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United Nations
Environment
Programme
World United States Army Corps of
Meteorological Engineers, Environmental Protection
Organization Agency, National Oceanic and
Atmospheric Administration
May 1990
Changing Climate and the Coast
Volume 2: Western Africa, the Americas,
the Mediterranean Basin, and the Rest of Europe
Report to the Intergovernmental Panel on Climate Change
from the Miami Conference on Adaptive Reponses
to Sea Level Rise and Other Impacts
of Global Clini*tte Change
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Library of Congress Cataloging-in-Publkation Data
Changing Climate and the Coast / edited by James G. Titus.
Papers presented at workshop held in Miami, Fla, Nov 27-Dec 1,1989,
sponsored by the US Environmental Protection Agency and others.
Contents: vol. 1. Adaptive responses and their economic, environ-
mental, and institutional implications—vol. 2. Western Africa, the Ameri-
cas, the Mediterranean basin, and the rest of Europe
Includes bibliographical references.
1. Global warming—Congresses. 2. Climatic Changes—Congresses.
3. Sea level—Congresses. I. Titus, James G. II. United States Environ-
mental Protection Agency.
QC981.8X356C5S1990 90-2741
333.91*7—dc20 CIP
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CHANGING CLIMATE AND THE COAST
VOLUME 2: WESTERN AFRICA, THE AMERICAS,
THE MEDITERRANEAN BASIN, AND THE REST OF EUROPE
REPORT OF THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE
FROM THE MIAMI CONFERENCE ON ADAPTIVE RESPONSES TO
SEA LEVEL RISE AND OTHER IMPACTS OF
GLOBAL CLIMATE CHANGE
Edited by
James G. Titus
U.S. Environmental Protection Agency
with the assistance of
Roberta Wedge
Norbert Psuty
Rutgers University
Jack Fancher
U.S. National Oceanic and Atmospheric Administration
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
The opinions expressed herein are solely those of the authors and unless noted otherwise do not necessarily
represent official views of any of the sponsoring agencies or the Intergovernmental Panel on Climate
Change.
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TABLE OF CONTENTS
Page
VOLUME 2
V. REGIONAL STUDIES
A. WEST AFRICA 1
Adjustments to the Impact of Sea Level Rise Along the West and
Central African Coasts 3
A.C. Ibe
The Gulf of Benin: Implications of Sea Level Rise for Togo and
Benin 13
Kolawole 5. Adam
Coastal Erosion and Management Along the Coast of Liberia 25
Eugene H. Shannon
Impact of Sea Level Rise on the Nigerian Coastal Zone 49
L.F. Awosika, A.C. Ibe, and M.A. Udo-Aka
Responses to the Impacts of Greenhouse-Induced Sea Level Rise on
Senegal 67
Isabelle Niang
Response to Expected Impact of Climate Change on the Lagoonal and
Marine Sectors of Cote D'lvoire 89
Philibert Koffi Koffi, Has sera Kaba, and Soko G. Zabi
Implications of Global Warming and Sea Level Rise for Ghana .... 93
J.F. Abban
Sociocultural Implications of Climate Change and Sea Level Rise in
the West and Central African Regions 103
0. Ojo
B. MEDITERRANEAN 113
Impacts of Global Climate Change in the Mediterranean Region:
Responses and Policy Options 115
6. Sestini
Impacts of Climate Change on the Socioeconomic Structure and
Activities in the Mediterranean Region 127
Ante Baric
iii
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Venice: An Anticipatory Experience of Problems Created by Sea Level
Rise . . 139
A. Sbavaglia, C. Clini, F. De Siervo, and G. Ferro
Implications of Sea Level Rise for Greece . 161
Hampik Maroukian
Impacts of Sea Level Rise on Turkey 183
Oguz Erol
The Influence of Sea Level Rise on the Natural and Cultural
Resources of the Ukrainian Coast 201
Yurii D. Shuisky
Coastal Morphology and Sea Level Rise Consequences in Tunisia ... 211
Ameur Oueslati
Responses to the Impacts of Greenhouse-Induced Sea Level Rise on
Egypt 225
M. El-Raey
Impacts of Sea Level Rise on Ports and Other Coastal Development in
Algeria 235
El-Hafid Tabet-Aoul
C. NORTH AND WEST EUROPE 239
The Vulnerability of European Coastal Lowlands Along the North Sea
and Atlantic Coasts to a Rise in Sea Level 241
Saskia Jelgersma
Impact of a Future Sea Level Rise in the Polish Baltic Coastal
Zone 247
Karol Rotnicki and Ryszard K. Borowka
Adaptive Options and Implications of Sea Level Rise in England and
Wales 265
Ian R. Whittle
Policy Analyses of Sea Level Rise in the Netherlands 283
J.G. De Ronde
Impacts of and Responses to Sea Level Rise in Portugal 293
Maria Eugenia S. De Albergaria Moreira
D. CENTRAL AND SOUTH AMERICA 309
Potential Impacts of Sea Level Rise on the Coast of Brazil ... 311
Dieter Nuehe and Claudio F. Neves
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Potential Impacts of Sea Level Rise on the Guiana Coast: Guyana,
Surinam, and French Guiana 341
J.R.K. Daniel
Impacts of Sea Level Rise on the Argentine Coast 363
Enrique J. Schnack, Jorge L. Fasano, Nestor U. Lanfredi
and Jorge L. Pousa
Regional Implications of Relative Sea Level Rise and Global Climate
Change Along the Marine Boundaries of Venezuela 385
Ruben Aparicio-Castro, Julian Castaneda, and
Martha Perdomo
Impacts of and Responses to Sea Level Rise in Chile 399
Belisario Andrade and Consuelo Castro
Living Strategies and Relocation in Latin America 421
Christina Massei
E. NORTH AMERICA 431
Responding to Global Warming Along the U.S. Coast 433
James G. Titus
Sea Level Rise: Canadian Concern and Strategies 457
K.B. Yuen
The Lowlands of the Mexican Gulf Coast 469
Mario Arturo Ortiz Perez, Carmen Valverde,
Norbert P. Psuty, and Luis M. Mitre
Raising Miami -- A Test of Political Will 487
Ted Miller and Mil Ham Hyman
Accommodating Sea Level Rise in Developing Water Resource
Projects 501
Robert H. Schroeder, Jr.
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WEST AFRICA
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ADJUSTMENTS TO THE IMPACT OF SEA LEVEL RISE ALONG
THE WEST AND CENTRAL AFRICAN COASTS
A. C. IBE
Coordinator, UNEP's Task on Implications of Expected
Climatic Changes on the Coastal and Marine Environment
of West and Central Africa
Nigerian Institute for Oceanography
and Marine Research
Victoria Island, P.M.B. 12729
Lagos, Nigeria
ABSTRACT
The coasts of West and Central Africa, stretching from Mauritania to
Namibia, are mostly low plain, sandy, surf beaten, and in many places, subsiding.
The region has population of about 269 million, of which a large percentage live
along or near the coasts. All but 4 of the 21 countries presently have their
capital cities on the coast. The lopsided history of urban development in the
region has meant that most economic and social infrastructures are located in
these cities. At present, erosion and concomitant flooding are prevalent along
the coasts and have assumed disturbing proportions, putting life and property
continually at risk.
These problems would be exacerbated by an accelerated rise in sea level
that would virtually cripple most economic structures and activities such as
ports, coastal roads, air fields, rail lines, fishing, farming, oil and mineral
production, manufacturing, etc. Settlements would be dislocated. Surface and
groundwater as well as flora and fauna of the region would be profoundly affected
as a result of increased salinization and added load of sediment and pollutants.
Increased incidence of heat-related diseases occurring with rising temperatures
would mean a drastic reduction in the well-being of humans, livestock, and crops.
The enormity of the various expected impacts dictates that significant measures
be taken to make the coastal zone habitable. Given the financial disabilities
of countries in the region, only well-planned anticipatory actions by these
countries, acting preferably in concert, can help avoid or minimize stress,
hazards, and resource losses from the expected changes.
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West Africa
INTRODUCTION
Recognizing that the impact of the expected accelerated rise in sea level
along most low-lying coastlines of the world would lead to a disruption of life
and dislocation of socioeconomic structures and activities in such places, the
Ocean and Coastal Areas Programme Activity Center (OCA/PAC) of the United Nations
Environment Programme (UNEP) set up Task Teams in 1987 to study the implications
of climate change on the coastal and marine environments of six of the regions
covered by UNEP's Regional Seas Programme, namely the Mediterranean, Caribbean,
South Pacific, Southeast Pacific, South Asian Seas, and East Asian Seas regions.
In 1989, two more Task Teams were assembled for West and Central Africa and
Eastern Africa. Other Task Teams (for the Black Sea and Kuwait region) are in
the process of being established. The ultimate objective of these Task Teams
is to advise governments in the various regions on how to respond appropriately
to the expected impacts of increased atmospheric temperatures and sea level rise.
The West and Central African Task Team convened for the first time in Lagos,
June 7-9, 1989. This paper combines the author's personal views on the problem
with those expressed by team members during that meeting.
SETTING
The West and Central African (WACAF) region, comprising 21 countries between
Mauritania and Namibia, stretches approximately for almost 7,000 km between
latitudes 23° N and 28° S (Figure 1) with a total area of 9 10s km2.
Climatically (and by implication, in terms of vegetation) the WACAF region
falls within three main zones (Figure 1):
1. North arid zone (semiarid and arid zones);
2. Equatorial humid zone (humid and subhumid zone); and
3. South arid zone (semiarid and arid zones).
GEOLOGICAL EVOLUTION AND GEONORPHOLOGY
The evolution of the continental margin of West and Central Africa is linked
with separation of South American from Africa. The dating of this separation
is inexact as it consisted of a series of overlapping events.
According to Emery et al. (1974), the earliest of the events in the region
was the development of small basins and troughs (the Liberia and Sierra Leone
Basins), when North America separated from Africa about 180 million years ago.
Then followed the separation of South America from Africa, which probably began
at the south and proceeded northward occupying a time span of about 165 million
to 135 million years. The general date of separation is indicated by the general
continuity of Precambrian and Paleozoic strata and structures in Africa and South
American and the disruption of Jurassic and younger structures. This separation
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Ibe
1. Mauritania
2. Cape Verde
3. Senegal
E 4. Gambia
* 5. Guinea Bissau
o 6. Guinea
z 7. Sierra Leone
8. Liberia
9. Cote d'lvoire
10. Ghana
11. Togo
•| 12. Benin
n 13. Nigeria
o-14. Cameroon
m 15. Equatorial Guinea
16. Sao Tome and Principe
17. Gabon
c 18. Congo
J2 19. Zaire
g 20. Angola
w 21. Namibia
Northern 7
Zone
Southern
Zone
Figure 1. Countries and zones of the WACAF region.
led to the formation of the basins farther south (the Mossamedes, Cuanza, Congo-
Cabinda, Gabon, Cameroun, Nigeria, Dahomey, and Ivory Coast Basins). Continued
separation of South America from Africa produced easily recognizable ocean-floor
provinces (see Emery et al., 1974 for details).
The coasts in the West and Central Africa region are mostly low plain,
sandy, and surf beaten. Four broad types are recognized: drowned coasts in the
northern area; sand bar or lagoon coasts along the north of the Gulf of Guinea;
deltas associated with most of the major rivers (e.g., Niger Delta) usually with
mangrove swamps and marshes; and coasts with sand spits (and tombolos) formed
by accumulation of longshore transported sand in bays found in the southern
parts of Angola.
From the point of view of their geological evolution and present
geomorphology, the coasts in the region are clearly vulnerable to sea level rise,
not only because they are low-lying but also because the sedimentary basins that
dominate the coasts are areas of subsidence. These basins, formed by the rapid
deposition of sediments in a tectonic setting, are even in present times, still
undergoing dewatering and compaction. In recent times, human intervention by
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Vest Africa
fluid extraction (including oil and gas) in the coastal zone has had the effect
of accelerating the subsidence due to natural causes.
SOCIOECONOMIC SETTING
Settlement and Population
The WACAF region has a population of about 269 million and with a rapid
annual growth rate of about 2.9%, the population will most probably double itself
within the next two and a half decades.
Due to the history of early contracts with Europeans, most important cities
in the region are located on the coast. Of the 21 countries, only 4 do not have
their capital cities in the coastal area. These coastal cities are nearly always
synonymous with centers of commerce, industry, and politics and have thus
attracted very large populations. For example, Lagos (Nigeria) is reputed to
have a population of over 8 million out of an estimated national population of
100 million. The story is much the same for Dakar, Abidjan, Freetown, Banjul,
etc.
Communication
Ports and harbors as transportation access facilities for maritime
activities provide the lifeline for socioeconomic development of the region and
are all located in the coastal zone. Most of these ports and harbors are linked
by intricate road, rail, and air transport routes that complete the network for
the export-import trade that is the linchpin of most economies in the region.
Coastal roads, some of which are presently under threat from marine erosion,
provide particularly easy access between the countries in the region, while air
transport offers a means of rapid movement of goods and peoples between the
countries.
Industries
When compared with Europe or America, the West and Central African region
is poorly industrialized, but the pertinent issue is that the industries that
do exist are concentrated mainly on or near the coast, most often around the
capital cities. Such industries include mining, oil and gas, petroleum products,
textiles, paper and pulp, timber, brewing, Pharmaceuticals, plastics, leather,
lumbering, and various manufacturing outfits.
Agriculture
Agriculture is the most important industry in the West and Central African
zone. About 70 to 80% of the population is engaged in agriculture, and the
economies of most countries in the region depend on it. The coastal areas are
becoming increasingly important to this industry and have the potential of
increasing substantially their contribution to agricultural production. About
60 to 80% of the food production of this zone comes from small farms.
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Ibe
The crops and produce from agriculture of this zone may be classified as
follows (UNEP, 1984):
1. Tree and horticultural crops (oil palm, coconut, citrus, avocado, pear,
rubber, kolanuts, sheanut, cocoa, coffee, pawpaw, banana, plantain,
mango, pineapple);
2. Cereals (maize, rice, sorghum, millet);
3. Root crops (cassava, cocoyam, yam, sweet potato, ginger, tigernut);
4. Vegetables and beans (groundnuts, cowpea, phaseolus bean, melons); and
5. Other crops (sugarcane, tobacco, and cotton).
Apart from crops, the coastal and forest areas have a low livestock
population. The main categories of livestock are large ruminants (cattle and
camels), small ruminants (sheep and goats), equines (asses, mules, and horses),
pigs, and chicken. The distribution of livestock is uneven. It is governed by
natural factors such as the presence of tse-tse fly and historical and cultural
factors as well as vegetation types.
Mariculture and aquaculture are becoming increasingly popular in the coastal
zone of the West and Central African region. Captive breeding of economically
important species such as Chrvsicthy spp., Megalops spp., Clarias lazera, as well
as oyster culture, are widely practiced in Nigeria and Ghana with varying degrees
of success. In Angola, the culture of mussels, Perna perna, is popular.
NATURAL RESOURCES
Forestry and Wildlife
The West and Central Africa region is the home of the tropical rain forest
and mangroves of great biological diversity, but the density and variation of
the forests are greatly influenced by climate, especially rainfall. The rain
forests and mangroves form the basis of an extensive lumbering industry.
The region is rich in wildlife, which is an important source of protein
and are hunted intensively, but several species are on the endangered list as
a result of uncontrolled harvesting and poor management. The most important
wildlife include elephants, lions, buffalos, hartebeests, smaller antelopes of
different kinds, warthogs, aardvarks, civet, cats, chimpanzees, baboons, birds
of all types, and reptiles.
The animal species found in the mangroves are also found in other brackish
water, salted waters, and nearby forests. The fauna consist of invertebrates,
molluscs, crabs, prawns, and fish, reptiles, birds (e.g., herons, storks, and
ibises), reptiles, and mammals (monkeys, bush pigs, and manatees). Most of the
reptiles, birds, and mammals are semi-aquatic.
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West Africa
In addition, the mangroves provide important spawning and breeding grounds
for a variety of finfish and shellfish that are the targets of artisanal and
industrial fishery in the coastal zone.
Fisheries
Despite deficient statistics, several resource surveys in the different
countries of the region show that respectable quantities of fish are harvested
in the region. According to UNEP (1984), production figures show high harvests
in Angola, Cameroon, Ghana, Ivory Coast, Nigeria, Namibia, Senegal, Sierra Leone,
and Zaire. Namibia, with 761,000 metric tons in 1978, has the highest figures.
The existence of upwelling zones in the region (both permanent and seasonal)
is known to be the basis of the rich fishery of the region. Major permanent
upwelling zones occur near Mauritania and Senegal as well as off the Congo,
Angola, and Namibia, whereas seasonal upwelling occurs in the Gulf of Guinea
between Cote d'lvoire and Nigeria. The lagoons, creeks, and bays along the
coasts are also areas of high productivity.
Fish and shrimp are the major resources of the region, although in some
countries such as Senegal, Sierra Leone, Nigeria, and others, edible molluscs
from near-shore areas are harvested in considerable quantity. The shrimps,
prawns, and oysters are now the targets of export trade in the region.
Minerals (Including 011 and Gas)
A variety of minerals ranging from commonplace sand and gravel to gold,
diamonds, and petroleum are mined from the coastal zone of this region.
According to UNEP (1984), the extent of mined resources, particularly if revenues
from petroleum products are considered as part of this grouping, is significant
in countries such as Nigeria, Gabon, Liberia, Guinea, Angola, and Sierra Leone;
their economies are best described as mineral economies. For example, the export
of petroleum accounts for over 90% of the export and foreign exchange earnings
of Nigeria. Except for Gabon and Nigeria, nonfuel minerals still dominate the
economies of the other countries listed above.
Water Resources
The West and Central African region is well-endowed in terms of rivers.
It is also blessed with heavy precipitation (reaching 2,000 mm in the south),
which means that the recharge potential of groundwater aquifers is very high.
Water balance maps depict areas of high rainfall, high humidity, and low
temperature, i.e., Liberia, Sierra Leone, and southeastern Nigeria, which have
the greatest water surplus (amounting to the equivalent of more than 1,000 mm
of rainfall). In the more arid conditions of the north, however, rainfall
decreases to 50 mm and, under such circumstances, aquifer recharge is very low.
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PRESENT CLIMATE EFFECTS
The West and Central African coasts are the scenes of high wave intensity.
This fact, along with other adverse geological conditions (e.g., erodibility of
sediments, subsidence), and detrimental human interference in the natural
environment, have meant that erosion and concomitant flooding are prevalent along
the coasts of the region (Ibe and Quelennec, 1989). In some places, the flood
rates are so rapid that whole towns (e.g., Grand Popo in the Benin Republic and
Keta in Ghana) have virtually disappeared. Elsewhere, life and property have
been put to risk with resultant economic losses and social misery.
The region in recent times has witnessed a prolonged scourge of drought
and desertification with all its attendant dislocation of population and
destabilization of socioeconomic activities. Hunger and disease have afflicted
the populace as a result of crop failures and losses in livestock.
PREDICTED CLIMATE CHANGES
Different scenarios of climate change have been put forward and defended
by various authors, but the Task Team adopted as the basis for its deliberations
the assumptions accepted at the UNEP/ICSU/WMO International Conference in
Villach, October 9-15, 1985, i.e., increased temperature of 1.5-4.5°C and sea
level rise of 20-140 cm before the end of the 21st century. (For the purpose
of the meeting, temperature elevation of 1.5° and sea level rise of 20 cm by the
year 2025 were accepted with the understanding that these estimates may have to
be revised on the basis of new scientific evidence.)
IMPACTS FROM EXPECTED CLIMATIC CHANGES
The problems of erosion and flooding presently experienced along the coasts
of the region will be exacerbated by the predicted acceleration in global sea
level rise. In fact, worldwide evidence points to erratic jumps in the rates
of shoreline retreat that suggest sea level rise as a contributory factor (Pilkey
et al., 1981). Although the accepted predicted values may seem small, its impact
along the low-lying and, in many cases, subsiding coasts in the region would be
immense, particularly when viewed from point of view of the Bruun (1962) rule,
which predicts that a rise of 0.3 m (1 ft) of sea level will cause a shoreline
recession of more than 30 m (100 ft) on low-lying coasts. Subsidence phenomenon,
known to be active in major coastal sedimentary basins in the region, would
aggravate the situation.
With the increase in ocean temperature, tropical storms are likely to extend
into some humid areas, and with rising sea level, the periodic flooding presently
being experienced in vast coastal areas will become more frequent and
devastating. This will virtually cripple most economic structures and activities
in the densely populated and highly urbanized settlements proximal to the sea.
Ports, coastal roads, and rail lines will be knocked out of action; fishing,
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West Africa
farming, oil and mineral production, and manufacturing will be interrupted;
people and businesses will be forced to relocate, etc.
As a result of increased sea level rise, surface drinking water and
groundwater aquifers would be rendered unusable as sources of potable and
irrigation water because of increased salinization and added loads of sediment
and pollutants.
The fragile ecosystems of the coastal zone will be adversely affected by
inundation from the sea and may not be able to perform their traditional roles
as the spawning and breeding grounds of most finfish and shell fish that are the
targets of artisanal and inshore industrial fishermen.
A rise in sea level will also profoundly affect the flora and fauna of the
region as well as the agriculture and livestock production. Vegetation kill due
to salinity stress would result, as is presently being witnessed in the Mahin
area on the northwestern flank of the Niger Delta (Ibe, 1988a,b). The
distribution and composition of the coastal vegetation would be affected with
salt-loving species increasing. This may decrease suitable forage for livestock,
resulting in a depression of this occupation among coastal populations. The
areas of saline soils would increase, making them unsuitable for cultivation of
crops like maize, banana, pineapple, etc. Coastal plantations would also suffer
from salinization. Hunger, already a problem in the region, would worsen.
Apart from the impacts due to sea level rise, other impacts derived from
a rise in temperature would result. Increased humidity and temperature would
favor rapid multiplication of insects such as mosquitoes and the tse-tse fly,
resulting in diseases such as malaria and trypanosomiasis reaching epidemic
proportions. Temperature-sensitive plant diseases and weeds would also increase
and cause greater damage to crops. Increased incidence of heat-related diseases
with rising temperatures would mean a reduction in the well-being of humans and
livestock. The general level of discomfort and misery would be high.
ADJUSTMENTS TO IMPACT OF SEA LEVEL RISE AND OTHER EFFECTS DUE TO CLIMATE CHANGES
It is imperative that countries in the region make some adjustments to cope
with the adverse conditions that would accompany the rise in sea level and higher
atmospheric temperatures. Given the financial disabilities of countries in the
region in the face of these serious threats, well-planned anticipatory and, in
some cases, reactive (including adaptive) actions need to be pursued by the
countries acting individually or in concert to avoid or minimize the stress;
hazards and resource losses would be likely to occur with the expected changes.
In relation to sea level rise, there will be a need to protect heavily
built-up areas having high-value installations where the option of relocation
is not a reasonable economic proposition. But while many of the engineering
countermeasures are feasible for shoreline protection in the face of sea level
rise, they are economically impractical in view of the financial position of most
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Ibe
countries in the region. The approach here should be toward the adoption of
low-cost, low-technology, but effective measures such as permeable nonconcrete
floating breakwaters, artificial raising of beach elevations, installation of
rip raps, timber groins, etc., from locally available materials. Fortunately,
outside the urbanized centers, the coasts are almost in pristine condition and
largely uninhabited except perhaps for small fishing settlements which, in any
case, are highly mobile. In such situations, resettlement of existing
populations and the enforcement of set-back lines for any new developments on
the coast should be applied. Where coasts are deemed highly vulnerable, total
ban of new development is necessary.
Designs of new buildings and other facilities should take into account the
predicted and continuing rise in sea level as well as increased heat. For
instance, houses should be concerned with increased use of natural ventilation
modes. Afforestation of coastal lands would provide some measure of damping of
wave energy as well as relief from increased heat.
Other adjustments would involve the protection of arable land, improved
management of water resources, introduction of new agrotechnology to cope with
new realities, controlled land use policies, maintenance of food reserves, and
the introduction of emergency disaster relief measures.
For protecting arable lands, some of the low-cost, low-technology measures
mentioned above would be applicable. Improved water management techniques would
involve the building of dams (after environmental impact assessment), aqueducts,
reservoirs, irrigation systems, and river diversions with the objective of
husbanding water in times of drought. The adoption of new agrotechnology should
aim at introducing more salt- and heat-tolerant crops, developing adaptive
irrigation systems aimed at reducing salinity stress, and so on. Although the
region is far from being self-sufficient in its food needs at present, there will
be a need to stockpile food and institutionalize other disaster relief measures
to cope with emergencies that may arise from sudden flooding or drought.
Other adjustments would require the setting up of environmental monitoring
and early warning systems, providing flood vulnerability and land use maps for
coastal areas, and perhaps above all, providing public information and education.
This calls for extensive information-gathering, analysis, and utilization.
Public information and education would drive home to the populace the seriousness
of the anticipated impacts from increased atmospheric temperatures and sea level
rise and thus better prepare them for the implementation of certain protective,
preventive, or adaptive measures that would necessarily have to be put in place.
CONCLUSION
Higher atmospheric temperatures and increased sea level rise are realities
that humanity has to cope with now and in the future. Even if all suggested
measures to stop the introduction of greenhouse gases were put in place now, the
world would still experience many of the anticipated impacts due to "sins of
omission or commission" already committed by man toward global warming.
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West Africa
The application of most of the protective, preventive, or adaptive measures
suggested above will be imperative but it is important that proposals for
adjustments to the expected impacts be embodied in a coordinated and enforceable
regional development plan. UNEP's Regional Seas Programme for the West and
Central African region affords a vantage platform for discussing and
institutionalizing such a plan. It is hoped that governments in the region,
while pursuing policy options at the national level, would now appreciate, even
more than ever before, the distinct advantages for a regional approach to the
problems associated with global warming.
ACKNOWLEDGMENTS
The author acknowledges the help of Profs. 0. Ojo, I. Findlay and A. Asare,
and Drs. T. 0. Ajayi, S. Zabi, I. Sy-Niang, S. Ogbuagu, T. Egunjobi, L. Awosika,
M. Akle, and G. Nai who are members of the WACAF Task Team. Miss S. A. Fakan
typed the manuscript.
BIBLIOGRAPHY
Bruun, P. 1962. Sea level rise as a cause of shoreline erosion. Am. Soc. Civil
Eng., Proc. V.88 Waterways and Harbours Div. Journ. WW1:117-130.
Emery, K.O., E. Uchupi, J. Phillips, C. Bowin, and J. Mascle. 1974. The
Continental Margin of Western Africa: Angola to Sierra Leone. Contribution No.
3481. Woods Hole, MA: Woods Hole Oceanographic Institution.
Ibe, A.C. 1988a. The Niger Delta and the global rise in sea level. In:
Proceeding of the SCOPE Workshop on Sea Level Rise and Subsiding Coastal Areas,
Bangkok, Thailand, November 7-14, 1988. Pergamon Press.
Ibe, A.C. 1988b. Coastline Erosion in Nigeria. Ibadan, Nigeria: Ibadan
University Press, 217 p.
Ibe, A.C., and R.E. Quelennec. 1989. Methodology for assessment and control
of Coastal Erosion in the West and Central African Region. UNEP Regional Seas
and Reports and Studies No. 107. Geneva: United Nations Environment Programme,
112 p.
Pilkey, O.H., et al. 1981. Old solutions fail to solve beach problem. Geotimes
26:18-22.
UNEP. 1984. Environmental management problems in resource utilization and
survey of resources in the West and Central African Region UNEP Regional Reports
and Studies No. 30. Geneva: United Nations Environment Programme, 83 p.
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THE GULF OF BENIN: IMPLICATIONS OF SEA LEVEL RISE
FOR TOGO AND BENIN
KOLAWOLE S. ADAM
Universite Nationale du Benin
Cotonou, Benin
INTRODUCTION
The coastline of West Africa in general, and the Gulf of Benin in
particular, has witnessed sea level variations of great dimensions in the past.
The present configuration of the coast is the product of the oscillation of sea
level that took place 20,000 years ago. Short-term as well as seasonal oceanic
fluctuations (tides, waves, storm waves) linked to atmospheric disturbances are
sometimes spectacular on the West African coasts, but the greatest dangers are
long-term changes that could result from a change in the world's climate. Global
warming is probably the cause of the rise in sea level that we have been
witnessing since the beginning of the 20th century.
Accelerated sea level rise -- which is already 2 cm per year along some
coasts -- will bring about important natural, socioeconomic, and cultural
disruptions in the coastal"plain of the Gulf of Benin. The coastal areas are the
most densely populated and contain the economic heart of both Benin and Togo,
including the main towns, the port and airport infrastructure, and the majority
of the countries' industries.
The coast of the Gulf of Benin is a low and even coastal plain stretching
nearly 500 km from the Cape of the Three Headlands (Takoradi Region in Ghana) to
the Delta of Niger (Nigeria). This paper focuses on the approximately 175 km
that constitute the coastal zone of Benin and Togo, examining (1) the possible
effects of future sea level rise on the coastal ecosystems such as deltas,
estuaries, lagoons, mangroves, and human activities of the coastal plain; (2)
the reactions of the different research institutes and decision-makers in the
face of these impacts; and (3) the present characteristics of the coastal
environment.
IMPACTS OF ACCELERATED SEA LEVEL RISE
Rising sea level is always accompanied by inundation and erosion. The Gulf
of Benin coast will be very sensitive and catastrophes may result if appropriate
13
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West Africa
precautions are not taken in time. We discuss the effects and damages of three
possible scenarios:
Sea Level Rise of 50 cm
As Figure 1 shows, the shore could retreat considerably, particularly
between Anecho and Grand-Popo. A retreat of about 100 meters may be foreseen,
which will be a big blow to the Cotonou-Lome interstate road, which would be
dangerously threatened and would have to be moved inland. Nearly half the
beaches and coconut-tree plantations would disappear in this region, although
some of the agriculture would not suffer serious damage. We can be certain that
Grand-Popo and Agoue graveyards would be periodically washed by the waves.
If urbanization is checked, particularly in the east of Cotonou, the risks
would be less, but there is little hope that this will happen. The swampy areas
would increase considerably, especially in the estuary of the Mono River, which
would bring about a loss of nearly 25% of the existing upland, especially in the
city of Cotonou where the situation is already highly critical. The ecological
imbalance caused by the oversalinization of the coastal lagoons would surely be
disturbed; the degradation of the mangroves which was already persistent will be
aggravated.
Protective measures would continue to aggravate the problems downstream, but
they can protect the very sensitive strategic places on the coast. However, the
protection would be short-lived and would lead to other management problems.
Sea Level Rise of 100 cm
All the damages from the previous scenario would be aggravated. The retreat
of the shoreline would provoke the displacement of all hamlets built on the crest
of recently formed barrier islands. Two-thirds of the town of Cotonou would be
submerged and the town would be depopulated since there is no possibility of
extension; by contrast, the town of Lome could be stretched farther north on the
plateau. The towns of Grand Popo, Agoue, Aneho and Kpeme would be seriously
threatened and may disappear. A high salinization of the coastal plain would
render life conditions more precarious. Protective measures would not be
feasible, and people would instead think of controlling the migration toward the
plateau.
Sea Level Rise of 200 cm
Because their elevations are only 3 m, all recently formed barrier islands
will come close to complete submergence; the portions not inundated will almost
surely erode (cf. Figure 2). Only a few small "islets" of lesser importance
will remain. All human settlements of the coastal plain wwould disappear. Only
the part of the town of Lome on the plateau would be able to resist destruction.
The Lome-Cotonou-Lagos interstate road would be partly submerged. The settlement
patterns in this part of the world would have to be reconsidered. In any case,
if this rise of the sea level persisted, people would surely not wait before
considering relocation toward the plateau and new modes of life.
14
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Figure 1. Areas vulnerable to a 50 to 100 cm rise in sea level.
Figure 2. Land loss from a 2-meter rise in sea level.
-------
West Africa
POSSIBLE RESPONSES TO SEA LEVEL RISE
There are two solutions to safeguard the coastal zones of Togo and Benin
along the Gulf of Benin: (1) coastal defense and the artificial nourishment of
the beaches; and (2) respect for the littoral dynamics which requires avoiding,
as much as possible, development that sets up an unavoidable confrontation
between humanity and the sea.
The evolution of research in the region appears to support a gradual shift
from the former to the latter approach. Still, most proposals for addressing
erosion are short-term and do not consider sea level rise. The overall theme of
most proposals is a natural protection of the littoral zone by using beach rock.
But the characteristics of the Gulf of Benin coast suggest that the effectiveness
of this natural protection would be limited, particularly if sea level rise
accelerates.
In both Togo and Benin, survey offices and university Applied Research
Laboratories are responsible for management of this coast. The labs are studying
the possibilities of safeguarding nature according to its evolution from the
field and the laboratory's research. The survey offices are studying the
cheapest methods of protecting certain elements of the environment by fighting
against some natural forces.
Given the prohibitive costs of some solutions and the lack of resources in
these difficult times, the majority favor measures that control the littoral
dynamics. The authority of the researchers is limited because it is the
decisionmakers who have the final word. Sometimes, they neglect the advice of
the nationals and turn to proposals made by foreign survey offices. But policies
are changing. Public opinion is obliging decisionmakers to enter into dialogue
with researchers, planners, and town developers. Nowadays, few people perceive
the rise of the sea level as an important factor in the management of the coastal
zone. But over time, the various scientific and policy reports on the subject
will probably be able to convey the importance of such a phenomenon.
THE COASTAL ENVIRONMENT OF BENIN AND TOGO
On the coasts of the Gulf of Benin, the tide is semidiurnal, with two highs
and two lows of nearly equal amplitudes that succeed each other at regular
intervals. The spring and neap tidal ranges are 1.6 and 0.6 meters,
respectively.
Along the shores of Benin and Togo is a coastal strip whose width increases
from the west (2 km in Lome) to the east (10 km at the Benin-Nigerian border).
It is a contact zone between many old and new barrier islands, lagoons, and
swamps that separate the coastal features from the inland slopes (yellow and
claylike sands). This body is limited in the north by a scarp of the red-clayed
plateau. There are numerous barrier islands with elevations of 3 to 5 meters.
16
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Adam
Table 1. Evolution of the Coast
SECTORS
ESTUAIRE VOLTA-KETA
ZONE W KETA
KETA VILLE-AFLAO
W PORT - LOME
EST PORT - LOME
TROPICANA
TROPIC ANA- KPOGAN
KPOGAN - AGBODRAFO
AGBODRAFO— GUMUKOPE
GUMUKOPE - ANEHO
ANEHO - HILL A- KONDJI
HILL A -KONDJI -GRAND POPO
GRAND POPO VILLE
GRAND POPO - OUIDAH
OUIDAH - AEROPORT- COTONOU
W- PORT -COTONOU
PORT-P.L.M.
P. L. M. —SO BE PRIM
SO BE PRIM — KLAKE
1959-64
*
+
-
*
*
*
*
*
*
*
*
*
*
*
K
*
*
X
*
1964-69
-
+
-
JX^
Jt^-^^
*--"''"
*
*
*•
J^T
#
*
*
*
*
+
+
—
*
1969-75
-
+
—
+
-
-
—
*
*
j^r
*
*
-
«
*
+
>^r
—
M
1975-81
-
+
-
+
^^"*
-
—
—
—
-
J^T
*^^
-
*
*
+
J^<
-
*
1981-84
-
+
—
+
*
—
—
-
—
-
^^
J^s^
+
K
*
*^x"
J>^
-
*
1984- 89
-
+
—
+
*
*
—
-
—
-
J^<
^^
4-
*
*
*
*
-
*
FATTENING
EROSION
STABILITY
APPARITION OF THE BEACH - ROCK
EFFICIENT BEACH - ROCK
17
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r
West Africa
The evolution of the coast has been schematized in Table 1. The offshore
barrier islands are mainly occupied by a well-planned planting of coconut trees
complemented in the east by the planting of eucalyptus and filao. Mangroves are
mainly found along the coastal lagoons, with the western boundary schematized by
an Aneho-Glidji line.
HUMAN ACTIVITIES ALONG THE GULF OF BENIN
Since the 16th century, the littoral of the Gulf of Benin, just like the
whole of the West African coast, has been the center of many human migrations and
the magnet for intense agricultural and commercial activities.
Demography
Although the distribution of the population is uneven, the density of the
rural population in the coastal plain of the Gulf of Benin is more than 200
inhabitants per square kilometer. The urban and demographic dynamism is marked
by industrial and related activities in Cotonou and Lome. The combined
population of the major cities (Lome, Aneho, Grand-Popo, Ouidah, Cotonou, and
Seme) is estimated at about 1.5 million inhabitants; the population of the entire
coastal plain is about 2 million, about 25% of the total population of both
countries. The urban dynamism of Cotonou is of concern, as it is a town in full
demographic explosion (600,000 persons) where the only open space for expansion
is on barrier islands stretching east of the town where erosion is already very
serious.
Economic Activities
The coastal region is the economic hub of both countries, for it harbors the
main towns, the ports, and airports, and, above all, a number of important
industries. The role of the port activities in the present economic development
of those countries is unquestioned (despite the scarcity of comparative data to
demonstrate its importance). Lome and Cotonou ports play an important role in
the import and export trading of landlocked countries of West Africa (Mali,
Burkina Faso, and Niger). The steady growth in the port activities, which was
more than 500% from 1968 to 1978, even recorded a sudden increase between 1977
and 1980 because of the onset of certain activities (oil refinery in Lome and the
role played by Nigerian imports during the time of the oil boom, when Lagos Port
was "congested").
Agriculture
Agriculture in this region is a function of the climatic and pedologic
conditions, which are not very good. The bars are mainly occupied by well-
arranged plantations of coconut trees. Near the coastal lagoons, some grain
foodcrops are grown (maize, cassava, cowpeas) as well as vegetables.
18
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Adam
Fishing
Just like the Lebou in Senegal, the Akan in Cote d'lvoire and in Ghana, the
Peda and the Pla peoples from Ghana have moved into the coastal strip of the Gulf
of Benin, practicing a flourishing fishing economy which nurtured the big trade
with the people of the interior. It was mainly the lagoons that attracted the
Peda, even though Lake Nokoue and Porto-Novo lagoon are largely exploited by the
Tofinu. In general, fishing is a traditional activity (small day-trip fishing)
that provides freshwater species (tilapia and Crustacea).
Since 1960, with the construction of Lome and Cotonou ports, offshore
fishing has developed with the massive arrival of Ghanaians (Fanti and Keta) who
introduced gear boats in this business that became semi-industrial. The economic
position of fishing in the region is in an average position (66th) in the world,
near the Cote d'lvoire and far behind Nigeria (28th), Senegal (33rd) and Ghana
(34th).
Today, offshore fishing is the most important activity practiced by
fishermen living at the coast; it provides a considerable quantity of fish (about
50 million tons/year for both countries) to a large part of the population of the
capital cities and the coastal towns.
Many of the fish caught in the region depend upon coastal wetlands.
Accordingly, the loss of those areas to rising sea level could severely hurt
fishing. The ability of the shallow water bodies that replace the wetlands to
support fisheries is unknown.
Modifications of the Shore
The demands of the national economy have called for the construction of two
deepwater ports in Lome and Cotonou. The protecting jetties of these ports are
large and they have accelerated the process of coastal erosion already started
by the construction of Akossombo Dam. More recently, the construction of many
piers for the protection of some strategic zone (Kpeme factory, Aneho town, P.
L. M. Hotel, Hotel da Silva) and the hydroelectric developments on the Mono River
(Nangbeto Dam) have added to the sedimentary and ecological inbalance of the
coastal zone (see Table 1).
Coastal Management
The general consumption of space all along the Gulf of Benin by hotels and
various structures and equipment aiming at the tourist trade is presently a
fundamental concern of planners and developers. In light of today's disorderly
management, avoiding irreversible choices will require a new policy for the
coastal zone. For the past 10 years, a planned development scheme has been under
consideration which, taking into account the present land uses, can be summarized
as follows:
19
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West Africa
to limit the coastwise boundary of the urbanization zones and main
development;
to define the mode of stabilization of the coasts; and
to plan the zones for recreation and tourism exclusively equipped with
mobile facilities..
Up to now, no government decree has considered such ideas; so, for the time
being, they remain purely and simply academic reflections.
CONCLUSION
The fragility of the coasts in general and of those of West Africa in
particular is of great concern. To try to best preserve this littoral, it is
necessary to understand its dynamics better. Sea level rise is an inescapable
parameter to reckon with in any approach to the management of the littoral. A
systematic inventory of all useful information sources is a foremost task (e.g.,
topographic maps, general maps, inventory maps, aerial photographs, satellite
pictures, oceanographic data, population density maps, historical documents).
Certain approaches such as satellite teledetection are indispensable tools today
to better understand certain phenomena (e.g., waves, salinity, currents, water
temperatures, biological processes of estuaries). All of these elements are the
basis for understanding and efficiently managing the coastal heritage.
20
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Adam
APPENDIX
THE GENERAL CHARACTERISTICS OF THE LITTORAL OF THE GULF OF BENIN
THE NATURAL SETTING
The Coastal Climate
The climate of the Gulf of Benin is of a beninian type (subequatorial) with
two rainy seasons (mid-March/July and September/November) and two dry seasons.
The average rainfall is 1,200 mm per year decreasing toward the west (1,400 mm
per year in Seme and 850 mm per year in Lome); this decrease is due to the
configuration of the coast in relation to the marine winds. The temperature is
constantly high (yearly average is 27°C) with the average maximum in March (33°C)
and the average minimum in August (25°C) when temperature can go down to 22.5°C.
The months of January, February, and March record high thermal amplitudes (12°C).
These variations are reduced during the rainy season.
The predominant direction of the wind is southwest with average speeds of
4 to 6 m/s (3 Beaufort). The winds from the south-southeast sector are not
frequent and they blow in April and May. Because of the relatively even relief,
the pattern of winds does not vary much according to seasons. In dry season, the
wind strength is weak to moderate (2 to 5 m/s) in the morning. It is stronger
during the day (5 to 7 m/s) and becomes moderate in the evening and in the night
(4 to 6 m/s). During the rainy season, a moderate wind blows (4 to 6 m/s) in the
morning which becomes stronger in the afternoon (6 to 8 m/s) and remains
constantly moderate to strong (5 to 8 m/s) in the evening and at night. The peak
speeds are reached during the passage of rain lines (east to west direction) with
average speed of 15 m/s, accompanied by harsh winds and rainstorms.
Swells and Waves
Along the Gulf of Benin, one observes a long swell of a distant origin, the
wavelength of which can vary between 160 and 220 m. This swell unfurls over the
bar at a distance of about 150 to 200 m from the shore (characteristics at the
Cotonou wharf). There are also waves due to local winds whose characteristics
are changing but have little importance for the morphological phenomena of the
coast. Their wavelength is about 50 m. The swell whose primary period is 12
seconds (even though it can sometimes vary between 10 and 16 seconds) has a
relatively regular average height between 1.0 and 2.0 m.
Table 1 gives the average amplitude of swell in Cotonou. Using the averages
observed in Lome in 1955 and 1961, it is noted that swells are stronger in
Cotonou than in Lome by 28% in 1955 and 11% in 1961. This difference is due,
according to Sitarz (1963), to the protection offered by Cape St. Paul (Ghana)
to Lome port area.
These swells generally travel from southwest to northeast (1980). The most
recent surveys give the following distribution:
21
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Vest Africa
SE - S 135° to 180° = 10%
S - SW 180° to 203° = 36%
S - SSW 203° to 225° = 54%
The breaker line in the region of Cotonou occurs at a depth of 3 m, or at
about 150 to 200 m from the shore: This is the locus of important sedimentary
movements.
The Coastal Geomorphology
The geomorphological evolution has mainly resulted from the fluctuations of
the marine level during the Quaternary, and secondly by the local tectonics
(faults of Togbin, of Godomey and Krake determined by J. Land and G. Paradis,
1977). Since 5,000 years ago the series of barrier features have regularized a
coastline that was indented with deep rias during the Flandrian transgressive
maximum. These are essentially sandy bars; granulometric and microscopic
analyses confirm the marine origin of these sands.
One can subdivide this shore into three sections with varying
characteristics:
Lome to Grand-Popo
A narrow coast (average width = 1 km and narrows towards the east) with
altitudes of between 3 and 5 m. Three types of profiles can be distinguished
according to hydrodynamic parameters:
• Profile with straight crest, steep seaward slope, short foreshore (less
than 3 m), upper berm at 1 m, even surfaced slope: profile resulting
from strong swells.
• Profile of very strong swells: profile with round crest, with basal
berm on its seaward slope. The inlandside of the barrier is steeply
sloped toward the lagoon.
• The beach profile with straight or rounded crest characterizes the
transition between a strong swell and an average one.
Grand-Popo to Godomev
The altitudes of the barriers in this section also vary between 3 and 5 m,
and they are modified on the inland margin by the lower course and the mouth of
River Mono, the coastal lagoons, and the swamps. The width of the bars is quite
narrow (less than 200 m). We see the same types of profiles as in the previous
case.
Godomev to Krake
The bars break up into a multitude of successive parabolic crests which are
rigorously parallel, of west-east orientation, and of a maximum altitude of 6 m.
22
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Adam
The granulometric (medium and fine sands) and morphoscopic (blunted and shining
sands) measures are in favor of a marine origin. These fine sands, generally
well sorted, have been deposited under homogeneous hydrodynamic conditions even
though some local disturbances can be noticed.
Close analysis of sediments along the littoral of the Gulf of Benin shows
fine to coarse sands (median diameters between 0.4 and 1 mm) at the foreshore,
up to 4 m; from 4 m to 16 m elevation, the sediments are very fine and well
sorted. Despite the homogeneity in the distribution of sediments from the west
to the east of the gulf, there is a strong variation to the east of the mouth of
River Mono; these sediments have medium diameters from 3 to 6 mm in the depths
of -12 m, and they are composed of coarse sands mixed with gravel.
The geomorphological cartography carried out with the collaboration of
researchers of both universities (Adam, 1986) has made it possible to demonstrate
the complexity of the evolution of this coastal strip. One element is durable
formation, beachrock, evidence of an old beach consolidated by a carbonate
cement. This formation is made of overlying slabs whose thickness varies between
0.5 and 1.5 m and whose width varies between 25 and 50 m. Its position in the
littoral profile (sometimes reaching + 3 m altitude) and its mechanical
resistance causes beachrock to be a natural protection against coastal erosion.
It presently plays a role of wave-breaker, eliminating the actions of the swell
in the coast of the eastern part of Lome. This formation exists all along the
coast at different altitudes. Its role seems to be efficient under the present
hydrological conditions prevailing between Lome and Kperme, between Ouidah and
Cotonou, and to the east of Seme. Its efficiency is null elsewhere. Today, the
distribution of beachrock is to be considered in any survey aiming at evaluating
the littoral of the Gulf of Benin.
Inlets
Three hydrological systems present themselves from the west to the east:
• The system of Lake Togo: Lake Togo gathers the waters from the Zio and
Haho Rivers before flowing into the ocean through the lagoon mouth of
Aneho. This mouth has a strange evolution; having been long closed by
a spit of barely 30 meters, it discharges water collected from brooks
into the Mono River through the latter's effluent, the Gbaga. When the
water rises, the whole area is flooded and since 1987, with the
construction of jetties at Aneho, an opening has been made at Aneho
which serves as a permanent mouth for this system of Lake Togo.
• The estuary of Mono is a hydrological complex characterized by the
courses of the Mono and Koufo Rivers and the tidal flows. The dynamic
behavior of this sector is linked with the variations of the tides and
of the flow of the river. During flood time, the flow is enough to push
back the saltwater zone beyond the shoreline. Inversely, when the
freshwater flow is at a low level, the saltwater contact goes up to
Agome-Seva (40 km). This part of the valley (6 m IGN) and Lake Athieme
are completely under the influence of the tide.
23
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West Africa
• The Delta of Oueme is the most important hydrological element of this
area. It is characterized by the regime of the Oueme-So system, which
is influenced by the tropical rainfall pattern of the upper basin of
River Oueme and the tidal currents.
All these inlets have undergone serious changes since the nouakchottian
transgression that put the different barriers in place. First of all, the
construction of successive spits has diverted all the inlets toward the east.
Such is the case of the valley of Zio and of Lake Togo, which used to run into
the sea at the level of Kpeme but today uses the artificial channel, which is the
permanent mouth of Aneho. The Mono River used to pour its waters into the ocean
at Grand Popo; it currently discharges through the opening at Avlo, which became
a permanent mouth only a couple of decades ago. The Oueme River that flowed into
the sea at Lagos before the opening of Cotonou channel in 1986, can only be
explained by this progressive migration toward the east for 5,000 years. These
inlets are often blocked by the construction of different spits, which often
provoke catastrophic floods during the rainy season. Such was the case of
Cotonou in 1985, which prompted the opening of the channel in 1986; even after
this opening, floods were reported in 1907, 1929, 1935, 1942, 1968, and 1987.
Those spectacular floods made it possible to map out marshy regions which
are more than 65% of the area in the Gulf of Benin. They are more widespread in
the estuaries of the Mono and Oueme where there are only few subaerial islands
whose banks are covered with mangroves. In all of the coastal plain, the
depressions between the islands are swamps whose landscapes look like littoral
meadows.
24
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COASTAL EROSION AND MANAGEMENT ALONG THE COAST OF
LIBERIA
DR. EUGENE H. SHANNON
Geologist/Director
Liberian Geological Survey
Ministry of Lands, Mines & Energy
Monrovia, Liberia
INTRODUCTION
Beach erosion affects all coastal countries of the world, including
Liberia.
The environmental consequences have often been devastating. In some cases,
whole communities have been displaced --or worse, wiped out. In addition to
extensive personal properties, major losses have included port facilities,
building infrastructures, recreational facilities, and agricultural, industrial,
and residential land.
As more and more infrastructures are developed along shorelines, erosion
seems to accelerate because of the nature of the type of development. For
instance, port facilities tend to promote erosion. It is, therefore, essential
to keep in mind the interaction of developmental activities with natural factors
so that such development is not threatened at a later date. For example, the
construction of the Free Port of Monrovia, the Hotel Africa, and the Villas has
accelerated erosion, causing loss of beaches and buildings down the coast.
Sea level rise from the greenhouse effect would aggravate all of these
problems. Unfortunately the Ministry responsible for assessing erosion has not
conducted any studies of the implications, of sea level rise, and we were unable
to undertake even a preliminary inventory of the likely consequence -- let alone
the appropriate response strategies. Nevertheless, the Ministry of Lands, Mines,
and Energy recognizes the increasing importance of global warming and the need
to participate in the international process. Given these limitations, this paper
discusses Liberia's current thinking on existing erosion problems, with a hope
that it will help researchers trying to understand how our country would respond
to accelerated sea level rise.
25
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West Africa
The Importance of Erosion
Coastal erosion is a dynamic process resulting from an imbalance between
sand accretion and erosion by the sea or wind. When equilibrium is not
established between accretion and removal of sand, erosion becomes inevitable.
Both manmade and natural factors induce shifts in the equilibrium of
alongshore transport. General topographic, geologic, and meteorological features
constitute natural process components, while the construction of hydraulic
structures, such as port facilities, dams, buildings, and beach mining, tends to
induce the artificial component.
Control of coastal erosion is very important in the context of the
development and management of coastal environments. However, choosing the type
of technology appropriate for solving this problem requires an understanding of
three essential elements:
t the basic physical processes of coastal erosion, such as wave behavior,
currents, and tides;
• human-induced (anthropogenic) changes in the physical coastal process,
which also contribute to erosion; and
• the structural and nonstructural solutions to the problem.
While physical factors and the range of appropriate technologies may exist,
sometimes for a developing country the decision of which technology to use with
regard to cost becomes very complicated because of the relative scarcity of
resources needed for the solution -- e.g., equipment, skilled manpower, financial
support.
The development along the coastal zone has been dramatic in the last few
decades. Construction has included resort settlements, residences, commercial
harbors, and a few coastal defense structures. Most of these structures were
built in response to a particular situation and with little concern for
environmental or downcoast impacts.
COASTAL PROCESSES
The coastal perimeter consists of both landward and seaward portions of the
shoreline. Erosion of the shoreline starts when the removal of sediments is
greater than accretion. Both of these processes -- erosion and deposition --
constantly occur along the shoreline. Therefore, an assessment of shoreline
erosion must consider the difference in the rates of erosion and accretion within
a fixed time span.
The sources of the sand we find on the shoreline originate from upland
drainage systems -- e.g., rivers, coastal fastlands, and offshore outcropping of
landward deposits. These systems are responsible in the long run for secondary
26
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Shannon
sources, such as beaches, sand dunes, and offshore deposits. Any disturbance of
these source materials, for example by wind and water, which are the ultimate
agents responsible for accretion and removal of coastal material, will lead to
erosion.
NATURAL CAUSES OF EROSION
The natural processes of erosion are usually impossible to resist. The
natural shoreline is a result of the interaction between the processes of
erosion, accretion, and meteorological and oceanographic conditions. Any changes
in one of these conditions will result in the transgression or regression of the
shoreline. Natural erosion is a geological process that seeks to establish an
equilibrium among the natural forces. Examples of natural processes of erosion
include the influences of tides, waves, eustatic changes in sea level, storms,
hurricanes, tsunamis, coastal characteristics, and loss of sediment supply.
ANTHROPOGENIC CAUSES OF EROSION
A significant amount of erosion is due to improperly planned human
interferences with natural coastal processes, such as dam and port construction,
beach sand mining, drainage alteration, devegetation and farming, construction
near the shore and beach, disposal of solid waste and landfill sludge, inlet
stabilization, and dredging.
The coast of Liberia is approximately 600 kilometers (350 miles) long. It
includes deltaic plains, fan deltas, coastal plains, and steep slopes produced
by faulting and intense erosion. Part of the coastline is characterized by
drowned valleys with bays, promontories, and pocket beaches. Portions of the
coastline are composed of sand pits, barrier beaches, and lagoonal environments.
Sands of the Liberian coast drift from Harper City in the southeast to
Robertsport City in the northwest. It has been estimated that 7.2 x 106 cubic
meters are transported from rivers annually, and that some 20% of this volume is
redeposited on the coast. A decrease in supply of sand is due to a decrease in
the transport of river sediment and the rate of littoral drift, which results
from the construction of manmade structures on the coast.
PREVIOUS WORK
Studies and remedies related to coastal erosion are primarily the
responsibilities of the Ministries of Lands, Mines, and Energy; Public Works; and
Rural Development.
Three organizations have conducted studies on the coastal erosion of
Liberia: the Japanese Agency for International Development; the Ministry of
Lands, Mines, and Energy; and the LAMCO J.V. Operation Company.
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West Africa
Japanese Activities
In 1978, the Japanese Agency for International Development conducted studies
for three weeks to identify the various causes of erosion along the Liberian
coastline. Their studies took them to Robertsport, Greenville, Harper, Buchanan,
and Monrovia. Two principal causes of erosion were identified by the Agency:
(1) drifting of river outlets, and (2) changes in the balance of littoral
transport caused by blockage of natural sand drifting, which was the result of
human activities -- e.g., construction of breakwaters, beach mining, and possible
reduction of sand supply from the rivers by the construction of the St. Paul
River Dam.
LAMCO J.V. Operating Company
The rate of erosion increased tremendously in Buchanan after erection of the
breakwaters, especially within the port area. Although sand was naturally
deposited east of those structures, active beach mining has also been intensive,
thereby accelerating the process of erosion.
In recognition of these threats to the beaches with regard to coastal
erosion, the Ministry of Lands, Mines, and Energy recommended that LAMCO
undertake countermeasures, especially north of Buchanan, either by constructing
groins or by providing artificial sand nourishment. Dr. Eugene H. Shannon
(Director, Liberian Geological Survey) et al. (1979) reported that two groins,
each reportedly valued at $35,000 (U.S. dollars) were constructed and proved to
be rather effective at the time. Boulder dumping was also instrumental in
reinforcing the shoreline against erosion. After this exercise, the Ministry of
Lands, Mines, and Energy devised a scheme -- Environmental Monitoring --to
monitor the extent of beach erosion from time to time in Buchanan.
Whereas the degree of protection was adequate in certain areas, other side
effects developed, especially along Atlantic Street in Buchanan. While
government, through the Ministry of Lands, Mines and Energy, has continuously
recommended that LAMCO establish more groin systems, progress has been slow.
The Liberian Government
Realizing the degradation of the country's shorelines by wave action,
especially along areas with exorbitant infrastructures, the Government of Liberia
set up a special technical committee in 1981, headed by the Ministry of Lands,
Mines, and Energy, to investigate and find means of safeguarding Hotel Africa,
the adjacent villas, and the beach. Other Ministries included Public Works and
Rural Development. After some studies, the committee estimated the rate of
erosion as approximately 10 feet (3 meters) per year.
Dr. Ntungwa Maasha, formerly Head of the Geology Department of the
University of Liberia, conducted a study between 1980 and 1982 along the Monrovia
coastline between Wamba Town and Yatono. Results of his study indicate that 80%
of the coastline of Monrovia consists of sandy beaches that erode at a rate of
0.5 to 4 meters per year. The only depositional area identified was West Point
28
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Shannon
beach, south of the Free Port of Monrovia. Natural shorelines were identified
in the vicinity of lagoons. Dr. Maasha also reported that the littoral drift is
everywhere from southeast to northwest, and that the long-shore current velocity
varies between 16 and 31 cm/sec.
A three-man Swedish team consisting of Hans Hanson, Lennart Jonsson, and Bo
Broms conducted a one-week study in 1983 along selected areas of the Liberian
coastline. Besides substantiating that harbor construction and other forms of
human interferences have aggravated the erosion problem, they gave an annual
figure of about 50,000-60,000 cubic meters of sand respectively, for deposition
and erosion south of the Free Port of Monrovia. They reported the sediment yield
of the St. Paul River as 1.5 x 106 cubic meters/year. They also reported that
the most frequent waves arrive from south to southwest, and that their heights
change seasonally from 1.3 m (highest) in June to 0.6 (lowest) in March. For
littoral transport, a wave height of about 1.1 m is said to be representative.
A semidiurnal tide is also reported, with a tidal range of about 1-1.5 m. The
tide induces long-shore currents with ebb stream directed to the south and north,
respectively, flood currents being much weaker (5-15 cm/sec, as opposed to 15-45
m/sec for ebb currents).
BEACH EROSION STUDIES IN LIBERIA
Like most coastal nations, Liberia is faced with serious problems as a
result of changes in the configuration of its shoreline due to the activity of
the ocean waves. Erosion is causing shoreline recession in some cities -- for
example, in Buchanan, Greenville, Harper, and Robertsport. Most recently,
alarming incidents of beach erosion along some portions of the Monrovia coastline
have resulted in loss of land and shorefront properties.
Because of the economic and environmental problems associated with beach
erosion, the Government of Liberia -- through the Liberian Geological Survey,
Department of Mineral Exploration and Environmental Research, Ministry of Lands,
Mines and Energy, the University of Liberia, other government agencies, and
foreign institutions, as mentioned in the previous section -- has endeavored to
implement beach erosion studies and recommend possible remedial measures related
to the development of shorefront properties. However, all of these studies have
been focused on Monrovia as a result of finance.
OAU Village
The beach of the OAU Village area is characterized by more or less
horizontal layers of black and brown-white, unconsolidated, medium- to fine-
grained sands. In some areas, especially around Fanti Town, diabase and
melanocratic gneisses outcrop in the sea and serve as wave barriers. As a result
of the change in the balance of littoral transport caused by blockage of natural
sand drift resulting from human interferences, the beach of the OAU Village is
estimated to be receding at the rate of 3 meters a year.
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Uest Africa
New Kru Town Area
The New Kru Town area is characterized by very fine- to medium-grained sand.
The area is separated from the OAU Village by the St. Paul River. At the mouth
of the St. Paul River, the beach is flat and broad, and it is composed of poorly
stratified white clayey sand, which is dusty and crumbly when dry.
The recession rate around the New Kru Town area is more or less the same as
around the OAU Village area. The area is affected by the same phenomena. Away
from St. Paul River, toward Point Four, the beach face becomes narrower,
gradually developing into a high escarpment about 5-7 meters higher.
West Point - Mamba Point Area
The West Point spit/bar, which lies at the mouth of the Mesurado River, has
characteristics similar to those of the area around the St. Paul area, except
that in West Point the flat and broad floodplain of the Mesurado River has been
destroyed by manmade structures, mainly zinc shacks. The Mamba Point area,
however, is characterized by massive diabase outcrops with steep cliffs, which
reflect wave energy, induce offshore sediment transport, and prevent the
formation of any beach. The diabase is well jointed horizontally as well as
vertically. Boulders of diabase that have been undermined by wave action can be
seen in the littoral zone. West Point-Mamba Point is the only area that has been
identified as a depositional area, especially south of the Free Port of Monrovia.
The strip of shoreline from Cape Mesurado to the OAU Village area is within
an embayment. Wave activity is much more complex because of wave refraction at
the cape and at the Free Port breakwaters. This human interference has thus
created an imbalance in the geomorphic system, and the adjustments in morphology
need to be critically investigated.
Namba Point - Elwa Area
The beach area between Elwa and Mamba Point is mainly characterized by
coarse-to-medium to fine-grained sand in alternating black and white layers.
With the exception of the area behind the Executive Mansion and near King Gray,
where large diabase outcrops are discernible, the rest of the beach area is
uniform, with sporadic diabase outcrops in the area.
There is an unusual increase in black sand (heavy minerals) in the Congo
Town area, with band thickness ranging from 1 to 2 feet in some places. This
area of increased heavy mineral occurrences is low-lying, swampy, and separated
from the mainland by small lagoons.
Neutral shorelines were identified in the vicinity of lagoons where sand
accretion and san removal are more or less in equilibrium.
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Shannon
METHODOLOGY
The methodology employed by the Liberian Geological Survey in the erosion
studies of Liberia includes beach profiling, sediment sampling, and the
observation and measurement of the littoral parameters in the field, as well as
granulometric analyses in the laboratory. Aerial photographs and maps were also
used to establish stations for studying and future monitoring (Figure 1).
Field Methods
A ground survey of the entire 35-km Monrovia coastline between the OAU
Village area and ELWA was conducted between May and July 1984. During the
survey, activities were mainly geared toward a better understanding of prevailing
sedimentary processes and also the dynamics of the Monrovia littoral environment.
The following paragraphs provide a complete breakdown of field activities.
Beach Profiling
Permanent features, such as trees, house fences, and electric poles, were
used as reference (bench) marks for profile measurements. In the absence of such
features, temporary markers were installed for easy location. Profiles were
measured along lines perpendicular to the shoreline and extending to the existing
water line. Conspicuous morphological features along the active beach face were
used as survey points. Measurements were made using a surveyor's level and a
stadia rod, and each station included a series of substations adequately spaced
along the beach.
Slope Measurement
The foreshore slope angle was measured directly using the clinometer of the
Brunton compass leveled on undisturbed portions of beach slope. Angle values
given represent an average of readings collected from various places at a given
site.
Wave Measurement
The wave periods at various locations were estimated by timing the breaking
interval of incoming waves. At each location, the estimate was done in
triplicate and the mean was used as the representative value. These mean values
were then combined in statistical fashion, and the resulting average was used as
the representative value for Monrovia and its environs. The average wave period
was subsequently used to empirically calculate other wave parameters, such as
length, height, and celerity.
Wind Direction
The direction of wind movement was measured using a flag and a Brunton
compass. The flag was placed on the beach, and the compass was aligned with it
to give the direction of wind approach. The various directions obtained
throughout the study area were combined statistically to give an average value.
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West Africa
JOHNSON VILLE
EXPL AMATION
Station Location
SHERMAN
LAKE
Fij. I STATION LOCATION MAP
(MONROVIA BEACH STUDY L3S)
KINS 8RAY
Figure 1. Station location map (Monrovia Beach study).
32
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Shannon
Sediment Sampling
The width of the beach varies from 9 m to 27 m. Therefore, a single sample
taken at a station would not serve as a representative sample of a given station.
For this reason, a triangular pattern was used in sampling each station or
substation, with samples taken at the three apexes, as shown in Figure 2.
All samples marked A are those taken on the berm or overwash terrace, while
those marked B and C were taken at the sea edge and at the midpoint between A and
B, respectively.
Each sample was approximately labeled commensurate with the station or
substation number. A geologic description of each sample was noted in the field
book.
Wave Mechanics of Monrovia and Its Environs
Waves approach obliquely to the shoreline in Monrovia and its environs. The
obliqueness increases in the area immediately north of Cape Mesurado, where
shoreline orientation approaches parallelism with the apparent direction of wave
approach.
Of a total of 40 readings of the direction of wind approach, 28 are toward
the southwest, 4 toward the northwest, and 8 toward the southeast (Table 1 and
Figure 3). Values to the southwest are more frequent; they have a range of 77
degrees, a mean of 38.3 degrees, and a standard deviation of 25 degrees. This
indicates that at the beginning of the rainy season (May-June), the Monrovia
coastline receives winds coming predominantly from the southwest (Figure 3).
Considering wind-generated waves (sea waves), the estimated average direction of
wave approach is South 38 degrees West. This bearing compares closely with wind
records at the Spriggs Payne Airfield Meteorological Station.
The mean wave period for the Monrovia coastline is about 12.96 seconds. The
statistical analysis is shown in Table 2. Using empirical equations (Friedman
and Sanders, 1978), the deep-water wavelength (L0) and the deep-water celerity
(C0) were calculated as follows:
L0 = 1.56T2
= 262.02 m
= 1.56T
20.22 m/sec Where T = wave period.
These values correspond to an initial breaker depth (H,) of 13.3 m (L0/20), and
the associated deep-water weave height (H0) is found to be 10.22 m (0.039 L0).
Considering transformation due to shallow-water conditions, the wave-length (L,)
and the celerity (C,) at initial breaking are found to be 139.1 m and 11.33
m/sec, respectively. Wave height at initial breaking (H,) is found to be 10.4
m, and wave break mainly by plunging, with spilling types being observed in a few
places. In the opinion of the authors, the landward limit of the breaker zone
will be marked by a water depth equal to about one-half the deep-water wave
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West Africa
BERM
BEACH FACE
SEA EDGE
BERM
BEACH FACE
SEA EDGE
Figure 2(A). Sample pattern in plan view.
Figure 2(B). Sample pattern in profile.
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Shannon
Table 1.
Statistical Analysis of Wind Direction Along the Monrovia Coastline
(1984 data)
Measured Direction of wind Approach (.Flagging
Set 1
S X«W
10
13
15
17
1 8
v) 9
20
25
27
28
30
50
52
55
60
64
71
75
85
87
Frequency
(f 1)
3
1
1
1
1
1
3
2
1
1
2
1
1
1
2
1
1
2
1
1
^f,«n(- 28
Set 2
SX« E
Z
15
22
25
30
2
37
45
Frequency
(f 2)
1
1
2
1
1
1
1
^f mn9 • 8
Set 3
N X» W
80
83
75
85
Frequency
(f3)
1
1
1
1
^'3*n3*4
^ j. n? _„_„
"
Where IN «Totol ** of meaeured values
N* 28 t 8 t 4 =40
n.« 28/ x 100 » 70% of It
1 /40
«2 * 8 / j^ 1 00 = 2 0% w
/40
n « 4y * 100 » 10% *
/40
Figure 3. Diagrammatic illustration of dominant wind approach for Monrovia,
based on Table 1.
N
w
/\
50
100%
.S
35
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West Africa
Table 2. Statistical Treatment of Wave Period Along the Monrovia Coastline
WAVE
PERIOD
(X) SEC
6.6
7
8
8.9
9
9.8
10
10.7
11
11.5
12
13
13.1
13.8
14
15
15.2
15.5
16
17
17.7
FREQUENCE
(f)
1
1
1
1
4
1
3
1
3
1
5
8
1
1
11
8
1
2
6
1
1
62
f
(f) (x)
6.6
7
8
8.9
3.6
9.8
30
10.7
33
11.5
60
104
13.1
13.8
154
120
15.2
31
96
17
17.7
803.3
RELATIVE
FREQUENCY
f/n
.016
.016
.016
.016
.065
.016
.048
.016
.048
.016
.081
.129
.016
.016
.177
.129
.016
.032
.097
.016
.016
1. 00
DATA
GROUPING
m
(7.5 )
6.5-8.5
m
(9.5)
8.5-10.5
11.5
10.5-12.5
13.5
12.5-14.5
15.5
14.5-16.5
17.5
16.5-18.5
GROUPING
FREQUENCY
3
9
10
21
17
2
-GROUPING INTERVALS CONSIDERED
mid-pt.
1) 4.5
2) 6.5
3) 8.5
4) 10.5
5) 12.5
6) 14.5
7) 16.5
8) 18.5
- 6.5
- 8.5
-10.5
-12.5
-14.5
-16.6
-18.5
-20.5
5.5
7.5
9.5
11.5
13.5
15.5
17.5
19.5
Mode -14.0 sec.
Median- 13.1 "
Mean - 12.96 "
n = 62; x - 12,96 a - 2.53 sec.
height (H0/2). At this arbitrary depth of final breaking (h = 5.11 m), the
characteristic wavelength (Lt) and celerity (Cf) are found to be 90.92 m and 7.08
m/sec, respectively. The wave height at final breaking (Hf) is also found to be
12.57 m.
COASTAL SEDIMENTS OF THE MONROVIA BEACHES
The beaches of Monrovia are characterized by medium- to coarse-grained sand,
consisting of mostly quartz, with iron stains that give a brownish-white
appearance. Heavy minerals (black sand) occur in minor amounts throughout, with
an apparent increase in the Congo Town and ELWA areas, as evidenced by locally
high bulk densities.
Representative histograms of the beach sand are shown in Figure 4 with
respect to locality and the dominant size fractions, and a generalized variation
line is shown in Figure 5. Local deviations from this general line were observed
in the vicinity of rock shorelines where grain size is apparently larger.
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Shannon
BEACH SAND
OUTCROPS
MOTOR ROAD
RIVER OR CREEK
SAMPLE LOCATION FOR
INDEX MAP Of LIBERIA SHOWING LOC
OF BEACH EROSION STUDY AREA
(OAU- EL WA)
g UNITS -2-1 0 I 2 3 4
4 t I 1/2 l/« l/» I/IS
PHI.MILLI>*TER CONVERSION
Figure 4. Map showing sediment size variation along the coast of Monrovia (OAU-
ELWA).
37
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Hest Africa
EXPLANATION
• 1st Most frequent interval
o g id ii ii n
Phi Generalized
(*)
2--
1 ••
o
o ^,-s
1 . •-'' \
o o \
2-
3-
4
i %* 'I
$ Q. i
(A
Millin
variation line (m
• • o o- o
0 „•'" 0 - ^ **
8 IH ^ || 3| |^
neter
m)
•4
2
• 1
.5
• .25
. .125
- .063
* is I8 1
2 "
Figure 5. Graphical illustration of dominant grain size fractions along the
Monrovia coastline.
Littoral Drift
The littoral drift along the Monrovia coastline is toward the northwest.
Using the calculated deep-water wave height (H0), the potential longshore energy
flux (Pis) and the potential longshore sediment transport rate (Q) were
calculated using a representative incidence angle of 78 degrees obtained for the
ELWA-Cape Mesurado shoreline. According to Sabawa et al. (1981), the calculation
is as follows:
Pis = 18.3 Ho 5/2(cos a) 1/4sin 2a
= 1678 joules/sec
Where a = angle of wave of incidence.
Q = 7.5 x 103 (Pis)
= 1.26 x 107 m3/yr
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Shannon
Within the nearshore zone, littoral transport will be affected by waves of
translation. The height of these trans!atory waves was evaluated from the
difference between wave height at various points of breaking and the original
wave height (H0). Hence, the minimum height of the waves of translation along
the coast of Monrovia is estimated as 0.2 m (H,-^), and the maximum height is
estimated as 2.35 (H,-H0). However, a representative height (Hr) of these
translatory waves was estimated using the mean of H, and H, (H.), and the
calculation is given below:
Hm = (H, + H,)/2
= 11.495 m2
= 11.495 - 10.22
= 1.275 m
Therefore, for the littoral transport, a wave height of about 1.3 m is most
probably representative of Monrovia. Using this value for H0 in the equation
given previously, the longshore energy flux is found to be 9.68 joules/sec, and
the longshore sediment transport rate is found to be 7.26 x 104 m3/yr.
The angle of wave incidence for that portion of the study area immediately
north of Cape Mesurado is about 15 degrees. The longshore energy flux along this
strip is estimated as 17.47 joules/sec, and the longshore sediment transport rate
is estimated as 1.31 x 105 m3/yr.
The littoral drift is therefore greater within the vicinity of the Free Port
breakwaters. This indicates that waves within this area have a greater capacity
to transport coastal materials along the shore.
COASTAL BEACH EROSION CONTROL
Various methods are available to fight the coastal erosion problem, but
basically they fall under either structural control or nonstructural control.
Nonstructural Control Methods
Most nonstructural methods only lessen or regulate the problems caused by
erosion, rather than prevent, halt, or retard erosion. They are grouped into
passive and active methods.
Passive Methods
The passive methods include:
• Land-Use Controls: This means that permission should be granted only
for structures that have to occupy waterfront sites. All the structures
associated with permitted waterfront should be movable or, at worst,
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Uest Africa
semipermanent and capable of quick, inexpensive repair. They should
always be designed to minimize damage.
• Coastal Setback Lines: This requires that all constructions on coastal
front should be placed at a safe distance from the shoreline.
Active Methods
• Move Threatened Structures: Threatened structures must be moved a safe
distance from the shoreline. This may be less expensive than trying to
control the erosion that threatens them.
• Vegetative Methods: These methods serve to slow the rate of erosion,
rather than stop it. They include stabilization of sand dunes, and
bluff and bank slopes with plantings, as well as the creation of salt
marshes to absorb wave energy. These methods are employed with
structural methods. For example, where a seawall or revetment is used
to stabilize the base of a cliff, bluff, or bank, plantings may be made
to control erosion from surface runoff and wave overtopping.
Whenever possible and economically practical, every effort should be made
to correct or modify manmade increases in coastal erosion before building what
may turn out to be much more costly erosion control structures.
Structural Methods of Erosion Control
Shoreline-hardening structures make the land mass more resistant to
erosional forces and protect facilities landward from the effect of wave action.
They tend to protect only landward infrastructures and have no beneficial effects
on adjacent shorelines or on beaches seaward of them. Shoreline-hardening
structures include seawalls, revetments, and bulkheads (see Appendix 2 for
diagrams and pictures of these structures). The characteristic design of these
structures will depend on the height, length, shape, and degree of differences
in texture permeability of porosity.
RECOMMENDATIONS
Because of the extent of beach erosion and its imminent threat to
investment, especially along the coastal front, the Ministry of Public Works has
proposed a temporary solution for reducing the rate of erosion at the site. The
technicians at the Ministry have estimated 125 working days at a total cost of
$2.4 million (U.S. dollars). The project includes boulder dumping (with a clay
dam on the villas side facing the sea) over an area 1,800 feet long and 50 feet
wide. Engineering consultants estimated that 100,000 cubic yards of boulders and
40,000 cubic yards of clay would be required (see Appendix 1).
The Ministry of Rural Development also recommended the following tentative
structural measures that are capable of minimizing the erosion problems at Hotel
Africa: Appendix 2, a stone revetment ($0.98 million, U.S. dollars); Appendix
40
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Shannon
2, a curved-face wall ($2.7 million, U.S. dollars); Appendix 2, bulkheads ($1.8
million, U.S. dollars); and Appendix 2, a concrete revetment.
But these structures are just a first step for a small part of the Liberian
coast. At this time it is difficult for us to contemplate the nationwide
response to a rise in sea level from the greenhouse effect. Nevertheless, we
conclude with the recommendations that would help us address both the current
problems and the additional problems resulting from global warming.
1. During the dredging of the port by the National Port Authority, all sand
removed from the port should be deposited on the beach near the Hotel
Africa for nourishment of the shoreline.
2. The National Port Authority should be included on the technical
committee for future study of beach erosion.
3. Funds should be appropriated to the Technical Committee for logistics
that should be used to monitor the rate of erosion. This would provide
data for potential consultants. Also, a soil conservation and pollution
control division should be developed and empowered to undertake long-
range measures for adequate monitoring.
4. A Beach Erosion Control Commission should be created.
5. Specific beaches should be designated for sand mining.
BIBLIOGRAPHY
Fayia, A.K., J.B. Massah, F.T. Morlu and B.O. Weeks, B.O. 1987. A Survey of the
Monrovia Beaches. Monrovia: Liberian Geological Survey.
Friedman, G.M., and J.E. Sanders. 1978. Principles of Sedimentology. New York:
John Wiley and Sons, Inc..
Hanson, H., L. Johnson and B. Broms. 1984. Beach Erosion in Liberia: Causes and
Remedial Measures. Lund, Sweden: University of Lund.
Japan International Cooperation Agency. 1978. Report on the Beach Erosion in
the Republic of Liberia. Tokyo: Japan International Cooperation Agency.
Maasha, N. 1982. Erosion of the Monrovia Beaches. Monrovia: University of
Liberia, Department of Research.
GDL. 1981. Government of Liberia. Report on "Seminar of Beach Erosion at Hotel
Africa" OAU Village, Virginia, Liberia: Government of Liberia, Lands, Mines &
Energy, Public Works & Rural Development, Technical Committee.
Shulze, W. 1971. Notes on settlement research in Liberia. In: Rural Africana,
No. 15, Liberia: An Evaluation of Rural Research. East Lansing, MI: Michigan
41
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Uest Africa
State University.
U.N.D.P. 1972. United Nations Development Program. Heavy Mineral Occurrence
Between Monrovia and Marshall. Technical report No. 5. Monrovia: Liberian
Geological Survey.
White, R.W. 1972. Stratigraph and Structure of Basins on the Coast of Liberia.
Liberian Geological Survey Special Paper No. 1. Monrovia: Ministry of
Information Press.
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Shannon
APPENDIX 1
ESTIMATE FROM PUBLIC WORKS
OAU VILLAGE COASTAL EROSION PROJECT
(Temporary Solution)
Subject: To prevent the coastal erosion at the OAU Village by the sea.
In order to start the work on temporary solution, an access road is needed.
1. Mobilization for access road.
A. Access road 12' wide 6" thickness laterite surface length = 1,800'
laterite = 1,000 C.Y.
Equipment;
1.4 dump trucks
2.1 grader
3.1 front end loader
Fuel consumption:
4 x 25 gallon per day/trucks = 100 gallons
40 gallons per day/grader = 40 gallons
35 gallons per day/front end
loader = 35 gallons
175 gallons/day
For 7 working days, all equipment = 1,250 gallons. 1250 gallons of
fuel for the access road, and 100 gallons of gasoline.
Total cost for fuel consumption @$1.88 x 1,250 = $2,350.00
Total cost for gasoline consumption @$2.09 x 100 = $ 209.00
$2.559.00
Temporary Solution;
Although this solution is costly, it will delay the rate of erosion at the
site. Also, the sand hauling from the beach around the area should be stopped
by the authorities.
The attached drawing gives a physical picture of what is needed at the site
in question and the following are the descriptions:
1. Rolder Rock -- with clay dam on the Village side and facing the sea will be
the Rolder with the length of about 1,800' and 50' wide at the top about
100,000 cubic yards (cu. yd.) of Rolder will be needed and about 40,000 cu.
yd. Clay will be needed.
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Uest Africa
Personnel:
1 Engineer 9 $40.00/day = $ 40.00
1 Superintendent @ $30.00/day = $ 30.00
20 Truck Drivers @ $10.00/day = $200.00
20 Laborers 9 $ 7.70/day = $154.00
10 Operators @ $12.50/day = $125.00
Sub-total = $650.00/day
Equipment: Fuel Consumption/Day
20 - 12 cu. yd.
dump trucks = 550/day
2 Trexcavators = 100/day
1 Dozer D/C = 50/day
1 Front end loader = 35/day
1 Mobile crane = 50/day
2 Pick-ups = 20/day (gas)
1 Man-haul truck = 15/day
1 Compressor* = 830/day
2 Tankers*
* Plus 20% contingency fuel for emergency equipment of the total consumption.
Minimum haulage/day:
4 Trips/day = 12 x 4 = 48 cu. yd.
40 cu. yd. Truck/day
Total volume of rock needed = 120,000 cu. yd.
for 20 Trucks = 48 x 20 = 960
No. = 120.000 = 1.000 = 125 days
960 8
Expenditures:
$650.00 x 125 days = $ 78,000.00
$15/cu. yd. x 12,000
(cost of B. Rock) = $ 1,800.00
Cost of fuel 100 x 125 x $1.88 = $ 235,000.00
Plus 25% of fuel cost for:
Lubricant and fast moving parts = $ 60,000.00
Gasoline 2.09 x 250 = $ 5.225.00
Grand Total $2,178,225.00
Plus 10% contingency $ 217.822.50
Total $2,396,047.50
It should be noted that this solution will only delay the rate of erosion,
until a permanent solution is to be found.
44
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Shannon
Permanent Solution:
There should be a comprehensive study by the Engineering Division to find
the causes of the erosion and the factors influencing it. The following facts
have to be known:
a) Direction of wind
b) Frequency of waves
c) Direction of waves
d) Height of tide
e) Topography of the area
f) Soil test
Submitted by: Emmanuel Oseni
Engineer/CB/MPW
45
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West Africa
APPENDIX 2
STONE REVETMENT
ITEM
Ballast
(above 400 Iba)
Ballast
Contingency
Transportation
Placement
QUANTITY
16764.50
12573.33
12%
20%
7.5%
UNIT RATE
25.00
25.50
Subtotal
Grand Total
EXTENSION
$ 419,112.50
282.900.00
$ 702,012.50
$ 84,241.50
140,402.50
52.650.94
$ 979.307.44
CURVED FACE WALL
ITEM
Excavation
Concrete Work
Form Work
Pile Work
Back Filing
Front Filing
QUANTITY
1955. cu.yd.
6286.67 cu.yd.
12% of concrete
work
15% of concrete
work
8941.04 cu.yd.
1257.33 cu.yd.
UNIT RATE
25.50
250.00
5
12.00
20.00
EXTENSION
Sub-Total:
Plus 15% contingency:
Grand Total:
$ 30,315.68
1,571,667.50
188,600.10
392,916.88
107,292.50
25.146.70
$2,315,939.40
347,390.90
$2.663.330.30
BULKHEAD ESTIMATES
ITEM
Ballast
Contingency
Transportation
Placement
QUANTITY
50,293.33 cu.yd.
12%
20%
8.5%
UNIT RATE
25.00
EXTENSION
Grand Total
46
$1,257,333.30
150,879.99
251,466.66
106.873.33
$1.766.553.30
-------
CRUSHED STONE
UNGEREENED k"
Shannon
Stone Revetment
RIPRAP (lOOOIbs to 6000lb« Averaging 4000lbi)
Chinked Witil One Man Stone
NATURAL BEACH LINE
One Man Stone
20lbs to 150 Ibs
Concrete Revetment
These are lighter construction which primarily functions as shore or beach
protection against erosion from wave, tide, or current actions.
SLAI '/if' &tJte»L«lD
• ft -
SECTION THROUGH SLAB
UNDER JOINT
47
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Vest Africa
Curved Face Wall (Seawall)
This structure is used for moderately severe wave action where the water
level is over the structural base, permitting the full waves to hit the wall.
This structure could also be used where poor foundations exist.
Bulkheads (Breakwaters)
The primary function of bulkheads is to retain fill and secondarily to
resist wave action.
RIPRAP I IDOOIk-•OOO*»)A»«™»B1
4000«w CM***« MM OM
CRUSHED STONE
UNSCREENED 2M*
AND UNDER
(photographs reproduced by permission of the Koppers Co., Inc., Pittsburgh, PA
(U.o.))
48
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IMPACT OF SEA LEVEL RISE ON THE NIGERIAN COASTAL ZONE
L.F. AWOSIKA and A.C. IBE
Nigerian Institute for Oceanography and Marine Research
Lagos, Nigeria
and
M.A. UDO-AKA
Federal Ministry of Science and Technology
Kofo Abayomi, Lagos, Nigeria
ABSTRACT
Widespread erosion, flooding, and subsidence are already devastating vast
areas of the Nigerian coastline causing severe ecological problems that have
compelled the federal government to set up a special relief fund to mitigate the
impact. A rise in sea level of approximately 1 m would aggravate the existing
ecological problems through accelerated coastal erosion, more persistent
flooding, loss of ecologically significant wetlands, increased salinization of
rivers and groundwater aquifers, and greater influx of diverse pollutants. Other
socioeconomic impacts include uprooting human settlements, disrupting oil and gas
production, dislodging port and navigational structures, upsetting the rich
fishery, forcing businesses and industries to relocate, wiping out the fledgling
coast based-tourism, and generally increasing the level of misery. The several
engineering counter-measures being presently proposed for coping with sea level
rise are too expensive for a developing country like Nigeria with huge external
debts. Responding to sea level rise should consist largely of keeping some steps
ahead of the projected rise by slowly "disengaging" from the coast where possible
and establishing and enforcing set-back lines in areas of new development. Where
this is not possible, as in heavily built up areas, emphasis should be on
developing and implementing low-cost, low-technology, but nonetheless effective
options.
INTRODUCTION
Along the coastal zone, probably the main consequence of an increase in
global temperatures is an accelerated rise in global sea level. This will be due
to the melting of alpine and polar glaciers and the thermal expansion of the
ocean surface.
49
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West Africa
Estimates of the projected rise in sea level differ, sometimes markedly
(e.g., from 0.45 to 3.65 m, according to various estimates), but the following
assumptions were accepted at the UNEP/ICSU/WMO International Conference in
Villach, 9-15 October 1985: increased temperature of 1.5-4.5°C and sea level
rise of 20-140 cm before the end of the 21st century, with the understanding that
these estimates may be revised on the basis of new scientific evidence.
This paper examines the potential impact of climate change on the coastal
and marine environment in Nigeria and suggests certain suitable policy options
and response measures that may mitigate the negative consequences of the impact.
GEOMORPHOLOGICAL SETTING
The Nigerian coastal zone extends for a distance of about 800 km between the
western and eastern borders of the country with the Republics of Benin and
Cameroun, respectively. It lies generally between 4°10' and 6°20'N latitudes and
2°45' and 8°35'E longitudes adjacent to the Gulf of Guinea.
The coastal zone is mounted on a voluminous, though localized, sedimentary
protrusion into the Gulf of Guinea ocean basin comprising a 12-km-thick pile of
Cretaceous and Tertiary sediments, close to the juncture of two of the boundary
realms of the Guinea basin (Allen, 1964). The origin and evolution of the
Nigerian coastal zone are closely linked with the Mesozoic (Upper Jurasic to
Lower Cretaceous) opening of the Atlantic Ocean and by different, more recent
phases associated with the structural deformation of the East African Rift
Systems.
The coast is bounded laterally to the north by an extensive river floodplain
(area, 8400 square kilometers), which slopes southward from about 20 m above sea
level in the Onitsha gap (Figure 1). This narrow zone is mounted on the Benue
Valley and contains the main channel of the Niger River before and after
bifurcation. This plain broadens southward with a decrease in slope and
subsequent increase in the density of tributaries of the major drainage channels
and down to the coast.
To the south is the Continental Shelf characterized by more or less uniform
gentle slopes broken at specific points by the recognizable submarine canyons
(Avon, Mahin, and Calabar Canyons).
The Nigerian coastal zone is composed of four distinct units with different
surficial configurations (Figure 2). A 200-km-long barrier lagoon coast in the
western part is followed by 75 km of transgressive mud coast, which tapers into
the dominating 450-km-long and beach-ridge-barrier-island-rimmed Niger Delta;
farther to the east is an 85-km Strand coast where mangrove fronts the sea in the
extreme eastern corner.
A common feature of these geomorphic zones is their low-lying nature. Most
areas along these zones are less than 3 m in elevation. The beach ridges on the
barrier islands that rim much of the coastline constitute the highest grounds
50
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Awosika, et al.
tnza
i—i HILLY COUNTRY
E23 DRY FLAT COUNTRY
DRY LAND & SWAMPS
FRESH WATER SWAMPS
MAN6KOVE SWAMPS
ESTUARIES
BEACH6S AND BARS
rrrr\ MARINE
n n iii
Figure 1. Sketch map showing the main physiographic features of the coastal and
adjacent land areas (after Short and Stauble, 1967).
BARRIER- LAGOON
COAST
Figure 2. Map of coastal Nigeria showing main geomorphic units (after Ibe,
1988).
51
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Vest Africa
with elevation of 2-3 m. In the transgressive mud coast, elevations of less than
1 m are common.
An important feature of the Nigerian coastal zone is that it is part of an
actively subsiding geosyncline. A sequence of dead coralline banks in shallow
waters off the Nigerian coast indicates stages in subsidence or rise in sea level
during the past 4,000 years (Allen and Wells, 1962). More specifically, Burke
(1972) has proposed that all the subsidence (approximately 80 m in about 15,000
years in the northwestern flank of the Niger Delta) can be accounted for by
eustatic sea level rise and isostatic adjustment to water load. The Nigerian
coastal geosyncline is subsiding not only because it was formed in an area of
subsidence but also because of the continued dewatering and compaction of its
sediments that were deposited rapidly. The present rates of subsidence are being
studied by the authors. The only reliable figures available to date reveal
subsidence rates of more than 2.5 cm/yr at the site of a tank farm along the
deltaic coast, after correcting for loading effects caused by the oil in the
tanks (Render Awani, personal communication, 1987).
Socioeconomic Setting
Settlement and Population
The Nigerian Coastal zone comprises all of the Lagos, Rivers, Cross River
and Akwa-Ibom states and the large southern sections of the Ogun, Ondo, Bendel,
and Imo states (Nigeria consists of 21 states).
Recent population projections indicate that up to 30 percent of the
estimated 100 million people in Nigeria live in the coastal zone with population
densities of more than 400 persons per square kilometer in urban centers like
Lagos, Warri, Port Harcourt, and Calabar (Nigeria in maps, 1982). Most of these
urban centers are also port and industrial cities, which accounts for their
teaming populations. Lagos alone is thought to harbour about 8 million
inhabitants. Most of those urban centers are literarily bursting at their seams
with the continued rural-urban drift of the population.
Apart from the large urban centers, several important historical settlements
like Badagry, Forcados, Brass, Abonema, Opobo, and Duke Town, with enduring
monuments of early European contacts and trade, are located on or near the coast.
Populations reaching 150 persons per square kilometer are typical of these
settlements. Oil exploration and exploitation activities in the coastal zone
have given rise to sprawling coastal settlements at Escravos, Brass, Bonny, and
Ibeno-Eket, and several fishing and trading settlements, smaller in size but no
less significant in socioeconomic terms, dot the coastal zone. Some of the
fishing settlements now house fishing terminals with a large work force.
Communications
Apart from a fledgling inland port at Onitsha, all other ports and harbors
in Nigeria are located naturally in the coastal zone. These ports at Lagos
(Apapa and Tin Can), Warri, Port Harcourt, Calabar, Sapele, Bonny, Burutu, Onne,
52
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Awosika, et a7.
and Koko constitute the economic lifeline of the country supporting a hitherto
flourishing import-export trade. Many canals, creeks, and rivers in the coastal
zone, particularly in the Niger Delta, provide sometimes the only communication
links between coastal towns and settlements on the one hand and between these
towns and settlements and the hinterlands on the other hand. This water
transportation system is vital to the country's economy in terms of passenger
traffic and goods haulage.
Of the four functional international airports, only Aminu Kano International
Airport, located at Kano to the north, is outside the coastal zone; the other
three airports are at Lagos (Ikeja), Port-Harcourt, and Calabar. These airports
constitute a rapid link with the outside world and account for heavy movements
of persons, goods, and services to and from Nigeria. Many other local airports
and helipads in the coastal zone provide easy links to these large airports.
The terminals of many road and rail systems in the country are located in
the coastal zone. Besides very important cross-country roads, transport networks
criss-cross the coastal zone; in some cases, these are the only links between the
western and eastern regions of the country.
Agriculture
The coastal zone proximal to the sea is not fit for agriculture because of
the high salinization of soils and aquifers. Beyond the present limits of direct
marine influence are vast agricultural lands afforded by the floodplains of the
Niger Delta and its numerous distributaries. The major staples of Nigeria (such
as yams, cassava, plantains, and rice) flourish on these lands, earning the
coastal zone the nickname "food basket of southern Nigeria"; most of the produce
has found a favorable export market in West and Central Africa. A planned World
Bank-assisted swamp rice cultivation project will further boost food production
from the coastal zone.
The coastal zone fias been found to be a highly suitable area for mariculture
and aquaculture techniques to enhance natural fish production. Although
production from captive breeding currently only modestly contributes to overall
fish production from the coastal zone, projections conservatively place the
productive potential from future fish farming at a significant 175, 150-525,000
tons annually (Talabi and Ajayi, 1984).
Industries
Nigeria has well over 2,000 industrial establishments, about 85 percent of
which are concentrated in the coastal zone. The coastal cities of Lagos, Warri,
and Port-Harcourt are centers of heavy industry; products and activities include
iron and steel, automobile assembly, textiles, Pharmaceuticals, cement, soaps and
detergents, paints, refined petroleum products, electronics, tires, plastics,
brewing, beverages and tobacco, and wool and wood products. About 75 percent
Nigeria's manufacturing industries are located in Lagos and its environs. Warri
and Port-Harcourt have two of the country's three petroleum refineries and two
53
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Hest Africa
of its three petrochemical industries. Warri hosts one of Nigeria's two iron and
steel industries.
In both economic terms and physical layout, the oil industry dominates the
coastal zone (Figure 3). Oil production and export handling facilities,
including structures associated with the ongoing liquefied natural gas project,
dot the coastal zone with constellations at Escravos, Forcados, Warri, Brass,
Bonny, and Ibeno-Eket.
Elsewhere along the coast, local and small-scale industries like wood works,
ceramics, weaving and, boat building flourish around coastal settlements.
Natural Resources
The Nigerian coastal zone has abundant natural resources of great
socioeconomic importance. These resources include forests and wildlife, a vast
fishery, minerals (including oil and gas), and surface and ground water.
Forests and Wildlife
The natural vegetation along the Nigerian coastal zone consists mainly of
strand vegetation consisting of Halophyllons, coastal thickets, and forest in the
area immediately adjacent to the beaches. Mangroves grow in the lower Niger and
the northwestern flank of the Niger Delta. The mangrove forests alone cover more
than 9,000 square kilometers. The mangrove swamps serve as spawning and breeding
grounds for most of the finfish and shellfish resources in the coastal zone.
Swamp and riparian forests are found along the western region, in the upper Niger
Delta, and also fringing the banks of the Niger up to Onitsha. Forest reserves
exist on barrier-bar islands between the Benin and Forcados River estuaries and
east of the Cross River estuary; these reserves form the raw materials for the
timber and plywood industries based in Sapele and Calabar as well as for the
paper and pulp industries in Iwopin and Iku-Iboku. Other natural forest products
within the coastal zone include thriving wildlife (locally, "bush meat"), which
boosts the protein availability , as well as palm oil, fuel wood, and south palm
wine and its derivatives. Apart from helping to meet the protein needs of the
country, the forest is the home of biologically diverse fauna and flora,
including medicinal herbs, that provide a source of scientific interest and
tourist fascination.
Fisheries Resources
Nigeria's coastal zone is blessed with lagoons, creeks, estuaries and, of
course, the shallow inshore ocean, which constitute a major source of the fish
and fisheries products sought by artisanal fishermen.
Before the advent of the oil industry in the late 1950's the coastal zone
served as a base for much of the country's artisanal fisheries. Myriad fishing
settlements established on protected, better drained land or on stilts in river
estuaries and beaches were, and are still, the dominant feature of the well-
watered coastal zone. The artisanal fishermen and women who harvest fish,
54
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Awosika, et al.
Figure 3. The lowland muddy coast of the Niger Delta with oil handling
facilities in the background.
shrimps, and molluscs in the fresh, brackish, and immediate marine waters with
set nets, traps, and other passive gear, use crafts ranging from paddled dugouts
to motorized large canoes. Ajayi and Talabi (1984), based on earlier surveys by
Tobor et al. (1977) and others, have estimated the annual yield of the coastal
and brackish water artisanal fisheries to be between 128,000 and 170,000 metric
tons. The coastal zone remains the base for this artisanal fishery.
Bonga (Ethmalosa fimbriatah sardines (Sardine!la madarensis = Sardinella
eba = Sardinella cameronensisK and shad (Ilisha africana) are the principal
pelagic and semi pelagic components of coastal artisanal fishery. The demersal
component of this fishery targets croackers (Pseudotolithus elonaatus. P. tvous.
and P. senegal_eniis), catfish (Aurius spp.), sole (Cvnoqlossus spp.), shinynose
(Polvdactvlus Quadrifilis). grunters (Pomadasvs spp.) snappers (Lut.ianus spp.),
and groupers (Eoineohelus spp.). Large tarpons (Meqaloos atlanticaK bill
fishes, sharks, and rays are also caught. Shellfish harvested by artisanal
fishermen include white shrimps (Nematopalaemon hastatus = Palaeinon hastatus).
brackish prawn (Macrobrachium machrobrachionK river prawn (Macrabrachium
vollenhovenii). and juvenile pink shrimp (Penaeus notialis =Penaeus duorariumK
The mangrove oyster, Crassostrea gasar. and other molluscs, e.g., Pachyacllion,
are delicacies in high demand.
Artisanal fishery revolving around the above-listed resources not only
contributes to the nation's march toward self-sufficiency in its protein needs
but also provides, particularly in the case of shrimps and oysters (annual
production approximately 48,000 tons, exportable resources with high foreign
exchange earning potential. For example, one metric ton of prawns fetches 12,000
U.S. dollars. The mangrove swamps serve as the breeding and nursery grounds for
55
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Uest Africa
most of the finfish and shellfish resources that are the targets of artisanal
fishery.
The potential of industural fishery within inshore waters is also very high
(Talabi and Ajayi, 1984; Tobor et al., 1977).
Minerals
Nigeria's coastal zone is richly blessed with a variety of minerals. Large
deposits of crude oil have been discovered both on land and offshore,
particularly in the Niger Delta. Nigeria is the sixth largest producer of crude
petroleum oil in the world and the second largest produces in Africa. Nigeria's
production capacity reached 2.3 million barrels per day in the late seventies but
declined to 1.3 million barrels per day as a result of present OPEC restrictions.
Despite this decline, petroleum still accounts for more than 90 percent of the
country's exports and foreign exchange earnings.
Natural gas has also been found in the Niger Delta in commercial quantities
either alone or in association with crude oil. At present, about much of the gas
is flared as there are no large gas utilization projects in the country.
Projected investments in the planned liquefied Natural Gas (LNG) project will
further increase the importance of petroleum to the national economy.
Other mineral resources such as limestone and valuable mineral
concentrations have been reported along the sandy beaches of Nigeria; these
provide raw materials for some coastal industries (Ibe, 1982; Ibe and Awosika,
1986). Coal and lignite occur in the eastern sector of the coastal zone,
particularly east of the northern tip of the Cross River estuary.
Surface and Groundwater
Some decades ago, based on folklore and meager records at the University of
Agriculture and Water Resources, surface water (rivers, creeks, etc.) supplied
the freshwater needs of the coastal zone apart from the director impact of the
sea. But all that has changed, and groundwater is now one of Nigeria's most
important natural resources, especially in the coastal areas. The coastal zone
is heavily dependent on groundwater because of the increasing salinization of
waters of the lagoons, creeks, rivers, and estuaries. The water table is often
less than 9 m near the coast, and varies from 15 m to 39.6 m farther inland. The
groundwater potential of this zone is very high (with a yield several hundred
thousand gallons per hour), due to generally high permeabilities, considerable
thicknesses of the aquifers, and high recharge potentials attributable to heavy
rains.
Present Erosion and Flood Situation
Analyses of historical hydrographic charts and aerial photographs, as well
as data from ongoing research by the Nigerian Institute for Oceanography and
Marine Research, reveal widespread erosion and flooding along the entire national
coastline.
56
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Auoslka, et al.
Present typical rates established at erosion monitoring stations include
more than 18 m at Ugborodo/Escravos, 20 m at Forcados, 16-19 m at Brass, and 10-
14 m at the Imo River entrance (Ibe and Antia, 1983 a, b; Ibe, 1984a, b, c,
1985a, b, 1986, 1987a, b, c; Ibe et al., 1985a, b, c; Ibe and Awani, 1986; Ibe
et al., 1986a, b; Ibe and Awosika, 1986; Ibe and Murday (In Press); Oguara and
Ibe (in press); Stein et al., 1986; Ibe, 1988a, b). Some of these rates are so
erratic and out of proportion with historical rates that sea level rise is
thought to be a part of the problem (Ibe, 1988). An acceleration of the rise in
sea level would further exacerbate the situation.
EFFECTS OF SEA LEVEL RISE ON THE COASTAL ZONE
Increase in Beach Erosion Rates
Although the amount of sea level rise totals a few millimeters per year and
may seem small, it plays a big role in explaining erosion processes affecting
most of the low-lying coastline in the world, particularly in Nigeria. Though
rising sea level does not cause beach erosion per se, other more important causes
are waves, winds, longshore currents, tidal currents, low relief, shelf width,
subsidence, sediment characteristics, offshore topography, and human impact. The
seriousness of sea level rise with respect to increased erosion and flooding can
be deduced from the data of Bruun (1977), which showed that a sea level rise of
0.3 m (1 foot) would cause a shoreline recession of more than 35 m (100 feet).
This may even translate to higher values on low-lying areas typical of the
Nigerian coastal zone.
A rise in sea level of approximately 1 m, which here will be accentuated by
the phenomenon of subsidence, would aggravate the existing ecological problem
of coastal erosion, resulting in loss of wetland and creating a threat to all
installations on or near the coastline.
Flooding
A rise in sea level will result in flooding of the low-lying beaches. This
will automatically cause flooding in the adjacent coastal areas. This is
expected to become even more threatening whenever storm surges coincide with
spring tides.
Many of these barrier islands defend the rich low-lying coastal lands
against storms; they enclose and protect the rich low-lying resources of
estuaries, marshes, and mangroves, all which are highly vulnerable to flooding
resulting from sea level rise.
Many of the barrier island, e.g., Victoria Island, Ikoyi Island, are heavily
developed and urbanized, with most state capitals and settlements situated near
the coast. Flooding of these urban area will result in destruction of properties
and loss of income and lives. Many industries and oil-handling facilities built
near the coastline, particularly in the Niger Delta, will also be affected by
flooding.
57
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Vest Africa
With rising sea level of approximately 1 m, the potential for flooding and
erosion of certain key transportation arteries on barrier islands and others near
the coast will increase. This will lead to a degeneration or interruption of
emergency and other social services. With higher sea levels, existing fishing
facilities, such as jetties, and storage centers built on the coastal fringes
only a couple of feet above the mean high tide line will be subjected to more
frequent tidal and storm inundation. The growing coast based-tourism will be
heavily affected as a result of both increased rates of erosion and persistent
flooding (Figure 4).
Figure 4. Tourist and recreational scene on a beach on Victoria Island with
hotels in the background.
Subsidence
The effects of sea level rise will increase as a result of ongoing
subsidence.
The Nigerian coastal geosyncline, particularly the Niger Delta, is sinking
not only because of tectonic subsidence but also because of continued dewatering
and compaction of sediments that were rapidly deposited.
The authors are studying the present rates of subsidence. The only reliable
figures available to data reveal subsidence rates of more than 2.5 cm/year at the
site of a tank farm along the delta coast, after correcting for the loading
effects of the oil in the tanks (Render Awani, personal communications, 1987).
Human intervention in the coastal zone (e.g., fluid extraction) has tended
to accelerate the subsidence problem. Subsidence associated with withdrawal of
fluids results in the reduction of fluid pressure in the reservoir or aquifer,
58
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Auoslka, et a7.
thus leading directly to an increase in "effective stress" (or "grain to grain
stress") in the system. Compaction results, and basin subsides.
Saltwater Intrusion and Higher Water Tables
The depth to water-table in the coastal zone is often very shallow, and the
groundwater itself is subject to pollution and saline contamination from
seawater. Sweet water in the area is, however, contained in the deeper aquifer,
which probably is in hydraulic continuity with the coastal plain sands.
Many towns and cities situated on the coastal lowlands obtain their water
supplies from the enormous groundwater resources of this hydrogeological
province. Some municipal wells in Port Harcourt yield as much as 90,000 gallons
per hour. A global sea level rise is expected to raise the water table along the
coast and result in increased salinity of the groundwater.
Deforestation
The Nigerian coastal zone is endowed with an extensive and productive
mangrove ecosystem, particularly in the Niger Delta.
Vast and fertile river floodplains have made the delta and other parts of
the coastal zone the food basket of southern Nigeria. Rising sea level will
increase the salinity of the water and soil. Such plants that are not tolerant
to this increased salinity will die. Scenes of dying vegetation are now common
along the Mahin mud beach where saline waters have flooded the adjacent low-lying
coastal areas.
This has resulted in the complete decimation of the once-flourishing rain
and mangrove forests (Figure 5). The lumber industry in Spele is expected to
suffer from the deforestation resulting from increased salinity attributable to
global sea level rise.
Transportation and Communication
Owing to the booming economic activities, an extensive network of roads
(about 4,000 km in Bendel State, 2,500 km in Rivers State, and the new 65-km
Lagos to Epe dual highway built on the Lekki barrier island) has been developed,
while extensive creeks, channels, rivers, and estuaries provide an excellent
water communication and transportation network. Increasing sea level will result
in flooding of these transportation and communications networks.
The state government canals linking the numerous settlements along the Mahin
mud beach are close to being overtaken by the ocean (Figure 6). This could be
disastrous to tertiary institutions, hundreds of secondary schools, commercial
houses, hospitals, hotels, and other institutions in which billions of naira have
been invested.
59
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Uest Africa
Figure 5. Trees dying as a result of saltwater intrusion.
Ocean Dynamics
It has been suggested that sea level rise will cause a continued deepening
of the Continental Shelf beyond the depth of closure and will result in an
increase of effective wave height due to the reduction in bottom friction as a
result of greater depth.
It is hence to be expected that the present ocean dynamics (wave height,
period, length, breaker angle, longshore current direction and magnitude, etc.)
shaping the coastal zone will change. A change or modification of ocean
dynamics, particularly the nearshore dynamics, will affect the sedimentary fluxes
and hence sedimentary budget. This controls the coastline evolution through
erosion, accretion, or stability. These modifications will vary from place to
place, depending on whether the changing dynamics will result in erosion,
accretion, or stabilization. These impacts could be further exacerbated if
storms become more frequent, or winds and currents change.
POSSIBLE RESPONSES
The possible measures that can be taken to mitigate the impacts of sea level
rise on the Nigerian coastal zone can be classified according to whether the
measure will attempt to halt the approach of the sea, i.e., "no retreat"; whether
the measure will allow the sea to rise while avoiding the impacts, i.e.,
60
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Awosika, et al.
Figure 6. The Niger Delta is already experiencing flooding problems which will
only be made worse by sea level rise.
("retreat"); or whether the measure will be an attempt to cope with sea level
rise ("adaptation").
"No Retreat" Measures
"No retreat" measures include construction of the following:
1. Levees, seawalls and revetments, which basically protect the shoreline
from waves and floods; and
2. Construction of groins and breakwaters to act as a wave barrier; this
results in a zone of reduced wave energy, and also helps to trap
sediments.
Generally the "no retreat" measures are very expensive for a developing
country like Nigeria with huge external debts. Examples from other countries
where these "no retreat" measures have been attempted have shown that they have
not worked effectively and, in some cases, have exercabated the erosion and flood
problem. Again, these "no retreat" measures are not capable of abating other
impacts of sea level rise such as higher water tables and saline groundwater
intrusion.
"Retreat" Measures
"Retreat" measures are generally soft regulatory and policy measures that
generally do not require large and immediate expenditure. These measures are
also flexible and can be easily changed in response to new sea level rise data.
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However implementation of such of measures results in the loss of land. Retreat
measures include the following:
1. Set back line: A set back line is a predetermined limit along the
coast seaward to which no settlements or facilities should be located.
Ibe et al. (1984) suggested a set back line of 20 times the determined
rate of erosion.
2. Beach nourishment program: This method is a popular approach used to
protect coastal property and to maintain recreational beaches.
However the success of beach nourishment programs depend on correct
implementation procedures, i.e., choosing the right grain size, burrow
pit, etc. The many beach nourishment programs implemented at the Bar
beach during 1974-75, 1981, and 1985-86 have not very successfully
checked erosion and flooding. This was partly due to incorrect
implementation procedures.
3. Controlled urbanization and capital facilities: The coastal zone of
Nigeria has witnessed sporadic urbanization in the 20 years due to the
oil boom of the seventies. Efforts should now be made to control this
urbanization within the coastal zone. Construction of capital
facilities such as roads, buildings, sewers, etc., should be kept
beyond the reach of projected sea level rise.
4. Public awareness program: Measures to increase public awareness of
the potential impacts of sea level rise should be pursued. Private
developers should be enlightened on the foundation and structural
codes required for buildings in such unstable zones along the coast.
Illegal mining of beach sand should also be discouraged. These san
miners should be made aware of the danger they create by their
actions.
5. Increase in flood plan elevation: Efforts should be made to increase
the elevations of the floodplain or beach ridges around the many
barrier islands. This would help to reduce the potential of flooding
of the adjacent lowland, but preliminary studies show that this is an
expensive option.
6. Afforestation: Limiting deforestation and using reforestation and
afforestation to slow or stop the rise in atmospheric concentration
of carbon dioxide was first proposed during the 1970's. Today it is
accepted as one of the effective ways of slowing down erosion and
denudation of the land. Efforts to afforest the coastal zone should
be stepped up, while deforestion should be discouraged.
7. Studies; Since rising sea level affects all coastal areas, studies
must be initiated with the aim of identifying area that will be very
sensitive to impacts of sea level rise. These studies should also
include collecting data on water level, rates of erosion, subsidence,
groundwater, ocean dynamics, and other facets of coastal management.
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Awosika, et al.
Such studies must be viewed by government and other sponsoring
agencies as essential and not as an academic exercise.
CONCLUSION
Nigeria does not presently have a well-articulated, concrete and enforceable
coastal zone management policy. The lagoon city project, which was intended to
create prime real estate on the foreshore of the Lagos lagoon but instead led to
enormous ecological damage, took advantage of this lack of a coherent policy.
An urgent need exists for national policies with adequate legal provisions for
coastwide, coordinated, and effective management and control of the Nigerian
coastal zone.
BIBLIOGRAPHY
Allen, J.R.L. 1964. The Nigerian continental margin: bottom sediments,
submarine morphology, and geological evolution. Marine Geology 1: 289-332.
Allen, J.R.L. 1965a. Late Quaternary Niger delta, and adjacent areas:
Sedimentary environments and lithofacies. A.A.P.G. Bull 49: 547-600.
Allen, J.R.L., and Wells, J.W. 1962. Holocene coral banks and subsidence in the
Niger Delta. J. Geol. 70: 381-397.
Ajayi T.O., and Talabi, S.O. 1984. The potentials and strategies for optimum
utilization of the fisheries resources of Nigeria. NIOMR Tech. Paper No. 18.
Atlas of the Federal Republic of Nigeria. First Edition 1978. Lagos.
Bruun, P. 1977. Practical solution to a beach erosion problem. Coastal
Engineering 1: 3-_16.
Burke, K. 1972. Longshore drift, submarine canyons and submarine fans in
development of Niger Delta. AAPG Bull. 56: 175-1983.
Ibe, A.C. 1984a. Defending Victoria Island against sea incursion. Special
Report, Lagos, Nigeria: Federal Ministry of Education, Science and Technology,
7 p.
Ibe, A.C. 1984b. Protecting Victoria Island against sea incursion. A position
paper submitted to the Ad Hoc Committee on the Victoria Island Erosion Problem;
August 1984. 5p.
Ibe, A.C. 1984c. A rational strategy for defending Victoria Island against
oceanic surges. In: Proc. Conference on the Bar Beach Surge. Federation of
Building and Civil Engineering Contractors of Nigeria Ltd.
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Ibe, A.C. 1985a. Nearshore Dynamics and Coastal Erosion in Nigeria. Paper
presented at the UNESCO Expert Workshop on WACAF/3 Project; Dakar, Senegal; March
11-19, 1985.
Ibe, A.C. 1985b. Harbor development related erosion at Victoria Island, Lagos.
First International Conference on Geomorphology, University of Manchester,
England; September 15-21, 1985. In: International Geomorphology 1986.
Gardiner, V., ed. pp.165-181.
Ibe, A.C. 1986. Port development related erosion at Escravos, Bendel State,
Nigeria. In: Proc. Man's Impact on the Coastal Environment Barcelona, Spain,
6-13 September 1986. In: Thallasa, Revista De Ciencions Del Mar Special
edition. Villas, F., ed.
Ibe, A.C. 1987a. Marine erosion on a transgressive Mud Beach in Western
Nigeria. In: Proc. Intern. Symposium on Geomorphology and Environmental
Management, Alahabad; India, Jan. 1-20 eds. S. Sighn and R. C. Tiwari (in
press).
Ibe, A.C. 1987b. Collective response to erosion hazards along the Nigerian
Coastline. In: Proc. Coastal Zone, 1987. Seattle, Washington: pp. 741-754.
Ibe, A.C. 1987c. Human Impact on the coastal erosion problem in the west and
central Africa (WACAF) region. In: Proc. International Se Conference,
University of Mauritius, Reduit, Mauritius, 7-12 September 1987 (in press).
Ibe, A.C., and E.E. Antia. 1983a. Preliminary study of the impact of erosion
along the Nigerian coastline. In: Proc. First International Conference on
Flooding, Desertification and Erosion in Africa. Port Harcourt, Nigeria: Rivers
State University of Science and Technology, May 2-6, 1983.
Ibe, A.C., and E.E. Antia. 1983b. Preliminary assessment of the impact of
erosion along the Nigerian shoreline. NIOMR Tech. Paper No. 17p.
Ibe, A.C., and P.E. Awani. 1986. Erosion management strategies for the Mahin
Mud Beach, Ondo State. In: Proc. National Seminar on Flooding and Erosion along
the Nigerian Coastline. University of Lagos, May 1986.
Ibe, A.C., and L.F. Awosika. 1986. Sedimentology of the barrier bar complexes
in Nigeria. NIOMR Tech. Paper No. 26.
Ibe, A.C., L.F. Awosika, and E.E. Antia. 1984. Progress Report No. 2. Coastal
Erosion Research Projects. NIOMR Special Publications; 106p.
Ibe, A.C., L.F. Awosika, A.E. Ihenyen, C.E. Ibe, and A.I. Tiamiyu. 1985a.
Coastal erosion at Awoye and Molume, Ondo State, Nigeria. A report for Gulf Oil
Company (Nigeria) Ltd. 123p.
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Awosika, et al.
Ibe, A.C., L.F. Awosika, A.E. Ihenyen, C.E. Ibe, A.I. Tiamiyu, E.G. Okonya, and
T. Orekoya. 1985b. A study of currents and scouring effects at the proposed
Davy Banks 'A' Location in OML 14. A report for Shell Petroleum Development
Company of Nigeria Ltd. 56p.
Ibe, A.C., L.F. Awosika, C.E. Ibe, A.I. Tiamiyu, P.O. Egberongbe, and S. Orupabo.
1986. The erosion problem at Victoria Island (1900 to Present) and its
solutions. In: Proc. National Seminar on Flooding and Erosion along the
Nigerian and similar coastlines. University of Lagos, May 1986.
Ibe, A.C., A.E. Ihenyen, and C.E. Ibe. 1985c. A hydrographic Survey of the
Proposed Benin Estuary Location OML 43. A report for Shell Petroleum Development
company of Nigeria Ltd. 25p.
Ibe, A.C., and M. Murday. 1986. Aerial Photostudy of recent migration of the
Lagos shoreline. NIOMR Techn. Paper (in press).
Stein, D., G. Echwebber, and A.C. Ibe. 1986. Investigation on the Bar Beach
erosion and a proposal on the maintenance of the coast. National Seminar on
Flooding and Erosion along the Nigerian and related coastlines. May 1986,
University of Lagos.
Oguara, T.M., and A.C. Ibe. Decision Analysis for the selection of erosion
control measures. NIOMR Tech. Paper (in press).
Nigeria in Maps, 1982. Barbour, K.M., Oguntoyinbo, J.S., Onyemelukwe, J.O.C.,
and Nwafor, J.C., eds.
Tobor, J.G., M.O. Okpanefe, J.O. Oladoye, A.L. Ekwemalor, and 0. Oladip. 1977.
Fisheries Statistical Survey of Nigeria. Report 1975-1976 NIOMR, Lagos.
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RESPONSES TO THE IMPACTS OF GREENHOUSE-INDUCED
SEA LEVEL RISE ON SENEGAL
PROFESSOR ISABELLE NIANG
Departement de Geologie, Faculte des Sciences
Universite Cheikh Anta Diop
Dakar-Fann, Senegal
ABSTRACT
The predicted rise in sea level of 1 m from greenhouse-induced global
warming will greatly impact the country of Senegal. The coastline of Senegal is
made up of three large estuaries (Senegal, Saloum, and Casamance Rivers), about
400 km of sandy coastline, and approximately 70 km of rocky cliffs. The low-
lying estuarine areas will be prone to inundation, and the sandy coasts will most
likely experience increased erosion if sea level rises as predicted. The Cap
Vert peninsula, where the majority of the population and economic activity are
concentrated, will be greatly affected. Furthermore, Senegal relies upon the
coast for the income generated from agriculture, fisheries, industry, and
tourism. Coastal towns and cities, like Dakar, Saint-Louis, Rufisque, Mbour, and
Joal, will be required to retreat and/or stabilize their waterfronts.
IMPLICATIONS OF SEA LEVEL RISE
Senegal would be very vulnerable to a rise in sea level, because low-lying
beaches and estuaries account for approximately 90% of its 700-km coast.
Increased coastal erosion would be particularly severe in areas that are already
eroding, such as Saint-Louis, Rufisque, and Joal, and homes would almost
certainly be destroyed. Coastal wetlands, including tidal flats, mangroves, and
tannes would be flooded, upsetting fish and wildlife. Saltwater intrusion into
both groundwater and agricultural lands would increase. Sand spits would breach
more often, and roads and other infrastructure would be lost.
Because two-thirds of the nation's population and 90% of its industry is in
the coastal zone, the nation cannot afford to ignore this issue, nor should
coastal cities and towns. The authorities are aware of the importance of the
coastal zone, but not about the possible acceleration in sea level rise. It will
be necessary to coordinate efforts among authorities, scientists, educators, and
industry leaders, who should all consider the national well-being to be of
highest priority. An action plan is required that would include:
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1. Scientific monitoring of the coastal zone (e.g. beaches, estuaries,
mangrove, qroundwater evolution). No tide data have been recorded since
1964. A network of tide gauges should be established. Swell monitoring
and regular morphological and sedimentological profiles should be
continued.
2. Education of the entire nation about sea level rise and its consequences
through a ma.ior public information campaign. This is especially
critical in a nation of diverse ethnic groups who have long histories
of living and working in ancestral grounds. For example, at Rufisque,
the Lebou fishermen refuse to leave even when their homes are inundated,
because these are ancestral grounds. In other areas, sand miners need
to learn the consequences of their removing sand from eroding coastal
areas, but perhaps more important, they need to learn other occupations
that would provide an acceptable livelihood for them and would be
harmless to the environment.
3. Revision or creation ofstrong and consistent national policies for use
of the coastal zone. This would enhance uses of the coastal zone and
would avoid future problems of inappropriate siting of industries or
populations.
4. Creation of response strategies to a rise in sea level. Developing
countries such as Senegal find it very difficult, if not impossible, to
invest in hard coastal protection works, or even those such as beach
renourishment. Other options will have to be developed for inclusion
in the national policy.
5. Programs to cope with potential relocation of communities, and possible
retraining of people for new skills or occupations. For example,
artisanal fisheries or even certain agricultural activities might be
changed to mariculture or aquiculture. Strong tribal or ethnic ties
that exist in some traditional communal villages on the coast will have
to be considered in any relocation and retraining activities.
6. Programs to develop and encourage new industries, or agricultural
activities to replace others displaced by the effects of sea level rise.
For example, in the Casamance River valley perhaps some peanut and
millet growing might be replaced by more rice growing, which already
exists. Saltworks at Kaolack on the Saloum River have the potential to
increase.
In the absence of detailed studies, it is impossible to be any more specific
about the effects and responses to a rise in sea level. Nevertheless,
considerable knowledge about the coast of Senegal has accumulated. To give the
reader an idea of the environments at risk, the following sections describe the
nature of the coastal environment, the impacts of current changes in sea level
and climate, and the socioeconomic resources of the coastal zone. Geological
details about the coast are found in the appendix.
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THE COASTS OF SENEGAL
The three main types of coastlines in Senegal (Figure 1) are rocky coasts
(about 70 km long), sandy coasts (about 400 km long), and mangrove estuaries
(about 250 km).
Rocky Coasts
These coasts are located along the Dakar and Ndiass horsts. Generally,
their base is covered by blocks, cobbles, and pebbles, which protect them from
wave attack. There are often small bay beaches between adjacent rocky capes.
Sandy Coast
The North Coast or "Grande Cote" (Saint-Louis to Yoff)
Here, the straight sandy beaches are linked with three Quaternary dune
systems: (1) the continental "red dunes," which are about 20 m high; (2) the
yellow dunes, which form a 250- to 4,500-m-wide field that is often 20-30 m high;
and (3) the littoral white dunes, which range from a few to 100 m wide and vary
between a few to 25 m high and are still accumulating windblown sand from the
beach. The interdunes (known as "niayes") are periodically inundated by
precipitation and groundwater, and play an important role in the coastal ecology.
Although they are 3 to 10 m above the sea level, they would be affected by any
rise in sea level due to the backwater effect.
The beaches are relatively narrow (between 40 m at Yoff and 110 m at
Camberene). Sail (1982) suggests that they erode during the dry season and
accumulate during the wet season. The Bruun rule suggests that with a rise in
sea level, the reaccumulation would be less owing to the need for the offshore
profile to rise with sea level. Given the Bruun rule-of-thumb that a one meter
rise in sea level causes one to two hundred meters of beach erosion, it is clear
that even a relatively small rise in sea level could completely eliminate these
beaches.
The South Coast or "Petite Cote" (Hann to D.iiffere)
Unlike the North Coast, the South Coast is characterized by rocky capes and
the absence of dunes (Demoulin, 1967). Because the beaches are lined with a
sandy barrier, however, we consider these areas to be part of the sandy coasts
(Figure 2). These barriers are often adjacent to shallow lagoons (wadi). During
the rainy season, these lagoons and wadi have much higher water levels, which
sometimes causes a barrier to break; this can release substantial organic
material into nearby coastal waters.
The beaches are very narrow (30 to 40 m). Beach rocks stick out of the sand
at the beaches at Rufisque, Bargny-Sienndou, and along the "Pointe de Sangomar"
sand spit.
Because the beaches are very narrow, a rise in sea level could have an even
greater impact here than along the North Coast. In cases where rocky capes lie
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DAKAR
peninsula
*_j Rocky coo»t
Tvl Sondy coatt
^5 Mongrov* •stuary
Presoulil*
gut oiseouE
Cap S Wring
lOOkn
Figure 1. Main coastal types of Senegal.
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• 3 Meter Contour
• 5 Meter Contour
100km
•I
Figure 2. Map of Senegal showing 3- and 5-meter contours.
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Hest Africa
behind the beach, there would be little opportunity for the ecosystem to shift
landward.
Mangrove Estuaries
These estuaries correspond to the three most important rivers: the Senegal,
Saloum, and Casamance. All of these estuaries are characterized by tidal flats,
mangroves, marshes, and tannes. Moving inland from the tidal channel, one
observes first tidal flats, then mangrove marshes with Rhizophora racemosa (5
to 12 m high) replaced by R. harisonnii and R. mangle in the Saloum estuary, then
Avicennia africana (1 to 3 m high). From south to north, owing to climatic
conditions, we notice a reduction of the mangrove population density and a
diminution of the species number (six in Casamance, four in Saloum, and two in
Senegal). The bare tanne is limited by the annual tide level, whereas the
vegetated tanne is also found above this tide level but can tolerate inundation
by freshwater.
These estuaries are also characterized by manmade shell deposits resulting
from the trade of Anadara senilis and the Rhizophora oysters (Gryphea gasar)
since the Neolithic times. They are present in the three estuaries but are
particularly pronounced in the Saloum (Diop, 1986).
Studies on the mangrove population along the Saloum (UNESCO, 1985) have
shown that from the mouth to the upstream part of the estuary, there has been a
height reduction of Rhizophora, diminution of the area occupied by Rhizophora,
reduction of the population density, and augmentation of dead Rhizophora.
Finally, the mangrove disappears upstream of Foundiougne. This regression of the
mangrove environment will be related to the drought, to the human activities (use
of trees for cooking, small-scale exploitation of salt), and to natural diseases.
CURRENT CHANGES IN THE COASTAL ENVIRONMENT
Consequences of the Drought
First of all, there is a renewal of eolian (wind-blown) migration of dunes
due to recent droughts. Along the Grande Cote, white dunes are migrating toward
the continent (2 m/year to 7.1 m/year), the exception being the "Gandiolais"
(south of St-Louis), where the white dunes migrate seaward (11.5 m/year between
1954 and 1980). This phenomenon determines a progressive filling up of the
interdunes (niayes). The migration speed of the yellow dunes varies between 4.80
m/year in the Cayar-Tanma lake sector to 1.3-3.8 m/year at Vele and Pikine. If
global warming worsens drought conditions, we may see an acceleration in the rate
of dune migration.
The lack of precipitations also induces a salinization of the rivers, the
groundwaters, and soils due to the weak or absent freshwater input. Saltwater
intrusion has led to a decline in the mangroves (in Casamance, 70 to 80% of the
mangrove has disappeared since 1969 (Diop, 1986; Marius et al., 1986)). The
reduction of the mangrove population is accelerated by human activities such as
the use of trees for cooking, construction of dams, the rice culture (responsible
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Niang
for 25% of the destruction in Casamance between 1967 and 1982), and the
exploitation of salt (Paradis, 1986). Therefore, tannes are replacing the
mangrove swamps (Marius et al., 1986). For example, between 1973 and 1979, in
the Casamance estuary, Sail (1982) noted that tannes increased 107 km2 while
mangroves declined by 87 km2.
Other consequences of the drought are the acidification and oxidation of the
soils, well studied in the Casamance estuary (Boivin et al., 1986; Marius et al.,
1986). The acido-sulfated soils are characterized by a low pH (<4.5), formation
of jarosite (iron sulfate), and salt precipitation with appearance of gypsum
unknown in Casamance before 1972.
Last, there is a tendency toward salt contamination of the groundwater due
to the lowering of the groundwater table (Boivin et al., 1986).
All of these problems could be made substantially worse if global warming
leads to a drier climate in coastal Senegal. Destruction of mangroves would have
a particularly severe impact on fishing. The threat to water supplies would be
particularly important for communities already struggling with salt
contamination.
Coastal Erosion
Cliff erosion
The speed of a cliff's retreat depends on its type. The Cap de Naze cliffs
are retreating slowly (5.8 cm/year) at the base owing to accumulation of blocks
and pebbles, but five times as rapidly at their summits. The plunging cliffs
(Cap des Biches, Fann) are eroding more rapidly, particularly those made of
sedimentary rocks (32.9 cm/year for the Cap des Biches and 29.3 cm/year for the
Fann cliffs).
Erosion Along the Sandy Coasts
Several parts of the Senegalese coasts are eroding rapidly (DHV, 1979; PNUE,
1985): St-Louis (1.25 to 1.30 m/year), Rufisque (about 1.30 m/year), and Joal in
particular. The impacts are important because all of these areas are densely
inhabited. Consequently, many coastal defense structures have been built,
including seawalls at St-Louis, Rufisque, and Joal, and groins at Rufisque
(Murday, 1986).
The causes of coastal erosion are still unclear. According to Masse (1968)
and DHV (1979), the erosion between Mbao and Bargny is induced by a predominant
onshore-offshore sand transport especially during storms, part of the sands not
being recovered by the beaches. This result is consistent with the slow
continuous rate of sea level rise (a few millimeters per year, Elouard et al.,
1967). In addition, human activities such as the hardening of the coastline by
human construction and especially the extensive sand mining along the Cap Vert
coast (from Cayar to Bargny) are contributing to the problem. Below Bargny, the
littoral drift also contributes to the problem. If sea level rise accelerates,
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there Is little doubt that erosion would Increase proportionately throughout much
of the coastal zone.
The many sand spits are even more vulnerable, even with current trends.
From 1850 to 1980, the "Langue de Barbaric" has seen 24 breaks, which forced the
authorities to stabilize the sand spit. Since then, the breaks have occurred
only south of St-Louis. With an accelerated rise in sea level, additional
protective measures will be necessary.
SOCIOECONONIC ASPECTS OF THE COASTAL ZONE
About the two thirds of the nation's population (about 6.8 million in 1987)
is concentrated along the littoral zone. The population density is between 10
and 20 persons/km2 along the North Coast, 20-50 persons/km2 in the South Coast
and Casamance, and more than 1,800 persons/km2 in the Cap Vert peninsula. Most
of the big cities and towns are located along the littoral zone: St-Louis
(88,404 inhabitants in 1976), Dakar (about 500,000), Pikine (1 million), Mbour
(37,896), Joal (15,665), Kaolack (135,473), and Ziguinchor (69,757). Directly
or indirectly, a rise in sea level would affect all of these inhabitants.
The most important maritime fishing centers are, from north to south, St-
Louis, Cayar, Dakar, Mbour, and Joal. Owing to the seasonal migration of fauna,
in relation to upwellings, the fishermen migrate from north during the dry season
to south during the wet season. Estuaries are important centers for nonmaritime
fishing. The total fish production was approximately 157,000 tons in 1987 with
a predominance of maritime and industrial fishing. Part of the production is
distributed on the great markets, another part is smoked and/or dried, and a part
is exported. Global warming could upset these fisheries both through the loss
of wetlands that support estuarine fishing and as a result of changes in ocean
currents, which could affect maritime fisheries.
The main farm crops along the coast are peanuts (total production of 946.4
thousand tons in 1987) and millet (total production of 801.2 thousand tons in
1987); the rice culture (total production of 135.8 thousand tons in 1987) has
traditionally has been confined to the Casamance estuary, but now is also present
in the Senegal and Saloum estuaries (EPEEC, 1983). Along the North Coast, the
niayes are used for market gardening, which is also practiced in the different
estuaries.
Since 1950, the Senegal estuary has been subject to management of irrigated
perimeters; this development program is now enhanced by the Diama and Manantali
Dams. These projects will permit the irrigation of 250,000 hectares (Michel and
Sail, 1984). Both sea level rise and changes in precipitation could impair the
functioning of these new systems.
Tourism is extensive on the South Coast (Saly, Mbour, Joal) and in Casamance
(Cap Skiring, Kabrousse), where it contributes 31 billion CFA francs per year in
hard currency.
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APPENDIX: THE COASTAL ENVIRONMENT OF SENEGAL
EVOLUTION OF THE COAST
The configuration and the evolution of the coastline in Senegal have been
controlled by three main factors: climate, geology, and hydrodynamics. We
discuss each in turn.
Climate
Senegal's climate is characterized by the alternation of two seasons:
• The dry season: cold, lasting 6 or 8 months during which the N to NW
maritime trade winds are dominant all along the coastline, with some
incursions of the NE continental trade wind or "harmattan."
• The wet or rainy season: hot, during which the precipitation occurs
(80% of the precipitation between July and September with a maximum in
August). The wind regime is dominated by SW monsoon winds.
The main characteristic of this climate is the great interannual variability
of the precipitation. The recent drought has been in effect since 1968 (Olivry,
1983).
Geology
The lithology and tectonics are responsible for the great morphological
subdivisions of the coastline (Sail, 1982). The entire Senegalese coastline
belongs to the Meso-Cenozoic Senegalo-Mauritanian passive margin basin (Bellion,
1987) (Figure A-l).
Tectonics
The Cap Vert peninsula is subdivided by N-S to NNE-SSW faults in two horsts
(Dakar and Ndiass horsts) separated by the Rufisque graben (Elouard, 1980). The
two horsts constitute the higher parts of the coastline (105 m). From Kayar to
Mbour three main fault directions (NNE, NW, and NE) have been identified (Dia,
1980; Bell ion, 1987; Lompo, 1987), and these faults appear to have been active
since the last Pleistocene (Dia, 1980). Furthermore, two subsidence centers are
located in the Senegal "delta" zone to the north and in the Saloum-Casamance
regions to the south. But recent studies (Faure et al., 1980) have shown a
lithospheric rigidity of more importance than predicted.
Volcanism
It is a basic volcanism (Dia, 1980, 1982; Bellion, 1987), subdivided in two
periods:
• The Tertiary volcanism (35.5 to 5.3 MA) is fissural (Dia, 1982). In the
Cape Verde peninsula, this volcanism determines the "eruptive system of
Dakar" (Dia, 1980);
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Vest Africa
LHH »»iflaiiH^TC-ijj
JBJTertiory and Ouorernary
volcanism
QUATERNARY
Littoral dunes
£^21 Fluvio deltaic deposits
dunes
TERTIARY
"Continental Terminal"
Ur^-^l Nummulite limestones
Lower Eocene
I' i '] Paleocene
SECONDARY
Maastrichtian
Figure A-1. Geology of Senegal
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Niang
• The Quaternary volcanism (2 MA to 500,000 ago) is represented in the
extreme west of the Cap Vert peninsula by the Mamelles volcano,
secondary eruptive bodies (Mermoz), and also by about five or six lava
beds and interstratified tuffs (Dia, 1980, 1982; Lo, 1988).
Hydrodynamics
The tidal range is only about one meter on the ocean coast, and less in most
estuaries. The NW swells are dominant and associated with SW swells only during
the rainy season (Figure A-2). On the North Coast, the NW swell determines a NE-
SW littoral drift (Pinson-Mouillot, 1980). Then, the NW swell is diffracted
three times around the Cap Vert peninsula (Riffault, 1980), determining a
divergence in the Hann bay and an E-W current between Rufisque and Hann (Masse,
1968). From Rufisque, the swell obliquity increases, generating a NW-SE littoral
drift with speeds between 0.8 m/s at Bargny and 1 m/s at the Somone estuary
(Demoulin, 1967).
Estimates of volume of sand transport by the littoral drift vary
(PNUE/UNESCO/ONU-DAESI, 1985), but all indicate that the sand transport is much
more important along the North Coast than along the South Coast.
THE MAIN TYPES OF COASTLINE
Three main types of coastlines are encountered in Senegal (see Figure 1)
(Sail, 1982): rocky coasts (about 70 km long), sandy coasts (about 400 km long),
and the mangrove estuaries (about 250 km).
The Rocky Coasts
About 70 km long, they are located along the Dakar and Ndiass horsts. The
cliffs consist of the following:
• Volcanic rocks along the Cap Vert peninsula. The Tertiary eruptive
system of Dakar gives rise to the ankaratrite cliffs of Goree (40 m
high) and Cap Manuel (35-40 m) and to the basanite cliffs of Madeleines
Island and Fann. The Quaternary eruptive system of Mamelles gives rise
to the dolerite cliffs located between Yoff and Fann (10 to 12 m high);
• Paleocene and Eocene marly limestones for the cliffs of Popenguine, Cap
des Biches (13 m high),"anse" Bernard and Madeleines;
• Maastrichtian sandstones and shales for the cliffs of the Ndiass horst:
Cap Rouge (47 m), Toubab Diallao (12m), and Cap de Naze (about 60 m);
• "Continental terminal" sandstones capped by lateritic crust in
Casamance.
These cliffs can be plunging cliffs (Cap Manuel) when they are made of
volcanic rocks, or have a straight to convex face when they consist of
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Uest Africa
Littorol drift
Current
Swell
Canyon
Erosion
l:'.-.;:'':iv.'-j Sedimentation
Figure A-2. Hydrodynamics of Senegal.
78
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Niang
sedimentary rocks (Cap de Naze) (Sail, 1982). Generally, their base is covered
by blocks, cobbles, and pebbles protecting them from wave attack. The abrasion
platforms are very rare (Cap des Biches, Cap Manuel, Fann-Almadies). Between two
rocky capes, there are often small bay beaches.
The Sandy Coasts
The North Coast or "Grande Cote" (Saint-Louis to Yoffl
Here, the straight sandy beaches are linked with three Quaternary dune
systems present above the Eocene shaley limestones (see Figure 1 and Figure A-l).
From the land to the sea, we can distinguish:
• The continental dunes or Ogolian red dunes (20,000-12,000 years ago)
with first NE-SW flattened longitudinal dunes (about 10 m high) built
during the arid Ogolian (18,000 years ago), followed by NNW-SSE to WNW-
ESE dunes of about 20 m high that are the result of Ogolian dunes
reworking during a short arid phase (8,000 to 6,800 years ago) (Michel,
1969);
• The semi-fixated yellow dunes built during an arid phase (Tafolian,
4,000-1,800 years ago) form a 250- to 4,500-m-broad dune field. They are
made of NNW-SSE parabolic dunes, barkhans (Pinson-Mouillot, 1980). Often
very high (up to 20-30 m), they are ended by an abrupt upthrow front
(30-45° steep, more than 30 m high) above the niayes or the red dunes
(Pezeril et al., 1986);
• The littoral dunes or white dunes form a band from a few meters to
hundred meters broad. They are parallel to the coast, the typical form
being the NNW parabolic dunes. The heights vary between a few meters
to 25 m maximum. They began to form during the Subactual and are still
supplied by the beach sands.
The main characteristic of this littoral zone are the interdunes' so-called
niayes, temporarily inundated by precipitation and groundwater. Three to ten
meters above sea level, these niayes are of three different types (Michel, 1969;
Pezeril et al., 1986); they can originate from old hydrographic networks or be
true interdunes. These niayes are characterized by a relictual subguinean
vegetation with the oil palmtree (Elaeis guineensis) bordering them (Fall, 1986;
Lezine, 1986).
The beaches are relatively narrow (between 40 m at Yoff and 110 m at
Camberere). The average slopes are less than 8°. The characteristic forms of
these beaches are beach cusps, with ridges and runnels (Diaw, 1981; Sail, 1982).
Sail (1982) proposed a model of the beach cycle, swell controlled with erosion
during the dry season and accumulation during the wet season and determining a
seasonal balance between the foreshore and the shore face.
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West Africa
The South Coast or "Petite Cote" (Hann to D.iiffere)
Unlike the North Coast, the South Coast littoral zone is characterized by
rocky capes and the absence of dunes (Demoulin, 1967). The beaches are lined
with a sandy barrier, however (see Figure 1 and Figure A-l).
The sandy barrier can lean on a shallow lagoon or wadi or on a rocky
bedrock. Arid during the dry season, these lagoons and wadi are filled up during
the rainy season, sometimes inducing a barrier break with little detrital input
to the coast (Masse, 1968).
Very often, we can observe behind the lagoon the Anadara senilis
Nouakchottian terrace. This terrace, located between -1-2.5 and +3 m, is the
result of the last important Holocene transgression, the so-called Nouakchottian
(max; at 5,500 years ago). This terrace is present at Mbao, Bargny (Demoulin,
1967), between Mbour and Nianing (Elouard et al., 1967), and at Mbodiene (Elouard
et al., 1967; Debenay and Bel lion, 1983).
The sandy barrier(s)., 100 to 150 m wide and less than 5 m high, can present
several aspects (Demoulin., 1967). The fixated barrier (the most common type) is
covered by Opuntia tuna and limited seawards by a mi croc! iff. In the Mbour
sector (Elouard et al., 1977), there is a barrier of several generations, with
the first one very rich in heavy minerals (ilmenite, zircon, and rutile). After
this barrier, there are successive and more recent barriers up to the beach.
o
The beaches are narrow (30 to 40 m) with average slopes of 3 to 4
(Demoulin, 1967), the shore face being more steep (5 to 15°). The beach cusps
are well developed on this coast (Demoulin, 1967) and sometimes consist of
pebbles. The beach sands on this coast are very often titaniferous (amorphous
ilmenite), the more important concentrations being found at Rufisque (33,360 to
92,580 ppm) and Tine Dine island near Joal (131,000 ppm) (Dumon, 1981).
One feature of this coast is the presence of Holocene to Pleistocene "beach
rocks" (Demoulin and Masse, 1969) outcropping on the beaches at Rufisque, Bargny-
Sienndou, and along the "Pointe de Sangomar" sand spit. The first carbon-14
dating made on shells have given an age of 32,500 +2150 years ago (Demoulin and
Masse, 1969), which corresponds to the so-called Inchirian. New petrographical
and geochemical studies (Giresse et al., 1988; Diouf, 1989) have questioned the
previous dating.
Mangrove Estuaries
Representing about 150 km of coastline, these estuaries correspond to the
three most important rivers, from North to South: Senegal, Saloum, and
Casamance.
General Characteristics
In all the estuaries, the common geomorphological units have been formed
during the last Quaternary (Sail, 1982; Diop, 1986).
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Niang
• Tidal channels. They are sinuous except in the Senegal estuary. These
channels present a well-developed hierarchy. The depths are not very
important except in the main channels: 8-10 m in the Senegal, 6 m in
the Saloum, and 8-9 m in the Casamance. These channels present sandy
or clay channel bars, very developed and unstable in the mouth channels.
From north to south, the channel sediment granulometry diminishes.
• Tidal flats-mangrove marshes-"tannes." From the tidal channel, we can
observe in the intertidal zone, first tidal flats then mangrove marshes
with Rhizophora racemosa (5 to 12 m high) replaced by R. harisonnii and
R. mangle in the Saloum estuary, then Avicennia africana (1 to 3 m
high). The sediments are finer in the inner estuary than on its
maritime part. From south to north, due to climatic conditions, we
notice a reduction of the mangrove population density and a diminution
of the species number (six in Casamance, four in Saloum, and two in
Senegal). The bare tanne presents salt efflorescences and is limited
by the very high tide level. The herbaceous tanne is developed beyond
the tide levels but can be inundated by freshwater. It is colonized by
an halophyte vegetation.
• Sandy barriers: with "kjokkenmoddinger" and some "lunettes," they
constitute the rare permanent emerged units (+2 to +4 m high) in these
estuaries. They are, therefore, favored sites for habitat and fresh
groundwater. Well developed in the Senegal estuary, they surround small
lagoonal lows. They are also present along the maritime parts of the
Saloum and Casamance estuaries but less developed. The different sand
spits bordering the main rivers belong to this unit: "Langue de
Barbarie," "Pointe de Sangomar," and "Presqu'ile aux Oiseaux." These
sand spits, built since 3,000 years ago, are N-S oriented due to the
littoral drift.
• "Kjokkenmoddinger" (manmade shell deposits): These are due to the
completion and trade of Anadara senilis and the Rhizophora oysters
(Grvphea gasar) since the Neolithic. They are accumulations sometimes
of huge size marked by the presence of Adansonia diqitata. They are
present in the three estuaries but are particularly developed in the
Saloum (Diop, 1986).
The Senegal Estuary
The estuary is a triangle. First flowing E-W with numerous meanderings, the
Senegal River changes direction from Keur Macene, flowing NE-SW then N-S from St-
Louis, bordered by the 25-km-long "Langue de Barbarie" sand spit. Before
reaching St-Louis, it receives a number of tributaries (Gorom, Lampsar), which
are ancient deltaic channels. From Bogue, the Senegal river bed is situated
below the sea level (-5 m up to St-Louis).
The Senegal estuary presents normal fluctuations with two seasons (Sail,
1982):
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West Africa
• A high-water season (July to November) during which there is a
fluviatile regime. The flood is characterized by an high interannual
variability in relation to the precipitation irregularity. For example,
at Dagana, the annual module varies between 890 m3/s during wet years
and 490 m3/s during dry years. Studies by Kane (1985) and Gac and Kane
(1986) on suspended matter in the "delta" zone showed that the values
are higher than 200 mg/L until the beginning of the flood, then reach
maximum values of 686.4 mg/L (1981) and 415.8 mg/L (1982). From
November, these values diminish to reach mean concentrations of 10 mg/L
during the low water period. The inundated areas fluctuate between
100,000 and 500,000 hectares, depending on the flood quality.
• A low-water season (December to June) during which the saltwater enters
the low estuary. The mechanism of the salt intrusion has been described
by Gac et al. (1986a,b). The salt front was found around Richard Toll
(170 km from the mouth) during wet periods and reached Dagana (217 km
from the mouth) during dry periods.
The Saloum Estuary
It opens into the Atlantic Ocean through three distributaries: the Saloum,
the Diomboss, and the Bandiala separating three groups of islands (Gandoul to the
North, Betanti and Fathila to the South). The three distributaries are connected
by a dense network of small and shallow tidal channels, the so-called bolons.
The Saloum is bordered by a 20-km-long sand spit, the "Pointe de Sangomar." A
mangrove swamp stretches all over the estuary. The main characteristics of the
Saloum estuary are the following:
• Hydrodynamic and hydrological regime: several studies conducted between
1981 and 1984 (EPEEC, 1983, 1984; UNESCO, 1985) have proposed for the
Saloum and Diomboss a reverse estuarine model (Barusseau et al., 1985,
1986) due to the weak or absent freshwater inflow (water discharges
lower than 0.7 m3/s (Diop, 1986)). The characterized model of the
regime is as follows: the flood phase lasts longer than the ebb, with
current velocities generally higher during the flood than on the ebb;
and the Saloum distributaries receive more water than flows back into
the sea (about 66%); the estuarine salinity is always higher than the
seawater, even after the wet season. It increases from the mouth (35%
in the wet season, 55% in the dry season) to the upstream end of the
estuary (respectively, 42 and 88% in Kaolack).
• The Saloum estuary is characterized by the presence of relatively coarse
sediments, and, even if the fine fraction is important, it is silt
dominated. The percentage of carbonates is low (<5%) due to the
mechanical and chemical destruction (low pH) of the shells.
• Studies on the mangrove population along the Saloum (UNESCO, 1985) have
shown that from the mouth to the upstream part of the estuary, there has
been a height reduction of Rhizophora. diminution of the area occupied
by Rhizophora, of the population density and augmentation of dead
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Niang
Rhizophora. Finally, the mangrove disappears upstream of Foundiougne.
This regression of the mangrove environment will be related to the
drought, to the human activities (use of trees for cooking, small-scale
exploitation of salt), and to natural diseases.
• The great development of "kjokkenmoddinger."
The Casamance Estuary
It is, in fact, a ria dominated by the "Continental terminal" sandstone
plateau (30-40 m high) often capped by a lateritic crust (Pages et a!., 1987).
During the last 240 km, the slope of the Casamance is null. Downstream of
Ziguinchor, the Casamance River receives the Diouloulou tributary and there are
numerous small tidal channels interconnected ("bolons"). The mangrove marshes
are well developed with Rhizophora racemosa and Avicennia nitida. followed by the
tannes. There are two types of sandy barriers (TECASEN, 1979). The recent ones,
like the "Presqu'ile aux Oiseaux" which is a sand spit, are N-S oriented in the
direction of the actual littoral drift; the old ones (since about 4,000 years
ago) are oriented NNW-SSE (change of direction of the littoral drift since 4,000
years ago) or NE-SW south of the Casamance mouth (built by the SW swells).
The water discharges are relatively low. During wet years (1962, 1967,
1969, 1975), the annual module was of 6.4 m3/s with a maximum of 32 m3/s. But
now, with the drought, the annual module is of 1.7 m3/s with a maximum of 6.8
m3/s (Pages et al., 1987). Before 1970, the Casamance River had a normal
estuarine function, but now it is a reverse estuary like the Saloum (Debenay et
al., 1987; Pages et al., 1987). Actually, the salinity increases upstream with
values higher than 100% upstream of Sedhiou located 200 km from the mouth (max;
of 170% in June 1986) (Pages and Debenay, 1987).
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RESPONSE TO EXPECTED IMPACT OF
CLIMATE CHANGE ON THE LAGOONAL AND
MARINE SECTORS OF COTE D'lVOIRE
PHILIBERT KOFFI KOFFI
NASSERA KABA
SOKO G. ZABI
Oceanographic Research Center of Abidjan
Abidjan, Ivory Coast
INTRODUCTION
Since 1985, scientists in the Oceanographic Research Center of Abidjan
(Cote d'lvoire) have been studying erosion. Although the southwest shoreline
(Tabou-Sassandra) is stable, the southeast (Fresco-Vridi-Port-Bouet-Ghana) border
is very unstable and is eroding at the rate of 1 to 2 m/year. Although part of
that erosion results from the Vridi Canal and the Bottomless Pit Canyon, the
Fresco-Vridi area appears to be eroding as a natural consequence of current sea
level trends.
The potential implications of an accelerated rise for Cote d'lvoire are
similar to those for other nations in West Africa. Erosion would accelerate
threatening some structures. Perhaps more important are the implications for
the lagoonal systems. If the outer barriers should break up due to erosion and
inundation, these lagoons might become exposed to the open ocean; even where the
barriers remain intact, rising water levels could drown the intertidal wetland
areas. In either event, subsistence fishing in the lagoons would be seriously
threatened.
This paper briefly describes the environmental conditions along Cote
d'lvoire and the administrative structure for dealing with coastal management
issues.
GENERAL DESCRIPTION OF LAGOON AND MARINE ENVIRONMENTS
Cote d'lvoire is located in West Africa on the Gulf of Guinea (Atlantic
Ocean), between latitudes 4° and 11° North; its surface area is 322,463 square
kilometers. Its 500-km coastline is fringed with 350 km of lagoons, which are
separated from the sea by a narrow offshore bar and a narrow continental shelf.
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Of the nation's 10 million people, about 3 million live along the coast (about
2 million in and around Abidjan).
The climate is warm and humid in the south and tropical dry in the north,
which results in two major types of vegetation: guinean (dense forests and pre-
forest savannahs) and Sudanese (savannahs). The economy of Cote d'lvoire is
essentially based on agriculture: traditional agriculture using slash and burn
techniques, and industrial plantations using very extended land areas. The
industrial growth rate for the last three decades has been about 7% from 1960
to 1984.
Lagoons
Lagoons are found along 60 percent of the coast and cover about 1200 square
km. There are three main lagoons (Grand-Lahou, Ebrie, and Aby Lagoon) connected
with the sea and each other by natural or artificial channels. Grand-Lahou
lagoon, which covers 190 square km, is the smallest and shallowest (average depth
of 3 m). The Bandama River, which drains the largest watershed of Cote d'lvoire,
flows into it. Ebrie Lagoon, in the middle, covers 566 square km and is on an
average, 4.8 km deep. It is connected to the sea by the Vridi Canal and Grand-
Bassam Channel. Aby Lagoon, near the Ghana border, covers 424 square km.
Lagoonal seasons are determined by riverflow and rainfall. The dry season
(January to April) is characterized by marine influence (maximum temperature and
salinity). During the rainy season (May to August), heavy rains swell forest
rivers. The flood season (from September to December) corresponds to maximum
inputs by "Sudanese" rivers (Comoe and Bandama) causing lagoon salinities to
approach zero.
A change in climate-could affect these lagoons in many ways. The inundation
of intertidal vegetation would remove important habitats for fisheries. Erosion
and flooding would increasingly threaten establishments along the shore. Rising
seas and decreased precipitation would increase the salinity of the lagoons,
perhaps leading to increased predation in some cases.
The Open Coast
There are two types of landscapes in the coastal region: (1) cliffs of
the southwest (from the Liberian border to Fresco) are characterized by a step-
like profile where a narrow quaternary coastline and the contact of the
precambrian plinth alternate. These plateau-coasts, cut as abrupt or gently
sloping cliffs, are elevated more than 20 m above sea level (more than 65 m in
the San Pedro sector); and (2) sandy low coasts (from Fresco to the Ghana
border), which have flat landscapes where the quaternary shoreline is more
developed (maximal width 4,500 m) and continuous. Low plateaus of the nearby
inland areas are generally less than 12 m above sea level. The land adjacent
to the sandy shorelines is usually 2-6 meters above sea level -- even lower near
Assinie.
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There are two major marine seasons: a major warm season (from February
to May) during which water temperatures vary from 27 to 28°C; and a major cold
season (from July to October) during which the upwelling is more distinct, water
temperatures are less than 23°C, and the salinity is near 35%. Beside these two
distinct seasons, there is a short warm season (November to December) with the
disappearance of the upwelling, and a short cold season (December to January)
with a coastal upwelling and water temperature varying from 24 to 25°C.
If sea level rises one meter, the Bruun rule implies that sandy beaches
could erode 100-200 meters, which would threaten some establishments along the
coast. In addition, upwelling and other aspects of the marine climate have an
important impact on fisheries. If climate change alters the seasonal or
geographical extent of upwelling, fishing would probably be affected.
PROTECTION OF THE ENVIRONMENT IN COTE D'lVOIRE
Administrative and Institutional Efforts
Environmental protection is a national concern. Among the institutional
establishments dealing with this subject are the Oceanographic Research Center,
the Tropical Ecology Institute, the National Agency of Meteorology, the National
Committee for fighting bush fires, and nongovernmental organizations like the
Green Cross. Cote d'lvoire has also signed several international conventions
in environmental protection. Actions against environmental degradation include
the monitoring of coastal erosion.
Shoreline evolution and coastal erosion have been studied since 1985 at
18 stations from Tabou to Assinie. The initial results are as follows: (1) the
southwest shore (Tabou-Sassandra) is stable because of its geology and steplike
formation; and (2) the sandy low coast at the southeast (Fresco-Vridi-Port-Bouet-
Ghana border) is very unstable and is eroding at 1 to 2 m/year. This area in
turn can be divided into an area with natural erosion (Fresco-Vridi) and an area
where erosion is linked both to the presence of the Vridi canal and the proximity
of the "Bottomless Pit" canyon (Vridi-Port-Bouet).
The aim of this erosion study is to establish a coastline sensitivity map.
This map will include the geology and coastal shapes, erosion and sedimentation
rate of the coastline, coastal drift, the topography of the coast, and inter-
tidal zones. This study will help in managing (1) passive measures of coastal
protection; (2) the exploitation of quarries (sand and others); and (3) refining
a sedimentation model built to predict erosion and the effectiveness of
protection options for the Abidjan area.
With respect to the fight against deforestation, Cote d'lvoire has
established a permanent national forest domain in the thick forest and savannah
zones (decree no. 78-231 of 3/15/78), which includes a total of 5,921,558
hectares divided into 205 forests and parks. A program of reforestation favoring
rapid-growing species of trees is being instituted, which will help slow global
warming by providing a natural sink for carbon dioxide.
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Ma.ior Constraints to Environmental Protection
An obstacle to protecting and managing the environment is the antagonism
between environmental and developmental forces, which must be reduced to achieve
the benefit of an effective equilibrium between the two.
The search for this precarious equilibrium is sometimes difficult because
of the ingrained habits of people, which are often detrimental to the
environment, and because of financial constraints.
CONCLUSION
The Ministry of Defense and the Ministry of Scientific Research coordinate
national activities related to research and monitoring of meteorological and
oceanographic surface conditions among all regional institutions with
responsibilities for studying climatic variability and its local impact. We need
to establish public education projects to promote an understanding of changing
climate and rising seas, to assess its potential impacts on society, and to
encourage regional scientific centers related to environmental research to
establish studies to identify the vulnerability of particular geographical areas.
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IMPLICATIONS OF GLOBAL WARMING AND
SEA LEVEL RISE FOR GHANA
J. F. ABBAN
Hydrology Division
Architecture and Engineering Services Corp.
Accra, Ghana
ABSTRACT
This paper identifies coastal areas in Ghana subject to erosion and some of
the causes of erosion, such as artificial structures along the coast or river
barriers. The socioeconomic aspects of sea erosion are also highlighted,
including the displacement of people with subsequent destruction of economic
activities, and the threat to tourist activities. Some of the studies conducted
to evaluate shoreline recession are discussed, as are attempts that have been
made to arrest or to contain sea erosion. Finally, this paper addresses sea
level rise and ways to assess it with data that could be obtained in Ghana.
INTRODUCTION
The Ghanaian coastline stretches roughly 550 km from Half Assini in the west
to Aflao in the east. A substantial number of dwellings, commercial activities,
and industries, as well as fishing and tourism, are found within 300 m of the
ocean coast. Coastal areas can be grouped into three basic economic categories:
1. Commercial and industrial areas, such as Accra, Tema, Sekondi, and
Takoradi;
2. Fishing areas, such as Tema, Keta, and Winneba; and
3. Tourist areas, such as Batianor, Ada, Labadi, Biniwa, Elmina, Winneba,
and Busia.
Coastal erosion is experienced in varying degrees; the adverse effects on
developments along the coastal zones cannot be overemphasized. The immediate
result of shoreline retreat is the loss of land, which in almost all cases
results in loss of properties and displacement of people. Erosion greatly
affects the social and economic activities of coastal dwellers and users. Lack
of economic activities means lack of jobs or forced change of vocation, with a
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subsequent loss of revenue to the government. New fishing areas must be sought,
and tourist sites are threatened. A typical example is Keta, where portions of
the/population had to seek shelter elsewhere because properties had been engulfed
by the sea. The Labadi pleasure beach, until coastal protection measures were
carried out, lost its tourist business to other areas. Bortianor, another
tourist spot, is being seriously threatened by coastal erosion.
COASTAL ZONE
Most of the coastal areas in Ghana are low-lying and sandy, interspersed
with beach rocks and rock outcrops. In some areas experiencing active beach
erosion (see Figures 1 and 2, which show shoreline changes for Keta and Ada,
respectively), shoreline changes have been monitored; these areas include Axim,
Dixcove, Nkontompo, Labadi, Ada, and Keta. Records for periods indicated in
Table 1 have been kept for Keta, Ada, Labadi, and Nkontompo.
Table 1. Periods of Shoreline Monitoring
Town
Period
Remarks
Keta
Ada
Labadi
Nkontompo
(Sekondi)
1907-87
1971-87
1941-85
1980-86
1954-65
1968-71
1956-86
1971-86
Soil logging
Beach profile monitoring
Soil logging
Beach profile monitoring
Soil logging
Beach profile monitoring
Geological data
Beach profile monitoring
Studies conducted on these areas indicate the following major causes of
erosion:
1. Creation of artificial barriers across some rivers (e.g., the Volta and
Densu), which reduce or otherwise interfere with the sediment load to
the coast;
2. Creation of artificial harbors (e.g., the Takoradi and Tema Ports),
where breakwaters and jetties interrupt littoral transport of sand and
other sediments;
3. The mining of sand along the coastline, which removes supply material
from the coastal zone so that natural shoreline stability is diminished;
and
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ATLANTIC OCEAN
Figure 1. Successive flooding and erosion through the years at Keta.
Figure 2. Successive flooding and erosion through the years at Ada.
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4. Natural, constant coastal processes (e.g., subsidence, seasonal and
interannual wave climate variability, and tectonic movement).
WETLANDS
The Ghanaian wetland ecosystem has not been exhaustively studied in the
environmental context, but a few studies have been conducted through the graduate
school at the University of Cape Coast. The Environmental Protection Agency of
Ghana is generally responsible for the policies developed to protect the wetland
ecosystems.
Two types of marsh-ecosystems are found in the West African region:
1. Wet-humid areas dominated by grasses and marshy shrubs (found near small
estuaries and lagoons); and
2. Mangrove-type vegetation dominated by almost all types of hydrophilic
angiosperms (with monocots of oil palm in plantations near large
estuaries).
Human habitation is common in the areas described above, since these
ecosystems are also dominated by fauna that form the economic basis of the
region. Fishing is the predominant activity in Ghana and the west coast of
Africa. Most of the wetlands on the Ghanaian coast are natural, and human
habitation and industry have not yet taken their toll. Mangroves generally are
not cut, except in cases where land has to be cleared for farming purposes, e.g.,
rice farming. This is all the more reason why specific policies and research
leading to protection of such areas should be initiated now.
SALTWATER INTRUSION
Coastal river estuaries are subjected to saltwater intrusion. Low riverflow
allows seawater to intrude farther upstream. This tends to seriously affect the
drinking water supply in areas such as Ada and Keta, where the local residents
rely on groundwater as a source of drinking water. In some cases, the high
salinity of the groundwater has made the water unsuitable for drinking.
FLOODING
Flooding along the coastal areas occurs in Accra, Botianor, and Keta.
Floods in Accra are mainly due to improper planning or to the inadequate drainage
system. Efforts to desilt and improve the hydraulics of the primary drains
(stormwater channels), coupled with various maintenance schemes, have
significantly reduced flooding in Accra.
Flooding in Botianor Is due mainly to releases from the Weija Reservoir (one
of the impounding waters providing Accra with a water supply) during the rainy
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seasons. This could be controlled by proper regulation of the Weija Reservoir,
channeling the river downstream from the dam, and construction of a proper
outfall to the sea.
Since the early 1960's, three floods in Keta have been caused by excess
water discharged into the Keta Lagoon from the Todzie and Belikpa Rivers during
exceptionally wet seasons. The creeks connecting the Keta Lagoon to the River
Volta estuary are blocked and, therefore, the excess water is impounded in the
lagoon instead of being discharged into the sea.
POPULATION
About 13.5 million people were estimated to live in Ghana in 1987, with a
large percentage residing in the coastal zone where most of the major cities are
located. Population density in the coastal urban areas exceeds 550 people per
square kilometer, 10 times the density of inland areas. The last three
population censuses indicate that the Keta area (including Kedzi and Vodza) is
being rapidly depopulated, the result of severe erosion coupled with non-
availability of land.
COMMERCIAL ACTIVITY
Ghanaian coastal area inhabitants are primarily fishermen, except for those
directly in commercial centers such as Labadi, a suburb of Accra (the capital of
Ghana), Tema, and Sekondi. Although Keta used to be a bustling commercial
center, these activities have dwindled to nothing because of severe waterfront
erosion.
TOURISM
Some of the tourist beaches along the Ghanaian coastal zone are Ada,
Chemuna, Labadi, Botianor, Biriwa, Elmina, Winneba, and Busia. Erosion of
varying degrees has been recorded in these areas.
AGRICULTURE AND FISHING
The most important crop in Ghana is cocoa, which accounts for about 60
percent of the nation's exports. Although the cocoa-growing area is not located
in the coastal zone, shipments must pass through the coastal ports. Production
of corn and other grains is substantial and is increasing. Data for 1969
indicate that production of corn and rice totaled 305,000 and 61,000 metric tons,
respectively; fishing produced 162,800 metric tons. In 1969, salt production
totaled 1,700 metric tons in the coastal lagoon area.
Although fishing is the mainstay of the coastal people, some inhabitants
move inland to practice arable farming during the off-season. Some of the local
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farms along the fringes of the Keta Lagoon primarily cultivate shallots, rice,
sugarcane, okra, pepper, and maize. These farming activities are disrupted each
time the Keta Lagoon is flooded.
COASTAL LAND DEVELOPMENT RESTRICTIONS
No consistent rules seem to limit coastal land development. In the past,
coconut trees planted along the coast indicated the off-limit zones for building
structures. However, the zones vary from place to place; in some beach areas,
structures are very close to the coastline.
In areas of active sea erosion, such as Keta, Vodza, Kedzi, and Labadi, the
coconut plantations have been claimed by the sea; thus, development, previously
behind the plantations are now close to the sea.
STRUCTURES ALONG THE COAST OR COASTAL WATERS
Four major ports are located along the shores of Ghana: Tema, Elmina,
Sekondi, and Takoradi. Sekondi is a naval port, and Tema and Takoradi are
commercial ports. Tema has a fishing port attached, and Elmina is purely for
fishing. All four harbors are manmade, and their breakwaters protrude into the
sea. Elmina harbor has two basins: the inner basin is in the Benya Lagoon, and
the outer basin is at the mouth of the lagoon where the lagoon water discharges
into the sea.
Apart from Tema harbor, where erosion is occurring on the western side of
the breakwater structure, erosion is occurring on the leeward (eastern) side of
the harbors.
Takoradi and Tema have tidal gauges. The Takoradi and Tema harbors were
opened in 1928 and 1962, respectively. The tidal gauge installations are as old
as the ports. Hydrological gauging stations are also located in the Keta Lagoon
and on the Volta estuary at Ada. Hydrological gauges were established at Keta
and Ada in August 1963 and September 1963, respectively. The mean range of the
semidiurnal tide along the Ghanaian coast is a nearly uniform 1.0 meters.
EFFECTS OF A ONE-METER SEA LEVEL RISE
A one-meter sea level rise would have a serious negative socioeconomic
impact on the country, causing storm flooding, beach and coastal erosion, and
loss of wetlands.
Storm Flooding
A one-meter rise in sea level would create a higher mean water level in
coastal lagoons and estuaries. This, combined with high riverflow due to heavy
rainfall, would exacerbate the flooding that presently occurs. Such flooding
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would cause additional loss of property and would very likely require relocating
whole communities and industries.
As indicated previously, Accra and Keta are but two examples of areas of
constant flooding. Although Accra and Botianor floods are attributed to an
inadequate drainage system and improper regulation of Weija Reservoir,
respectively, these areas, like many coastal towns, have drainage outlets subject
to tidal influence of the sea. Flooding affects industries through inundation
of warehouses, which results in damage to equipment, raw materials, and
manufactured goods. Some residential areas near natural drainage channels are
constantly flooded during the wet season.
The traditional reaction of local people is to move out until the floods
subside and then to move back again. Some people, however, tend to find
permanent accommodations elsewhere.
The government antiflooding program, especially in Accra and other coastal
areas, focuses on improving the drainage system in these areas. The government
is also discouraging development of lowland areas.
The projected sea level rise would allow water pushed by coastal storms to
surge farther ashore with devastating effects.
Beach and Coastal Erosion
The projected one-meter rise in sea level would exacerbate the erosion
already seen along the low-lying sandy coast of Ghana. Loss of these coastal
lands would have a far-reaching socioeconomic impact on the nation. Coastal
tourist enterprises would be at risk; commercial and industrial sites would need
major protection or relocation. Agriculture in the near-shore zone might suffer,
requiring inhabitants either to move or to change crops to remain productive.
Loss of Wetlands
The rate of natural growth and migration might not be able to keep pace with
the rate of wetland submersion caused by rapid sea level rise. Consequently,
valuable wetlands could be lost. A more gradual rise might permit wetlands to
survive and migrate. Wetland migration could occur only in areas having no
barriers to lateral displacement. Agricultural lands, sharply rising land
contours, dams, or other barriers would interfere with migration.
IMPACT ON FUTURE DECISIONS
Sea level rise would certainly influence the development of new settlements
and the use of beaches as recreational grounds. Existing laws would have to be
enforced or modified, especially regarding restrictions on development of the
coastal zone. Decisions would have to be made concerning whether or not to
resettle people affected by sea level rise.
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Response to Sea Level Rise
The country will have to reassess its planning with regard to development
along the coastal area once the sea level rise impacts have been identified and
quantified.
Historical records of the tidal and hydrological stations mentioned
previously, together with studies conducted so far at Keta and Ada and aerial
photographs, could form the basis for the study of the sea level rise.
Although dozens of culturally different tribes live in Ghana, the people are
well integrated into a whole national fabric. The Ghanaian educational system
is one of the best in the West Africa region, with a literacy rate that stands
at roughly 30 percent. The government is striving to rehabilitate and strengthen
the national economy; therefore, many issues have more immediate concern than sea
level rise. Educating and informing everyone at all levels of government and
industry, as well as the general public, of the need to plan and prepare
responses to rising sea level will be a formidable task.
Preparations also will be formidable. These will encompass the entire
spectrum of the nation's business: enhancing education, enacting legislation,
establishing government agency responsibility for oversight or regulation,
monitoring industry and private sector activity in the coastal zone, carrying out
scientific monitoring programs, and conducting research to assess impacts of sea
level rise. Such research must address geomorphological impacts and must also
provide important information upon which to base appropriate responses to
socioeconomic impacts. Cultural impacts must be considered as well.
Property Ownership
In Ghana, land is entrusted to the government (local authorities) or to the
"stool" (kings or chiefs as custodians). Land for development can therefore be
leased to interested parties by these agencies.
The government could only advise people to move as the sea level begins to
rise and areas are threatened. Experience in Keta and elsewhere has shown that
people are not very willing to vacate their houses, let alone resettle elsewhere,
when being threatened by the sea. In most cases, people move out or migrate only
when their houses have been destroyed by the sea. There have been instances
where people have built more than one house that has been engulfed by the sea.
COASTAL PROTECTION IN GHANA
Ghana has protected its coast since the 1920's.
Bulkheads
Steel sheet pike bulkhead was tried in Keta in the sixties. The average
depth of the pile was 10 m. Even though this form of sea defense wall was
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expected to last at least 40 years, it started to fail within 6 years after
construction and has now collapsed completely.
Stone Revetment
Stone revetment in the form of armor rocks has been successfully tried at
Sekondi. About a kilometer of road lined with houses has been saved from sea
erosion.
Another successful form of stone revetment is the gabion revetment. Tourist
spots such as Labadi and Elmina have been protected since 1981. A gabion armor
rock revetment is currently being put in place at kilometer 22 along the Accra-
Tema beach road to prevent that section of the road from being engulfed by the
sea.
Groins
Wooden groins were tried in Keta several times between the 1920's and 1960's
without much success. Pilot gabion groins constructed along the James Town
Beach, Accra, about 5 years ago appear to be very promising, and they are being
monitored for eventual adoption along some sandy beaches.
Sea Outfalls
A rubble mound outfall structure constructed in the sixties at James Town
to help with the runoff from stormwater and sewage had no adverse effect on the
coastal morphological changes in the vicinity.
Subsidence
Land subsidence has not been investigated much in Ghana, but there is reason
to suspect that subsidence might be contributing to the severe erosion occurring
at Keta.
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SOCIOCULTURAL IMPLICATIONS OF
CLIMATE CHANGE AND SEA LEVEL RISE
IN THE WEST AND CENTRAL AFRICAN REGIONS
0. OJO
Department of Geography
University of Lagos
Lagos, Nigeria
ABSTRACT
This paper begins by examining what is presently known about the
characteristics of climate and climate variations in the West and Central African
(WACAF) regions and then looks at the socioeconomic and sociocultural
implications of the environmental impacts of climate change and sea level rise.
Also discussed are strategies that could be used to reduce or eliminate the
vulnerability of human settlements and environmental systems, as well as
socioeconomic and sociocultural systems, to the adverse consequences of climate
change and sea level rise.
INTRODUCTION
Since the beginning of time, the world's climate has fluctuated. In the
West and Central African region, for instance, there has been a great variation
in rainfall, which in turn has affected environmental processes and human
activities in the region. The impact on geological processes has influenced and
indeed severely disrupted local, regional, and even global socioeconomic and
sociocultural systems (for example, natural resources planning and management,
food production and agriculture, water resources and energy systems, forestry,
marine resources development, transportation, and tourism).
There is mounting scientific evidence that human activity is partly
responsible for changing the earth's global and regional climates. Although it
is difficult to distinguish between ecological changes due to human activities
and those caused by natural processes, there is no doubt that the differences
in climate between various parts of the earth has in large measure determined
the types of activities people pursue for both recreational and productive
purposes.
This paper examines the impact of climate change on the West and Central
African regions, with particular focus on the sociocultural implications of the
greenhouse warming and the rise in sea level.
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WEST AND CENTRAL AFRICA: CLIMATE CHANGE AND VARIABILITY
Future climate changes are likely to have a significant impact on the marine
environment and the adjacent coastal areas. The coastal areas of West and
Central Africa extend from the coast of Mauritania in West Africa to the coast
of Angola. Most of the region is in the tropics and spans the low latitude
areas between approximately 30° N and 30° S.
Annual precipitation varies from less than 200 mm in the north and south
to over 2,000 mm in the western equatorial regions, most of the area receives
between 200 and 1,000 mm of rainfall per year. Of this total, 75% or more of
the precipitation falls during the rainy season, which lasts between 6 and 12
months in the central part:; of the West and Central African region, and less than
4 months in the extreme north and south. The rainy season is linked to the
migratory pattern of the intertropical convergence (ITC), sometimes called the
intertropical discontinuity (ITD), which is associated with the apparent
migratory patterns of the sun (incorporating a time lag of about a month or two).
The climate in the WACAF region is also influenced by factors other than
the ITC, such as atmosphere and oceanic circulation, and land and sea breezes.
However, little is known about their relative influence.
IMPACTS OF CLIMATE CHANGES AND SEA LEVEL RISE
Climate change is defined here as the change in the mean values of climate
variables. Climate variability is defined as the differences between monthly,
seasonal, and annual values of climate parameters and their average values.
Clearly, it is possible for climate to change without becoming more variable,
and it is possible to become more variable without the average condition
changing. Any impact analysis must examine both the long-term climate changes
and the short-term climate variabilities. These must be examined over three
natural time scales: (1) the short-term periods, which range between daily,
weekly, monthly, seasonal, or annual periods; (2) the medium-term scales, which
cover a decade or so; and (3) the long-term scales, which span decades or
centuries (although in the case of nuclear waste sites the assessments span tens
of thousands of years.)
The impacts created by short- and medium-term climate problems have made
the governments and people of the West and Central African regions aware of the
need to examine their own causative role and to fashion appropriate responses.
Droughts and floods in particular have caused so much damage that world attention
has been drawn to the socioeconomic consequences in the WACAF regions,
particularly over the past three decades. Indeed, there is a growing realization
that society is vulnerable.
Ecological and Physical Impacts
The average global rise in temperature is expected to be in the range of
1.5°C to 4.5°C, while sea level rise is expected to be between about 20 and 140
cm. Based on these expectations, it is assumed that both evaporation and
precipitation will increase by about 2 to 3% for each degree of global warming.
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Thus, it is reasonable to expect that both precipitation and evaporation would
increase, possibly between 5 and 20% in the humid, tropical areas of the WACAF
regions, which are already too hot and too wet. The increase in both
precipitation and temperature could have significant environmental impacts. The
increase in average rainfall may be accompanied largely by an increase in the
amount of rain per hour during severe storms and shifts in geographical patterns
of precipitation and cloudiness. However, since the increase in temperature
could increase evaporation and potential evapotranspiration, there would be a
tendency toward more droughts in many, if not most, of these humid, tropical
areas. With the increase in ocean temperatures, tropical storms (e.g.,
hurricanes and thunderstorms) are likely to extend into areas of the region
where they have been less common. Where tropical storms already occur, more
intense winds and rainfall might be expected.
The savanna and semi arid areas of the WACAF region would probably have less
rain, which -- coupled with temperature increases -- would reduce soil moisture
availability (WMO/TD, 1988). Less soil moisture, in turn, would diminish food
production and availability, the availability of water and fuel, and human
settlements.
The rise in sea level that would accompany global climate change would
result in submergence and inundation of the coastal lowland areas. It would also
lead to increased salinity of the estuarine areas and increase the size of the
coastal region.
The ecological and physical implications of climate change include effects
on geological, geomorphological, and hydrological processes, ocean dynamics,
droughts and desertification, and floods and erosion. Decreased precipitation
would lessen the water supply and hydroelectric power generation, while
decreasing the risk of floods. Increased variability could increase the
probability of both floods and droughts.
Forest ecology and the ecosystems would also be affected. For example,
changes in ecological conditions might be less favorable to the existing biota.
Ecosystems would respond by gradually invading the neighboring areas where the
climate is more favorable.
Impacts on Agriculture and Livestock Production and Management
Agriculture and livestock production are the center of life for almost all
the peoples in the region. The climate and soil characteristics determine how
the land is used for agriculture and livestock production, including which crops
are grown.
The impact of climate change and sea level rise on agricultural production
would no doubt be significant, as would the socioeconomic and sociocultural
consequences. For example, decreased rainfall would reduce the production
potential of the crops presently grown in the various ecological zones,
increasing hunger in the region and reducing the incomes of farmers and others
whose occupation depend on farming. In the extreme, unemployment, starvation,
and death could also result. There might also be increased migration to urban
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centers for alterantive employment; and livestock farmers may migrate to other
areas in search of water for their cattle.
Livestock zones are also clearly determined by climate, particularly
rainfall. The cattle zone is essentially determined by distribution of the tse-
tse fly, which so far has made it virtually impossible to keep zebu cattle in
the southern reaches of West Africa. Furthermore, these southern reaches have
been unable to develop mixed farming even though their heavily leached soils
could greatly benefit from animal manure. The north is the main cattle area in
the region primarily because its climate is not hospitable to the tse-tse.
Decreased rainfall and drought would affect livestock production in other
ways. The productivity of existing grassland areas, important for livestock
production, would be reduced. On the other hand, new grazing lands would emerge,
possibly shifting livestock production toward the coast. As with reduced crop
production, income would decline, leading to greater financial stress, which
could threaten economic survival. There would also be significant impacts on
labor, employment, and population distribution.
Along the coasts, where sea level rise may lead to submergence of the
lowland coastal areas (e.g., along the coasts of Senegal and Gambia), much of
the land currently used for agricultural and livestock practices would be lost.
As a result, there would be mass migration out of that area, substantial loss
of income and great financial stress, and unemployment. Large-scale resettlement
would cause additional problems. In a few cases, farmers may be forced to change
their practices. Because most of the coastal environment would be characterized
by water surfaces and their associated ecological systems, converting to
aquaculture may be a viable response (see Everett, Volume 1, Environmental
Implications.)
Impacts on Water Resources and Water Resources Management
Agriculture, industry, and domestic activities depend on water resources.
Unfortunately, a large proportion of the population in the WACAF regions lacks
access to adequate freshwater supplies, especially because of population growth
and rising standards of living which increase water demands.
The changes in the magnitude and timing of water resources would
necessitate changes in management strategies toward greater conservation efforts
in order to balance water supply and demand. In addition, because most of the
water resources along the coast would become polluted by intrusion of saltwater,
water resources management would place greater emphasis on desalinization.
In general, the WACAF regions have five types of water supply systems.
The first category includes areas that depend mainly upon precipitation; unless
storage is available, these systems are only useful during the wet season,
usually six months of the year or less. The second category includes water
supply systems based on river flows that do not store significant amounts of
water for use during periods of deficiency.
The third category of water supply systems is located in coastal areas
where precipitation occurs during most months of the year. The impact of
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decreased regional precipitation on this region may be less than elsewhere since
there would be a general tendency for coastal areas to receive more
precipitation. However, sea level rise may cause floods and saltwater intrusion,
which could contaminate water supplies. This would hurt agriculture and might
even disrupt settlements, with all the consequences discussed in the conference
report section on social and cultural implications.
The fourth category of water supply systems consist of manmade reservoir
systems, which can reduce the effect of intra- and interannual variations in
precipitation and runoff. With reservoirs, water is released when it is required
for agriculture and other purposes. Examples include such manmade lakes as the
Kainji and Akosombo dams. If climate becomes drier, it may be necessary to
curtail releases of water to maintain needed storage capacity for later release.
Water shortages in these reservoirs could have considerable financial
implications and lead to hunger, famine, and death.
The fifth category of water resource systems consists of those based on
groundwater resources. In this case, decreased precipitation would lead lower
water tables and thus increase the difficulty in obtaining water even if the
total amount of water in the aquifer is still sufficient.
Impacts on Other Sectors
Although the impacts on agriculture and water resources are likely to be
the most important, other sectors would also be affected, including fishing,
energy resources, transportation, manufacturing, and construction.
Upwelling fisheries predominate off the southwest coast of the WACAF region.
Increased global temperatures would warm the normally cold upwelling waters,
making them unsuitable for the fisheries and causing a reduction in and possible
collapse of ocean upwelling fishing activities. Tropical warm water fisheries
would be hurt since a rise in temperature would cause a change in the
characteristics of the ocean waters and consequently in the habitat of the fish
currently found in the area. Any significant reduction in the catch would upset
both the economy and culture of the coastal zone. In addition, wetland loss and
increased salinity would reduce estuarine fishing.
Energy supply and demand would also be affected. For example, Critchfield
(1966) notes that the construction of power lines must always take into account
a great number of climate effects on the equipment. Strong gusty winds can down
poles and snap lines, or cause trees and other debris to fall onto the lines.
An increase in the number of thunderstorms would bring more lightning, which
causes at least temporary power failure if it strikes a power line. Temperature
fluctuations can also affect the operation of switches, transformers, and other
equipment. In warmer weather, lines tend to expand and sag; thus they become
susceptible to more damage from strong winds.
Climate change could also have significant impacts on solar energy and
wind, two sources of energy that still remain untapped in the WACAF region.
Submergence of the coastal areas would make the onshore development and
exploration of petroleum more difficult and more expensive.
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However, of more immediate concern are the possible impacts on the supply
and demand of hydroelectric power and fuelwood, which is the most widely used
source of energy in the WACAF region. For example, reduced precipitation would
adversely affect the supply of hydroelectric power, which is very sensitive to
riverflows. There might also be problems related to the seasonal aspect of
riverflows, as well as to the unreliability of rainfall as a source of water
supply in many parts of the WACAF regions. Reduced hydroelectric power
production would impose economic hardships.
The impacts on the supply of fuelwood could also be important. For example,
with a decrease in precipitation, some sources of the fuelwood would be
eliminated. Also, more frequent thunderstorms and erosion could cause more
damage to the forests. With a rising sea, the increased landward penetration
of storms would hurt all but a few (salt-tolerant) tree species, and thus
decrease the area of forests. If climate change leads people to migrate to a
particular area, the increases demand for fuelwood in some areas would aggravate
all the environmental problems commonly associated with deforestation.
There could also be important impacts on energy demand. For example, with
increased temperatures, particularly at night, there would be less demand for
space heat in the WACAF regions and, consequently, less energy consumption.
However, if temperatures were higher during the day, there would be greater
demand for energy to cool buildings.
STRATEGIES FOR AVOIDING OR MITIGATING THE IMPACTS ASSOCIATED WITH CLIMATE CHANGE
The above discussion shows that the impacts of climate change and sea level
rise are likely to be considerable. The question arises: what are the possible
solutions for reducing or, if possible, eliminating the adverse consequences.
In general, there are two categories of strategies: (1) avert or reduce the
magnitude of climate change and (2) mitigate the consequences.
The following measures could be used to avert or reduce the magnitude of
climate change:
Reduce demand for fossil fuels;
Adopt technical solutions to collect or control carbon dioxide; and
Increase biomass production, which includes the reforestation of denuded
areas.
Strategies to reduce demand for fossil fuels involve the use of conservation
measures and alternative sources of energy. This measure is particularly
important for developing areas such as the WACAF regions because the relative
contribution of these areas to the atmospheric gases has been increasing since
1950. Reducing energy demand will reduce burning of fossil fuels. Technical
solutions, which include the use of mechanisms to control atmospheric
concentrations of carbon dioxide, are linked to world, regional, and national
energy policies, forest management, and personal and societal values. Such
solutions include measures to control the production and use of coal and
petroleum and measures to control emissions from power plants or those occurring
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at the point of combustion. The adoption of such measures, however, could
require complete sociocultural change.
Increasing biomass production through afforestation will provide a natural
sink that will absorb carbon dioxide. Cooper, for example, noted that an
increase of only 1% in the plant life on earth, especially forests, would be
sufficient to absorb one year's release of carbon dioxide at the present rate
(Kellogg and Schware, 1982). In tropical areas in general, and in the WACAF
regions in particular, there is a great need to reduce the rate of deforestation
and to reforest deforested areas. However, it is important to note that
reforestation implies ecological changes, which in turn may have climate
consequences. Marchetti (1979) has pointed out that a change in vegetation
patterns could offset the intended cooling by absorbing more solar radiation,
thus warming the earth.
Strategies for mitigating the consequences of climate change include those
that would help to increase human resilience to the effects. Such strategies
include protecting arable soil, improving water resources management, applying
agrotechnology, improving land-use policies, maintaining food reserves, and
adopting disaster response measures.
In the WACAF regions, there has been a tremendous loss of arable soil
through soil erosion and salinization in recent years, and this trend would
probably persist with climate change and sea level rise. Largely responsible
for this loss are poor agricultural management practices such as overgrazing.
Improving water resources management, for example, through effective management
of dams, aqueducts, reservoirs, irrigation systems, and diverted rivers, would
ensure adequate and reliable water supply in the event of drought and water
deficiency.
Another effective measure would be to develop agrotechnologies such as more
efficient irrigation systems, saltwater crops, and new forms of nitrogen-fixing
plants. Improved coastal land-use policies would also be important and should
be considered in sociocultural planning for mitigating the consequences of sea
level rise.
Maintenance of food reserves and adoption of provisions for disaster relief
now being promoted by international organizations to help the countries adversely
affected by the recent climate variations, also could help to mitigate
sociocultural impacts. The WACAF regions, like any other part of the world,
require a reliable food supply; since any variation or change in climate and
consequent sea level rise could adversely affect food production in the region,
it would be prudent to develop adequate food reserves.
Other strategies for mitigating the effects of climate change and sea level
rise involve access to information and technology, which can lead to better
decisionmaking regarding how best to respond to potential climate change.
Examples of such strategies include the use of environmental monitoring and
warning systems, the collection and use of improved data, public information and
education, and the transfer of technology.
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CONCLUSION
Climate change and sea level rise would have considerable Implications on
human cultural systems. We need to plan and Implement the measures necessary
to either avert or mitigate the consequences. It is important to note, however,
that usually the sufferer of the consequences sees the causes and effects of the
problem as wholly local, and thus thinks only of local solutions. However, to
effectively plan and implement solutions to the problems that could result from
climate changes, it is important for local people to base their response
decisions on a larger world view.
We need to ensure that solutions are carried out on world, regional,
national, and local scales. For the WACAF region, in particular, it is important
that cooperation, collaboration, and coordinated efforts occur at the regional
and local levels as well as at the national and international levels. To this
end, national governments must be ready to do their part as appropriate, for
example, by ensuring that their national observing and communication systems
function efficiently, and doing more to protect the coastal environment.
Scientists, planners, and policymakers must promote research, provide improved
access to data and information necessary for effective planning and
implementation, prudently use data and information, and support effective public
participation in planning and implementation of measures to avert or mitigate
the consequences of climate change and sea level rise.
BIBLIOGRAPHY
Critchfield, H.J. 1966. General Climatology. Englewood Cliffs, NJ: Prentice
Hall.
Flohn, H. 1979. A scenario of possible future climates -- natural and man-
made. In: Proceedings of World Climate Conference. WMO No. 537. Geneva:
World Meterorological Organization, pp. 243-268.
Kellogg, W.W., and R. Schware. 1982. Climate and Society: Consequences of
Increasing Atmospheric Carbon Dioxide. Boulder, CO: Westview Press.
Marchetti, C. 1977. On geoengineering and the C02 problem. Climate Change
1:59-68.
Maunder, W.J. 1970. The Value of Weather. London: Meuthen.
Ramanathan, V. 1980. Climatic effects of anthropogenic trace gases. In:
Interactional of Energy and Climatic. W. Bach, J. Bankrath and J. Williams,
eds. Dordrecht, Netherlands: Reidel.
Rotty, R.M. 1979. Energy demand and global climate change. In: Man's Impact
on Climate. W. Bach, J. Pankrath, and W.W. Kellogg, eds. Developments in
Atmospheric Science 10. Amsterdam: Elsevier, pp. 269-283.
WMO. 1979. World Meteorological Organization. Proceedings of World Climate
Conference. WMO, No. 537. Geneva: World Meteorological Organization.
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WCP. 1986. Report of the International Conference on the Assessment of the Role
of Carbon Dioxide and Other Greenhouse Gases on Climatic Variations and
Associated Impacts. WMO, No. 661. Geneva; World Meteorological Organization.
Ill
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MEDITERRANEAN
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IMPACTS OF GLOBAL CLIMATE CHANGE IN THE
MEDITERRANEAN REGION: RESPONSES AND POLICY OPTIONS
G. SESTINI
Applied Earth Science Consultant
Via Delia Robbia 24
50132 Florence, Italy
ABSTRACT
Global climate change is likely to have two major types of negative impacts
on the Mediterranean region: (1) changes of precipitation and soil moisture,
which will affect water resources, riverflows, irrigation systems, and
agriculture; and (2) sea level rise, which will exacerbate coastal erosion and
flooding with repercussions on tourism, settlements, communications, and ports.
To minimize the adverse impacts of climate change, analyses of these impacts
should be incorporated into the planning of new projects and activities along
the coast.
In most Mediterranean countries, the use of the coastal zone has increased,
especially for agriculture and tourism. Unfortunately, development has
progressed in a haphazard way, with little planning or consideration of
environmental impacts. This present state of environmental degradation will
exacerbate sea level rise impacts.
The large amount of capital investment along the coasts suggests that
protective measures will be desired, even though they may not be feasible in many
cases; thus, the cost of protection will greatly escalate and difficult political
decisions will have to be made concerning when, where, and how the coast should
be protected.
In the meantime, preparation is imperative through increased awareness,
analysis, regional planning efforts, and regulation in the face of unhindered
development based on short-term profitability.
INTRODUCTION
The impact of climate change on soils, hydrology, vegetation, and on two
Mediterranean deltaic regions was first evaluated at the European Workshop on
Interrelated Bioclimatic and Land Use Changes, in the Netherlands, October 1987
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(Imeson et al., 1987; Sestini, 1989). The consequences of temperature and sea
level rise for the coastal areas were further examined in 1988 by a United
Nations Environment Programme (UNEP) task team of experts in Split, Yugoslavia,
which attempted to forecast changes of climate, sea level, hydrology, ocean
circulation, marine ecosystems, and vegetation (Sestini et al., 1989, for a
review), as well as socioeconomic changes (Baric and Gasparovic, 1989). Six
case studies have evaluated impacts on major deltaic areas (Georgas and
Perissoratis, 1989; Corre, 1989; Marino, 1989; Sestini, 1989a,b; Hollis, 1989).
The conclusions with regard to climate variables were that doubled C02 would
result in a temperature increase of 1.5 to 3.5°C; evaporation increases of 15-
20%; a possible northward shift of the areas of cyclonic activity, with a
probability of a precipitation decrease in the southern half of the
Mediterranean; and magnification of interannual variability, with more frequent
occurrence of extreme conditions (e.g., heat waves, droughts) (Wigley, 1989).
Soils would be affected in their physiochemical structures, particularly
where rainfall is <500 mm/year, with greater salinization and reduction in
organic matter. Soil erosion would increase. Higher temperatures would cause
a northward and upward shift of vegetation zones, changes in forest composition,
and greater incidence of forest fires; desertification would increase in the
marginal areas of limited rainfall. Agriculture might be affected by changed
water supplies, decreased soil fertility, and especially by the greater incidence
of extreme events. Lagoons and salt marsh ecosystems might change as a
consequence of greater temperature and salinity fluctuations, with water
stratification phenomena becoming more frequent.
A discussion at the September 1987 UNEP Conference in Norwich, England, on
the type and magnitude of changes in sea level produced an estimate that sea
level will rise 14-22 cm by 2030, 25-40 cm by 2050, and perhaps up to 1 meter
by the end of the 21st century (Raper et al., 1990). Nevertheless, the behavior
of some of the causal variables (e.g., oceanic thermal expansion and the melting
of polar ice) are more uncertain than these estimates would lead one to believe.
The Mediterranean study also emphasized that (at least in some countries)
the pressure on the environment from rapid population growth would far outweigh
the impact of climate change (Baric and Gasparovic, 1989).
Two principal effects of climate change stand out for their far-reaching
consequences and require urgent attention from both scientists and policy makers:
1. Coastal instability due to sea level rise, and its attendant negative
consequences for lowlands and wetlands, maritime cities, and harbors
(e.g., for lagoonal fishing, reclaimed land agriculture, beach tourism,
industries, and communications); and
2. Precipitation and soil changes and their consequences for slope
stability, for surface and subsurface waters, and stream and irrigation
systems (e.g., for the management of hydropower, irrigation, drinking
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Sestini
and industrial water supplies, inland navigation, and waste disposal
systems, especially in a situation of growing water pollution).
THE PROBLEMS OF IMPACT ASSESSMENT
The complex, interrelated nature of the physical-biological systems and the
present and future population and economic patterns of the coasts and alluvial
plains (Figure 1) makes assessing the impacts of climate change and sea level
rise difficult.
The physical impact of sea level rise on low-lying coasts can be predicted,
even modeled quantitatively, on the basis of the present parameters of
morphology, hydrodynamics, sediment budgets, land subsidence, and the effects
of artificial structures. Likewise, the impacts of altered rainfall distribution
on surface and groundwater can be modeled, and the effects of increased air
temperatures and changed soil-water parameters on biosystems can be estimated
at least qualitatively. What is more difficult to quantify, however, is the
impact of these physical and biological changes on the future socioeconomic
framework of the threatened coastal zones.
Future organization of these regions (Figure 2) depends on an evaluation of
the present and future state of the environment; on the side effects of large
construction projects with a life of decades; on the necessity to protect
unmovable assets such as historical cities, harbors, and industrial centers; and
also on the possibility of abandoning threatened areas and/or the redeployment
of land uses.
Evaluation of economic impacts must consider not only the present function
and value of land uses in the context of local needs and of the importance of
the lowland concerned to its hinterland and farther, but also future land
functions and values. The primary needs are determined by the present level of
population and its trends of growth or decline, by the wider economic role of
the region, and by external market forces. Some economic activities and land
uses cannot be projected into the future because they are interrelated with
"external" -- economic, social, and political -- factors and therefore can evolve
independently of local conditions (Figure 2). For instance, the future relevance
of local industries, agriculture, and ports will largely depend on worldwide
commodity prices and trade trends such as those related to mineral and energy
raw materials (with their effects on heavy and chemical industries) and to
cereals and industrial crops; and on the demand for consumer goods in a
competitive, exchange-oriented international society.
The role of ports may change in response to altered trends of maritime trade
(e.g., the Suez Canal after a decline of petroleum transport), and local markets
for consumer goods and services could vary in relation to stagnating or reduced
urban growth resulting from shortages and pollution of surface and ground waters.
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00
I HIGHER TEMPERATURES I
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SEA WATER
TEMP.
SALINITY
CURRENTS
SURFACE WATERS
AQUIFERS RECHARGE
POPULATION, SETTLEMENTS
AND
SOCIO-ECONOMIC WELLBEIN6
PROJECTED
TEMPERATURE
AND
SEA LEVEL RISE
LONG TERM PLANNING
AND
INVESTMENTS
INTERNAL
SYSTEMS TRENDS
t
NATURAL
MANIPULATED
ASSESSMENT
OF FUTURE IMPACTS
LAND « RESOURCES USES
PROJECTED
ECONOMIC REQUIREMENTS
PROJECTED POPULATION PRESSURE
PRESENT STATE
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ENVIRONMENT
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AND INVESTMENTS
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NEW APPROACHES
Figure 1.
Some of the variables affecting the assessment
of the impacts of future climatic changes.
Figure 2. The interrelated nature of
physical and biological systems.
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Sestini
THE IMPACT OF SEA LEVEL RISE
Much of the 46,000-km-long Mediterranean coastline rises quickly from the
sea. There are many alluvial and coastal plains, but each is fairly small.
Nevertheless, they have been important since ancient times as communication
pathways for the interior. Deltas have been generally advancing in the past
centuries (despite a 1- to 2-mm sea level rise and local geological subsidence),
and until early in this century (or a few decades ago in some countries), they
were in a fairly natural state with extensive lagoons and marshes.
Today, all coastal plains are intensively used for agriculture, often on
lands reclaimed from wetlands, with active fishing and aquaculture in the
lagoons. Industrial centers and harbors have been established in some areas
(e.g., Ravenna and Porto Marghera, Venice, Italy; Fos de Mer by the Rhone Delta
in France; and Abuqir-El Taba by Alexandria, Damietta, and Port Said in Egypt).
Considerable portions of the Mediterranean coastlines have become more and more
intensively exploited for beach recreation at the edges of coastal plains or
between cliffed shores. In fact, in the northern Mediterranean, practically all
beaches are presently used (utilization ranges from as low as 25% of total
coastline in Yugoslavia to as high as 75% in north Italy and eastern Spain).
Tourism development has involved construction of hotels, apartments, pleasure
boat harbors, and related permanent infrastructures and services. Some resorts
have become very urbanized (high rises), and old towns have expanded with an
increase in resident year-round population. Undoubtedly, all these activities
and settlements would be the first to be threatened by a rising sea level.
Coastal settlements, from villages to cities, are numerous. However, with
a few notable exceptions (e.g., Venice, Siracusa), most major cities have only
small portions at sea level with exposed seaside boulevards and some residential
quarters at an elevation of 1 meter or less (e.g., Barcelona, Nice, Marseilles,
Genoa, Naples, Ancona, Algiers, Pyreus, Alexandria).
The effects of sea level rise must be considered in conjunction with the
degree of exposure to storm waves and surges that aggravate coastal erosion with
seaward removal of sand, direct attack, or overtopping (with flooding) of
seawalls and dikes. The degree of exposure to wave energy varies with coastal
orientation in relation to waves (Figure 3). Storms with high waves (2-6 m) are
generated in the western Mediterranean (and to a lesser extent in the central
basin) causing wave paths to the northwest, west, and northeast (in the west and
in the Adriatic Sea), and to the southeast in the eastern Mediterranean. The
cold and violent winds that blow in winter from the north and northeast (mistral,
bora, etc.) generate waves that attack the Algerian-Tunisian, Sardinian, west
Adriatic, central Aegean, and Nile Delta coasts. All other lowlands and cities
are more sheltered (e.g., Albania, Turkey, northern Greece) and suffer from a
smaller degree of storm wave impact.
Low sandy coasts still in a fairly natural state would probably retreat
gradually in response to beach profile readjustment (Bruun and Schwarz, 1985)
with some periodic flooding. The breakup of barrier islands and breaching of
beach/dune ridges would occur where exposure to storm waves is accompanied by
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Mediterranean
Figure 3. Main deltaic-alluvial lowlands of the Mediterranean region (arrows
indicate the predominant directions of winter storm waves).
natural (in some cases also manmade) subsidence or where the coastal sand budget
is low or negative. Undoubtedly, well developed, thick ribbons of coastal sand
can survive sea level rise, as indicated by the relic dune and beach ridges on
the Continental Shelf of the Adriatic Sea and Nile Delta.
Wetlands can move landward and grow upward if the rate of sea level rise is
low. However, the persistence of brackish lagoons and marshes would depend on
the integrity of the barrier islands, while their ability to move landward is,
in fact, generally impeded by dikes, roads, and other structures.
Many stretches of the Mediterranean coasts are, however, no longer in a
natural state. Many shores are retreating because dams have sharply reduced (or
eliminated) the ability of rivers to supply sand to the coast (Figure 4), or
because people are mining the sand in river beds. In addition, dunes have been
flattened to make room for beach resorts. The natural beach fluctuations and
coast-parallel sand movements are impaired by fixed defense structures, as well
as by the jetties that protect the entrances of estuaries, lagoon outlets,
canals, and ports.
The most heavily fortified lowland coasts are in the west Gulf of Lions, on
the Tyrrhenian and Adriatic side of northcentral Italy, and in parts of Greece
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Sestini
and northern Tunisia. The other lowland coasts (e.g., Turkey, Albania) have
fewer coastal protection structures; continued shore erosion in conjunction with
increased use of the coast will gradually motivate other coastal areas to begin
employing these devices as well, as in the Nile Delta. From a local perspective,
these measures are justified to stabilize harbor accesses and to protect beach
investments; but when one considers the impacts that protecting one area can have
on other areas, the wisdom of these measures is not as obvious. All too often,
people fail to sufficiently consider the future effects of hard structures on
sediment-starved coasts (e.g., the dikes built at the retreating Rosetta and
Damietta headlands in the Nile Delta will eventually weaken the lagoon barriers
to the east).
A 25- to 30-cm sea level rise would not flood most Mediterranean lowlands,
but it would worsen the present situation of beach, delta, and lagoonal
instability. Water levels in lagoons, estuaries, and canals would be higher,
especially in areas already facing land subsidence (e.g., the Adriatic coast).
There would be increased salinity in the lagoons, more extended salt wedges in
rivers, and further salinization of reclaimed lands. All protective structures
(breakwaters, seawalls, dikes) would have to be raised periodically, and beach
nourishment schemes would have to be intensified. The cost of beach and urban
seaside protection will threaten the economic viability of some beach resorts
and small towns.
• Cities <1 m elevation,* surrounded by water
Cities mostly >2 m, with parts <1 m (iniharboura)
(fein SLR impact on port/shoreline infrastructures
Figure 4. Mediterranean cities that would be most threatened by sea level rise
in association with storm surges. Also shown are the main river systems that
are dammed.
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A further rise of 30-100 centimeters would have catastrophic effects, unless
measures of artificial protection measures are implemented in advance (e.g.,
raising and stabilizing dunes, erecting more seawalls, and blocking
canals/estuaries and lagoonal entrances with sluice systems). Recreational
beaches would continue to exist (along coastal plains if not along cliffed
coasts), but existing seaside resorts and exposed cities would suffer extensive
damage. Higher water levels in the northern Adriatic lagoons would cause the
gradual decline of several historical and commercial centers; these impacts could
be further exacerbated by other human activities such as withdrawing groundwater.
The socioeconomic impact of sea level rise on coastal lowlands will vary
because the degree of land use and development varies -- both in absolute terms
and in comparison with nationwide averages (e.g., the Ebro and south Turkey
Deltas are relatively undeveloped as compared with the Nile Delta, which contains
45% of Egypt's population). Few people live below the 1-m contour, even in the
generally overcrowded Nile Delta. Populations are usually concentrated on ground
more than 2 m above sea level, especially on the raised present or past alluvial
channels. But there are exceptions, including Venice, and new recreational and
port/industrial centers. Moreover, land use will become more intensive because
of population growth (probably 550 million by 2025, as compared with 350 million
in the Mediterranean countries today), and increased tourism (213 million a year
in 1984, perhaps doubling by 2025) (UNEP, 1987). Recent urbanization on coasts
has been and will continue to be focused on all available flat ground near the
sea.
In the southeastern Mediterranean countries, populations will grow faster
and coastal areas will continue to provide focal points for development, mainly
in the vicinity of cities. In North Africa, the nature and extent of the
economic consequence of sea level rise will depend on the degree and type of
coastal development during the next 2-3 decades. In Egypt, for instance, the
economic consequences will depend on the uses made of the coastal lagoons (i.e.,
land reclamation, fishing, or freshwater storage).
In conclusion, the most serious negative consequences for coastal (in some
cases national) economies would be the physical impacts on (1) tourist beaches
and infrastructure; (2) pleasure marinas; (3) coastal protection structures; (4)
towns and cities by the sea, seaside boulevards, and residential areas subject
to washovers; (5) ports and industrial installations, especially those built on
lowlands and in lagoonal areas; (6) roads, railways, airports by the sea; (7)
lagoonal fishing; and (8) reclaimed lands and relative irrigation systems.
RESPONSES AND POLICIES FOR ACTION
Responses to rising sea level would vary from (1) extensive artificial
protection, to (2) altered land use (e.g., less urbanized tourist beach centers,
the return of some agricultural reclaimed lands back to their lagoonal state),
to (3) abandonment. Because the Mediterranean coast is diverse, no single
solution is likely.
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Sestini
Nevertheless, the intensity of development and the economic value of coastal
activities suggest that abandonment will be confined to isolated localities;
however, in many places, public and private investments might gradually become
economically unviable as increased physical damages make maintenance too costly
(e.g., polders, infrastructures, tourist harbors, power stations by the sea).
The Mediterranean coast already has a high degree of coastal defense in many
areas; the large number of unmovable features (cities, ports, valuable
agriculture, etc.) would make abandonment expensive. But the escalating costs
of protection would impose major burdens on state and local governmental budgets,
perhaps taking up a large percentage of the income generated by coastal
economies.
The maintenance of beach recreation facilities requires a more practical and
rational approach than that of today. Is the vision of total protection held
by local residents, private investors, and politicians practical in the long run,
given the natural processes involved? The present state of degradation caused
by the very activities to be protected suggest that it is not. It may be
unrealistic to continue occupying a retreating sandy shoreline by maintaining
the existing defense structures. A more rational approach would be to establish
setback lines and zoning, with less urbanized settlements, and to adopt more
"open-space" tourism, wherever feasible, based on the model of the Camargue in
the Rhone Delta (Corre, 1989).
With a few notable exceptions of good regional planning (e.g., Gulf of
Lion), coastal exploitation has been a local or private investment venture (often
with political backing), whereas the ownership and responsibility for coastal
use usually are with the state, which has to pay for protection and for the
damages caused by natural hazards.
In the face of rising costs of protection, it may be necessary for nations
to adopt the approach that coastal investments, if carried out with no
consideration for environmental impact, must be accepted as "high risk," and the
consequences are to be borne by the investors themselves. (See papers in this
volume for a discussion of this principle. The concept is parallel with the
spreading attitude and burgeoning legislation that industrial-urban-agricultural
polluters must pay for degrading and redressing the environment.)
Given the continued uncertainty about the timing and magnitudes of sea level
rise, determining which policies ought to be implemented now is difficult. A
low level of awareness persists on the part of the public and authorities alike
concerning the consequences of climate change and the seriousness of -- and the
need to address -- the present state of coastal degradation.
It would also seem to be reasonable that countries where the coastal zone
is still mostly undeveloped should look at the consequences of failing to conduct
impact assessments, which can be seen in most nations with heavily managed
coasts.
Response strategies will depend on the degree of local impact, physical and
financial, according to present and projected land and water resource uses.
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Mediterranean
Impacts have, by and large, yet to be evaluated because data bases are, In many
cases, limited or nonexistent.
Strategies imply long-term planning based on interdisciplinary approaches.
Policy decisions based on these strategies will require political insight and
the will to carry out and implement them; that is, they will require a high
degree of centralized decision -- in the rather tight timeframe of just a few
decades. Even the first stage, that of deciding upon and implementing a phase
of rational studies (i.e., to create institutes and/or to coordinate existing
ones for environmental impact assessment and planning), is no light task in
countries where responsibility for environmental matters is dispersed among
different ministries, local authorities, universities, and national research
centers.
BIBLIOGRAPHY
Baric, A. and F. Gasparovic. 1989. "Implications of climatic changes for the
socio-economic activities in the Mediterranean coastal zone." UNEP/OCA, Nairobi,
Rept. WG 2/12.
Brunn, P. and M.L. Schwartz. 1985. "Analytical prediction of beach profile
change in response to a sea level rise." Zeitschr. fur Geomorphologi, Suppl.
Bd. 57: 33-55.
Corre, J.J. 1989. "Implications of climatic changes for the Gulf of Lion."
UNEP, Nairobi, Rept. WG 2/4E.
Georgas, D. and C. Perissoratis. 1989. "Implications of climatic changes for
the inner Thermaikos Gulf." UNEP/OCA, Nairobi, Rept. WG 2/9.
Hollis, G.E. 1989. "Implications of climatic changes for the Garaet Ichkeul
and Lac Bizerte." UNEP/OCA, Nairobi, Rept. WG 2/a.
Imeson, A., H. Dumont, and S. Sekliziotis. 1987. "Impact analysis of climatic
change in the Mediterranean region." European Workshop on Interrelated Biocli-
matic Changes, Norwijkerhout Oct. 1987, v.F.
Marino, M.G. 1989. "Implications of climatic changes on the Ebro delta, Spain.
UNEP/OCA, Nairobi, Rept. WG 2/3.
Raper, S.C.B., R.A. Warrick, and T.M.L. Wigley. 1990. Global Sea Level Rise.
In: Milliman, D.J. (ed.) Rising Sea Levels and Subsiding Coastal Areas.:
SCOPE, Bangkok, Nov. 1988 Seminar (in preparation).
Sestini, G. 1989a. "The implications of climatic changes for the Po delta and
Venice lagoon." UNEP/OCA, Nairobi, Rept. WG 2/11.
Sestini, G. 19895. "The implications of climatic change for the Nile delta."
UNEP/OCA, Nairobi, Rept. WG 2/14.
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Sestini, G., L. Jeftic, and J.D. Milliman. 1989. "Implications of expected
climatic changes in the Mediterranean region: An overview." UNEP Regional Seas
Reports and Studies, No. 103, UNEP, Nairobi.
Sestini, G. 1990. The impact of climatic change on two deltaic lowlands of the
Eastern Mediterranean. In: Jelgersma S. (ed.) Sea Level Rise and European
Coastal Lowlands. Basil Blackwell (in press).
UNEP, 1988. The Blue Plan, Futures of the Mediterranean Basin. Executive
Summary and Suggestions for Action. Sophia Antipolis, France.
Wigley, T.M.L. 1989. Future climate of the Mediterranean Basin with particular
emphasis on changes in precipitation. UNEP/OCA, Nairobi, Rept. G WG/2/6.
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IMPACTS OF CLIMATE CHANGE ON THE
SOCIOECONOMIC STRUCTURE AND ACTIVITIES
IN THE MEDITERRANEAN REGION
ANTE BARIC
Institute of Oceanography and Fisheries
Split, Yugoslavia
ABSTRACT
This paper examines the possible impacts of climate change on the
Mediterranean coastal areas, focusing special attention on human settlements and
major economic sectors (agriculture, tourism, fisheries, and aquaculture).
Society's activities depend closely on the existing climate. One can assume
that the impact on activities and institutions will be primarily local, with
possible important common characteristics for small and large areas or regions.
However, the assessment of local impacts is outside the scope of this paper owing
to our lack of knowledge on the particular circumstances facing other regions.
Climate change will have a limited impact on the distribution and dynamics
of coastal populations. The natural population growth will not be affected by
climate changes and will continue to follow the present general trends -- i.e.,
little natural population growth in the northern Mediterranean countries, with
high growth rates for nations along the southern and eastern coasts. The current
rate of migration toward the coast will probably not change, although it could
accelerate in the south owing to the natural spreading of the deserts.
Approximately 5 percent of the population living in coastal zones will be
indirectly affected by the impacts of climate changes and sea level rise; about
one percent reside in areas that would be inundated by a rise in sea level.
An inherent quality of most institutions is a certain inertness in response
to phenomena that are not expected for decades. However, because these changes
could begin to occur as soon as the next decade, the governments and the public
should begin preparing for them today.
The nations of the world should incorporate the mitigation of climate change
into national development and environmental management. This calls for (1)
alerting the public (avoiding unnecessary alarm) and all administrative and
economic institutions involved in the decision-making process about the possible
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Mediterranean
effects of the climate changes; (2) studying the local conditions under which
these changes will occur; (3) incorporating the implications of climate changes
into the integrated planning process for global development and development of
individual economic activities; (4) undertaking appropriate cost-benefit and
environmental impact analyses within land-use, environmental, and town planning
and management; and (5) promoting and developing new technologies for mitigating
the impacts of climate change.
Responding to climate change will require considerable funds, which should
be anticipated in national, regional, and local plans.
INTRODUCTION
It is no exaggeration to say that climate largely determines the basis of
all human activities. Directly and indirectly, climate affects soils,
vegetation, water resources, storminess, and most other environmental conditions,
which in turn help to determine our productive pursuits and the very institutions
by which society organizes itself.
Thus a change in climate would affect the social and economic structures
of the entire world in ways that we cannot yet predict. Would the changes be
sudden or gradual? Should we view the worldwide impact as simply the sum of all
local impacts, or must the socioeconomic impacts -- like the geophysical
processes -- be viewed in a global context? Both approaches yield important
insights, although predicting regional and local impacts is impossible unless
someone has become truly familiar with a particular area.
Reducing the impacts of climate change in the next century will be
expensive. New investments will be required for coastal defense and supplying
sufficient water to agricultural areas, or for relocating people should such
engineering projects be too costly. The need for new investments may affect
developing nations in the eastern and southern Mediterranean region particularly
severely. New strategies will be necessary for development, technology, and
environmental protection.
The changes brought about by the greenhouse effect are chronic, while the
sociopolitical and economic institutions react only to existing and impending
emergencies. Because the complex network of institutions need 20 to 50 years
to adapt, the planning should already be under way. In this paper, we attempt
to evaluate the adaptability of the socioeconomic activities to a change in
climate.
BACKGROUND INFORMATION ABOUT THE MEDITERRANEAN REGION
Although the coastal zones of the Mediterranean countries represent only
17% of the total area of the countries (Blue Plan, 1988), they are a primary
focus in assessments of climate changes, given the risk of a rise in sea level.
The 46,000 kilometer Mediterranean coast is very ragged and indented. More
than half of it is rocky, while the rest is considered to be sedimentary (see
Table 1). About 75% of the coastline belongs to four countries:
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Table 1. Selected Data for the Mediterranean Coastal Zones
ro
vo
Country
Urbanized
coastal zones
(sq. km)
Population
in coastal
zones (1,000's)
Percentage
of coastal
population
in urban areas
Population/km
of coast
Length of coastal
shoreline (km)
total islands
Spain
France
Monaco
Italy
Malta
Yugoslavia
Albania
Greece
Turkey
Cyrus
Syria
Lebanon
Israel
Egypt
Libya
Tunisia
Algeria
Morocco
2,794
1,203
2
4,981
13
351
52
1,315
371
20
17
86
154
236
85
168
276
91
13,860
5,496
27
41,829
383
2,582
3,050
8,862
10,000
669
1,155
1,668
2,886
16,511
2,284
4,965
11,500
3,390
80.64
87.52
100.00
66.76
85.38
54.38
34.10
59.37
53.00
49.48
35.93
80.15
90.35
35.73
62.17
67.47
48.00
44.89
5,372
3,227
6,750
5,260
2,128
422
7,297
591
1,926
855
6,311
11,867
21,250
17,300
1,290
3,819
9,583
6,621
2,500
1,703
4
7,953
180
6,116
418
15,000
5,191
789
183
225
200
950
1,770
1,300
1,200
51
910
82
--
3,766
--
4,024
--
7,700
--
--
--
--
--
--
--
--
--
— ~
00
Q)
-5
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Mediterranean
Greece, Yugoslavia, Italy, and Turkey. The islands in three of these countries
account for roughly 40% of the Mediterranean coast: Greece, 7,700 km;
Yugoslavia, 4,024 km; and Italy, 3,766 km (Blue Plan, 1987).
Approximately 133 million people live in coastal zones, representing 37%
of the total population of the Mediterranean countries. About 87 million people
live in the coastal cities. The gross national product in the region ranges from
about $700 to $10,000 (U.S.) per capita (Blue Plan, 1988). The distribution of
gross domestic product varies among the countries (Table 2). For example,
agriculture's contribution ranges from 2% in Libya up to 20% in Syria and Egypt;
industry's contribution ranges from 24% in Libya up to 69% in Syria.
IMPACT OF CLIMATE CHANGE ON SELECTED ECONOMIC ACTIVITIES
Agriculture
Agricultural production in the Mediterranean countries is generally oriented
toward food, although a few countries also produce tobacco and cotton.
Cultivated land is less than 50% of the total area of each country; in north
African countries, it is always less than 10%. In recent times Mediterranean
agricultural regions have generally remained unchanged, although in Italy and
France the total cultivated land has declined (Blue Plan, 1988).
In the northern Mediterranean countries and Turkey, most agriculture is
removed from the coast, although the high fertility of coastal soils makes the
coastal zone highly productive. By contrast, in the eastern and southern
Mediterranean countries, production is concentrated in the coastal zone. In
Egypt, agriculture is found both in the Nile Delta and inland along the Nile
River.
The expected climate changes in the Mediterranean region (Wigley, 1988)
could have very far-reaching consequences on agriculture. Sea level rise will
inundate some areas and lead to salinization of others. Other factors could also
be important, such as higher temperatures and changes in the amount and
distribution of precipitation.
Lengthening of the summer dry period may affect the existence of crops or
plantations, the incomes of farmers, and the commercial values of products.
Rising temperatures will change growth cycles, harvest times, and the quality
of produce; for example, as spring comes earlier in northern Europe, the need
for early fruits and vegetables produced in the Mediterranean will decrease.
Warmer temperatures will also have indirect effects, such as increased
evaporation, lower moisture levels of the soil, and increased erosion.
Most plants require the greatest amounts of water during the spring or
summer, which is the period of least precipitation in the Mediterranean. The
absence of showers in late spring or early summer may significantly reduce
productivity or necessitate increased irrigation. At the same time, warmer
temperatures will increase water requirements for plants. Wherever possible,
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Table 2. Distribution of Gross Domestic Product (%)
co
Country
Spain
France
Italy
Yugoslavia
Greece
Turkey
Syria
Israel
Egypt
Libya
Tunisia
Algeria
Morocco
1960
21
9
15
24
23
41
25
11
30
14
24
21
29
Agriculture
1976 1980
9
6
8
15
18
29
17
8
29
3
21
7
21
8
4
6
12
16
23
20
5
23
2
17
6
18
1984
6a
4
5
15
18
19
20
5
20
2
15
6
17
1960
39
48
38
45
26
21
21
32
24
9
18
24
24
Industry
1976 1980
39
43
41
43
31
28
36
43
30
68
30
57
31
37
36
43
43
32
30
27
36
35
72
35
57
32
1984
34a
34
40
46
29
33
24
27
33
64
35
53
32
1960
40
43
47
31
31
38
24
57
46
77
58
55
47
Services
1976 1980
52
51
51
42
51
43
47
49
41
29
49
36
48
55
60
51
45
52
47
53
59
42
26
48
37
50
1984
60a
62
55
40
53
47
57
68
48
34
50
41
51
1982
Source: World Bank, World Development Reports.
00
-J
_d.
o
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Mediterranean
it will be necessary to use closed systems of water distribution and ways of
supplying water, which will minimize evaporation; it may also be necessary to
reuse wastewaters.
Temperature rise may also significantly affect the development of various
parasites and insects, which may directly affect agricultural productivity and
income.
The investments required for coastal defense, dams, and irrigation systems
will make agricultural production much more expensive, which could have far-
reaching socioeconomic consequences. The rich northern Mediterranean countries
should be able to solve these problems. But the poorer countries in the south,
which even today have problems with supplying their inhabitants with food, will
have more difficulty coping.
Tourism
The Mediterranean is by far the strongest tourist region in the world. For
over 30% of the tourists that vacation outside their own country, their final
destination is one or more of the Mediterranean countries. In 1984, about 100
million people visited the Mediterranean,1 of these, 45 million were domestic
tourists. Although France, Spain, and Italy are the most popular destinations,
tourism is an important part of the coastal economy throughout the region.
Mediterranean tourism is primarily oriented toward swimming and sunbathing -
- activities that directly use the seashore.2 Therefore, the immediate coast,
its slope, climate,3 and the quality of land and sea are of prime importance.
Most tourist facilities, such as hotels, camps, and youth hostels, are located
within 200-300 m of the coast. Facilities farther from the shore are found
mainly in the developed and luxurious tourist areas.
Tourism will suffer from climate change. Beaches that lie below cliffs and
other rocky inclines would be first to disappear. There would also be problems
with beaches where infrastructure is within a few meters of the high water mark.
It may be necessary to relocate city streets and promenades (e.g., Nice, Cannes)
1 This number is probably too low, since most of the countries do not
accurately register their domestic tourists (Blue Plan, 1988).
2 Mediterranean tourism fluctuates seasonally. Depending on location, the
number of visitors from June to September is from 50% to 80% greater than other
periods of the year.
3 Mediterranean tourism fluctuates seasonally. Depending on location, the
number of visitors from June to September is from 50% to 80% greater than during
other periods of the year.
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Baric
or highways and railway lines (the coastal stretch between Nice and Cannes, and
parts of the Italian and Yugoslav coasts).
Even if sea level rises moderately and does not threaten tourist facilities,
the loss of beaches would disappear or require substantial investments for
reconstruction. Moreover, saltwater intrusion due to sea level rise and
increased evaporation from higher temperatures would diminish the availability
of water needed for tourism and wastewater drainage. Islands may experience even
greater damages than the coast of the mainland.
A special type of tourism, nautical tourism, has stimulated the building
of a large number of marinas, sport harbors, and berths. They will be much
harder hit than the large freight harbors.
Global warming may lengthen the tourist season in the northern Mediterranean
by creating more favorable weather. However, the rise in air temperature and
sea level may enhance the attractiveness of the continental lakes and of the
coastal tourist areas of other seas (e.g., Baltic, North Sea), thus negating the
need for many northern Europeans to travel south for their vacations.
Any attempts to relieve the impacts of climate changes on tourism will
encounter great organizational and financial difficulties. The industry has a
great number of hotels, restaurants, shops, and tour operators, each of which
respond to their own sets of incentives. Moreover, mitigating the consequences
would require high public investments in roads, utilities, and other
infrastructure.
Fisheries
Foods harvested from the sea have historically provided an important staple
in the diets of the inhabitants of the Mediterranean, especially the small
islands. With the development of food preservation techniques and faster
transport, the consumption of fresh seafoods has spread inland.
About 4 million tons of seafood are produced in the Mediterranean countries
every year. The needs of individual Mediterranean countries for seafood are
basically satisfied through national fishing. The annual catch on the
Mediterranean is approximately 1 million tons.
Although the total catch has remained constant for about the last 10 years,
there have been significant changes in the species composition of the catch (Blue
Plan, 1988). This change has resulted from the overexplcitation of some species,
the demands of the market, and the development of specific new techniques in
fishing. Looking at individual countries, we find major differences: In more
developed northern countries, there has been a significant decrease in the number
of average-quality fish (sardines, mackerel) caught and an increase in the number
of high-quality fish (mullet, perch, dorade). In the less developed countries,
there has been no real change in the catch of poorer quality fish.
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Wed/terranea/7
According to some assessments, the present level of fishing is close to the
sustainable catch, endangering the existing fish stock. In some regions the
catch may not be threatening species survival, while in other areas certain
species are clearly overfished. The consequences at first are reduced catches,
but eventually the species can disappear (e.g., mackerel in the Adriatic Sea).
Because sustainable yields themselves will change, better assessments and
regulation to ensure an optimal catch without overexplcitation will be even more
important in the face of climate change.
It is likely that the expected climate changes will break existing
ecological balances and chains, and new ones will be formed on significantly
different levels. The Mediterranean region is typical of this problem, because
it contains species that are heterogeneous in every individual area, the result
of the vastly different biotypes. Generally speaking, the weak primary production
limits fish stocks. Cyclonal activity directly affects the dynamics of water-
mass movements, especially in shallower coastal regions.
A general decrease of precipitation is predicted for the entire year and
for the summer period.4 The resulting increase in the salinity of the sea, along
with sea level rise, could affect the inflow of nutrients from river runoff or
from "upwelling" of deep-sea waters. The changes in the physical characteristics
also could affect the oxygen solubility in the sea. The changes in the physical
characteristics could speed up the physiological processes of marine organisms.
They also could accelerate the mineralization of organic matter.
The rise in the sea temperature in the shallow coastal waters could create
subtropical or even tropical conditions, which would probably stimulate a greater
immigration of numerous plant and animal species from the Red Sea through the
Suez Canal into the Mediterranean region. Some plant and animal species
indigenous to the Red Sea have already naturalized in the eastern Mediterranean,
but in the future they will spread westward. In contrast, the boreal species
will be endangered or may even disappear.
These changes could bring about major alterations in the qualitative and
quantitative composition of the Mediterranean marine flora and fauna.
Economically important populations of marine organisms will also be affected.
Climate change also may cause subsequent changes in the migratory habits of fish
species that constitute the largest part of the annual catch. Likewise, a shift
in the distribution of niches of some other economically important species may
require significant modification of existing fishing techniques. This may
include new devices and equipment for detecting fish, larger boats capable of
fishing in farther and deeper waters, and new fishing equipment. All these
changes will require significant financial expenditures that may depress further
development of fishing in the economically weaker countries.
4 However, in some regions of the Mediterranean, precipitation and/or the
inflow of freshwater may increase. Nonuniform changes in precipitation could
cause very complex alterations in the physical characteristics of the
Mediterranean Sea, especially the shallow coastal areas.
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Baric
Aquaculture
Some countries have tried to satisfy the demand for high-quality fish by
artificial fish production, although it still accounts for a small fraction of
total fish consumption. In 1987, approximately 26,500 tons of high-quality fish
were produced; by 1992, this number is estimated to reach 44,000 tons (Blue Plan,
1988). About 90% of the present aquatic farming in the Mediterranean occurs in
lagoons. Other techniques, for example raising fish in tanks, are being
introduced in some countries.
The Mediterranean coast provides great conditions for further development
of aquaculture. However, uncontrolled development often endangers the areas
suitable for aquaculture. If aquaculture is to be notably increased, measures
for the protection of suitable habitats must be taken immediately. Within the
framework of the program prepared by the Priority Action Programme of the
Mediterranean Action Plan in cooperation with the Food and Agricultural
Organization, ecological criteria for the rational development and protection
of aquaculture in the Mediterranean coastal regions are being developed, so that
the Mediterranean countries can in time legislate the proper protective measures.
Since marine aquaculture is mainly located in the coastal zones, climate
changes and their direct consequences (sea temperature rise, salinity rise, sea
level rise) will greatly affect its development. Keeping mind the fact that
marine culture in the Mediterranean comes from lagoons whose average depths are
only 50 cm, sea level rise may make the lagoons completely unfit for production.
New lagoons will need to be created or existing ones greatly modified.
A rise in both the salinity and the temperature of the Mediterranean Sea
will result in a decrease of oxygen solubility and an increase in the
decomposition of organic matter. This may enhance the oxygen depletion and may
even create anoxic conditions. On the other hand, warmer temperatures will
accelerate the growth of marine organisms in the colder periods of the year,
shortening the production cycle.
The changes in climate conditions may alter the effects of pollutants on
certain organisms. For example, the expected temperature rise may create major
changes in the bioaccumulation of certain pollutants, which may negative impacts
on some commercially important species. Regulations on the acceptable levels
of water pollution in fish ponds may need to be amended, and some aquacultural
activities may need to be relocated (see Titus, Problem Identification, Volume
1, for additional discussion of impacts of sea level rise on fish ponds.)
Community Infrastructure
The discussion here on human settlements is restricted to freshwater supply
and wastewater collection, treatment, and disposal. Although little technical
data are available on community infrastructure in the Mediterranean region, we
can anticipate the general impacts of climate change. However, the impacts will
vary by locality.
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Mediterranean
When discussing infrastructure along the Mediterranean, we must distinguish
between the northern, eastern, and southern areas, and between urban and rural
units. Infrastructure is generally most numerous in the cities of the more-
developed northern countries. While all northern cities have systems of
waterworks, most areas in the south do not and some do not even have running
freshwater.
Until recently, most sewage systems in the Mediterranean released their
wastes directly to the sea by the shortest possible route. A large number of
small systems released wastes immediately under or just at the surface of the
sea. It was difficult to control these releases, and consequently coastal waters
became polluted.
Recently the philosophy and practice of wastewater management has been
changing. The general belief now is that wastewater should be collected, treated
to an acceptable degree of contamination, and then released through a long
pipeline far into the sea., This method of wastewater disposal also allows for
the reuse of wastewater -- a point of great importance to areas with inadequate
water sources. Israel has not released any wastewater into the sea for the last
several years; after proper treatment it is reused, mainly for irrigating crops.
The expected climate changes will have affect existing community
infrastructures and require new infrastructures. Basically, the reduction of
available water will exacerbate present-day problems in many areas. It will be
necessary to supply some cities and settlements with water from far-away sources,
since the local sources will have a lessened capacity and poorer quality.
Due to the temperature rise, the rate of growth of various microorganisms
in some water sources will increase, thus increasing possible waterborne
environmental health risks. Eutrophication may be intensified in some sources
and rivers. All this will require the construction of equipment and facilities
for freshwater purification, which will significantly increase the price of
freshwater -- the price may even double.
Sea level rise may endanger the sewage systems in some coastal cities,
particularly those whose sewage systems also serve as cisterns. Drainage may
also be more difficult. After rainstorms, wastewater may flood the lower parts
of these cities. Both this situation and the shortage of water will require the
construction of completely new sewage systems and facilities for wastewater
treatment and possibly reuse.
IMPACT ON THE DISTRIBUTION AND DYNAMICS OF COASTAL POPULATION
The current migration toward the coast will continue in the future, but with
less intensity than urbani2:ation. This latter process will be especially intense
in the southern and eastern parts of the Mediterranean, where today 40-50% of
the population lives in the urban areas. According to the Blue Plan (1988),
this figure is expected to reach 70-80% by the year 2025.
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Baric
Changing climate will have a limited impact on the population in the coastal
zone, especially in the initial years of accelerated sea level rise, assuming
that coastal defense measures are taken. The natural population growth is
primarily affected by other factors, such as the growth of the standard of
living, the growth of the economic vitality, the level of medical care, and
cultural and religious customs. Nevertheless, migration to the coast may be
accelerated in the south if global warming increases desertification.
Urbanization probably will be slower than predicted by the Blue Plan (1988).
Reduced water supplies, poorer water quality, the need for more purified drinking
water, transport of water from distant sources, plus a greater level of
wastewater treatment and recycling will require greater expenditures for urban
infrastructure. The resulting rise in the cost of urban living will slow the
migration toward cities. The temperature rise will make living in crowded cities
less pleasant during the summer. The hot exhausts of air-conditioning systems,
which probably will be increasingly used, also add to the warming in cities.
A reduction of their use would occur only with a drastic rise in energy prices,
which may be necessary to limit fossil-fuel emissions.
Our preliminary calculations suggest that at least 5% of the coastal
population -- some 6,700,000 inhabitants -- would be affected by the impacts of
sea level rise. Some of these people would be directly threatened with
inundation, but probably not more than 10-20% of the total number affected. The
repercussions will include the need to remove structures and construct new one
for the eventual relocation of the inhabitants.
CONCLUSIONS
Inertia is inherent to economic, social, and political institutions,
particularly for phenomena that will not manifest themselves in the near future.
But because recent information indicates that these changes could happen as early
the next decade, the public and the governments should start preparing for them
now. Our recommendations are as follows:
1. Information should be disseminated to the public as well as to all levels
of economic and political decision-making entities about the possible
consequences of gradual changes in the climate and the need for measures
to mitigate the impact. This should be a national action, not be left
to the local authorities or to coastal zones.
2. Local inventories should be made of the coastal zones, and data should
be collected on the expected local impacts of sea level rise and
temperature rise on water, soil, precipitation, and individual
socioeconomic activities.
3. A strategy should be developed that can react to changing climate
conditions, keeping in mind the accumulative nature of these changes.
Calculating expenditures for a given change or given time horizon ignores
any additional changes in subsequent years.
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VENICE: AN ANTICIPATORY EXPERIENCE OF PROBLEMS
CREATED BY SEA LEVEL RISE
A. SBAVAGLIA (Chairman Magistrate delle Acque in Venice,
Italian Ministry of Public Works)
C. CLINI (Chairman Expert Committee for R & Dr
Italian Ministry of Environment)
F. DE SIERVO (Technical Director, Consorzio Venezia Nuova)
G. FERRO (Deputy General Director, D'Appolonia S.p.A.)
Via Siena, 20
16146 Genova, Italy
ABSTRACT
This paper discusses the social, cultural, and other impacts of increased
flooding in Venice. It briefly describes Venice's physical, ecological, social,
economic, and cultural framework and the characteristics and evolution of
flooding phenomena. It then analyzes the short-term impacts of the increased
floodings and discusses the response of the city (and the country) at the social,
technical, and political levels. The paper next describes the special projects
being undertaken to prevent floodings, with particular emphasis on the mobile
gates at the lagoon entrances (whose construction will soon be started), on the
impact of this project, and on the reactions of the city. Finally, the paper
attempts to interpret the Venice experience, identifying the features that can
be considered as representative of generally expected impacts and the reactions
to sea level rise in seafront cities.
INTRODUCTION
Although it is necessary "to consider with great caution casual connections
(to the earth's climate evolution) often proposed" (Puppi and Speranza, 1988),
a large number of studies indicate that there is credible evidence for an
accelerated rise of sea level in the next century.
The current trend is characterized by an increase of about 10 centimeters
per century (Gormitz et al., 1982). With respect to this trend, all scenarios
forecast by different researchers indicate a significant increase. Most of the
studies forecast a rise in global sea level of between 25 and 75 centimeters by
the year 2050 and between 50 and 225 centimeters by the year 2100 (Titus, 1986).
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The many consequences expected In coastal areas as a result of sea level
rise can be classified into three categories: shoreline retreat, flooding, and
salt intrusion (Titus, 1986). These consequences would affect urban and rural
areas differently, but in both cases they would have significant economic,
social, and cultural impacts. All of these have been extensively investigated
by many authors in recent years. Previous assessments have been based on a
priori estimates of the impacts, since experience on this topic has not yet been
acquired. However, few cases exist worldwide that can provide a valuable insight
into the phenomenon. Among them, Venice represents an extremely significant
experience.
Since the beginning of this century, the relative mean sea level in Venice
has risen by about 25 centimeters, and the mean number of floodings of the city
has increased from less than 10 to more than 40 per year. Catastrophic
floodings, having a return period of 800 years at the beginning of the century,
presently have a return period of 200 years; that is, a 25-centimeter rise
quadrupled the risk of serious flooding. For these reasons, the problem of
protecting the city from the sea has taken an increasingly urgent priority, and
in such a way Venice represents the likely economic, social, and cultural impacts
that sea level rise would have on an urban environment.
This paper illustrates the Venice experience in order to provide some
indication for future, possibly more generalized situations. It first briefly
describes Venice and its environment and provides a short history of sea level
rise. It then analyzes the perception of the problem, discusses the short- and
long-term reactions, and presents the course of action that officials have
selected. Finally, it illustrates future perspectives and critically reviews
the Venice experience, outlining the most prominent aspects likely to be
experienced by coastal communities in general as sea level rises.
VENICE AND ITS ENVIRONMENT
The Venice lagoon is the most important remnant of a series of lagoon
formations that, thousands of years ago, occupied all the northern bow of the
Adriatic. It is made up of a basin of 550 square kilometers, and is connected
to the sea by three openings at Lido, Malamocco, and Chioggia (Figure 1). The
basin has an oblong and arched shape and extends about 50 kilometers along the
Adriatic coast, varying from 4 to 15 kilometers in width, with an average depth
of about 1.5 meters.
One portion of the lagoon (420 square kilometers) is permanently submerged
by water (shallows); another is permanently above the water (islands and
urbanized areas). Of the remainder, one part (the "barene") is submerged only
by normal tides, while another part (the "velme") is generally submerged and is
above water only during very low tides. At the edge of the lagoon, 90 square
kilometers of water are reserved for fish farming. Figure 2 illustrates various
parts of the Venice lagoon.
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Figure 1. Map of the Venice lagoon.
The evolution of the Venice lagoon has been reconstructed on the basis of
geological studies. About 10,000 years ago, the sea level began to rise and the
coastline migrated north from the lower Adriatic. When it reached approximately
the present location (about 6,000 years ago), an intense and prolonged alluvial
phase took place. Sediment flowed into the sea and was distributed along the
coast by the wave motion and the sea currents, forming the littoral line that
delimited the primitive Venice lagoon (albeit with a smaller extension than the
present one).
Among the factors affecting the lagoon's morphology during the ages, the
activity of the lagoon's tributaries was dominant. They kept the water brackish
(rather than salty), but they also threatened to make the entire lagoon a
marshland and eventually to fill it completely.
The lagoon is an extraordinary environment to be conserved and protected,
with a balance between the natural beauty of the place and the needs of the
communities living there. Several hydraulic works have been carried out to
preserve it, particularly the diversion of major tributaries into the sea, the
location of the sea entrances, and the dredging of channels for inland
navigation.
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Figure 2 (A). Historic Venice.
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B
Figure 2 (B and C). Aerial view of a fish farm in the Lagoon of Venice.
Conditions in the lagoon are particularly favorable for this type of fish
farming. This had led to the construction of numerous dykes which isolate the
farms that are now part of the Venetian landscape.
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Figure 2 (D). Aerial view of a low-tide inlet of the Lagoon of Venice. The
strips of land that emerge at low tide are a distinctive feature of the lagoon
They have a very important hydraulic and ecological role; they can attenuate
currents and wave motion, and so help to control two of the causes of the city's
decay.
The Venice lagoon is characterized by networks of deep natural channels to
the mainland, which branch out of the three openings. Other manmade channels
have been operated over the centuries to improve navigation within the lagoon,
and two large channels have been created in recent times to house shipping to
the industrial Port of Marghera: the Vittorio-Emanuele Channel (1926) from the
Lido opening, and the San Leonardo Channel (1968) from the Malamocco opening
Tides propagate primarily along these natural and manmade channels.
To allow ships of increasing tonnage to enter the lagoon (for military and
commercial reasons), as well as to avoid the frequent malaria caused by stagnant
water, the Venetians carried out, between the 16th and 19th centuries, a complex
series of works to redirect the course of rivers such as the Brenta, Piave, and
Sile, so that they came out into open sea rather than within the lagoon. In this
way, the flow of freshwater into the lagoon was reduced, and the rivers no
longer carried sediments into the lagoon, which in the long run would have caused
the basin to silt up.
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Other internal defense measures were undertaken against the major external
threat represented by the sea. In the 18th century, the "Murazzi," massive
seawalls performing their function even today, were built to protect the shores
from flooding by high tides. Between the 19th and 20th centuries, breakwaters
were also built to prevent the silting up of the three openings to the sea. As
a result, the tidal flow between the sea and the lagoon was increased along with
the speed of the tides in the internal channels, leading to noticeable changes
in the physical characteristics of the lagoon. These changes were further
emphasized by the two large shipping channels opened during this century. For
the Venetian lagoon, therefore, the problem has always been one of maintaining
the equilibrium between the natural and human environments.
The presence of human settlements in the lagoon has made the ecological
balance even more complicated, and so the search for an equilibrium between the
various needs of the environment is becoming increasingly difficult. The
movement of the sea is essential to the renewal of the lagoon's waters, removing
human, industrial, and agricultural waste, but stronger tides must be controlled
to avoid both flooding of inhabited areas and erosion of the "barene," which
would silt up the channels.
SEA LEVEL RISE IN VENICE
From the hydraulic point of view, the complex system of the Venice lagoon
can be subdivided into (1) the basin of Lido, or the northern lagoon; (2) the
basin of Malamocco, or the central lagoon; and (3) the basin of Chioggia, or
the southern lagoon. Each of these three basins is connected to the northern
Adriatic by inlets, known as port openings. The three port openings have a total
cross-sectional area of approximately 18,000 square meters, and for each tidal
cycle about 330 million cubic meters are exchanged.
Approximately 430 square kilometers of the lagoon are open to tidal
expansion, which flows into the lagoon through the three openings along the 800-
kilometer network of channels. These channels wind across shallow waters and
"velme" (areas of the lagoon usually covered with water), islands, and "barene,"
and their depth and width gradually decrease as they reach upland to the extreme
borders of the lagoon. Excluding fish farms, 75 percent of the area subject to
tidal expansion is between 0 and 2 meters deep, whereas only 5 percent exceeds
5 meters, as is the case of the deepest channels.
In this natural environment, with largely urbanized areas, the phenomenon
of exceptionally high tides is taking place with an increasing frequency, thus
becoming a real threat to Venice and its lagoon. High tides are often determined
by the coincidence of various factors: the normal astronomical tide, the
scirocco wind that drives waters of the Adriatic to the north, the sea level
fluctuations due to different atmospheric pressures at each end of the Adriatic
(seiche), rain on the catchment basin drained by the lagoon, and finally the
seasonal variations in the level of the Mediterranean Sea.
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The frequency and severity of tidal floods increased in this century as a
result of sea level rise due to the melting of world's glaciers, and as a result
of land subsidence due to natural settling and the drawing of water from artesian
wells.
Land subsidence, which is also caused by natural factors, played a major
role in the origin and evolution of the lagoon, and has become a determining
factor affecting the city and lagoon environment after human intervention.
Anthropogenic subsidence initially started with the heavy groundwater pumping
used mainly for industrial purposes. Intense pumping of groundwater resources,
which is the main cause of Venice's sinking, mainly occurred between 1950 and
1970. Since the progressive reduction in artesian water consumption started in
1970, the piezometric levels have moved back to their original values, and by
1978 the natural aquifer pressure had been reestablished.
Aquifer depletion and subsidence ran parallel courses between 1950 and
1969-70. Both reached their peak values in 1969, when subsidence was reported
to be 12 centimeters in the industrial zone and 10 centimeters in Venice. With
the reduction in consumption and further natural recovery of aquifers after 1970,
the land survey of 1973 showed subsidence to be slowing. A small rebound (of
the order of 2 centimeters) in the historical center was measured during the 1975
survey.
However, human-induced subsidence was not the only factor causing more
tidal floods in the lagoon: natural subsidence and global sea level rise
(eustacy) also contribute to the diminishing land surface level of the city with
respect to the sea level, thus increasing the impacts of high tides (Carbognin
et al., 1984).
Leveling measures from before and after groundwater exploitation -- i.e.,
between 1908 and 1980 -- suggest that the present natural subsidence is about
half a millimeter per year. This annual average rate is appreciably lower than
the average rate of about 1.3 millimeters per year estimated with reference to
the last millennium.
Eustacy has affected the water level of the lagoon due to its connection
to the Adriatic Sea. From the beginning of this century, the sea level has been
rising 1.27 millimeters per year.
These three factors (human-induced subsidence, natural subsidence, and
global sea level rise) and their effects on the Venetian environment are depicted
in Figure 3. The period 1908-80 includes the different stages of land sinking.
The aforementioned anthropogenic subsidence lowered the land an average of 10
centimeters, netting out any rebound.
In conclusion, these three factors have lowered the surface level with
respect to sea level by about 22 centimeters from the beginning of the century.
Today the mean elevation of the land surface of the city is about 110 centimeters
above mean sea level, while 80 years ago it was nearly 130 centimeters. This
loss of 22 centimeters has caused Venice to flood more frequently.
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NATURAL
— .
Subsidence
Natural Trend Period Influenced by Hun an Activity
1920
1940
1960
1980
Figure 3. Eustacy and subsidence trend.
Parallel to the rise of relative mean sea level, high tides have increased
as well. Figure 4 shows the increase of the annual mean level of high tides (as
well as of low tides) from 1920 to 1980. In Figure 5, the number of high tides
for height classes (for each 10 years from 1955 to 1985) is presented. The
increasing number of exceptionally high tides is clearly indicated. For
instance, between 1931 and 1945, eight exceptionally high tides took place,
reaching or exceeding 1.10 meters above the average sea level; whereas between
1971 and 1985, with the increased subsidence due to human interventions
subsequently interrupted, forty-nine high tides were recorded.
As Figure 6 shows, Venice is extremely vulnerable to sea-induced flooding.
When water levels are 70 centimeters above zero (relative to the Punta del la
Salute hydrometer), St. Mark's cathedral is flooded; at 80 centimeters, water
pools appear in St. Mark's square; at 90 centimeters, the square cannot be walked
through any more and begins flooding the lowest streets ("calli"); at 140
centimeters, more than 60 percent of the city is flooded. In the period 1920-50,
the tidal level exceeded the "critical threshold" level of 80 centimeters 15
times a year. This threshold has been exceeded, on the average, 25 times a year
in the period 1950-60, and 50 times a year since 1960. Exceptionally high tides
(e.g., greater than 140 centimeters) have become more frequent as well. Looking
back to history, during the preceding seven centuries the Republic of Venice was
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1920 1930 1940 1960 1960 1970 1980
Figure 4. Annual average high (a), mean (m), and low (b) tides.
'•»••*
a) HIOH TIDES
b) LOU TIDES
Figure 5. Number of high tides for height classes.
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Sbavaglia, et al.
subjected to fewer exceptionally high tides (51) than in the 52 years between
1914 and 1966, when it experienced 53. Figure 7 illustrates the area flooded
by tides of 1 to 1.9 meters.
PERCEPTION AND SHORT-TERM EFFECTS
Venice has always been a sea-town, organized and subordinated to the lagoon
environment. Its economy was based mostly on shipping. Water was an essential
factor of life. It simultaneously meant refuge, safety, nourishment, income,
and prospects for development. As an example, until 1300 there were no streets
in Venice: its channels were the only transportation system, and the boat was
the only transportation facility in town.
Though Venetians became allied with the lagoon water to build their "living
environment" on the archipelago, practically in every age calamities have been
reported periodically affecting the town. An exceptionally catastrophic event
occurred on November 4, 1966, at the time of a big flooding of the Padana Plain
by the Po River and of the city of Florence by the Arno River: a tide 194
centimeters above average sea level was recorded. More than 4,000 ground-floor
apartments were inundated, and more than 13,000 people lost their homes. The
tide devastated shops and storerooms, caused an electric blackout, and cut off
gas supplies and telephone connections.
Although the problem of rising sea level was already studied and discussed
by a few specialists in the fifties and early sixties (e.g., Miozzi, 1960), at
that time the problem was basically ignored by public opinion and the political
groups. The main issues at the beginning of the sixties were the industrial and
urban development of the city and the surrounding area.
The situation suddenly changed after the catastrophic 1966 event. The high
tides ("acque alte") immediately became the central problem of the public debate.
The impact was enormous, not only in Italy but worldwide, and committees to "Save
Venice" grew up all over the world. The event, defined by an author as being
"cruelly beneficial" (Miozzi, 1968), also gave a substantial impetus to the work
of the interministerial committee "Per lo Studio dei Provedimenti a Difensa della
Citta di Venezia," set up in 1963 and practically inactive until then.
The high tides continued in the years after 1966 (basically at the same
level as during the years immediately prior), and the press gave them extensive
attention. In 1970, a public body was set up to predict high tides.
Meanwhile, the program for protection proceeded slowly. The slowness of
the interministerial committee that was supposed to coordinate the operations
exasperated the citizens. The Venetians protested and organized symbolic
demonstrations of disapproval of the city's administrators.
In 1971, seven proposals for a special law for Venice were presented within
eight months. Finally, after endless discussions and a large number of
amendments, on April 16, 1973, the Special Law (Law 171/73) was approved. It
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Figure 6. Flooding in Venice (continued): (C) Venice during the exeptional
flood tide of 1966, (D) damage to buildings produced by the combined action of
high tides and wave motion.
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Figure 7. The shaded areas show the portion of Venice flooded by tides of (A)
1 m, (B) 1.1 m, (C) 1.2 m, and (D) 1.9 m. Assuming no change in storm frequency,
these areas will be underwater 50 times a year for rises in sea level of 20, 30,
40, and 110 cm, respectively.
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established that the national government should take care of the physical
safeguarding of the lagoon and urban areas; the regional government would be in
charge of planning activities; and the city government would manage the
restoration of the historical center. The planned response measures have four
objectives: the physical safeguard of the lagoon, decontamination, the
restoration of monumental and smaller buildings, and the economic development
of the Venetian area. The law also provided financial support of 300 billion
lire (about 3 billion U.S. dollars). At that time, many people believed that
most of the problems were over. However, the long path toward the protection
of Venice from high tides was just beginning.
LONG-TERM REACTIONS
Since the Venice program started in 1973, the people became more and more
accustomed to the periodic: flooding of the city, intensifying public commitment
to a solution.
To carry out the 1973 Special Law, an international bid was issued (Law
404/75) to solicit proposals for implementing the Special Law. Five groups of
well-recognized companies submitted their proposals, but none was considered
adequate (March 1978). Then the Ministry of Public Works was authorized to buy
the projects submitted (Law 56/80). The Ministry commissioned a group of
internationally recognized experts to draw up a plan of action to protect the
city from high tides. The plan was based mainly on the idea of temporarily
closing off the lagoon at the three openings, using barriers that were in part
fixed, in part mobile. These would normally be left open and closed only when
necessary.
The project drawn up by the experts was approved in 1982 by the Supreme
Council of Public Works, which established that the work should aim, above all,
to achieve these primary objectives:
the reduction of flood tides in the lagoon;
the guarantee that a sufficient renewal of the lagoon water would be
maintained to prevent a worsening of the water pollution;
the maintenance of the three openings at Lido, Malamocco, and Chioggia
as viable port entrances, limiting closures to a minimum.
To carry out intensive studies of the area, test possible solutions, and
then plan and carry out a complex series of measures that should meet the needs
of both the environment and the tourist, commercial, and industrial activities
that are now part of it, the Italian Government has entrusted the Venezia Nuova
Consortium.
The project drawn up by the experts in 1981 suggested, as a solution to
the problem, the installation of mobile gates set in fixed barriers. The
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barriers made it possible to reduce the effects of excessively high tides, but
they also permanently reduced the exchange-flow between the sea and lagoon.
The "Venice Project" has as its primary objective the conservation and
development of the city of Venice, and of its lagoon, which is a unique
ecosystem. This obviously requires controlling the high tides. The difficulty
arises from the impossibility of closing off the lagoon from the sea for long
periods of time. The tides have a fundamental role in maintaining the life of
the lagoon environment. Even a simple reduction in the exchange-flow could have
consequences that should not be underestimated (see Park, Volume 1).
The series of operations to safeguard Venice was given its clearest
definition in Law 798 of November 29, 1984.
In 1982, the Magistrate alle Acque charged the Consortium with the task of
carrying out studies and producing mathematical models of the lagoon. These
studies were to focus on reestablishing the hydrogeological equilibrium of the
lagoon; arresting and reversing the process of decay within the lagoon by
eliminating its causes; reducing the level of the tides in the lagoon; defending,
with specific local measures, the islets that make up the city center; and
safeguarding the urban areas of the lagoon from flooding by means of mobile
gates at the three openings to regulate the tides. The work of the Consortium
actually started in 1986.
To finance this first stage of operations, the law set aside 234.5 billion
lire (almost 2 billion U.S. dollars). The funding for the following studies was
to be guaranteed by the budgets from the fiscal year 1987 onward. An updated
estimate of the cost of the work is 3,300 billion lire.
THE PROJECT AND THE PROBLEMS
To protect Venice and its lagoon from sea level rise, the only possible
solution is the control of tidal flow at the port openings. In compliance with
Law 798, the solution that has been found most suited to the conditions and needs
of the lagoon environment consists of a system of mobile structures for the
regulation of tidal flow.
The project envisions the use of specially designed gates, respecting the
typical conditions of the lagoon system from the viewpoints of both the
environment and socioeconomic development. For each port opening, a set of
rectangular flap gates will be installed; these will be hinged to a foundation
structure made of cellular-reinforced concrete caissons.
Each gate -- i.e., each module -- is 20 meters wide (Figure 8). In their
"off" position, the gates are flooded and lie horizontally in a recess in the
foundation structure. If necessary, by expelling part of the water they contain,
the gates are lifted to their operating position (at an angle of 45 degrees with
the horizontal) to stop the tidal flow. The gates have no intermediate piers
to hold them in their operating position and, therefore, oscillate freely under
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A
B
Figure 8. (A) Schematic illustration of the mobile gates and (B) gate being
towed past San Marco.
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the action of the waves, which are transmitted, practically unaltered, to the
lagoon. The compliance of the gates with the waves drastically reduces the
forces transmitted to the foundation structures, thus simplifying their
construction and reducing costs as compared with more traditional solutions.
In normal conditions, when the gates are open, the port openings are free
from any structure. Therefore, there are no obstacles to either water flow or
navigation. There will be no aerial superstructures, either temporary or
permanent, since these would alter the landscape and could hinder the transit
of ships.
Although strongly requested after the 1966 event, the project for the
temporary closing of the lagoon has encountered increasing public opposition.
A strong environmental concern grew, fed by the tremendous environmental
degradation of the lagoon. Fear was expressed that the closing of the lagoon
could reduce the water exchange and further worsen the environmental problems.
In view of the rise of the "green movement," increasing attention was devoted
to those concerns, and a number of additional detailed studies were performed
by the Venezia Nuova Consortium to investigate these problems. However, a final
approval of the project is still pending.
In the same period, the interministerial committee, set up by the Law
798/84, recognized the pollution of the lagoon as a major problem and started
a restoration plan. The guidelines for the restoration plan were approved by
the Committee in October 1989.
Updated estimates indicate that the total financing needed for safeguarding
and restoring Venice and the lagoon will most likely reach some billions of
dollars.
CONCLUSIONS
During this century, Venice has experienced a significant increase in both
the frequency and the magnitude of periodic floodings. This is due to a number
of different simultaneously occurring causes (particularly mean sea level rise
in the Adriatic Sea and land subsidence due to uncontrolled exploitation of the
water table). The experience of Venice has many similarities with the expected
effects of the sea level rise on other seafront cities, at least in a first
stage.
However, although the Venice situation represents a very interesting case
study, some of its peculiarities must be carefully considered:
its physical characteristics -- i.e., the presence of the lagoon between
the sea and the inland environments;
its sociocultural implications, since the sea-town of Venice always
tried to manage the lagoon environment not only by integrating itself
with the element "water" but also by developing its organization "on
the sea"; and
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its political and economical peculiarities, being a "unique" town
worldwide and having available large financial resources.
Some interesting conclusions can be drawn from the Venice case study:
sea level rise (although of limited extent) represents a critical
problem for the town;
the problems were recognized for a long time by the scientific community
and were outlined to the public administration, but interventions were
started only following a catastrophic event;
the definition and implementation of remedial measures required a very
long period of planning and study, and after 20 years real work still
has to start;
some years after the catastrophic event, Venetians started to accept
the floodings as an unavoidable phenomenon in its particular habitat;
as time passed, other issues started to be considered essential for the
remedial measures (environmental conservation, city development, etc.),
slowing down the initial rate in the development and implementation of
the remedial measures; and
remedial measures need very large financial resources, that in general
can be collected only from the national government.
From a more general point of view, the Venice case can provide some
guidelines on the following:
the need to focus in advance public attention on both the primary and
secondary effects of the sea level rise phenomenon;
the need to consider the environmental, urban planning, and
socioeconomic impacts of the safeguard projects from their inception;
and
the need to clearly evaluate the project's financial requirements and
to assign priorities.
In particular, we believe that it is not generally possible to rigidly
maintain the "ante quo" situation. Rather, when a sea level rise effect is
forecast, it is necessary to develop a new environmental strategy, (1) with
adequate human, urban planning, and aesthetic characteristics; (2) with limited
social and cultural impacts; and (3) that is achievable with available financial
resources.
BIBLIOGRAPHY
Carbognin, L., P. Gatto and F. Marabini. 1984. The City of the Lagoon of Venice
- A Guidebook on the Environment and Land Subsidence. Venice.
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Gormitz, V., S. Labedeff and J. Hansen. 1982. Global sea level trend in the
past century. Science 215:1611-1614.
Miozzi, E. 1960. La Conservazione e la Difesa dell'Edilizia di Venezia, il
Minacciato suo Sprofondamento ed i Mezzi per Salvarla. Proceedings of the
Conference for "La Conservazione e Difesa della Laguna e della Citta di Venezia".
Miozzi, E. 1968. Venezia nei Secoli, Vol. Ill: La Laguna. Venice: Libeccio
Publishers.
Puppi, G., and A. Speranza. 1988. The physical problem of global climate on
Earth. Alma Mater Studiorum 1:1-14.
Titus, J.G., ed. 1988. Greenhouse Effect, Sea Level Rise and Coastal Wetlands.
Washington, DC: U.S. Environmental Protection Agency.
Titus, J.G. 1986. Greenhouse effect, sea level rise, and coastal zone
management. Coastal Zone Management Journal 14:3.
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IMPLICATIONS OF SEA LEVEL RISE FOR GREECE
DR. HAMPIK MAROUKIAN
Department of Geography
University of Athens
Athens, Greece
INTRODUCTION
Many parts of coastal Greece will be seriously affected by a rising sea
level. If drastic measures are not taken soon by state and local governments,
it will be much more difficult and more costly to face this problem later.
Consider the delta of the Sperkhios River. If sea level rises 2 meters in
the next century, this deltaic plain could lose about 40 square kilometers of
land. A rising sea level would also cause serious problems to coastal urban
areas, industries, settlements, harbor facilities, tourist complexes, coastal
communication networks, airports, and other infrastructure. The areas that will
probably be most threatened are the big harbors of the country: Pireas,
Thessaloniki, Patra, Volos, Iraklio, Alexandroupoli, etc. Many airports like
Kerkyra, Alexandroupoli, and Thessaloniki are almost at sea level and will
certainly be threatened. Coastal highways in northern Peloponnessos,
Thessaloniki plain, Sperkhios delta, Porto Lagos, etc., will have problems too
(Figure 1).
The incursion of the sea will create another very serious problem to the
coastal environment, that of erosion. This process will most certainly affect
densely populated coastal zones on low to intermediate slopes. In recent
decades, more than one million cottages have been constructed on or near the
coastal zone. Many of these already face erosion problems, since they were
constructed without prior knowledge of the conditions that prevailed in the
environment. Thus, a sea level rise of just a few decimeters would be
destructive to all these structures. Unfortunately, nothing has yet been done
to put some limitations on coastal construction.
Correspondingly, similar problems are expected to occur in coastal
cultivated areas like the deltaic plain of the Sperkhios, the plain of
Thessaloniki, the Argolis plain, Akheloos plain, and the Louros-Arakhthos plain.
It is believed that parts of the extensive drainage and irrigation networks of
these areas will be rendered useless. The groundwater table will also be
affected by rising seas. The underground saltwater wedge in the water table will
certainly shift inland, affecting cultivated land.
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25°
28°
40°
PATRA
KORINTH
i*
NAFPLI
LEGEND
Cities
Industries
Airports
Wetlands
Fisheries
Saltworks
TERRANEAN
SEA
0 50 100 150 Km
22°
25°
28°
Figure 1. Map of Greece.
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Haroukian
Finally, coastal wetlands will be covered by the rising sea level and an
important natural resource of the environment of Greece will cease to exist. The
lagoons of Messologi, Amvrakikos, and Porto Lagos, which are important fishing
grounds, will become shallow bays or gulfs. The extensive saltworks of Messologi
and other areas of Greece will have to move farther inland.
Despite these problems, the prospect of sea level rise does not seem to
concern officials from government or private organizations in Greece. In recent
meetings with high ranking officials of the Ministry of Environment, Physical
Planning and Public Works (the main agency responsible for the management and
protection of the Greek Coasts), they agreed that they would eventually need to
take measures to confront the problem, but they felt that there is no urgency
today. They generally encouraged me to assess in more detail the likely
consequences of global warming and sea level rise, and to come back and suggest
to them options that could be rationally implemented today, given the
uncertainties.
This initial response made me realize that the most fundamental barrier to
responding to sea level rise in Greece will probably be similar to the barrier
that has confronted the world in general since Svante Arhenius warned us of the
greenhouse effect in 1896: the information gap between researchers and policy
makers. This gap is more than a failure to communicate often enough: between our
respective fields of scientific and policy expertise lies a conceptual "no man's
land" into which both scientists and policy makers are reluctant to tread.
As I left the meeting, my initial reaction was that the policymakers seem
to unrealistically expect me to have all the answers on a "silver platter." But
on the other hand, perhaps I was unrealistic to expect that if I presented them
with scientific information on an environmental risk, they would be able to give
me the response options on a silver platter. Scientists feel comfortable
describing observable facts, but are hesitant to speculate about future impacts
of new phenomena, and are even less qualified to recommend policy actions. Yet
by the same token, policy makers that feel comfortable making decisions when all
the options have been laid out feel less qualified—and often lack the time--to
develop planning and structural responses that have not been thoroughly assessed.
To properly respond to sea level rise, scientists and policymakers must work
together to answer questions that are interdisciplinary in the broadest sense of
the word.
But the necessary collaborative effort has not yet gotten under way in
Greece, so it is not possible to provide a detailed examination of the impacts
and responses to sea level rise. The remainder of this paper describes the
environment and the resources at risk.
THE NATURAL ENVIRONMENT
Climate and Tides
The coastal climate of Greece can be characterized as Mediterranean with
warm to hot dry summers and moist cool winters. Storms are not a common
phenomenon in Greece. Storm winds usually blow from the northern or southern
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quadrants. Those from the east or west are rare and of short duration, no more
than one or two days.
The tidal range around Greece, as in all of the Mediterranean Basin, is
small. The greatest tidal range is observed at the Strait of Evripos where the
northern and southern Evvoikos Gulfs join. The maximum tidal range is 1.20 m in
the northern port of Khalkis and the mean is 0.42 m.
Although the Greek region has numerous earthquakes, tsunamis are rare.
Nevertheless, it is very likely that the great explosion of the volcano of Thera
(Santorini) around 3,400 years ago was followed by a catastrophic tsunami that
reached all the shores of eastern Mediterranean Sea. According to Galanopoulos
(1960), from 1801 to 1958 there occurred 170 earthquakes with a range fron I to
VIII on the Mercalli-Sieberg scale, but only 6 tsunamis were destructive.
The low tidal range and absence of frequent storms implies that it has been
safe to build one to two meters above sea level. As Titus (this volume, Problem
Identification) points out, this situation potentially makes low areas more
vulnerable to inundation than areas with frequent storms or large tidal ranges.
Types of Coasts
Fortunately, Greece does not have a particularly flat coast, except for
deltas. About 31% of the coasts are rocky with slopes greater than 50%,
generally along the northern portion of the western coasts of Greece, the
northeastern coasts of the Gulf of Corinth, the western coasts of the Aegean, and
some parts of Khalkidiki (Figure 2). Another 25% of the coasts have slopes
between 10% and 50%; these shores are often easily erodible, e.g., the southern
Korinthiakos Gulf.
Despite the predominance of steep coasts, about 45% of the coast has slopes
less than 10%. These include the deltaic plains of Arakhthos-Louros, Akheloos,
Pinios (Peloponnessos), Sperkhios, Pinios (Thessalia), Aliakmon-Axios, Evros, and
the fan delta of Nestos; the barrier beaches of northwestern Peloponnessos,
Akheloos-Messologi, Amvrakikos, and Nestos; the lagoons of Messologi, Amvrakikos,
and Vistonida; and all the pocket beaches, accretion beaches, and coastal plains.
Figure 3 shows a number of low-lying areas in Greece.
The sediment size of most of the depositional features is in the sand range,
but in many parts the presence of pebbles and stones is not uncommon. Although
the presence of sand dunes is not rare in many parts of Greece, they are located
along the coast without extending inland because of the short duration of the
high intensity winds.
A final feature typical of warm seas is the presence of beachrocks. They
all seem to be eroding today and are found mostly in the central and southern
part of the country, usually in sandy beaches. Most of them date from the Late
Holocene age and are located a couple of meters above or below present sea level.
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Maroukian
Gently sloping coasts
Intermediate coasts
Steeply sloping coasts
o Major ports
Figure 2. Distribution of slopes along the coasts of mainland Greece.
There are five major deltaic plains (Evros, Axios-Aliakmon, Sperkhios,
Akheloos, and Louros-Arakhthos) and four regions with barrier beaches, barrier
islands, and spits (Amvrakikos, Akheloos-Messologi, northwestern Peloponnessos,
and Nestos). There are also numerous pocket beaches, accretion beaches, and fan
deltas (the largest at Nestos).
Wetlands
The Ramsar Agreement, concluded in Iran in 1971, called for each country to
delineate the wetlands that were environmentally significant. For Greece these
are the following:
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°> B
'
,r. e road is gone
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Figure 3 (D-F). Low-lying areas of Greece,
(D) Saltworks in Zakynthos island, western
Greece.
(E) Astakos, west-central Greece. Barrier
beach.
(F) Amvrakikos Gulf, western Greece.
Barrier beach with lagoon on the
right.
-------
Wec//terranea/7
The Evros Delta Wetland
The River Evros is one of the largest rivers of the Balkan peninsula and is
characterized by high discharge and sediment transport rates, particularly during
the winter and spring months. There are four lagoons and at least three barrier
islands of limited size. Until 1950, human interference in the natural
environment was minimal. Since then, various artificial drainage systems control
to a large degree the flow of the river.
The Vistonida-Porto Lagos Wetland
Lake Vistonida is located in central Thrace and is the extension of the bay
of Porto Lagos. It has an area of 4500 hectares (11,120 acres) and forms a
shallow lagoon with an average depth of 2.0-2.5 meters and a maximum of 3.5
meters. The average height of Vistonida is 0.10 meter. The deterioration of the
surrounding lowlands has led to their increased erosion and sedimentation
deposition in the lake, which has resulted in a rise of the lake bottom by 0.40
meter from 1976 to 1982.
The Nestos Delta Wetland
The Nestos River is the natural boundary between Macedonia and Thrace. Its
source is in Bulgaria and its length in Greece is 130 km. The main wetland area
comprises the main channel, the bank zones, and the coastal zone of lagoons (Nea
Karvali-Nestos mouth - Cape Baloustra). The general area of the coastal zone (a
length of about 45 km and width of 1.5-3 km together with the Nestos Delta) is
characterized by a great variety of biotopes with various plant colonies and
zones of vegetation. The present cultivation of the land has worsened the
conditions in the Nestos wetland.
The A1iakmon-Loudias-Axios Delta Wetland
This region covers the lower deltaic plain of three rivers (Aliakmon,
Loudias, and Axios) and has an area of about 200 square kilometers. The largest
part has been apportioned to the local peasants. The coastal parts of the
deltaic plain are drained today for cultivation purposes. This process, together
with water and soil pollution, has turned this wetland into a very unstable and
endangered environment.
The Messologi Lagoon Wetland
This wetland is found in the middle of western Greece next to the Akheloos
Delta. It is composed of three lagoons (Aetoliko, Messologi, and Klisova) and
has a total area of 25,800 hectares (63,752 acres). The natural biotope has
deteriorated in the last twenty years owing to the draining of some areas and the
conversion of others to salt-works.
The Armvrrakikos Wetland
Found in northwestern Greece, the wetland forms a closed sea with a total
shoreline length of 256 km and a maximum depth of 60 m. The Louros and Arakhthos
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Maroukian
Rivers flow into the gulf where the Logarou, Tsoukalio, Rodia, and Mazoma Lagoons
are located as well as the Bay of Koprani. The wetland is burdened by human and
industrial effluents as well as agricultural and cattle by-products.
The Lake Koukhi Wetland
This wetland is located in northwestern Peloponnessos facing the Ionian Sea.
It connects to the sea through a very narrow inlet having a width of only 8 m.
The deepest part of the lake is 40 cm and the mean is 30 cm. Its area varies
seasonally from 710 hectares (1,754 acres) to 850 hectares (2,100 acres). It is
one of the largest lagoons in Peloponnessos. It is rapidly deteriorating, mainly
as a result of human activities (agriculture, hunting, and pollution).
Because of the low tidal ranges in Greece, these wetlands are barely above
sea level and hence would be mostly lost with a one-meter rise in sea level.
SOCIOECONOMIC FEATURES
Demography
A large part of the Greek population has lived near the coast since ancient
times. Many ancient city-states flourished along the Greek coast and in many
cases their very existence depended on their coastal colonies in the
Mediterranean Basin. The population of ancient Athens, for example, could have
been a few hundred thousand people. In Roman and Byzantine times and the ensuing
period of Turkish occupation between the fifteenth and nineteenth centuries, life
deteriorated and inhabitation in coastal areas decreased considerably. In the
early nineteenth century, Athens was just a village of 5-6,000 people. Today,
greater Athens has about 3.5 million inhabitants.
Table 1 gives a general picture of the proportion of inhabitants on or near
the coast of mainland Greece. This number is 52% of the total population of
7,083,000 living in the above-mentioned departments. If we consider the seasonal
migration of the Greek population toward the coasts in summer, then this
percentage could easily reach the 65% mark. Furthermore, if we include the
millions of tourists who visit Greece during the summer months, then it is safe
to say that for a considerable time of the year, about three quarters of the
population live along the coasts.
Harbors, Ports, and Other Coastal Structures
Various types of artificial structures are found along the coasts of
Greece. They may be classified into three main groups:
1. harbor and other ship-related structures,
2. coastal defense structures, and
3. water intake/outfall structures.
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Table 1. Number of Inhabitants Who Lived On or Near the Coast of Mainland
Greece (by department in 1981)
Department
Population (x 1,000)
Aetoloakarnania
Argolis
Arkadia
Arta
Attiki
Akhaia
Evros
Evvia
Ilia
Imathia
Thesprotia
Thessaloniki
Kavala
Korinthia
Lakonia
Larissa
Magnissia
Messinia
Xanthi
Pieria
Preveza
Rodopi
Fthiotida
Fokis
Khalkidiki
TOTAL (includes rounding)
99
49
9
28
1,947
190
48
116
71
3
1
597
83
60
21
11
135
72
5
29
25
3
63
9
23
3,697
Greece has a total of 444 commercial harbors of various sizes and
importance, of which 284 have sea defense structures (these numbers do not
include small harbors for local ferries). The first group of structures is by
far the most important. It includes, among other types, such structures as
moles, breakwaters, bulkheads, jetties, and trestles. Moles and breakwaters have
either vertical or sloping faces. The most commonly used materials are quarry
stones and concrete. In many cases, especially in the smaller harbors, jetties
serve several purposes including those served by moles and quays. The most
common type of quay walls are gravity walls of concrete blocks. Jetties are
usually formed with a surrounding bulkhead and backfilling.
Coastal defense measures usually consist of revetments, groins, and, more
recently, artificial nourishment. Coastal revetments and groins are built almost
exclusively with quarry and concrete blocks.
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In Table 2, the most important harbor installations are shown together with
passenger and cargo movement.
Pireas shows the greatest domestic movement of passengers and cargo, most
of it being car-ferries (ferry boats). Pireas together with Rafina serve to a
great extent the Aegean islands. The high cargo movement of Thessaloniki is due
to the transport of goods to neighboring countries (Yugoslavia and Bulgaria).
The increased cargo movementin Volos is due to the transport of goods from Europe
to the Middle East (Syria). The high number of passengers arriving in Patra and
Igoumenitsa is due to the increased arrivals of tourists from Italy with car-
ferries during the summer months.
Land Use
A large proportion of the Greek coast with steep slopes and cliffs has not
been developed. The remainder is composed of deltaic plains, narrow coastal
plains, and pocket beaches. In many cases, these coastal zones were developed
in a very disorderly fashion before the state could intervene. As a result of
this anarchic development, construction in the coastal zone has, in many
instances, upset the equilibrium that exists in the coastal environment.
In several coastal lowland areas, particularly in the Messologi region,
there are extensive salt works. In other parts of Greece, like the plains of
Thessaloniki, Sperkhios, Amvrakikos, Evros, and southern Peloponnessos, there are
large areas with rice fields. In the Argolida-Messinia-Lakonia area, northern
Peloponnessos, Volos, and Crete, there is extensive cultivation of fruit-bearing
trees and horticulture. Olive trees are found everywhere in Greece, but the
main producing areas are in Amfissa-Itea, western and southern Peloponnessos
(Kalamata), and Crete.
The often thoughtless exploitation of water resources in coastal areas with
water pumps and wells has led to a serious drop of underground water tables and
simultaneous advance of saltwater. This has led to the degradation of
underground waters which, in turn, has affected the quality and quantity of
agriculture in the coastal zone. This problem will only be exacerbated with
rising sea level and more frequent droughts resulting from global warming.
Fisheries
Aquaculture is a very important activity in Greece. The indented coastline
and its great length complement aquaculture development. Important areas of
coastal fisheries are the lagoons of Messologi, Amvrakikos gulf, and Porto Lagos.
Fishing boats are usually of small displacement and the production is intended
for domestic consumption (Table 3). Exports are minimal.
In recent years, a great effort has been directed to the reorganization and
modernization of fisheries in the various lagoons of Greece to make them
profitable, in both quality and quantity.
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Table 2. Number of Arriving Boats, Passenger and Cargo Movement in Selected
Harbors of Greece (1986)
Passenaers
Harbor
Pireas
Thessaloniki
Patra
Iraki io
Rodos
Kerkyra
Alexandroupolis
Kavala
Volos
Kalamata
Igoumenitsa
Khania (Souda)
Khalkis
Syros
Rafina
TOTAL
Arrivals
of
vessels
17,600
2,400
2,250
2,030
1,980
2,180
830
880
3,330
200
2,080
200
800
2,100
1,700
140,000
Embarking
(1000s)
2,701
11
492
382
128
114
44
15
107
--
86
180
--
110
330
9,256
Disem-
barking
(1000s)
2,664
10
584
385
124
147
42
16
105
--
108
182
--
110
328
9,297
Carao
Loaded
(IO3 tons)
2,125
2,452
219
428
213
19
335
1,662
3,714
16
3
141
1,635
37
77
38,703
Unloaded
(IO3 tons)
4,825
8,024
349
1,313
394
165
115
645
2,837
156
254
318
818
103
81
46,203
Table 3. Fishing Vessels and Fish Caught in Greece (1986)
Total
Coastal Fisheries
Number of fishing
vessels
Fish caught (tons)
6,380
112,700
5,500
35,700
89.7
31.7
Fishing could be vulnerable to sea level rise both because the fishing ports
and other activities are located in low areas, and because the loss of wetlands
would reduce fish populations.
Coastal Development
Human intervention in the deltaic plains, the lagoons, and the wetlands is
not very extensive. Shore alignment and protection structures are found in some
lagoons like those of Amvrakikos, Messologi, and Porto Lagos (Vistonida).
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Maroukian
Important shore protection structures (against erosion) are found only in the
area of Messologi and the deltaic plain of Thessaloniki.
The state has spent very little on the development and protection of the
coastal environment. Beside harbor works in various locations of Greece and the
construction of some coastal roads, state assistance that addresses coastal
problems is of only local significance.
Private investment in the coastal region, however, is at high levels. In
the last decades, thousands of summer cottages have been constructed in many
parts of the Greek coasts. This rapid settlement development is frequently
accomplished without any planning and is many times done illegally. Another
important development along the Greek shores is the construction of big vacation
complexes with hotels and all kinds of sports and recreational facilities.
Finally, a variety of industrial complexes, like oil refineries, aluminum
smelters, steel works, shipyards, and dockyards, are located in coastal zones.
All of these activities will be vulnerable to a rise in sea level unless some
remedial actions are taken.
CONCLUSION: THE NEED FOR A GOVERNMENT POLICY
The first attempt at a comprehensive solution to the question of coastal
management and protection was made with Law 2344/1940. There followed many
amendments and additions, mostly relating to land use and management of the
coastal zone.
Following the increasing interest in the protection of the environment in
recent decades, a national coastal management program was started in 1980. The
implementation of this program was entrusted to the Ministry of Physical Planning
and Environment. The primary aims were as follows:
1. To prepare a uniform and complete program for the development and
management of the coastal zone; and
2. To study the following:
• Settlement patterns and deterioration of the coastal zones;
• The frequent irreversible destruction of the natural ecosystems and
landscapes;
• The reduction of productive agricultural land;
• The exhaustion of marine resources due to pollution and
overexploitation; and
• The inaccessibility of the beach due to continuous land ownership
along the beach.
Unfortunately, this program never had the financial resources necessary to
carry out its original mandate. Recent administrations have shown little
interest in spending additional money on the project, and there has not been a
large outcry from the public to revive this initiative. Nevertheless, the wave
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of concern for the environment sweeping across Europe is beginning to be felt in
Greece, and the protection of our coastal heritage is an obvious priority.
Clearly, any new national research, planning, or management efforts to
protect the coastal1 environment should estimate the likely impacts of sea level
rise; calculate the costs of alternative response strategies such as retreat and
holding back the sea; and compare costs for alternative policy implementation
dates between today and 2020, particularly in the case of land-use restrictions.
Such an assessment will require a technical panel including coastal geologists,
engineers, planners, economists, and public works officials.
In the narrow sense, we can afford to ignore accelerated sea level rise for
a while, because the consequences are a few decades away, and a culture that has
survived as long as ours is hardly likely to perish at the hands of a changing
climate. But, by the same token, since we know that there will be a Greece for
centuries to come, is it proper to ignore the adverse impacts that our actions
today may bequeath to future generations? Compared with the potential
environmental, cultural, and economic losses that could result from a rise in sea
level, the cost of developing a national response strategy would be small.
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APPENDIX: DETAILS OF COASTAL CLIMATOLOGY, CURRENTS, TIDES,
AND TSUNAMIS IN GREECE
PRECIPITATION
The general characteristic of the geographical distribution of mean monthly
temperatures is a decrease with higher latitudes. July and August are exceptions
because they present great temperature homogeneity. Generally, the western
coasts of Greece are a little warmer than the eastern coasts during the winter
months. The opposite is true during the summer months. Both the temperature
difference and the summer duration increase with higher latitudes. The eastern
coasts experience a more continental climate.
The precipitation system that prevails all over Greece is of the
Mediterranean type and is characterized by winter precipitation and summer
drought (Table A-l). During the warm period of the year, rainfall increases from
south to north because of the increasing continental ity of the climate. The mean
annual precipitation is 706.8 mm.
Table A-l. Mean Monthly Precipitation in Greece (mm)
Month Amount Month Amount
J
F
M
A
M
J
112.5
80.9
70.4
41.5
33.9
21.4
J
A
S
0
N
D
12.4
10.4
29.8
77.4
92.8
123.4
The maximum 24-hour period precipitation occurs during autumn and winter
months and rarely during the remaining months of the year, e.g., Lefkas 248.0 mm
in November, and Rodos 320 mm in January. The largest number of days of
precipitation are observed during the month of January.
The greatest snowfall occurs in January and February, followed by December
and March. The mean number of days with snow increases with increasing latitude,
distance from the sea, and from west to east.
When a low-pressure storm arrives from the west, the weather over Greece
becomes cloudy with a tendency toward rain and storms over the Aegean Sea while
wind intensity abates. Finally, storms from the south occur when a low pressure
from the west passes over the Balkan Peninsula, north of the Aegean Sea.
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WINDS
In general, the most prevalent winds blow from the northern quadrant. The
highest wind speeds occur in the open seas, mostly in the central Aegean Sea, in
the Ionian sea, and between Crete and Peloponnessos. In the summer, the Etesian
winds blow from the north.
The direction, intensity, and duration of the winds, along with the fetch
length, determines the height of waves. The general circulation of winds in the
Greek seas depends on the distribution of the atmospheric pressure, which is
affected to a great extent by the local influences of the distribution of the
seas and the uneven setting of the mountain masses.
In winter, we have northerly winds, which are the result of high-pressure
cells covering the Balkans and northern Russia. These winds become very intense
if a storm occurs over Greece when cyclonic depressions move over or move north
of the Greek seas. This results in very intense southerly winds.
In summer, the prevailing winds over the Greek seas are northerlies, called
Etesian. They are seasonally very constant, being northernly and northeasternly
in the Aegean and northwesternly in the Ionian and western Greece. Their
dominance is interrupted in fall when southerly winds start becoming more and
more frequent, thus keeping coastal temperatures high long after summer is over.
The temperature of the surface of the Greek seas presents a normal annual
fluctuation with a minimum in February and a maximum in August (Figure A-l). The
annual temperature range of the surface water fluctuates between 9.8°C in the
south Aegean Sea and 11.5°C in the north Aegean Sea. The warmest seas of Greece
are found in the north Aegean and the Ionian Seas all year round.
According to observations by the Hydrographic Service of Greece, the highest
mean annual sea surface temperature is located around Rodos (19.7°C) and the
lowest near Alexandroupolis (15.5°C).
CURRENTS
The currents in Greece are of three types:
• Local currents,
• Tidal currents, and
• General currents of the open sea.
Local currents are directly dependent on the configuration of coasts, depth,
the bottom relief, and the direction and intensity of winds.
The main tidal currents occur at the Strait of Evripos, the Corinth Canal,
the Strait of Lefkas, at the entrance of Amvrakikos gulf, and at Rio-Antirio
Narrows.
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Figure A-l. Mean monthly sea surface temperatures (°C) of the Greek seas,
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Mediterranean
The open sea currents generally follow an east-west direction. The current
originating from the Black Sea determines the motion of the north Aegean currents
giving a general east-west direction and a north-south direction in the western
Aegean. The Black Sea current, as it comes out of the Dardanelles, has a speed
of up to 2.5 knots and is directed to the south.
In the central Aegean, there is an anticlockwise motion, while in the
southern Aegean there is a clockwise movement around the island of Crete. Along
the east Aegean, there is a south to north current. In the Ionian sea, the
general motion of the currents is from south to north except near Kerkyra (Corfu)
and Lefkas, where the current near the coast runs from north to south.
TIDES
Most stations use automatic tide gauges, and the remainder use tide poles
(Table A-2).
Table A-2. Tide Stations in Greece
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Aedipsos
Alexandroupolis
Aliverion
Amfiali
Argostolion
Volos
Gythion
Igoumensitsa
Iraki ion*
Thessalonikr
Isthmia
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Kavala*
Kalamata*
Katakolon
Kerkyra
Leros
Lefkas*
Limnos
Mytilini
Sal amis
Patra*
Pi reefs*
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
Posidonia*
Preveza*
Rodos
Skiathos
Souda (Khania)*
Styl i s
Syros*
Khalkis (north)*
Khalkis (south)*
Khios*
Note: Stations with a cross use automatic tide gauges; all others use tide
poles. Stations 4 and 11 have been discontinued. Source: Zoi-Morou (1981).
During their installation, the leveling of the stations is linked to the
national geodetic system of the country by the Greek Army Geographical Service.
It is possible to divide the Greek seas into three large areas (Table A-3).
1. The north Aegean Sea with tidal ranges between 0.11 and 0.25 m;
2. The south Aegean Sea with tidal ranges between 0.05 and 0.08 m; and
3. The Ionian Sea with tidal ranges between 0.05 and 0.18 m.
TSUNAMIS
Tsunamis in Greece are rare. Their zones of origin coincide with the
seismogenic zones of the external island arc of the Greek microplate (Ionian
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Maroukian
islands, Crete, Rodos) as well as with the internal volcanic arc (Corinth-Megara,
Aegina, Milos, Santorini, Nisyros, Kos).
Along these zones there occur numerous earthquakes which every few years
reach an intensity of *6 on the Richter scale. Owing to the highly irregular sea
bottom terrain, there is a possibility of submarine landslides which can
sometimes produce tsunamis.
The tsunamis have not been systematically studied in Greece. The first
study was done in 1956 by seismologist Galanopoulos when a tsunami-like
phenomenon occurred in the southeastern Cyclades, following a great earthquake
on July 9, 1956 (36.9°N, 26° E, H = 03:11:38, M = 7.5). The tsunami owed its
genesis to a submarine landslide on the steep slopes of the southeastern shores
Table A-3. Maximum, Mean, and Minimum Tidal Ranges (in Meters) at Tide Stations
in the Ionian and Aegean Seas
Station
Maximum Range Mean Range
Minimum Range
Ionian Sea
Preveza
Lefkas
Katakolo
Patra
Kalamata
0.28
0.30
0.67
1.05
0.58
0.05
0.11
0.08
0.18
0.11
0.01
0.01
0.01
0.01
0.01
South Aegean
Syros
Khania (Souda)
Irakiio
Leros
North Aegean
Thessaloniki
Kavala
Alexandroupolis
Limnos
0.32
0.25
0.58
0.52
0.94
0.96
0.65
0.60
0.05
0.06
0.08
0.06
0.20
0.25
0.13
0.11
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
Source: Zoi-Morou (1981).
of Amorgos Island (36.8°N, 26.2°E). The seismic sea wave caused sea level to
fall up to 3 meters and rise 2.5 meters. The wave train affected almost all the
harbors of the south Aegean. Galanopoulos prepared a map with the sources of
known tsunamis which proved to be destructive in historical times (Figure A-2).
A second tsunami was generated by an earth slump, set in motion without
shock, in the area of Aegion in northwestern Peloponnessos when a massive
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Mediterranean
slumping, estimated to have a mass of 57,000 cubic meters, subsided 5-44 meters
below the sea level and the coastline in some parts receded up to 500 meters
inland (Comninakis et al., 1964). Even though there was no earthquake at the
moment, the slump occurred (7 February 1963), it was preceded by seven local
earthquakes west of Aegion on 2 February 1963.
Earthquakes accompanied
Tsunamis
27-
26*
Figure A-2. Sources of tsunamis that have affected the coasts of Greece from 479
B.C. to A.D. 1956.
BIBLIOGRAPHY
Comninakis, P., N. Delibasis, and A. Galanopoulos. 1964. A tsumami generated
by an earth slump set in motion without shock. Annales Geologiques des pays
Helleniques 16: 93-110 (in Greek).
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Dagre, D., and Lambrou, D. 1981. Study of the legislation about "aegialos" and
"paralia." Athens: Technical Chamber of Commerce, (in Greek).
Galanopoulos, A.G. 1957. The Seismic sea wave of July 9, 1956. Praktika
Akadimias Athinon 32: 90-101 (in Greek).
Galanopoulos, A.G. 1960. Tsunamis observed on the coasts of Greece from
Antiquity to present time. Annali di Geofisica, 13 (3-4): 369-386.
Hydrographic Service. PILOT (Ploigos), Athens (in Greek).
Volume A. Western coasts of Greece 1971, with announcements in 1983 and
1986.
Volume B. Southern coasts of Greece 1976.
Volume C. Northeastern coasts of Greece 1947, with announcements in 1983
and 1987.
Volume D. Northern and eastern coasts of Greece, 1987.
Kamkhis, M. 1981. The development and protection of the coastal zone in Greece.
Proceedings of the Conference on the Development (Growth) of Greece, Athens, III.
pp. 152-156.
Kotini-Zabaka. 1983. Contribution to the Study of the Climate of Greece by
month. Doctoral dissertation. Thessaloniki, Greece: University of Thessaloniki
(in Greek).
Maroukian, H. 1989. Sea level in the past, present and future. Proceedings of
the First Panhellenic Geographical Conference, 2, 1987, Athens.
Ministry of the Environment, Physical Planning, and Public Works. Program for
the delineation of wetlands of the RAMSAR agreement. 1986. Athens: Ministry
of the Environment, Physical Planning, and Public Works (in Greek).
i. Evros delta
ii. Lake Mitrikou
iii. Lake Vistonida-Porto Lagos
iv. Axios-Loudias-Aliakmon delta
v. Nestos delta
vi. Kotyhi lagoon
vii. Messologi lagoon
viii. Amvrakikos gulf
Moutzouris, C., and Maroukian, H. 1988. Greece. In: Artificial Structures and
Shorelines. H.J. Walker ed. New York: Academic Publishers, pp. 207-215.
National Statistical Service of Greece. 1982. Actual population of Greece
according to the April 5, 1981 census, Athens: National Statistical Service of
Greece (in Greek and French).
Zoi-Morou, A. 1981. Tide data of Greek harbors. Oceanographic Study no. 13,
Athens: Hydrographic Service (in Greek).
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IMPACTS OF SEA LEVEL RISE ON TURKEY
PROF. DR. OGUZ EROL
Institute of Marine Sciences and Geography
University of Istanbul, Turkey
ABSTRACT
The low coastal belt of Turkey is occupied by intensive agricultural land
use, and most of the cities, towns, and villages are found along the lowland
coasts. But most of the population is settled on the high cliff sections of the
coast. The ports are principally established at a point where the stretches of
sedimentary coastline meet the relatively higher bedrock ground. Some parts of
the harbor cities and industrial establishments have extended onto the low
coastal plains, especially during recent years. Because they are not wide areas,
these parts may be subject to disruption as sea level rises. Artificial coastal
protection is not present along this low coastline because there is mainly no
need for it at present.
The common assumption in Turkey that sea level is constant is not shared
by the scientists, and for good reason. The Turkish shores have fluctuated
several times during the Holocene, and sea level has been rising at least for
the past 4,000 years. But because the rising sea has been balanced by
sedimentation and tectonic uplift, for most practical purposes it has been
reasonable to assume that sea level is constant. But if global warming is likely
to cause a 50- to 100-cm rise in the next century, the time is now to recognize
this issue in the coastal decisionmaking process. In Turkey, some government
offices are responsible for planning and construction of harbors and other
coastal establishments. Some municipalities of coastal cities are also
responsible for managing low coastal plains, but none of them is yet dealing with
a future sea level rise. Will it take a dramatic event to draw the attention
of policymakers, or can they respond to scientific information?
INTRODUCTION
When one asks "What will happen on the Turkish coastline if the sea level
rises?", the answer at first seems simple: not much, because the Anatolian
Peninsula is a tectonically uprising block, and, except in the deltaic areas,
there are no extensive lowland areas around it. But if sea level rise
accelerates, the hidden dangers will emerge. Because tides and storms are small,
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many coastal establishments and settlements have been built within 2 meters of
sea level and will eventually be inundated unless dikes are built. But many
fishing villages, such as Meset Limani illustrated in Figure 1, could not afford
dikes, and an inland migration would not be feasible if traditional activities
were to continue.
In the past, the main causes of shoreline changes have been sea level
fluctuations due to tectonic uplift and subsidence, alluviation, and human
activities (Erol, 1983, 1988). The most important recent changes have been in
deltas (Erol, 1983; Bird, 1985), which in some cases have advanced 40 kilometers
seaward (Erol, 1976). Because of changes in river courses, Ephesus, Priene
Miletus, Kaunos, and many other ancient harbors have been abandoned.
Nevertheless, tectonic uplift -- often associated with earthquakes'--^has also
been important in some cases. For example, the city of Seleukeia Pieria'in Hatay
was completely abandoned after Byzantine times (Erol, 1963; Pirazzoli et al.,
1989).
No one has assessed the impacts of a 50- to 200-cm rise in sea level.
Nevertheless, a number of expectations seem reasonable. First, in the high rocky
cliff coasts, the rising sea level will not cause great changes or shifts of the
coastline, but the rate of cliff recession will accelerate, increasing the
frequency and extent of landslides and destroying portions of many coastal roads.
Second, along low, eroding, soil cliffs, there may not be immediate changes, but
erosion will eventually result. Because these areas are already densely
populated narrow terrace strips, displacement of destroyed coastal establishments
will become a serious problem, and protecting them from the sea will cause
erosion elsewhere. Finally, along deltaic coasts that are advancing seaward
today, rising sea level will reverse the shoreline change, and coasts will begin
to retreat. The geomorphological result of this will be a thick alluviation that
may bury relatively new deltaic soils and perhaps interrupt agricultural activity
on the deltaic plain as much as droughts do today.
Many coastal establishments would be displaced as a result of these changes.
In the high rock cliff areas, the increased activity will influence the
settlement points, roads, etc. Since the places at the top of the cliffs are
already scarce, rebuilding settlements elsewhere will be difficult if not
impossible. In the narrow strip of low soil-cliff terrace areas, the
displacement of ruined coastal establishments, especially tourist places, will
be several times more expensive. In the low deltaic areas, which are already
overcrowded, displacing the populations may be politically impossible,
necessitating expensive coastal protection. Even where it is feasible, it will
encroach upon important agricultural areas, which is already happening due to
population growth. In Turkey, the art of life may have to change.
Many cultural sites would also be at risk. Besides the modern settlements,
most of the ancient harbors and cities would be covered by seawater. Because
of sedimentation, they would be buried, and access to these ruins would be much
more difficult. Some of them would be destroyed by increased wave activity.
Because of their great number, moving the ruins would be practically impossible,
and in any event, it would change their character.
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Figure 1. A typical Turkish fishing town. While towns like this clearly lack
the resources to hold back the sea, retreat is not a viable option either.
In Turkey, the State general directorates and offices responsible for
planning and constructing airports and harbors are connected to the Ministry of
Construction and Settlements. In addition to these General Directorates, the
State Planning Department and some municipalities of the coastal cities have
interests in the low coastal belt of Turkey.
None of these agencies is dealing yet with the issues and problems that will
accompany future sea level rise. When asked about the problem, they generally
minimize its significance. Even coastal engineers, who would seem more
predisposed to incorporate technical information, are designing coastal
establishments without regard for future changes.
In the Turkish law for coastal protection, sea level is accepted as an
"unchanging" boundary between the land and sea. Even without the greenhouse
effect, we know that such a definition is technically inaccurate, but in the past
it has not mattered as other processes offset rising sea level. But in the
future, keeping this definition in our coastal policy will yield irrational
results, as the United States and other countries with higher current rates of
relative sea level rise have already seen (Titus et al., 1985).
The remainder of this paper summarizes the natural environment of Turkey
and human activities along its coasts.
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THE NATURAL ENVIRONMENT OF TURKEY
Climate and Waves
Turkey lies between the middle latitudes and the Mediterranean macroclimatic
zones and has a transitional character. The climate of the Black Sea is mainly
under the influence of northerly winds that usually blow as gales. Because of
the long fetch of the Black Sea and the absence of intervening islands, large
waves strike the shore; hence high coastal cliffs and shingle beaches at the
mouths of short mountain rivers are eroding. Details of wave heights and water
temperatures are in Appendix 1.
Coastal Geomorphology
The coast of Turkey has developed under the influence of (1) the
geomorphology of the mainland -- that is of the Anatolian Peninsula and
especially of the North Anatolian and Taurus folded mountain chains and the belt
of faulted central plateaus; and (2) the submarine relief of the sea basins
surrounding the peninsula. The coastline of Turkey may be divided into three
main groups: (1) retreating cliffed coastlines on rocky and soil material (5,752
km), (2) advancing sandy depositional soil (1,546 km), and (3) advancing, partly
swampy deltaic soils (1,035 km).
High Rocky Cliff Coastlines
High rocky cliffs are found mainly on the north and south Anatolian
coastlines, which run parallel to the folded mountain chains. There are,
however, some shorter stretches of similar coastline on the faultline coasts of
the Aegean and Marmara Seas. This type of high rocky cliff rises sometimes a
hundred meters above the sea. These cliffs are interrupted by river mouths with
limited shingle beaches on the north and south Anatolian coastlines. On the
Aegean coastline, on the other hand, the rocky cliff coasts of fault mountains
are relatively short and are interrupted by several deltas.
Generally, the high rocky cliff coasts are slowly eroding. At the foot of
the cliffs, the coastal platform is usually very narrow or absent. Therefore,
building highways along the coastline is extremely difficult, and the roads are
located on the top of the cliffs if possible. Because of the humid climate
during all seasons of the year, landslides are common on the Black Sea coastal
strip. However, because of the minor drop in sea level following the Climatic
Optimum of the middle Holocene, narrow sandy beaches have developed at the foot
of these cliffs. In the event of a future sea level rise, these narrow sandy
beaches will be covered by water again, exposing cliffs to waves, which will
accelerate their erosion.
The Low Soil Cliff Coastlines
Low (2-meter elevation) and medium-high (10- to 20-meter elevation) cliffs
composed of soft sediment are found at the base of many Pleistocene terraces.
For the most part, the coastal belt is a narrow strip between the sea and the
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mountains. Because these coastal belts have been ideal for settlement, tourist
and industrial establishments, and road construction, they are densely populated.
Although this narrow strip has a few meters of relief, the increasing exposure
to waves will cause erosion, and shorefront establishments will be ruined at an
increasing rate.
The Low Unconsolidated Coastlines
These low stretches are found especially on the deltaic coastlines. They
include wide sandy beaches, beach rock, lagoons, tidal flats, and coastal dunes.
Because rivers are supplying large amounts of sediment, these shores are
advancing into the sea today. Accelerated sea level rise, however, would reverse
this process.
Especially on the north and south Anatolian coastline, the small deltaic
unconsolidated coastlines consist mainly of gravel and shingle beaches. This
is the result of the influence of the strong waves and coastal currents.
Although there are no barrier islands in Turkey, some coastal spits have
developed at the mouths of rivers and bays; some have formed along the foots of
cliffed coasts. These low areas are very vulnerable to both inundation and
erosion due to sea level rise.
Coastal Dunes, Wetlands, and Lagoons
Turkey has well-developed coastal dunes, especially along the western Black
Sea coast and in the deltas of the Aegean and Mediterranean Seas. These natural
barriers to storms would provide some defense against the consequences of sea
level rise, at least in the short run. Elsewhere, beach rock has developed
along numerous low soil cliffs.
Wetlands are mostly confined to relatively narrow areas in the Kizilirmak,
Yesilirmak, Seyhan, and Ceyhan Deltas and in other low coastal reaches along the
Aegean Sea, most of which are associated with lagoons. There are no coral reefs,
mangroves, or saltmarshes in Turkey.
Lagoons are found mainly behind the coastal spits of the deltaic areas of
Turkey. There are, however, lagoons in some inlets with high- and low-cliffed
coasts, too. The lagoons of the Turkish coastline are used partly as salt pans
and fish ponds. The former lagoons of Kucukcekmece and Buyukcekmece have
recently been converted to water reservoirs for the city of Istanbul.
Genuine tidal estuaries are not found in Turkey, although some ria-type
inlets are present. The ancient harbor of Istanbul, which is called Halic, is
an example of this type of ria.
LATE PLEISTOCENE AND HOLOCENE SEA LEVEL CHANGES
Recent sea level changes have played a very important role in the coastal
geomorphology of Turkey. The influence of young tectonic subsidence and uplift
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phenomena are observed at several points of the coastline. Alluviation, deltaic
subsidence, and climate changes must be added to this group. These kinds of
coastal processes are controlling the prograding and retrograding stretches of
the coastline.
Finding some unchanging coastline stretch in Turkey is really difficult.
Generally, the upper Pleistocene (Tyrrhenian) terraces with their fossils are
less than about 250,000 years old, and they are found at elevations between 10
and 80 meters in different coastal places. Some coastal terraces and their
fossils at about 6 to 10 meters must belong to the last interglacial period --
that is, about 100,000 years ago. Moreover, on the recent coastline of Turkey,
except prograding deltaic coastline stretches, there are traces of elevated
former sea levels of 200 cm (about 6,000-8,000 years ago), 100 cm (about 2,000-
2,500 years ago), and 50 cm (about 1,400 years ago) (Kayan et al., 1983; Laborel,
1989; Pirazzoli et al., 1989). If we reconstruct these former traces, we may
determine what will happen in the future. These kinds of studies must be
extended for all the Turkish coastline.
CULTURAL AND ECONOMIC FEATURES
Demography
Most of Turkey's population of 50 million is well out of danger from a
rising sea. Of the 399 cities and towns in Turkey, more than half the population
lives less than 100 meters above sea level. Unfortunately, the lack of vertical
resolution on topographic maps makes it impossible to estimate the portion of
the population that lives within a few meters of sea level.
Ports
During ancient times, there were several harbors and cities on the coastline
of Turkey, generally at the point where the main trade ways of the country ended,
usually on a deltaic plain next to a low soil-cliff (Erol, 1976, 1983, 1989;
Akurgal, 1970). The presence of lagoons facilitated the establishment of
primitive landing places that were later converted to harbors. Many of these
harbors and cities had to be abandoned because deltaic alluviation, sea level
changes, earthquakes, and tectonic uplift shifted the shorelines (c.f. Erol,
1963, 1983; Kraft et al., 1977, 1980a,b, 1982; Kayan, 1981, 1987).
In modern times, the ports have expanded and situated on much broader
grounds. In addition to the historical ports, several smaller fishing harbors
and shelters with breakwaters have been built. According to Erol (1988), the
total number of the artificial structures of Turkey is as follows:
Large commercial harbors 12
Small harbors 115
Shelters with breakwaters 9
Abandoned ancient harbors 44
Major coastal protection works 6
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In the building of all these coastal establishments, unfortunately, sea
level and other environmental conditions are assumed to be constant. In reality,
even some of the new harbors have been destroyed or covered by sediments, often
within a period less than 10 years. Warning the policy makers in Turkey has been
extremely difficult. In some cases, sea level rise may help to offset the
sedimentation processes that have forced port abandonments. However, this would
be merely a fortuitous coincidence.
Other Land Uses
The coastal zone has Turkey's most fertile agricultural lands and a mild,
humid climate. In recent times, coastal tourism and yachting have experienced
explosive growth. The tourist establishments were first built on the narrow
beach strip, but now they are backing up to the country's most valuable inland
agricultural fields. The land has also been expanded toward the sea with walls,
embankments, quays, etc. But as noted previously, the coastal lowland strip of
Turkey is narrow at the base of inland mountains. A rise in sea level would
force the nation either to give up agricultural lands to facilitate landward
resettlements or to spend large amounts of money on erecting coastal defenses.
Fisheries
Fishing has been an attractive livelihood for the people who have lived on
the Turkish Mediterranean coastline since historic and even prehistoric times.
For example, in 1923, there were about 30 fish ponds on the Anatolian coastline
with a yearly production of 9,000 tons of fish products. However, in the area
of the Marmara Sea and Straits, the local character of fishing developed somewhat
differently. This is because fish from the Black Sea migrate toward the Marmara
and Aegean Seas during the autumn and winter months, as the Black Sea waters
become cooler. In the early years, the migrating fish were staying partly in
the Marmara Sea during the winter season. But in recent years, because of water
pollution and other hostile conditions, they prefer to continue their migration
to the north Aegean Sea. Those fish return to the Black Sea during spring and
summer seasons. So fishermen are following the fish and are catching them,
especially in the Anatolian coastal waters of the Black Sea, at the entrance of
the Bosphorus, and in the Marmara and north Aegean Seas. Under these
circumstances, fish production has increased yearly from 79,000 tons (1952) to
532,000 tons (1985). The percentage of this production is distributed as
follows:
Black Sea 80
Marmara Sea and Straits 12
Aegean Sea 5
Mediterranean Sea 3
Climate change could affect the fisheries in many ways. Although Turkey
does not have extensive wetlands, many of the fish caught there spend part of
their lifetimes in the marshes found elsewhere. Warmer temperatures could
encourage some of the fish that migrate out of the Black Sea during the winter
to remain there longer. On the other hand, warmer temperatures might amplify
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pollution problems. The unknown impact of global warming on seasonal
precipitation, river flow patterns, and currents also could be important.
CONCLUSION
An evaluation of the implications for Turkey leads one to realize that
worldwide, sea level rise would be a serious problem. Turkey would appear to
be one of the countries least vulnerable; yet even here, the consequences could
be severe.
Clearly, policy makers need to take sea level rise into account. Even in
the short run, doing so would help to ensure that new development is consistent
with current environmental changes. In the long run, it is important both
because our valuable coastal strip is very narrow and because it would help
introduce policy makers to the other consequences of the greenhouse effect, such
as hotter summers and more droughts, which in Turkey could be far more
devastating.
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APPENDIX: CLIMATOLOGY AND CURRENTS OF TURKISH WATERS
The climate conditions that control the recent phenomena are determined by
the main physiographic features. The country lies between the middle latitude
and Mediterranean macroclimatic zones and has a transitional character. The
Middle European and Mediterranean climates alternatively dominate in the Black
Sea region, whereas only the Mediterranean climate dominates south of the Taurus
Mountains and in the Aegean Sea region. The climate of the Marmara region is
transitional between the Black Sea and Mediterranean types. In the central part
of the Anatolian Peninsula, which is between the North Anatolian and Taurus
Mountains, a continental plateau type of Mediterranean climate is characteristic.
The types of coastal regions found in Turkey are shown in Figure A-l.
Black Sea
The climate of the Black Sea coast of Turkey is mainly under the influence
of northerly winds (air masses) that usually blow as gales called Karayel (black
winds) in Turkish. Because of the long fetch (i.e., distance over which waves
can form) in the Black Sea and the absence of islands along this somewhat
straight coastline, the wave energy is considerable. Thus, rapidly retrograding
high coastal cliffs and shingle beaches at the north of the short mountain rivers
are predominant along this coastline. The sandy beaches and their related dunes
are also developed under the influence of these strong northerly winds.
The heavy rainstorms and strong northerly winds that dominate the winter
climate (temperature 0 to 7°C) of the Turkish Black Sea coasts yield to mild
winds during the summer. Except for some rare winds in the eastern part of the
coastline, the influence of the southerly winds is extremely rare in the Black
Sea coastal strip of Turkey. Therefore, the summers are also mild (19 to 23°C),
cloudy, and rainy in this area. The temperature of the seawater is cool (15 to
16°C), and the surface of the Black Sea is mainly rough.
Marmara Region
The North Anatolian Mountain chain usually prevents the penetration of the
marine climate influences inland—that is toward the main plateau of Central
Anatolia, especially in the middle and eastern parts of the country. But in the
west, toward the Marmara Region, the climatic influence of the northerly winds
and air masses can easily penetrate to the south during the winter and summer
seasons. But usually these northerly weather conditions alternate with southerly
conditions. In Istanbul, for example, the southerly gales alternating with
northerly winds have an important effect. The Maramara Region with cold (1 to
6°C) rainy winters and cool (22 to 23°C), windy summers is a transitional area
between the Black Sea and the Mediterranean environments. These climate
characteristics as well as sea currents in the straits are also controlling the
physical properties of the water masses in the Marmara Sea.
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Mountain ridges
Deltaic areas
Figure A-l. Types of coastal regions of Turkey: (1) Black Sea type; (2) Maramara
type; (3) Aegean type; and (4) Mediterranean type.
Aegean Sea
The climate in the Aegean Sea is a transitional blend of the climate between
the Black Sea and the Mediterranean Sea. But there the Mediterranean climate
dominates mainly during the summer, whereas the Black Sea conditions dominate
during the winter in the Marmara region. However, because of the northerly cool
to warm (26 to 28°C) summer winds in the Aegean Sea, the summers are cooler than
the eastern Mediterranean area, and this climate characteristic also controls
the summer seawater temperatures (16 to 19°C) of the Aegean Sea.
Along the Mediterranean coast of Turkey, the Mediterranean climate
dominates. Warm (24 to 29°C), dry, and calm weather conditions are very
conducive to the development of biogenetic coastal forms as well as dunes and
beach rock. The rainy, cool to warm (9 to 11°C) winters and wave activity cause
the formation of wide, sandy beaches. The excessive summer evaporation causes
cementation in the beach sands or calcite concentrations in the coastal to inland
soils. Investigations have shown that similar conditions were prevalent in this
part of the coastline during the Holocene and even during the upper Pleistocene
(Erol, 1983; Kayan et al., 1983; Laborel, 1989).
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Marine Hydrology
Water Masses
The Black Sea in the north and the eastern Mediterranean in the south are
Turkey's two main sources of water masses. The water masses originating from
the Mediterranean Sea are principally warm (21.54°C on the surface) with high
salinity (39.15 parts per thousand), and the water masses in the Black Sea are
cool (8 to 15°C on the surface) with low salinity (18.36%). In the area of the
Marmara Sea and Straits, there are transitional conditions between the Black Sea
and Mediterranean masses. Indeed, the warm and saline Mediterranean water flows
on the surface along the Anatolian coast toward the north in the Aegean Sea
(Figure 3) and meets the cool and less saline Black Sea water. There the
lighter, less saline Black Sea water flows on the surface toward the south, and
relatively heavy saline Mediterranean water flows under it toward the north into
the Dardanelles Strait. These layered surface and deep-water masses also occur
in the Marmara Sea and Bosphorus Strait.
The mean surface temperature in the Marmara Sea is 15 to 17°C.o The surface
temperature of the seawater is 8 to 9°C in January and 24 to 26°C in August.
The salinity of the surface waters is 23.47%, and that of the deep waters is
38.64%.
The characteristics of deep seawaters are also influenced by the surface
conditions. In the eastern Mediterranean, there are four layers of water masses
(Yuce, 1987): (1) surface waters of Atlantic origin (temperature 21.54°C,
salinity 39.15%); (2) intermediate eastern Mediterranean waters (temperature
15.5°C, salinity 39.15%); (3) deep water (temperature 12.6°C, salinity 38.4%);
and (4) Bottom water.
In the Black Sea, there are three layers of water masses: (1) surface water
in the upper 200 m (temperature 8 to 15°C, salinity 18%); (2) transitional water
layer; and (3) deep water (temperature 9°C, salinity 22.5%).
The surface temperatures drop below the freezing point, especially in the
north and western coasts of the Black Sea, and ice masses may penetrate through
the Bosphorus to the northern Marmara Sea (Erinc, 1985).
Currents
The characteristics of the currents in the straits and Marmara Sea are
principally influenced by the salinity and temperature differences between the
Black and Mediterranean Seas. The water volume brought by rivers into the Black
Sea Basin is great, and because of this, the surface level of the Black Sea is
50 cm higher than that of the Marmara Sea. This is another reason for the
currents in the straits.
The winds are a significant influence on the currents in the Bosphorus.
Normally, the surface current in the Bosphorus is from north to south. Its
velocity is directly under the control of the dominant northerly winds, and it
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Mediterranean
may reach up to 9-10 km/h. But it may decrease or completely disappear when the
southern winds blow persistently for a few days, especially during the southerly
gales. In this case, the warm and saline Mediterranean deep water may rise to
the surface. This kind of unusual sudden change causes mass mortality of fish
that live in the upper, less-saline, cool waters and also of fish that live in
the deeper, saline, and warm water layers.
Because of the strong underwater currents, the bottom of the Bosphorus is
partly bare of fine sediments or is covered in some places by larger particles
of sands and even shells. The water exchange between the Black and Mediterranean
Seas has been studied by several authors since the 19th century (e.g., Makarov,
1885; Wharton, 1886; Ullyott and Ilgaz, 1946; Pektas, 1953; Yuce, 1985, 1987b).
The influence of the currents in the area of the straits and Marmara Sea has also
been discussed by Stanley and Blanpied (1980). According to these authors, the
sea level changes duringi the late Holocene was the most important factor
controlling the currents in this area.
In the Marmara Sea, the surface currents are directed from the Bosphorus
toward the Dardanelles Strait with a maximum speed of 2.5 km/h, and a minimum
speed of 750 m/h (Figure A-2). In the Dardanelles Strait, similar to the
Bosphorus, the Black Sea water flows on the surface from north to south, and the
Mediterranean water flows as an undercurrent toward the north. Because of the
strong mixing on the boundary of these two counter-currents, the salinity of the
surface water increases rapidly here. It is 18% in the north Marmara Sea, it
becomes 25% in the Dardanelles, and 37.52% in the north Aegean Sea. There, the
surface temperature is at a maximum of 24.11°C in August and a minimum of 13.33°C
in March. Toward the southern Aegean Sea, the surface waters coming from the
Black Sea gradually disappear.
Dissolved Oxygen
The amount of the dissolved oxygen, especially in the surface water masses,
plays an important role in the biologic properties of the sea. The boundary of
this dissolved oxygen surface layer is 150-300 meters in the Black Sea. Below
this level is an anaerobic (due to high levels of H2S) water body, as in the
Marmara Sea. This deep layer is not found in the Aegean and Mediterranean Seas.
Wave Conditions
The wave conditions on the surface of the seas surrounding Turkey is under
the control of wind direction and its velocity and the fetch distances. But,
since satisfactory studies on fetch are missing, only the conditions of wave
heights and directions will be explained here.
In the Black Sea, northerly and northwesterly winds are dominant especially
in winter months. Because the fetch distance is great in this direction, waves
are high and they strongly erode the foot of high cliffs on the coastline of the
North Anatolian Mountain chain. The strong southwesterly winds in the Marmara
Sea blow sometimes as gales and they alternate with northern winds. In the
Aegean and Mediterranean Seas, the southwesterly winds influence the coastline
during the winter, whereas the moderate northerly winds prevail during the
summer, especially in the Aegean Sea.
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Figure A-2. Surface currents in the seas surrounding Turkey.
The height of the waves and related wind directions are as follows:
Black Sea
Bosphorus
Marmara Sea
Dardanelles
Aegean Sea
Mediterranean
Sea
Mean
N 3-4
N 1
SW 3-4
SW 1-2
SW 3-4
SW 3-4
Maximum
Up to 13 m in winter
Up to 4-6 m in winter
Up to 8-9 m in winter
The tides and other sea level fluctuations are small along the Turkish
coastline. The daily periods of the tides are as follows:
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A/ed/terra/?ean
Black Sea maximum 10 cm
Bosphorus maximum 2.5 cm
Marmara Sea maximum 2.5 cm
Aegean Sea maximum 30 cm
Mediterranean Sea maximum 30 cm
Izmir Gulf maximum 50 cm
Iskenderun Gulf maximum 50 cm
The pattern of storm surges (compared to mean sea level) are as follows
(Aykulu, 1952):
Marmara Sea
Aegean Sea
Black Sea
maximum 101 cm
maximum 122 cm in Izmir
maximum 65 cm in Eregli
According to historical records in Turkey and surrounding countries,
tsunamis and other rapid sea level changes were frequently observed (Soysal,
1985). The waves may not be very high, but they are destructive. Some of them
may be only storm surges, but the others must be tsunamis. This kind of wave
was especially destructive at the Izmit Gulf and at the estuary of Istanbul-
Halic Harbor in the Marmara Sea, at the Izmir Gulf and Islands in the Aegean Sea,
and at the Fethiye Gulf in the Mediterranean Sea.
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200
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THE INFLUENCE OF SEA LEVEL RISE ON THE NATURAL AND
CULTURAL RESOURCES OF THE UKRAINIAN COAST
YURII D. SHUISKY
Geography Department
Odessa State University
Ukraine, 270000 U.S.S.R.
INTRODUCTION
The Union of Soviet Socialist Republics has a larger mainland coastline than
any other nation. However, concerns about global warming have not focused on sea
level rise as much as on other implications of global warming. This relative
emphasis is reasonable when one realizes that most of the Pacific, Arctic, and
Baltic coasts are sparsely developed and that much of this coastal area is
currently experiencing uplift. Aside from Leningrad, the most important
exception is probably the Ukrainian Black Sea coast. Unlike most other parts of
the U.S.S.R., this is a warm coast with a low barrier appropriate for tourism and
substantial fishing that depends on natural systems that are sensitive to sea
level.
Because no research has been done on the subject, we are unable to present
any quantitative estimates of the impacts of accelerated sea level rise, and the
lack of policy assessments makes it impossible for us to discuss response
strategies. With those limitations, this paper briefly describes the activities
along the Ukrainian Black Sea coast that seem vulnerable to a 50- to 200-cm rise
in sea level, characterizes the coastal environment, and summarizes existing
research on sea level trends and related coastal processes. We hope that this
paper helps to encourage officials in the Ukrainian Republic to begin considering
the implications of global warming and sea level rise.
RESOURCES AT RISK TO A RISE IN SEA LEVEL
The Black Sea coast of the Ukranian Republic is heavily developed and is one
of the most populated coasts in the U.S.S.R. Fortunately, most of the
development is concentrated on the highlands. Nevertheless, some coastal
barriers and low terraces with elevations between 1 and 5 meters are completely
occupied with buildings, including port facilities, sanatoriums, holiday homes,
and camping establishments. The barriers along the Sukhoy and Adjalyk Lagoons,
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for example, have considerable port facilities. All of these economic resources
would be at risk from a 50- to 200-cm rise in sea level.
The Sasyk Lagoon near the mouth of the Danube has been transformed into a
freshwater basin, with river water used for irrigation. To prevent seawater from
encroaching during heavy storms, a 12-kilometer-long, 4-kilometer-high dike was
built; however, sea level rise could threaten the dike unless additional
protection is constructed.
Along the Sasyk (near Eupatoria) and Dniester Lagoon, the coastal barriers
have railroads and highways. For almost 40 years, the retreating shores have
created difficulties for these critical transportation links, especially on the
Dniester barrier. As a result, the Dniester barrier has been protected with a
5,000-foot-long concrete structure and rip-rap. On some parts of the Sasyk
barrier the highway has been rebuilt somewhat inland. On the Tiligul and
Kujalnik barriers, the highway is about 200 meters inland on a dike with an
elevation of about 5 meters.
Because the coastal barriers are only 1 to 5 meters above sea level, future
sea level rise threatens the aquaculture in the lagoons behind them. To prevent
problems in the Usunlar, Burnas, and a few other barriers, the dunes have been
artificially elevated. Because the Shagany, Alibey, Budaki, Tiligul, Usunlar
limans are important for fish breeding, stabilizing barriers in front of the
lagoons is important.
The natural conditions of the Black Sea coast encourage erosion and cliff
retreat; average annual cliff erosion rates range from 0.1 to 4.5 meters per year
(Shuisky and Schwartz, 1988). More than half of all the coastal protection
structures attempt to retain artificial beaches, mainly groins and breakwaters.
Seawalls are less widespread, and there are very few rip-rap structures. An
accelerated rise in sea level would clearly diminish the effectiveness of
existing structures, and probably necessitate increased artificial replenishments
of beaches, as has already occurred in other countries.
The largest portion of the shoreline protected from landslides is along the
Crimea coast, where 50 kilometers (almost 15% of the coast) -- mainly from Sarych
Cape to Alushta -- is protected by short concrete groins with artificial gravel
beaches between them. On the western Crimea coast, 5 kilometers are protected
near Eupatoria, Saky, and Nikolayevka. Around Skadovsk the shore is protected
by a one-kilometer-long seawall and an artificial beach, and there is a seawall
of about 2 kilometers (concrete and rip-rap groins with an artificial sand beach)
near Port Zhelezny. All of these structures will have to be fortified.
In a number of cases, artificial beaches have been used. The District of
Ochakov, Koblevo, and along Odessa Bay each have about 2 kilometers of protected
shore (solid concrete and stabilized slopes). In the City of Odessa, the shore
is strengthened for 12 kilometers from Langeron Cape to Bolshoy Fountain Cape.
Coastal protection structures were built near Illichevsk and on the Dniester
barrier. All of these artificial beaches would require additional fortification
as sea level rise accelerates.
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Shuisky
Neither the U.S.S.R. nor the Ukraine has a single organization to deal with
research on and exploitation of the natural and cultural resources of the Black
Sea coastal zone as a whole. Instead, several regional organizations are
responsible for part of the problem, for example, the Ukrainian Institute of
Communal Building (Odessa) in the Ukraine, the Sea Coast Protecting Concern
(Krasnodar) and the Sea Hydrotechnical Construction Institute (Sochi) in Russia,
and the Sea Coast Protecting Concern (Tbilisi) in Georgia. Some aid is rendered
by other organizations, such as the Sea Institute in Odessa, the Geological
Station in Yalta, and the Hydrological Station in Vilkovo. Scientific research
is carried out by laboratories and scientific groups in the Universities of
Odessa, Rostov, Kuban, Moscow, and Kiev.
No administrative or economic organization on the Black Sea coast is
concerned with solving the sea level rise problem. The lack of concern is caused
by a number of factors, including the following: (1) the lack of reliable data
about the disastrous effects of the rise on the natural and cultural resources
of the Ukranian coast; (2) the relatively low rate of the rise of the Black Sea;
(3) the economic system of the Ukraine, which does not encourage research on
possible future disastrous consequences of the sea level rise; and (4) the low
prestige of the scientists, whose opinion is usually ignored by state and
economic institutions.
THE COASTAL ENVIRONMENT
Climate
The average air temperature at the coast varies from 9°C in the Odessa
region to 16°C in the Yalta region. The mean temperature during the warm season,
which lasts from April to October, is 22-24°C. Maximum temperatures occur in
August when some days reach 30-35°C, the absolute maximum being 40°C.
The winter is fairly mild; in January, the average air temperature is
-2.5°C in Odessa and about 6.5°C in the Yalta region. The temperature often
falls below -10°C, but rarely below -20°C. The absolute minimum is -28°C. A
severe winter happens once in 14-15 years, and a warm winter occurs once in 12-13
years.
Rain and fog prevail during the cold half of the year, and snow falls every
year. The precipitation reaches 300-400 mm per year in the Odessa region,
200-300 mm in the Tarkhankut and Kerch peninsulas, and 500-600 mm in the southern
coast of the Crimea.
The Black Sea water is warm; in the open sea its temperature is never lower
than 6°C, reaching 19°C to 26°C in July and August and up to 28°C in shallow
bays. In the winter, the temperature falls to 2-3°C at the shore; in narrow
areas along the shores between the Danube delta and the Crimea, sea ice can
appear, on the average, every 3-5 years. The sea freezes annually only at the
Danube and Dnieper outfalls, and in small bays (Egorlyk, Tendra, Djarylgach,
Perekop, and in the Kerch Strait).
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Geology
It is known (Shuisky, 1982) that the northern Black Sea coasts are
characterized as classical liman coasts. Sediments in the limans and lagoons
contain chemical elements and organic salts that can be used for medical
treatment. Deposits of medicinal mud were found in the limans of Burnas, Budaki,
Hadjibey, Mojnacki, Saky, and especially the Kujalnik liman. Those medicinal
sediments have led to the establishment of numerous medical and sanatorium
institutions.
The districts of the Danube delta, Shagany, Burnas, Kujalnik, Saky limans,
Yalta, Theodosia, Kerch, and Skadovsk towns are the sites of mineral water baths.
Their contents are varied including carbonates, hydrocarbonates, potassium and
sodium, sodium and magnesium, and chalybeate waters. These deposits, too, serve
as the basis for many medical institutions.
The Black Sea coast within the Ukraine borders also contains deposits of
certain nonmetallic minerals, such as building stone, sand, gravel, pebbles, and
sedimentary ores. The largest deposits are located near the Danube delta, near
Odessa city, Sevastopol and Theodosia towns (building stone and raw cement
materials), on the shores of the Jebrijan cove and Dnieper, and the Sasyk limans
(sand and shells).
Among the natural resources of the Black Sea coast, the recreational
resources are the most important. Warm water and a long warm season are the main
factors that make the Black Sea a popular tourism and recreational area. In
addition, coastal sediments contain important deposits used for medical purposes.
Sand and pebble sediment exploitation (removal) is forbidden within the
coastal zone. The nearshore zone is the traditional location for the fishery
industry. It is most intensive in the Danube, Dniester, Dnieper outfalls,
Karkinit and Kalamit Bays, and Kerok Strait. The biggest seaports are
Illichevsk, Sevastopol, and Kerch. Fish-breeding farms are situated on the
shores of the Sasyk, Shagany, Budaki, and Tiligul limans.
There are many nature reserves on the Ukranian Black Sea coast. Their
purpose is to save the gene banks and protect flora and fauna. The largest of
them, the Danube reservation, is situated in the Danube outfall. It is oriented
to ornithology and botany, as well as research on freshwater fish. In addition,
there are important bird reservations in Chernomorsky (in Egorlyk and Tendra
Bays) and Lebiashiy (on Lebiazhiy isles), and the Kalanchak Isles in Djarylgach
Bay were declared reserve areas. The Martian Cape reserve on the southern coast
of the Crimea Seas has a botanic orientation. The Kara-Dag reserve protects
volcanic landscapes and relief shapes, and also the precious and semiprecious
mineral and rock deposits.
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Shu/sky
SEA LEVEL MEASUREMENTS
There is a general awareness that the Black Sea has been rising for at least
the past 200 years. This phenomenon was discovered by instrumented
measurements at many locations in the U.S.S.R. and in other countries (Bulgaria,
Romania, Turkey) on the Black Sea.
Although the measurements of the sea level changes began in Odessa in 1803,
the first gauging rods turned out to be unreliable, and the data from 1870 are
now the earliest used. In that year, controlled gauging stations were
established in Odessa, Ochakov, Sevastopol, and Poti, which are now sources of
precise data about the changing level. During 1916-23, measurements were begun
in other places, generally in seaports. The data from those observations have
been analyzed by many researchers (Blagovolin and Pobedonostzv, 1973;
Pobedonostzv, 1972).
The direct observations with gauging staffs indicate a relative rise of sea
level. On the Black Sea coast it consists of the two constituent phenomena: (1)
the eustatic rise and (2) tectonic sinking of the littoral areas. The
correlation of the eustatic and tectonic factors can differ, however, among
various parts of the Black Sea. The level can rise, but also the littoral areas
can rise, sink, or be stable, and the rates of these phenomena can be equal or
unequal. It has been determined that there are 16 combinations of eustatic (E)
and tectonic (T) factors (Shuisky, 1978).
1. +T>-E - very strong, relative sinking, never rises
2. +T<-E - strong, relative sinking, never rises
3. +T4>+E - weak, relative sinking, usually does not rise
4. +T<+E - weak, relative sinking
5. -T>-E - very weak, relative sinking
6. -T<-E - weak, relative sinking
7. -T>+E - moderate, relative sinking
8. -T<+E - strong, never turns into sinking
9. +T=+E - the level state is relatively stable
10. -T=-E - the level state is relatively stable
11. +T=-E - strong, relative sinking
12. -T=+E - strong, relative rising
13. Stable T with +E - rising
14. Stable T with -E - sinking
15. Stable E with +T - relative sinking
16. Stable E with -T - relative rising
This pattern of the T and E correlation should serve as a basis for the
coastal zone dynamics analysis. (For the most part, the coastal zone is
indifferent to the causes of both stability and changing with various rates. It
is the stability, rising, or sinking at various rates that is important. The
actual rates of positive and negative long-term changes in different physical and
geographic conditions of a sea coast are of particular significance.)
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There is a lack of practical information in connection with sea level rise.
Although scientific research on the process is under way, there is still no
interest on the part of industrial, economic, and financial organizations despite
the important natural and cultural resources on lowlands (Stepanov and Andreev,
1981). The most serious reports of the researchers on the natural processes
connected with the sea level changes were published in collections such as "Sea
Level Fluctuations" (Kaplin et al., 1982a) and "The Sea and Oceanic Level
Fluctuations" (Kaplin et al., 1982b).
The analysis of the modern data on Black Sea level change within the Ukraine
led to the conclusion that there is a relative rise at 26 stations and sinking
at only one (Kherson, situated in the Dnieper outfall). The relative rising
rates vary considerably from place to place -- from +5.10 to -1.50 mm/year (Table
1), with an average of 1.40 mm/year. The higher rates prevail between the Danube
Delta and Dophinovka Lagoon and in the Dnieper outfall. The information on
modern relative changes referred to here were verified by other geomorphological
and geological research methods (Melnik and Mitin, 1982; Ivanov and Shmuratko,
1982).
SEA LEVEL RISE AND COASTAL PROCESSES
The influence of multicentennial sea level change on coastal development in
different seas has been studied quite extensively. Much research was carried out
to define the curve of sea level rise in the Holocene period using stratigraphic,
radiocarbon, oxygen, palynologic, and archeologic methods. These studies led to
the construction of Black Sea coast maps and the distribution maps of the
abrasive and accumulative relief shapes for the last 50,000 years. In Odessa
University, the climate-stratigraphic method is being worked out, based on the
astronomic climate theory of M. Milankovich. Transferring a radiation curve into
a climate (or eustatic) curve, we use the sea level as an integral index.
As far as the annual and centennial changes (algebraic sum of E and T) and
their influence on coasts, the study of this question in the U.S.S.R. is
inadequate at present.
The methods for calculating the nearshore bottom abrasion rates have almost
been completed. These methods also take into account the T and E correlations.
Finally, we will be able to quantitatively estimate the impact on the shore
processes of the sea level change rates and figures.
But it is already obvious that a more rigorous analysis of such a phenomenon
-- its nature and its impacts on coastal systems -- is extremely urgent. Such
an analysis should address sea wave activity and the eustatic factor interaction.
It is also necessary to carefully check the benchmark tidal gauges, and their
steadiness, where especially high relative rising rates are noticed. We know
(Klige, 1981) that about 14.3% of the general world ocean shoreline has been
rising at more than 2 mm/year.
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Table 1. Average Relative Fluctuations of the Black Sea Level Along the Shores
of the Ukraine (mm/year)
Rates of sea level
Coastal points
1. Sulina (Romania)
2. Primorskoje
3. Lebedevka
4. Bugaz
5. Illichevsk
6. Odessa
7. Yuzhnij
8. Ochakov
9. Nikolayev
10. Stanislav
11. Kasperovka
12. Kherson
13. Gerojskoye
14. Tendra Spit
15. Lazurnoye
16. Skadovsk
17. Khorly
18. Chernomorskoye
19. Tarkhankut
20. Yevpatoriya
21. Sevastopol
22. Balaklava
23. Yalta
24. Alushta
25. Sudak
26. Feodosiya
27. Kerch
a + = Sea level is rising.
b - = Sea level is sinking.
Duration
years
1896-1988
1951-1975
1950-1987
1945-1987
1958-1987
1875-1988
1974-1988
1874-1985
1916-1983
1925-1970
1916-1970
1916-1987
1951-1986
1885-1987
1964-1988
1923-1985
1923-1985
1927-1986
1878-1986
1917-1986
1875-1986
1951-1985
1928-1988
1928-1987
1931-1987
1923-1987
1882-1970
fluctuations
(mm/year)
Average Precision
+1.60a
+1.80
+1.59
+2.01
+1.51
+5.10
+1.26
+0.97
+0.52
+0.85
+2.10
-1.50b
+3.70
+2.26
+1.10
+0.82
+0.95
+1.04
+1.21
+0.72
+0.91
+0.60
+1.10
+1.30
+0.68
+0.35
+0.45
±0.13
±0.78
±0.51
±0.66
±0.48
±0.32
±0.43
±0.27
±0.19
±0.25
±0.14
±0.54
±0.79
±0.35
±0.18
±0.16
±0.11
±0.41
±0.23
±0.14
±0.15
±0.63
±0.22
±0.33
±0.28
±0.18
±0.15
By drawing analogies from storage lakes and from the Caspian Sea in the
U.S.S.R., we can propose the following steps to respond to intensive sea level
rise expected as a result of the greenhouse effect:
• A survey of both the most and the least valuable natural and cultural
resources states, and of their locations along the Ukranian coast, is
needed. An assessment of the morphology and coastal dynamics is also
important. The results should be used to identify the places requiring
protection from the seawater invasion -- in the first phase, second
phase, third phase, etc. The financial and material resources to
accomplish the necessary measures must also be identified.
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• Some of the cultural resources can be relocated to secure areas. Others
can be dismantled because their work is complete. The remainder may
need protection from the advancing sea when the level rises. Various
combinations of these approaches are possible.
• The protection of the most valuable natural and cultural resources on
the lowlands can be realized by using protective seawalls or dikes,
following the example of the Netherlands, Belgium, Great Britain, and
China. The lowland in the State of New Jersey (U.S.) is also protected
and we have taken such experience into account here in the Ukraine --
not, however, as protection from the eustatic level rise, but as
protection from heavy storms.
• Elevation of artificial sandy dunes can be used where the appropriate
conditions exist, especially in the areas of active wave and eolian
accumulation of sandy sediments. Dune formation should precede the sea
level rise.
• The long-term effect on the coastal zone of artificial placement of
sediments usually promotes the increase of beaches and accumulative
forms. In the Holocene period of the Black Sea shelf, during the
periods of coastal zone sediment activation, the areas of accumulative
forms increased, and in the periods of sediment deficit, these areas
decreased, down to an entire washout. In the modern stage of the Black
Sea coast development, most of the barriers and spits developed
following a sea level rise, especially where the sediment reserves are
sufficient. Accordingly, we cannot rule out the possibility that the
coastal zone is artificially saturated with sediments that will also
promote the rise of the accumulation forms after the accelerated sea
level rise in the following decades.
• Since the Black Sea coastal zone structure is very complicated, there is
no single step that will resolve the sea level rise problem. A
combination of measures is necessary.
It is unclear whether the disastrous sea level rise is something certain and
unavoidable. But in the last year, the idea of such a rise caused a tide of new
research, which widely discussed various causes of the world ocean level's
changing nature, including the influence of the anthropogenic factor.
Hoffert and Flannery (1985) came to the conclusion that the nonstationary
impact of C02 on the climate (in the time scale of 10-100 years) is conditioned
by simultaneous influence of several external factors (outer-atmosphere
insolation, volcanic aerosols, concentration of C02 and the other greenhouse
gases, and also by internal changeability of the climatic system (first of all,
the internal oceanic dynamics).
In the U.S.S.R., many scientists have also come to such conclusions. For
instance, on the basis of the analysis of the latest comprehensive observations,
results, and climate numerical modeling, Kondratiev (1986, 1987) concluded that
existing information is insufficient for elucidation of global climate trends and
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the complicated changeability and causal conditionality of climate. The tendency
to ascribe observed climate temperature to C02 influence encounters has been
rejected by some for a number of reasons, including the character of the
atmosphere and ocean interaction.
Long-term observations of the abrasion and accumulative shore dynamics cause
me to make other correlations with the latest Black Sea level relative changes.
The connections are not significant. The causes are still unknown, the nature
of such interaction is not clear, and the complex analysis of the results has not
yet been carried out. But still, the results received are sufficient to offer
a series of theoretical theses, which can explain the causes of the modern
seashore retreat.
Although the Ukraine has no policy to address sea level rise, long-term
research on the winds, waves, currents, and changing level is continuing. In
this case, it is important to carry out the synchronic observations of the
cliffs, beaches, barriers, spits, and changing longshore drifts. We have already
received such data, but laboratory work and theoretical analysis, which will be
completed in 1990, are also required to demonstrate the connections between the
sea level changes and the changing storm strength, and the changing sea level and
cliff abrasion rates. We will look at the shoreline accumulative forms, retreat
rates, drift distribution, and the interrelationships between the destructive and
accumulating processes.
CONCLUSION
Before we can sensibly specify or implement policies to protect the Ukranian
coast from rising sea level, we must understand the implications. To do so,
scientists will need the enthusiastic encouragement of policy officials, who have
much of the information necessary for meaningful assessments.
Scientists will also have to cooperate better with policy officials and with
each other. The issue is clearly interdisciplinary, which means that the issues
that professionals in one field prefer to study may not address the questions
that people from other fields are -- or at least should be -- asking. In the
case of sea level rise, policy makers need coastal scientists to determine which
land would be inundated or eroded, or which would experience increased flooding
or salinization, and to assess the ecological implications; they need engineers
to estimate the cost of protecting all the coastal areas, as well as
recommendations for incorporating sea level rise into current infrastructure
planning; and they need economists to estimate the costs of protection versus
allowing the sea to advance. In turn, the researchers need policy makers to
provide continual guidance on the type of information most useful for decision
making.
BIBLIOGRAPHY
Blagovolin, N.S., and S.V. Pobedonostsev. 1973. Recent vertical movements of
the shores of the Black and Azov seas. Geomorphology 3:46-55 (in Russian).
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Wed/terra/7ea/7
Hoffert,. M.I., and B.P. Flannery. 1985. Model projections of the time-
dependent response in increasing carbon dioxide. In: Potential Climatic Effects
of Increasing Carbon Dioxide. MacCracken, M.C., and P.M. Luther, eds.
Washington, DC: U.S. Department of Energy, p. 149-190.
Ivanov, G.I., and V.I. Shmuratko. 1982. Oceanic levels during the Pleistocene.
In: Sea Level Fluctuations. Moscow: Moscow State University Publishing House,
p. 60-75 (in Russian).
Kaplin, P., R. Klige, and A. Chepalyga, eds. 1982a. Sea Level Fluctuations.
Moscow: Moscow State University Publishing House, 310 p. (in Russian).
Kaplin, P., R. Klige, and A. Chepalyga, eds. 1982b. Sea and Oceanic Level
Fluctuations for 15,000 Years. Moscow: Nauka Publishing House, 230 p. (in
Russian).
Klige, R.K. 1980. The Ocean Level During Geological Time. Moscow: Nauka
Publishing House, 145 p. (in Russian).
Klige, R.K. 1981. Estimations of Contemporary Seashores Vertical Changing in
Connection with Ocean's Level/Coastal Zone of the Sea. Moscow: Nauka Publishing
House, p. 11-17 (in Russian).
Kondratiev, K.Y. 1986. Natural and anthropogenous changing of climate. Heral
of Acad. Sci. U.S.S.R. 10:30-39 (in Russian).
Kondratiev, K.Y. 1987. Carbonic acid gas and climate: Data of observation and
numerical modelling. New All-Union Geogr.Soc. 119(2):97-105 (in Russian).
Melnik, V.I., and L.I. Mitin, eds. 1982. Geology of the Ukrainian Shelf:
Environment, History, and Methods of Investigations. Kiev, Naukova Dumka
Publishing House, 175 p. (in Russian).
Pobedonostsev, S.V. 1972. Contemporary vertical changing of the seashores
around the European part of the U.S.S.R. Oceanology 12(4):460-469 (in Russian).
Shuisky, Y.D. 1978. Types of Coasts of the Earth Globe. Odessa: Odessa State
University Publishing House, 75 p. (in Russian).
Shuisky, Y.D. 1982. Limans and liman's coasts. In: Encyclopedia of Beaches
and Coastal Environment. Schwartz, M.L., ed. Stroudsburg: Hutchinson Ross Co.,
p. 516-518.
Shuisky, Y.D., and M.L. Schwartz. 1988. Human impact and rates of shore retreat
along the Black Sea coasts. Journal of Coastal Research 4(1):405-416.
Stepanov, V.N., and V.N. Andreev. 1981. The Black Sea -- Resources and
Problems. Leningrad: Hydrol.-Meteorol. Publishing House, 157 p. (in Russian).
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COASTAL MORPHOLOGY AND SEA LEVEL RISE
CONSEQUENCES IN TUNISIA
DR. AMEUR OUESLATI
University of Tunisia
Tunis, Tunisia
INTRODUCTION
The consequences of sea level rise are already evident on the 1300-km
Tunisian coast (Oueslati et al., 1987). Almost the entire landscape of beaches,
rocky low coasts, salt marshes -- and particularly cliffs -- is retreating
(Oueslati, 1989). In many cities, erosion is threatening hotels, dwellings, salt
pans, industrial establishments, and the public infrastructure; the nation's
archeological heritage is also at risk. The few sections of the coast not yet
suffering erosion are generally in undeveloped areas at the mouths of rivers and
the bottom of some bays.
The vulnerability of the Tunisian coast has been particularly evident in the
aftermath of storms. For example, a January 1981 storm in the Gulf of Tunis
caused severe damage and completely removed beaches along many stretches of
coast, especially the suburbs of the capital. With a stable sea level, the waves
could have rebuilt these beaches after the storm. But the Bruun Rule shows that
when sea level rises, offshore portions of the beach system must gradually rise
as well, implying that much of the sediment deposited offshore during storms will
remain there. The experience in Tunisia after the 1981 storm has been consistent
with this theory.
Water tables are also rising, with a resulting salinization of low-lying
areas, particularly in subsiding areas such as those along the Gulfs of Tunis and
Gabes (Oueslati, 1989). Rising seas have also transformed many occupied (in
ancient times) areas into wetlands, and may soon do the same to the cultivated
areas of antiquity (Oueslati, 1989; Paskoff and Oueslati, in press).
In response to these problems, coastal defense structures are becoming
increasingly common on the Tunisian coast. Seawalls are most common, with
dimensions scaled to the size and value of the buildings being protected. Along
the Gulf of Tunis and at Mahdia, the structures are very large. On the other
hand, many human activities are increasing the vulnerability of the coast:
extraction of beach sand for construction and the loss of marine vegetation as
a result of pollution directly weaken the coast. Dams for managing water
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resources and jetties at harbor entrances diminish the natural supply of
sediment, which might otherwise offset some of the erosion (particularly in cases
where the littoral drift is mostly in one direction, such as Bizerte and Ghar el
Mebah, where beaches downdrift of the jetties are eroding rapidly).
The next two sections briefly summarize the likely impacts of an accelerated
rise in sea level on the Tunisian coast and the possible responses. Although
Tunisians have not studied in detail the implications of sea level rise for each
particular coast, the reader can better understand our vulnerability by
considering the environmental conditions of the coast in more detail; this
information is provided by the final sections of this paper.
IMPACTS OF ACCELERATED SEA LEVEL RISE
About half of Tunisia's population and most of its major cities are on the
coast (Figure 1). The many ports range from industrial-sized harbors to those
servicing small fishing or pleasure villages. Most of the nation's industrial
and tourist establishments, and all of its salt production facilities, are very
close to the shore. The remainder of the coastal lowlands are cultivated --
mostly for cereals, although fruits and vegetables are also profitable in the
Medjerda River Delta and around urban areas where they can be sold to local
residents. All of these activities are at risk.
A rise in sea level of 50 to 200 centimeters would almost undoubtedly result
in a great retreat of the entire coast, the extension of salinized areas, and the
disappearance of some natural systems. Along the Gulf of Tunis, important parts
of the Medjeida delta (Figure 1) and the Milian plain would be inundated; most
lagoons either would disappear or would be shifted substantially landward; and
Tunis and its suburbs would be seriously threatened. Along the Gulf of Gabes,
coastal systems could probably shift landward. New wetland ecosystems may form
on the alluvial plains where the current ecosystems are inundated. Figure 2
illustrates the Kerkna archipelago, where the outer parts of Sfax and Gabes may
be seriously damaged -- perhaps even more than Tunis, given current subsidence
trends. Sea level rise at sfax is estimated to be 5.7 mm/yr, a rate almost four
times higher than the worldwide average (Pirazzoli, 1986).
In the central part of Hammamet Gulf, the most important impact would be
saltwater intrusion into cultivated alluvial plains. Meanwhile, the wetlands
behind the foredunes may be converted into open-water lagoons. Cities in the
northern and southern parts of this gulf may be severely damaged, especially the
large tourist complexes of Hammamet and Sousse Monastir. Along the eastern coast
of the Cap Bon peninsula and at Dimass, the lagoons seem likely to be completely
lost, because rocky high ground (a consolidated Tyrrhenian bar) immediately
inland would preclude a landward migration. Similarly, in the Sahel, the narrow
alluvial plain would be squeezed between an advancing shore and the rocky high
ground.
Rising sea level also threatens fishing, a major occupation and an important
Tunisian tradition. The two largest fisheries are located at the inlets of the
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Oueslati
0
Figure 1. Cultural and economic features (urban population, hotels, and ports)
[Legend: a = towns wholly or partly installed on unconsolidated lowlands -
1,000s of inhabitants; b = zone occupied by important tourist area; c = hotel
capacity - 1,000s of beds; d = ports; e = fishing ports; f = marina]
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Figure 2. Kerkna archipelago -- possible consequences of 50, 100, and 200 cm
rise in sea level (hatched areas would be invaded by sea water).
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Dues 1 ati
Ichkeul and Bhiret el Biban Lagoons, which would be drastically altered by sea
level rise. Along the Gulf of Gabes (particularly Jerba and Kerkna Islands)
fishing is still conducted by the traditional method of using palm fronds stuck
into tidal flats to trap fish brought in by tidal currents; along other parts of
the gulf, many families feed or support themselves by gathering cockles in the
tidal flats. But sea level rise would inundate most of the tidal flats.
Breeding facilities for fish (Monastir), oysters (Lagoon of Bizerte) and other
shellfish would also be at risk.
Finally, we could expect the erosion and loss of a major portion of the many
archeological sites that are among the most important constituents of Tunisian
culture.
RESPONSES
Like other nations discussed in this report, Tunisia could respond to sea
level rise either by holding back the sea or by retreating landward. Most of the
structural approaches described by Pope (Adaptive Options, Volume 1) would be
appropriate for some part of the coast, and in many cases, the necessary
structures would not have to be erected for several decades. By contrast,
although shores will retreat and settlements will be relocated in many (if not
most) parts of the coast, the anticipatory strategies presented by Titus
(Adaptive Options, Volume 1) would be difficult to implement, because they
presuppose that (1) officials are willing to modify current activities to protect
against crises not likely to occur for several decades, and (2) that
environmental protection is sometimes important enough to prohibit construction.
Neither of these assumptions yet applies to coastal management in Tunisia.
The inhabitants of the coast are somewhat aware that erosion and
salinization threaten their fields and dwellings, but they generally are not
aware that rising sea level is causing the problem. Similarly, it would be
obvious to mudflat fishermen that if sea level rise inundated the flats, their
livelihood would be threatened. Because their ancestors have pursued this
traditional occupation for centuries, the fact that the crisis would confront
their grandchildren (instead of them) would not substantially reduce their
concern. But no one has informed them about this problem.
Currently, only two state agencies are even concerned about current beach
erosion problems. Although they have tried solutions, the projects have been
arbitrary, scattered, and poorly studied. They have been mostly ineffective and
in some cases have made the problems worse. Managers almost never consider the
relationship between sea level rise and current problems. There is a complete
lack of legislation and policies to protect the coastal environment. When
coastal areas are developed, no one is considering the argument by Everett
(Environmental Implications, Volume 1) that in the long run, a hectare of
mudflats might feed more people than a hectare of agricultural land, and that we
should therefore set development back farther from the shore.
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THE COASTAL GEOMORPHOLOGY
Cliffs
The most important and extensive active cliffs are characteristic of the
northern coasts (characterized by relatively deep water and exposed to strong
northern and northwestern swell) of the country where they generally average
15-30 m in height. In rare contrast, such as at the extremity of the Cap Bon
peninsula, they are higher than 50 m.
For the most part, these cliffs consist of sandstone and clay and rarely are
composed of rocks, limestone, or marls. Rocky cliffs (eolianites and marine
quaternary limestones) that alternate with fluvial layers often show remarkable
differential erosion rates. However, such cliffs are usually only a few meters
high (5-10 m).
Along the entire northern coast, the cliffs are retreating, sometimes quite
rapidly, under the attack of north and northwesterly swells. Measurements taken
during 1982-87 on cliffs 7 to 15 m high, formed in the Numidian flysch, showed
them retreating at rates varying from 1.5 to 8 m/yr. Because of the very humid
atmosphere and steep coastal slopes, landslides are frequent wherever clays
dominate. Landslides along the northern coasts are also threatening human
dwellings. Fortunately, this area is not yet densely occupied.
There are fewer eroding cliffs on the eastern coasts. For the most part,
they are a few meters (2-5 m) high and are formed in Pleistocene materials
(especially alluvium, eolianite, and marine limestone). The only important
cliffs there are along the Gulf of Gabes and its surroundings, where they are
formed in gypsum-rich clays covered by a strong calcrete (attributed to the lower
Quaternary) or a gypsum crest (late Pleistocene). These latter cliffs, generally
averaging 7 to 15 m in height, are sometimes prone to high rates of erosion,
despite the small waves. There is severe erosion of the important archeological
sites that are visible in the upper part of the cliffs (e.g., on western coast
of the Kerkna archipelago and at Nadhour between Sfax and Gabes Town).
Unconsolidated Low Coasts
Unconsolidated low coasts are extensive in Tunisia and are found primarily
at the inland margin of wide gulfs (Tunis, Hammamet, Gabes) and bays (Tabarka and
Bizerte). They are especially developed and predominant along the eastern
portion of the coastal landscape. They generally consist of alluvial plains
formed by fine material dating back to the late Quaternary, mainly the Holocene
and the historic times. The seaward margin of these lowlands is characterized
by sandy beaches, small cliffs, or salt marshes. These are found in the Gulf
of Gabes and its surroundings where tides are high and may reach 2 m at spring
tides.
Careful observations reveal significant regional differences in these
lowlands because of physical conditions, human activities, and the orientation
of the coast. This section describes several distinctions:
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• A narrow alluvial plain situated at the inland portion of a bay bordered
bv sizable cliffs and intersected bv small but active wadis. The
shoreline is characterized bv a large sandy beach favoring the formation
of extensive dunefields and important human settlements inland.
This is the case of the Tabarka and Zwaraa coasts, which are situated near
the Algerian border. The plain, averaging 4 m in height, is made of sand and
clay sometimes containing more or less well-rounded pebbles. It covers about
5 km2 and is partly occupied by the Tabarka agglomeration.
This area boasts one of the best sandy beaches of the country. Extending
over 10 km, this beach stretches to 50-70 m in width, especially around the mouth
of wadis. It benefits from two important sources of sediments: (1) wadis that
cross in their higher courses steep slopes formed in the Numidian flysch, and (2)
rocky active cliffs situated at the borders of Tabanka Bay. Well exposed to the
ambient winds, this beach formed an important source of sand to be blown inland
to create an extensive and thick dunefield (Ouchtata field) that is today largely
stabilized by a planted forest. The system must have been repeated in the
geologic past, because recent dunes cover Pleistocene eolianite. The assemblage
of forms is crossed by active wadis that in turn supply the shoreline with sand.
• A narrow, largely alleviated plain, occupying the inner margin of a bay
and devoid of active wadis. The shoreline is also characterized by a
sandy beach favoring the formation of large dunes.
In Bizerte, situated on the northern coast, the plain is 200-700 m wide and
covers about 3.5 km2. Its altitude, which rarely exceeds 10 m above sea level,
is sometimes lower than 2 m. This is especially the case in the outer section,
which is often characterized by a swampy landscape. Sediments are mainly
composed of sand and silt, except in the northern part where clay predominates.
The sediments are locally quite thin (50 cm-1.5 m) and cover marine consolidated
deposits inherited from the Tyrrhenian stage. The beach covers about 12 km. At
its eastern part, well exposed to the northwest winds, is a large field of sand
dunes (Rmel's field), now almost wholly colonized by a planted forest.
• A wide deltaic plan formed bv a large wadi and situated in a gulf. The
shoreline of this plain is characterized bv sandy beaches and lagoons.
The deltaic plain of the Medjerda, the largest and most important river of
the country, covers about 600 km2. It is generally 1-10 m above sea level, but
in some parts it may be less than 30 cm above sea level. Its sediments are
mainly composed of sand and clay. Swamps occupied a very large portion of the
area before the draining operations undertaken since the French colonization.
Today the swamps are found only in the lowest section of the delta, especially
near the shore.
The formation of this deltaic plain dates back mainly to the Holocene. But
its progradation was significant during historic times because of the increased
sediment carried by the river following deforestation. The ancient archeological
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site of Utica illustrates such a history of alluviation. This site is today more
than 10 km inland, whereas it was a harbor in ancient times.
The coast is characterized by a relatively wide (10-15 m) sandy beach and
a low (2-3 m) and narrow (30-60 m) foredune. The northern part shows a typical
spit at the location of a former mouth of the Medjerda River, which was abandoned
following the 1973 flood when the river shifted southward to occupy an artificial
channel originally designed to drain the excess water during floods. The
southern part of the coast is well exposed to the northwestern winds, which
favored the formation of a dunefield (Raoued Gammarth) now almost entirely
wooded. The coast is also characterized by a lagoonal landscape (see the
paragraph describing lagoons).
• An alluvial plain at the mouth of a ma.ior river and situated at the
inland margin of a deep bay. The coast is characterized by a densely
occupied sandy beach.
This is the case of the coast of the bay of Tunis, which is largely occupied
by the southern suburbs of Tunis, the capital of the country. The alluvial plain
is an accumulation mainly of the Miliane wadi, Tunisia's second largest river.
Relatively wide (approximately 36 km) and low (2-10 m), this coastal plain was
created essentially during historic times because its material covers marine
deposits dated from about 2,750 years ago and certain antique ceramics. The
alluvial deposits are generally fine (sand and clay), but can locally contain
some coarse layers of mixed and more or less well-rounded pebbles.
The beach is about 10 m wide and is generally accompanied by a small
foredune (1-2 m high and 10-30 m wide). Dunes are much more prevalent on Tunis's
eastern coast than on its northern coast. An example is the small dunefield of
Borj Cedria-Soliman, which is partly covered by a planted forest. The land
immediately behind the foredune, is almost everywhere, swampy and colonized by
salt plants.
• A straight coast with active streams, narrow alluvial plain, broad sandy
beaches, extensive dunefields, and absence of ma.ior human settlements.
These characteristics are prevalent along the coast between Wadi el Abdi and
Wadi el Mgaiez on the northwestern face of the Cap Bon peninsula. The plain,
averaging 800 m wide and 5-10 m high, is limited landward by a dead cliff. Its
deposits are generally made of sand and silt and often lie on a bedrock platform
inherited from the Tyrrhenian transgression. This coastal type is prominent only
around the mouth of wadis that in their higher and middle courses drain steep
slopes across Miocene marls and sandstones. The beach is generally 10-15 m wide,
but can stretch 50 m wide in some river mouths. The dune fields are sometimes
very extensive and often cover late Quaternary eolianites.
• An alluvial plain at an inland margin of a large gulf intersected by
active wadis. The shore is characterized by a broad sandy beach, with
localized development, and a laqoonal landscape.
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This is the case of a large part of Hammamet Gulf, especially northern
Hergla and southern Sousse. The plain covers about 150 km2; its height varies
from 2 to 10 m. The seaward parts of the coast are often swampy and saline.
The beach is generally well developed, stretching into 40 m wide in many places.
But foredunes are large in only two cases: in Skanes and between Hergla and
Selloum, where it is largely wooded. Lagoons characterize segments of the
northern Hergla and southern Sousse coasts. Except for the area between Hergla
and Bou Ficha, the Hammamet Gulf coast has been subjected to extensive human
development, particularly hotel construction in Hammamet, Monastir, and
especially Sousse.
• A relatively straight coast devoid of active wadis and characterized by
a narrow coastal plain and wide sandy beach. The human installations
vary from one region to another.
In four main regions -- Mahdia, Chebba, northeast Jerba, and Zarzis -- the
coastal plain is sometimes only a few hundred meters wide. Its altitude may be,
such as at Mahdia, less than 3 m above sea level, where there is extensive
swampland. Generally this plain is situated downdrift from a consolidated
coastal barrier or a dead cliff dating back to the Tyrrhenian stage.
At Mahdia the beach is about 10-15 m wide, and the foredune is always small
(2-3 m high) and discontinuous. The coast is partly developed, especially in the
segment next to the city of Mahdia (residences, industries, and hotels). At
Chebba the beach is wider and is sometimes punctuated by Pliocene sandstone
outcrops. It is also has an extensive dunefield inland, now artificially fixed,
and the coast is still unoccupied.
The beach of Jerba, extending almost 20 km, is frequently wide (7-20 m) and
is also punctuated by rocky outcrops (marine limestones, eolianites, and
calcretes). It is not continuous, forming elongated spits at three sites. The
foredune is locally well developed. Sand dunes, sometimes covering large areas
are often occupied by orchards and dwellings. The major part of this coast is
occupied by hotels often built close to the shoreline.
At Zarzis, the coast is largely developed, especially with tourist
facilities. The beach resembles that of Jerba in its width and its outcrops of
rocky material. But the foredune is relatively smaller.
• A coast marked by a sebkha landscape fringed by a microcliff or a sandy
beach, especially at the mouth of active wadis.
These characteristics predominate along a large part of the coast of the
Gulf of Gabes. The lowlands, composed mainly of fine sandy and silty materials,
are generally 5-10 m high. The most important of them are linked to relatively
large wadis and are 2-10 km wide. In some cases, such as at Kerkna and Jerba,
the sandy and silty material is thin (50 cm-1 m) and covers a marine limestone
dating back to the Tyrrhenian.
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Sebkhas1, salt marshes found in northern Africa, are a major feature of the
coastline. The largest sebkhas are inherited from Holocene eustatic sea level
oscillations and occupy the position of ancient lagoons or bays that have been
filled by continental deposits.
Beaches occupying the mouth of wadis are relatively wide (10-20 m) and are
accompanied by small (2-5 m) but sometimes well-defined foredunes. In some cases
the beach forms a spit. Except for the coasts at Gabes and Chaffar, these
beaches are still unoccupied.
Wetlands
Wetlands occupy the seaward parts of the alluvial plains (Medjeida, Miliane,
Gulf of Hammamet, Mahdia) and can be associated with sebkhas. The most important
wetlands exist along the southern coast (Gulf of Gabes and its surroundings) and
correspond to typical tidal marshes favored by the low energy of the coast and
the high tides. Such tidal marshes occupy different positions (behind spits and
capes, bottoms of creeks, mouths of wadis) and have a low vegetation dominated
by Salicornia. They also present some particularities in comparison to tidal
marshes of other climate zones. They are always characterized by the existence
of dunes and plants adapted to the aridity, and they often extend landward into
the sebkhas and alluvial plains.
Lagoons
Lagoons are numerous and varied along the Tunisian coasts. But according
to their morphology, hydrology, and position in comparison with the sea, they can
be classified into two main categories: (1) wide lagoons with continued
communication with the sea and (2) those isolated from the sea with a sandy bar,
and lagoons invaded only during the stormy season.
Four main lagoons belong to the first category:
• The Lagoon of Bizerte covers about 15,000 ha and connects to the sea
through a large channel, now partly developed.
• The Lagoon of Ichkeul (12,000 ha) is linked to the Bizerte Lagoon through
the Tinga emissary and responds to an important seasonal variation. It
is occupied by marine water only during the dry season. In the winter
it is the recipient of considerable continental discharge because of the
large wadis that divert into it.
• The Lagoons of Ghar el Mel ah (3,000 ha) and Tunis (4,000 ha) are cut off
from the sea by a sandy coastal bar, but connected to the sea by dredged
inlets.
1An arabic term for a flat area, close to the water table and characterized
by a salt material.
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Dues 7at/
• The Lagoon of Bhiref el Bibane, situated near the Libyan border, has a
surface of about 30,000 ha. It is bordered on the seaward side by a
consolidated littoral bar dating back to the Tyrrhenian. Connection with
the sea is possible through some natural inlets, among which the inlet
of S. Mohamed Chaouth is the most important.
Lagoons of the second category are connected to the sea only through natural
inlets that generally open only during storms. These lagoons are numerous and
exist in the Gulf of Tunis (St. Sidi Bakhoun, St. Ariana), in the eastern coast
of the Cap Bon peninsula (St. Bouzid, St. Klibia), in the Gulf of Hammamet (St.
Assa Jiriba, St. Halk el Mungil), and in the Sahel (St. Skanes, St. Dimass).
In all of these situations, the inland area is often swampy. The salinity
of the lagoons and the temperatures are often higher than in the open sea. They
also increase toward the south. In the Bhiret el Bibane Lagoon, for instance,
the temperature can climb as high as 40°C, and the salinity increases in the
summer when sirocco winds blow.
CONCLUSION
Given our inability to effectively address problems due to current relative
sea level rise, one might pessimistically assume that coping effectively with
accelerated sea level rise will be close to impossible. But there may be a
positive aspect: As late as 1983, for example, the United States was failing to
address current trends of sea level rise, but widespread public attention to the
greenhouse effect prompted officials to look into the issue of sea level rise and
to direct their staffs to at least take current trends into account. As the
paper by Klarin and Hershman (Legal and Institutional Implications, Volume 1)
illustrates, five years later officials were preparing for an accelerated rise.
The same thing could happen here. In Tunisia, there is sufficient technical
expertise to begin preparing for a rise in sea level, but neither the public
awareness nor the official recognition necessary to start the process.
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APPENDIX: ADDITIONAL DETAILS ON THE CLIMATE OF COASTAL TUNISIA
Some very important regional differences can be observed between the
northern and the eastern coasts, particularly in the rainfall volume and wind
characteristics. The mean annual rainfall is often higher than 500 mm and
sometimes reaches 1 m in the northern coast, whereas it is generally less that
300 mm in the major part of the eastern coast. Moreover, the rain average
diminishes rapidly toward the south. Near the Libyan border it is only about 100-
150 mm/yr. Rain is often torrential and falls in concentrated patterns of a few
days.
During the summer, the mean monthly temperature everywhere is greater than
20°C. The average daily maximum temperature during July and August is always
higher than 30°C and can reach 40°C when southern winds, the sirocco, are
prevailing. During the winter, the mean temperature of the coldest month
(January) is higher than 10°C almost everywhere along the coast. The mean
minimum temperature generally oscillates between 6° and 8°C. Temperatures are
rarely below 0°C.
The strongest and most frequent winds generally blow from the northwestern
direction and occur mainly in winter. Nevertheless, differences exist according
to seasons and the coastline orientation. On the northern coast, western and
northwestern winds prevail occurring approximately 35% of the time. On the
eastern and especially on the southern coasts, the gentler eastern and
northeastern winds dominate.
The contrast between the northern and the eastern coasts of Tunisia appears
also in the hydrodynamic and the marine water characteristics. Because of its
exposure to northern winds and its relatively deep water, the northern coast has
cooler, less saline, and rougher and larger waters than the eastern coast. At
the end of the hot season, water temperatures are about 21-22°C, and the salinity
is about 37 0/00 (parts per thousand). At the end of the winter, the
temperatures vary between 15 and 16°C, but the salinity is still almost unaltered
(36 to 37 0/00) except in the inner portion of the Gulf of Tunis. Unless there
is an exceptional storm, wave height along the northern coast rarely exceeds 6
m. In the Gulf of Tunis, waves of 1.5 m and higher represent only 6% of the
observed cases. Tides constitute a secondary phenomenon as their range is, at
spring tides, about 0.20 to 0.30 m.
Along the eastern coats, waves are mainly generated by the eastern and the
northeastern winds. They are generally characterized by a low energy. The most
important waves rarely exceed 1.20 m in height. From 1954 to 1961, the largest
wave registered at Sousse was only 3.5 m in height. The eastern coasts have a
broad shelf. The southern part (Gulf of Gabes) is characterized by important
tides. Here, the tidal range is often higher than 0.70 m and may reach 2 m at
spring tides. Water temperatures of the eastern coasts are always more than 16°C
and increase southward, where they are about 16-19°C and 22°C, respectively, at
the end of winter and summer. However, the salinity change is less perceptible
-- 37.1 and 37.2 0/00, respectively, at the end of the cool and the hot seasons.
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ACKNOWLEDGEMENTS
The author is greatly indebted to Prof. R. Paskoff and Prof. N. Psuty for
their help. J. Titus has revised and improved the text and proposed some
modifications in the English text. All of them are sincerely acknowledged.
BIBLIOGRAPHY
Oueslati, A. 1986. Jerba et Kerkna (iles de la cote orientale de la Tunisie):
leur evolution geomorphologique au cours du quaternaire. Publ. Univ. Tunis, 210
P-
Oueslati, A., R. Paskoff, H. Slim, and P. Trousset. 1987. Deplacements de la
ligne de rivage en Tunisie d'aprea les donnees de 1'archeologie a 1'epoque
historique. Coll. Intern. C.N.R.S. Paris, 67-85.
Oueslati, A. 1989. Les cotes de la Tunisie, recherches geomorphologiques. Th.
d'Btat, University of Tunis, 680 p.
Paskoff, R. 1985. Les plages de Tunisie. BDITEC, Caen. 198 p.
Paskoff, R., and A. Oueslati. Modifications of coastal conditions in the gulf
of Cabes (southern Tunisia) since classical antiquity. In: Journal of Coastal
Research (in press).
Pirazzoli, P.A. 1986. Secular trends of relative sea level (R.S.L.) changes
indicated by tide gauge record. In: Journal of Coastal Research, Special Issue
1:1-26.
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RESPONSES TO THE IMPACTS OF GREENHOUSE-INDUCED
SEA LEVEL RISE ON EGYPT
M. EL-RAEY
Department of Environmental Studies
University of Alexandria
Alexandria, Egypt
ABSTRACT
The projected sea level rise of 1 meter in the next century from greenhouse-
induced global warming is a serious concern to deltaic countries such as Egypt.
Deltas are particularly susceptible to sea level rise because the delicate
balance at the river-ocean interface produces land that is inherently just above
sea level. Deltas depend on new sediment delivered by rivers to enable them to
keep pace with sea level rise. Sea level rise will exacerbate the erosion
already present in the Nile River delta caused by dams upstream that have reduced
the sediment supply.
The population of Egypt is clustered along the banks of the Nile River and
within the delta. Only 3.5% of the one million square kilometer area of the
country is cultivated and settled (Quarterly Economic Review of Egypt, 1985).
The nation's coastline has experienced severe erosion in the last 100 years.
Reduction in the supply of sediment to the delta started with the construction
of delta barrages in 1881. Since then, the situation has become progressively
worse with construction of new dams. The 1964 construction of the Aswan High
Dam has completely stopped the supply of sediment to the delta; since that
time, many areas on the delta coast have been eroding 1 meter every year. In
some areas, erosion rates have jumped to more than 100 meters per year.
The impacts of global warming on the Nile delta are taken seriously by
concerned authorities in Egypt. A basic survey of available information and
implications has been compiled by Broadus et al. (1986) and Sestini (1989).
Sestini and others anticipated that a relative rise of 1 meter could submerge
lowlands 30 km inland of the coast or more, which accounts for 12-15% of Egypt's
arable land, 8 million people, and 10rl5% of the country's gross national
product. Salt intrusion will also contaminate water used for drinking
and agricultural purposes. Many people have called for a national policy of
response to these anticipated changes.
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Responding to sea level rise in Egypt will be difficult because most of
the arable land is along the Nile River or within the Nile delta. Therefore, when
this area becomes uninhabitable, moving to higher ground will not solve all the
problems, because this land will be inadequate for growing enough food to support
the displaced population. Other possible responses include building a dike along
the delta coastline or bypassing sediment around Aswan High Dam. This study
investigates the impacts of a 1-meter sea level rise on Egypt, assesses what is
at risk along Egypt's coastline, and discusses possible responses.
INTRODUCTION
Technological developments and the conversion of agricultural communities to
industrial communities have resulted in excessive use of energy resources. As
energy use is necessarily associated with waste in the form of materials and
heat, this waste has increased dramatically in the last few decades to the extent
that it has become a major threat to the environment. In particular, a gradual
increase of greenhouse gases (C02, CFCs, 03, CH4, and OH) in the environment has
resulted in a measurable warming of the atmosphere with anticipated changes in
climate, and additional effects such as sea level rise and changes in
precipitation patterns.
The impact of these climate changes on the ecosystem, human activities,
health, and welfare should be carefully assessed before a policy for
countering those impacts is developed. National and international organizations
have coordinated efforts to develop measures to adapt to these climate changes.
Models have predicted that the temperaotureriseassociatedwithaccumulation
of greenhouse gases may range from 2.5°C to 5°C by the middle of the
next century. The associated rise in sea level, due to both ocean thermal
expansion and melting of polar glaciers and ice caps, is anticipated to range
from 30 cm to 150 cm (Titus, 1986; UNEP, 1987, 1989).
Egypt's Nile delta, in particular, will be adversely affected because its
northern region is entirely less than 1 meter above sea level. It is already
subject to a great deal of environmental changes due to severe reduction of
sediment delivery after construction of the Aswan High Dam.
This paper outlines the impact of various environmental changes over the
northern Egyptian coasts, directs attention to areas of potential risk from the
effects of climate change, and recommends a policy by which government agencies
could reduce losses and help Egypt adapt to global warming.
IMPACTS ON THE NORTH COAST OF EGYPT
No formal multidisciplinary team has investigated the detailed impacts of
climate change on the Egyptian delta. However, a number of research centers have
studied one aspect or another of the problem and have accumulated valuable
information. These groups include the Institute of Coastal Research, the
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Institute of Oceanography, the Suez Canal Authority, the Environment Affairs
Authority,a nd the University of Alexandria research groups. A number of United
Nations Environment Programme meetings have also stressed the seriousness of the
impact of global warming, especially sea level rise.
An assessment of the impacts of climate changes on the northern Egyptian
coasts requires the documentation of detailed information on land use,
topographic variations, population distribution, soil characteristics, coastal
erosion, and socioeconomic distribution parameters. Unfortunately, the
information already available is outdated, intermittent, and, in many cases,
inconsistent. In addition, large uncertainties exist regarding the accuracy of
important variables, such as regional subsidence rates, elevation, and the
distribution of economic activities. Nevertheless, available information
provides a general account of the likely impacts.
A 1-meter interval elevation contour map of the Nile Delta and vicinity
(Figure 1) shows that the area below the 1-meter contour extends inland as much
as 30 km south of Alexandria city and south of Lake Manzala (Sestini, 1987).
Because about 40% of Egyptian industry is located near and around Alexandria,
we can infer that serious damage could result from a 1-meter rise in sea level.
In addition, because of the sandy and porous nature of the soil in this area,
waterlogging resulting from saltwater intrusion may affect the fertility of the
arable land below the 2-meter or perhaps the 3-meter contour. Considering the
relatively high population density and extensive resources of the area, a
tremendous socioeconomic impact would be likely.
Recent analysis of erosion and accretion patterns (Frihy et al., 1989) has
also shown large changes over the northern Egyptian coasts. Hence, many tourist,
recreational, and economic sites will be subjected to considerable stress. In
addition, this area is generally subsiding. Based on these results and on
consideration of economic development axes in both vertical and horizontal
directions on the north coast (ARICON, 1988), we conclude that sea level rise
will pose major risks to three areas: the Alexandria region west of the Rosetta
branch, Lake Burullus and vicinity, and the Lake Manzala region.
1. Alexandria region: The region at risk includes residential areas in
several localities, in addition to industrial sections west and east
of the city. A large part of the area south of Alexandria city
(Amerya) is also below the 1-m contour level. These areas are
presently under extensive development. Plans for development in this
area should be carefully revised. Some tourist sites west of
Alexandria are also built between the first ridge and the sea (at
localities below the 1-meter contour), which puts them at risk. This
region hosts about 40% of Egypt's industry, as well as many historical
and tourist sites.
2. Lake Burullus: This area is already subject to serious erosion and
accretion problems. Rising sea level will increase this rate and
destroy beaches and resort villages in the area. In addition, the lake
is under consideration for a water storage project. The environmental
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MEDITERRANEAN SEA
BALTIM
ROSETTA
ALEXANDRIA
jj/iV-j Wetlands (
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El-Raey
A detailed quantitative environmental impact assessment should be carried
out based on use of geographical information systems, making use of the
information on the northern coasts already existing at the University of
Alexandria and other research centers. A multistage technique in which the
impact could be calculated by an interaction matrix for each 0.25 meter of sea
level rise is suggested. An interaction matrix with elements of the "magnitude"
and "importance" of the impact should be calculated for each area. The elements
of such a matrix could be estimated from accurate analysis of geographic
information systems based on recent data of the area.
ADAPTIVE OPTIONS
If sea level rises, Egypt has only three options:
Withdraw from coastal areas;
Build walls around limited areas to protect valuable lowlands or
industrial complexes from inundation; or
Adjust to expected changes, and perhaps take advantage of them by
appropriately changing land use (e.g., shifting to crops that tolerate
flooding).
Because of the variable environmental and economic conditions in the
vulnerable areas, the choice of any of these options will greatly depend on the
area under consideration. A detailed study of each area is, therefore,
necessary.
Alexandria city is built over a number of relatively high hills or dunes
separated by narrow "tunnels" (Figure 2). It may be possible to protect the
urban and industrial areas against rising seas by building a number of walls
to protect the southern parts of the city. However, such a response must await
accurate analysis of data and studies of geological structure and elevation of
these hills.
In general, any policy that would be of interest for future development in
the area must be of the type that will help whether or not climate changes --
i.e., it must a two-sided policy. Conserving energy and water resources and
converting to salt-tolerant agriculture are policies of this type. Broadly
speaking, response strategies fall into two categories: limiting global warming
and adapting to its consequences.
Limiting Global Warming
This approach is intended mainly to buy time:
1. Limit the production and emission of C02, CFCs, and other greenhouse
gases. Enforce air pollution control measures. Apply the Clean Air
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Mediterranean
Abu-Qir
Abu-Qir Gull
Alexandria Topography
Delta Deposits
Present Borders of Lake Mariut
Regions From Lake Mariut That
MEDITERRANEAN SEA
Have Been Drained
024
Raas-EI-Teen
Alexandria Harbor
Breakwater
Raas-EI-Agami A Sea Gulf
Mariut Valley
AI-Mex-Abu-Sir Dunes
Om-Gaghyu Island
AI-Amereya 2go 50
Figure 2. Alexandria outskirts showing ridges over which the city is built.
Act in Cairo, Alexandria, and Tanta, at least, and enforce it by
efficient monitoring networks.
2. Develop and enforce the operation of more energy-efficient engines.
Increasing engine efficiency is found to be one of the most important
factors in reducing greenhouse emissions (Lashof and Tirpak, 1989).
Include a social impact tax in the price of polluting fuels to limit
their excessive use.
3. Work on planting greenbelts, and increase the awareness and perception
of the public concerning overuse of fertilizers. Encourage and support
programs for environmental education and research.
4. Increase the proportion of solar energy use and/or other renewable
energy sources, such as wind energy. Support programs for studying
and implementing energy conservation techniques.
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El-Raey
Adaptation
Adapting to global warming involves long-range planning. For instance,
one of the most important problems developing countries are expected to face in
the near future, with special reference to Egypt, is the availability of
freshwater. With a population growth rate of 2.8% per year, future domestic
water use is expected to consume a large part of Egypt's fixed water budget
(55 million cubic meters per year). In view of the projected global warming,
water conservation programs must start -- the sooner the better -- whether we
have climate changes or not. Other adaptation policies for Egypt include the
following:
1. Adopting new agricultural practices with improved efficiencies for
using freshwater resources.
2. Encouraging and developing multidisciplinary institutions concerned
with the real location and use of scarce freshwater supplies, such as
groundwater resources. Developing techniques for rainfed (as opposed
to irrigated) agriculture. Supporting projects based on rainfall along
the north coast.
3. Strengthening mechanisms for converting land and other resources into
and out of agriculture in response to climate change.
4. Adopting a new policy for urban development of coastal regions based
on predicted sea level rise for the next 40 or 50 years. For instance,
resort villages with massive foundations are currently built on ridges
parallel to the shore. In the future, only transportable wooden cabins
should be allowed near shores.
Special policy recommendations for the northern coastal region include the
following:
1. Plans for building an international road along the north coast consider
enforcing road foundations to act as a wall for protecting the Nile
delta in case of sea level rise. The same could be extended to
vulnerable areas west of Alexandria.
2. Reevaluate the Alexandria and Damietta master plans, based on new
predictions. Build future massive beach resorts on the ridges at least
1 meter above sea level.
3. Launch a socioeconomic program directed toward increasing public
awareness that rainfall patterns may change. Use recent
biotechnological capabilities of saltwater-tolerant plants.
4. Develop and implement techniques for reducing water table levels over
existing lowlands and human settlements near the coastal regions.
Develop windmill techniques of water pumping, and test capabilities
in pumping already waterlogged areas in Agamy west of Alexandria.
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Mediterranean
5. Control the overexploitation of quarries along the coasts west of
Alexandria.
6. Relocate waste dumping to suitable sites to reduce future risk of water
pollution.,
7. Investigate the technical and economic possibilities of protecting
Alexandria city by building a number of discontinuous walls over
"tunnels," and using local natural rocks, such as granite, basalt,
dolomite, and diorite.
8. Delineate and study regions of erosion and accretion for better
evaluation of conditions along the northern coasts and identification
of areas most vulnerable to sea level rise.
9. Encourage the reclamation projects to take place in areas with greater
elevation. Extend public services to newly developing communities in
the highlands, giving first priority to people from vulnerable areas
to move to these newly developed lands.
10. Explore the technical and economic feasibility and impact assessment
of bypassing Nile River sediments from Aswan High Dam.
As a first step, a multidisciplinary team of experts should be formed to
carry out a detailed environmental impact assessment of the effects of sea level
rise and to recommend specific measures to counter these effects. The same
exercise should then be carried out for other effects of climate change.
ACKNOWLEDGMENTS
The author acknowledges valuable discussions with Dr. S. Nasr from the
Department of Environmental Studies, and with Dr. 0. Frihy from the Institute
of Coastal Research.
BIBLIOGRAPHY
ARICON. 1988. Master plan for development of the north delta
region and international road. Cairo, Egypt: Ministry of Reconstruction, New
Communities and Infrastructure.
Broadus, J., J. Millman, S. Edwards, D. Aubrey and F. Gable. 1986. Rising sea
level and damming of rivers: Possible effects in Egypt and Bangladesh. In:
Effects of Changes in Stratospheric Ozone and Global Climate, Vol 4: Sea Level
Rise. J.G. Titus, ed. Washington, DC: U.S. Environmental Protection Agency and
United Nations Environment Program.
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Frihy, O.E., S.M. Nasr, M.H. Ahmed, and M. El-Raey. Long term shoreline and
bottom changes of the inner continental shelf off the Nile Delta, Egypt.
(Submitted).
Lashof, D.A., and D.A. Tirpak. 1989. Policy Options for Stabilizing Global
Climate. Washington, DC: U.S. Environmental Protection Agency.
Quarterly Economic Review of Egypt. 1985. Annual Supplement. London: The
Economist Publications Ltd.
Sestini, G. 1989. The implications of climatic changes for the Nile Delta.
Report WG 2/14. Nairobi, Kenya: United Nations Environment Program/OCA.
UNEP. 1987. United Nations Environment Program. Environment Library No. 1.
Geneva: United Nations Environment Program.
UNEP. 1989. United Nations Environment Program. The Full Range of Responses
to Anticipated Climatic Change. Geneva: United Nations Environment Program.
April.
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IMPACTS OF SEA LEVEL RISE ON PORTS AND
OTHER COASTAL DEVELOPMENT IN ALGERIA
EL-HAFID TABET-AOUL
Laboratorire d'Etudes Man'times
30 Rue Asselah Hocine Alger
Algiers, Algeria
INTRODUCTION
More and more, the public is recognizing that global warming due to the
"greenhouse effect" will increase the mass and volume of the water in the oceans
and will thereby accelerate the rate of sea level rise during the next few
decades. Such a rise would increase coastal erosion and other hazards of coastal
life.
Due to the seaward advance of deserts and rising sea level, the coastal
zone of North Africa is becoming narrower. At the same time, population growth
is causing rapid urbanization. Thus, it is important today to create strategies
for adapting to the global warming of tomorrow.
SEA LEVEL TRENDS IN THE MEDITERRANEAN SEA
The Mediterranean shore has been populated since the beginning of recorded
history. Ancient civilizations have left a great number of remains on the coast,
which can be very helpful in addressing the impacts of sea level rise. As early
as 1934, His Highness Prince Omar Toussoun ordered a study to determine how much
the sea level had risen in the port of Alexandria, Egypt.
Most people along the Mediterranean coast have not noticed the sea rising,
but that does not mean it is not occurring. Tidal gauge records in Marseilles
show that the sea level has been rising 1 mm per year there for the last century
(Bruun, 1987). This rise may be limited by the region's climate. For example,
the Mediterranean Sea is already an area of net evaporation, which tends to lower
sea level. Moreover, seasonal variations may obscure the sea level. As Figure
1 shows, seasonal variations can be 100 times the annual rise.
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Mediterranean
1900
DATE
Figure 1. Yearly evolution of mean sea level in Trieste, Italy, which is a good
approximation of trends on the Algerian Coast.
POSSIBLE IMPACTS ON ALGERIA
For Algeria, the most important problems resulting from sea level rise are
likely to be the loss of usable land, damage to port facilities, and pollution
of groundwater.
Loss of Usable Land
The continental shelves in the western part of the Mediterranean Sea are
rather narrow -- less than 25 miles wide -- and are cut by numerous canyons.
Along the Moroccan and Algerian coasts, the shelf slopes an average of
approximately 10%.
Above the sea, the limited width of the vital belt confined between the
desert and the sea implies that national population growth will increase the
urbanization of the coastal zone. In Algeria, more than 50% of the population
lives within 50 kilometers of the sea (Figure 2).
Park et al. (1986) forecast that 40 to 75% of existing U.S. coastal wetlands
could be lost by 2100. A similar impact can be expected in Algeria.
Quays and Port Facilities
Given the low tidal range (less than 50 cm) in the Mediterranean Sea, port
facilities have been designed with levels close to sea level. In Algeria, ports
are designed with quays up to 2.0 m above sea level. A rise in sea level would
flood these structures as well as the operational land behind.
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Tabet-Aoul
Because of the importance of maritime trade, which represents more than
90% of the total amount of the Algerian trade exchange, port designers should
bear in mind the possible effects of sea level rise in future port construction.
Fortunately, existing structures can be elevated as the sea rises.
Groundwater Pollution
Most of the cities on the North African coast are supplied by groundwater.
A rise in sea level will cause saltwater to contaminate the groundwater.
Regarding soil permeability and smooth groundwater table slope near the shore,
large quantities of freshwater will be lost, proportional to the rise in sea
level.
WHAT CAN BE DONE
Along the North African coast, both structural and planning measures will
be necessary.
Rigid structures, such as breakwaters, seawalls, and groins, can protect
urban areas. However, given their high cost, these structures would be
appropriate only where there are valuable buildings or land. If structures are
destroyed by storms or other phenomena, they should not be rebuilt.
Alger
Figure 2.
STATISTIOUES O. N.S H! 21 -ALGERIA
Algerian cities with more than 100,000 inhabitants,
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Mediterranean
In rural areas, rigid solutions would not usually be justified economically.
More flexible measures may be appropriate such as setback lines that prohibit
construction in areas likely to be inundated within a specified period of time
(up to 100 years). New construction criteria should be defined. However, the
difficulty will be to convince officials to accept the loss of
precious land today to prevent the consequences of something that will happen
in the 21st century.
BIBLIOGRAPHY
Bruun, P. 1987. The effects of changing the atmosphere on the stability of sea
level and shore stability. PIANC 58:129-132.
Bruun, P. 1989. Coastal engineering and the use of the littoral zone. Ocean
and Shoreline Management 12(5) and (6).
Lamy, A., and C. Mi Hot. 1981. Bottom pressure and sea level measures in the
Gulf of Lions. Journal of Physical Oceanography 11:394-410.
Park, R., T.V. Armentano and C.L. Cloonan. 1986. Predicting the effects of
sea level rise on coastal wetlands. In: Effects of Changes in Stratospheric
Ozone and Global Climate. Volume 4: Sea Level Rise. J.G. Titus, ed.
Washington, DC: United Nations Environment Programme and the U.S. Environmental
Protection Agency. October.
Sharaf el Din, S.H., and Z.A. Moursy. 1977. Tide and storm surges on the
Egyptian Mediterranean coast. Rapp. Comm. Inter. Mer Medit. 24:2.
Vignal, J. 1935. Les changements du niveau moyen des mers le long des cotes
en Mediterranee. Annales des Ponts et Chaussees 28.
Weaver, D.F., and D.L. Hayes. 1989. Proposed response to sea level rise by a
local government. In: Coastal Zone '89. New York: American Society of Civil
Engineers, pp. 2490-2501.
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NORTH AND WEST EUROPE
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THE VULNERABILITY OF EUROPEAN COASTAL LOWLANDS
ALONG THE NORTH SEA AND ATLANTIC COASTS
TO A RISE IN SEA LEVEL
DR. SASKIA JELGERSMA
Geological Survey of The Netherlands
P.O. Box 157
2000 AD Haarlem, The Netherlands
ABSTRACT
The European coastal lowlands comprise deltas and plains including wetlands
and natural areas at low altitudes that encompass extensive zones of densely
populated, intense economic and agricultural activity. Around the southern North
Sea Basin alone, the coastal plains area is the home of more than 200 million
people who live close to present sea level and are already at risk from
inundation as a consequence of coastal erosion, storm surge, and the current
trend of sea level rise of 1 to 1.5 mm per year.
During a session on the impact of a future rise in sea level, part of the
European Workshop on Interrelated Bioclimatic and Land Use Changes, 12 papers
presented case histories on the present situation of the shoreline. The
consensus was that European coastal lowlands are already experiencing damage from
erosion, inundation during storm surges, storm waves, subsidence, and saltwater
intrusion as the consequence of sea level rise, increased incidence of
storminess, and human activities.
Moreover, many human activities are increasing the vulnerability of coastal
areas to a rise in sea level. These activities include sand extraction from
beaches and offshore areas for reclamation and the construction industry; the
destruction of natural shoreline defenses, such as sand dunes, to provide hotel
accommodations and amenities for the tourist industry; the interruption and
diversion of longshore sediment transport by groins, jetties, and harbors; the
reduction of the sediment load of rivers by water management in drainage basins
and the construction of dams and reservoirs, cutting sediment supply to nourish
beaches and deltas; the canalization of rivers for navigational purposes; the
reclamation of coastal lowlands for agricultural, industrialization, and
residential development; and the extraction of groundwater for drinking water and
irrigation, which has led to subsidence and the penetration of saltwater.
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North and Vest Europe
The maximum rise of sea level during the recent geological past did not
exceed 2.2 m/100 years. During the past 4,000 years, when the rate of rise was
considerably less, sedimentation has kept up with and locally exceeded sea level
rise. In natural areas, where human activities are not pre-eminent, such as the
Dutch, German, and Danish Madden Sea, sedimentation has kept up with the present
rise of sea level of 10 to 15 cm/100 years. Investigations of the sediments of
the coastal lowlands indicate that, given a natural sediment budget, these areas
responded and adjusted to a range of rates of sea level change and climatic
change in the past.
The coastal lowlands of Europe have a good infrastructure. Accordingly,
they will be able to address future sea level rise more easily than countries
that have none, e.g., the Third World. Nevertheless, in both rich and poor
nations, the socioeconomic impacts of a future sea level rise will be profound
and widespread.
INTRODUCTION
As the report of the Miami conference notes, people have always been
concentrated near the coast. Although the general lack of topographic
information has made it impossible so far to estimate how many people live within
one or two meters of sea level, we do know that about half of the world's
population lives in deltas and other coastal lowlands. In most cases, deltas are
entirely less than ten meters above sea level; and in many cases at least half
the delta is within one or two meters of sea level. Even for the portions with
greater elevations, life is affected by sea level because the heights of river
and storm surges are influenced by the base level of the sea.
For purposes of this paper, we define coastal lowlands as areas that are
within coastal floodplains or would be without manmade coastal protection
structures. Besides flooding, most of these areas are already subject to erosion
and saltwater intrusion because of rising sea level and, mainly, as a result of
human interference with the natural flow of rivers to the sea and sediment along
the coast.
Even a large part of relative sea level rise stems from subsidence induced
by human activities, such as withdrawals of groundwater, oil, and gas, and
drainage of land and the resulting compaction of peat and clay underlying it.
In some cases -- such as the Netherlands -- the fact that relative sea level rise
and its consequences are already being faced would make communities less
vulnerable to global warming because physical and political infrastructures to
address the problem already exist. In other cases, existing subsidence has
eliminated the safety margin that might otherwise have allowed communities to
tolerate the projected rise in sea level over the next 50-100 years.
This paper summarizes the implications of sea level rise for low-lying
coastal areas around the North Sea and the Atlantic coast of Europe.
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Jelgersma
ENVIRONMENTAL CONDITIONS
Coastal lowlands comprise the lands where sediments are deposited by tides,
storm surges, and some areas flooded by river water -- namely, those in which
flooding results because of the backwater effect from the sea. The sediment
deposited includes peats, clays, silts, and sands generally lying below the
present spring tide level; at slightly higher altitudes, they also lie along the
inland margins of the coastal lowlands. Although coastal lowlands are usually
within a few meters of sea level in the case of coastal dunes they can accumulate
to several tens of meters above sea level.
The coastal lowland itself shows a great variety of morphology and
lithology. Rivers entering the sea can have deltas that show great variation due
to dominant processes of waves, currents, and fluvial input. If river input is
low and/or the tide ranges are relatively great, estuaries are found instead.
Inland from the shoreline, there are generally coastal wetlands, with zonations
primarily dependent on the vegetations' tolerance of salinity and frequent
flooding.
Along certain coasts, coastal barriers with dunes on top of them and barrier
islands can occur with coastal wetlands in the hinterland. During the Holocene
rise in sea level, these zones of different environments have shifted landward;
if sea level rise accelerates, their landward migration will do likewise.
There are no important deltas in northern and western Europe. Most of the
rivers end in estuaries, like the Elbe, Weser, and Ems estuaries in Germany; the
Rhine and the Meuse Scheldt estuary in the southwestern Netherlands; the Severn
and Thames in England; the Somme, Seine, and Gironde estuaries in France; the
Tajo estuary in Portugal; and the Guadalquivir estuary in Spain.
In large measure because of the configuration of the southern North Sea
Basin, storms from the north and west can produce extremely high tides, which
have caused severe flooding many times throughout the last several centuries.
This configuration also contributes to large tidal ranges: macrotidal (>4 m)
conditions prevail along the English Channel, along the Strait of Dover, and in
the Bristol channel. The highest tidal range of Europe can be found in the Bay
of Mont-Saint-Michel (12 m) in France. Figure 1 roughly indicates the coastal
lowlands, the river estuaries, and the delta.
LAND USE
For centuries, Europeans have drained and reclaimed wetlands for
agriculture, industry, and housing of large cities. The draining has caused land
subsidence through compaction of peat and clay soils; moreover, land surfaces
have also been lowered because the compaction of unconsolidated sediments --
which would be occurring even without human interference -- is no longer offset
by the deposition of sediment from floods. In many areas, compaction has been
so great that these soils are now lying below mean sea level. Accordingly, they
have to be drained by pumping, and many areas are protected by dikes against
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North and Vest Europe
storm surges and high tides. The only extensive natural areas left are the tidal
flats of the Dutch, German, and Danish Madden Sea.
An important side effect of this intense drainage is the intrusion of
saltwater. The damming of rivers diminishes the freshwater flows that would
otherwise push saltwater back toward the sea. Dredging in the estuaries and
deltas in the interest of port development has also caused saltwater intrusion
farther upstream. This shift of saline water has affected the intake of water
from the river for irrigation and other water supplies. Yet another side effect
is saltwater intrusion in coastal aquifers (see Titus in the section on Problem
Identification).
The coastal lowlands of Europe, especially the river estuaries and deltas,
are areas of dense population and heavy industrial activity. More details about
human activities, land use, and vulnerability to flooding, especially by a rise
in sea level, should be given on smaller scale maps by the European countries
involved. An example is the maps of the southern North Sea Basin. In the
region, about 20 million people live below the high-tide level. The economic
value of these low-lying areas is enormous. These areas are also gateways to
industrial areas in the hinterland as well as oil and gas fields; there is a
heavy concentration of pipelines, refineries, and oil harbors in the southern
North Sea. The population density and important industries in the coastal
lowlands surrounding the southern North Sea Basin make them very vulnerable to
sea level rise.
EFFECTS OF A FUTURE RISE IN SEA LEVEL
An accelerated rise in sea level would (1) increase the risk that reclaimed
lowlands will be inundated; (2) accelerate coastal erosion, threatening both
structures and recreational beaches; (3) increase the risk of flood disasters;
(4) impair the effectiveness of drainage systems; (5) increase saltwater
intrusion into groundwater, rivers, bays, and farmland; (6) damage port
facilities; (7) threaten the wetland habitats of birds, fish, and wildlife; (8)
shift sedimentation in rivers farther upstream, hampering shipping; and (9) alter
tidal ranges, which might exacerbate many of the other effects.
Other impacts of global warming could also be important. If wind patterns
and climate change, the runoff from rivers will increase in winter and decrease
in summer. The increased runoff can create problems for the embankments, and a
decreased runoff can cause extensive saltwater intrusion upstream. Increased
storminess could be even more important: the most significant damages on
coastlines occur during storm surges at the time of high tide. If this increase
in storminess should occur along the coasts of the southern bight of the North
Sea, the highly populated, industrialized coastal lowlands would suffer
disastrous losses.
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Jelgersma
RESPONSE TO SEA LEVEL RISE
How can the coastal lowlands of Europe respond to the predicted rise in sea
level? They can either try to defend the lowlands or move present activities and
development landward. The land can be protected by dikes, seawalls, beach
nourishment, and other engineering solutions, but economic and environmental
impacts can make such a protection strategy unacceptable. On the other hand,
moving present activities landward also will have serious economic and social
effects. Well-developed countries such as a united Europe will have the
organization, the technology, and the resources to make these tradeoffs, unlike
less developed countries, which lack the above-mentioned infrastructure.
Sea level rise and the implementation of response strategies will have
serious effects on individual, regional, and national economic levels. Impacts
on real income include the loss of production from land and seas as well as the
effects of employment changes from reconstruction. Migration of people and
enterprises will disrupt existing economic and social structures.
Many European coastal lowlands are in critical balance with the present sea
level and are in great danger of flooding if storm surges occur. Important parts
of the shorelines are affected by erosion, especially during storm surges. At
places where shorelines are eroding, stone jetties and concrete or wooden groins
are built to lessen sand draft. This method is disputable because it seems to
be causing more erosion on the rest of the unprotected shoreline. Beach
nourishment seems to be a more successful method of protection.
But a strategy is more than a set of physical structures or laws governing
what and where people can build. We need to systematically analyze which areas
are vulnerable, as well as the legal, environmental, economic, and cultural
implications of each of the possible responses. Only then will it be possible
to rationally respond to the risks of accelerated sea level rise.
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IMPACT OF A FUTURE SEA LEVEL RISE IN THE
POLISH BALTIC COASTAL ZONE
KAROL ROTNICKI & RYSZARD K. BOROWKA
Department of Paleogeography
Quaternary Research Institute
Adam Mickiewicz University
Fredry 10, 61-701 Poznan, Poland
ABSTRACT
About 3,645 square kilometers of land (1.2% of the total area) in Poland are
less than 20 feet above mean sea level. The area at greatest risk, located below
1 m above sea level, is 1,550 square kilometers, of which 70% lies in the delta
of the Vistula and 12% lies in the lower Odra valley and around Szczecin Bay.
The remaining 18% below 1 m elevation is in a 300-km section of the coast between
Wolin Island Hel (at the end of the Hel Spit). These areas have 1.8% of Poland's
population.
In the area at risk, there are four large shipyards with capacity equal to
2% of world production, a large chemical plant at Police, an oil refinery in
Gdansk (processing 6 million tons/year), railway junctions, plants of the
machine-building industry, the lower Odra power plant, and the whole of the old
city of Gdansk, a priceless cultural center. Within the low-lying area, there
are 28 holiday resorts and sandy beaches. Eighteen holiday resorts are situated
above the cliffed coast and are exposed to erosion rates of 40-150 cm/yr.
At present, the awareness of the impacts of sea level rise is low, both in
society in general and in the administrative units.
INTRODUCTION
Intensive emission of C02 induces the so-called greenhouse effect. This
will increase global temperature, which will bring about a faster melting of
glaciers and inland ices, as well as thermal expansion of the ocean water.
Forecasts indicate that during the next 100 years, these factors may cause sea
level to rise from 50 to 200 cm. This rise will pose a number of threats to the
natural and cultural environments of the coastal zones of maritime nations.
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North and West Europe
NATURAL FEATURES OF THE POLISH COASTAL ZONE
Sea Level Changes and Storm Surges
Changes in coastal water levels in Poland have been recorded by 21
marigraphic and gauging stations (Figure 1), many of which have been operating
for the last century. A clear cycle of changes in the sea level can be observed
in periods of 19-20, 7-11, and 3-5 years. The first two are connected with
changes in the activity of the sun; the origin of the last cycle is obscure
(Jednoral, 1984; Dziadziuszko and Jednoral, 1987). The regression lines and
equations show that there has also been a gradual rise in sea level over the last
hundred years (Figure 2). The tendency has accelerated markedly in recent years.
The mean annual sea level rise over more than a hundred years amounts to +0.7
mm/yr in Swinoujscie, +1.1 mm/yr in Kolobrzeg, and +1.2 mm/yr in Gdansk. For
the last 35 years (1951-85), the rate of rise is generally higher, reaching +1.4
mm/yr in Swinoujscie and +2.9 mm/yr in Gdansk.
Poland experiences severe storm surges. Surges greater than 570 cm have
a probability of 0.75% in any given year. From 1951 to 1975, storm surges
occurred very irregularly, from none to seven in a year (Majewski et al., 1983)
(Figure 3). Over the last 700 years, 82 storm surges have exceeded 1.2-1.5 m.
In 31 of these cases, sea level rose by more than 2.5 m (maximum <3.0 m),
exceeded 600 cm, and none was higher than 650 cm (Jednoral, 1984). During the
period of systematic observations, the highest intensity of storm surges took
Figure 1. Wind conditions, air temperature and precipitation (A), directions of
longshore currents (B) along the Polish coast.
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E
o
520
500-
480
Swinoujscie
Rotm'cki and Borowka
.••It
1860 1880 1»OO 1920 1940 1960
E
o
520-1
500-
480-
Kotobrzeg
1860
1880
1900
1920 1940 1960 1980
E
o
520
500-
480-
1860
Ustka
1880
1900 1920 1940 1»6O 1*«O
E
o
520-I
500-
480-
Gdahsk
1860 1880 1900 1920 1940 1960
1980
years
Figure 2. Sea level rise during the last century in the Polish coastal zone.
(Czekanska, 1948). From 1951 through 1980, 88 storm surges occurred; 15 of these
249
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North and Vest Europe
RECURRENCE INTERVAL (YEARS)
1.5 2 5 10 20
500
.99 .9 .7 .5 .3 1 .05 .02 .01
PROBABILITY OF BEING EXCEEDED IN ONE YEAR
.001
Figure 3. Probability of storm-surge height and of number of storms per year
in the Polish Baltic coastal zone. Probability curves counted on the ground of
data published in Majewski et al. (1983).
place at the turn of the 19th century. About 55% of storm surges develop
withwinds from the north, 31% from the northwest, and 14% from the northeast.
The northeast wind creates the highest and most dangerous storm surges.
River mouths are important sources of longshore material and are also zones
of discontinuity in the dune belt. Therefore, they are places where storm surges
can penetrate the coastal barriers onto usually low-lying areas behind them.
On the Polish coast of the Baltic are the mouths of two rivers with drainage
basins exceeding 100,000 km2 (the Vistula and Odra Rivers) and six rivers with
basin areas of 1,000 to 3,000 km2 (Figure 3).
Geomorphology
The 493-km Polish coast consists of alternating cliffed (105 km) and barrier
beach sections (373 km). Swampy coastal sections occupy about 15 km (Figure 4).
The cliffs are 15-40 m high, with a maximum of 90 m; 45 km of cliffs are
retreating between 0.4 and 2.3 meters per year. At the cliff base one can
observe low beaches (0.4-0,8 m) with one or no submerged sandbars in the breaker
zone (Rosa, 1984). A striking example of coastal erosion is the ruins of the
church at Trzesacz, which was built in the 12th century about 1,800 m from the
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Rotm'cki and Borowka
Figure 4. Geomorphology of the Polish coastal zone. 1 - ground moraine plateau,
2 - end moraine hills, 3 - alluvial and glaciof-luvial plains, 4 - glacio-
lacustrine plains, 5 - swampy plains, 6 - cliffed coasts, 7 - barrier coasts,
8 - mean annual rate of the cliff abrasion (meters per year - in numerator) and
cliff height (in meters - in denominator).
coast. Figure 5 shows the church and other areas threatened by erosion. Figure
6 illustrates structural response to this erosion.
Coastal barriers are especially well developed in the eastern and middle
parts of the Polish coast. They separate old marginal valleys and terminal
depressions of the last inland ice from the sea, allowing coastal lakes and
swampy plains to form. On the Polish coast three types of barriers can be
distinguished:
1. Barriers of a modest width (<0.5 km) occupied by a single row of dunes
3-6 m high. They are already susceptible to destruction by storm
surges, especially because the adjacent beaches are low (0.6-0.8 m).
2. Wide barriers (<2.0 km) occupied by several rows of dunes with heights
up to 20 m. Beaches extend up to about 1.0-1.2 m above sea level.
3. Wide barriers (about 2 km) occupied by complexes of parabolic and
barkhan dunes that are 20-50 m high. Foredunes can be found only near
the beach, and their heights vary from 3 to 10 m. On the Leba Barrier,
for example, there are also fields of migrating dunes with barkhans
shifting east by about 10 meters per year.
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B
ro
en
ro
Figure 5. Coastal erosion in Poland.
(A) Ruin of the church at Trzesacz (middle
coast), which was 1.8 km from the Baltic coast
when it was built in the 12th century.
Tetapads have subsequently been installed
to slow cliff erosion.
(B) The town of Ustronie Morskie (middle
coast) is also threatened by cliff erosion.
-------
ro
en
CO
(D) Leba Barrier (middle coast)
when erosion of foredunes has
exposed underlying peat.
(C) Swimmers and sunbathers at Wolin Island
(western coast) where the cliff has been cut
into glacial and fluvial glacial Pleistocene
deposits.
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B
no
en
Figure 6. Erosion protection in Poland.
(A) Sarbinowo (middle coast). Concrete block
and concrete band protect the cliff against
erosion.
(B) Fishing village Kuznica on the Hel spit
(eastern coast.) Boulder and clay ridge and
piles of concrete sleepers protect the coast
where foredunes have been destroyed by storm
surges.
(C) Hel Spit near village Kuznica.
Artificial beach built of sand pumped from
the bottom of the Puck Bay.
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Rotm'cki and Borowka
There are also well-developed spits. Hel Spit is being intensively
destroyed by erosion at present, especially in its western part. This process
started with the construction of the harbor breakwaters of Wladyslawowo in 1938,
located at the base of the spit.
Along the Polish coast are two large estuaries: Szczecin Estuary (687 km2),
the Vistula Estuary (838 km2), and some coastal lakes with a total area of about
196 km. Low-lying wetlands behind barriers are commonplace (Figure 4),
particularly in the deltas of the Vistula (ca. 1,650 km2) and Odra Rivers (ca.
300 km2) as well as numerous late glacial marginal valleys. A substantial part
of these areas, especially on the Vistula Delta, are depressions with an
elevation of -1.8 m below sea level. Since the 15th century, people have
controlled the hydrologic conditions of the wetlands; hence a rise in sea level
would not necessarily inundate them, but it would require increased pumping.
CULTURAL AND ECONOMIC FEATURES OF THE POLISH COASTAL ZONE
Land Use of the Low-lying Areas
The Szczecin Estuarine area and the lower Odra valley areas lie less than
1 m above sea level. These areas are mainly wet meadows and grazing land,
similar to areas on Poland's middle coast. Areas between 2 and 5 m above sea
level are mostly arable land. In the Vistula Delta (1,653 km2), embracing 47%
of the low-lying areas of the Polish coastal zone, agricultural land takes up
77%, and nonagricultural land, 23%. Of the agricultural land, 62.5% is in
cultivated fields and 37.5% is in meadows and pastures (Matusik and Szczesny,
1976).
The Vistula Delta has very good soils that have facilitated the development
of intensive agricultural production. A substantial part of the low-lying areas
of the Polish coastal zone (1,835 km2) is in polders, of which 555 km2 are in
depressions (Cebulak, 1976, 1984). About 67% of the polders are in the Vistula
Delta, 18% on the middle coast, and 15% in the Szczecin region. The polders are
protected by a system of dikes: 975 km of dikes in the Vistula Delta, 22 km on
the middle coast, and about 250 km in the Szczecin area (Cebulak, 1984).
Population
The Polish coastal zone comprises 28 towns, which in 1985, were inhabited
by 4.2% of the total population of Poland (i.e., 1.6 million people); of this
total, 83% live in six towns: Gdansk, Szczecin, Gdynia, Elblag, Swinoujscie, and
Sopot (Figure 7). In 13 of these towns, 50-100% of the land is 0-5 m above sea
level. Only 5-40% of the remaining towns lie less than 5 meters above sea level.
Jointly, the low-lying areas of the Polish coast are inhabited by about
680,000 people -- i.e., 1.8% of Poland's population. Approximately 52% live in
the Gdansk-Gdynia-Sopot agglomeration, 23.5% in the Szczecin region, and 13.6%
in the Vistula Delta. The remaining 11% are dispersed along a 300-km-long coast
between Wolin Island and the tip of Hel Spit. The density of the population of
the coastal belt lying less than 5 m above sea level is 193 persons/km2, of which
25-26 persons/km2 live in rural settlements.
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Wort/? and West Europe
annual trans-shipment in ports
in million tons (in 19791
annual ship production
in thousand DWT (in 1979)
7 fishing ports and annual fish
discharging in thousand tons
(in 1976)
holiday resorts with sandy beaches:
fa situated on a cliffed coast
A situated on a dune coast
0 45 km
Figure 7. Cities, ports, shipyards, and holiday resorts at the Polish Baltic
coast. Black sector in the circle marks the part of the city threatened by a
future sea level rise.
Ports and Industry
The largest Polish port is Goteborg, which lies on the Baltic. Poland has
four other large ports: Szczecin and Swinoujscie on the west coast, and Gdansk
and Gdynia on the east coast (Figure 7). The joint annual transshipment of the
four smaller ports amounted to 60 to 70 million tons in 1979. The old harbor
in Gdansk and those in Szczecin and Swinoujscie are natural, situated in the
river mouths; the Gdynia harbor and the North harbor in Gdansk are artificial.
In addition, three small natural harbors are situated in the river mouths on the
middle coast.
The coastal zone has a well-developed shipbuilding industry. There are
several shipyards, including three large ones in the ports of Gdansk, Gdynia,
and Szczecin with an annual productive capacity of about 2% of the world
production. The harbors and shipyards have a developed industrial hinterland,
which also is the location of the electromechanical, electronic, and food
industries. Also located in this area are the Lower Odra power plant, an oil
refinery in Gdansk, a large chemical plant at Police with a new harbor for
handling chemical cargo located on the Odra River, railway junctions, and
numerous architectural monuments (e.g., the Old Town in Gdansk, a priceless
monument of culture).
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Rotm'cki and Borowka
Tourism
Almost the entire coastal zone has spectacular landscapes, which are valued
by tourists. It has two national parks, on Violin Island and on the Leba Barrier,
and a coastal landscape park at Hel Spit. The coastal zone boasts a combination
of sandy beaches (3 ha/km of beach), cliffs, forested and partly active dunes,
large coastal lakes behind narrow barriers, and architectural monuments
(Andrzejewski, 1984).
In 1980, 14.5 million tourists visited the Polish coastal zones, which has
138,000 beds for tourists, mostly in small localities of up to 1,000 inhabitants.
There are also accommodations at camping grounds, of which about 50% are up to
500 m from the beach (Andrzejewski, 1984).
Shore Protection
Of the 39 holiday resorts and sandy beaches (Figure 7), 16 are on cliffed
coasts that are eroding 0.4-2.3 m/yr. As a result, a variety of shore protection
structures have been erected on the Polish coast. The most expensive concrete
seawalls protect about 20 km of the shoreline. Wooden and concrete groins are
located along 58 km of the coast, but they often do not really protect the shore
against erosion; they merely slow erosion and in so doing, create a problem
elsewhere. Most of the low unconsolidated dune coast is only protected with
the help of low fences.
In recent years, especially after storms of the 1980s when erosion caused
the shore of the narrow Hel Spit to shrink by 50-80 m at some places and the
water washed over in other places, boulder-and-clay ridges are being built, and
piles of concrete sleepers are being dumped along a 4-km section of the shore.
However, these are destroyed too. In 1989, at two points of Hel Spit, the sand
from the bottom of Puck Bay was pumped onto the seashore to create a 50-m beach
belt 2-3 m in height.
The entrances to all the harbors are protected against storm waves by
jetties, usually running parallel to each other and confining the navigable
channels. There is sand accumulation on the updrift (western) side of the
jetties, and erosion and landward shoreline movement on the downdrift side.
IMPACT OF A FUTURE SEA LEVEL RISE
Accelerated rise in sea level will pose direct and indirect threats to the
low-lying areas. Direct inundation will confront the lowest areas, which will
be below the new sea level. Indirect threats such as flooding will face the
adjoining, slightly higher, areas. The natural, economic, demographic, and
cultural resources of Poland's coastal will be seriously jeopardized.
Impacts of a 0.5-m Sea Level Rise
The areas lying less than 0.5 m above sea level will be inundated by a
number of processes: (1) the narrow, sandy coastal barriers separating the
low-lying areas from the sea could erode, exposing inland areas to the sea; (2)
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river valleys will drown; and (3) groundwater tables will rise. Several other
effects will be evident with a 0.5-m rise in sea level. Other impacts include
cliff erosion and higher lake levels.
Increased Cliff Erosion and Landward Movement of the Beach
With a 0.5-m rise in sea level, the probability of particular levels of the
sea being exceeded during storm surges will increase markedly. Flood levels that
today occur only once in a hundred years will recur every 3.5 to 5 years. Based
on the cliffs that are currently exposed to similar levels of wave attack, we
estimate that most cliffs will erode 2.3 m/yr.
Accelerated Sediment Transport by the Longshore Current
The higher levels attained by storm surges will destroy foredunes and erode
barrier islands and spits. The lowered barriers will then be susceptible to
storm washover, which will lead to inlet breaches and sedimentation on the
backside of barriers. The sedimentation will encroach either upon coastal lakes
or upon the meadows and pastures of peat plains. As a result, the coast will
recede and the barriers will shift landward. Especially threatened are the
narrow barriers of the middle coast separating Lakes Jamno, Bukowo, and Kopan
from the sea and Hel Spit.,
Higher Coastal Lake Levels
Coastal lakes are connected with the sea through canals or rivers. The
coastal barriers along the Polish coast have enclosed depressions and valleys
of the late glacial age, forming coastal lakes and peaty marsh plains.
Theoretically, a sea level rise of 0.5 m should increase the area of these lakes
by 10-30%. This, however, depends on (1) how fast sea level rises, and (2)
whether other geological and biological processes adjust to the rate of the rise.
Over the last few decades, no increase in the area of these lakes has been
observed, despite the accelerated rate of sea level rise. On the contrary,
because of their intensive eutrophication, the lakes tend to be overgrown, and
their area is dwindling. The rise in water level would have to be very rapid
to change this tendency. Hence, a rise in the level of the lakes will probably
enlarge the area of swamps and young peat bogs surrounding the lakes and situated
on valley floors and low-lying plains. The sediment transported by rivers into
the lakes, the shift of coastal barriers southward through overwash and inlet-fan
sedimentation, the rapid growth of vegetation on the lake sides, and biogenic
sedimentation controlled by eutrophication are all likely to transform the
coastal lakes to land, thus gradually destroying a zone of great landscape value.
However, theoretically the whole of the lacustrine-barrier zone could shift
south.
Expanded Depression Areas and Higher Groundwater Levels
A sea level rise of 0.5 m will enlarge the area of depressions from 555
km2 to 1,720 km2, with 63% of the increased area in the Vistula Delta, 23% in the
Szczecin Haff region, 13% on the middle coast, and 1% in the Gdansk-Gdynia-Sopot
agglomeration (mostly in Gdansk). These areas will probably be inundated by the
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groundwater level rise; however, this too depends on the adjustment of natural
processes to (1) the rate of sea level rise and its ingression through the
valleys, and (2) the rate of groundwater level rise. Most probably this sea
level rise will make these areas swampy and will cause the development of peat
bogs and the accumulation of phytogenic layers. Thus swamps and wet grassland
will greatly increase in area. The rise in sea level may even affect areas
situated 1-2 m above sea level today. The range of this process will depend
primarily on (1) the intensity of the inflow of groundwaters from morainic
plateaus onto the low-lying areas, and (2) the initial depth of the groundwater
level.
In polders, primarily in the Vistula Delta (1,135 km), (1) groundwater
will rise more rapidly; (2) the probability of particular areas being flooded
will increase, as will the breaching of dikes due to increased infiltration of
water during high stages; and (3) the dikes already built will be too low for
the new hydrological conditions. The probability that the dikes already built
in the Vistula Delta will be unable to protect polders against water is today
less than 0.1% (i.e., a recurrence interval of 1,000 years). However, dikes can
be disrupted because of their excessive permeability or by an ice jam at the
mouth of a river.
The height of the dikes is 2.2-2.3 m because Polish regulations require
them to be 70 cm higher than the 50-year storm (i.e., annual probability of
0.02), although sea level has risen 10 cm since some of them were built
(Krzesniak, 1976). If the sea rises another 50 cm, then the water level during
the 50-year storm will only be 10-20 cm below the dikes, 50-60 cm too low for
comfort.
Thus, it will probably be necessary to (1) upgrade the capacities of
intermediate pumping stations; (2) rebuild and increase the height of dikes; and
possibly (3) raise polder bottoms. These problems would face polders with a
combined area of 1,500 square kilometers, their surrounding dikes (some 1,300
km long), and 120-200 intermediate pumping stations. It is possible that new
polders will have to be built on waterlogged land that will keep expanding in
area. Given the possibility of a one- meter rise in sea level, the new dikes
should be 3.2-3.3 m above sea level.
Inundation of the Lower Reaches of River Valleys
Several changes will take place in the lower reaches of river valleys,
depending on the ability of a particular river to adjust to the rate of the
anticipated sea level rise.
In the Odra valley, a sea level rise of 0.5 m would increase the frequency
of flooding over an area 3-4 km wide that extends 50 km upstream, due to both
higher storms surge levels and the backwater effect on river surges. Near the
coast, flood levels will generally rise 50 cm; upstream, the rise in flood levels
will be somewhat less but still significant. In some cases, the increased
flooding may be mitigated if global warming reduces ice jams, which currently
are responsible for some floods. Sedimentation from floods will tend to shift
upstream, perhaps increasing the ability of a few undeveloped areas to keep pace
with the rising sea -- at the expense of increased inundation downstream.
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These effects will necessitate rebuilding the facilities currently
protecting the polders, such as dikes and possibly also intermediate pumping
stations. In the lower Odra valley, harbor facilities and low-lying industrial
plants in Szczecin and in Police will be threatened. Similar threats will emerge
in the lower Vistula valley and the valleys of the lesser rivers (the Rega,
Wieprza, Parseta, and Slupia), at the mouths of which are located harbors,
industrial buildings, and parts of residential buildings.
Increased Estuarine Salinity
The lakes will grow more saline as a result of more frequent inflows of
Baltic waters into them through river mouths and overwash breaches of barriers.
Moreover, a rise in sea level will facilitate contact between the Baltic and
Atlantic through the Danish Straits. We may anticipate more frequent and massive
storm inflows of the more saline and oxygenated Atlantic waters into the Baltic,
which will benefit the biological life of this sea.
Increased Groundwater Salinity
Higher sea level will hinder the seaward flow of groundwater and allow the
water table to rise in the coastal zone. Higher groundwater levels will also
increase seawater infiltration. This will be reinforced further by an
accelerated water circulation in polders and an excessive exploitation of fresh
waters on barriers, where the drawing of freshwater from near-surface lenses
may cause a rise in the saline water table.
Summary of the Impacts of a 0.5-m Rise
Because of physiographic conditions, the zones of the contemporary landscape
and land use probably could not shift inland. It is imperative to keep the
present agricultural use of the Vistula Delta and the lower Odra Valley,
especially in the polder areas. Giving it up would mean tremendous economic
losses.
All the ports and shipyards as well as a part of the industry and railway
junctions located in the low-lying areas will suffer damage with a future rise
in sea level. The extent of the danger will vary from port to port, depending
on the following factors:
1. The degree of exposure of the ports and their facilities and
infrastructure to waves and storm surges. Thus, the North Harbor in
Gdansk and the fishing harbor in Wladyslawowo, both projecting into the
sea, will be most threatened by exposure, whereas the harbor in
Swinoujscie, situated on the west coast, will be more threatened by
higher storm surges in this part of the Baltic.
2. The altitude above sea level of wharves, jetties, breakwaters, and other
facilities.
3. The probability of simultaneous impacts of the rising sea level and
floods caused by ice jams at the mouths of the rivers on which some
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harbors are
and Ustka.
Rotm'cki and Borowka
located -- e.g., in Szczecin, Police, Darlowo, Kolobrzeg,
4. An increase in sediment transport by longshore currents. This, in turn,
will cause a more intensive alluviation of the entrances to the harbors
in Swinoujscie, Ustka, Darlowo, Kolobrzeg and Wladyslawowo, as well as
of the fairways leading to the harbors -- e.g., the 30-km long fairway
in the Pomeranian Gulf leading to the harbors in Swinoujscie and
Szczecin.
5. The kind, height, strength, and technical condition of the storm
protection structures in the harbors. They are built to accommodate
the probability of storm surges of various heights. However, the rise
in sea level will increase the probability of storm surges that will be
higher than those currently planned for. As a result, various technical
equipment in the harbors and their storm protection structures may prove
to be too low and too weak. They may stop fulfilling their function and
may suffer more rapid destruction. A general answer to the question of
whether harbor facilities and storm protection structures would suffer
destruction in case of a sea level rise is impossible at this stage of
the analysis of the problem. It requires detailed analyses for each of
the harbors.
Impacts of a 1- to 2-Meter Rise in Sea Level
Such a rise would inundate another 1,200 km2 of land (Figure 8); a much
larger area would experience increased flooding. The processes and phenomena
triggered by the rise of 0.5 m will continue and intensify, but their spatial
range will expand, and the threat they will pose to urban, industrial, and
agricultural areas with a high capital investment level will be greater. The
Figure 8. Location of low-lying areas along the Polish Baltic coast.
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steep slopes along the morainic plateaus would prevent the beach-barrier-lake
zones from shifting inland by more than 1 to 4 km.
Lakes will change shape, unless peat formation and sedimentation
accelerate. Some lakes will unite; and cultivated fields, with the exception
of polders, will practically disappear from the low-lying areas of the coastal
zone. There will be an increase in the area of peat bogs and water-logged
meadows. In the Odra valley, the narrow strip of the floodplain in danger
stretches 80 km south of Szczecin; in the Vistula delta, the endangered area
includes 1,560 km, or 94% of the delta area less than 5 m above sea level.
Rural settlement will have to be moved to altitudes higher than the 2-m
contour lines. Agricultural use of this land will be possible only through the
building of polders in an ever-increasing area. A part of the settlements and
tourist accommodations on the low sandy coast will be destroyed or will have to
move onto newly developed accretionary lands on the inner parts of barriers.
Threatened with direct inundation will be parts of towns located less than 2 m
above sea level and inhabited today by about 360,000 people -- mainly parts of
Gdansk, Szczecin, Swinoujscie, and Elblag. Higher situated areas of towns will
be threatened indirectly by flooding.
CONCLUSIONS
It is difficult to make a complete list of threats to urbanized, harbor,
industrial, and historical areas. We can only draw attention to the main sources
of danger. The danger starts today and will grow with the rise of sea level.
Its main sources are (1) the insufficient height and strength of harbor
protection facilities; (2) the increased filling up of the entrances to harbors
and navigable channel ways; (3) the destructive action of storm surges of a
higher frequency of given stages and ever higher; (4) a rise in groundwater
level posing a threat to (a) the strength of foundations and grounds under
houses, industrial buildings, railway junctions, and communication routes, and
(b) the functioning of the urban underground infrastructure with such
installations as stormwater drains, telecommunications, and power cables; (5)
the appearance of groundwater on the surface of low-lying parts of towns; and
(6) the insufficient height of artificial dikes and the possibility of a flood.
The Central Marine Office is responsible for planning and implementing the
protection of Poland's seashores. The existing plans consider current erosion
rates but would not accommodate an accelerated rise in sea level. Also, they
concern only the shoreline, not the entire coastal zone. Awareness of the
dangers from future rise in sea level is low, both among the public and within
the administrative units. It is highly probable, however, that with the changes
taking place in Poland today, the message of this report will get through to the
new decisionmakers and managers in the state administration.
The processes already started by the rising sea will require town planners,
designers, planning offices, economists, engineers, and decisionmakers to adopt
a totally different approach and philosophy that will accommodate the analysis
of the costs, risks, and effects of sea level rise. They must learn to view the
coastal zone as a dynamic system that undergoes continual adjustment.
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BIBLIOGRAPHY
Andrzejewski, E. 1984. Turystyka (Sum.:Tourism). In: Pobrzexe Baltyku.
Augustowski, B., ed. Wroclaw: Ossolineum.
Cebulak, K. 1976. System wodno-melioracyjny (Sum.:The water and drainage
system). In: Xulawy Wislane. Augustowski, B., ed. Wroclaw: Ossolineum.
Cebulak, K. 1984. Gospodarka polderowa (Sum.: Polder economy). In: Pobrzexe
Baltyku. Augustowski, B., ed. Wroclaw: Ossolineum.
Cieslak, K., and W. Subotowicz, eds. 1986. Stan wiedzy o hydrodynamice i
litdynamice oraz ochronie brzegu morskiego.
Czekanska, M. 1948. Fale burzowe na poludniowym wybrzexu Baltyku (Sum.: Flood
raised by storm on the southern shores of the Baltic Sea), Badania Fizjograficzne
nad Polska Zachodnia 11:58-96.
Dziadziuszko, Z., and T. Jednoral. 1987. Wahania poziomow morza na polskim
wybrzexu Baltyku (Sum.: Variation of sea level at the Polish Baltic coast),
Studia i Materialy Oceanologiczne 52:215-238.
Jednoral, T. 1984. Spietrzenia sztormowe wzdlux polskiego wybrzexa. Slupsk:
Instytut Morski, Archives Reports., Jednoral, T. 1985. Fale wiatrowe Morza
Baltyckiego w swietle badan empirycznych. Slupsk: Instytut Morski, Archives
Reports.
Kwiecien, K. 1987. Warunki klimatyczne (Sum.:Climatic conditions). In:
Baltyk Poludniowy. Augustowski, B., ed. Wroclaw: Ossolineum.
Majewski, A. 1987. Charakterystyka wod (Sum.: Characteristic of the Southern
Baltic waters). In: Baltyk Poludniowy. Augustowski, B., ed. Wroclaw:
Ossolineum.
Majewski, A., Z. Dziadziuszko, and A. Wisniewski 1983. Monografia Powodzi
Sztormowych 1951-1975, Warszawa: Wydawnictwa Komunikacji i Lacznosci.
Matusik, M. 1984. Gospodarka rolna (Sum.: Agricultural economy). In: Pobrzexe
Baltyku. Augustowski, B., ed. Wroclaw: Ossolineum.
Rosa, B. 1984. Rozwoj brzegu i jego odcinki akumulacyjne (Sum.: The development
of the shore and its accumulation sections). In: Pobrzexe Baltyku.
Augustowski, B., ed. Wroclaw: Ossolineum.
Slupsk: Instytut Morski, Archives Reports., Costa, J.R., and V.R. Baker. 1981.
Surficial Geology Building With the Earth. Chichester: John Wiley and Sons.
Subotowicz, W. 1982. Litodynamika brzegow klifowych. Gdansk: Ossolineum.
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APPENDIX: CLIMATE AND HYDRODYNAMICS OF POLAND
Climate
The climate of the Polish coast is characterized by highly variable weather
conditions because the southern Baltic is on the path of very active cyclones.
Moreover, it is an area of a frequent exchange of air masses advancing almost
freely from different directions. The prevailing masses are polar-maritime air
from the west (60.4%). Much less frequently the area comes under the influence
of polar-continental air masses from eastern Europe (15.5%) and arctic air from
the Norwegian Sea (9%). The least frequent are tropical air masses (1.5%)
(Kwiecien, 1987). The mean annual temperature of the Polish coast varies between
7.1°C at Cape Rozewie and 8.0°C in Swinoujscie.Q The coldest months are January
and February, with mean temperatures from -0.6°C in the west to -2.4°C in the
east (see Figure 1). The warmest months are July and August (16.1-17.2°C). The
mean precipitation depends on the degree of exposure of the coastline to
rain-bringing westerly winds. Thus, the highest mean annual rainfall is recorded
on the middle coast between Darlowo and Leba (650-700 mm), while the remaining
areas receive much less rainfall (550-570 mm). The highest mean monthly wind
velocities (5-7 m/sec) are characteristic of the autumn-winter months, whereas
the lowest are recorded from May to August (2.5-3.5 m/sec). The autumn-winter
season contains the greatest number of days with strong winds (29 days: 6-7°C)
and storm winds (18 days: >8°C).
Hydrodynamics
The direction of the longshore current is controlled by prevailing winds,
and sediment in the littoral zone is generally transported from the west to the
east (see Figure 1). It is only between Kolobrzeg and Swinoujscie that westward
sediment transport can sometimes prevail. During storms, rip currents 50-200
m apart appear that are almost perpendicular to the coastline. In the deep-water
zone, about 85% of waves are not higher than 3 m or longer than 7 sec. As much
as 95% of the waves are not higher than 4 m or longer than 8 sec. In the
offshore zone, storm waves attain a height of 1 m above the current mean sea
level, and reach 2 m only in the zone of a steeply sloping coast (Jednoral,
1984).
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ADAPTIVE OPTIONS AND IMPLICATIONS OF
SEA LEVEL RISE IN ENGLAND AND WALES
IAN R. WHITTLE, CHIEF ENGINEER, MICE FIWEM
Flood Defense Manager
National Rivers Authority
London, England
ABSTRACT
On July 10, 1989, the National Rivers Authority was established as the major
flood defense agency for England and Wales, with the regionally based staff
transferred from the regional Water Authorities. One of the Authority's
principal roles is to coordinate and plan flood defense strategies and to
undertake appropriate defense programs.
As an island nation, the United Kingdom has a significantly high percentage
of low-lying land already at risk; rising sea levels will increase that risk.
Coastal land use is a mix of rural, urban, residential, commercial, and
industrial zones. This paper identifies the location of flood-prone areas and
refers to some of the socioeconomic aspects of those unprotected areas.
Reference will be made to the storm of 1953 and the defense systems constructed
subsequently around the coast and along the river networks.
The principles used to develop the design defense level for the Thames
Barrier is also summarized. We review the present policies for flood defense
and the short-term interim approach needed to respond to any additional threat
from sea level rise.
Long-term strategies cannot be developed until predictions from global
circulation models become more reliable. This paper refers to current research
programs to analyze the effectiveness of the present generation of defense
structures and identifies some of the constructional adaptations that would
increase their effectiveness.
Some reference is made to the implications for agricultural lands if the
rainfall patterns deviate from those of the present day. Rising sea levels may
preclude the use of gravity outfalls and low-head pumping stations.
The United Kingdom has an extensive data-gathering network to aid the
monitoring of rainfall, river flows, and river levels in real time. Tidal and
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storm-surge forecasts can be undertaken with a considerable degree of accuracy.
The tidal gauge network can be monitored, again, in real time, to check these
predictions. This paper shows that the United Kingdom's ability to issue
reliable flood warnings to inhabitants in urban and coastal areas is well
advanced.
Finally, this paper comments on the use of benefit/cost analyses to support
policies, as well as the effects of the new European Community Directives for
environmental and wildlife protection as a component of the flood defense
policies.
INTRODUCTION
Legislation
The government departments responsible for flood defense policy are, in
England, the Ministry of Agriculture, Fisheries, and Food, and, in Wales, the
Welsh Office. The 1989 Water Act established the National Rivers Authority.
This act transferred to the new Authority from the former regional water
authorities responsibility for supervising all matters relating to flood defense,
and for undertaking functions set out in the 1976 Land Drainage Act. Among other
things, the new act gave the National Rivers Authority responsibility for
safeguarding the water environment; for improving water quality and resources;
for enhancing the environment, amenities, and recreation facilities; and for
developing, in conjunction with the Ministry of Agriculture, Fisheries, and Food,
strategies for flood defense and flood warning systems. The act also provided
for the establishment of utility companies to deal with water supply, sewer
systems, and sewage treatment. (Scotland and Northern Ireland have separate
legislation, so policies and practices in these two countries are excluded from
this paper.)
The powers to deal with problems of erosion of coastal land not subject to
flooding are exercised by 88 Maritime Councils in England and Wales under the
Coast Protection Act of 1949. As in the case of flood defense, the government
departments that have overall responsibility are the Ministry of Agriculture,
Fisheries, and Food in England and the Welsh Office in Wales. The National
Rivers Authority has no responsibility for this area of activity; thus, no
further reference will be made in this paper.
The National Rivers Authorities exercises its functions through nine regions
in England and one region in Wales (Figure 1). Before the new act's passage,
ten regional water authorities managed all aspects of the water cycle.
As the principal flood defense agency in England and Wales, the National
Rivers Authority not only has powers to construct all types of flood defense
works and land drainage works, both on statutory main rivers and on the coast,
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Whittle
National Rivers Authority
Regional Boundaries
Figure 1. The ten regions of the National Rivers Authority.
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but also has general oversight of 250 Internal Drainage Boards and the county,
district, and metropolitan borough councils.
Within the ten regions, flood defense functions are carried out by Regional
Flood Defense Committees, each under a chairman appointed by the Minister of
Agriculture, Fisheries, and Food. Four of the regional committees have developed
their functions to local flood defense committees. The boundaries of the areas
of regional and local committees are "river catchment based" and have evolved
over a 50-year period as a consequence of the various land drainage acts
preceding today's statutes. These four regions share a total of 18 local
districts.
Funding of Flood Defense Works
Any of the above flood defense agencies undertaking improvement works that
can be regarded as a capital investment may be eligible for funding from the
national government. The level of the grant may range from 15 to 55%, with the
actual rate depending on the type of flood defense agency and, in the case of
the National Rivers Authority, the scale of local district programs and the
ability of the local population to pay for them. Sea defense works or river
works to protect against tidal flooding attract a 20% supplement added to the
above rates.
The balance of the cost of the capital works, together with the costs of
all maintenance works, staff costs, all overhead costs, equipment costs, etc.,
are met out of revenue raised individually within the local districts.
The National Rivers Authority is currently spending some £67m (over 100
million U.S. dollars) per annum on capital works. The majority of this amount
goes toward building or reconstructing flood defenses. This level of investment
is expected to increases, in real terms, over the next decade by as much as 50%.
Through grants, the Ministry of Agriculture, Fisheries, and Food provides
approximately 30% of the cost of the capital works program; this contribution
also will increase. Finally, almost as much is being spent on the maintenance
of existing structures, defenses, and water courses.
SEA LEVEL RISE - PROTECTIVE MEASURES
Historical
Until some 8,000-10,000 years ago, much of Great Britain was covered with
a deep ice sheet. The northern part of England and Wales was covered by thick
ice, while land to the south of this sheet suffered varying intensities of ground
freezing. At this time, the sea level would have been up to 100 meters (330
feet) lower than today, and the present sea bed of the English Channel and
southern North Sea was exposed as dry land. Thus, Great Britain was apparently
part of the European continent (Brunsden, et al., 1989).
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As a consequence of a gradual rise in global temperature, this ice sheet
melted and sea level rose. Over time, the ancient deep river valleys and lakes
gradually silted up and the layers of the superficial deposits became
interspersed with layers of vegetation, resulting in a complex, stratified
arrangement of organic and inorganic materials.
Despite the silting processes, much of this land still lies below present-
day sea level. Some of it is as low as 7 meters below the sea, but the majority
lies between 0 and +5 meters (Figure 2). These areas have a high level of
natural fertility, and, over many centuries, inhabitants have raised embankments
to exclude either seawater or riverwater. These embankments were constructed
at what was the edge of the sea. Gradually, the lower lying land that was
seaward of the defenses was covered and raised by further deposits of marine
sediments. As the resulting salt marsh grew, new defenses were constructed at
the new seaward limit. Each of these successive embankments was constructed to
a much larger cross-section and to a higher level than the earlier ones.
These progressively larger defenses were needed because the sea and river
levels were rising relative to the land and because higher standards of defense
were required to protect the increasingly larger areas of land carrying the ever-
increasing valuable agricultural and horticultural industries.
England and Wales cover an area of approximately 15 million hectares.
Agricultural land is graded using a five-category land classification system.
The Ministry of Agriculture, Fisheries, and Food has conducted some work on
identifying areas at risk, and a paper on this subject was presented at the 1989
Loughborough Conference (Whittle, 1989). About three-quarters of a million
hectares of land lie below +5 meters Ordnance Datum Newlyn (ODN). (Note: ODN,
similar to NGVD in the United States, refers to a fixed elevation that was at
sea level when the datum was established.) Within this lie some 640,000 ha of
land, (8%), Grades 1-3, of which nearly 200,000 hectares are classed as Grade
1 land.
In the early days, these lowlands were frequently inundated and,
consequently, not conducive to occupancy by settlers. So for the most part,
settlements developed along river estuaries, especially where a high-level spit
or area of land was free from frequent inundation. Today, many of these early
settlements alongside rivers have become established as major commercial and
industrial zones supported by the necessary infrastructure and residential areas.
Progressively, demand for developable land has meant extension into zones where
risk of flooding is high. Thus, higher standards of defense have been demanded.
In common with many developed countries, the United Kingdom now has billions of
pounds of real estate investments in rural and urban zones—to say nothing of
the hundreds of thousands of people, protected from sea and tidal flooding, all
of which will require continued protection against a rising sea level.
Post-1953 Tidal Surge
A major tidal surge struck along the east coast of England in 1953. Some
300 people died, thousands of hectares of land were inundated with saltwater,
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Tide Gauge
Land below 5 metres AOD
Land between 5 & 10
metres AOD
The boxed informetion on this mep - supplied by the
Proudmen Oceenographic Laboratory - shows recent trends
in sea level computed from records at eight tide guages
in the national network maintained by M.A.F.F.
Lowestoft
3.35
0.9
+ 1.2
*>.«
Figure 2. Low-lying land in England and Wales.
270
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Whittle
and vast urban areas were demolished or seriously damaged. Many kilometers of
sea defense were breached, demolished, washed away, or overtopped. The surge
caused a tide-lock condition in many rivers, causing them to overflow their banks
and flood low-lying lands.
Since that storm, at that time the worst recorded in living memory, the
catchment boards and their successors (river boards, followed by river
authorities, water authorities, and the National Rivers Authority) have
reconstructed, raised, or constructed most of the 1,000 km of sea defenses and
the many thousands of kilometers of tidal defenses. However, many of those
defenses have reached the end of their useful lives. Earthen embankments may
have a life of only 25 years and are being reconstructed, and some hard sea
defenses, which appear to have led to increased beach erosion, need either
complete reconstruction or, at least, a new and deeper foundation at the front
toe.
The surge of 1953 threatened the center of London (Figure 3). The decision
was taken then to implement a long-standing proposal to protect London: the
Thames Barrier.
The Thames Barrier
The Thames Barrier is unique in concept. It consists of a series of gates
that are rotated upwards out of cills set into the river bed (Figure 4). The
Barrier has been designed to afford a standard of protection against a one-in-
one-thousand year storm surge, including sea level rise expected through the year
2030.
The level of the top of the gate was determined as follows:
1. Tide levels at Southend, the mouth of the estuary, were analyzed to
determine the one-in-one-thousand year return period.
2. The hydrodynamics of the river were analyzed to translate the Southend
data of tide levels to the Barrier site.
3. The trend line of the rise in river levels at a location near the
Barrier site was analyzed to establish the relative rise in water level,
and then extrapolated to the year 2030 (i.e., 50 years following the
completion date of the structure).
4. The Barrier structure and gates are designed to resist a static force
from some 9 meters (29 feet) of water.
The Barrier has been designed to permit water to spill over the top of the
gates. Upstream of the Barrier, the river extends for a tidal length of 40
kilometers (28 miles). If the Barrier is operated sufficiently early in the
tidal cycle, a "reservoir" of this length, and 9 meters deep, has little chance
of being filled on any one extreme event. Furthermore, the gates could be
rotated further to gain another 2 meters (6.5 feet) in height, provided that
271
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North and West Europe
Figure 3.
higher.
What London would have looked like if the flood had been just a bit
minor alterations are made to the cills (Figure 4). Thus, the Barrier is capable
of modification to effectively protect London well into the next century against
the worst case predictions of sea level rise (at least given current storm
severities) (Kelly, 1989). In 1982, the Barrier and associated riverside
defenses from Southend, at the river mouth, to Teddington, at the tidal limit,
were tested when the Barrier, although not quite complete, was closed against
a high-surge tide. The Barrier has been operated against adverse conditions on
four occasions.
Other Structures Along the Thames
Besides the Thames Barrier itself, other rivers and creeks have been given
protection by new barrier structures. Most of these consist of drop-leaf gates
set between towers. Those and other gated structures along the Thames would
probably need structural reanalysis to determine their suitability for
modification.
272
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HWST
LWST
River beg
» DesiOnn«>d level
1953 Hood level
Whittle
Open position
Flood control position
B
HWST
Undershot low position
Maintenance position
HWST—high water, spring tides
LWST—low water, spring tides
Bonier gate in four positions
Figure 4. (A) The Thames Barrier concept and (B) barrier in place on Thames
River.
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North and Vest Europe
Barriers apart, many of the remaining defenses along the Thames consist of
conventional hard defenses of varying design. Some may have adequate foundations
and stability to receive an additional crest to gain extra height. Other
defenses, such as soft earthen embankments with protected front face, may also
be capable of being raised merely by the addition of extra material. Elsewhere,
however, where the foundations and subfoundations consist of soft alluvial soils,
it is unlikely that additional weight can be added to these structures. An
extensive program of geotechnical investigation will be required to find the
optimal solution.
Other Defenses in England
The areas of land in England and Wales at risk are protected by a variety
of defenses. In the main, these defenses have been constructed from soft
materials excavated from adjacent lands, but some occur naturally, such as sand
dunes. Soft, artificial defenses have a short life, and many of those built
since 1953 are now showing signs of stress and are being rebuilt, often by
substituting a concrete or stone structure to meet the higher standards needed
for the future.
Some navigable rivers within the United Kingdom have been supplied with
barrier structures, particularly the river at Hull and the Fosse River at York.
These structures have been designed with significant "air draught" to permit
navigation.
Lowering Beach Levels
The United Kingdom, in common with other parts of the world, is experiencing
a general lowering of beach levels and, frequently, loss of the protective
foreshore and salt marsh in front of the soft defenses. The cause of this
decline is alleged to be inability of the surf zone to move shoreward because
of the presence of some obstructing defense. Accordingly, it has been shown that
foreshores are becoming steeper (Halcrow, 1989), which will aggravate problems
associated with defense management policies.
It can be shown through experimental work that the rate at which the beach
level is being reduced is affected by the type of obstructing defense. A
vertical profile wall creates reflective waves, which aggravate beach scour,
although these damaging effects may be reduced by a "stepped" profile. An
alternative profile to combat the adverse effect of walls is to use an embankment
that permits waves to "run up" the face of the structure and thus dissipate wave
energy.
OPTIONS FOR COMBATING SEA LEVEL RISE
Allowances in Design of Sea Defenses
It has been recognized for many decades that as a result of the retreat of
the ice sheet, northern England is rising and southeastern England is sinking.
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Whittle
This isostatic change has contributed to a relative rise in sea level in southern
England. An overall allowance on the order of 3 millimeters per year has,
therefore, been included in the recent designs for sea defenses.
Most of the defenses along the east coast of England are open to a long
fetch to the Continent and can experience severe wave action. An allowance of
up to 2 meters may be provided. Soft defenses built from marine alluvium and
clay soils suffer from shrinkage in the upper drying zone. An allowance of up
to 1 meter for this effect is added to the design still-water level. Obviously,
concrete walls do not have this component of safety, so crest levels of such
defenses are lower. These allowances, together with any additional allowances
that appear pertinent, are added to the basic still-water level (tide plus
surge). The base still-water level is that for 1953 or any later event that
resulted in a higher level.
It is appropriate to consider the allowances that should be included in
the design of new flood defense works for sea level rise. There is so much
uncertainty about future storm patterns, rainfall changes, and evapotranspiration
changes that any allowance must be regarded as a "first guess." Some have
suggested that an allowance of about 6 millimeters per year, including the
existing isostatic change, could be prudent for short-life structures pending
improved estimates of the consequences of climate change. Design concepts of
structures should ideally permit easy modification to meet longer term needs.
The Ministry of Agriculture, Fisheries, and Food has estimated that the
cost of constructing a defense suitable for currently projected sea level rise
in England and Wales could amount to between 5 and 8 billion pounds (7 and 12
billion U.S. dollars). Within this budget figure is an allowance for new and
replacement pumping stations, new drainage outfall systems, and at least two new
tide-exclusion barriers.
Alternative Solutions
The opportunity for reconstructing soft defenses is diminishing. In many
instances, this may be due to the need to provide increasingly large structures,
the difficulty of obtaining a cheap supply of material from nearshore or inland
sources, or the need to avoid damage caused to the environment by digging "borrow
pits." Similarly, hard defenses are becoming more expensive, costing 3 to
5 million pounds per kilometer. With an appreciation of the damage that the hard
structure can cause to the environment, there is a gradual change in the
engineering attitudes toward seeking equally efficient alternative solutions.
Engineers in Great Britain are gaining experience with schemes that involve
raising beach levels using material dredged from sources in stable, offshore
zones. The specification for this material is usually for a coarser grading than
that already on the beach; thus, longer term stability is anticipated. This
material may be further stabilized and protected by the construction of large
terminal groins built from imported rock.
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North and Vest Europe
The design of these structures Is complex. A core of lighter weight
material is protected by layers of rock of increasing mass. Further, in an
attempt to overcome the adverse effect associated with terminal structures, the
"plan shape" is built to resemble a "fish tail," and it may be curvilinear on
plan; the crest level at the seaward end may be higher than that at the landward
connection to encourage the littoral drift processes (Barber, 1988).
Thus, if the "soft" solutions being constructed to date are shown to be
reasonably stable, we may see an extension of this engineering concept for future
capital schemes. In engineering terms, the choice of this solution is sound,
and it really only represents a reversal of natural trends through the use of
energy-dissipating structures.
A natural feature to which much attention is being paid is the salt marshes
found frequently to the seaward side of defenses. These marshes are often found
at a level of about high spring tide. In addition to their environmental
benefits, they are able to dissipate wave energy and allow only small, depth-
limited waves to reach the defense structure.
Many of these marches are in decline because the seaward edge is being
eroded or the vegetative cover is dying back, thus leaving only mud patches.
Engineering solutions are being sought to reverse these trends so as to preserve
these valuable components of a defense system.
The behavior and performance of marshes outline in other recent papers
(e.g., Titus, 1988) confirms that experienced in the United Kingdom. There is
a need, therefore, for an international approach to optimize the ability of this
natural type of defense to respond to future sea level rise.
RESEARCH
Bodies Commissioning Research
The National Rivers Authority is continuing research previously carried
out by water authorities and will be expanding its program to complement research
already undertaken by the Ministry of Agriculture, Fisheries, and Food. Other
complementary research is commissioned by organizations such as the oil industry,
firms of consulting engineers, or intergovernmental agencies in conjunction with
other government departments using research facilities at the numerous
universities, research laboratories, and specialist consultants.
One area of research of specific interest to the National Rivers Authority
is the work undertaken by the Ministry of Agriculture, Fisheries, and Food on
the collection and analysis of tidal data from its system of tidal gauges around
the coast of the United Kingdom (Figure 5). Data from some of these gauges are
used in connection with the Storm Tide Warning Service (see the following
section). The program of analysis feeds into other worldwide scientific
programs.
276
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Whittle
(8 8)
STORHOWAYrf?
SCRABSTER^-,
vv^ /
VWICK
SULLAPOOL.T
ISLE OF MAN (80) KEYSHAM
VEUXSTOWE (SB)
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ORTUHO BRIGHTON (90)
WEYMOUT1U90)
ST MARY'S
Figure 5. Tide gauges of the national network
installations are underlined).
277
- December 1988 (modernized
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North and West Europe
Another strategic research effort is being directed toward finding ways in
which existing defenses can be modified to improve their effectiveness. The
findings from this program are equally important when considering designs for
new defenses. At present, there is much uncertainty about both the timing and
the extent of sea level rise. Until some of these uncertainties are removed,
it is prudent to build defenses to deal only with known situations but, equally
so, to build in provisions for easy modification when the need arises.
Research Programs
For many years, the Ministry of Agriculture, Fisheries, and Food has been
funding applied research and development programs. The principal areas of marine
research have centered around the interaction of tides, surges, and waves. These
dynamic forces have effects on sediment transport processes which greatly affect
the foreshore, surf zone, and stability of estuaries. Many other aspects of the
program are set out in the annual report (MAFF, 1988).
The former water authorities and now the National Rivers Authority also
undertake complementary research programs. At present, the Authority is
concerned with developmental research into the performance of embankments. The
Authority will also include some research into the use of new materials and
systems to facilitate a rapid response to be made to structures should the need
arise.
STORM TIDE FORECAST SERVICES
East Coast Storm Tide Warning Service
Following the 1953 storm event, the government set up a review committee
to report on the event and to make recommendations. The Waverley Committee
recommended the establishment of a warning service for the east coast. Today,
the service is administered by the Ministry of Agriculture, Fisheries, and Food
and is run from the United Kingdom's Met Office.
Atmospheric and tidal data are fed into a numerical surge model to provide
hourly sea level forecasts up to 36 hours ahead. If it appears that a critical
level could be reached at any of the reference ports (Figure 6), checks are made
about 12 hours before high water, using real-time tidal and wind data. This
critical level, known as Danger Level, is predetermined and related to some
crucial defense within the relevant Division. The Met Office will issue
preliminary warning notices to the relevant police force, the National Rivers
Authority region, the local authorities, the Ministry of Agriculture, Fisheries,
and Food, and other interested parties during this period, and it will issue a
metric confirmation or cancellation of that preliminary warning some 4 hours
before expected high water.
The National Rivers Authority will open up its relevant flood control
center, either upon receiving a warning or whenever it perceives that
meteorological conditions could lead to a storm. The Authority has access not
only to this principal tidal gauge network but also to local gauges, and it will
monitor all of these as part of its flood forecasting procedure.
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EAST COAST
STORM TIDE WARNING SERVICE
POIIC*
loundarMi
Forci
RQ.
National Rivers' Authority
Boundary
Region i
Rtglonal H.O
Rtcdvlng C«ntr*
Coattal Division lounaary
Port with tMt gtug*
wd «rMm tor KM CwMVWMC UnK IHO) FCS ADAS MAFF
Figure 6. The Storm Tide Warning Service and the east coast reference ports,
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North and Vest Europe
Throughout any event, the Authority maintains close liaison with the police
forces and local emergency services and others as needed. The National Rivers
Authority work force and other private and public work forces, including military
personnel, may be called on in an extreme event. The police, as the law and
order enforcement agency, will, in liaison with the National Rivers Authority,
issue any notice to the public. They will coordinate the evacuation of the
public from any threatened zone. Following any event that entailed the issuance
of a warning, there is an intense inquiry both to validate the quality of the
warning and, if necessary, to evaluate the return period of the event.
The performance of the warning service has been progressively improving.
This has been made possible by the new computers that can handle greater inputs
of data; by improvements funded by the Ministry of Agriculture, Fisheries, and
Food to the data-gathering systems at the tidal gauges; and by modifications to
the numerical models. The detailed analysis of the tidal data is undertaken by
the Proudman Oceanographic Laboratory at Bidston, near Liverpool, under contract
to the Ministry of Agriculture, Fisheries, and Food.
The warning service outlined above applies only to the east coast. The
remainder of England and Wales receives only the output from the numerical surge
model on a twice-daily basis. A full warning system depends on refining the
models for the south and west coasts and on having better real-time data from
the eastern Atlantic and Western Approaches to the United Kingdom. Much of these
data are exchanged with similar agencies on the Continent, thus ensuring their
optimum use within international forecasting systems.
SUMMARY
Land in England and Wales lying less than 5 meters above sea level must be
protected from flooding. Some of this land is below the sea level and has to
be pump drained. In the main, this low-lying land is backed by a scarp-face,
with land rising rapidly up to the +10.0 meter contour. Much of the lowest lying
land is used for agricultural production, but the higher ridges have been
developed for urban, commercial, and industrial use.
A rise in sea level will necessitate a review of present defense design
standards. In the absence of a definitive statement on timing or amount of rise,
designers in the National Rivers Authority are contemplating increasing the
defense allowances and are adopting designs that are flexible enough to permit
easy modification. Through close contact with research bodies, the National
Rivers Authority will develop strategies appropriate to the needs to meet
changing circumstances.
It has been suggested that defenses that may have only a short life,
approximately 25-50 years, be designed to incorporate an allowance of not less
than 6 millimeters per year, which includes 3 millimeters per year for the
isostatic movement in southeast England (Figure 7) (Whittle, 1989).
280
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North and West Europe
Options for raising defenses should not be implemented unless they are cost
effective. Decisions, however unpalatable, may have to be taken not to
reconstruct some defenses.. Present-day solutions favor the environment by
artificially raising the beach levels. The evaluation of benefits for coastal
defense includes components for environmental, recreational, and amenity
benefits. It may be appropriate to include within the benefits assessment those
benefits that will accrue to planned future development, so that developers are
prepared to make appropriate contributions.
Research into climate change, global warming, and sea level rise is
essential to develop financially sound defense and land drainage strategies.
The National Rivers Authority is conducting research on the use of newer
materials and new proprietary systems to protect defenses.
ACKNOWLEDGMENT
The author acknowledges the assistance given by colleagues in the National
Rivers Authority and the Ministry of Agriculture, Fisheries, and Food in the
preparation of this paper, and the permission of the Ministry to use material
assembled by the author while employed there as Chief Engineer. The views
expressed are those of the author and do not represent the views of the Ministry
of Agriculture, Fisheries, and Food or of the National Rivers Authority.
BIBLIOGRAPHY
Brunsden, D., E. Gardner, and A. Goudie A. 1989. Landshapes. London: David
and Charles.
Barber, P. 1988. Sea Defense at Jaywick. Report to Anglian Region, National
Rivers Authority.
Hal crow, Sir William and Partners. 1989. Report on Coastal Management for
Anglian Region. London, England: National Rivers Authority.
Kelly, P.M. 1989. Global Warming and the Thames Barrier. London, England:
London Emergency Planning Information Center, University of East Anglia.
MAFF. 1988. Ministry of Agriculture, Fisheries, and Food. River and Coastal
Engineering Report. London, England: MAFF.
Titus, J.G., ed. 1988. Greenhouse Effect, Sea Level Rise, and Coastal Wetlands.
Washington, DC: U.S. Environmental Protection Agency.
Whittle, I.R. 1989. The Greenhouse Effect: London at Risk. Conference of
River and Coastal Engineers. Loughborough, England: Ministry of Agriculture,
Fisheries, and Food.
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POLICY ANALYSES OF SEA LEVEL RISE IN THE
NETHERLANDS
J. G. DE RONDE
Ministry of Transport and Public Works
Rijkswaterstaat, Tidal Waters Division
P.O. Box 20907. 2500 EX Den Haag
The Netherlands
INTRODUCTION
In the Netherlands, politicians are becoming more and more aware of the
potential problems that could be caused by climate change. Rijkswaterstaat, a
part of the Ministry of Public Works and Transport, started some smaller studies
on this topic in 1985 (De Ronde, 1989; De Ronde and De Ruijter, 1986).
THE COASTAL PROTECTION STUDY
In 1989, an extensive policy analysis was completed on the future management
of our sandy coast with regard to present erosion problems and the expected
increase in sea level rise (Rijkswaterstaat, 1989). The analysis was based on
morphological predictions of coastal development (erosion and accretion) for
every kilometer of the 254-km length of our dune coast. The total length of the
Dutch coast without estuaries is 353 km. The predictions were made for the years
2000, 2020, and 2090 for three scenarios:
Scenario A -- present sea level rise of 20 cm per century,
Scenario B -- sea level rise of 60 cm, and
Scenario C -- sea level rise of 60 cm plus an increased wind velocity
of 10%.
Impacts like loss of safety and loss of (dune) area were compared with such
measures as beach nourishment, groins, and dikes. An inventory was made of the
whole coastline with a width of 500 m, and this was entered into a GIS system.
The grid used was 1,000 by 50 m; the 50 m was perpendicular to the coastline.
The predictions of coastal erosion/accretion together with the GIS system could
be visualized, and totals could be made of lost areas. The areas can be
subdivided into different types, such as nature, nature with a high ecological
value, housing, industry, and areas used for drinking water.
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Figure 1 gives an example of the results, showing the predicted total losses
of dune area in hectares up to the year 2090. The lower line depicts the
predicted losses if the present sea level rise of 20 cm per century were to
continue, and the upper line depicts the predicted losses if the expected sea
level rise of 60 cm up to 2090 were to occur. In the case of scenario C, the
lost area in 2090 is expected to be about 5,000 hectares. It can be concluded
from these predictions that, in the case of the sandy coast of the Netherlands,
the expected future sea level rise is worsening the erosion problems, but present
erosion is the main problem.
3000 • -
2000 • •
1000- -
LOST DUNE AREA
1990 2000
2020
2090
YEAR
Figure 1. Predicted loss of dune area up to 2090 in the case of present sea
level rise of 20 cm per century (scenario A) and in the case of the expected sea
level rise of 60 cm for the next 100 years (scenario B).
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De Ronde
It is believed that present sea level rise is only a minor cause of this
present erosion. It is thought that this erosion is partly a late coastal
response to more severe sea level rise in the past and partly due to sediment
moving from the coast into the estuaries.
Concerning dikes, the story is of course different. Here, present problems
consist of just maintenance plus minor adaptations, while in the case of future
sea level rise, the necessary adaptations are much greater.
The length of dune coast where measures like beach nourishment are
necessary, in the case of scenarios A and B, can be found in Figure 2. The
large increase in the beginning is due to the fact that up to 1990, many beaches
already will have been nourished. So in 1990, the length of "unsafe" dunes is
zero. If nothing is done, this length will increase rapidly in the beginning
until the effect of past nourishments will have been diminished after roughly
10 years. At present, about 15 km of beach needs to be kept in place by beach
nourishment. This area will increase to 45, 60, or 80 km (of a total of 254
km) up to 2090 for scenarios A, B, and C. At other parts of the coast, where
safety is not at stake, erosion will still occur.
Future Policies
During the coming year, politicians will have to decide what kind of policy
will be followed in the near future. This study describes and compares four
possible future policies:
RETREAT -- At all places where safety is not a problem, nothing will
done, and these parts of the coastline may retreat. Everywhere where
safety is at stake, the coast will be defended.
• SELECTIVE DEFENSE -- In addition to the actions described above, the
most valuable areas (e.g., dunes with a high ecological value) will also
be defended as well.
. TOTAL DEFENSE -- No retreat at all will be tolerated.
. SEAWARD DEFENSE -- "Weak parts of the coast" will be strengthened.
Examples of the necessary measures for retreat and selective defense are
shown in Figure 3. Here the planned beach nourishments are given over the period
1990-2000 in the case of present sea level rise of 20 cm per century.
The expected costs for the four possible policies over the coming 10 years
are given in Table 1. Especially during the first 10 years, seaward defense is
very expensive. The "cheapest" policy is, of course, retreat. The costs for
scenario B are nearly the same as those for scenario A. For scenario C, the
costs are again a lot higher, due to the 10% increase of the wind, with great
effect on dike height and dune strength. In the long run, however, seaward
defense is only a bit more expensive than the other policies. In the case of
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North and Uest Europe
to- •
70 I-
60- •
SO- -
4Q. -
30- -
20- -
10- -i
UNSAFE DUNE COAST
0.6 m*tw
^ .^ -- —" 0,2 nwur
1990 2000
2020
2090
YEAJ?
Figure 2. Predicted length of unsafe dune coast in the case of present sea level
rise of 20 cm per century (scenario A) and in the case of the expected sea level
rise of 60 cm for the next 100 years (scenario B).
Figure 3. Parts of the coast where beach nourishments are planned during the
period 1990-2000 with policy RETREAT (A) and with policy SELECTIVE DEFENSE (B)
in the case of present sea level rise.
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De Ronde
Table 1. The Expected Costs Over the Coming 10 Years for Four Policies and Three
Scenarios (millions of U.S. dollars per year)
Policy
Retreat
Selective
defense
Total
defense
Seaward
defense
A
20 cm
15
19
25
30
Sea level rise scenario:
B
60 cm
(Pi
17
20
28
33
C
85 cm
us 10% wind)
26
31
43
55
a sea level rise of 20 cm per century, the average costs over 100 years are 16,
18, 21, and 23 million U.S. dollars per year, respectively, for the four
policies.
The Minister of Transport and Public Works recently advised policy makers
to use the policy of total defense.
THE ISOS STUDY
Another policy analysis will be finished at the beginning of 1990. This
so-called Impact of Sea Level Rise on Society (ISOS) study is being conducted
in cooperation with the United Nations Environment Programme and Delft
Hydraulics.
This study focuses on the impacts of and possible responses to sea level
rise. It also examines other effects of climate change, including shifts in
storms, river discharges, precipitation, and evapotranspiration. Storms may
become more severe or more frequent, having great consequences for the design
of coastal structures. River discharges may increase and cause more frequent
flooding during the winter season, or may decrease during summer and cause
shortages of water needed for agriculture or drinking. These impacts and the
possible measures against them will also be studied, but more along the lines
of a sensitivity analysis.
The ISOS study will include the entire Netherlands. Besides the coast,
it will look at 3,000 km of dikes along estuaries, rivers, and lakes. Further,
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it will analyze the impacts of sea level rise on the ecology and water management
of the Netherlands. Table 2 shows some of the scenarios that will be used in
this study.
Of course, looking at only impacts is insufficient when discussing sea
level rise. Equally (or even more) important are the possible measures to be
taken and when they should be taken.
Table 2. Main Scenarios of the ISOS Study -- Changes Between 1990 and 2090
Parameter
Favorable
Scenario
A
Mean
Scenario
B
Unfavorable
Scenario
C
Mean sea level rise + 35 cm
Wind force - 10%
Wind direction - 10°
Mean rise of design
level - 20 cm
Precipitation
Summer + 20%
Winter 0%
Evapotranspiration
Summer +
Winter +
River discharge
0%
0%
+ 60 cm
0%
0°
+ 65 cm
+ 10%
+ 10%
+ 10%
+ 10%
+ 85 cm
+ 10%
+ 10°
+ 150 cm
0%
+ 20%
+ 20%
+ 20%
Summer
Winter
+ 10%
- 10%
0%
+ 0%
- 10%
+ 10%
First of all, impacts with the so-called T0 alternative (no measures taken)
will have to be quantified, starting with the changes in hydraulic conditions;
the effects on morphology; and the consequences for safety, water management,
environmental management, and costs. With this knowledge, alternative measures
and constructions can be designed. Given a certain measure or set of measures,
the impacts on hydraulic conditions, morphology, etc., must be studied. When
this has been done, the different alternatives can be evaluated and compared.
With the ISOS study for the Netherlands, it will be possible to answer
questions such as the following:
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De Ronde
• Depending on the rate of acceleration of sea level rise, what measures
should be taken, and when should we initiate them? (or: How long can we
wait before we have to do something?)
If not only relative sea level rise is changing, but also storm
frequency as well as river discharges, then how important are the
various impacts compared to each other? In other words, should we not
be as worried about these other changes as we are about sea level rise?
For example, in the case of the Dutch coast, a 10% increase in wind
force has about the same influence as a 60-cm rise in sea level.
The results of the first phase of the ISOS study, with an inventory of all
important relations between --on the one hand -- sea level rise, changes of
storm surges, and changes of river discharges, and -- on the other hand -- the
impacts, were published in 1988 (Rijkswaterstaat and Delft Hydraulics, 1988).
The second phase of the study is not yet finished. Here, though, some
preliminary results will be given for dikes only.
The 3,000 km of primary dikes in the Netherlands were divided into about 50
so-called dike-rings, each with its own safety standard and subdivided into
about 150 dike-parts. For each dike-part, cost functions were calculated,
depending on the amount of heightening of the dike, the dike's construction, and
the extension of buildings along and on the dike. The raising of a dike within
a town with many houses in and on the dike is many times more expensive than the
raising of a simple dike in the countryside. On the other hand, the model can
calculate for every dike-part the necessary raising, depending on sea level rise,
changes in storminess, changes in river discharges, and changes in management
(e.g., the management of the Ussel Lake).
In the case of the expected sea level rise of 60 cm for the coming 100
years, total costs for dikes will amount to about $7.5 billion U.S. dollars
(Figure 4). In the case of the unfavorable scenario, where besides the 60-cm
sea level rise an increase of the wind of 10% and an increase of winter river
discharges of 10% were considered, the total costs increase to $14 billion U.S.
dollars.
Within the model, the number of dike heightenings during the coming 100
years and the amount of heightening can be differed. When the dikes are raised
in small steps, the costs will be incurred as late as possible in time, but the
total costs will be greater because of the initial costs that occur at every step
of raising. On the other hand, when they are raised in one or two big steps,
the initial costs will occur only once or twice, but the relatively high costs
of the first raising will occur early in the heightening. These different
strategies can be worked out with the model, and an optimal strategy can be
found.
Given a certain scenario (e.g., 60-cm sea level rise), finding an optimal
strategy will not be difficult. The target in the ISOS study will be to find
an optimal strategy, given all possible scenarios with their chance of
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INTEGRATED COSTS OF DIKE RAISING
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Figure 4. Integrated costs of dike raising for the scenarios. Expected sea
level rise of 60 cm and the unfavorable scenario with 85-cm sea level rise plus
10% wind and 10% river discharge.
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occurrence. This will be much more difficult. On the one hand, one will try
to minimize the chance of being in an unsafe situation (when real changes will
be greater than expected), while on the other hand, extensive measures might be
overdone when changes will be smaller than expected.
BIBLIOGRAPHY
De Ronde, J.G. and W.P.M. De Ruijter, eds. 1986. Zeespiegelrijzing, worstelen
met wassend water. Report GWAO-86.002. The Hague, the Netherlands:
Rijkswaterstaat, Tidal Waters Division (in Dutch).
De Ronde, J.G. 1989. Past and future sea level rise in the Netherlands,
Proceedings of the Workshop on Sea Level Rise and Coastal Processes, Florida,
March 9-11, 1989.
Rijkswaterstaat and Delft Hydraulics. 1988. Impact of Sea Level Rise on
Society: A Case Study for the Netherlands, phase I. The Hague, The Netherlands:
Rijkswaterstaat.
Rijkswaterstaat. 1989. Kustverdediging na 1990, discussienota. (In Dutch, an
English version of this report will appear in 1990.)
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IMPACTS OF AND RESPONSES TO SEA LEVEL RISE IN PORTUGAL
MARIA EUGENIA S. DE ALBERGARIA MOREIRA
Centre de Estudos Geograficos
University of Lisbon
Lisbon, Portugal
ABSTRACT
Because of the physiographic characteristics of the Portuguese coast and its
population distribution, the main potential impacts of sea level rise will occur
in the estuaries and coastal lagoons, on the barrier islands, and along the
active sandstone cliffs. The large estuaries and coastal lagoon systems will
be the most severely affected areas because they are densely populated and are
the sites of extensive economic activity. Approximately 70% to 95% of their
intertidal areas, 0.5 m to 2.0 m in elevation, are reclaimed or used in their
natural capacity. These reclaimed lands are occupied by salines (salt pans) and
aquacultural ponds (40%), agricultural fields (34%, primarily rice) associated
with extensive pasture land (2%), port development (12%), urban and industrial
development (8%), and airports (1%).
Among the impacts already being observed as a result of sea level rise are
damage to several artificial coastal structures, beach erosion, retreat of
sandstone cliffs, salt marsh retreat, and salinization of the reclaimed
agricultural soils. The first two and the last of these impacts require
immediate responses from the responsible central and local government agencies.
Wherever harbors and tourist beaches are affected by erosion, the
institutional reaction has been, and will be in the near future, to rely on
technology to repair or reinforce the existing development.
Regarding the impacts on the agricultural soils (rice fields), the responses
of the agencies to the current situation have been to build freshwater reservoirs
along the freshwater fluvial systems to assist in flushing the fields. Future
responses to the increasing salinity in the soils and in the water table, and
also to the submergence (up to 2 m), will need to be different from current
responses. The initial reaction by central governmental bodies to the soil
salinization probably will be to shift the main crop from rice to more salt-
tolerant plants (e.g., barley or sugarbeets), or more probably to shift the use
of these reclaimed areas from agriculture to some sort of development. At the
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municipal level, agencies will probably rely on technological improvements and
will continue to produce rice.
INTRODUCTION
This paper briefly lays out the climate, hydrology, and coastal
geomorphology of Portugal. It then discusses potential impacts of sea level
rise and summarizes our discussions with officials of Portuguese agencies that
must respond to sea level rise.
Climate and Hydrology
The Portuguese coast is in the subtropics, on the boundary between the
Atlantic temperate climate and the Mediterranean climate (Figure 1). This
geographical position explains the different climate regimes that can be found
along the coast, which contributes to the different local geomorphological
processes.
All of the western coast is exposed to the influence of the Westerlies that
dominate the annual and the seasonal wind regime blowing from the north,
northwest, and west. Strong storm winds blow from the southwest in the winter,
associated with tropical depressions.
Wave heights vary: the annual mean wave height is 2.9 m on the northern
sector (Leixoes), 2.3 m on the central sector from Aveiro to Cabo da Roca, 1.0
m on the southwestern sector, and 1.1-1.4 m on the southern coast of the Algarve
Figure 1. Location of Portugal in the subtropical zone.
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(Figure 2). The greatest wave heights, observed in Sines on the western
Portuguese coast in 1978, were around 16-17 m; they originated from the southwest
during a 100-year storm that destroyed the jetties of the harbor of Sines (Feio,
1980). On the southern coast, the calm seas dominate and the infrequent high
waves very seldom reach 5 m. They occur when the strong Levante wind blows from
the Gulf of Gibraltar, usually in winter but also in spring or in autumn.
On the western coast, calm seas (wave height less than 1 m) are infrequent,
as are extreme storm waves (higher than 6 m, Figure 2). The storm waves do not
occur every year, but they are more frequent in the northern region, occurring
every winter.
As a consequence of the wave regime, a general longshore current is
generated from north to south on the western coast (Ferreira, 1981; Ribeiro et
al., 1987). Deflected and refracted by the capes, the current can reach the
coast from opposite directions, from the west, the west-southwest, and the
southwest. A strong littoral current from the southwest also occurs when the
waves run from the southwest. The morphodynamic effects of both of these
littoral transport directions can be seen on the growth and migration of the
spits and barrier islands along all of the coast.
The tidal regime on the Portuguese coast is semi-diurnal and mesotidal. The
tidal range is around 3.8 m along the western coast, 3.4 m on the southern coast
during the spring tides, and between 0.9 m and 1.2 m during neap tides. In the
estuaries, the tidal range is 60-80 cm higher during spring tides. In time of
the fluvial floods, or even during the high fluvial water flow, these values can
increase a few centimeters. The spring tide level reaches 2 m above mean sea
level on the open coast, if the sea is calm.
THE COASTAL GEOMORPHOLOGIC CHARACTERISTICS
The Portuguese coast (excluding the islands) is around 870 km long and
presents a great variety of geomorphologic features, as shown in Figure 3.
According to the published geomorphologic map (Ferreira, 1981) and measurements
taken from the 1:50,000 national topographic maps, sandy beaches occupy 37.5%
of the total length of the coastline; coastal wetlands, 36.9%; and cliffs, 25.6%
(Figure 3).
Excluding the beaches located near the main estuaries, which are nourished
by the fluvial sediments, the beaches of the western coast are narrow (70 to 150
m) -- even those with dunes. The widest beaches have gentle slopes and are
located along the spits, or on the coastal sectors sheltered from the waves by
prominent capes.
On the southern coast, the beaches are narrow with gentle slopes. On the
western side, there are pocket beaches interconnecting through the karst caves
and galleries cut into the calcareous sandstone of the cliffs. Along the eastern
sector, there are linear beaches extending along a cliff face or in the form of
barrier islands and barrier spits.
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Southwestern Coast
East Southern Coast
West
Southern Coast
Figure 2. Spectra of the annual mean wave directions along the Portuguese coast
(1974-1978). Frequency distribution of the annual mean wave height. Data from
I.N.M.G.
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vo
Figure 3. The coast of Portugal.
(A) The rocky, sourthern Algarve
coast of Portugal.
(B) A combination fishing and tourist
village on the Algarve coast.
(C) A highly-populated tourist beach
in Nazare.
(All photos by Karen Clemens)
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Excluding the beaches located near the main estuaries, which are nourished
by the fluvial sediments, the beaches of the western coast are narrow (70 to 150
m) -- even those with dunes. The widest beaches have gentle slopes and are
located along the spits, or on the coastal sectors sheltered from the waves by
prominent capes.
On the southern coast, the beaches are narrow with gentle slopes. On the
western side, there are pocket beaches interconnecting through the karst caves
and galleries cut into the calcareous sandstone of the cliffs. Along the eastern
sector, there are linear beaches extending along a cliff face or in the form of
barrier islands and barrier spits.
Most of the western Algarve beaches are almost completely submerged during
the high spring tides. This feature and the retreat of the cliffs (Dias, 1988)
are already serious problems to the tourist industry there.
The coastal wetlands include the low tidal platforms, which are sandy or
muddy, and the upper tidal platforms covered by salt marsh vegetation. They have
developed on the sheltered estuarine margins, along the creeks, and around the
lagoons between 1.5 m below sea level and 2 m above sea level (Figure 3). They
represent 70% of the total intertidal area of the Portuguese coast.
Approximately 70-95% of the nation's salt marshes have been reclaimed
(Moreira, 1986). The land is defended from tidal submergence by dikes or
embankments. The remaining marsh is characterized by a flat surface and is
pocked by tidal pans and by a dense network of creeks. The microcliff of the
vegetated salt marsh almost always shows a tendency to retreat, being undercut
by the currents and collapsing afterwards. The resulting silty sediments are
accumulating on the tidal platforms where they are stabilized by the low salt-
marsh vegetation. The platform is sandy and muddy, with layers of broken shells,
and cut by the creeks that are more deeply excavated into the mud than into the
sand.
The tidal platforms developed in the Ria Formosa (Faro) lagoonal system are
sheltered by the barrier islands (Figure 3). They are essentially sandy, with
layers of clay and silt (Granja, 1984), and form islands that are colonized by
a Mediterranean type of salt marsh. The creeks are not very deep, and their
margins evolve mostly by the sliding of the sandy layers that overlay the silt.
Here, as well as in Aveiro and in the Sado, the salt marsh is being covered by
the sand coming from the transgressive dunes (on the spits and barrier islands)
and from the beach ridges, blown by the wind, or carried by overwash events.
The cliffs differ in height, profile, and lithological composition (Figure
3). The highest cliffs (more than 50 m) are cut into hard rock, granite, and
metamorphic rock on the northern coast, compact calcareous formations and schists
on the southwestern coast, and interbanded limestone-mudstone-sandstone in the
central coast, north of Serra de Sintra. They are connected to abrasive rocky
platforms that have a lot of stacks, especially when cut into granite. The
processes of retreat, consisting of large rotational landslides, are evident on
the limestone and the mudstone cliffs.
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Low cliffs, around 10 m, also can be found cut into granite in the north,
and into calcareous formations such as at Cabo Raso on the central portion of
the coast. Low cliffs, 15-20 m high, cut into the Miocene and the Pliocene
sandstones are very frequent on the central and the southwest coast, and the
Algarve coast between Sagres and Quarteira. They are connected to narrow
limestone platforms with abundant stacks and patches of sandy accumulations that
form several pocket beaches. These cliffs retreat by collapsing after being
undercut at the base. Cliff retreat rates of 2 m/year due to human effects and
a sea level rise were measured by Dias (1988).
COASTAL LAND USE
The coastal fringe in Portugal is largely natural. Intertidal areas and
adjacent land within the public maritime domain are administered by the Navy and
by the municipalities. No construction is allowed there, and even the public
infrastructure for sanitary facilities, safety, and leisure is regulated and
needs special authorization. These laws, the tidal range, and the annual storm
waves of 5 m to 7 m discourage permanent human occupation of the very low coastal
fringe. There is a strong contrast between the modest human occupation of the
low coastal fringe and the very high population density of the coastal
municipalities (Figure 4).
Among the coastal natural systems, the dunes and the estuarine and lagoonal
wetlands are the most disturbed systems due to the permanent human occupation.
The dunes are inhabited along most of the coast, except in the natural protected
areas that occupy 25% of the total coastal area. Major tourist settlements
occupy 29% of the secondary dunes, and some are even found on the primary dune
(foredune), as occurs on the northern sandy coast and on the eastern Algarve
coast, including the Ria Formosa barrier islands (Figure 5).
The traditional fishing settlements, located on the beach and in the
foredunes, are now quite scarce (4% of the dune area) because they have been
transformed into tourist villages or modern fishing ports. The most important
traditional fishing settlements that are permanently occupied are found on the
barrier islands of the Algarve and are dispersed on the central coast.
Other artificial structures, such as harbors and military airports, have
been built on the dune fringe (Figure 5). In general, the foredune is occupied
by natural vegetation that is regenerated or planted to minimize the migration
of the sand inland. Forty-two percent of the total coastal dune area is planted
with pines (primarily maritime pine), acacia, and eucalyptus. The coastal dune
areas have high concentrations of tourism, but the highest concentration of
population (Figure 4) is along the estuarine margins and the coastal fringe from
Cascais to Lisbon (the Costa do Sol, the first tourist area of Portugal) (Cavaco,
1983).
The coastal fringe of Alentejo, from Troia (Setubal) to Sagres, shows very
low population densities, and some places are deserted. The sector near Sines
is an exception, due to the industrial complex and harbor of Sines, and also to
the increasing tourist demand on this coast.
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Figure 4. Distribution of the population density in Portugal (1981) by
municipality (Concelho) (E.P.R.U., 1988).
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Figure 5. Principal types of land use on the coastal zone: (1) planted forest
(pinelands); (2) natural coastal shrubland; (3) urban and tourist occupation;
(4) cultivated areas; (5) natural reserves and protected areas; (6) harbors; and
(7) airports.
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The coastal wetlands, which have developed on the intertidal platforms of
the estuaries and lagoons (Figure 3), have been hurt by human activities more
than any other part of the coastal zone. The salt marsh, as a natural system,
occupies only around 10% of its original area, where it is protected as Natural
Reserves or Parks due to its ecological value. More than 90% of the total area
of the salt marshes are reclaimed; of this, 40% is totally or partly transformed
into salt works and fish ponds. Agricultural fields (especially rice fields)
represent 34% of the land use in association with pastures or grazing fields
(2%). Harbors (commercial, fisheries, and leisure) occupy 12%; urban and
industrial areas (8%) and airports (1%) form the remainder of the land use.
The salt works are on the high tidal mudflat, after building dikes that
are more or less 0.5 m to 1 m above the spring high tide water level. Very
often the dikes need to be repaired, and some of them are permanently reinforced
by rock embankments or by wooden bulkheads that try to avoid or to minimize the
erosive effects of the storms or the fluvial floods.
In most of the rice fields, the drainage water is discharged through gates
into the estuarine deep channels during the low tides. In a very few cases is
this drainage water pumped from the rice field drains to be discharged into the
estuary, because the rice fields occupy the surface of the upper mudflat (1-3
m above sea level).
Salinization of the rice field soils occurs in summer owing to the dryness
of the climate (Daveau et al., 1977). This situation happens frequently on the
southern estuaries during the dry years, when the evapotranspiration is very high
and there is insufficient freshwater to inundate the rice fields and to reduce
the salinity of the water table.
The urban and industrial areas, as well as the harbors, represent the
highest investment on the reclaimed areas. The most important towns and harbors
of Portugal are located on the estuarine or on the lagoonal margins, and their
artificial structures, such as harbor platforms, roads, and railways, are 2-4
m above sea level. It is the same with the airports that were built on the upper
mudflat, as the airport of Faro, whose runways have cracked as the underlying
muds settled.
THE IMPACTS OF POTENTIAL SEA LEVEL RISE
Some of the impacts the Portuguese coast could suffer from sea level rise
will affect all of the coast, independent of its morphology. The erosion and
submergence (partial or total) of the former intertidal area will increase, and
the extent of other impacts will depend upon the coastal morphology, the rate
of the sea level rise, the topography, and the resistance of the lithologic
materials against the erosion. Therefore, the impacts in this paper are
presented relative to the coastal morphology, classified as estuaries and coastal
lagoons, beaches, and cliffs.
In the estuaries and coastal lagoons, the consequences of a 2-m rise in sea
level (Figure 6c) will be the great enlargement of the estuarine area,
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penetrating into the fluvial system; the increase of the salinity into the
estuaries and aquifers; the salinization of the soil water table in the fluvial
plains and in the reclaimed lowlands; the submergence of part of the salines,
the fish ponds, and the rice fields; the submergence of the total tidal platform
("slikke") and the low salt marsh; the retreat and disappearance of the salt
marsh area; a great risk of erosion and flooding of the harbors and the low
coastal urban areas; the submergence of the Faro airport; and the increasing risk
of flooding and backup in the urban waste drains.
On the beaches, the main impacts will be the narrowing of the beach by
about 50% and the retreat of the foredune; the disappearance of the pocket
beaches; and new pocket beach formation close to the eroding sandstone cliffs.
The Ria Formosa barrier islands will lose more than 50% of their area. New
inlets will form, and washover will increase.
On the cliffs, the impacts of sea level rise will be the submergence of the
abrasion platforms and the increasing retreat of the sandstone cliffs, of the
limestone cliffs, and even of the hard-rock cliffs (especially in the active
tectonic areas).
From the listed impacts, the more important will be those affecting the
estuaries (low coastal wetlands and estuarine waters) and the lagoons, because
they are both the most vulnerable and the most populated.
In the case of a sea level rise of 1 m (Figure 6B), the greatest economic
impact will be the investment associated with coastal tourism. The most
important tourist beaches of the country will disappear. On the coast of the
Algarve, this problem will be in addition to the retreat of the cliffs, whose
tops are very often highly developed.
For a sea level rise of 0.5 m (Figure 6A), the increased salinity of the
estuarine waters, aquifers, and soils will be economically more important than
the submergence of the lower tidal flats, or the erosive effects on the salt
marsh not offset by accumulation of peat and sediment. Salinization will affect
the freshwater supplies for domestic and industrial uses and the water table of
the agricultural soils, especially in the rice fields. Sea level rise will also
be costly for rice agriculture because of the need to pump drainage water from
the rice fields before discharging it into the creeks.
Because of the reclamation of the salt marshes, this ecosystem will not
migrate on the inland boundaries because they are formed of dikes or very steep
dune slopes. In some places, the dikes are less than 50 cm higher than the
spring high tide water level. Here, the erosive effects will be considerable
because they already are a real problem to the owners of the rice fields.
RESPONSES TO SEA LEVEL RISE
The responsibility for managing the coastal zone rests with several entities
of the central, regional, and local administrative authorities. The most
important decisionmakers are the Navy (central administration) and the
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municipalities (local administration). The Department of the Environment must
be consulted, as well as the other agencies that are related to the spatial
organization of this zone.
Among the several organizations and services that take care of the coastal
zone's protection and management are those that should be involved with the main
problems concerning the impacts of sea level rise on the coastal lowlands. To
some of these agencies, the impacts of sea level rise constitute surprising news,
first because they had never considered it, and second because they thought that
it was not so urgent a problem. To other agencies, the impacts are a real
problem and they have been applying the classic engineering solutions to protect
the coastline. We briefly summarize what officials in various agencies think
about sea level rise.
National Navy
As the coastal fringe is a public domain, the national navy is responsible
for managing the coastal margin that occupies the space between the high spring
tides and a line located 50 m inland.
The Hydrographic Institute is the Navy surveying department with an interest
in coastal dynamics. It produces the cartography of the sea bottom and does the
research for controlling and monitoring all the conditions related to
navigability. The phenomenon of sea level rise is, actually, one of the research
programs partly supported by the Institute. Although the results demonstrate
that sea level is rising between 1.27 mm and 1.54 mm per year (Taborda and Dias,
1989), the consequent impacts have not been viewed as a problem. Naval officials
generally believe that protection structures should be built.
Municipalities
The response of the municipalities where tourism is the main economic source
is to keep the beach as large as possible. They will rely on technology (coastal
engineering structures, nourishment). Some municipal officials suggest that
swimming pools be built at seaside as an insurance in case beaches are lost.
State Secretary of the Environment
The impacts on the natural systems will be controlled by several
organizations connected to the environment: the General Directorate of the
Environment (DGA); the General Directorate of the Quality of the Environment
(DGQA); the General Directorate of Natural Resources (DGRN); the General
Directorate of Hydraulic Resources (DGRH); and the General Directorate of Parks
and Natural Reserves (DGPRN). These organizations, which report to the State
Secretary of the Environment, are responsible for all aspects of environmental
protection at this time. There is no Ministry of the Environment currently, and
thus there is no cabinet-level representation for the environment in Portugal.
To some of these entities, the sea level rise issue was surprising, as was
the evidence that it could have such severe impacts on the natural coastal
systems, as well as on the economic systems. DGQA is developing some research
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Figure 6. Location and relative importance of the impacts of potential sea level rises of (A) 0.5 m; (B) 1
m; (C) 2 m. 1, 2, and 3 - increasing erosion; 4 - submergence; 5 - salinization.
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projects about climate change due to the greenhouse effect and the consequent
warming of the atmosphere.
The discussion of the impacts of sea level rise on the coastal hydraulic
systems will continue in the near future, although these agencies have a very
small capacity of direct intervention. Clearly, they must advise the private
owners and other official entities about the risks of certain investments.
Some impacts that have been controlled are those affecting the natural parks
and reserves (DGPRN), especially on the coastal wetlands (Natural Reserves of
Pancas-Tejo estuary, estuary of Sado, Ria Formosa, and Castro Marin-Guadiana),
because the salt marshes will retreat and disappear as a result of the erosion
and the submergence. A solution that must be considered is to allow marshes to
migrate inland, replacing the existing estuarine brackish marshes, which are
not very extensive because of the reclamation of the low fluvial plain and the
channelization of the river courses.
General Directorate of Harbors
The potential impacts on harbors, and on other structures, of coastal
engineering to protect beaches, such as avoiding the infilling of the estuarine
navigation channels, monitoring the growing of the bars, and dredging, will be
controlled by the General Directorate of Harbors (DGP). This agency controls
the national and regional management of the harbors and other coastal protection
structures, according to the regional and local civil administration (Commissions
of Regional Coordination and Municipalities).
This office is not very concerned about sea level rise because the
consequences will unfold slowly. They need to rebuild the coastal structures
anyway, from time to time, so sea level rise can be incorporated gradually. The
reinforcement of structures whose effective lifetime will be decreased and the
building of new structures are the solutions most commonly suggested.
National Survey for Civil Protection
The National Survey for Civil Protection is part of the Ministry of Defense
and protects the people against natural hazards. It is concerned with the
impacts of a sea level rise of 1 m and 2 m because of the increased flooding
risks in the urban drainage systems and the risk to buildings affected by the
storm waves. They told us that they have no immediate answer to the problem,
but they will consider it.
General Directorate of Agricultural Resources
The General Directorate of Agricultural Resources is responsible for the
study of soils and the coordination of agricultural productivity. It is very
concerned about the problem of salinization of the reclaimed estuarine soils and
the alluvial soils. The subject is being studied, and several solutions and
their economic feasibility are being considered, especially because of the
potential for decreased rice productivity. At the same time, the cost of rice
production will increase because of the cost of energy to pump the water from
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the drainage channels of the rice fields. One of the possible solutions may be
to substitute other crops (oats, barley, or sugarbeets) for rice or to use the
land for purposes other than agriculture.
General Directorate of Tourism
The Directorate of Tourism is one of the organizations connected to coastal
management and planning. It is very concerned with the impacts of sea level
rise on the coast, mostly on the beaches. Together with other agencies, it will
try to find options that can provide practical solutions, such as jetties or
artificial nourishment of the beach. A proposed solution to decrease the tourist
pressure on the coastal fringe will be accepted with very great difficulty.
The impacts of the possible sea level rise will be controlled by several of
these organizations as well as by the owners of the land. Very seldom will such
impacts be responded to by only one agency.
CONCLUSION
One of the few conclusions we are able to draw is that the solutions will
appear gradually as sea level rises. Neither structural solutions nor land use
changes are yet part of the planning process in Portugal. This is hardly
surprising given the recent nature of the issue. Nevertheless, because sea level
rise could have important impacts, the time to start planning is now.
BIBLIOGRAPHY
Cavaco, C. 1983. A Costa do Estoril. Esboco Geografico. Ciencia e Tecnica
6, Lisboa, Ed. Progresso Social e Demografia:261.
Carvalho, J.R.R., and J.P. Barcelo. 1966. Agitacao maritima na Costa Oeste de
Portugal Metropolitano. Lisboa, Laboratorio Nacional de Engenharia Civil, Mem.
290:63.
Daveau, S., et al. 1977. Repartition et rythme des precipitations au Portugal.
Lisboa, Centre de Estudos Geograficos, Mem. 3:184.
Dias, J.M.A. 1988. Aspectos geologicos do Literal Algario. Geonovas, 10:113-
128.
E.P.R.U. 1988. Portugal em Mapas e Numeros. Lisboa, Centre de Estudos
Geograficos, Rel. 28.
Feio, M. 1980. 0 Porto de Sines: prejuizos e reparacoes. Finisterra 15(29):74-
84.
Ferreira, D.B. 1981. Carte Geomorphologique du Portugal. Lisboa, Centro de
Estudos Geograficos, Mem. 6.
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Granja, H.M. 1984. Etude geomorphologique, sedimentologique et geochimique de
la Ria Formosa (Portugal). These de 3, troisiemme cycle, Univ. Bordeaux 1:254.
Institute Hidrografico. 1978, 1988. Tabela de Mares, 1979 and 1989 - I,
Portugal, Lisboa.
Institute Nacional de Meteorologia e Geofisica. 1974-1978. Anuario
Climatologico de Portugal, Lisboa, 1974, 1975, 1976, 1977, and 1978.
Moreira, M.E.S.A. 1986. Man made disturbances of Portuguese salt-marshes.
Thalassas 4(l):43-47.
Moreira, M.E.S.A. 1989. Geomorphology and sedimentation rates of the tidal mud
flats of the Sado estuary. IGU-CCE Annual Regional Symposium Guide Book, Lisboa,
130 p.
Psuty, N.P. 1986. Impact of impending sea-level rise scenarios: the New Jersey
barrier island responses. Bull. New Jersey Academy of Science 31(2):29-36.
Ribeiro, 0., H. Lautensach, and S. Daveau. 1987. Geografia de Portugal I. A
Posicao Geografica e o Territorio. Lisboa: Sada Costa, 334 p.
Service Meteorologico Nacional. 1970. 0 Clima de Portugal. Fascicule XII -
Normais climatologicas do Continente, Acores e Madeira, correspondentes a 1931-
1960, Lisboa.
Taborda, R., and J.M.A. Dias. 1989. Tide-gauge data in deducing sea level rise
and crustal movements rate: the Portuguese case. IGU-CCE Annual Regional
Symposium Guide Book, Lisboa. 130 p.
Titus, J.G. 1986. Greenhouse effect, sea level rise, and coastal zone
management. Coastal Zone Management Journal 14(3):147-171.
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CENTRAL AND SOUTH AMERICA
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POTENTIAL IMPACTS OF SEA LEVEL RISE ON THE COAST
OF BRAZIL
DIETER MUEHE
Departamento de Geografia
Institute de Geociencias
Universidade Federal do Rio de Janeiro
Rio de Janeiro, RJ 21945, Brazil
CLAUDIO F. NEVES
Programa de Engenharia Oceanica, Coppe
Universidade Federal do Rio de Janeiro
Caixa Postal 68508
Rio de Janeiro, RJ 21945, Brazil
EXECUTIVE SUMMARY
The impact of sea level rise on Brazil would be similar to the impacts on
other nations: Wetlands and lowlands would be inundated, beaches would erode,
coastal areas would flood more frequently, and saltwater would encroach inland.
But the question remains: How severe will the effects be, how much will they
cost, and what should we do?
Because Brazilians have only recently begun to ask these questions and
almost no research has been done to answer them, we can not yet provide
quantitative estimates of the impacts. Thus, it has not yet been possible to
demonstrate the significance of the issue to public officials, which will be
necessary before we can confidently recommend policy responses.
What we can offer is the perspective of scientists who are beginning
preliminary assessments which we hope will eventually assist policy makers in
the decision process.
We are persuaded by the point of view that the primary responsibility of
researchers is to gradually develop an understanding of the implications of sea
level rise in one's own country and develop recommendations based on that
research, not on the results of analysis in other countries. Because serious
analysis has not been undertaken, we would rather simply tell the IPCC that this
is so than speculate on the implications of response strategies. We are pleased
that our point of view is reflected in the conference report's section on South
America.
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Central and South America
Simply put, our strategic response to sea level rise at this time is to
understand the problem so that in a couple of years we will have useful
information for policy makers. This will require us to develop a comprehensive
understanding of the coast of Brazil, then estimate inundation, erosion,
flooding, and other effects, then evaluate the costs of alternative responses,
and only then, recommend policies. Accordingly, the bulk of this paper is on
the first step -- understanding the coast.
INTRODUCTION
Brazil is divided into five major geographic regions, according to
geological, climatic, and economic characteristics (Figure 1). Four of these
regions border the Atlantic Ocean (North, Northeast, Southeast, and South) and
the coastline has an approximate length of 7,400 km, without considering the
contour of bays and islands. Extending from latitude 4° north to 34° south, with
climates ranging from tropical to subtropical, within each region the coastline
may be further divided into different segments according to the geomorphological
features or processes.
In Brazil, erosion problems have not been generally considered as caused by
sea level rise, although a few reports (e.g., Muehe, 1989; Tomazelli and
Villwock, 1989) have addressed this issue very recently. Frequently, the idea
that sea level is dropping still persists. In fact, the relative sea level
curves established for several sectors of the Southeast and South regions for
the last 7,000 years (Delibrias and Laborel, 1971; Suguio et al., 1985), indicate
that during two or three occasions, sea level has been up to 5 m higher than at
present.
Despite the continuous drop in relative sea level during the last 2,300
years, evidence of coastal erosion begin to be noticed at different parts of the
coastline. Lack of sediment supply, increase of storm intensity, local tectonic
movements, and human interference may all contribute to this erosion. The
absence of long-term tidal data and also the scarcity of topographic and
cartographic material makes it difficult to follow coastal changes for a longer
time span into the past. Most of the studies about coastline changes have been
limited to typically unstable areas such as tidal inlets and river mouth bars,
and therefore cannot be considered as evidence of erosion due to a marine
transgression. Nevertheless, there is an increasing feeling, among some
researchers, that a rise in sea level may also be responsible for some of the
detected erosion.
In a shorter time scale, though, there might be a trend for a sea level
rise. Pirazolli (1986) presented relative sea level curves for six locations
in Brazil during the period 1950-1970. There was a rise at rates varying between
5 cm/century to 35 cm/century, except for one location near the mouth of the
Amazon River, which showed a trend for decreasing sea level. This subject is
further discussed in the section about tidal information. Although the time span
of observation was too short to derive a definite conclusion, it is strong enough
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Muehe and Neves
CENTRAL-WEST
TROPIC OF CAPRICORN
SOUTH
Figure 1. Geographic regions of Brazil.
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Central and South America
to justify the beginning of comprehensive studies about the subject in Brazil,
as well as special care in obtaining tidal data.
IMPACTS ON THE COASTLINE
The coast of Brazil was divided into five sectors, and for each of them the
geomorphologic characteristics and the population distribution were presented.
It is reasonable to assume that places with higher numbers of inhabitants per
kilometer of coastline would be more susceptible to the impacts from a one-meter
ri$e in sea level. Therefore, it can be derived from maps that the major impacts
would be limited to the neighborhood of about fifteen coastal cities where the
deny ty'is higher than 5,000 inhabitants per kilometer of coastline.
>*"" * .-'
As a guide for evaluating these impacts, five areas are suggested for study
in each of the sectors owing to their geomorphologic and socioeconomic
characteristics. From North to South, these areas are Salinopolis (PA), near
the mouth of the Amazon; Fortaleza (CE); Recife (PE); Rio de Janeiro (.RJ); and
Rio Grande (RS). ( •.
We briefly summarize concerns for four coastal regions: the Nqrth, the
Northeast, the Southeast, and the South. i
The North
The most important impact here would be the rising water levels in tidal
rivers. Flooding of river valleys will confined to a fairly narrow area due the
presence of high ground somewhat inland. Low-lying alluvial areas such as in
the Marajo Island at the river mouth, however, might be inundated. Because the
low-lying areas in northern Brazil are now sparsely populated, major consequences
for the economy can be avoided as long as future development in the regions
occurs takes sea level rise into account.
The Northeast
In this region, low-lying deltaic areas such as the Sao Francisco Delta will
suffer an expansion of the mangroves into and used today for temporary housing
and agriculture. A more serious problem will face coastal cities like Recife,
Aracaju, and part of Maceio, where low-lying areas are flooded when heavy rains
coincide with spring tides (Nou et al., 1983); with-50-cm rise in sea level the
same effect would occur even during neap tides. Drainage problems and flooding
will probably also confront the low-lying areas of the coastal plains of the
Todos of Santos Bay in Bahia. These problems could be particularly severe in
the heavily populated city of Recife, where urbanization has expanded throughout
the floodplain the Capibaribe and Beberibe Rivers, exacerbating flooding and
drainage problems (Figure 2).
The Southeast
The diverse types of coasts in this region (barrier beaches, pocket beaches,
rocky shores, coastal lagoons, bays, estuaries) will respond in different ways
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Muehe and Neves
Figure 2. Retreating bluffs on the coast of Paraiba (northeast region); note
a tree at the edge of the bluff (center).
to a sea level rise. Some areas are already eroding -- even though human
interference is negligible -- suggesting that these areas are already exhibiting
some of the signs of rising sea level.
For example, during the last fifteen years, the mouth of Paraiba do Sul
River has seen extensive beach erosion with a resulting loss of valuable property
(Argento, 1989). On the southern part of the delta, grayish black sandstone has
been exposed, indicating that shores are retreating. Similar processes have been
identified by Muehe (1984, 1989) at the barrier beaches between Cape Frio and
Guanabara Bay, and the back side of the barrier that faces Araruama Lagoon
appears to be eroding.
Another area in the State of Rio de Janeiro that may suffer from a rise in
sea level is the fluvial-marine plain along the estuary of Sao Joao River located
about 200 km south of Paraiba do Sul River. Currently, rice is extensively
cultivated along the valley, using river water for irrigation. Besides the
potential of flooding, sea level rise could threaten the water supply as
saltwater advances farther upstream, a process that has already been observed.
Finally, the flat areas around Guanabara Bay appear to be vulnerable. These
areas currently flood during heavy rains, especially along rivers and drainage
canals. The combined effects of a rise in sea level and siltation of those
canals will aggravate the flooding. Moreover, because the relative sea level
was 5 m higher during the Holocene than today (Amador, 1974), the terrain in
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this area is very flat and hence extensive areas are vulnerable to flooding from
storm surges. Similar problems seem likely to afflict other coastal plains and
river valleys in the region (Figure 3).
The South
Little data have been collected on current shoreline changes. However, in
Santa Catarina peat has emerged near the scarps of coastal barriers, indicating
that shores are retreating. Similarly, peat is present on the foreshore and
along the base of the foredunes along the beaches of Rio Grande do Sul. Erosion
along the margin of Patos Lagoon also appears to be another indication of
relative sea level rise. All of these trends would be exacerbated if sea level
rise accelerated.
OCCUPATION OF THE COASTLINE
A study of the impacts of sea level rise must consider not only the
geomorphological features of the coast, but also the economic impact it would
have on the population. Due to the fact that no detailed assessment of the
entire coastal zone of Brazil has ever been conducted, and also because it is
always assumed that the population is not evenly distributed along the coast,
the authors chose to characterize the human occupation of the coastline (measured
in terms of inhabitants/km of coastline). This parameter is used to identify
areas where potential impacts would be stronger for the following reason: an
Figure 3. Barrier island of Ipanema-Leblon, city of Rio de Janiero. Erosive
processes have been observed on Leblon Beach (top) and waves reach the longshore
avenue during storms.
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Muehe and Neves
area with a higher degree of occupation would most likely have more diversified
activities (e.g., housing, water supply needs, waste disposal, harbors and
marinas, tourism, agriculture), that would ultimately be affected by sea level
rise. The cost for facing the adverse impact would probably be divided among
all local residents in the form of increased taxes, reduced revenues or
reallocated funds, even though the population might not be at risk of flooding
(which is the first thought of impact).
Micro-regions, established by the Institute Brasileiro de Geografia e
Estatistica (IBGE), as a group of counties with homogeneous geographical
characteristics, were chosen as the basic unit of the coastline. Then, for each
micro-region located on the coast, only those counties that have a coastline were
considered in this study, measuring the length of its coast and its population
(based on 1980 census). The towns would be located at most 30 km from the coast.
First, a comparison was made between the population living in those coastal
counties and the population of the state (figures are presented in Table 1).
For the country as a whole, about 20.4% of the population might be potentially
affected by the consequences of sea level rise (not necessarily flooding). In
the north region, both states, Amapa (AP) and Para (PA), show a high
concentration of population near the coast, respectively 82.9% and 50.7%, even
though their total population is not significant compared to other states. This
is because they are both located in the Amazon region, and their capitals are
are located on the margins of the Amazon delta. In the northeast region,
Pernambuco (PE) has the highest percentage (38.5%) which is explained by the dry
weather in the interior and by its historical development since the 1600s as an
important area of sugarcane plantations. In the southeast region, Rio de Janeiro
(RJ) shows a percentage of 68.6%, which is a high figure. The reason is because
the capital, the City of Rio de Janeiro, and its metropolitan region are located
around two bays and represent the second largest urban center in the country.
Finally, in the south region, Rio Grande do Sul (RS) is the state with the
highest percentage of population (28.7%) in the coastal zone, mostly concentrated
around Patos Lagoon, which has an area of 10,000 km2 and whose coastline will be
affected by sea level rise.
A second study was conducted in order to quantify the population density per
unit length of coastline. Four classes were identified: those where the density
was less than 1,000 hab/km, which characterizes remote areas; those where the
density was between 1,000 and 5,000 hab/km, characteristic of most urbanized
areas, where the economical activities should be more important; those with a
density between 5,000 and 10,000 hab/km, typical of medium size cities, usually
around state capitals; and, finally, above 10,000 hab/km, typical of large
cities.
It was observed that 47.4% of the coastline has very low occupation (a
weighted average value of 522 hab/km). These localities include preservation
areas, small towns without appropriate surveying, or areas where data about
coastline evolution would not be available at all. Consequently, it is difficult
to make an assessment of impacts of sea level variations. On the other hand,
it also suggests that a planned occupation -- which should take into account
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Table 1. Population Living in the Coastal Zone (1980 Census)
Region State
1 AP
PA
2 MA
PI
CE
RN
PB
PE
AL
SE
BA
3 ES
RJ
SP
4 PR
SC
RS
Brazil
Population
In the state On
175,257
3,403,391 1
3,996,404 1
2,139,021
5,288,253 1
1,898,172
2,770,176
6,141,993 2
1,982,591
1,140,121
9,454,346 2
2,023,340
11,291,520 7
25,040,712
7,629,392
3,627,933
7,773,837 2
119,001,427 24
the Coast
145,313
,726,131
,024,148
127,798
,869,026
634,906
400,831
,367,686
644,720
435,985
,622,432
845,546
,748,200
826,490
101,804
877,168
,234,681
,232,034
Percentage
(%)
82.9
50.7
25.6
6.0
35.3
33.4
14.5
38.5
32.5
38.2
27.7
41.8
68.6
3.3
1.3
24.2
28.7
20.4
NOTE: Region -- 1 = North; 2 = Northeast; 3 = Southeast; 4 = South.
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Muehe and Neves
data about sea level trends in neighboring areas -- would be the "best
response"to avoid future problems.
In other areas, which amount to fifteen cities and 12.7% of the coastline,
the population has already been established. Usual coastal engineering works
for shore protection would be feasible there and detailed studies (for past
evolution and future observations) are economically justifiable.
TIDAL INFORMATION
Tide data in Brazil has usually been obtained by the port authorities and
by the Navy for navigation purposes. For various reasons -- like cost of
maintenance and repair of equipment -- the time series has many gaps; this
prevents a study of long-term variations.
As a rough guide of the tidal variation along the coast of Brazil, Table 2
presents figures obtained from the 1989 Tide Table published by the Diretoria
de Hidrografia e Navegacao (DHN) for different ports along the coast. It is
interesting to observe the decrease in tidal range, from 5.0 m near the Equator
to 0.5 in Rio Grande, at the southern part of the country.
Studies conducted by Pirazolli (1986), including six locations in Brazil
during the period 1950 through 1970, indicated a trend for sea level rise in four
stations (Recife (PE), 27 cm/century; Salvador (BA), 16 cm/century; Canavieiras
(BA), 31 cm/century; and Imbituba (SC), 5.5 cm/century; in Fortaleza (CE), the
sea level has oscillated by an amount of 6.6 cm in fifteen years, showing a trend
for rise at the end of the period of observation; in Belem (PA), there was an
oscillation of 2.2 cm in twenty years, with a trend for decreasing in the last
seven years of observation. This data justified the need for further
investigation. Currently, groups of researchers at the Universidade Federal do
Rio de Janeiro (UFRJ) and at the Institute Oceanografico da Universidade de Sao
Paulo (IOUSP) are studying long-term sea level variations at various points along
the coast. The work, which should be completed by the end of 1990, includes:
retrieval of tide data from graphs to digital format; correction for changes in
datum; verification of errors and gaps; and determination of daily, monthly, and
yearly mean sea level curves.
Brazil already participates in the GLOSS program of the Intergovernmental
Oceanographic Commission (UNESCO), and the DHN of the Brazilian Navy is
responsible for the installation of ten permanent tide gauges in the country,
including three stations at oceanic islands. The IOUSP and the Brazilian Port
Authority holding company (PORTOBRAS) also participate in this effort being
responsible for two stations. Combining the data already available for the past
twenty years with the data to be obtained during the next twenty years will
enable us to have a clear picture of relative sea level changes at the beginning
of next century.
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Table 2. Tidal Range Along the Coast of Brazil
Spring tide
Region8
1
2a
2b
3
4
State
AP
PA
MA
PI
CE
RN
RN
PB
PE
AL
SE
BA
BA
ES
ES
RJ
RJ
SP
SP
PR
SC
SC
RS
Location
Barra Norte
Salinopolis
Itaqui
Luis Correia
Mucuripe
Areia Branca
Natal
Cabedelo
Recife
Maceio
Aracaju
Salvador
Ilheus
Barra do Riacho
Tubarao
Cabo Frio
Rio de Janeiro
Sao Sebastiao
Santos
Paranagua
Itajai
Imbituba
Rio Grande
Tvoe"
E
M
B
M
0
0
E
E
M
E
E
B
0
0
0
0
B
0
E
M
E
0
M
HW°
4.16
5.08
6.28
3.27
2.93
3.50
2.12
2.36
2.33
2.34
2.04
2.52
2.20
1.60
1.50
1.26
1.29
1.19
1.50
1.64
1.13
0.72
0.43
LWd
0.37
0.36
0.44
0.20
0.17
0.24
0.11
0.08
0.10
-0.01
0.06
0.18
0.19
0.08
0.04
0.09
0.12
0.03
0.04
0.07
0.12
0.01
0.05
AH"
3.79
4.72
5.84
3.07
2.76
3.26
2.01
2.28
2.23
2.35
1.98
2.34
2.01
1.52
1.46
1.17
1.17
1.16
1.46
1.57
1.01
0.71
0.38
a Region: 1 = north; 2a == northeast, from Maranhao to Cape Calcanhar; 2b =
northeast, from Cape Calcanhar to Bahia; 3 = southeast; 4 = south
b Type of location of the tidal stations: 0 = open coast; B = inside bay; E =
in estuaries; M = at the mouth of the estuary or bay
0 HW = mean values of high water spring tide (elevation in meters relative to
local datum).
d LW = mean values of low water spring tide (elevation in meters relative to
local datum).
e AH = HW - LW.
Source: Values from 1989 Tide Table.
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INSTITUTIONS INVOLVED IN ENVIRONNENTAL MANAGEMENT
The Constitution of 1988 and the state Constitutions that followed brought
the environmental issues into a legal framework by declaring in one of its
chapters that "all have the right to an environment that is in ecological
balance." It also includes the coastal zone among the areas classified as
"national heritage."
Brazil's National Coastal Zone Management Plan (PNGC) was established in May
1988. The Comissao Interministerial para os Recursos do Mar -- the government
agency for sea resources -- is responsible, through its Secretary for Coastal
Zone Management, for establishing general goals and common policies, and for
giving technical and financial support to state and municipal agencies. However,
each State is responsible for developing its own Coastal Management Plan. Each
plan is supposed to include "macro-zoning" of the coast, the monitoring program,
and a geographical information system. Because the program is new, macro-zoning
is progressing in only six states, including Rio de Janeiro.
The various consequences of sea level rise -- erosion, flooding, and
saltwater intrusion -- are intrinsic to any management plan. However, officials
are not yet convinced that there is a problem. Many researchers still believe
that sea level is falling around the coast of Brazil; and information on current
sea level and even shoreline trends is unavailable for most of the coast.
Regarding the climate changes issue, the Brazilian government took an
important step in October 1989 by enacting a law that creates the Comissao
Interministerial sobre Alteracoes Climaticas -- an internrinisterial committee
for climate changes, which includes the Secretaries of eight federal ministries,
the Secretary of the Comissao Interministerial para os Recursos do Mar, and the
directors of seven institutions related to research on meteorology, space
science, environment, and agro-sciences.
Finally, studies are currently being developed in Congress in order to
establish a national management plan for water resources. Dams for irrigation,
water supply, and hydroelectric power plants can alter the balance of estuaries
downstream; The significance of these impacts may be much greater than currently
anticipated if sea level rise accelerates; and transition to a drier climate
could further amplify the interactions between water resources and coastal
management. Thus, these two programs need to work together to ensure that
solutions to one type of problem (e.g., increased water supply needs to
counteract increasing droughts) do not create other problems downstream (e.g.,
increased saltwater intrusion and loss of sediment in deltas).
The results of the new programs will not be known for many years. Whether
they are going to work depends mostly on the amount of funds and effort that will
be invested in environmental education.
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MANAGEMENT PROGRAMS
The National Coastal Zone Management Plan was established in Brazil
according to the Federal Law No. 7661 on May 16, 1988. It is made up of the
National Policy for the Environment and the National Policy for Sea Resources.
The Comissao Interministerial para os Recursos do Mar -- the government agency
for sea resources -- is responsible, through its Secretary for Coastal Zone
Management, for establishing general goals and common policies, and for giving
technical and financial support to state and municipal agencies. However, each
state is responsible for developing its own Coastal Management Plan. Each plan
should include the macro-zoning of the coast (which is summarized in twelve
thematic maps), the monitoring program, and the Geographical System of
Information. A detailed explanation of PNGC can be found in Frischeisen et al.
(1989) and Azevedo et al. (1989).
The PNGC is still in its infancy: the macro-zoning program is in progress
in only six states (Rio Grande do Sul and Santa Catarina in the south region,
Sao Paulo and Rio de Janeiro in the southeast region, and Bahia and Rio Grande
do Norte in the northeast region) and it is expected to be completed by 1992.
The concerns about a possible sea level rise are intrinsic to any management
plan. However, in practice, it becomes very difficult to consider relative sea
level variations either because tidal data are not available, or because there
is no reference line that can be used to control erosion along unpopulated
stretches of the coast.
Regarding climate changes, the Brazilian government took an important step
by passing Federal Law No. 98352 on October 31, 1989. This law created the
Comissao Interministerial sobre Alteracpes Climaticas -- an interministerial
committee for climate changes. The committee includes the Secretaries of eight
federal ministries, the Secretary of the Comissao Interministerial para os
Recursos do Mar, and the directors of seven institutions related to research on
meteorology, space science, environment, and agro-sciences.
Finally, studies are currently being developed in Congress in order to
establish a national management plan for water resources. The Brazilian
Association for Water Resources (ABRH), an association of engineers and other
professionals who deal with hydraulic engineering and water resources,
contributes to this plan by forwarding several proposals to the Congress
committee. Multiple uses of water resources (irrigation, water supply,
hydroelectric power plants, construction of dams) cause changes in river
discharge, which alter the environment of estuaries downstream. The significance
of these impacts may be much greater than currently anticipated if the climate
becomes drier and sea level rise accelerates. Thus, it is desirable that the
management plans for water resources and for the coastal zone work together to
ensure that solutions to one type of problem (e.g., increased needs for water
supply) does not create other problems downstream (e.g., increased saltwater
intrusion and loss of sediment in deltas).
Perhaps the most difficult part is to establish stations and routines for
collecting data, which is usually a very expensive task. Taking into account
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all regional differences in socioeconomic needs and priorities, as well as those
differences in impacts due to global weather and oceanographic changes, the
establishment of those national committees gives a promising perspective.
The results of all these plans will be felt in the future, though. Whether
they are going to work depends mostly on the amount of funds and effort that will
be invested in environmental education.
ENVIRONMENTAL LEGISLATION FOR THE COASTAL ZONE
The most important step in environmental legislation, with consequences yet
to be perceived, was given by the Brazilian Constitution of 1988 and the State
Constitutions which followed. Environmental issues were brought into a legal
framework by the declaration in one of its chapters that "all have the right to
an environment which is in ecological balance." It also includes the coastal
zone among the areas classified as "national heritage."
Since 1934, the "Code of Water Resources" has been the basic law which
regulates the uses of water resources, the occupation of the margins of rivers
and lakes, and the occupation of the coastal area. It establishes that a strip
of land 33 m wide, inland from a specific high-water line, belongs to the Union.
Together with a resolution of the Brazilian Navy, public access to the shore is
granted.
The National Policy for the Environment (1981) established the creation of
a National Committee for the Environment (CONAMA) including representatives from
federal ministries and civil organizations. CONAMA has since then approved
several resolutions for protection of sensitive areas and for establishment of
ecological stations. The following areas are included among those of permanent
protection (Resolution 004, 1985): barrier islands, spits, and barrier beaches
up to 300 m inland from the highest water line; mangroves; vegetation for fixing
dunes; wetlands and other areas used by migrating birds; and land up to 100 m
around lakes, lagoons, and reservoirs. As a matter of fact, since 1965, the
"Forest Code" had considered mangroves and vegetation on dunes as being of
permanent protection
The legal framework which grants a balanced use of the environment is
essentially established. In addition to the federal laws listed above, each
state has its own regulations and policies. In a scenario of sea level rise and
climate changes, some of these legislations may need to be reviewed in face of
scientific studies. However, the most urgent problem for the country seems to
be how to enforce these laws, in such a vast area, with very limited resources.
Furthermore, without the social and educational development of a large percentage
of the population, it is extremely hard to achieve the goal of living in an
ecologically balanced environment.
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CONCLUSION
We have only begun to assess the implications of sea level rise and the
greenhouse effect. Upon further investigation, we may find that we have been
overlooking impacts that are more important than those described here; and some
of the impacts that now seem serious may prove to be manageable. Any conclusions
thus must be viewed as tentative and illustrative hypotheses necessary to guide
future research.
In our view, the expected global rise in sea level implies that municipal,
state, and federal authorities should take a preventive approach when selecting
sites for urban expansion and location of industries. Due to the high cost of
protecting developed areas from such a rise, this "preventive approach" includes
the following steps:
1. Enforce coastal management programs, as the one currently in progress,
and establish urbanization plans according to those programs;
2. Install long-term tidal gauges in order to furnish, twenty years from
now, reliable data for inferring sea level trends;
3. Establish a methodology for observing (and quantifying) the evolution
of shoreline, mangrove areas, and other coastal features;
4. Maintain a systematic data bank for oceanographic and meteorologic
information according to international standards;
5. Incorporate the results of scientific assessments into coastal
development plans, for example, by requiring construction to be set back
from the shore;
6. Adopt flexible criteria for designing harbors and coastal structures,
which take into account all the information available for the site and,
at least, a "lower expectation" of sea level rise; and
7. Formulate educational programs about environmental (particularly
coastal) protection and global climatic effects, addressed to different
levels of the population.
The costs involved in these cautious measures could bring significant
benefits in the future and could avoid greater socioeconomic impacts.
BIBLIOGRAPHY
Amador, E.S. 1974. Praias fosseis do reconcavo da baia de Guanabara. An. Acad.
Brasil. Cienc. 46(2): 253-262.
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Angulo, R.J. 1989. Variacoes na configuracao da linha de costa no Parana nas
ultimas quatro decadas. II Cong, da Assoc. Bras, de Estudos do Quaternario. Rio
de Janeiro, July 10-16, 1989. (in press).
Argento, M. 1989. The Paraiba do Sul retrogradation and the Atafona
environmental impact. In: Neves, C. and Magoon. O.T. (ed.) Coastline of Brazil.
American Society of Civil Engineers, New York. p. 267-277.
Azevedo, L.H., D.M.W. See, and D.R. Tenenbaum. 1989. Coastal zone planning.
In: Neves, C. and Magoon, O.T. (ed.) Coastline of Brazil. American Society of
Civil Engineers, New York. p. 70-83.
Bandeira Jr., A.N.; S. Petri, and K. Suguio.
Brasileiro S.A., Internal Report, 203 p.
1975. Projecto Rio Doce: Petroleo
Cruz, 0., P.da N. Coutinho, G.M. Duarte, A.M.B. Gomes, and D. Muehe. 1985.
Brazil. In: Bird E.C.F. and M.L. Schwartz (ed.), The World's Coastline. Van
Nostrand Reinhold Co., New York. p. 85-91.
Delibrias, C., and J. Laborel. 1971. R ecent variations of the sea level along
the Brazilian coast. Quaternaria, XIV: 45-49.
Dias, G.T.M. 1981. 0 complexo deltaico do Rio Paraiba do Sul.
Quaternario no Brasil. Publ. Especial. 2:35-74. Rio de Janeiro.
IV simposio
Dias, G.T.M., and M.A. Gorini. 1979. Morfologia e dinamica da evolucao do delta
atual do rio Paraiba do Sul. Anais da V Semana de Geologia, UFRJ. Rio de Janeiro.
Dias, G.T.M., and C.G. Silva. 1984. G eologia de depositos arenosos costeiros
emersos -- exemplos ao longo do literal fluminense. In: Lacerda, L.D. de,
Araujo, D.S.D. de, Cerqueira, R. and Turcq, B. (ed.) Restingas: Origem,
Estrutura, Processes. CEUFF, Niteroi. p. 47-60.
Dominguez, J.M.L. 1989. Ontogeny of a strandplain: Evolving concepts on the
evolution of the Doce river beach-ridge plain (East coast of Brazil).
International Symposium on Global Changes in South America during the Quaternary:
Past -- Present -- Future. Sao Paulo, May 8-12. Special Publication 1:235-240.
Dominguez, J.M.L., L. Maratin, A.C.S.P. Bittencourt, Y. de A. Ferreira, and J.-
M. Flexor. 1982. Sobre a validade da utilizacao do termo delta para designar
planicies costeiras associadas as desembocaduras dos grandes rio brasileiros.
32 Congr. Bras. Geol., 2 (Breves Comunicacoes): 92, Salvador.
Franzinelli, E. 1982. Contribuicao a geologia da costa do Estado do Para (entre
a baia de Curaca e Maiau). In: K. Suguio, M.R.M. de Meis, and M.G. Tessler (ed.)
Atas IV Simposio do Quaternario no Brasil. Rio de Janeiro, July, 27-31. p. 305-
322.
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Frischeisen, E.R., M.S.F. Argento, R. Herz, and R.P. Carneiro. 1989. The
Coastal Management Program in Brazil. In: Neves, C. and Magoon, O.T. (ed.)
Coastline of Brazil. American Society of Civil Engineers, New York. p. 1-9.
Marques, R.C.C. 1987. Geomorfologia e evolucao da regiao costeira do complexo
estuarino lagunar Mundau-Manguaba. M.Sc. thesis, Departamento de Geografia,
Universidade Federal do Rio de Janeiro. Rio de Janeiro. 152 p.
Martin. L., and K. Suguio. 1989. Excursion route along the Brazilian coast
between Santo (State of Sao Paulo) and Campos (North of State of Rio de Janeiro).
International Symposium on Global Changes in South America during the Quaternary.
Sao Paulo, May 8-12, 1989. 136 p.
Martins, L.R., and J.A. Villwock. 1987. Eastern South America Quaternary
coastal and marine geology: A synthesis. In: Quaternary coastal geology of West
Africa and South America. INQUA-ASEQUA Symposium, Dakar, April 1986. p. 28-96.
Muehe, D. 1984. Evidencias de recuo dos cordoes litoraneos em direcao ao
continente no literal do Rio de Janeiro. In: Lacerda, L.D. de, Araugo, D.S.D.
de, Cerqueira, R. and Turcq, B. (ed.) Restingas: Origem, Estrutura, Processes.
CEUFF, Niteroi. p. 75-80.
Muehe, D., and C.H.T. Correa. 1989. The coastline between Rio de Janeiro and
Cabo Frio. In: Neves, C. and Magoon, O.T. (ed.) Coastline of Brazil. American
Society of Civil Engineers, New York. p. 110-123.
Nou, E.A.V., L.M. de M. Bezerra, and M. Dantas. 1983. Geomorfologia. In:
Projeto Radam Brasil. Levantamento de Recursos Naturais V. 30, Folhas SC 24/25,
Aracaju/Recife. Ministerio das Minas e Energia. Rio de Janeiro.
Nunes, T. de A.N., V.L. de S. Ramos, and A.M.S. Dillinger. 1981. Geomorfologia.
In: Projeto Radam Brasil. Levantamento de Recursos Naturais V. 24, Folha SD 24,
Salvador. Ministerio das Minas e Energia. Rio de Janeiro.
Pirazolli, P.A. 1986. Secular trends of relative sea level (RSL) changes
indicated by tide-gauge records. Journal of Coastal Research, SI, 1:1-26.
Prates, M., L.C.S. Gatto, and M.I.P. Costa. 1981. Geomorfologia. In: Projeto
Radam Brasil. Levantamento de Recursos Naturais V. 23, Folhas SB 24/25,
Jaguaribe/Natal. Ministerio das Minas e Energia. Rio de Janeiro.
Prost, M.T., M. Lintier, and B. Barthes. 1988. Evolution cotiere en Guyane
Francaise: La Zone de Sinnamary. 35 Congr. Bras. Geol. and 7 Congr.
Latinoamericano Geol. Abstracts. Belem, Brazil, Nov 6-13, 1988, p. 407.
Silveira, J.D. da 1964. Morfologia do literal. In: Azevedo, A. de. ed. Brasil
a terra e o homem. Sao Paulo, Cia. Editora Nacional. p. 253-305.
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Suguio, K. and L. Martin. 1976. Brazilian coastline Quaternary formations -
The State of Sao Paulo and Bahia littoral zone evolutive schemes. An. Acad.
Bras. Cienc., 48 (Suplemento): 325-334.
Suguio, K., and L. Martin. 1981. Progress in research on Quaternary sea level
changes and coastal evolution in Brazil. Proc. Symp. on Holocene Sea Level
Fluctuations, Magnitude and Causes, 1981, Dept. Geology, USC: 166-181.
Suguio, K., L. Martin, A.C.S.P. Bittencourt, J.M.L. Dominques, J.-M. Flexor, and
A.E.G.de Azevedo. 1985. Flutuacoes do nivel relative do mar durante o
Quaternario Superior ao longo do literal brasileiro e suas implicacoes na
sedimentaca costeira. Rev. Bras. Geoc., 15 (4): 273-286.
Tomazelli, L.J., and A. Villwock. 1989. Brasil: evidencias de uma provavel
tendencia contemporanea de elevacao do nivel relative do mar. II Cong, da Assoc.
Bras, de Estudos do Quaternario. Rio de Janeiro, July 10-16, 1989 (in press).
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APPENDIX: GEONORPHOLOGICAL DESCRIPTION OF THE COAST
General classifications of the main features of the Brazilian coastline have
been presented by Silveira (1964) and by Cruz et al. (1984). Martins and
Villwock (1987) presented a modified version based on the other two
classifications. In the present paper, a similar pattern is followed with a few
modifications.
The Barreiras group, which is mentioned in this classification scheme,
represents tertiary sedimentary accumulations of varied composition and extends
from the North up to the Southeast Region. Its flat-topped, table-like surface
was deeply incised by the drainage system during the Pleistocene climate
fluctuations. At the coast these deposits occur in the form of active or dead
bluffs, several tens of meters high, carved by the action of waves. Lateritic
concretions, found inside the deposits in the zone of the groundwater table
fluctuation, are frequently preserved at the inner shelf, indicating the
amplitude of coastal recession.
The North Region
The North Region extends from Cape Orange in Amapa (AP), at the border
between Brazil and French Guyana, up to the south of the State of Para (PA)
(Figure A-l). The 1,080-km-long coastline is strongly influenced by the sediment
discharge of the Amazon, which is responsible for the enormous enlargement of
the continental shelf. In front of and northward from the river mouth, the 10-
and 50-m isobaths occur, respectively, at distances of about 100 and 150 km from
the coast. The influence of the Amazon sediments could be followed, during the
recent AMASED expedition, up to about 200 km offshore, where a sharp boundary
between turbid and clear ocean water marked the distal influence of the river.
Southward from the river mouth, the distances of the 10- and 50-m isobaths reduce
to respectively 10 to 80 km. Both the north and south segments, the coast is
characterized by a fringe of muddy sediments, deposited in front of a Barreiras-
like hinterland and covered by mangroves. The south segment presents an
irregular coastline, while the northern segment presents a smoother shoreline.
These differences are obviously due to the large amounts of sediments from the
Amazon River transported to the north.
Due to a tidal range of more than 3 m (reaching 10 m at some locations),
erosive processes are strong. The low gradients of the rivers allow a wide
penetration of tides. Problems have not been reported so far, but large
destruction of mangroves at the ocean front occurs at the north sector (Dias,
personal communication). Naturally, without long-term observation it is not
possible to know if this is a general trend or only a cyclic phenomenon, as
related by Prost et al. (1988) for the mangrove coast of French Guyana. For the
south sector Franzinelli (1982) described the presence of active bluffs at
Atalaia beach in Salinopolis, where the sediments of the Barreiras group lie on
top of the calcareous sediments of the Pirabas Formation (Figure A-2). Dead
bluffs, 7 m high, are also found at distances of about 100 m from the shoreline,
in places where the Barreiras group has been eroded by a higher sea level.
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Muehe and Neves
NORTH REGION
MUD DEPOSITS,BARREIRAS GROUP
BARREIRAS GROUP. R1AS,MANGROVES
Figure A-l. Classification of main physiographic features of the Brazilian
coastline: North Region.
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Central and South America
f I a n t i c
c g „
ATALAIA
LEGEN D
E~^-~—•» Mangrove deposits
Tidal flat deposits.
Sand and Silty sand
Barreiras Group
/~N>-'-> Lithologic Contact
Cliffs
Beach ridges
Cities
GEOLOGIC MAP OF PARA STATE COAST
NEAR MARACANA AND SALINO'POLIS
Modified from Fronzinelli, 1982
Figure A-2. Geologic map of part of the ria coast of Para, between Maracana and
Salinopolis. (Frazinelli, 1982; Martins and Villwock, 1987).
330
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Muehe and Neves
For the whole region, a sea level rise will significantly increase the
penetration of the tidal wave into the rivers. Flooding along the river valleys
will be laterally confined by the higher areas of the Tertiary and Pleistocene
sedimentary deposits. Depending on the sediment budget, low-lying alluvial
areas such as in the Marajo Island at the river mouth, will be inundated.
The Northeast Region
The Northeast Region consists of nine states: Maranhao (MA), Piaui (PI),
Ceara (CE), Rio Grande do Norte (RN), Paraiba (PB), Pernambuco (PE), Alagoas
(AL), Sergipe (SE), and Bahia (BA) (Figures A-3 and A-4).
With a length of about 2,480 km, the coast can be divided into two distinct
sections. The first has a coastline 1,540 km long, roughly aligned in the east-
west direction; the climate is dry and consequently extensive dune fields extend
from the State of Maranhao up to Cape Calcanhar. The other section, southward
from Cape Calcanhar up to the State of Bahia in the vicinity of Abrolhos plateau,
has a coastline 1,940 km long, is aligned in the general north-south direction,
and is subject to a humid climate.
The shelf width is narrow when compared to that of the North Region. The
width of the inner shelf, roughly based on the 50-m isobath, decreases from up
to 70 km, in the northern sector of the region, to only 25 km in the south, with
a new enlargement to more than 100 km at the Abrolhos plateau in the southern
extremity of the State of Bahia.
Deposits of the Barreiras group are typical for the whole region, as are the
alignments of beach rocks ("recifes") in front of the shoreline (Silveira, 1964).
The recifes frequently provide an important protection against the action of
waves.
Coastal plains are generally narrow, depending on the distance of the
retreat of the front scarp of the Barreiras group, but increase their extension
by penetration along the lower courses of the river valleys (Nunes et al., 1981;
Prates et al., 1981; Nou et al., 1983). In some places bluffs are still under
the action of waves. In others, the coastal plain enlarges in front of major
rivers and at the deltas of the Parnaiba River (at the border between Maranhao
and Piaui), Sao Francisco River, at the border of the States of Alagoas and
Sergipe, and in front of the Pardo and Jequitinhonha Rivers in the southern
State of Bahia.
A large number of estuaries are found inside or in the proximity of the
Todos os Santos Bay in Bahia.
As in the North Region, very few studies are available about recent coastal
evolution. Marques (1987), in her study about the barrier beach in front of the
Mundau-Manguaba estuarine lagoonal complex in Alagoas, showed a continuous
lateral progradation of the barrier northeast from the tidal inlet during the
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NORTHEAST REGION '. FROM MARANHAO TO CAPE CALCANHAR
BAHKtIHAS
DUNCS .BARREIRAb CROUP
Figure A-3. Classification of main physiographic features of the Brazilian
coastline: Northeast Region from Maranhao to Cape Calcanhar.
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Muehe and Neves
NORTHEAST REGION: FROM CAPE CAIJCANHAR TO BAHU
BARREIRAS GROUP, DUNES.BEACH ROCKS
BARRERASGROJP.DELTASJEACH RDGES
SCALE
Figure A-4. Classification of main physiographic features of the Brazilian
coastline: Northeast Region from Cape Calcanhar to Bahia.
333
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Central and South America
period 1956 to 1984 and a net erosion, during the same period, at the southwest
segment. But these changes may reflect only a local instability of a naturally
unstable coastal segment and not a consequence of a sea level rise (Figure
A-5).
Flooding in most of the coastal area due to sea level rise will be limited
in extension by the scarps of the Barreiras group. Low-lying areas of the
deltas, like the Sao Francisco Delta, may show changes in mangroves (both in area
and in species of trees) and a possible limitation of the areas used for
temporary cultures. A more serious problem will arise in coastal cities like
Recife, Aracaju, and Maceio, where the expansion of urbanization into low-lying
areas actually provokes inundations when heavy rains coincide with spring tides
(Nou et al., 1983); with a 50-100 centimeter rise in sea level the same effect
would occur even during neap tides. Drainage problems and inundations will
probably also affect the low-lying areas of the coastal plains in the confluence
of the Todos os Santos Bay in Bahia. These problems will become critical in the
heavily populated city of Recife, where urbanization has expanded over the valley
floor of the rivers Capibaribe and Beberibe, and where drainage problems and
flcodings very often occur.
Just north of the mouth of these rivers, a long and severe history of
erosion has been recorded in the nearby historical town of Olinda. The causes
of erosion are not completely clear yet. The area suffered subsidence in
geological time. However, several engineering works -- groins, detached
breakwaters, dredging -- that have been built might have accelerated the eroding
process. A rise in sea level will strongly affect this area, and further
problems will arise due to an intensification of erosion.
The Southeast Region
The 1,530-km-long coastline of the Southeast Region consists of the States
of Espirito Santo (ES), Rio de Janeiro (RJ), and Sao Paulo (SP) (Figure A-6).
Like the other regions examined, the table-like Barreiras group is still present,
governing the width of the coastal plains up to the northern part of the State
of Rio de Janeiro. An increase in the width of the coastal plains is due to the
Rio Doce Delta in Espirito Santo State and the Paraiba do Sul Delta in the
northern part of Rio de Janeiro State (Figure A-7). The adequacy of the term
"delta" for both of these depositional features has been questioned by Dominguez
et al. (1982), based on the argument that the progradation in front of the river
mouth is a result of longshore drift of sediments derived from the inner shelf
and not of fluvial sediment accumulation, as assumed by Bandeira et al. (1975)
for the Doce River Delta and by Dias et al. (1979) and Dias (1981) for the
Paraiba Delta. More recently, Dominguez (1989) changed his interpretation about
the Doce river delta or strandplain, attributing a more significant role to the
river as a sediment supplier than in his earlier model.
Southward from the Paraiba Delta, at Cape Frio, the coastline changes from
northeast-southwest to an east-west direction. This stretch ends at Marambaia
Island and is formed by barrier beaches, the only interruption being the rocky
coast near the mouth of Guanabara Bay. The barriers may occur as either single
334
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Muehe and Neves
2 Km
Figure A-5. Shoreline modifications of the barrier beach in front of the Mundau-
Manguaba lagoonal-estuarine complex in Maceio, Alagoas (Marques, 1987).
335
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Central and South America
SOUTHEAST REGION
\-.rv
U ounill', HI ff.n UttXS.
u*,oon:i
HOCK,
MANGROVES
BEACH wnoi ',.MY5,.»MHCI!OVE5
Figure A-6. Classification of main physiographic features of the Brazilian
coastline: Southeast Region.
336
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Muehe and Neves
41'4O'
41*30'
_4T7Cf
41*10'
41*00
(DHolocene marine terraces,(2) Lagoonal deposits, (3) Fluvial
deposits (Intralagoonal delta). (4) Pleistocene marine ter-
races, 15} Barreiras Formation (Tertiary),(6) Crystalline base-
ment (Pre'cambrian). (7) Beach-ridges alignments', (8) Fluvial
paleochannels , (9) Lakes.
Figure A-7. Geologic map of the Paraiba do Sul Delta or coastal plain,
and Suguio, 1989).
(Martin
337
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Central and South America
or double alignment, with a sequence of coastal lagoons at their backside.
Araruama is the largest of these lagoons, with its mouth near the town of Cabo
Frio. The barrier beaches follow the west direction up to the bay of Sepetiba
near the border with the State of Sao Paulo. From this point on, and along the
whole State of Sao Paulo, the coastline returns to its northeast-southwest
direction, with submergence characteristics in its northern part and emergence
characteristics in the south. The transition between the drowned, indented
coast, with its steep crystalline promontories, and few, narrow coastal plains,
like Ubatuba and Caraguatatuba, and the emergence southern sector, with large
plains up to 40 km wide (for instance, the southernmost Cananeia-Iguape plain)
is very gradual. The region of Sao Sebastiao forms approximately the limit
between these zones. The width of the inner shelf also follows the trend with
the isobath of 50 m situated at a distance of 8 km from the coastline in front
of Santos estuary and at 50 km in front of Iguape (Suguio and Martin, 1976).
These authors explained that such phenomenon are due to a continental flexure
where the inflexion axis strikes asymmetrically to the coastline.
The geomorphology of this region presents many diversified features (barrier
beaches, pocket beaches, rocky shores, coastal lagoons, bays, estuaries) that
will respond in different ways to a sea level rise. Some locations already
present signs of erosion, even though human interference has been minimal.
The mouth of Paraiba do Sul River has shown strong instability in the past
fifteen years, with extensive erosion of the adjacent beaches and loss of valued
property (Argento, 1989). On the southern part of the delta, the coastal plain
shows a sequence of ridges; at the beach face, formations of grayish black
sandstone -- humic material cemented with ferruginous oxides -- have been
exposed, indicating a process of erosion or retrogradation. This same process
becomes also evident by the truncated configuration of coastal lagoons on the
back side of transgressive barriers (Dias and Silva, 1984). Similar processes
have been identified by Muehe (1984, 1989) at the barrier beaches between Cape
Frio and Guanabara Bay, besides evidence of erosion along the back side of the
barrier that faces Araruama Lagoon.
Another point in the State of Rio de Janeiro that may suffer from a rise in
sea level is the fluvial-marine plain along the estuary of Sao Joao River,
located about 200 km south of Paraiba do Sul River. At present, there is an
extensive culture of rice along the valley, which uses the water from the river
for irrigation purposes. Besides potential risks of flooding, the rise of sea
level will cause a stronger saline intrusion, which has already been observed.
The flat areas around Guanabara Bay have flooded very often during heavy
rains, especially along rivers and drainage canals. The combined effects of a
rise in sea level and siltation of those canals will enhance the problem of
flooding. On the other hand, because the relative sea level was 5 m higher
during the Holocene than at present, not only were beach sediments deposited
far from the present coastline (Amador, 1974) but the terrain also became very
flat and appropriate for marine flooding of extensive areas. Similar problems
should affect all low-lying areas of coastal plains and river valleys.
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Muehe and Neves
The South Region
This region is formed by the States of Parana (PR), Santa Catarina (SC), and
Rio Grande do Sul (PS) (Figure A-8). The coastline is 1,310 km long. Along its
northern portion, the coastal plains are narrow and less significant, having
pocket beaches separated by rocky headlands. Paranagua Bay is the most important
feature of this segment. Toward the south, the coastal plains gradually become
wider, and important estuaries appear, like Guaratuba Bay (PR), the Itajai River
(SC), and Laguna (SC), although along the coast of Santa Catarina, pocket beaches
are very frequent.
Reaching the State of Rio Grande do Sul, though, the coastal plain widens
considerably, reaching 120 km for an extension of almost 520 km, being the
largest coastal plain in the country. This is where Patos Lagoon is located,
which has an area of 10,000 sq. km and an average depth of 4 m, and is connected
to the ocean through a single inlet at Rio Grande. The mild slope of the coastal
plain extends offshore: the 50-m deep contour is about 30 km away from the
beach, twice as far as in Santa Catarina.
Processes of erosion and accumulation have been reported by Angulo (1989)
for the littoral of Parana, but observations of coastline changes were restricted
to typically unstable areas like mouths of estuaries (a similar comment has been
made already for Maceio, in the Northeast region). In Santa Catarina, the
emergence of peat at the backshore near the scarp of the barrier indicates a
trend of retrogradation. Tomazelli and Villwock (1989) present well-defined
information about the presence of peat on the foreshore and along the base of
foredunes along the beaches in Rio Grande do Sul. Erosion along the margin of
Patos Lagoon is also interpreted by these authors as an indication of relative
sea level rise. Due to the dominant onshore direction of local winds, a dune
field tends to be built with sand removed from the beach. The erosive effects
already observed might be intensified if this dune field is removed.
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Central and South America
Figure A-8. Classification of main physiographic features of the Brazilian
coastline: South Region.
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POTENTIAL IMPACTS OF SEA LEVEL RISE ON THE GUIANA COAST:
GUYANA, SURINAM, AND FRENCH GUIANA
J.R.K. DANIEL
University of Guyana
Georgetown, Guyana
ABSTRACT
The northeastern coastal zone of the South American continent, known as the
Guiana coast, stretches between the estuaries of the Amazon and the Orinoco
Rivers and forms the coastline of Guyana, Surinam, French Guiana, and parts of
Brazil and Venezuela. The coastal strip is of varying width and is below sea
level at high tide in most places. As a result, extensive areas are covered with
swamps, mangrove forests, and tidal and mud flats.
Early colonizers managed to establish plantations by draining the land.
Because agricultural development has taken place in this zone, today over 90%
of the population of Guyana, Surinam, and French Guiana live on the Guiana Coast.
Therefore, most of the urban centers and communication lines are concentrated
on the coastal zone in the three countries.
A rise in sea level would have serious economic and environmental
consequences for the Guiana coast. The coastal stretch that is naturally
protected by cheniers and shell beaches is likely to recede with the rising sea
level. Much of Guyana and Surinam will be inundated, even if the sea level rises
by as little as 30 cm.
Mechanisms are in place in both Guyana and Surinam to construct and maintain
sea defense structures and to take emergency measures in case of breaches. But
long-term plans to counter the consequences of sea level rise are nonexistent
in the three countries. The governments concerned have not taken the possible
threat of sea level rise seriously, and the coastal communities are mostly
unaware of the possible danger.
INTRODUCTION
Along the northeastern coast of South America between the mouths of the
Amazon and the Orinoco Rivers lies a 1,600-km-long, low coast dominated by
swamps, mangrove forests, tidal flats, mud banks, and flat coastal plains. This
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Guiana coast forms the coastline for Guyana, Surinam, French Guiana, and parts
of Venezuela and Brazil.
More than 90% of the population of the Guianas live on the coastal plain.
As a result, most of the urban centers, including the capitals, communication
networks, and industries are concentrated there.
A rapid rise in sea level would inundate low-lying areas, erode the
coastline, increase salinity of the lower courses of the rivers, disrupt coastal
wetlands, and raise the water table. Although the heavy sedimentation that takes
place on the Guiana coast may offset some of the erosion and wetland loss from
a rapid sea level rise, it would do little to mitigate the other problems.
About 50% of the coast of Guyana is protected by sea defense structures, and
provisions exist to take emergency measures in case of major breeches or failure
of the sea defense system. However, the entire coast of Surinam and French
Guiana, and the western portion of the Guyana coast, remain in their natural
state.
PHYSICAL CHARACTERISTICS
The Coastal Plain
The coastal plain forms a distinct geomorphological region in the Guianas.
It occupies only a small percentage of land in each country but is considered
an important economic zone. It can be subdivided into two geomorphological
regions: the young and the old coastal plains (Figure 1). The former does not
rise more than 2.5 m above mean sea level and in places lies 1.5 m below high
tide; the old coastal plain has an average elevation of 3 m rising to 8 m near
its southern border. Both are underlain by clays of different periods.
CLIMATIC CHARACTERISTICS
The Guiana coast has a humid tropical climate with its characteristic high
rainfall and high temperatures. Two distinct wet periods can be recognized in
the rainfall pattern: the first lasts from mid-May to July, and the second from
November to January, with the former having the most rainfall.
Marine Environment
The waves, in accordance with the wind direction, are northeasterly, and
they meet the shoreline at an oblique angle. The coast may be considered as a
low-moderate energy coast. Unlike the Caribbean islands, the Guiana coast is
not subjected to hurricanes and storm waves. Wave energy is considerably reduced
off the coast of Guiana because of the presence of fine sediments, which remain
in suspension in the near coastal area. The tide is semi-diurnal and its effects
are felt far inland along major rivers.
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A. Guyana
B. Surinam
C.French Guiana
SURFACE MATERIALS
Svamp
Cheniers
Esluorine and Riverain deposits
Saline marine cloy sediments
Desalinised marine clay sediments
Pegosse (Peal groning above S.L.) —|
Mottled cloy sediments
OEMERARA
Mottled cloy sediments S
Remnants of old chemers Isondl I
White sandt
Crystalline basement complex
COROPINA
- BERBICE
HOLOCENE
PLEISTOCENE
PLIOCENE-PLEISTOCENE
PRE-CAMBRIAN
_____ Cooital Ptain
Figure 1. Geomorphology of the Guiana coast.
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Sediment Transportation and Deposition
It is estimated that 100 million tons of sediment are transported westward
every year by the ocean currents. A large proportion is kept in suspension by
the changing tidal conditions, waves, and currents.
When the concentration of sediment in the water exceeds a critical level,
it flocculates to form a coherent mass of viscous mud known as sling mud, and
settles to form mudflats on the shoreline and mudshoals in the offshore region
(NEDECO, 1972).
The mudshoals influence the development of the coastline of the Guianas.
The coast that lies directly opposite the mudshoal is protected from wave action
because the viscous nature of the mud damps out the waves. This coast may be
designated as an accretionary coast. A coast that lies directly opposite a
trough (between two mudshoals) is subject to wave erosion and may be designated
as an erosional coast (Augustinus, 1978). It has been shown that the mud shoals
migrate westward at an average rate of 125 m/month and the recurrence interval
of a mudshoal is approximately 30 years (NEDECO, 1972). Thus, at any one point,
the coast is subjected to either accretion or erosion.
Accretionary Coasts
An accretionary coast begins as a tidal flat at the landward end of a shoal
and can extend as far as 0.8 km. As soon as the tidal flat begins to emerge
above the high-water level, mangrove establishes itself and stabilizes the flat.
The mud that emerges above the high-water level is subjected to physical,
chemical, and biological ripening, leading to soil formation favoring other
vegetation types in addition to mangrove.
Sand accretionary coasts are rare, and where they do occur, they are not
as extensive as the clay accretionary coasts. Cheniers are extensively developed
on the Guiana coast. Stretches of beaches entirely composed of shell fragments
occur in several places along the northwestern coast of Guyana.
Erosional Coasts
Erosional coasts lie opposite a trough (between two mudshoals). When the
eastern end of a mudshoal is eroded, the coast directly opposite it increasingly
comes under wave action. Erosion on the shoreline begins at the edge of the mud
flat. As the mud flat is gradually eroded, waves are able to come closer to the
coast. The removal of mud exposes the root system of the mangrove to wave
action, which eventually destroys the vegetation. Since the seedlings of the
mangrove are not adapted to development under continuous inundation they are not
replenished. Once mangrove is destroyed, erosion of the coast proceeds
unhindered.
Vegetation and Fauna
Mangrove vegetation fringes the shoreline of the Guiana coast. Either a
herbaceous swamp or a swamp forest occurs behind the mangrove. The largest
swamp is located between the Pomoroon and Orinoco Rivers.
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Daniel
The wetlands on the Guiana coast have an exotic variety of animals, birds,
insects, and marine life. The northwest coast is one of the breeding grounds
for the scarlet ibis and many other birds. In the nearshore region, several
shrimp species and two species of crabs are common. The northwestern coast is
the annual nesting grounds for at least four types of giant sea turtles
considered to be endangered species: greens, hawksbills, Ridleys, and
leatherbacks. In the numerous canals and drainage ditches, freshwater fish
abound.
Groundwater Resources
The geologic formation of the Guiana Shield favors the occurrence of
groundwater on the coastal plain. More than 90% of the potable water on the
Guyana coast is obtained from two aquifers that occur at two levels. The
groundwater recharge area is the exposed portion of the white sand that underlies
the rolling hills south of the coastal plain.
AGRICULTURAL AND ECONOMIC DEVELOPMENT
Agriculture
The predominant economic activity on the Guiana coast is agriculture,
followed by fishing. The coastal belt has favorable soil and climate for lowland
crops, such as sugarcane and rice. Among the three countries, Guyana has the
most cultivated land (Figure 2). In both Guyana and Surinam, almost all
agricultural activities are confined to the coastal belt. Apart from market
gardening near large cities, agriculture is insignificant in French Guiana.
Agriculture is the major source of employment, economic growth, and foreign
exchange in the Guyanese economy (Table 1). Most of the irrigation and land
development programs are geared to two major crops, sugarcane and rice. Since
fertile agricultural land is located very close to the coast, large sums of funds
are allocated for drainage, irrigation, and sea defense works.
The land use pattern on the coastal belt of Surinam is similar to that of
Guyana, but in Surinam agriculture contributes only 9.1% of the Gross Domestic
Product (GDP).
In French Guiana, the main occupation on the coast is fishing, which
constitutes 59.3% of all exports. Very few food crops are produced in French
Guiana. Being an overseas territory of France, most of its food is imported.
POPULATION DISTRIBUTION
Over 90% of the population of the three countries live on the Guiana coast
(Table 2). The capitals are also located on the coast, as are major towns and
urban centers.
The main communication lines of the three countries are along the coast.
Since most of the rivers on the Guiana Shield flow in a south to north direction,
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A. Guyana
B. Surinam
C. French Guiana
m
m
CULTIVATED LAND
BAUXITE PRODUCING AREA
COMMERCIAL TIMBER PRODUCTION
GOLD PRODUCING AREA
MANGANESE DEPOSIT
GOLD EXPLOITATION
BAUXITE EXPLOITATION
REFORESTATION
LIVESTOCK
NATURE RESERVE
® AIRPORT/AIRSTRIP
• FISHERIES
M TOURISM
. SPACE CENTRE
5. OIL WELL
— ROAD
i | | RAILWAY
-_-_- DISUSED RAILWAY
IILOMETRES 50
Figure 2. Land use of the Guiana coast.
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Table 1. Agricultural Development
Component
Total population
Area (km2)
Agriculture contribution
to GDP(%)
Total cultivated land (ha)
Irrigated land (ha)
Sugarcane (metric tons) 3
Rice (metric tons)
Fish catches
Guyana
756,000
214,969
29.0
242,817
161,818
,520,000
300,000
27,600
Surinam
354,860
163,265
9.1
36,000
20,000
150,000
270,000
3,600
French Guiana
85,700
90,000
N.A.
3,000
N.A.
5,000
7,790
1,400
N.A. = Not available.
ferry service and other forms of river transportation are provided at major river
crossings.
With the exception of the bauxite processing industry in Linden (Guyana)
and Brokopondo (Surinam), all the major industries and factories are located on
the coastal belt, particularly in the capitals and port cities.
EFFECTS OF SEA LEVEL RISE
Methodology
To estimate erosion from 50-, 100-, and 200-cm sea level rise scenarios,
we used the Bruun Rule:
al
S = —
h
where S = approximation of shoreline movement, a = rise in sea level, h = maximum
depth of exchange of material between the nearshore and the offshore, and 1 =
length of the profile of exchange.
On the Guiana coast, the sea bottom profile in the nearshore zone is shaped
by the wave action to a depth of 2 meters (NEDECO, 1972). The orbital motion
of waves is reduced to an almost horizontal to-and-fro movement. Wave velocity
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Table 2. Population of Cities/Towns Located on the Guiana Coast
Distance from
City/Town Population the coast (km)
Georgetown"
New Amsterdam
Rose Hall
Corriverton
Paramaribo (1987)
Nickerie
Cayenne (1988)
St. Laurent
56,095
19,287
3,167
18,617
68,617
8,000
19,688
3,486
0
8
0
0
7.5
11
0
27
"Unless otherwise noted all values are for 1981.
exceeds 0.70 m/sec, a critical velocity that is required to initiate erosion on
the sea bottom (Augustinus, 1978). Therefore for convenience, the maximum depth
of exchange of material between the nearshore and offshore (h) is taken as 2
meters.
The average distance between the 2-meter bathymetry and the shoreline is
about 300 meters, but it varies according to the position of the mudshoals. To
determine the length of the profile of exchange (1), distances between the
2-meter bathymetry and the shoreline were measured at intervals of 20 kilometers
along the coastline on the map (scale 1:1,000,000).
RESULTS
Scenarios
Projected coastline positions for a 50-, 100- and 200-cm rise in sea level
are shown in Figure 3(A-C). The future coastline shown here is highly
generalized because of the small scale (1:1,000,000) of the map. Based on the
EPA study of sea level rise (Titus, 1985), two scenarios, the mid-range high and
mid-range low -- henceforth simply referred to as high and low, respectively -
- were selected. Measurements taken from the map were compiled under the two
scenarios to show the future rate of coastal erosion. They were also compared
with both short-term and long-term historical rates of erosion (Table 3). The
latest available maps were published in 1980. Therefore, 1980 was considered
the baseline.
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oo
10m Depth Contour (Closure Point)
Change in Sea Level
50cm Rise
100cm Rise
200cm Rise
KILOMETRES SO
Figure 3A. Scenarios of sea level rise for Guyana.
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en
o
SURINAM
10m Depth Contour (Closure Point)
Change in Sea Level
50cm Rise
100cm Rise
200cm Rise
KILOMETRES 50
Figure 3B. Scenarios of sea level rise for Surinam.
-------
CO
en
10m Depth Contour (Closure Point)
Change in Sea Level
50cm Rise
100cm Rise
200cm Rise
KILOMETRES 50
Figure 3C. Scenarios of sea level rise for French Guiana.
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Central and South America
Table 3. Projected Recession on the Guiana Coast (Meters of shoreline retreat relative to its
current position)
50 cm
100 cm
200 cm
Total shoreline
retreat (m)
Coasts
Total shoreline
retreat (m)
Total shoreline
retreat (m)
Historical records
Mid-term
historical
record (m/y)
1942-49
Long-term
historical
record (shill)
1942-66
Historical
record (shill)
1830-1980
Wainini-Pomoroon 1200
Pomoroon-
Essequibo Estuary 2500
Essequibo Estuary*
Essequibo-Demerara*
Demerara-Mahaica*
Mahaica-Berbice 1100
Berbice-Corentyne 900
2400
5200
-sea defense-
-sea defense-
-sea defense-
2200
1800
4800
10300
4300
3600
12
5
5
10-20
28
27
10-15
15-25
8-15
6.2
Corentyne-
Coppename
Coppename-
Surinam
Surinam-Maroni
Maroni-Sinnemary
S i nnema ry- Cayenne
Cayenne-Oyapock
350
1200
900
500
400
600
700
2300
1800
1100
900
1200
1400 20
4600 4 15
3600
2200
1750
2400
* We assume no erosion in areas that already have sea defenses.
Since the erosional environment on the coast varies significantly, each
coastal segment between the major rivers is treated separately. A 50-cm scenario
forecast would affect almost the entire coast. Further rise in sea level would
only exacerbate the situation. Therefore, the scenario for a 50-cm rise in sea
level is considered in detail.
50-cm Scenario
For a 50-cm rise in sea level, it is estimated that the wetland loss would
be highest along the northwestern coast of Guyana. Several factors lead to this
conclusion. The tidal range is very low in this area, which implies that
existing wetlands are at low elevations. The area is also very flat and has many
water courses. Above all, the area is subject to subsidence. Despite the high
rate of peat growth and sedimentation, until recently the relative rate of sea
level has been rising in the area (Brinkman and Rons, 1968).
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Being sparsely populated with little or no development or infrastructure,
the effects of sea level rise would be minimal compared to the densely populated
coasts. The wetlands would simply migrate landward, as the coastland is very
low and occupies a large area.
Saltwater intrusion would also disrupt the swamps since they lie at the
same elevation as the mangrove. A rise in the water table would convert most
of the low-lying swamps to brackish, open-water environments.
The estuaries generally have maintained a fairly stable shoreline on the
Guiana coast (NEDECO, 1972). The estuarine areas receive much more sediment than
the coasts. Erosion is balanced by sedimentation on the larger islands in the
estuary (Daniel, 1984). However, the estuarine coasts facing the northeastern
direction would be affected by the increased wave velocity when sea level rises
to 50 cm.
Wetland loss would be greater along the coast where sea defenses exist.
With the erosion of the mangrove and the tidal flats, large waves would be able
to approach the seawall more frequently, thereby increasing the pressure on the
seawall and increasing the incidents of overtopping. Laboratory studies have
indicated that if the sea level rises by as little as 30 cm, overtopping would
increase threefold (NEDECO, 1972). Saltwater intrusion in the rivers and creeks
is also likely to increase with rising sea level.
Western Surinam, particularly the area adjacent to the mouth of the
Corentyne River, has development similar to the eastern coast of Guyana. Rice
cultivation is extensive and, with improvement of drainage and irrigation, is
expanding. Several acres of swamps have been drained and converted to rice
cultivation.
Most of the urban and agricultural development in Surinam is located on a
chain of cheniers that occurs farther inland. The vast swamp that exists between
the cheniers and the coast is undisturbed. Furthermore, several hectares of land
on the coast are preserved as nature reserves. Therefore higher sea levels would
simply cause the wetland to migrate inland.
In French Guiana, a 50-cm rise in sea level implies a very low erosion rate.
This area experienced a slight uplift in the past (Brinkman and Rons, 1968).
A few islands that lie in the offshore area are underlain by resistant
crystalline basement rocks. Since the extent of the lowland is limited by the
rapidly rising land southward, wetland loss would be proportionately higher on
this coast than elsewhere. Initial sea level rise is likely to affect only the
mangrove-fringed coast. Other problems associated with sea level rise, such as
higher water table and increased salinity in the surface and groundwater, can
also be expected, although economic loss is not likely to be significant.
A slightly higher erosion rate is forecast for the coast east of Cayenne,
an area also subject to subsidence (Brinkman and Rons, 1968). If the subsidence
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continues, erosion is likely to be greater. Because of sparse settlements in
the region, very little economic development has taken place.
100-cm Scenario
A 100-cm rise in sea level for a high scenario would occur by the year 2062
according to the EPA estimates, and a low scenario as interpolated from the EPA
estimate would occur by the year 2080. On the northwestern coast of Guyana,
further encroachment of swamps by mangrove vegetation can be expected.
Total land loss would be great (over 5,000 m). Along the eastern part of
the Guyana coast and parts of Surinam coast, land loss would be considerable
(over 2,000 m) and much farmland would be affected.
The area most affected would invariably be the coast that is protected,
unless foreshore erosion is prevented. Mangrove in the foreshore area in front
of the sea defense structures will be completely wiped out by the rising sea
level. Georgetown, a city that is well fortified against sea erosion, is likely
to come under increasing pressure as the sea level rises.
200-cm Scenario
A 200-cm rise in sea level for a high scenario would occur by the year 2095
and for a low scenario in 220 years' time, as interpolated from the EPA
estimates. The effects of a sea level rise of this magnitude are difficult to
determine at this time. On a few unprotected coasts, strips of land up to a
kilometer wide would be permanently inundated, forcing the mangrove to migrate
landward, and swamp vegetation would be drastically changed. The lower courses
of several rivers that flow parallel to the coast would be altered as the land
separating the river channels from the coast is eroded away. Urban development
and roadways previously located on the unprotected sections of the coast would
have been relocated on the old coastal plain.
Major cities and towns protected against sea erosion would have embarked
on a beach fill program, and perhaps a few kilometers of breakwater would have
been built, but the costs of such programs would be prohibitively high.
Increasing problems in sewage disposal, stormwater disposal, rising water table,
and saltwater intrusion in the cities would be enormous. The effects of sea
level rise described previously would be exacerbated. Some coastal settlements
have already experienced some of these effects, although not necessarily due to
rising sea level.
Sedimentation along the coast may partially offset the effects of wetland
loss, but sedimentation occurs unevenly along the coast and is influenced by a
cyclic pattern, resulting in net decrease of land area. The scenarios forecast
in this study do not take into consideration the possible effects of
sedimentation. Calmer sea conditions have caused heavy sedimentation on the
Guiana coast in the past. Furthermore, at the mouth of the Amazon River,
suspended solids increase as much as fivefold during the wet period compared with
the dry period (Gibbs, 1967). Thus, an increase in discharge in the Amazon
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Daniel
system through increased rainfall or increased deforestation and runoff could
supply more sediments.
PAST TRENDS IN RECESSION
Contradictory views have been expressed on the severity of erosion on the
Guiana coast. NEDECO (1972) concluded that there had been a net erosion on the
Guiana coast. On the other hand, the Hydraulics Research Station (MRS) at
Wallingford refuted this claim. In a recent study, Augustinus and Mees (1984)
claimed that the coast of Guiana has been receding.
Based on the positions of cheniers, NEDECO (1972) calculated that the coast
of Guyana was receding at the rate of 20 m/year and the Surinam coast was
receding at the rate of 12 m/year between 1947/48 and 1957, and 8.5 m/year
between the years 1957 and 1966. Augustinus and Mees (1982) also observed that
on the Surinam coast, erosion has diminished and accretion has taken place. On
the whole, recession has averaged 10-30 m/year on the Guiana coast. NEDECO
(1972) observed that with the rise of sea level in the past century, the 10-30
m/year historical rate of erosion has accelerated in recent years. Various rates
of erosion calculated by NEDECO are given in Table 3.
Historical records also show that the shore has advanced along some coasts.
For example, at Pt. Isere (French Guiana) and Totness (Surinam), rapid accretion
has taken place.
Seawalls do not always prevent erosion. Although the coast may appear
visibly stabilized after the construction of a seawall, erosion can continue in
the foreshore area. NEDECO demonstrated that the foreshore area is oversteepened
where sea defense structures exist. Augustinus and Mees (1984) attributed the
receding shoreline in Guyana to the lack of mangrove development.
Seawalls without adequate toe slope protection are particularly prone to
oversteepening of the foreshore and the eventual collapse of the seawall itself.
This happened in Clonbrook near the Mahaica River mouth, where a 152-meter
section of seawall sank more than 0.6 meters after the foundation collapsed into
the sea (Starbroek News, 1989a).
RESPONSES
Guyana
In Guyana, settlement has meant a constant battle against the sea. The
settlers built artificial dams and sluice gates between the naturally occurring
cheniers to form a defense against erosion.
Because of the complexity of the coastal processes and their effect on the
low-lying areas for the past four decades, successive governments in Guyana have
sought the help of international consultants to study the coast. Two such
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Central and South America
consultants, NEDECO and MRS, made in-depth studies of the coastal problems. The
former also studied Surinam's coastal problems. The two consultants perceived
the coastal problems differently and suggested conflicting strategies (Daniel,
1988).
NEDECO's model for the Guiana coast predicted a 30-year cycle of erosion
and accretion with a net land loss of 10-30 meters annually. They observed that
strengthening the seawall at the present site would not help, because the
accelerated erosion in the foreshore region would eventually undermine the sea-
wall. They recommended a seawall of a different design for the priority areas,
such as Georgetown and its environs. The priority areas were determined on the
basis of a cost-benefit analysis. In the low-priority areas, such as rural
areas, a new seawall several meters inland from the present sea defense system
was suggested. This simply means abandoning several acres of valuable
agricultural land fronting the coast.
Based on economic, statistical, and historical data, HRS suggested that
Guyana should be prepared to respond to emergencies rather than build a strong
sea defense system and supported the present policy of strengthening the sea
defense as and when necessary.
Comparing the two reports, it is clear that NEDECO'S suggestions are valid
in light of the accelerated sea level rise. HRS's report is based on more
conservative estimates and does not take into consideration the possibility of
future sea level rise.
The seawall has to be considerably strengthened and raised to counter the
effect of rising sea level. Other defensive measures would include increasing
the toe slope on the seaward side and systematic beach filling. On some
vulnerable coasts these measures have already been taken. The present height
and width of seawalls is determined according to the cost factor. Overtopping,
even at present levels, is not desirable, but because of the high costs, they
are so designed. Raising the seawall by as little as 30 cm would increase the
cost so exorbitantly that a country like Guyana could ill afford it.
A plan proposed by NEDECO (1972) to build a breakwater to the city's
coastline may have to be implemented. A beach fill scheme would also lessen the
problem.
Disposal of sewage in densely populated urban centers would pose severe
problems when the water table rises along with the rising sea level. At present,
a majority of houses are equipped with septic tanks. A rise in the water table
would render most of them useless, unless drainage is drastically improved.
In the eastern part of Guyana, where most of the agricultural land is
located, a well-integrated plan will have to be implemented to counter the
effects of sea level rise,, Sections of seawall will have to be rehabilitated
and drainage facilities improved.
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Daniel
At present, Guyana is equipped to take emergency measures in the event of
breaches in the sea defense system. The Hydraulics Division of the Ministry of
Agriculture is responsible for the maintenance of the sea defense system. It can
obtain resources from the government and the private sector without legislative
approval to incur expenses under "force account" to repair seawalls and contain
flow whenever necessary.
Routine surveillance and maintenance work is carried out by the regional
councils, but they do not carry out major repairs. Increasing problems
associated with shortages of manpower, materials, machinery, and funds have
prompted the government to reconsider centralization of sea defense.
Although the government is prepared to take emergency measures for sea
defense, a rapid sea level rise in the future and its potential impact are not
envisaged by the engineers. The problem of coastal erosion is perceived simply
as a cycle of erosion and accretion associated with the movement of mudshoals
in the nearshore region.
The Ministry of Housing, which regulates land use and implements housing
policies, does not restrict the construction of buildings near the seawall. In
Georgetown, some houses are less than 15 meters from the seawall. Major
government and private housing developments are located close to the seawall in
Enterprise, Nuitenzuil, Success, Lusignan, and along many parts of the coast.
The Ministry does not perceive the possible sea level rise to be an immediate
threat and has no policies to curb the construction of buildings close to the
seawall.
Similarly, the Guyana Water Authority (GUYWA), which controls the
distribution of potable water in Guyana, does not have a policy to deal with the
impact of future sea level rise on water resources. Even records of water
quality, transmissivity, recharge rates, and discharge rates of each well site
are not kept. Such data are obtained only when major surveys are carried out.
The last major survey was carried out by Worts in 1958.
Mining of sand from the cheniers is prohibited by law, a measure that would
prevent accelerated erosion. Similarly, several species of animals and birds
that take sanctuary in the coastal swamps and forests are included among the
endangered species specified in the Guyana Wild Life Preservation Act. The
recently formed Guyana Agency for Health Education and Food Policy is required
to review all development projects and submit environmental impact reports. Its
function is similar to that of the U.S. Environmental Protection Agency. Despite
all of these developments, there is no coherent policy to take countermeasures
against the possible rise of sea level in the future.
Coastal dwellers who live in areas that are repeatedly affected by erosion
and flooding are fully aware of the implications of a failure in the sea defense
system, but are unable to perceive the larger problem of sea level rise because
of lack of information. Recently, the possible threat of sea level rise and its
possible consequences were mentioned at two regional conferences held in Guyana.
The Commonwealth Secretariat also has completed a study on Guyana's coast and
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has warned the government of the possible consequences of sea level rise. These
recent developments have helped the government to perceive more clearly the
problem of sea level rise.
Surinam
Surinam's land development on the coast has followed a pattern similar to
that of Guyana. Most of its agricultural land is restricted to the coastal
plain. But unlike Guyana, it is not close to the coastline. Therefore,
extensive flood control and sea defense were unnecessary. In addition, Surinam's
coast is fairly stable, and coastal erosion is not as acute as on the coast of
Guyana.
The western Surinam coast, east of the Corentyne River where a large area
is under rice cultivation, is considered a stable area. The small farmers who
hold less then 4 hectares of land are mostly located along the rivers in
Comowijne and Surinam. Therefore, farmers in Surinam do not encounter erosion
and flooding as frequently as their Guyanese counterparts. They are not used
to perceiving the sea as a threat. However, an increase in sea level may cause
the rivers to overflow and damage low-lying rice farms.
Because large areas along the coast have been preserved as nature reserves
and Paramaribo is located several kilometers from the coast, the Surinamese do
not seriously consider the effects of sea level rise. Nevertheless, the
administration in Surinam commissioned NEDECO (1968) to study erosion along the
coast. NEDECO later conducted a more elaborate survey of the entire Guiana coast
(1972).
Surinam follows a vigorous environmental policy. Several organizations in
Surinam have carried out joint surveys with their Dutch counterparts on various
aspects of the environment. The Soil Survey Department of the Ministry of
Natural Resources has carried out research in collaboration with the Soil Survey
Laboratory of Wageningen, the Netherlands, on soil and erosion along the coast.
The Dutch navy has conducted hydrographic surveys off the coast of Surinam and
a Dutch engineering firm has been dredging the rivers frequently. The
International Maritime Organization (IMO) has also been conducting studies in
Surinam waters, as well as in Guyana and French Guiana. The Department of Lands
and Surveys and Aerial Photography has compiled maps of the coastal area based
on aerial photographs taken at regular intervals, and the Ministry of Agriculture
and Fisheries and the Department of Surveys of Waterways and Water Courses have
also carried out several hydrologic studies.
Since the coastal problem in Surinam is not as acute as in Guyana, there
is hardly any awareness among the coastal dwellers about the possible danger of
sea level rise. Because Surinam collaborates closely with several Dutch
organizations, it would not be difficult for the' government to take
countermeasures against the impacts of sea level rise when the need arises.
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French Guiana
Economically, French Guiana would be least affected by a future rise in sea
level. But physically it could suffer extensive losses of wetland areas.
The coastal area is included in the Cayenne arrondissement (district)
according to administrative divisions. It is subdivided into 14 communes, the
smallest French division. Each commune is no more than a village with basic
facilities, such as running water. Most decisions are made in Cayenne, if not
in Paris. Being an Overseas Department of France, French Guiana is totally
dependent on the metropole. Modern ideas on the environment, greenhouse effect,
future rise in sea level, etc., hardly trickle down to Cayenne. It still remains
in its colonial lassitude. The only modern development has been the construction
of a space center at Korou.
Few studies of the environment have been carried out in French Guiana.
Studies conducted along the Guiana coast by international consulting firms have
included the offshore region of French Guiana. The French navy also has
conducted regular hydrographic surveys off the coast of French Guiana. Any long-
term plan of action to counter the effects of sea level rise would have to
originate from France. Unless urban centers along the coast are seriously
threatened, responses from the administration in French Guiana are unlikely.
CONCLUSION
A rise in sea level, predicted as a result of global warming processes,
would severely affect the low-lying areas of the Guiana coast. They would be
affected by wetland losses, coastal erosion, a rise in the water table, and
saltwater intrusion into surface water and groundwater resources.
These impacts would vary along the entire length of the coast. Most parts
of Guyana would be affected because its coast lies below high water level. The
northwestern coast would be the most affected because of subsidence. The area
east of the Essequibo River, where most of the cultivation takes place, is
protected against wave erosion by some form of sea defense, ranging from concrete
seawalls to the naturally occurring cheniers. Wetland loss in the foreshore
area of this coast would be considerable, and the pressure on manmade sea defense
structures would increase even under a low scenario forecast for a 50-cm rise
in sea level.
Most of Surinam's coast is fringed by mangrove, and parts of it are formal
nature reserves. Furthermore, erosion is not as severe as on the coast of
Guyana. Under a low scenario forecast for a 50-cm rise, wetlands would migrate
inland. Wetland losses in French Guiana would be higher because low-lying areas
are limited. But economic losses would be minimal because its coast remains
largely undeveloped.
In general, the responses to the accelerated sea level rise in the region
are poor. Although Guyana's coastal dwellers have been battling the sea since
359
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Central and South America
the colonial period, such problems as erosion and flooding are perceived as local
phenomena. Few government organizations or local inhabitants consider the future
rise of sea level to be a serious threat. Recently, however, concern about the
consequences of future sea level rise has been shown at higher government levels.
Nevertheless, no efforts have been made to restrict developments along the
coastal highway.
In Surinam and French Guiana, the possible effects of sea level rise are
not seriously considered because most economic development, with few exceptions,
has largely taken place away from the coastline. Coastal dwellers in both these
countries do not endure as many problems as their Guyanese counterparts, and are
therefore less vulnerable..
BIBLIOGRAPHY
Augustinus, P.G.E.F. 1978. The changing shoreline of Surinam (South America).
Ph.D. Thesis Publication No. 95, Foundation for Scientific Research in Surinam
and The Netherlands Antilles, The Netherlands: University of Utrecht, 232p.
Augustinus, P.G.E.F. 1982. Coastal changes in Surinam since 1948. Proceedings
Furoris Congress on Future of Roads and Rivers in Surinam and Neighbouring
Region. University of Surinam. The Netherlands: The Delft University of
Technology, pp. 329-338.
Augustinus, R.G.F.G., and R.P.R. Mees. 1984. Coastal erosion and coastal
accretion between the estuaries of the Corentyne and the Essequibo Rivers: A
contribution to the coastal defense in the Republic of Guyana. The Netherlands:
State University of Utrecht, Laboratory for Physical Geography.
Brinkman, R., and L.J. Pons. 1968. A pedo-geomorphological classification and
map of the Holocene sediments in the coastal plain of the three Guianas. Paper
No. 4. Wageningen, The Netherlands: The Soil Survey Institute.
Daniel, J.R.K. 1984. Geomorphology of Guyana. Occasional paper. Dept. of
Geography, University of Guyana. Release Books, 72p.
Daniel, J.R.K. 1988. Sea defense strategies and their impact on a coast subject
to a cyclic pattern of erosion and accretion. Ocean and Shoreline Management
2:159-175.
Gibbs, R.J. 1967. The geochemistry of the Amazon River System: Part I. The
factors that control the salinity and the composition and concentration of the
suspended solids. Bull. Geol. Soc. Am. 78:1203-1232.
NEDECO. 1968. Surinam transportation study. Report on hydraulic investigation.
The Hague, The Netherlands: Netherlands Engineering Development Consultants,
293 p.
360
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Daniel
NEDECO. 1972. Report on sea defence studies. The Hague, The Netherlands:
Netherlands Engineering Development Consultants,
Starbroek News. 1989a. News item, May 3, 1989. Guyana Publications Ltd.
Titus, J.G. 1985. Sea level rise and the Maryland coast. In: Potential
Impacts of Sea Level Rise on the Beach at Ocean City, Maryland. J.G. Titus et
al., eds. Washington, DC: U.S. Environmental Protection Agency, p. 1-32.
361
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IMPACTS OF SEA LEVEL RISE ON THE ARGENTINE COAST
ENRIQUE J. SCHNACK
Laboratorio de Oceanografia Costera
Facultad de Ciencias Naturales
C.C. 45, 1900 La Plata, Argentina
JORGE L. FASANO
CIC y Centre de Geologia de Costas y del Cuaternario
Universidad Nacional de Mar del Plata
Funes 3350, 7600 Mar del Plata, Argentina
and
NESTOR W. LANFREDI
JORGE L. POUSA
CIC y Facultad de Ciencias Naturales y Museo
Universidad Nacional de La Plata
Paseo del Bosque, 1900 La Plata, Argentina
ABSTRACT
The Argentine coast exhibits a variety of environmental settings, including
estuarine and deltaic areas, marshes, sandy and pebbly shores, and cliff
exposures. Different wave and tide regimes operate along the coast.
Although erosion typifies much of the nation's 5,000-kilometer coastline,
these problems are particularly severe in the Province of Buenos Aires with 40%
of the country's total population and one third of its coastline. The main urban
developments, harbors, industrial complexes, and tourist resorts are located in
this province. Floods are very dramatic on the Rio de la Plata shores, which
have the highest population density. Here the water level rose 4.75 m in 1940
and 3.85 m in 1958. In the latter case, more than a half million inhabitants
were affected in different ways. The Coriolis effect has been regarded as a
major cause for the storm surges on the Argentine side of the Rio de la Plata.
South of the Rio de la Plata, the oceanic shorelines show dissipative
characteristics with a significant littoral drift (between 400,000 and 1 million
m3/year). There is high erosion in many areas; for exalmple, the Mar Chiquita
beach has been retreating more than 5 m/year during the last three decades.
Beach-sand mining for construction also contributes to erosion. Unplanned urban
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Central and South America
development can also account for property Loss and damage. At Mar del Plata, the
main tourist resort in Argentina, groins, jetties, and seawalls have been
constructed since the beginning of the century without the utilization of basic
geomorphological information, thereby partially solving local problems but
increasing erosion along downdrift areas.
Fifteen tide-gauge stations, a few of them with extensive records, are
distributed along the Argentine coast. The 64-year record of Puerto Quequen,
located 120 km southwest of Mar del Plata, shows a rise in sea level of 16.09
cm/100 years. This locality seems to be the most reliable, in terms of both
historic data and tectonic stability.
Coastal plain flooding is also critical in areas such as the Rio Salado
Basin, where topographic gradients are extremely low and the phreatic surface is
very shallow. In addition, salt intrusion of coastal aquifers can be predicted
as a combined result of sea level rise and coastal retreat. Overpumping has
already created this type of problem in the city of Mar del Plata.
Urban development on the sandy coastline of the northern Buenos Aires
Province has caused the elimination of extensive sand dunes, which are the only
available storage bodies for groundwater. Beach erosion in this area is partly
due to the restriction in sediment supply from the sand dunes.
The accelerated rate in sea level rise predicted for the next century will
exacerbate the described processes. Although several impacts can be predicted
for the Patagonian coast, they are far less dramatic than those in the northern
coast because of the much lower population density and urban/industrial
development.
In the absence of a general legal/organizational framework, institutional
responses to coastal problems are limited to specifically oriented government
offices, mostly at the provincial level (e.g., hydraulic departments, water
resources agencies). Some municipal counties backed by community organizations
are involved in dealing with the development and management of coastal resources,
although they usually lack expertise. It is expected that future efforts, based
upon scientific evidence, will result in the adoption of legal and administrative
procedures for proper use and protection of the coastal zone.
INTRODUCTION
In recent years, increasing atmospheric concentrations of C02 and other
greenhouse gases is producing a global warming, which could expand ocean water
and melt polar ice sheets. Predictions of future sea level rise suggest a 1-m
rise within the next 60 to 150 years (Hoffman, 1984). Estimates of future sea
level rise vary according to the relative contribution of different factors
involved (thermal expansion, retreat of alpine glaciers, melting of the Greenland
and Antarctic ice-sheets). Gornitz et al. (1982) established that "eustatic" sea
level is presently rising at a rate that exceeds 1 mm/year.
364
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Schnack, et al.
Lanfredi et al. (1988) have estimated that sea level is currently rising
1.6-mm/year in Puerto Quequen, which probably has the only reliable tide-gauge
station in Argentina. This station has a 64-year record and is located in a
technically stable area, which allows for a true eustatic component to be
considered.
Even without considering the present or predicted rates in sea level rise,
the Argentine coastal areas are undergoing several impacts (shore erosion, salt
intrusion, pollution, etc.) as a response to both natural and predominantly
human-induced processes. If the rate of sea level rise were to accelerate as
predicted, it would be necessary to adopt policies and management regulations to
adequately deal with it. Government and community structures would play an
important role in this regard.
CHARACTERIZATION
Natural Features
According to the Koeppen climatic system, the Argentine coast is temperate
from the Parana Delta down to 40 km SW of the Rio Negro, arid from there to Rio
Gallegos, and "cold humid" to the south of that location.
The coastline of Argentina is about 5,700 km long (Figure 1), not including
the Malvinas and Antartica. (Note: While Argentina claims both of these
sectors, the United Kingdom currently administers the Malvinas (Falkland Islands)
and Argentine ownership of the Antarctica sector is not universally recognized.)
A very wide continental shelf extends offshore, reaching in some places, over 800
km in width. Main coastal landforms (Figure 1) are deltas, estuaries, marshes,
cliffs and wave-cut terraces, sandy and pebbly shores, and ice-fringed coastlines
(Antarctic area). Sandy coastlines are typical along the strip extending from
Cabo San Antonio to Mar Chiquita Lagoon, in northeastern Argentina, where a 150-
km-long barrier develops. In this area, the shoreline shows dissipative
characteristics with a significant littoral drift (between 400,000 and 1 million
mVyear). Figure 2 illustrates a number of coastal features.
Pebbles are a typical component of the Patagonian shores. They originate
in the reworking of mainly Quaternary pebbly substrates from continental
terraces, pediments, and fluvial deposits. Wave and tidal action at different
sea level positions resulted in several raised shorelines of Pleistocene and
Holocene age, which are a typical feature on the coastal plain. These high sea
level stands are also well represented in the Mampas coastal plains. In all
cases, fossil molluscs are present in the sediments; these constitute the best
tools for correlation and dating (Feruglio, 1950; Rutter et al., 1989).
It is known that sea level was higher than today at least three times
during the Quaternary: (1) during the Holocene (maximum sea level about 6,000
years ago), (2) during the last interglacial (120,000 years ago), and (3) during
a previous interglacial. On the Argentine shelf, the Wisconsin shoreline was
dated in about 18,000 years ago, at depths beyond 100 m (Fray and Ewing, 1963)
365
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Central and South America
x
j Bt
JcoMooom
fftlVAOAVIA
\Oflf*
Figure 1. Distribution of predominant geomorphic features along the Argentine
coast (Schnack, 1985).
366
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Schnack, et al.
Brackish and saltwater marshes are present along the coast, the former
mainly in the northeastern sector of Buenos Aires Province (Samborombon, Mar
Chiquita) and also in Bahia Blanca and further southward (Figure 1). The latter
are predominant in Patagonia, where macrotidal environments prevail. The
Patagonian coast is predominantly rocky, and cliffy, whereas the Buenos Aires
(Pampas) coastline alternates between extensive low-lying and cliffy areas.
Cliffs in the Province of Buenos Aires are generally composed of
semi-consolidated, deposits of the Plio-Pleistocene age, reaching their maximum
altitude (25 m) in the vicinities of Mar del Plata. Only in this city, an old,
lower Paleozoic quartzite outcrops at the sea. The Patagonian coast exhibits
mainly Tertiary sediments, both of marine and continental origin. Lastly,
Quaternary, glacially derived sediments outcrop in eastern Tierra del Fuego, and
Cretaceous marine rocks are the main feature on the Beagle Channel area.
Although there are several embayments along the whole Argentine coast, Mar
Chiquita Lagoon inlet is the only one that has the proper attributes of such a
feature. At a typical microtidal setting, the Mar Chiquita inlet (less than 100
m wide and less than 3 m deep in the channel axis) shows both seasonal (or
storm-driven) and historic shifting. As can be seen in Figure 3 (for location
see Figures 1 and 4), the inlet has a historic trend of northward shifting
coincidental with the regional net littoral drift. However, engineering works
have modified the natural adjustment of the inlet. In the tide-dominated
Patagonian coast, a few embayments exhibit some features that are common
attributes of tidal inlets. At San Antonio Bay, in northern Patagonia (Figure
1), a well-developed flood-ebb delta is active, but no freshwater inflow exists
in the area.
Wetlands are distributed all along the Argentine coast. The most typical
and extensive are those in Bahia Samborombon, where muddy, tidal flats develop
along 100 km of coastline, at the Salado Basin depression (Figures 1 and 4).
Also, tidal flats and marshes are present from Bahia Blanca southward. Wetlands
along the Patagonian coast are not so extensive. They are more restricted to
low-lying areas at the several embayments. In all cases, marshes are temperate
and show the presence of typical vegetation (Soartina. Salicornia). The general
topography at low-lying areas would allow marsh and vegetation to shift inland
if a rapid sea level rise occurred. In some cases, e.g., restricted marshes in
Patagonia, where a rocky slope borders a narrow coastal plain, migration would
be limited to a few hundred meters, thus causing marshes to disappear.
The most prominent estuarine environment is the Rio de la Plata, a water
body shared by Argentina and Uruguay. As a continuation of the Parana River
Delta, the Rio de la Plata has a submerged deltaic front composed of silt-clay,
but sand banks also occur. The main body is freshwater, but the outer part is
brackish. Although no river discharge occurs at present, Bahia Blanca, a
brackish-water environment with mesotidal action, hosts one of the most important
harbors. Here, muddy environments and suspended material's, as well as drifting
sandwaves and channels, are driven by tidal currents.
367
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Figure 2 (A-C). Coastal features of Argentina.
(A) Erosive coastline at the edge of the Pampas plain,
looking north. In the background is Mar Chiquita
Lagoon, where a sandy barrier develops to the north.
The coastal plain has an extremely low topographic
gradient. A sea level rise makes this region
vulnerable, both to beach erosion (dune destruction) and
to flooding. Both processes are already occurring to a
high degree because of human influence.
(B) Low (<2 m) eroding cliffs approximately 20 km north
of the Mar del Plata. Beach sediments are scarce. Note
the coastal road.
(C) Protected beach (see groins) at Santa Clara, a
resort town 18 km north of Mar del Plata.
-------
ff Figure 2 (D-F).
;t| (D) Stone defense to rebuild beaches at Mar del Plata
'£ (constructed in the early 1980s). By the 1970s, beaches
in this area were lost. Many other beaches are
protected by groin systems.
(E) 15 km south of Mar del Plata center, eroding
beaches in an area where sand mining for construction is
doen. Note the improverished dune "relicts" resting on
an approximately 10 m high cliff which now is being
reactivated by dune disappearance.
(F) Part of a tidal salt marsh in Coleta Mabespina
(Patagonia). Many similar environments of varying area
(usually small in Patagonia and lareger in Buenos Aires
Province) are distributed along the Argentine coast.
Some may not migrate landward as sea level rises because
of topographic (hills) or human barriers, hence, a
significant wetland loss may result.
-------
goo too o
1000 3OOO
IOOO 500 0
•wrens
*."
-~-' *"
1000 800 __ 0
'
IN I»CW
8000
gg» mere*?
>^
*** ^ T7sc''"-T^"*'""'"""" ---""•"- -^t Li- -•*"""
v.v^.v,. ^wvv«v ...v , :,--'"
IOOO 900 0 JOOO
x N
I9O9
Figure 3. Historic migration of Mar Chiquita Lagoon inlet.
Several other estuaries are represented in the coast of Patagonia by the
river outlets under macrotidal conditions, but few detailed studies have been
done in relation to water chemistry and dynamics. Bottom sediments are variable,
with gravels, sands, and muds in different proportions according to the source
and dynamics. In this macrotidal setting, most of the fine sediments are
transported in suspension. Because of the large tidal amplitudes, some of these
estuaries have extensive uncovered areas during the ebb tide. One such areas is
the Rio Gallegos outlet, where tidal ranges reach 12 m (Figure 1).
Cultural and Economic Features
According to Brandani and Schnack (1987), human activities along the
coastal zone of Argentina include urban development and recreation; industry and
commerce; port activities; fishing, military and naval bases; research; arid
conservation of natural resources. In certain areas, beach sand is mined for
building purposes. Other activities include: mining of coastal gravels arid
shells (from Quaternary deposits), offshore oil exploration and extraction, and
algae exploitation. The general features of the major Argentine harbors are
shown in Table 1.
370
-------
Schnack, et a7.
Figure 4. General topography of the Province of Buenos Aires. Note the
extremely gentle slope in the Salado Basin depression and in the Rio Colorado-Rio
Negro region.
371
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Central and South America
Table 1. General Characteristics of the Main Harbors in Argentina
PORT
Buenos Aires
Mar del Plata
Quequen and
Necochea
Bahia Blanca
Puerto Madryn
Zone of Comodoro
Rivadavia
Puerto Deseado
Ushuaia
LOCATION
0 = 34°
0 = 58°
0 = 38°
Q = 57°
0 = 38°
0 = 58°
0 = 38°
n = 62°
0 = 42°
Q = 65°
0 = 45°
Q = 67°
0 = 47°
fi = 65°
0 = 54°
34'
23'
03'
33'
35'
42'
47'
16'
46'
02'
52'
29'
45'
55'
49'
S
W
S
W
S
W
S
W
S
W
S
W
S
W
S
PURPOSE
General cargo,
bulk and con-
tainer bulk
terminal
Fishing port
and bulk
terminal
Grain in bulk
terminal and
fishing port
General cargo,
grain in bulk
terminal, and
fishing port
General cargo
Oil terminal
and fishing
port
Fishing port
Fishing port
and general
FACILITIES
Wharves, berths,
cranes, ware-
houses, sheds,
grain elevators
Wharves, berths,
cranes, ware-
houses, sheds,
grain elevators
Wharves, berths,
grain elevators,
warehouses
Wharves, berths,
cranes, grain
elevators, ware-
houses, sheds
Wharves, berths,
cranes, ware-
houses
Wharves, berths,
cranes
Wharves, berths,
cranes, ware-
houses
Wharves, berths
ANCILLARY
FACILITIES
Dockyards,
shipyards
Dockyards
Workshops
and small
dockyards
Workshops
and small
dockyards
Small
dockyard
Workshops
Workshops
Small
dockyard
ECONOMIC
ACTIVITIES
Chemical, textile,
metallurgical, and
food industries
Fishing irrLstries,
packing houses,
agricultural and
cattle- raising
activities
Fishing and food
industries (meat
and flour), agri-
cultural and
cattle- raising
activities
Agricultural and
cattle-raising
activities
petrochemical
industries
Aluminum factory,
fishing indus-
tries, and sheep-
raising activities
Oil fields, sheep-
raising activi-
ties, and fishing
Sheep- raising
activities, and
food industries
Fishing
activities
0 = 68° 13' W cargo
372
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Schnack, et a 7.
Demography
In Argentina, over 41% of the population inhabits the coastal zone.
Population densities vary along the coast. A general gradient develops from
north to south, with the greatest population numbers and densities in the
nation's capitol, Buenos Aires city, and associated urban centers. The lowest
population concentrations and variety of activities are found in Patagonia, south
of the Colorado and Negro Rivers, where a few small urban centers support most
of the regional population and activities.
Most of the largest urban centers and 25% of its urban centers with more
than 5,000 inhabitants are coastal. However, the fact that the federal capital
(Buenos Aires city), with only 17 km of coastline along the Rio de la Plata,
contains 10% of the country's total population must be considered. Buenos Aires,
together with its suburbs (Greater Buenos Aires) is estimated to have ten million
inhabitants (30% of the national population).
The continuing historical pattern of population migration to the city
(averaging a yearly growth rate of 47% between 1869 and 1980, against 13% for the
national population growth) has been caused by mutually reinforcing factors: the
Port of Buenos Aires handling 90% of the total waterborne transit and commerce
of the country; the siting around the city of many of the nation's industrial and
productive activities; and the concentration of a strongly centralized federal
government.
The Province of Buenos Aires, with more than 1,500 km of coastline and
nearly 12 million people (40% of the national population) is by far the most
important coastal province (state) of Argentina. The average density is 35.3
people/km2 and over 90% of the population lives in urban centers, the largest of
which are all coastal (Figure 5): La Plata with 460,000 people, followed by Mar
del Plata with 410,000 people, and Bahia Blanca with over 220,000 inhabitants.
Rural areas are dominant along most of the coastline. It is here -- not the
cities -- where the topography is vulnerable to major inundation from sea level
rise, as can be observed in the Salado Basin depression with extremely low
topographic gradients (Figure 4).
The Patagonian region varies in population distribution according to the
specific province. In Rio Negro Province, only 12.5% of the population live in
coastal centers. This is due to the strong economic influence of the Rio Negro
Basin and the city of San Carlos de Bariloche, at the foot of the Andes. Farther
south, in Chubut, more than 80% of the 263,000 inhabitants live in coastal urban
centers. Santa Cruz Province, the third largest in Argentina, has only 114,900
people and its density is correspondingly very low: only 0.5 people/km2. The
National Territory of Tierra del Fuego has only 40,549 inhabitants with 38,515
people living in just two coastal cities: Rio Grande (21,969) in the north, and
the capital of Ushuaia in the south (16,546).
373
-------
1000-5000
5000 - 20000
20000-100000
100000-500000
>500000
Figure 5. Population of urban centers on the Argentine coast.
374
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Schnack, et al.
Land Use
Low-lying coastal lands are mainly rural and are found mostly in the
Province of Buenos Aires (Salado Basin in the north, and the southern tip of the
state, from Bahia Blanca to Bahia Anegada). The Salado Basin coastal plain,
facing Samborombon Bay, is largely devoted to agriculture (mainly cattle).
Because this is a flood-exposed area, activities are somewhat restricted.
The area immediately above the highest tide levels in Bahia Blanca is partly
occupied by housing developments related to the various industries established
nearby; much of this area is subsiding. South of Bahia Blanca, the coastal area
is mainly devoted to agriculture. In the northern, sandy belt of Buenos Aires
Province (Figure 1), and extending southward to Mar del Plata and Miramar,
tourism is the main land use.
At the Salado Basin, the recurrence of historic floods led the Public Works
authorities to construct drainage canals toward Samborombon Bay at the beginning
of the 20th century. However, results have not been optimal, as floods have
occurred ever since.
As a general case, the Patagonian coastal lands are mainly devoted to sheep
raising; a very localized algae farming also takes place.
Fisheries
Most Argentine fisheries are export-oriented. In 1981, the country
contributed 1.69% of the world exports (Espoz, 1985). Fisheries are mainly found
in shelf waters. Fish catches are by far predominant, but molluscs and
crustaceans are also important resources. Oyster and scallop beds are present
in shallow waters in northern Patagonia. Crustaceans (e.g., prawn, king crab)
represent typical catches in Patagonia and Tierra del Fuego.
Commercial sea-farming is not commonplace along the Argentine coast. Only
a few oyster and mussel farming projects are being carried out in San Antonio
Oeste, and crustaceans projects in Mar del Plata and Puerto Madryn. In all
cases, they are only at the experimental stage.
The main fishing activities are centered in the ports of Mar del Plata, with
most of the fishing fleet and processing installations, and more than 70% of the
total yearly catch. Other important harbors are: Ingeniero White (Bahia
Blanca), San Antonio Este, San Antonio Oeste, Puerto Madryn (Figure 4).
Additional small harbors are distributed along the Patagonian coast.
IMPACTS OF SEA LEVEL RISE
Considering the variety of environments and the socioeconomic importance of
certain regions of Argentina, a rapid sea level rise, as predicted for high and
low scenarios (Hoffman, 1984), would result in major damage to coastal areas in
low-lying, flood-exposed plains and in open marine beaches and cliffs.
375
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Central and South America
Beach Erosion
Erosion is an ongoing process, even at the present rate of sea level rise
which has been estimated for the region as 1.6 mm/y (Lanfredi et al., 1988). The
coastline between Cabo San Antonio and Mar del Plata is undergoing severe
erosion, partly due to natural causes (e.g., lack of fluvial sediment input, sea
level rise) and mainly because beach-sand mining and dune urbanization take place
without any planning or environmental assessment. Engineering structures have
been installed to protect the shore, but in many cases they operate locally and
cause downdrift erosion by trapping the transported sediments. At Mar del Plata
(Figure 6) several groins and jetties have been installed throughout this
century. Also, Mar del Plata harbor certainly influences erosion in the
downdrift direction (northward in the whole region) by breakwaters at its
entrance.
Since erosion is a typical problem of the sandy shoreline and of the cliff
exposures of Buenos Aires Province, sea level rise should only exacerbate the
existing problems. At Mar Chiquita beach (Figures 4 and 7), a shore retreat of
more than 5 m/y has been determined (Schnack, 1985), causing land losses and
property destruction. This is the highest rate in shoreline retreat established
for the whole coast of Argentina. Many other localities north of Mar Chiquita
also show increasing erosion as a consequence of human intervention.
In a well-known paper, Bruun (1962) describes a method for determining
shoreline retreat produced by sea level rise. He assumes that after a sea level
rise the beach profile will simultaneously undergo an upward and a landward
shift, though retaining its original shape. Thus, the final beach profile
displacement can be considered as the result of two rigid translations: a
vertical one and a horizontal one, the latter being the shoreline retreat.
For the given scenario (Hoffman, 1984), considering a 0.50-, 1.00-, arid
2.00-m sea level rise to take place in a period of 50 years, a beach profile at
Punta Medanos (Figure 4) would undergo a retreat of 1.93, 3.86, and 7.73 m/yr,
respectively. These estimates show the dramatic impacts of predicted, rapid sea
level rise. Furthermore, human-induced erosion represents a major factor that
must be considered at least as effective as sea level rise itself.
Hvdrological Impacts
Although hydrological problems along most of the Argentine coast may be
foreseen as a direct consequence of sea level rise, the Buenos Aires Province
shows most clearly the effects of anthropogenic activities due to its high
population density, despite the fact that this population is concentrated at very
specific points. These activities are responsible for the shifting or breakdown
of the natural equilibrium.. This is particularly true when dealing with
groundwater resources, for processes operate at different intensities and time
scales. Moreover, as groundwater motion is slow, thus hindering direct
observation, the consequences arising from management decisions may not be
noticed for several years, and so the results could be irreversible when
detected.
376
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• 22.6
.ZJ4
Punlo Igltsta
-1931-1939
—1324-1928
Schnack, et al.
LOCATION MAP
}gj2l930 - modified in I960
-1936
1930 - 1932
Punto Pltdroi
(Torrtrfo dil Monjt)
1924- modified In 1961
je»oo's-
•TS,
(•1932 Groin construction
Contour interval: 10m
0 1 2km
Figure 6. Engineering structures at Mar del Plata. Except for the harbor, all
the structures have been installed to protect the shore from erosion.
377
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Central and South America
Mar Chiquita
Lagoon
-11—11—11
II M II I
JL__JL__JL__JL
SOUTH ATLANTIC OCEAN
200 300 meters
' 1
Figure 7.
property.
Shore retreat at Mar Chiquita beach. Note the land losses, including
Besides the highly disturbed deltaic area, on which little, if any,
background information is available, three main coastal environments can be
considered in the province: cliffed, sandy, and marshy shores. As a result of
sea level rise, saltwater encroachment can take place, the impacts being mainly
dependent on the physical coastal setting, climatic variation, and human
factors.
A common feature of the three environments is the lack of sufficient
available data, with the exception of some urban areas. This poses serious
restrictions on the reliability of numerical solutions, for they depend upon both
the quality and quantity of the input data.
In Mar del Plata, located at the easternmost extreme of the Tandilia Sierra,
the aquifer consists of partially reworked Plio-Pleistocene loess-like sediments,
378
-------
Schnack, et al.
with an average depth of 100 m. It had undergone over-pumping until the 1960s.
As a result, seawater intrusion was detected, and nearly all the pumping wells
located within the city and close to the coast were abandoned. The exploitation
zone had to be shifted to the north. This action led to a restoration of
groundwater tables which had flooded buildings, and has acted as a hydraulic
barrier preventing a landward migration of the freshwater/saltwater interface.
Today the situation in the well field can be considered at equilibrium. Hence,
in Mar del Plata the landward migration of the saltwater front due to sea level
rise would be negligible when compared with the human-induced migration.
A different situation can be observed toward the north of Mar Chiquita (a
small town located about 30 km north of Mar del Plata). A sand dune barrier,
which extends for more than 150 km and becomes progressively wider northward,
overlies marine-estuarine sediments of Holocene and Pleistocene age (Fasano et
al., 1982; Parker, 1980). At the low-lying coastal plain of Samborombon Bay,
sand dunes are replaced by shelly beach ridges (Sala et al., 1977). Both sand
dunes and shelly ridges are the only available freshwater storage bodies. These
storage bodies can be idealized as if they were an elongated island surrounded
by seawater on the east and brackish-to-salty continental waters on the west.
Because of this, the sandy barrier could be largely influenced by a eustatic sea
level rise. According to the erosion rate measurements, e.g., 5 m/y at Mar
Chiquita (Schnack, 1985) (Figure 6), the horizontal component exceeds in orders
of magnitude the rise in sea level (1.6 mm/y) in the vulnerable sandy coastline.
The landward migration of the interface would be largely controlled by the beach
retreat. Changes in altitude of the base level play a minor role. In fact, as
stated by Urish and Ozbilgin (1989), the groundwater/free seawater interface is
a highly dynamic boundary. On sandy sloping beaches, tidal fluctuations and wave
run-up cause an effective mean sea level generally higher than free-water mean
sea level.
Kana et al. (1984) summarizes the different opinions about the effect of sea
level rise on the position of the freshwater/saltwater interface in a water table
aquifer. Some state that the whole system would shift upward and landward
proportionally to sea level rise and shoreline retreat, respectively. Others
consider that freshwater rise would not follow sea level rise at the same rate,
but would be some fraction of it as a consequence of decreasing recharge and
increasing discharge.
Under nondeveloped conditions, the lens-shaped groundwater reservoir can be
regarded as being in dynamic equilibrium by direct recharge from precipitation
and discharge to the sea. It seems reasonable that a sea level rise of the
magnitude considered here is sufficiently slow to allow groundwater to reach a
new equilibrium position.
Floods are very dramatic on the Rio de la Plata shores, with the highest
population density. Here the water level rose 4.75 m over datum in 1940 and 3.85
m in 1958. In the latter case, more than a half million inhabitants were
affected by property losses and other damages.
379
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Central and South America
The marshy areas of Buenos Aires Province extend mainly south of Bahia
Blanca and also border Samborombon Bay. In these environments, erosion does not
seem to be a dominant process. Due to the extremely gentle topographic gradient,
minor positive variation in sea level causes the flooding of extensive areas with
consequent land loss (Figure 3). This would allow an inland movement of
seawater, resulting in its intrusion into the groundwater system. Additional
effects, such as longer-lasting floods are linked to higher water tables, which
inhibit the infiltration process during precipitation. From the point of view
of groundwater as a resource, these effects would not pose a severe risk because
brackish-to-salt water dominates.
Other Impacts
A rapid sea level rise would result in several disturbances of various
degrees of importance, depending on the urban development, industries, general
resources, and installations.
Impact on harbors (Table 1), in any of the predicted scenarios, would be
high in Buenos Aires and Bahia Blanca because of the flat, low-lying terrain of
the surrounding areas where very important economic activities take place. At
Mar del Plata, Quequen, Puerto Madryn, and Comodoro Rivadavia the impact would
be only moderate and the affected areas would be those next to the shoreline.
Landscape damage and pollution effects can be predicted. At Puerto Deseado and
Ushuaia the impact would be low, mainly restricted to the port facilities and
their adjacent areas.
Wetlands would also be affected, either by migration and recolonization or
by disappearance when migration is restricted by highlands or hard substrates.
As we consider a rapid sea level rise, it is likely that inland migration of
wetlands would keep pace in vertical growth relative to the rate of sea level
rise. Under these conditions, a rough estimate suggests an average loss of 50%
of the wetlands area.
The inland transportation of pollutants would also be a direct effect of a
rising sea level. This would be particularly important in heavily populated,
industrial, and harbor areas (Buenos Aires, Mar del Plata, Bahia Blanca), as well
as in Patagonia, where oil spills may be transported inland (Comodoro Rivadavia).
Although they are not yet in existence, sea-farming establishments may also be
affected to some extent.
RESPONSES
Institutional Background
Government and legal instruments for coastal planning and protection are
dispersed and no specific: framework for coasts is available. A document on
national priorities for marine and coastal research (SECYT, 1983) identified the
lack of properly trained personnel and of coordination between research and
management activities as significant issues.
380
-------
Schnack, et al.
At present, coastal issues show several problems related to organizational
levels: lack of coordination and overlapping among public agencies; confusing
and contradictory laws and regulations, and insufficient resources for adequate
coastal zone management.
The conflicts between pollution, recreation, and coastal protection, for
instance, are significant in the larger summer resorts of Buenos Aires Province,
such as Mar del Plata. Coastal erosion has led to the construction of a variety
of costly defenses in order to prevent the disappearance of beach resources and
to reverse the destructive tendencies caused by sand-trapping devices (mainly
groins). These defenses produce the desired effect in one place, i.e.,
accumulation of sand, but at the expense of other beaches, which end up being
heavily eroded, as is the case between Mar Chiquita and Miramar (Figures 4 and
6). These conflicting activities in Buenos Aires Province have an institutional
background. Construction of coastal defenses is the responsibility of a
Directorate of the Provincial Ministry of Public Works, and a separate
Directorate of the same Ministry grants permits for sand extraction from beaches
and dunes, an erosion-triggering activity. No integrated planning procedures
exist among the Directorates within the Ministry. Moreover, while tourist use
and exploitation of the shore are the domain of municipal governments, port
activities (a major source of pollution and erosion in Buenos Aires and Mar del
Plata, among others) are under federal government jurisdiction.
Table 2 presents a summary of governmental units related to functional or
sectorial aspects of marine and coastal zone management. The hierarchical level
for each government unit (whether national or provincial) is shown in Roman
numerals (I is the highest and corresponds to the chief executive's office,
whether the nation's president or the governors). When some sector is also
represented within the government structures of coastal provinces, its
hierarchical level is indicated. Only names of the federal institutions are
listed under the "nation" heading. Provinces are, from north to south: BA ,
Buenos Aires; RN, Rio Negro; Ch, Chubut; SC, Santa Cruz, and TF, Tierra del
Fuego.
Table 2 lists only those sectors currently related to coastal zones for
which some governmental unit exists. For farming, ranching, education, and
forestry, no special orientation to coasts is found within governmental
structures. For the last sector, this is understandable since the Argentine
shoreline is essentially a treeless corridor (Brandani and Schnack, 1987).
However, farming practices affect estuaries and coastal wetlands through the
concentration of runoff products, agrochemicals, and sediments.
Defense and production are concentrated in units of relatively high
hierarchical level within the federal government. Development and wildlife
management have a higher priority in the provinces than at the national level.
Development is mostly industrial in nature, and ecological management emphasizes
the exploitation of specific renewable resources for production or consumption,
rather than the conservation of integrated environmental systems.
381
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Central and South America
Table 2. Argentine Governmental Organizations With Primary Policy Authority
for Marine and Coastal Resources
Provinces
Hierarchical
Sector
Defense operations
Foreign policy
Customs
Port administra-
tion
Port activities
Port maintenance
Navigation6
Fisheries control
Coastal tourismd
Research (civil-
ian)c
Research (mili-
tary)0
Shore protection
Wildlife manage-
ment
Parks- -conserva-
tion
Zoning—Pollu-
tion control*
Waterworks
Oil and gas
development*
Mining
Industrial
development
Name level
Armada
Ministerio de Relaciones Exteriores
Direccion de Aduanas
Administracion General de Puertos
Capitania General de Puertos
Direccion de Construcciones
Portuarias y Vias Navegables
Prefecture Naval
Direccion de Pesca
Subsecretaria de Turismo
Consejo Investigaciones Cientificas
y Tecnicas
Universidades Nacionales
Institute de Investigaciones
Pesqueras
Direccion del Antartico
Direccion de Investigacion y
Desarrollo
Servicio Hidrografia Naval
Direccion de Fauna Silvestre
Direccion de Ordenamiento Ambient a I
Obras Sanitarias de la Nacion
Secretaria de Energia
Yacimientos Petroliferos Fiscales
Gas del Estado
Secretaria de Hineria
Secretaria de Desarrollo Regional
II
II
IV
IV
V
V
IV
III
IV
IV
IV
IV
IV
III
III
ne
VI
ne
V
IV
III
IV
IV
III
IV
BA
ne
ne
ne
ne
ne
ne
ne
III
III
IIa
IVe
ne
ne
ne
ne
III
IV
IV
IU.
IV3'
ne
ne
ne
III
IV
RN
ne
ne
ne
ne
ne
ne
ne
III
III
IIa
IVe
ne
ne
ne
ne
III
III
III
III
ne
ne
ne
ne
III
IV
Ch
ne
ne
ne
ne
ne
ne
ne
IV
IV
nee
IVe
ne
ne
ne
ne
IV
III
IV
IV
ne
ne
ne
ne
IV
III
SC
ne
ne
ne
ne
ne
IV
ne
IV
III
IV
ne
ne
ne
ne
ne
III
III
IV
IV
ne
ne
ne
ne
IV
III
TF
ne
ne
ne
ne
ne
ne
ne
IV
III
nee
ne
ne
ne
ne
ne
ne
IV
IV
IV
ne
ne
ne
ne
IV
III
More than one governmental unit deals with sector.
bln addition to several governmental units, national companies participate in sector.
°Separate units are dedicated to sector with different objectives.
University research is actually carried out by Departments or Institutes, with lower hierarchy than
indicated.
\ocated in coastal provinces where they research according to regional needs.
'some coastal cities may have a company providing primary services.
ne = Non existing.
Source: Brandani and Schnack (1987).
There is no specific legal framework for coastal issues at either the
national or provincial level in Argentina. Some legislation related to other
aspects (e.g., control of pollution by naval vessels, fisheries, etc.) considers
a few coastal aspects. Also, a number of provincial decrees (e.g., to prevent
sand mining on beaches) and municipal resolutions provide some approaches to
solving coastal problems from a legal point of view.
382
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Schnack, et a7.
Expected Responses to a Sea Level Rise
If we consider the preceding paragraphs, it is clear that sea level rise is
not an issue at the institutional or the general public levels. Only a small
part of the scientific population regards this as an important problem. In
addition, there is insufficient evidence, from an observational basis, to really
evaluate if a true sea level rise is occurring throughout the entire coastline.
Most of the erosion and environmental disturbances are due to human intervention
on coastal areas. Moreover, it must be considered that other hazards, such as
inland flooding, earthquakes, landslides, and other phenomena, seem to have more
dramatic effects and general concern among the public and institutions because
they tend to affect the economy more noticeably.
However, if an integrated, environmental policy is established, the coastal
issue may become progressively more important. Coastal protection would be
seriously considered and sea level rise properly regarded as an important factor.
Based upon scientific evidence, future efforts should result in the adoption
of legal and administrative procedures for proper use and protection of the
coastal zone.
BIBLIOGRAPHY
Brandani, A.A. and E.J. Schnack. 1987. The Coastal Zone of Argentina:
Environmental, Governmental and Institutional Features. Journal of Shoreline
Management 3:191-214.
Bruun, P. 1962. Sea Level Rise as a Cause of Shore erosion. Journal of
Waterways and Harbors Div. 88:117-130.
Caviglia, F.J. 1988. Intrusion salina en el Rio de la Plata. I.T.B.A., Buenos
Aires, 38 p.
Espoz Espoz, M. 1985. Introduccion a la Pesca Argentina. Fundacion Atlantica,
Mar del Plata, 336 p.
Fasano, J.L., Hernandez, M.A., Isla, F.I. and E.J. Schnack. 1982. Aspectos
evolutivos y ambientales de la laguna Mar Chiquita, Provincia de Buenos Aires,
Argentina. Oceanologica Acta No. Esp., 285-292.
Feruglio, F. 1950. Descripcion geologica de la Patagonia. Y.P.F.
Fray, C. and M. Ewing. 1963. Pleistocene sedimentation and fauna of the
Argentine Shelf. In: Wisconsin Sea Level as Indicated in Argentine Continental
Shelf Sediments. Proceedings of the Academy of Natural Sciences of Philadelphia.
115:113-126.
Hoffman, J.S. 1984. Estimates of future sea level rise. In: Greenhouse Effect
and Sea Level Rise. M. Barth & J. Titus, eds. Van Nostrand Reinhold Co., New
York. 79-103.
383
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Central and South America
Kana, T.W., Michel, J., Hayes, M.O. and J.R. Jensen. 1984. The physical impact
of sea level rise in the area of Charleston, South Carolina. In: Greenhouse
Effect and Sea Level Rise.. Van Nostrand Reinhold Co., New York, 105-150.
Lanfredi, N.W., D'Onofrio, E.E. and C.A. Mazio. 1988. Variations of the mean
sea level in the southwest Atlantic Ocean. Continental Shelf Research.
Parker, G. 1980 Estratigrafia y evolucion morfologica durante el Holoceno en
Punta Medanos (Planicie costera y plataforma interior). Provincia de Buenos
Aires. Simp, sobre Problemas Geologicos del Literal Atlantico Bonaerense, Com.
de Inv. Cient. de la Provincia de Buenos Aires. Resumenes (La Plata). 205-224.
Rutter, N., Schnack, E., del Rio, J., Fasano, J., Isla, F. and U. Radtke. 1989.
Correlation and dating of quaternary littoral zones along the Patagonian Coast,
Argentina. Quaternary Science Reviews 8:213-234.
Sala, J.M., Gonzalez, N. and M. Hernandez. 1977. Efectos de la barrera
hidraulica natural en las aguas subterraneas del literal de Bahia Samborombon.
Obra del Centenario del Museo de La Plata, t. IV, Geologia. La Plata, 153-166.
Schnack, E.J. 1985. Argentina. In: The World's Coastlines. E. Bird and M.
Schwartz, eds. Van Nostrand Reinhold Co., New York, 69-78.
SECYT (Secretaria de Ciencia y Tecnica). 1983. Programa de investigacion y
desarrollo en Pecursos Marines Costerns y lagunares de la Provincia de Buenos
Aires. Buenos Aires. 30 p.
Urish, D.W. and M.M. Ozbilgin. 1989. The coastal groundwater boundary.
Groundwater 27(3) :310-315.
384
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REGIONAL IMPLICATIONS OF RELATIVE SEA LEVEL RISE
AND GLOBAL CLIMATE CHANGE ALONG THE
MARINE BOUNDARIES OF VENEZUELA
RUBEN APARICIO-CASTRO
JULIAN CASTANEDA
Institute Oceanografico de Venezuela
Universidad de Oriente
Cumana-Sucre, Venezuela
MARTHA PERDOMO
Ministerio del Ambiente y de los
Recursos Naturales Renovables
Caracas 1010, Venezuela
ABSTRACT
Sea level data on the marine boundaries of Venezuela have been analyzed
using several tidal-gauge stations with continuous records ranging from 21 to 36
years. The rates of change in sea level have been highly variable. All of the
time series examined, except two, show a tendency toward increase in sea level,
with values ranging from 3.26 mm/year in Maracaibo Lake (an area of remarkable
petroleum and groundwater extraction during the last 50 years) to 0.91 mm/year
at Amuay. The easternmost tidal-gauge stations, located on Carupano and Puerto
Hierro, exhibit a lowering trend, which can be explained in terms of technically
induced uplift of this regional land mass due to its proximity to the boundary
between the Caribbean and the South American tectonic plates.
In an attempt to determine the Venezuelan coastal zone's vulnerability, this
paper indicates the lowland areas likely to be affected by this phenomenon and
discuss the resulting environmental, social, economical, and geopolitical
implications of these changes. Among other factors associated with global
climate change, the frequent occurrence of tropical storms and hurricanes in the
Caribbean Basin, and the changes in their track and destructive potential, emerge
as some of the most negative effects influencing the Venezuelan coastal zone in
the near future.
385
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Central and South America
INTRODUCTION
Global warming could disrupt environmental conditions and political
institutions throughout the world. In the recent past, the threat of a
greenhouse warming has been studied by the United Nations Environment Programme
(UNEP) through its Regional Seas Action Plans, in conjunction with the World
Meteorological Organization (WMO) and the Intergovernmental Oceanographic
Commission of UNESCO.
A 1988 UNEP study of the Wider Caribbean Region (including the Caribbean
Sea, the Gulf of Mexico, and the Florida-Bahamas area of the Atlantic Ocean)
emphasized the marine and coastal environment and addressed the implications of
climate changes in that region. That research served as a starting point to
initiate local scientific concern about anthropogenically induced global climate
changes in Venezuela.
This paper characterizes the Venezuelan coastal zone and summarizes its main
geodynamic and geomorphological features, its typical ecosystems, and its
socioeconomic importance. It presents some evidence of local variations in
climate conditions along the marine boundaries of Venezuela, examines the local
signal of relative mean sea level variability from tidal-gauge records, and
discusses the resultant environmental, social, geopolitical, legal, and economic
implications of the regional pattern of alterations in climate conditions.
Finally, it presents, for the consideration of Venezuelan authorities, a set of
recommendations of domestic importance toward implementing an effective national
response policy.
NATURAL CHARACTERISTICS OF THE VENEZUELAN COASTAL ZONE
Venezuela's coastline constitutes approximately 52% of the southern coastal
boundary of the Caribbean Sea and an appreciable portion of shoreline on the
Atlantic Ocean. Many types of coastal environmental stages are exposed along the
approximately 4,000 kilometers of the Venezuelan shoreline: sandy marshland,
beaches, cliffs, deltaic plans, coastal lagoons, barrier islands, estuaries, and
bays. These environments are distributed on both Venezuela's Caribbean Sea
boundary (2,720 kilometers) and its Atlantic Ocean border (1,300 kilometers).
In addition, its 200 nautical miles of Exclusive Economic Zone (EEZ), with an
area of 630,000 square kilometers, comprises around 300 islands, islets, and
keys.
While sandy shorelines and beaches appear frequently along the Caribbean Sea
border, sandy marshlands are confined to the Peninsula of the Paraguana at the
western section. The presence of cliffed coastal portions is clearly evident.
Deltaic zones are few, with the Orinoco Delta, on the Atlantic margin, emerging
as the most extensive one, occupying 88,000 square kilometers in its drainage
basin and 22,500 square kilometers in its receiving basin. The Unare Delta, in
the central section of the Caribbean boundary, with a drainage basin of 22,300
square kilometers and only 28 square kilometers of area in its receiving basin,
consists of two big coastal lagoons (Unare and Piritu) separated from the sea by
386
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Apan'cio-Castro, et a7.
very low-lying sandy barriers and partly protected by a mangrove forest of
limited extent.
Any general attempt to summarize a broad geodynamic characterization of the
Venezuelan coastal area should consider the following features:
• It lies on a very tectonically active zone. Located along the
country's easternmost coastal section is a significant proportion of
present-day global seismicity (see Figure 1).
• The local surface wind field presents a remarkable persistency in its
mean directional distribution, reflecting the regional predominance of
easterly winds and implying favorable conditions for coastal upwelling
throughout the whole year. However, with regard to the wind field's
strength, a notable westward intensification is evident, and
consequently, the local rate of evaporation on the western Venezuelan
coastline is enhanced.
• The seasonal fluctuation of the Intertropical Convergence Zone is
usually thought to be the most important factor controlling the local
rainfall pattern.
• The local tidal regime presents a microtidal mean range and gradual
westward increase of the form number, implying the occurrence of mixed,
mainly semidiurnal, tides at the easternmost section; mixed, mainly
diurnal tides at the central part; and diurnal tides at the westernmost
portion.
• Tropical cyclone activity has not been significant in the past.
Specifically, up to 1972, only three tropical storms occurring over the
southern coastal boundary of the Caribbean Sea had reached the category
of "hurricane" during the entire century.
• The coastline along the marine boundaries of Venezuela shows clear
signs of geomorphological changes. Table 1 shows the area of the
Venezuelan shoreline where coastline changes have been well documented
(see, for example, Bird, 1985).
VAST RESOURCES OF THE VENEZUELAN COASTAL ZONE
The socioeconomic and ecological importance of the Venezuelan coastal area
is well established.
Oil Resources
About 50% of the total population of Venezuela, estimated to be 20 million
people for 1990, resides in the coastal zone. Additionally, the oil industry,
which is the primary resource for national income, bases its operations on
structures located mainly on the coastal margin. In particular, these structures
387
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Central and South America
85°W
80'W
75'W
70" W
65°W
60°W
25'N
10'N -
- IO°N
65'W
BO'W
75'*
70'W
65'W
60'VI
Figure 1. Venezuelan marine territory in the Caribbean Sea.
are located on the westernmost portion. They include the estuarine system formed
by the Lake of Maracaibo, the connecting waterways of El Tablazo Bay, and the
Maracaibo Straits. Expansion of the national oil industry implies, in addition,
the establishment of macro-facilities on the easternmost section of the
Venezuelan coastal margin (Araya and Paria Peninsulas) during the next five
years.
Fishery Resources
The entire coastal zone of Venezuela possesses valuable fishery resources
that have the potential of continuous production if they are efficiently used.
The wind-induced coastal upwelling observed in the area is the key physical
mechanism responsible for the high biological production characterizing local
fishery activities.
The northeastern section of the country has been an important fishing area
for a wide variety of pelagic and demersal species. Specifically, the Gulf of
Cariaco, the western coast of the Araya Peninsula, and the southern and
388
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Aparicio-Castro, et al
Table 1. Venezuelan Coastline Changes
1. Orinoco Delta
2. Gulf of Paria
3. Western shore of the
Araya Peninsula
4. Coastal boundary of the
Unare Bay
5. Tucacas
6. Eastern shore of the
Medanus Isthmus
7. Falcon Province on the
Paraguana Peninsula
8. Mi tare Delta
9. Southern side of the
Guajira Peninsula
10. Western coast of the
Gulf of Venezuela
11. Swampy southern shore of
the landlocked embayment
of Lake Maracaibo
Progradational long-term trend
Encroaching of swampy shores at the north
Sea gaining
Erosion
Beach erosion
Extensive beach erosion
Active cliffing
Progradation
Active cliffing
General recession os sandy coastline
Progradation
CARIBBEAN SEA
389
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Central and South America
northeastern coasts of the Island of Margarita are zones of above-average sardine
fishing (Sardinella anchovia). The northwestern coastal portion, including the
Maracaibo estuarine system and the Gulf of Venezuela, has been the source of the
large increase in the total Venezuelan production of shrimp. Additionally, the
central and eastern areas of the Venezuelan coast present a set of marine
physical conditions favorable to surface catches of Atlantic skipjack and
yellowfin tuna. This has been extremely beneficial to the local economy during
the last five years.
Marine Ecosystems
Some of the most productive and biologically complex marine ecosystems in
the world, such as coral reefs, seagrass beds, and mangrove forests, are present
along the Venezuelan coastal zone (see Figure 2).
Coral reefs, consisting of the consolidated skeletons of corals, accumulate
rapidly in geological time and constitute the basis of many coastal fisheries.
They provide food, shelter, and nursery areas for commercially valuable fishes
and crustacean species. In addition, the reef forms breakwaters, which protect
harbors and bays, and limit coastal erosion.
Mangrove forests, a coastal feature of tropical regions, develop in low-
lying coastal areas where freshwater is supplied by rivers or terrestrial runoff.
The forests provide, through their prop roots, a surface to which marine
organisms can become attached. This, in turn, reduces tidal and wave energy.
I5°r
72
CARIBBEAN SEA
71°
70°
69°
68s
67
65« 66"
64"
1C. II I W U5 VJO VI OU UO UT 63 62 61
Figure 2. Spatial distribution of mangrove forests (•) and seagrass beds
along Venezuelan marine boundaries.
390
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Aparicio-Castro, et al.
Seagrass beds, which cover the bottoms of coastal bays, provide sediment
retention and stabilization processes that are very important for adjacent coral
reefs. The beds prevent the abrasion and burial of the reefs during conditions
involving high wave energy. Additionally, seagrasses serve as nurseries for the
juvenile populations of commercially important species, including fishes and
invertebrates (lobsters, conches, bivalves, etc.).
EVIDENCE OF CLIMATE CHANGE ALONG THE COASTAL AREA OF VENEZUELA
Evidence of long-term climate variations along the coastal margin of
Venezuela in recent decades has been reported by Aparicio (1988). The main
qualitative findings of that study, based on data records no older than 35 years,
are summarized in Table 2.
The pattern of variability in relative mean sea level along the Venezuelan
marine boundary, extracted from tidal-gauge stations, shows strong local tectonic
signals at the easternmost zone (see Table 3). In fact, signals given by sensors
located on Puerto Hierro and Carupano reflect a clearly tectonically induced
uplift of this local land mass, which can be explained in terms of the proximity
of this zone to the boundary between the Caribbean and the South American
tectonic plates. The global signals of sea level rise seem to be present along
the central part of the Venezuelan coastal margin, such as is evidenced by
examination of the records at Cumana and La Guaira. Another strong local signal
can be seen by examining sea level data from the Maracaibo tidal-gauge station.
A clearly anthropogenically induced local subsidence characterizes that signal,
due to petroleum/groundwater extraction activities in the area during the last
50 years.
IMPACTS OF GLOBAL CLIMATE CHANGE
The most obvious negative effect is submersion due to mean sea level rise
and loss of low-lying lands. The areas that seem to be particularly vulnerable
Table 2. Long-Term Temporal Variability of Climatological and Surface
Oceanographical Conditions Along the Marine Margin of Venezuela*
Parameters Long-term linear trend
Air Temperature Increase
Evaporation Increase
Precipitation No significant change
Zonal Wind Stress Decrease
Sea Surface Salinity Increase
"Based on data collected on land site coastal weather stations.
391
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Central and South America
Table 3. Relative nean Sea Level Variability Along the Venezuelan Coast Long-
Term Linear Trend
Station Record
Code Location Lat. Long. length
Linear
trend
(mm/year)
Standard
deviation
(mm/year)
1
2
3
4
5
6
Puerto Hierro 10°37'N 62°05'W
Carupano 10°40'N 63°15'W
Cumana
La Guaira
Amu ay
Maracaibo
10°28'N 64°12'W
10°28'N 66°56'W
11°45'N 70°13'W
10°41'N 71°35'W
1955-1963
1967-1987
1953-1976
1953-1989
1953-1985
1964-1989
-4.36
-2.12
1.92
2.24
0.91
3.26
3.26
1.07
0.59
0.41
0.61
0.61
CARIBBEAN SEA
are the most external portion of the Orinoco Delta, the easternmost area of the
Peninsula of Paria, and the region enclosing the small Unare Delta and the Unare
and Piritu lagoons, which constitutes, perhaps, the Venezuelan coastal area that
may have received the most negative influences from human activities in recent
years. Specifically, this region is experiencing (1) erosion, mainly induced by
deforestation and industrial and urban development, and (2) salinization of the
Piritu Lagoon, which is due, in part, to restriction of the freshwater supply
(gradual damming of the Unare River) and to uncontrolled use of chemicals in
certain agricultural processes.
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Aparicio-Castro, et al.
Saline intrusion in local groundwater resources is another negative effect
produced by sea level rise that will affect the Venezuelan coastal area --
specifically, those coastal aquifers located in the Peninsula of Paraguana
region, which, in turn, have been under indiscriminate exploitation during the
last 25 years. Surely, a sea level rise will worsen the actual water quality of
these aquifers, with negative consequences to local agricultural resources
(Alvarado, personal communication, 1989).
Coastal erosion of beaches will have a tremendous impact on national efforts
to develop the tourism industry. The most vulnerable areas seem to be Tucacas,
on the Falcon Province; beaches on the Mochima National Park, which is located
in the country's eastern coastal region; and Margarita Island, which has very
high economic activity along its margin.
A particular case to be considered concerns the geopolitical implications
for Venezuela derived from the reduction in area affecting Aves Island, which is
the only outcrop of the Aves Ridge above sea level into the Venezuelan Basin of
the Caribbean Sea. This island constitutes a large portion (about 135,000 square
kilometers) of Venezuelan marine territory (see Figure 3). A comparison of
geological surveys of Aves Island, which is only 3.7 meters above sea level at
its highest point, reveals that the island has been progressively reduced in size
during the last 30 years. Probably the factors responsible for this reduction
are mainly local erosional processes and the subsidence rate of the Aves Ridge
(Schubert and Laredo, 1984). Sea level rise in the Caribbean Sea, which has been
actually estimated to average approximately 4 mm/year (Maul and Hanson, 1988),
could exacerbate the present-day erosional instability of Aves Island with
unpredictable consequences for Venezuela from a legal point of view.
Caracas
VENEZUELA
Figure 3. Aves Island generates approximately 135,000 Km2 of marine territory
for Venezuela.
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Central and South America
Displacement of traditional fishing, sites, even on a relatively small
spatial scale, could emerge as a consequence of the alteration of the
thermohaline structure of the coastal marine surface layer along the Venezuelan
shoreline. This could harm local artisanal fisheries, with a negative effect on
domestic economies, especially those located along the eastern section of the
country.
Sea surface temperature (SST) in the Atlantic Ocean/Caribbean Basin is
supposed to increase in response to global warming of the lower atmosphere. As
a result, this part of the world would present, in the near future, better
thermal conditions for the genesis of hurricanes and tropical storms. A recent
work (Emanuel, 1987) reports that an increase in SST of 1.5°C would enhance the
potential maximum hurricane wind by about 8%. It also has been reported that
more frequent intensification of tropical systems to tropical storms could be
expected (Shapiro, 1988). As has been mentioned previously, the Venezuelan
marine margin has been out of the standard track of hurricanes during this
century. However, two recent facts related to cyclonic activity in the Caribbean
region deserve special consideration: (1) the strongest recorded hurricane of
this century, Hurricane Gilbert, beat the Caribbean Sea in 1988, and (2) a
hurricane (Hurricane Joan) hit the Venezuelan coastal territory for the first
time during this century in 1989 (see Figure 4). Changes induced by global
climate variations in the location of the geographical area favorable to the
genesis of hurricanes and tropical storms on the tropical Atlantic Ocean are,
then, of crucial importance for Venezuela.
RESPONSE POLICY
Despite the efforts of the local scientific community, the need to adopt
strategies to manage the impact of global climate changes on the Venezuelan
coastal geography has not yet been clearly understood by national authorities.
This seems to be a logical consequence of the considerable uncertainty
characterizing technical reports regarding the magnitude of future alterations
of global lower atmospheric and surface marine conditions typifying regional
climate.
Actually, Venezuelan scientists involved in this problem face the task of
motivating official decision-making agencies. In this sense, the international
pressure placed on the Venezuelan government, which has been recently invited to
subscribe to global agreements related to the matter (The Montreal Protocol, The
Hague Declaration), has been considerably beneficial.
Arrangements are being made to form a local technical committee that would
have as its primary task the preparation of a government response to the
implications of global climate changes on Venezuela's geography. In this sense,
local official agencies dealing with environmental policy, and Venezuelan
scientists related to the earth sciences, are being encouraged to initiate a work
platform on the basis of collective action and shared efforts.
394
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Aparicio-Castro, et a7.
45'
40'
Figure 4. Track of the most destructive hurricanes affecting the greater
Caribbean Sea region during 1988 and 1989.
This committee will be sponsored by the Ministerio del Ambiente y de los
Recursos Naturales Renovable (MARNR), which is the national agency responsible
for environmental policy in Venezuela. The following specific objectives are to
be addressed by that committee in the immediate future:
• Coordinate national activities related to research and monitoring of
meteorological and oceanographic surface conditions among all regional
institutions charged with the responsibility of studying climate
variability and its local impact.
• Expand the actual tidal-gauge network operating on the Venezuelan
coastal boundary, taking advantage of our participation in the Global
Observer System (GLOSS).
• Evaluate the feasibility of establishing onshore and offshore
structures on critical coastal areas facing high risks due to sea level
increases.
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Central and South America
• Coordinate a long-term policy for reducing and reversing the ongoing
deforestation of Venezuelan territory.
• Establish public education plans to promote better understanding of the
topic of climate change and to assess its potential impacts on society.
• Motivate regional scientific centers related to environmental research
to establish studies that will address and identify the degree of
vulnerability of particular geographical areas to specific
climatological anomalies.
• Stimulate research on alternate, nonconventional energy sources as part
of a long-term policy devoted to reducing the use of fossil fuels,
combined with more efficient use of energy, over the next few decades.
• Organize the Venezuelan contributions to global research programs about
climatic changes and their implications, such as the World Ocean
Circulation Experiment, Tropical Ocean Global Atmosphere Programs and
the International Geosphere/Biosphere Program.
CONCLUSION
In view of the clear evidence that climatological anomalies on the coastal
area of Venezuela have the potential to induce serious social, economical, and
ecological implications, the Venezuelan government should consider this topic to
be a matter of urgency. The need to compile inventories of natural coastal
resources and existing environmental information must receive first priority, so
that a worst-case climatological scenario can be developed for the country. This
could provide an impact analysis that would facilitate the early implementation
of an effective national policy.
ACKNOWLEDGMENTS
Without the cooperation of the following members of the Venezuelan
scientific community, it would not have been possible to produce this report.
Beatriz Vera (Universidad Central de Venezuela), Carlos Carmona (Universidad
Nacional Experimental Francisco de Miranda), Jorge Alvarado (Ministerio del
Ambiente y de los Recursos Naturales Renovables), Teniente Mario Capaldo
(Direccion de Hidrografia y Navegacion), and Jose Luis Naveira (FUNDAOCEANO).
Also highly appreciated are data records provided by the Venezuelan Air
Forces, Venezuelan Navy, and MARNR.
396
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Aparido -Castro, et a7.
BIBLIOGRAPHY
Aparicio, R. 1988. Some meteorological and oceanographic conditions along the
southern coastal boundary of the Caribbean Sea (1951-1986). In: UNEP(OCA)/CAR
WG.l Report Implications of Climate Changes in the Wider Caribbean Region (in
press).
Bird, E.C. 1985. Coastline Changes. A Global Review. New York: John Wiley
& Sons.
Emanuel, K.A. 1987. The dependence of hurricane intensity on climate. Nature
326(2):483-85.
Maul, G.A., and K. Hanson. 1988. Sea level variability in the intraamerican sea
with concentration on Key West as a regional example. In: UNEP(OCA)/CAR WG.l
Report Implications of Climate Changes in the Wider Caribbean Region (in press).
Schubert, C., and M. Laredo. 1984. Geology of Aves Island (Venezuela) and
subsidence of Aves Ridge, Caribbean Sea. Marine Geology 59:305-18.
Shapiro, L.J. 1988. Impact of climate change on hurricanes. In: UNEP(OCA)/CAR
WG.l Report Implications of Climate Changes in the Wider Caribbean Region (in
press).
397
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IMPACTS OF AND RESPONSES TO SEA LEVEL RISE IN CHILE
BELISARIO ANDRADE
CONSUELO CASTRO
Institute de Geografia
Pontificia Universidad Catolica
Santiago, Chile
INTRODUCTION
The latitudinal extent of Chile's Pacific coastline offers a wide variety
of geomorphological and oceanographic situations. The coast extends from 18° to
56° south, roughly equivalent to the latitudinal difference between Mexico's
border with Guatemala and the Alaskan/Canadian border. If the indentation of the
coast is taken into consideration, as well as the perimeter of numerous islands
situated in the fiords region, the length of Chile's coastline is greater than
25,000 km. Figure 1 shows the variation of Chile's coast.
CHARACTERIZATION
Natural Features
Coastal Climatology
The Chilean coast is under the influence of tropical, subtropical, and
temperate climates of western continental margins. The ocean has an important
moderating influence upon the temperatures. As Fuenzalida (1971) points out, the
temperatures between 20° S and 30° S are 2.8°C colder than the latitudes would
suggest; between 50° S and 60° S they are 4.6°C warmer. Therefore, despite
having a difference of almost 37 degrees of latitude, the difference of the mean
temperature is only 12.8°C. By contrast, there is a marked difference in the
total amount of precipitation. In Arica at 18°28' S, the total amount is 1.1 mm;
on the other hand, in San Pedro at 47°43' S, the total annual amount is 4,076.1
mm (Figure 2).
Tides and Waves
Tides in Chile are generally mixed-semidiurnal; that is, two high waters and
two low waters during a tidal day, with a diurnal difference.
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Central and South America
B
Figure 1A-B. Chile's 25,000-km coast varies considerably.
48'S) -- artificial foredune; and (B) Longotoma (32° 22'S) -
400
(A) Ritoque (32°
- sandy coastline.
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Andrade and Castro
Figure 1C-D. (C) Papudo (32° 30'S) - storm surge effect. Beach is now
replenished with dune sediments. (D) Punta Con Con (32° 55'S) -- Rocky coast,
high terraces, with old stabilized dunes. By human interference, these dunes
nave oeen reactivated.
401
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ARICA
Ut. 18 SB'S Long. 70 20' W
altitude 6 mta.
LA SERENA
Ut 29 64'S Long. 71 16'W
altitude 32 mta.
•fc«*.ICI r^dp. (*»!.„
«l
sot
36
< ^ ^-\
16f
tOf
6i
^vw
360
300
36O
3OO
160
100
60
JA80NOJFMAMJ
TEMP ^3 PRECP.
.Itov. 1C!
Pnoo. Imml.
JAflONDJFUAUJ
— TEMP. ^ PRECP
VALPARAISO
Lat. 33 OVS Long. 71 38'W
altitude 41 mta.
inwni
TEMP. E2PBECI>
o
ro
CONSTITUCION
Ut. 36 20'S Long. 72 26*W
altltud* 2 mta.
invnl
VALDJVIA
Ut. 39 48'S Long. 73 14'W
aJtituda 6 mta.
PUERTO AISEN
UL 45 24'S Long. 72 42*W
ahltud* 10 mta.
CABO SAN ISIDRO
Lat. 53 47-S Long. 70 68'W
altitude 20 mta.
JA8ONOJFMAMJ
40
30
16
16
10
ei
Prvoix I
4OO
360
300
360
200
160
100
60
40
36
30
36
30
16
10
6
A3ONOJFMAMJ
JA8OHDJFMAMJ
JA8ONOJFMAMJ
40O
360
300
360
30O
16O
100
60
0
•TEMP.
iPRECIP.
TEMP.
PRECT.
- TEMP.
PREQP.
TEMP.
Figure 2. Chilean coastal climatic types. Note the great pluviometric contrast and thermic homogeneity.
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Andrade and Castro
The tidal ranges vary. Between 18° and 41° S latitude, the maximum
amplitude is between 1.5 and 1.9 m, respectively. Within the fiords region to
the south, especially between the Gulfs of Ancud and Corcovado, tides are 5 to
8 m because of a resonance effect. South of this sector, down to Punta Arenas
at 52° S, the amplitudes vary between 1.8 and 2.5 m. There is a great contrast
between the west and east entrances of the Straight of Magellan. At Punta
Dungeness, the easternmost point, the amplitude reaches 10 m, while at the
western entrance of the straight the amplitude is only about 2 meters. At the
Tierra del Fuego islands to Cape Horn, the range is between 1.5 and 3 meters.
The information about waves on the coast, especially that collected with
instruments, is scarce. Data exist primarily for the central area of the
country, where there seems to be good correlation between wind patterns and wave
patterns (see Appendix 1: Waves of Chile).
Surges
Storm surges occur occasionally on the Chilean coast; these are caused by
large and intense atmospheric perturbances in the South Pacific, known as
"Bravezas" in Chile. According to Paskoff (1970), they progress along the
coastline from south to north in the form of great waves, many meters above the
usual height reached by the storm waves, and linger 24 to 48 hours1 (see
Appendix 1).
Tsunamis
Since 1652, over 30 tsunamis have been recorded on the Chilean coast
(I.H.A., 1982). With an expected 1-m rise, surges will increase their
penetration inland. Generated by earthquakes and submarine movement, these have
devastating effects. As an example, on 13 August 1868, the tsunami that affected
the Port of Arica dragged the North American ship Wateree for more than 2 miles
from its anchoring ground and finally deposited it 400 m inland over the coastal
dunes.
'This author's description of the morphologic effects and the wave levels
reached during an event that occurred in 1968, which affected a coastal sector
of approximately 2,500 km between Arica and Talcahuano, coincides with one
presented by Araya-Vergara (1979). In 1968, a number of roads located more than
5 m above sea level were destroyed by waves, as were hotels, houses, and
restaurants, which had foundations 5-7 m above sea level. In general, all points
near the coastline situated at the holocene level "La Vega" (1-2 m) were affected
by the "Bravezas," and various points situated above the Pleistocene level
"Cachagua" (5-7 m) were also affected (for example, the airstrip of the naval
aviation base at Quintero). The foredunes of various beaches of central Chile
were eroded. The effects produced by these spasmodic phenomena, not very
frequent, are long lasting and much more notorious than the effects of continuous
wave action related to the usual storms occurring over several years.
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Central and South America
Coastal Geomorpholoqy
The Chilean coast between 18° S and 41° S is dominated by marine processes,
acting under hyperarid, semiarid, Mediterranean, and oceanic temperate climates,
with rocky coasts and pocket beaches dominating. To the south of this sector,
oceanic temperate climate dominates, with domination by marine processes along
the open coast to the west and fluvial domination in the inland fiords (Figure
3) (Appendix 2 provides more detail).
Neotectonics
A particular characteristic of the Chilean coastline is its great vertical
mobility, the result of its location in a plate convergence zone. Because of
this, strong movements of uplifting and sinking occur with magnitudes that
surpass those expected from a sea level rise induced by the greenhouse effect.
For more than a century, the data of various authors have shown that the
magnitude of the vertical movements can frequently exceed 150 cm (Meneses Toro,
1897; Vidal Gormaz, 1901; Saint Amand, 1963; Pflaker and Savage, 1970; Fuenzalida
and Harambour, 1984; Gonzalez, 1985).
It cannot be clearly distinguished whether the tendency is toward downfall
or uplifting, because in some latitudes the coast has moved in both directions.
However, there seems to be a slight predominance of uplifting north of 39° S and
sinking south of this latitude.
The most recent movements have been determined by I.G.M. (1985), who found
a mean uplift of 33 cm in the coastal sector of San Antonio-Algarrobo
(33°20'-33°30' S) due to the earthquake of March 3, 1985. Barrientos et al.
(1981), using the tide gauge of Puerto Montt (41° S), indicated an uplifting of
the region of about 4.7 cm/year between 1964 and 1973, diminishing to 2.4 cm/year
between 1980 and 1985; this same site sank 200 cm during the May 1960 earthquake.
Cities and Population
The population of Chile is approximately 12.5 million, 80% of which is urban
and mainly concentrated in Santiago. The urban coastal population represents 21%
of the total population, and a large part of it resides in urban areas of more
than 100,000 inhabitants. The regions of Valparaiso and Bio-Bio together contain
55.35% of the total urban coastal population of the country.
The main coastal cities are located on coastal stepped plains separated by
dead coastal cliffs. At first, the cities were located over the low (between 5
and 20 m) and narrow marine terraces but later they grew toward the higher
terraces (Figure 4).
The main tourist centers are the sandy coasts of Coquimbo Bay (29° S) and
the central coast (33°30' S). The bathing resorts extend over coastal dunes,
including the foredune. Protection structures for wave action are infrequent,
except in places where adequate structures for ports have been built, e.g.,
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Andrade and Castro
»'', •', •.] Older resistant
• '-.'•'•I Low resistant
• • '• • *
•.-'•i*-I 13/ociol ond glacial fluvial
.^ * | High relief - cliffed
t^jL_A. I Low relief - cliffed
Figure 3. Coastal landform types.
405
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Central and South America
WUIOUE(200 12' SJ I
#*
ANTOFAGftSTA ( 23° 39' SJ
LA SERENA (29° 54' SJ
VflLPARAISO (33°02'SJ
PUERTO MONTT
(4I°29'S.)
PUNTA ARENAS (S°IO'SJ
Figure 4. Some Chilean cities located over marine terraces.
406
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Andrade and Castro
docks, marinas. With a sea level rise of about 1-2 m, these bathing resorts will
be only somewhat affected.
Economic Aspects
The National Accounts give an idea of the relative importance of some
economic activities held in the coastal zone. The Gross Domestic Product was
$18.5 billion (U.S. dollars). Tourism (primarily coastal, but incorporating
activity from all over the country) accounted for 0.94% of this total, and
fishing accounted for 0.88%.
IMPACTS OF SEA LEVEL RISE
The existing coastal national maps of Chile do not permit a quantitative
evaluation of the area affected by a sea level rise of 20 and 200 cm, given that
maps have contour intervals of 25 m or greater.
The Rocky Coastline
Considering the steepness of the rocky coast along its 30,000 km, a sea
level rise of 20 cm will not have any noticeable effect. A 50- to 100-cm sea
level rise would probably affect scarce coastal tourist installations, but only
during storms.
A rise of 200 cm would produce effects on harbor structures, requiring their
redevelopment, as happened in the tectonic sinking of 1960. A sea level rise of
100 to 200 cm would accelerate the recess of cliffs in soft rocks (sandstone) of
the central zone of Chile affecting populated centers, essentially tourist
centers.
South of 41° S, the attacking of the cliffs created in soft glacial outwash,
will affect a great number of populated centers of the eastern coast of Chiloe.
Coastal protection works would be necessary in this sector. We estimate that
over 60 km of seawall will be necessary to shelter the threatened areas.
The Sandy Coastline
Although they constitute only 2.1% of the total coast, sandy shorelines
support important economic activities (tourist and industrial as well as
residential). All the pocket beaches are located in front of cliffy landscapes,
so they cannot migrate inland in the eventual case of a sea level rise.
A sea level rise of 50 cm or more will substantially diminish the area of
pocket beaches. A rise of 2 meters would eliminate them completely.
The sandy shorelines associated with dune fields have an important sediment
supply from the rivers and enough space to shift inland. In this case, a sea
level rise of 50 cm or more will affect the foredune, making it retreat inland.
Important industrial facilities would be affected, particularly those at Quintero
407
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Central and South America
Bay (32°46' S), San Antonio (33°33' S), Constitucion (35°18' S), and Talcahuano
(36°42' S). Approximately two-thirds of all the coastal bathing resorts would
be partially inundated.
RESPONSES
Institutions and Agencies Associated With the Coastal Zone
The national administrative organizations related to the coastal zone are
within three independent ministries:
1. Ministry of National Defense, Marine Subsecretary, which consists of
a. General Office of the Marine Territory and Merchant Marine. This
organization has the control and monetary responsibility for the
entire coast, territorial sea, and exclusive economic zone of the
Republic. Its inland jurisdiction extends 80 m inland, starting
at the limit of the spring high tide line. The essential mechanism
for control of the coastal area lies with the members of this
office, who permit the particular use in any form of beaches, beach
lots, the sea floor, portions of water, and rocks within and/or out
of the bays. The agency also has responsibility for issuing
permits for extraction of sediments and landfill for coastal
engineering.
b. Navy Hydrographical Institute. This agency is in charge of all
studies and preparation of documents for navigational aid, such as
tide tables, marine navigational charts, and navigational tracks.
It is also in charge of meteorological forecasting and doing basic
research in oceanic and coastal physical oceanography. It is a
member of the International Tsumani Alarm System of the Pacific.
2. Ministry of Public Works, Harbor Works Office. This agency is in
charge of the design, calculation, and studies of harbor works, and
conducts research in coastal oceanography.
3. Ministry of Economy, National Fishery Service. Administers the fishery
sector, promotes and coordinates investigation in this domain. This
office is in charge of the methods and installations of aquaculture,
fishing quotas, and extraction of live products from the littoral zone.
The previously named institutions, together with other institutions from a
group of Chilean universities, form the CONA or "Comite Oceanografico Nacional"
(National Oceanographic Committee).
The CONA has prepared a National Oceanographic Plan for the period 1987-97,
which is based on a four-year survey of national institutions concerned with
408
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Andrade and Castro
oceanic scientific technological work. Five research programs are proposed to
investigate the structure and interrelationships of ecosystems within Chilean
seas.
Agency Perceptions About Greenhouse-Induced Sea Level Rise
Conversations held with members of some of the relevant agencies suggest
that a sea level rise of 20-50 cm is not perceived as a problem. Because there
is a lack of awareness concerning a greenhouse effect-induced sea level rise, no
one is planning a response to it. Local planners are more concerned about
solving current problems; nevertheless, they indicate that when it becomes
necessary to protect small fishery facilities or installations in contact with
the beach, they will support solutions based on seawall tetrapods.
Also, due to the effects of strong winter storms, some tourist beaches have
been nourished with sand. The filling is done with sediments extracted from
inland deposits. In some cases, the foredune has been elevated using mechanical
and vegetational methods. This is done because of dune management and not as a
response to a marine erosion.
Frequently, local planners have been forced to respond to tectonic sea level
rising, but this is not predictable and for this reason they do not consider a
slow sea level rise of 20 to 50 cm over many years to be an emergency.
Chilean government agencies will be able, from a technological point of
view, to apply protective actions in critical areas when the problem is
adequately evaluated.
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Central and South America
APPENDIX 1: WAVES OF CHILE
The reports that give the most adequate synthetic view are those of
Araya-Vergara (1971, 1979); both are on central Chile. The information provided
by Davies (1980) based on the works of Holcombe (1958) and Meisburger (1962)
gives a very useful integrated view.
Holcombe (1958) concluded that in the Southern Hemisphere, the mean latitude
of the zone of maximum value of gale force winds oscillates only between 54° S
and 56° S during the winter-summer period. Because of this persistence of high-
frequency gale-force winds and the length of the fetch, the southern storm belt
is the most evident and important wave-generating area in the world and produces
a high proportion of the world's ocean swell (Davies, 1980).
The path followed by the swell generated at latitude 55° S in front of the
Chilean coast produces wave trains with a west and southwest component from 41°
S toward the north. This pattern of waves makes the coast of Patagonia the most
attacked by storm waves during the year.
With the data compiled by Meisburger (1962), Davies presents various
synthesis charts in which it is possible to appreciate that for the Chilean
coasts the frequency of occurrence, in at least half the year, of waves of 2! m
or higher is as follows:
South Latitude %
38° - 56° > 40
38° - 30° 30 - 40
30° - 25° 20 - 30
25° - 18° 10 - 20
The greatest height reached by waves occurring with a frequency of 3% or
greater in at least half the year is as follows:
South Latitude Height (m)
56° - 45° > 6.0
45° - 40° .6.0 - 5.0
40° - 22° 5.0 - 3.7
22° - 18° 3.7 - 2.2
In a more detailed scale, Araya-Vergara (1971) shows the wave
characteristics in Chile, according to the works of D.O.P.-Tudor Eng. Co. (1965),
as well as the unedited reports of the Laboratoire Central d'Hydraulique de
France, for Constitucion (35°18' S) and San Antonio (33°35' S). The results of
his analysis indicate that the origin of the most frequent waves is from the
southwest, which coincides with the prevailing winds.
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Andrade and Castro
In Arica in December 1975 and July 1977, with a total of over 3,396 waves
recorded, the mean period during the summer had a value of 12 seconds and a
significant height of 1.15 m; during winter the mean period was 9 seconds and the
significant height was 1.3 m.
In Iquique there are only data for the month of June 1987. Using 1,336
waves, the mean period was 11.02 seconds with a significance height of 1.08 m.
The wave data are scarce and discontinuous. They refer only to a sector
of the coast dominated by the southern west coast swell environment.
There are no automatic wave records situated along the coast dominated by
the southern storm wave environment, especially south of 41° S.
Important differences between the coast facing directly the open Pacific
and those of the interior waters of the fiord coast probably exist.
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Central and South America
APPENDIX 2: GEONORPHOLOGY OF CHILE
Distribution of Cliffed Coasts
According to Araya-Vergara (1982), the length of the cliffed and rocky
coastline is 33,711 km; 700 km of the northern region of Chile correspond to the
mega-cliff described by Paskoff (1978), along which can be distinguished four
sections. The first section, between 18°28' S and 20°13' S, is an active cliff
with unevenness between 400 and 1,000 m; a second section between 20°13' S and
21°24' S is a dead cliff behind a terrace 2 to 3 km wide; a third section
between 21°24' S and 23°28' S, with unevenness between 500 and 1,200 m, is also
a dead cliff with a terrace in front, composed of marine Miocene deposits,
sculpted by the sea; the fourth section, which reaches 25°22' S, presents active
and dead sectors, with mean heights of 500 m, but in some places it can reach an
altitude of 2,000 m. This is a major feature of the north coast of Chile. In
general, in this sector hard rocks appear on the surface, giving a stable
appearance.
South of 25° to 33°44'S there are predominantly cliffs and bluffs in
essentially igneous formations. Another section also with predominance of cliffs
but in tertiary soft sedimentary rocks as well, is developed to 36°30'S. From
this sector to 43°30'S are hard cliffs sculpted in micha-schists alternating with
soft tertiary sandstone. It is also possible to distinguish an internal sector
between 41° S and 43° S with soft cliffs sculpted essentially in glacial outwash,
but in sheltered environments. From 43° S to 56° S, hard rock cliffs and bluffs
dominate with some morainic intercalations.
Distribution of Low Unconsolidated Coasts
The lower coasts, including the deltas, constitute 2.1% of the total;
according to Araya-Vergara (1982) they add up to 580 km. They are discontinuous
and concentrated in groups related with the existence of fluvial sedimentary
sources and with a minor association, to soft sedimentary rocks at the shoreline.
The main groups of beaches which can be distinguished are the following:
29° S - 30° S Coquimbo - La Serena
32° S - 33° S Longotoma - Concon
33° S - 37° S Chile Central
38° S - 43° S Arauco - Chiloe
In general they are in dynamic equilibrium, with not much evidence of
retreat or advance in the long range. However, Andrade (1985) has found evidence
of recession in the Chiloe coast, in the internal sector. It may be explained
by a relative sea level rise due to recent subsidence movements and applications
of the Bruun rule.
Most of the constructed coasts correspond to beach ridges, composed of
sand. In the interior coast of Chile spits and hooks are very frequent, formed
by sand and gravel that the sea extracts from the cliffs sculpted in glacial
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Andrade and Castro
outwash. At Tierra del Fuego it is common to find beaches supplied by morainic
deposits.
A great number of beaches along Chile correspond to pocket beaches, which
are located over rocky platforms between resistant rocky promontories. Although
data are scarce, our observations from fieldwork in central Chile indicate that
they have a general thickness less than 4 m at the backshore.
A frequent phenomenon in central Chile is the development of coastal dunes,
associated with beaches which are generally located north of the river inlets.
This ensures a good sedimentary supply because of the longshore drift generated
by waves mainly from the southwest, which coincides with the prevailing winds and
which also transports the sand inland.
The principal coastal dunes are located between 29° S and 42° S. They
cover approximately 131,000 hectares, according to the inventory made by
IREN-CORFO (1966). Most of the modern active dunes are located between 33° S and
38° S according to Castro (1985).
Castro (1985) provided a synthesis of the different morphologic elements
found in the coastal dunes, distinguishing:
a) The foredune.
Located in contact with the backshore forming a parallel band to the beach,
its width is variable between 50 to 200 m; the average height is 5 m. There is
a close association between the morphologic aspect of the dune and the vegetation
found on it. Thus in central Chile, the foredune is composed of a group of
hummocky dunes, elongated in the direction of the wind, with a pointed tail to
leeward. They are separated by deflation corridors. There are obstacle dunes
produced by the capture of sand by vegetation . The most frequent species is
Ambrosia chamissonis, which possesses a radicular system which develops to great
depth; it is an accidentally introduced species from California (Kohler, 1970),
which apparently is substituting for the native species Carpobrotus chilensis,
which helps form lower dune hummocks.
The Chilean foredune does not have the aspect of a continuous wall as in
North America or the northwest coast of Europe, colonized by Ammophila arenaria,
but has aspects of a nebkha field. In some places where dune control has been
applied with Ammophila arenaria, the foredune gives a massive appearance as in
the case of Chanco (35° S).
b) Interdune depression.
A depression separates the foredune from the moving sand ridges of the
interior. It has a variable width; its major axis is parallel to the beach,
frequently comprising an active deflation area and sand transportation area. But
on occasions, it may be occupied by a coastal lagoon or a marsh. In this sector
the water table is very close to the surface, so it has vegetation adapted to
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Central and South America
these conditions such as Scirpus nodosus. The depression may also develop by the
deflation of old coastal ridges.
c) Moving sand ridges.
These occupy the greatest area within the dune field. They have a variety
of forms, in which we can distinguish some individuals, such as barkhans. The
coalescence of barkhans leads to transverse dunes which are organized as waves
moving to the interior many hundreds of meters, invading agricultural lands and
villages. They do not have vegetation cover.
d) Stabilized dunes.
Frequently in contact with active dune fields are various generations of
dunes stabilized by natural vegetation. A variety of this group are the
longitudinal dunes, which appear within this axis in the same direction as the
prevailing wind. They present associations of Puva chilensis and Cereus sp.
Other morphological types are the undulated dunes. Their vegetational
layer is composed by low gramineous and bushes such as Baccharis concava.
Both of the described stabilized dune forms are dated as Holocene (Paskoff,
1970; Caviedes, 1972). Holocene dune reactivation can be verified in many places
starting as blowouts, evolving on occasion as parabolic dunes. The origin of the
reactivation is normally because of human interference.
A third variety of stabilized dunes corresponds to hills which are smoothly
undulating and which have not lost totally their original form due to natural and
anthropic causes. Paskoff (1970) assigns them a Pleistocene age. They may be
covered by mesomorphic scrub bush more or less dense.
A sea level rise of 1 m could affect rapidly the foredune, but the Holocene
dunes would not be affected immediately.
Distribution of Aquatic Features
Wetlands
Although there has been no inventory of wetlands in the country, or
estimates as to the dimension or nationwide distribution of wetlands, a few
reports give us a general idea of their morphology and their floristic
composition.
Geomorphologically, Andrade (1985) described some tidal marshes on the Gulf
of Ancud showing morphological patterns similar to those of the temperate zone
of the Northern Hemisphere. In this study area they show evidence of erosion by
the sea due to a technically induced sea level rise caused by crustal
subsidence.
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Andrade and Castro
In relation to their requirements of low wave energy and great tidal range,
they tend to develop better between 40° and 43° S in protected positions in
estuaries or behind sand barriers. In the botanic studies done by Ramirez et al.
(1988), Schwaar (1978), and Reiche (1934), some of the halophytes described are
Triqlochin maritimun. Cotula coronopifolia. Eleocharis melanostachvs. Selliera
radicans. Spartina densiflora. and Salicornia sp. In general, the tidal marshes
develop adjacent to a cliffed landscape in the Gulf of Ancud. A rapid sea level
rise would probably endanger the permanency of these intertidal ecosystems, since
in many cases they do not have space to migrate upslope because they are bounded
by bluff coasts.
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APPENDIX 3: AVAILABLE CARTOGRAPHIC AND
AERIAL PHOTOGRAPHIC DATA
The actually available cartographic documents are produced and distributed
by two agencies of the Ministry of Defense: the Institute Geografico Militar
(IGM) and the Institute Hidrografico de la Armada (IHA). The first agency
produces topographic charts, and the second agency produces navigational charts.
The IGM charts exist in various scales and projections, and cover the
country partially according to the scale:
Scale
1:500,000
1:250,000
1:100,000
1:50,000
1:25,000
Coastal Sector
18° S
18° S
53° S
55° S
18° S
18° S
30° S
31° S
37° S
40° S
56° S
27° S
27° S
47° S
Contour Interval
Form Curve
250 m
250 m
250 m
50 & 100 m
25 & 50 m
25 & 50 m
25 & 50 m
25 & 50 m
25 & 50 m
The IHA navigational charts include only bathymetric data in meters. They,
as well as the IGM charts, cover the country partially. Due to its specific
purpose, there is a greater scale variety; therefore we will only indicate the
number of charts for each scale.
Scale
3,000,000
2,000,000
1,000,000
500,000
260,000
250,000
200,000
165,000
150,000
130,000
125,000
100,000
80,000
75,000
70,000
65,000
60,000
50,000
No. of Charts
2
2
2
10
1
2
16
1
8
1
1
13
2
1
3
1
5
20
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
45,000
40,000
35,000
32,000
30,000
25,000
24,000
20,000
16,000
15,000
12,500
12,000
10,000
8,000
7,500
6,000
5,000
4,000
2,000
No. of Charts
2
35
5
4
40
19
1
72
2
53
1
5
94
20
1
5
20
3
2
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Andrade and Castro
There are various vertical aerial photo missions. The Photogrametric
Service of the Air Force (SAP) is officially in charge of producing this type of
document. However, many other missions produced by other agencies in the past
are available.
Year
1942-45
1955
1961
1961
1974-75
1978-80
1978-80
Approx. Scale
1
1
1
1
1
1
1
30,000
70,000
20,000
50,000
55,000
30,000
60,000
Latitude
17°30'- 37°10'S
37°- 38°20'S
37°- 43°30'
32°15 - 34°
43°30 - 51°
33° - 41°S
18° - 56°S
Agency
USAF
HYCON
HYCON
OEA
SUSAF
SAF
SAF
On occasion, other charts and aerial photographs, which were produced for
specific uses, can be obtained through public and private organizations. These
documents are not standard issues; therefore, there are no general indices for
them.
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Central and South America
BIBLIOGRAPHY
Andrade, B. 1985. Estudio morfosedimentologico de marismas del Golfo de Ancud,
Chile. Revista de Geografia Norte Grande 12:27-33.
Araya-Vergara, J.F. 1971. Determinacion preliminar del las caractersticas del
oleaje en Chile central. Not Mens. Museo Nac. Hist. Nat. Santiago, Chile
Araya-Vergara, J.F. 1972. Bases geomorfologicas para una division de las costas
de Chile. Informaciones Geograficas 22:5-36.
Araya-Vergara, J.F. 1976. Reconocimiento de tipos e individuos geomorfologicos
regionales de la costa de Chile. Informaciones Geograficas 26:9-30.
Araya-Vergara, J.F. 1979. Las incidencias cataclismaticas de la bravezas en la
evolucion de la costa de Chile. Informaciones Geograficas 26:19-42.
Araya-Vergara, J.F. 1982, Analisis de la localizacion de los procesos y formas
predominantes de la linea literal de Chile: Observacion Preliminar.
Informaciones Geograficas 29:35-55.
Barrientos, S., S.N. Ward, and E. Lorca. 1981. El terremoto de 1960 en el sur
de Chile y sus deformaciones cuasi-permanentes. Comunicaciones 39:158.
Canon, J.R., and E. Morales. 1985. Geografia del Mar Chileno. Colecion
Geografia de Chile. Santiago, Chile: I.G.M. Vol. IX., 244 p.
Castro, C. 1985. Resena del estado actual de conocimiento de las dunas
litorales en Chile. Rev. de Geografia de Chile Terra Austral is 28:12-32.
Castro, C. 1988. The Artificial Construction of foredunes and the interference
of dune-beach interaction. Journal of Coastal Research (Special Issue No. 3).
Caviedes, C. 1972. Geomorfologia del cuaternario del Valle del Aconcagua. Chile
Central. Cuad. Geogr. Friburg No. 11.
Davies, J.L. 1964. A morphogenic approach to world shorelines. Zeit. fur
Geomorph. 8:127-142.
Davies, J.L. 1980. Geographical variation in coastal development.
Geomorphology Texts No. 4. London: Longman. 212 p.
D.N.H.A. 1961. El maremoto del 22 de Mayo de 1960 en las costas de Chile.
Publicacion No. 3012. Valparaiso, Chile: Departmento de Navegacion e Hidrografia
de la Armada. 129 p.
Fuenzalida, R., and S. Harambour. 1984. Evidencias de subsidencia y
solevatamiento en la peninsula de Brunswick, Magallanes. Comunicaciones No. 34.
Sanitago, Chile: Universidad De Chile, p. 117-120.
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Fuenzalida-Ponce, H. 1971. Climatlogia de Chile. Santiago, Chile: Universidad
de Chile, Departmento de Geofisica y Geodesia. Publication Interna de la Seccion
Meteorologia. 73 p.i
Gonzalez, O.M. 1985. Mapa neotectonico preliminar de America del Sur. Ceresis.
Santiago, Chile: I.G.M.
Holcombe. 1958. Similarities and contrasts between the Arctic and the Antarctic
marine climates. In Polar Atmosphere Symposium. Parti. Metheorology. London:
I.G.M. 1985. El terremoto del 3 de Marzo de 1985 y los desplazamientos de la
corteza terrestre. Rev. Geog. de Chile Terra Austral is 28:7-12.
Inman, D.L., and C.E. Nordstrom. 1971. On the tectonic and morphogenic
classification of coasts. Journal of Geology 79:1-21.
I.H.A. 1982. Institute Hidrografico de la Armada. Maremotos en la costa de
Chile. Publicacion 3016. Valparaiso, Chile: I.H.A. 48 p.
IREN-CORFO. 1966. Inventario de dunas en Chile (29° 48' - 41° 50' Lat. sur).
Publicacion No. 4. Institute de Investogaciones de Recursos Naturales CORFO.
20 p. July.
King, C.A. 1977. Classification and morphometry of the coast between 20° S and
42° S. Rev. Geog. Valparaiso 8:27-57.
Kohler, A. 1970. Geobotanische untersuchungen ankustendunen Chileswischen 27
and 42 Grad. Sud. Breite. Bot. Jahrb 30:50-200.
Kohler, A. 1967. Die entwicklung der vegetation auf kustendunen mitelchiles.
Umschau in Wissenschaft und Technik. 20/67:666-667.
Meisburger, E.P. 1962. Frequency of occurrence of the ocean surface waves in
various height categories for coastal areas. U.S. Army Engineer Research and
Development Laboratories. Report 1719-RR.
Meneses, T.J.N. 1897. Jeografia de Chile. Santiago, Chile: Imprents El
Comercio. 159 p.
Orson, et al. 1985. Response of tidal salt marshes of U.S. Atlantic and Gulf
coast to rising sea level. Journal of Coastal Research l(l):19-37.
Paskoff, R. 1970. Le Chili semi-aride. In: Recherches Geomorphologiques.
Bordeau, France: Biscaye Freres. 420 p.
Paskoff, R. 1978. Sur 1'evolution geomorphologique du grand escarpement cotier
du Desert Chilien. Geogr. Phys. Quat. 32(4):351-360.
Pflaker, G., and J.C. Savage. 1970. Mechanism of the Chilean earthquakes of May
21 and 22, 1960. Geol. Soc. Amer. Bull. 81:1001-1030.
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Ramirez, C. et al. 1988. Estudio vegetacional de una marisma del centro-sur de
Chile. Medio Ambiente 9(2):21-30.
Reiche, C. 1934. Geografia botanica de Chile. Santiago, Chile: Imprenta
Universitaria.
Saint-Amand, P. 1963. The Great Earthquakes of May 1960 in Chile. Washington,
DC: Smithsonian Institution, pp. 337-363.
Schwaar, J. 1978. Halophyten-gesellschaften in Sudchile. Verhandlungen deir
Gesellschaft fur Okologie Kiel 1:409-411.
Tudor Eng. Co. 1965. Report for a Waterfront Facility. Constitucion, Chile.
San Francisco, CA: Tudor Eng. Co. 276 p.
Vidal Gormaz, F. 1901. Hundimientos i solevantamientos verificados en las
costas Chilenas. Revista Chilena Hist. Nat. (Valparaiso) 5(10):213-224.
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LIVING STRATEGIES AND RELOCATION
IN LATIN AMERICA
CRISTINA MASSEI
Fundacion Ambiente y Recursos Naturales
Moreno 2142, 1428 Buenos Aires, Argentina
ABSTRACT
Accelerated sea level rise will produce multiple and irreversible
transformations locally, regionally, and nationally in Latin America. Such
changes will not only involve geographic and economic aspects of the countries,
but also will produce irreparable losses to their historical and sociocultural
inheritance, particularly in the affected communities.
This paper focuses on how to study the implications of relocation, not the
implications themselves, with particular emphasis on "strategies for living" with
the relocation of affected communities, which is at present a well-known concept
in the Latin American social sciences field. This criterion makes it possible
to account for all the dimensions of social effects -- i.e., demographic,
socioeconomic, or cultural. It is defined as "the way in which the community
is organized and uses its environment." The family group is the primary unit
of analysis; the local community is also considered.
Because most inhabitants near the shore are subjected to marginal economies
bordering on poverty, such "strategies for living" may be little more than
strategies for survival.
INTRODUCTION
In Latin America, sea level rise will have multiple and irreversible social,
economic, and cultural effects locally, regionally, and nationally. These
effects will be so extensive that even the interior provinces will be affected,
because national transport, services, trade, and production centers are located
on the coast. Direct damages to these centers will affect national activities
and will bring about new physical, social, economic, and cultural configurations,
significantly restructuring communities and the future historical process.
The resettlement process is a social process that frequently is overlooked
in favor of the costs of flood damages, coastal defense, and other physical
effects of flooding. Frequently, poor families settle in coastal areas near
cities because urban centers supply services, consumer goods, and transitory and
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Central and South America
informal work sources. Consequently, we must design a relocation policy that
takes into account not only the losses of goods and dwellings, but also the
disruptions in the formal and informal links of the local community at all
levels.
We have developed a "living strategies" concept for the population in
general and "survival strategies" for the most impoverished sectors. These
strategies account for all the demographic, socioeconomic, and cultural
dimensions that must be considered when relocating communities. According to
Cernea (1989), in general, previous efforts to relocate communities have often
failed because people focused on physical logistics and underestimated the
social, cultural, political, and labor-market effects.
This paper lays out an analytic structure by which one could analyze the
social effects of relocation strategies. We warn the reader at the outset,
however, that the paper does not specifically address the effects themselves.
THE RESETTLEMENT PROBLEM
Involuntary displacements of population due to sea level rise would cause
economic and cultural shocks to many communities and destroy production goods,
valuable natural resources, and the local environment. Such displacements would
also create problems in areas that receive the transplanted population, because
if vacant land were scarce, the available natural resources would be severely
taxed (Cernea, 1989). Partridge (1983) wrote "the relocation process destroys
a pre-existent form of life." It transforms "every form of life, in all its
different aspects, such as institutional and social ones, economic systems,
guidelines to the community organization, power structures, everyday activities,
or the cultural tradition."
Because having one's hometown destroyed can give people a feeling of
helplessness, relocation strategies should focus on returning to the people some
control over their own lives, similar to the control they previously had. (It
cannot be exactly like the original control, because the preexisting
socioeconomic organization will not exist after the resettlement.) In addition,
officials in Latin America must take three important factors into account: (1)
the characteristics of the people to be relocated: in general these people
belong to the lowest socioeconomic stratum, which is why the relocation problem
is inseparably linked to the survival of these sectors; (2) the sociocultural
identity crisis, which makes people question the efficiency and validity of their
traditional strategies and survival schemes and increases their uncertainty to
such an extent that it immobilizes their capacity to respond; and (3) the impact
produced on social relations networks, on the existing leadership structure, and
on the behavioral guidelines.
METHODOLOGICAL APPROACH
Analyses of resettlement strategies should follow three guidelines: Do
not collect socioeconomic and cultural data without taking into account the model
of possible relocation policy. On the contrary, put the data in the order of
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Massei
the model from the precise moment of their recollection, description, and
analysis. Otherwise, the data will not be read in their proper context. The
model must consider the specific characteristics of the flooded area (which are
seldom included), and its type of links with the affected population. Finally,
the scheme must carry out an analysis in a more complex field than that of the
usual socioeconomic descriptions. Actually, sudden relocation basically affects
the population living strategies that include a number of relationships -- e.g.,
economic cooperation, neighboring links -- the modification of which gives rise
to the main social and economic cost that we are trying to reduce.
Defining this theoretical scheme is necessary for creating living strategies
that are equivalent to the present ones, so as to satisfy the needs of the
transplanted population. This "equivalent reposition" not only refers to the
replacement of affected dwellings and goods but also to the possibility of
obtaining work and earnings.
UNIVERSE OF ANALYSIS
According to the previous scheme, we define as "universe under study" the
population whose link to the area represents a significant component to its
living strategies. That is, not only are the residents in the area included,
but also the nonresidents who maintain ties (of labor, patrimony, etc.) with that
area, developing in this way some aspect of their overall living strategy. Then,
the main question is, Which are the modalities of that link between the
population and the affected area? These relations occur at different dimensions
(demographic, social, cultural, and economic) and result from the particular
historic development of the area, from its cultural reality, from its regional
economic institutions, and from its physical features (COMIP, 1984). It is also
necessary to analyze the compulsory vs. uncompulsory character of that link.
Among all the possible modalities, the most essential is that of the compulsory
link on an economic basis. This category includes the economic activities that
require the concurrence of some of the features of the area, such as obtaining
the area's raw materials (ichthyic fauna, soil materials, etc.) and food
(fishing), using its water for transport, using the area's coastal features or
its proximity to urban centers and ports for supplies and services, and using
its resorts for recreational activities and its land for production or dwelling.
The uncompulsory link, which can be easily reproduced in another area, will
include agricultural activities that are not inherent to the area, industrial
and commercial activities that do not require the area's raw materials, community
services (health, education, dwelling, etc.), and the familiar or community links
(cultural, religious, political, ethnic, etc.).
LIVING AND/OR SURVIVAL STRATEGIES
In developing relocation strategies, we are not dealing with good or bad
players who follow strategies either to win or to lose. Rather, we are concerned
with human beings who are doing their best to survive (Bartolome, 1983). Also,
the unit of analysis is not the individual, but rather the family, since people
organize themselves in families so as to face the problem of living.
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Central and South America
First of all, the survival strategies concept is used to study the
implications between the population factors (fertility, and familiar structures
and types) and a community's economic structure (productive patterns, labor
markets, etc.)- Later on, the concept is enlarged to include politics and
organizing behavior, provided the basic needs are satisfied not only in the area
of economics but also the areas of the society and politics. First, of the
strategies the poor social groups or sectors were analyzed. Then, with the
prompt diffusion of the concept, the middle and even the most privileged layers
of society were investigated. This approach allowed for the literature to
include generic definitions as well as more restricted and specific formulations.
As an example of the first type, it is worth mentioning the definition that
describes the survival strategies "as the attitudes or arrangements that take
place in the family to face the problem of existence or living, which in many
cases does not surpass the survival level" (Rodriguez, 1981). Consequently, any
type of family belonging to any social group or stratum can be the subject of
a strategy. Because of this definition, the living strategies notion has been
adopted.
In contrast, among other authors who use restricted formulations are Duque-
Pastrana (1973), who introduced this concept to the social sciences. They have
sustained that in order to ensure the family income, the survival strategies
must delineate the economic roles of every member of the family, even extended
family members. From this point of view, the subjects are exclusively families
belonging to the impoverished sector of society, and the strategies are only of
an economic sort. Aside from their discrepancies, the different approaches have
overlapped on the following items:
. the unit of analysis is the family instead of the individual;
. the survival or living strategies vary according to social strata; and
• the strategies are subjected to the prevailing "economic structure."
In this work we will define the "living strategies" concept as the modality
in which the unit organizes itself and makes use of its resources to reproduce
and/or optimize its material and nonmaterial conditions of existence; "survival
strategies" has a corollary definition, applied to the poorest social strata.
This definition is chosen because the problem of relocation involves all the
social sectors of the area to be flooded and these people are affected not only
economically but also socially, demographically, and culturally.
Groups who develop the living strategies consist of individuals who are
linked to one another by bonds that admit a common past and that jointly project
toward the future. The living strategy they use assigns the participatory roles
to each member of the group. The strongest group is the family, the fundamental
unit of analysis. We define this group as people whose association is based on
sharing a residence; being linked by blood or marriage; interacting daily,
regularly, and permanently; and tending jointly to the reproduction and/or
optimization of their material and nonmaterial conditions of existence.
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Massei
THE ENDOGENOUS COMPONENTS OF THE STRATEGIES
Because of the complexity of the problem of relocating, it is not easy to
delimit precisely the components of the living strategies, at least at the level
of those categories and variables that constitute them. Nevertheless, advances
provided by the specialized literature define a basic group of aspects or
dimensions of them that can be arranged according to different fields in which
they appear.
For example, in the socioeconomic field, the relevant elements are connected
with activities that involve obtaining goods and services to fulfill the unit's
basic needs. They include ways of being part of the productive structure, such
as in the employment arena; how the work is organized within the unit; ways and
sources for consuming goods and services; the network of interchanging goods and
services; and the network of mutual aid or extrafamiliar cooperation.
In the cultural field, special relevance is acquired by the values and the
rules put into practice in the acquisition and preservation of goods and services
(e.g., attitudes toward the role of women). These habits, attitudes, and
behavior are passed on through social inheritance (Bartolome, 1983). In fact,
they become such a part of the culture that they can obstruct the possibility
of improvement of the survival condition (Arguello, 1981).
The demographic field includes the considerations of the structure of the
units and their characterization in terms of sex, age, fertility, construction
ways of unions, mortality, migrations (especially those of a labor sort), the
familiar living cycle stages (initial, expansion, and fission), duration of said
stages, etc. These aspects are important to plan resettlement policies that may
take into account the family requirements in the long run.
Many variables have ambiguous implications according to the context in
which they appear. For example, in the demographic factors case, the fact that
a farming couple has many children could be considered as a survival strategy,
based on the reasoning that the more children they have, the more manpower they
can count on, and consequently the better resources they can have to fulfill
their needs. However, the large number of offspring can be a burden and, as a
result, a conditioning could occur that could influence negatively, because they
are in the family cycle's first stages and they have scarce productive resources.
CONTEXTUAL FACTORS
Table 1 lists a number of contextual factors that must be taken into account
for an exhaustive understanding of the strategies.
Local Level
The local level or the immediate social environment is where we find the
articulation of relationship or neighboring links that form the basis of
sociocultural identities and informal economic relations. In many cases, these
links contribute more to the support of the family than the monetary or formal
income. To know these links is very important because, apart from having an
425
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Centra? and South America
Table 1. Factors That Should Be Considered in Evaluating Relocation
Contextual factors Endogenous characteristics
- Access to the land - Demographic
- Social organization - Migratory
- Work market - Occupational
- Productive organization - Educational
- Goods market - Sociocultural
- Goods and services offered - Consumption
- Public policies
- Development projects
Source:COMIP - Precensus Tasks (1985).
effect on the strategies, they determine the behavior of population in social
processes, such as resettlement.
Regional/Subregional Level
This leads to a careful consideration of the surrounding regions or
subregions and of the area's interactions with them, even beyond the frontiers
among countries, surpassing the reductions to both the ecological and the
political administrative aspects. It is at this level where we will detect, on
the one hand, the structure of production and employment and, on the other hand,
the mechanisms to obtain goods and services through the so-called "needs
fulfillment circuits." The analysis of these circuits allows us to know the type
of needs to be fulfilled, to what extent they are fulfilled (especially the basic
needs), the area (space) where the goods and services are acquired, and the way
of approaching them.
National Level
The national level determines the historic and cultural context of
development. It is also at the national level where it would appear to be
convenient to evaluate the public policies that could affect the living
strategies and, above all, the scope and covering of the actions arising from
such policies in the regional field of the affected area, provided that process
will affect said field.
PROOF OF CONSISTENCY
A specific census was carried out according to this conceptual scheme for
the relocation policy of an Argentine-Paraguayan multipurpose hydroenergetic
project in the Parana River, Corpus Christi. Contrary to the conventional
census, it accounted for strategies, sociocultural components, and the formal
and informal links that exist in the affected area, apart from the demographic
and economic components.
426
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Massei
The same proof also verified the methodology's consistency and the
relevance of the constitutive variables. The typology elaborated on these
variables and on the previous knowledge about the population. These variables
appeared to be effectively discriminating, despite the fact that some "mixed"
productive insertion strategies were detected together with the cyclic character
of some of them, which revealed the necessity of incorporating the historic
prospect to achieve their adequate characterization. The important fact here
is that an exploratory proof has been carried out. This census does not rule
out the necessity of using other types of instruments and careful studies to
become more knowledgeable as regards cultural rules and values and the circuits
that lead us to fulfill the needs of people being relocated.
CONCLUSIONS
Resettlement is not simply physical evacuation, but a complex social
process. The following criteria are essential to a successful resettlement:
1. To fix as an aim of the policy that the whole of the affected population
could reconstruct its living strategies, generally improving its
conditions of existence. This reconstitution would consist of:
• keeping or substituting its resources and their optimization
modalities;
• keeping its social articulations and the cultural components of its
lifestyle;
introducing in its strategies changes positively valued by the people
in terms of their life projects; and
• obtaining the recognition of the involved actors that the subject
of this process is the population at an individual level as well as
under the different associative forms. Involved actors include
agency, the affected people, and the authorities.
2. To define as policy subjects all those who might be linked to the
affected area and whose link might constitute a significant component
of their living strategy (residents or nonresidents).
3. To define the living strategies as an affected object, because the
disruption between the units and the particular field where they develop
basically affects them. Consequently, they also appear to be the
replacement object -- that is to say, what the relocation policy must
restore to the population. This strategy's reconstruction will not
imply a mechanical transposition, but rather a functional replacement
equal to the economic and social conditions that are necessary to carry
out the strategies. This implies that other aspects, positively valued
by the people, could be generated functioning as alternatives of those
that cannot be reconstructed.
427
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Central and South America
4. It is not likely that the replacement can be carried out at comparable
levels, especially for those sectors whose conditions of existence are
definitely inferior to the socially accepted minimum standards of
existence. As a result, we will aim to generally improve those
conditions.
5. To encourage the people's participation in relocation decisions, both
direct and channeled through the different associative forms (either
formal or informal). The policy's formulation and its application will
grow out of that participation, positive modalities valued by the
affected people, and from specific modalities for each social sector.
6. To set the relocation units on two levels: one based on family, and
the other based on customs for the preservation of links and networks
among units.
7. To contemplate the reconstruction of the community's structure, and
the integration of the relocated people among each other and with the
receiving population.
8. To aim at establishing the new settlements in places as near as possible
to the former location, so as to maintain most of the preexisting links
and to count on circuits to obtain resources and to fulfill needs
already proved and recognized.
9. To include all the aspects -- social, economic, judicio-legal,
technical, etc. -- to guarantee the integral management of such
resettlement.
BIBLIOGRAPHY
Arguello, 0. 1981. Estrategias de supervivencia: un concepto en busca de su
contenido. Economia y Demografia XV. Buenos Aires.
Bartolome, L.J. Estrategias adaptativas de los pobres urbanos: El elemerito
entropico de la relocalizacion compulsiva. Entidad Binacional Yacyreta y Depto.
de Antropologia Social, Universidad Nacional de Misiones, Argentina.
Bartolome, L.J. 1983. Aspectos sociales de la relocalizacion de la poblacion
afectada por la construccion de grandes presas. UN-OEA. Buenos Aires.
Borsotti, C.A. La organization social de la reproduccion de los agentes
sociales, las unidades familiares y sus estrategias. Demografia Economica.
Mexico.
Cernea, M. 1989. Reloca!izaciones involuntarias en proyectos de Desarrollo.
Banco Mundial, Report No. 805, Washington.
COMIP. 1984. Tareas precensales, primera etapa. Buenos Aires-Asuncion.
COMIP. 1985. Tareas prcensales, segunda etapa. Buenos Aires-Asuncion.
428
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Hassei
COMIP. 1986. Formulacion preliminar de al Politica de Relocalizacion. Buenos
Aires-Asuncion.
Duque-Pastrana, E. 1973. Las estrategias de supervivencia economica de las
unidades familiares del sector popular urbano: una investigacion exploratoria.
PROELCE. Chile.
Jelin, E. 1983. Fatnilia, unidad domestica y division del trabajo (que sabemos,
hacia donde vamos). CEDES. Buenos Aires.
Massei, C. 1983. Methodologia general para el analisis socio-economico del
emprendimiento en la zona de Corpus. Efectos sociales de las grandes presas de
America Latina, Seminar. UN-OEA. Buenos Aires.
Massei, C., and G. Borches. 1983. Evaluacion y planificacion regional de una
obra publica de propositos multiples de gran envergadura. Buenos Aires.
Massei, C., and G. Borches. 1984. Concepto de estrategias de vida y su
inclusion en la elaboracion de politicas de relocalizacion, Seminar. UN-OEA.
Posadas, Argentina.
Partridge, W. 1983. Relocalizaciones en las distintas etapas de desarrollo de
los emprendimientos hidroelectricos. UN-OEA. Buenos Aires.
Rodriguez, D. 1981. Discusion en torno al concepto de estrategias de
supervivencial. Relatorio del taller sobre estrategias de supervivencia.
Demografia y Economica, Nro. 46. Mexico.
Torrado, S. 1981. Sobre los conceptos de estrategias familiares de vida and
proceso de reproduccion de al fuerza de trabajo: Notas teoricas-metodologicas."
Demografia y Economica, Nro. 46. Mexico.
Torrado, S. 1983. La familia como unidad de analisis en censos y encuestas de
hogares. CEUR. Argentina.
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NORTH AMERICA
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RESPONDING TO GLOBAL WARMING ALONG THE U.S. COAST
JAMES G. TITUS
Office of Policy Analysis
U.S. Environmental Protection Agency
Washington, DC 20460
INTRODUCTION
The process of responding to accelerated sea level rise in the United States
is well under way, at least for a phenomenon that is not expected for several
decades. Over the last seven years, almost all of the coastal states have held
at least one major conference on the subject, and a few of them have altered
coastal development policies to accommodate a future rise. Public officials are
generally familiar with the issue, as are representatives of the press,
nongovernmental organizations, and coastal investors. The federal government has
conducted assessments of possible nationwide responses, and of implications for
specific types of decisions, such as the design of coastal drainage systems,
maintenance of recreational beaches, and protection of coastal wetlands.
This paper examines possible responses to sea level rise in the United
States. Because the most important question is what should we actually do in
response to rising sea level, we focus primarily on the planning and engineering
strategies that will determine how activities on the coast eventually change.
Nevertheless, because the process by which society comes to understand the need
for action is also important, we conclude with a brief summary of the evolution
of U.S. sea level rise studies in the 1980s.
FUTURE RESPONSES: SHORELINE RETREAT AND FLOODING
The most important responses to sea level rise in the United States can be
broadly classified as responses to shoreline retreat, increased flooding, and
saltwater intrusion. In each case, the fundamental question is whether to
retreat or to hold back the sea.
Shoreline retreat has received by far the greatest attention; nevertheless,
because flooding involves the same strategic questions, we combine the
discussion. Because there is a general consensus in the United States to "let
nature take its course" in national parks and other undeveloped areas, we
examine only developed areas. We divide our discussion of this impact into two
433
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Wort/7 America
parts: barrier islands and the open coast, and sheltered areas. We conclude the
section by discussing when action is likely to be necessary.
Barrier Islands and the Open Coast
Oceanfront communities could respond to sea level rise by protecting
developed areas with dikes, pumping sand onto beaches and other low areas, or
retreating from the shore. Along mainland beaches, the last option generally
implies no coastal protection; in barrier islands, however, it would also be
possible to engineer a landward retreat of the entire island, creating new land
on the bayside to offset that lost to oceanside erosion. The four options are
illustrated in Figure 1.
To obtain a rough understanding of the relative costs of these options, we
examined Long Beach Island -- a long, narrow barrier island developed with
single-family homes and one- and two-story businesses (see Figure 2). Table 1
Table 1. Cost of Sea Level Rise for Four Alternative Options for Long Beach
Island, New Jersey (millions of U.S. dollars)
Sea level
rise
(cm)
Levee with
beach
Raise
island
Island
retreat
No
protection
30
60
90
120
150
180
210
240
52
434
509
584
659
734
809
884
Levee Sand
Total Cost
105 41
285 109
522 178
786 247
1048 308
1310 371
1574 431
1835 492
Incremental Cost
55
462
843
1548
1740
1932
total loss
total loss
30
60
90
120
150
180
210
240
0
330
0
0
0
0
0
0
52
52
75
75
103
103
110
110
105
180
237
264
262
262
262
258
41
68
69
69
61
61
61
61
55
407
381
705
190
total loss
total loss
total loss
Source: Weggel et al. (1989) (dike cost); Yohe (1989) (no protection).
434
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Titus
Initial Case
No Protection
Engineered Retreat
Island Raising
Levee
Figure 1. Responses to sea level rise for developed barrier islands.
illustrates the costs of the four options for a rise in sea level between 30 and
240 cm. For a rise greater than 50 cm, any of the protection options would be
less expensive than allowing the sea to reclaim the valuable resort property.
Although surrounding the entire island with a dike would be less expensive than
raising the island, it would be culturally unacceptable because it would
interfere with access to the beach, and people would lose their views of the bay.
Engineering a retreat would also be much less expensive than raising the
island in place, because the latter option would require more (and higher
435
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North America
National
Wildlife
Refuge
Beach
Haven
Beach
Township
,, Harvey
Ship Swrl North cedar*
Bottom City Beach
Figure 2. Long Beach Island, New Jersey.
436
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Titus
quality) sand. However, this option would be vigorously opposed by the
oceanfront owners who would have to move their houses to the bay side, as well
as by bayfront owners who might lose their access to the water. Moreover,
filling new bays,ide land would disrupt back-bay ecosystems unless the estuary
were also allowed to migrate landward onto the mainland (which we discuss below).
As Table 2 shows, island raising would cost less than $600 per house per year
(U.S. dollars) until after sea level had risen more than 60 cm; this would be
less than the rent for one week. Thus, we suspect that the more expensive but
less disruptive approach of pumping sand onto beaches and the low bay sides of
barrier islands would be the most commonplace, at least in the beginning.
Table 3 compares the ability of the four options to satisfy various
desirable criteria. (Most of the rationale for this table is found in Titus,
1990.) An important lesson from the Long Beach Island study is that the least
expensive solutions are not always the most likely; dikes are culturally
unacceptable, and an engineered retreat is administratively difficult.
Nevertheless, the noneconomic criteria should not always outweigh economics.
Leatherman (1989) estimated the quantity of sand necessary to hold back the
sea for every coastal state but Alaska, and estimated the cost assuming that sand
does not become more expensive. Titus et al. (1990) adjusted those cost
estimates on the assumption that as least-cost supplies are exhausted, it will
Table 2. Evolution Over Time of the Relative Costs of Retreat Island Raising
(Long Beach Island, New Jersey)
Sea level
above 1986
(cm)
15
30
45
60
75
90
105
120
150
180
210
Year*
2013
2031
2045
2057
2068
2078
2087
2096
2112
2126
2139
Years before
sea will
rise 15 cm
18
14
12
11
10
9
9
8
7
6.5
6
Cost (mil
Retreat
20
34
34
34
34
34
34
34
30
30
30
lions) Cost (U.S.
Raise
island
57
85
95
110
127
132
132
132
132
132
132
Retreat
77
168
196
214
235
261
261
294
296
319
346
$/vr/house)
Raise
island
219
420
548
692
879
1015
1015
1142
1305
1406
1523
* Assuming global sea level rises one meter by the year 2100.
NOTE: All costs assume that until the particular year, the community has
responded to sea level rise by raising the island in place.
Source: Titus (1990)
437
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North America
Table 3. Ability of Alternative Responses to Satisfy Desirable Criteria, Long
Beach Island, New Jersey (assuming 1 m rise by 2100)
Policy:
Dikes Raise Engineered
Islands Retreat
Abandonment
Forced Unplanned
Criteria
Social Cost
Cumulative 584 786 247 1548 1548
($millions)
Present Value
($millions, 3%) 115 130 46 170 170
Environmentally No Usually Usually Yes Yes
Acceptable
Culturally No Yes Yes No Maybe
Acceptable
Legal Yes Yes Maybe Maybe Yes
Constitutional Yes Yes Yes Maybe Yes
Institutionally Yes Yes Maybe Maybe Yes
Feasible
Performs Under Poor Good Good Good Good
Uncertainty
Immmune to Yes Mostly Somewhat No Mostly
Backsliding
Source: Titus (1990).
be necessary to go farther out to sea for suitable sand. Table 4 illustrates the
resulting estimates of dredging costs for current trends and rises in sea level
of 50, 100, and 200 cm. Titus et al. also estimated the cost of elevating
buildings and utilities as sea level rises.
These calculations are only rough estimates. Leatherman probably
underestimated total sand requirements by assuming that beaches would be designed
only for a one-year storm; designing them for a 100-year storm would increase the
cost by 50-100 percent. Moreover, Titus et al. ignored the cost of elevating
multifamily buildings, and sea level rise would be factored into routine
reconstruction of water and sewer lines at no incremental cost. On the other
hand, our calculations assume that all developed areas will be protected.
Although this is a reasonable assumption for Long Beach Island and similar areas,
it would be less expensive to abandon more lightly developed islands. Moreover,
438
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Titus
Table 4. Nationwide Impact of Sea Level Rise on the United States
Trend 50 cm 100 cm 200 cm
If No Shores Are Protected
Dryland lost (sq mi) 3,315-7,311 5,123-10,330 8,191-15,394
Wetlands lost (%) 17-43 26-66 29-76
If Developed Areas Are Protected
Dryland lost (sq mi) 2,200-6,100 4,100-9,200 6,400-13,500
Wetlands lost (%) 20-45 29-69 33-80
Cost of coastal defense
(billions of 1988 dollars): 32-43 73-111 169-309
Open coast:
Sand 15-20 27-41 58-100
Elevate structures 9-13 21-57 75-115
Sheltered shores 5-13 11-33 30-101
If All Shores Are Protected
Wetlands lost (%) 38-61 50-82 66-90
Source:Titus et al. (1989).
a number of states have already required construction to be set back from
theshore a few hundred meters, suggesting that no protection would be required
for the first 50 cm of sea level rise.
Sheltered Waters
Americans' affinity for beaches and concern for the environment have
created a strong constituency against holding back the sea with dikes and
seawalls, counterbalancing the natural tendency of all landowners to protect
their property. Along the open coast, both interests can be accommodated,
because beach nourishment protects property by maintaining the natural
shoreline. Along sheltered waters, however, the prospects for avoiding a
conflict are not as great. As Figure 3 shows, protecting property with dikes and
bulkheads would prevent wetlands from migrating inland and could eventually
result in their complete loss in some places.
In a recent EPA report to Congress on the implications of global warming,
Park et al. (1989) examined the potential loss of wetlands and dryland for a
sample of 46 sites comprising 10 percent of the U.S. coastal zone, for three
alternative responses: no protection, protecting areas that are densely
developed today with dikes and bulkheads, and protecting all shores. For each
site, Weggel et al. (1989) estimated the cost of protecting developed areas from
439
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North America
5000 YEARS AGO TODAY
-»— SEA LEVEL ^"ttllBpWilt 2— CURRENT
^l*»i^#^ SEA LEVEL
SEDIMENTATION AND
PEAT FORMATION
FUTURE
SUBSTANTIAL WETLAND LOSS WHERE THERE IS VACANT UPLAND
-CURRENT
SEA LEVEL
CURRENT
SEA LEVEL
PEAT ACCUMULATION
Figure 3. Evolution of a marsh as sea level rises (Titus, 1986).
a 2-meter rise. Titus et al. (1990) used cost functions suggested by Vleggel et
al. and estimates of inundated land from Park et al. to interpolate the cost
estimates, and developed confidence intervals for the estimates of lost land.
Table 4 illustrates the nationwide results (the source studies provide
regional detail). For a one-meter rise, the cost of protecting the most densely
developed 1,000 square miles of coastal lowlands would work out to $3,000 per
acre per year, which would generally warrant protection. However, such
protection would increase the loss of wetlands by 300-500 square miles, and would
reduce the area of shallow water for submerged vegetation by another 500-700
square miles. Moreover, many vacant areas are being rapidly developed. If all
areas must be protected, the additional loss of wetlands would be 1,800-2,700
square miles, and another 3,000-7,000 square miles of shallow waters would be
lost.
The political process will have to decide whether to abandon coastal
lowlands to protect the environment. To help the necessary discussions get under
way we are circulating a draft that investigates seven options for enabling
coastal wetlands to migrate landward (Titus, 1989). The first two apply only to
undeveloped areas: prohibiting development and purchasing coastal lowlands. The
next three involve doing nothing today and purchasing land and structures when
440
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Titus
inundation is imminent; forcing people to move out when inundation is imminent;
or hoping that protection will prove to be uneconomic. The final two options,
which we call "presumed mobility," allow people to use their property as they
choose, but on the condition that they eventually will abandon it if and when sea
level rise threatens it with inundation; presumed mobility could be implemented,
whether by prohibiting construction of bulkheads and levees or by converting
property ownership to long-term or conditional leases that expire when sea level
rises a particular amount.
Table 5 summarizes our assessment of each option to satisfy various
desirable criteria, including low social cost, low cost to taxpayers, performance
under uncertainty, equity, constitutionality, political feasibility, and the risk
of backsliding. Unlike the table for barrier islands, we omit environmental
criteria because each of these options is each designed to achieve roughly the
same level of environmental protection.
Our overall assessment is that presumed mobility would be the best general
approach. A general prohibition of development would probably violate the
takings clause of the Bill of Rights; buying 20,000 square kilometers of land
would be expensive, and in any event, these options apply only to areas that have
not yet been developed. Doing nothing today seems unlikely to protect wetlands
because (1) purchasing property in the future would be even more expensive if it
is developed; (2) forcing people to move out of their homes would be
politically impossible if they are willing to tax themselves to pay for the
necessary protection; and (3) economics alone is unlikely to motivate people to
abandon developed areas.
One of the most overlooked but important criteria is performance under
uncertainty. No one knows how much sea level will rise in the future; only rough
estimates are available. Thus, policies likely to succeed for a rise anywhere
between 0 and 3 meters should be preferred over those that might be superior for
a particular scenario but might fail if other scenarios unfold. For this
criterion, the approach of presumed mobility is clearly superior: ecosystems will
be protected no matter how much sea level rises; real estate markets will be able
to efficiently incorporate new information on sea level trends; and if the sea
does not rise significantly, the policy costs nothing. By contrast, buying
coastal lowlands or prohibiting development requires policy makers to draw a
(disputable) line on a map above which the policy does not apply. If sea level
rises more than assumed, ecosystems eventually will be lost; if it rises less,
society will have unnecessarily forfeited the use of valuable coastal land.
When Will a Response Be Necessary?
A recent study by the National Research Council (Dean et al., 1987)
concluded that because dikes can be erected in a relatively short period of time,
no action is necessary today. This argument also applies for beach nourishment
on the open coast. However, our analysis of wetland-protection options suggests
441
-------
Table 5. Alternative Strategies for Protecting Natural Shorelines: Areas That Have Not Yet Been Developed
Cost
Policy to public
1. Prohibit None
Development
2. Buy Speculative
coastal premium
land
Defer Action
3. Order None
people out
later
4. Buy land and
out later structures
5. Rely on None
elements/
economics
Presumed mobi I i ty
6. No None
bulkheads
7. Leases <1X of land &
residual value
Social Cost
(vs. no sea level rise)
Present
Speculative
premium +<1X
of base value
Speculative
premium + <1%
of base value
<1X of land
and structures
<1X of land
and structures
<1X of land
and structures
<1X of land
value
<1X of land
value
Performance under
Economic uncertainty:
Const i- Political New
tutional feasi- Risk of institutional Likelihood of
value Cumulative Efficiency Sea Level Economics Equitable bility backsliding requirements succes:
Land
Land
Land and
structures
Land and
structures
Land and
structures
Land + residual
value of
structures
Land + residual
value of
Poor No Yes
Poor No Yes
Fair Yes Perhaps
Fair Yes No
Fair Yes Useless
(if it
works)
Optimal Yes Yes
Optimal Yes Yes
No No None Possible
Yes Yes None Possible
Maybe Doubtful Low Very
likely
Yes Yes Low Very
likely
Yes Yes Good Low
Probably Good Likely
Usually
Yes Yes Fair Very
unlikely
Regulatory
Park Service
aquisition
Police
Park Service
Aquisition
Hazard
Mitigation
Regulatory
Change in
titles of
Almost certain
at first, un-
likely in long
run
Almost certain
at first,
unlikely in
long run
Unlikely
Unlikely
Unlikely
Very likely
Almost
certain
ro
-------
Titus
that these measures are likely to be effective only if they are implemented
several decades in advance: people would need several decades to depreciate
structures and to become accustomed to the idea that property must be abandoned
to the sea to protect the environment.
A number of planning mechanisms are in place along the ocean coast to
foster a retreat. North Carolina and a number of other states require houses to
be set a few hundred meters back from the beach and prohibit hard engineering
structures along the beach. South Carolina prohibits reconstruction of
storm-damaged property if such property is too close to the shore.
Along wetland shores, however, only Maine has implemented planning measures
to allow ecosystems to migrate inland. That state has explicitly incorporated
presumed mobility into its development regulations, which state that structures
are presumed to be movable; in the case of apartments that are clearly not
movable, the regulations state that if the buildings would block the landward
migration of wetlands and dunes resulting from a one-meter rise in sea level, the
developer must supply the state with a demolition plan. Although other states
require construction to be set back somewhat from the wetlands, the setbacks are
small compared with the inland migration of wetlands that would accompany a one-
meter rise in sea level.
FUTURE RESPONSES: MISSISSIPPI DELTA
Louisiana is currently losing over 100 square kilometers of land per year
because human activities are thwarting the processes that once enabled the
Mississippi Delta to expand into the Gulf of Mexico. For thousands of years, the
annual river flooding would deposit enough sediment to enable the delta to more
than keep pace with sea level rise and its own tendency to subside. In the last
century, however, the federal government has built dikes along the river and has
sealed off "distributaries" to prevent flooding and to maintain a sufficiently
rapid riverflow to prevent sedimentation in the shipping lanes. As a result,
sediment and nutrients from the river no longer reach most of the wetlands, and
they are being rapidly submerged. Moreover, with flows in distributaries cut
off, saltwater is penetrating inland, converting cypress swamps to open water
lakes and otherwise disrupting wetlands. If sea level rise accelerates, the
already rapid disintegration of coastal Louisiana would follow suit.
As with other coastal areas, both dikes and abandonment are possible.
However, there is a general consensus that these options should be avoided if
possible, because in either event, most of the delta's wetlands would be lost,
and those wetlands support 50 percent of the nation's shellfish and 25 percent
of its fish catch. Thus, federal and state officials are focusing primarily on
options to restore natural processes that would enable at least a large fraction
of the delta to survive even an accelerated rise in sea level. The U.S. Congress
has authorized a number of projects to divert freshwater and sediment to wetlands
by effectively cutting holes in the dikes. Under current policies, however, such
projects will likely divert only a small fraction of the river water to avoid
siltation of shipping lanes.
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North America
In the long run, protecting Louisiana's wetlands would require people to
allow the vast majority of the river's discharge to reach the wetlands. This
would be possible if navigation were separated from the streamflow of the river.
One way to do this would be to construct a series of canals with locks between
New Orleans and the Gulf of Mexico, and to completely restore the natural flow
of water to the delta below the canal. Unfortunately, requiring ships to pass
through locks would hurt the economic viability of the Port of New Orleans.
Another option would be to build a new deep-water port 10-20 miles to the east.
Perhaps the far-reaching response, one that has been advocated by the
state's Secretary for Environmental Protection, would be to allow the river to
change course and flow down the Atchafalaya River. Without a $1 billion river
control structure, the river would already have done so. Although from a purely
environmental perspective this option is most appealing, it would further
accelerate the loss of wetlands in the eastern part of the state and would enable
saltwater to back up to New Orleans, requiring the city to find a new water
supply.
It is somewhat ironic that human activities designed to prevent flooding
may leave the entire area permanently below sea level in the long run. There may
be a lesson for Bangladesh and other nations who are considering flood-protection
dikes to protect land from surges in river levels: build dikes around a few
cities, but make sure the river is still able to flood enough areas for the flow
of water to slow sufficiently to deposit sediment onto farmland and wetlands,
rather than washing sediment out to sea where it will benefit no one.
FUTURE RESPONSE: SALTWATER INTRUSION
Responses to saltwater intrusion, like shoreline retreat and flooding, can
involve either holding back the sea or adapting to a landward encroachment.
Preventing Salinity Increases
Figures 4 and 5 illustrate why sea level rise increases the salinity of
estuaries and aquifers, respectively. In the former case, a rise in sea level
increases the cross-sectional area of the estuary, slowing the average flow of
water to the sea, the major process that keeps the estuary from having the same
salinity as the ocean. Assuming that the tides continue to carry the same amount
of water and that mixing stays constant, salinity will increase because the force
of freshwater is reduced while the saltwater force is increased. Moreover, if
the bay becomes wider, the tidal exchange of water will increase, further
increasing the freshwater force. (Because it is difficult to graphically
represent the previous explanation, Figure 4 expresses it in a different fashion
by comparing the amount of freshwater entering the estuary with the amount of
seawater from the tides.)
Salinity increases can be prevented either by impeding the ability of
saltwater to migrate upstream or by increasing the amount of freshwater entering
the estuary. During the drought of 1988, the New Orleans District of the Corps
of Engineers designed a barrier across the bottom of the Mississippi River that
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blocked saltwater on the bottom while allowing the ships and freshwater to pass
on the top. In many cases where human withdrawals of freshwater have increased
estuarine salinity e'nough to have adverse environmental consequences, water
resource agencies have constructed projects to divert freshwater into estuaries.
Elsewhere in Louisiana, the Corps has designed projects to divert water from the
Mississippi River to wetlands that are suffering adverse effects of saltwater
intrusion; and Everglades National Park has long had a similar arrangement with
the Corps of Engineers and the South Florida Water Management District.
The Delaware River Basin Commission (DRBC) releases water from its system
of reservoirs whenever salinity reaches undesirable levels, to protect
Philadelphia's freshwater intake and aquifers in New Jersey that are recharged
by the (usually) fresh part of the river. Hull and Tortoriello (1979) estimated
that a 13-cm rise in sea level would require an increase in reservoir capacity
of 57 million cubic meters (46,000 acre-feet), while Hull and Titus (1986)
suggested that a 30-cm rise would require about 140 million cubic meters, about
one-fourth the capacity that would be provided by the proposed Tocks Island
reservoir. Hull and Titus also noted that the DRBC has identified reservoir
sites sufficient to offset salinity increases from sea level rise and economic
Initial Condition
Freshwater
Saltwater
After Sea Level Rise
Figure 4. Increasing bay salinity due to sea level rise.
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\. . j Freshwater
Saltwater
Figure 5. Impacts of sea level rise on groundwater tables. According to the
Ghyben-Herzberg relation, the freshwater/saltwater interface is 40 cm below sea
level for every cm by which the top of the water table lies above sea level.
When water tables are well below the surface, a rise in sea level simply raises
the water table and the fresh/salt interface by an equal amount (A-B). Where
water tables are near the surface, however, drainage and evapotranspiration may
prevent the water table from rising. In such a case (C), the freshwater table
cour narrow greatly with a rise in sea level: for every 1-cm rise in sea level,
the fresh/salt interface would rise 41 cm.
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growth well into the 21st century. Williams (1989) conducted a similar analysis
of the impacts of and responses to sea level rise in the Sacramento Delta in
California.
Although dams can be useful, one must understand their limitations. Most
important, there is a finite amount of water flowing in the typical river; dams
can increase the freshwater flow during the dry season because they reduce the
flow during the wet season. Because droughts are generally the only time when
high salinity is a concern, the impact on salinity during the wet season is
generally not a problem. Dams also reduce flooding, which (as we discussed
above) can be viewed as a benefit by people who might otherwise lose property (or
drown) in a flood; but this is a liability to the extent that flood prevention
keeps sediment from reaching wetlands and enabling them to keep pace with sea
level. A final problem is that if climate change makes droughts more severe in
the future, it may be difficult to find sufficient reservoir capacity to offset
the resulting reductions in riverflow, let alone increase riverflow enough to
offset sea level rise. Salinity increases in aquifers can also be prevented by
either increasing the force of freshwater or by decreasing the force of
saltwater. The most notable application of the former approach is in southern
Florida, where water managers maintain a series of freshwater canals whose
primary purpose is to recharge the Biscayne Aquifer with freshwater. Various
types of barriers have also been identified for blocking saltwater intruding into
the estuary (Sorensen et al., 1984).
Decreasing depletive uses of water can help to offset salinity increases.
For example, during droughts the Delaware River Basin Commission has the power
to curtail diversions of water to New York City. Reducing water consumption
within the basin is a critical component of water management strategies in this
and many other regions.
Adapting to Salinity Increases
If measures are not undertaken to prevent increase of salinity, people will
have to adapt to it. Some cities could respond by moving their intakes upstream.
Note that this appears to be the only response to increased salinity that would
work with sea level rise but (at least in many cases) not with decreased
riverflow. In the case of sea level rise, moving the uptake upstream the same
distance as salinity advanced would leave the public (and if ecosystems were able
to migrate upstream and inland, the environment) in roughly the same condition
as before the sea level rose. By contrast, if less freshwater is flowing into
an estuary, there may no longer be enough freshwater to supply the previous level
of consumption.
Another response is to shift to alternative supplies. For example, if
flows in the Mississippi River decline, or if wetland loss motivates policy
makers to allow the river to change course, New Orleans would have to abandon the
river as a supply of freshwater. Many argue that the river is polluted enough
to view such a situation as a "blessing in disguise," and have suggested that the
groundwater under Lake Ponchartraine would be a suitable source (Louisiana
Wetland Protection Panel, 1987). Nevertheless, alternative supplies are finite
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and may become increasingly scarce as the economy grows, especially in areas
where the greenhouse effect fails to increase precipitation enough to offset the
increased evaporation that warmer temperatures invariably imply.
Water conservation is likely to play an increasingly important role in
efforts to adapt to reduced availability of freshwater. Many jurisdictions
already place restrictions on depletive uses, such as watering lawns and washing
cars. Officials in New Jersey are planning to ration the water that farmers
withdraw from the Potomac-Raritan-Magothy Aquifer, which is recharged by the
Delaware River. Nevertheless, regulations of water use are difficult to enforce
and generally apply only to a limited number of visible activities.
In our view, the best long-term response would be to treat water like any
other scarce commodity: sell water at a market-clearing price, rather than at
a price based on cost. There is an emerging trend in this direction among large
water users in the western United States, but the principle is likely to face
severe cultural and institutional barriers. First, Americans generally believe
that water should be as free as the air we breathe. Second, public utilities
generally are not allowed to make a profit. Nevertheless, with increasing
government deficits and a gradual acceptance of the scarcity of water, the public
would probably learn to accept water markets.
The Need for Near-Term Action
As with dikes built to prevent inundation, there is no need to build dams
or canals to counteract future saltwater intrusion. Nevertheless, setting aside
sufficient land for future dam sites is similar to allowing wetlands to migrate
landward: it will be less expensive to prevent people from developing the land
today than to buy people out later. Accordingly, to the extent that regions will
rely on dams in the future, it would be best to identify those sites today and
implement policies that will keep options open for future reservoir construction.
The matter of reserving land for dams or wetlands illustrates a principle
that may apply to other commodities: even when a particular action will not be
necessary for a few decades, it is best to establish the "rules of the game" in
advance so that people can gradually take whatever measures are necessary based
on how they perceive the probability and eventuality of the particular situation
that is anticipated. If we want to use water efficiently, its price will
eventually have to rise. Political realities prevent a substantial rise today,
but if the government put everyone on notice that it would charge a fair-market
price beginning in the year 2030, the public would probably accept such a policy.
It is easier to agree on what is fair when no one is immediately threatened, and
honorable people do not object to fulfilling the conditions of treaties,
contracts, and other arrangements made by a previous generation.
EVOLUTION OF THE U.S. RESPONSE: 1982-1989
For most practical purposes, the United States began to seriously examine
potential responses to accelerated sea level rise in the summer of 1982. Two
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officials of the U.S. Environmental Protection Agency (EPA), John Hoffman and the
head of his office, Joseph Cannon, were troubled by an apparent failure in
information transfer. For several years, climatologists had warned that a
global warming due to ,the greenhouse effect was likely (NAS, 1979, 1982). Yet
federal, state, and local officials responsible for coastal decision making
either were generally unaware of this prospect or viewed it as mere speculation.
No one had estimated the likely rise in sea level for specific years, and
even if they had, the EPA officials were not sufficiently familiar with coastal
activities to know whether consideration of a possible rise would warrant changes
in current decision making. But Hoffman had a hunch that sea level rise would
justify changes in at least some decisions, and convinced Cannon to initiate a
small program to begin the process by which the United States prepared to live
with a rising sea on a warmer planet.
In retrospect, it may seem strange that EPA, a regulatory agency
responsible for controlling pollution, first addressed the greenhouse effect
issue by initiating a program to adapt to a global warming, rather than a program
to reduce emissions of greenhouse gases into the atmosphere. Even then, a number
of environmental groups were initially suspicious that the Agency was effectively
"throwing in the towel." But in the context of what could actually be
accomplished at the time, the strategic decision Cannon made was perfectly
rational. The nation had just elected a new president who had promised to relax
environmental regulations; nonregulatory approaches to protecting the environment
seemed to have more promise. The planned sea level rise project would encourage
state and local officials to anticipate sea level rise, with the hope of
averting situations that would otherwise eventually necessitate regulations.
Moreover, there was no public consensus to reduce global warming; a project aimed
at increasing awareness would help create the political conditions necessary for
policy makers to consider reducing emissions of C02 and other greenhouse gases.
The first major activity of the Sea Level Rise Project was an
interdisciplinary study in which Hoffman et al. (1983) estimated the range of
future sea level rise; Leatherman (1984) and Kana et al. (1984) used those
scenarios to estimate the physical effects on Galveston, Texas, and Charleston,
South Carolina; Sorensen et al. (1984) provided rough cost estimates for
engineering responses to sea level rise; and Gibbs (1984) and Titus (1984)
performed economic analyses using the information provided by the other
researchers. The results were presented at a conference in Washington in 1983
and were published the following year (Barth and Titus 1984).
The initial effort was only partly successful. On the positive side,
Hoffman's study estimating sea level rise prompted the National Academy of
Sciences to prepare their own estimate (Revelle 1983), so that by the end of the
first year, there were two available studies, both of which suggested that a
substantial rise in the next century was likely. We were also successful in
making officials and coastal scientists aware of the potential for a significant
rise: (1) our reports were written for the layman -- no matter how technical the
subject matter of a study, they always included an overview chapter that
explained the contents; (2) we sent out form letters to most of the people in the
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country working on coastal issues, telling them how to obtain our reports, and
about one-third of them responded by requesting at least one document; and (3)
we gave about 50 speeches and briefings every year on the subject to government
offices and public meetings.
However, we failed to obtain our most important objectives. By 1984, we
had identified only a handful of issues where we could make a case that sea level
rise required changes in current practices. Moreover, while we continued to
study the issue, we were generally unable to convince federal and state agencies
with a stake in sea level rise to undertake efforts themselves to address the
issue. There were four notable exceptions: (1) the National Academy of Sciences
formed panels to (a) estimate the future contributions of glaciers to sea level
rise (Meier et al., 1985) and (b) assess the engineering implications of a
possible rise (Dean et al., 1987); (2) Orrin Pilkey, the most prominent
environmental activist on coastal matters, began to incorporate global warming
into his many speeches to civic groups on the need for coastal development to
be more sensitive to environmental processes; (3) the Army Corps of Engineers
agreed to cofund with EPA a $25,000 study on the implications of sea level rise
for coastal protection works (Kyper and Sorensen, 1985); and finally (4) the
legislature of Terrebonne Parish, a local government in Louisiana, passed a
resolution calling on Congress to improve estimates of future sea level rise and
initiated a $100,000 study on response strategies for their community, which was
already facing substantial erosion due to subsidence (see Edmonson, Volume 1).
It was clear that we were doing something wrong, so in mid-1984 we changed
the focus of our studies. From then on, we decided to fund studies only after
we had internally developed a specific hypothesis demonstrating that a
consideration of sea level rise would alter decisions people make today. In the
ensuing two years, we commenced studies to investigate the following hypotheses:
(1) sea level rise would destroy a large fraction of our coastal wetlands unless
planning solutions were soon implemented to require development to be abandoned
to allow wetlands to migrate inland (Titus et al., 1984); (2) because groins help
to control erosion due to alongshore transport but not the offshore erosion from
sea level rise, a consideration of the issue would prompt the State of Maryland
to drop its plans to build more groins at Ocean City, Maryland, and instead
employ beach nourishment; (3) because it is much easier to put slightly larger
pipes in a coastal drainage system during construction than subsequently to add
new pipes, it would be rational to design new coastal drainage systems with an
allowance for sea level rise; (4) sea level rise would accelerate the already
alarming rate of land loss in Louisiana, and hence, imply that action is much
more urgent than currently assumed; and (5) increased salinity in the Delaware
Estuary might eventually necessitate additional reservoirs to protect
Philadelphia's water supplies, and although they need not be built today, the
risk of this eventually happening warrants land use planning to ensure that all
the suitable sites are not developed.
Because we had conducted "back of the envelope" assessments that
demonstrated the need to consider sea level rise before funding them, all of the
studies turned out to demonstrate that even a 50-50 chance of accelerated sea
level rise would warrant changes in current decision making. Although sea level
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rise was probably not the only reason, within a month of the Ocean City study's
(Titus et al., 1985) release, the State of Maryland announced that it would shift
its erosion-control strategy from groins to beach nourishment (Associated Press,
1985). (The wetland study (Titus, 1988) was not released until much later, but
even while it was still in draft, the State of Maine responded by issuing
regulations requiring that structures be removed if necessary to enable wetlands
and dune ecosystems to migrate landward.)
Although the other studies (Titus et al., 1987; Louisiana Wetland
Protection Panel, 1987; Wilcoxen, 1986) did not precipitate specific actions,
they provided additional examples to buttress our claim that people should begin
preparing for sea level rise, even though it is uncertain. We continued to give
about 30 speeches a year on the subject to various communities and professional
organizations, trying where possible to talk to enough people beforehand to
develop a hypothetical example relevant to their own activities where planning
for sea level rise today would be warranted. The fact that we could cite studies
demonstrating the rationality of planning today increased the credibility of our
assertion that the particular audience should consider it as well; and the fact
that Maryland and later Maine had made a decision based on sea level rise helped
convince people that policy makers are capable of planning for the long-term
future.
Although many scientists, reporters, low-level officials, and members of
the public continued to request our reports, in the beginning of 1986 we knew
that we had failed to achieve our primary goal of motivating people to prepare
for sea level rise. We had the sense that we were fulfilling a need to have
someone thinking and telling people about the long-term implications of current
activities, but that for most people, our activities were little more than a
curiosity; practical people could safely ignore the issue of sea level rise.
But then the British Antarctic Survey discovered an emerging hole in the
ozone over the South Pole. This seemingly unrelated event attracted the
attention of several U.S. Senators, who held hearings on the subject and decided
to include the related issue of global warming. Suddenly, widespread public
attention was focused on the greenhouse effect and its impact on sea level. The
unusually hot year of 1988 further increased public awareness. For the first
five years of our project, we were able to motivate only a few agencies to
undertake any substantive efforts; in the last two years, the momentum of the
issue has motivated dozens of initiatives, as Klarin and Hershman (Volume 1)
discusses.
We would like to think that our initial efforts laid the groundwork for the
emerging response to sea level rise, even though at the time our efforts seemed
futile. By this line of reasoning, our initial reports explaining the issue
convinced low-level officials, low-level environmental spokesmen, and coastal
scientists that sea level rise is important, but failed to convince high-level
officials, heads of nongovernmental organizations, or prominent scientists that
the time was ripe for addressing the issue. When the ozone hole and hot year of
1988 convinced leaders that global warming is a serious issue, their lower-level
counterparts were already informed and ready to recommend action.
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We will never know whether our efforts made much of a difference in the
final analysis. Nevertheless, on the assumption that they did, we briefly offer
a few lessons that may be useful for nations beginning to prepare for future sea
level rise. First, it is important to designate an individual to work full time
on the issue. A key to the success of the EPA project is that Hoffman was able
to find someone who was sufficiently interested in the issue to stay with it for
the better part of a decade. It takes time to develop expertise
when a new issue emerges: much of the relevant information is unpublished, and
disciplines ranging from law and economics to biology and engineering must be
synthesized.
Second, because responding to sea level rise is likely to be decentralized,
public information is sufficiently important to warrant 10-20 percent of the
total budget and 25 percent of the project manager's time. Thousands of one-hour
conversations with reporters and professionals working on related issues will be
necessary, as well as many shorter conversations with curious citizens. Anyone
who views their time as too valuable to completely satisfy all inquiries is
doomed to failure. College students and low-level assistants who have the
initiative to question the project manager about the implications of future sea
level rise often surface later as influential researchers or directors of
organizations. Although the typical conversation on the subject may accomplish
little, the totality of thousands of conversations over the course of several
years produces a critical mass by which people begin to talk to each other about
the issue and spend their own time investigating its implications.
If the need to satisfy all inquiries is recognized, the project manager
will find that he or she can save time by preparing summary reports that explain
the issue to someone with no background in the issue. Managers of government
projects often commission numerous studies, and in their own minds, develop a
broad vision of the issue. But while they make the studies available, they
rarely prepare reports summarizing their perspective. This is unfortunate both
because preparing such reports disciplines one to examine the weaknesses in their
opinions, and because their overviews of the issue would correspond more closely
to what the public needs to know than would the reports prepared by specialists
in particular disciplines.
Finally, studies should begin with a socially relevant hypothesis before
being funded. In our case, the hypothesis was that a particular change in
current activities was warranted even if one allows for the possibility that sea
level might not rise. In some cases, it is worth examining an issue just to make
sure that no action is yet necessary. However, any project manager unable to
present a cost-benefit argument in favor of action today in at least a few cases
should be criticized for, at best, a lack of imagination and for, at worst,
directing resources to the wrong issues and thereby forfeiting any savings that
might be realized from preparing for sea level rise in other ares. Such
criticism may not always be fair, but the fear of receiving it will be a powerful
incentive to ensure that "no stones go unturned."
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CONCLUSION
No one would accuse the United States of overreacting to the prospect of
a rise in sea level' from the greenhouse effect; the process has been slow, but
steady. After seven years, we have reached the point where the relevant
disciplines and the relevant government agencies are considering the issue and
looking for opportunities to respond. Everyone realizes that it is difficult to
convince politicians to make short-term sacrifices for the long-term good, but
we have a public that is concerned about environmental quality in general and
the greenhouse effect in particular.
We understand that many of the assumptions American researchers take for
granted would not apply in other nations. Nevertheless, we believe that two
recommendations are universally appropriate for any foreign colleague who decides
to dedicate a number of years helping a nation prepare for rising seas. Focus
your efforts on identifying actions that need to be taken today and make sure
that no one ever considers you an expert on the issue. What you learn will be
important only if its knowledge becomes commonplace.
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SEA LEVEL RISE: CANADIAN CONCERNS AND STRATEGIES
K.B. YUEN
Assistant Director
Oceanography and Contaminants Branch
Physical and Chemical Sciences Directorate
Department of Fisheries and Oceans
200 Kent Street
Ottawa, Ontario, Canada, K1A OE6
INTRODUCTION: THE CANADIAN CONTEXT
Canada is a coastal nation bordering on three oceans and possessing over
244,000 kilometers of coastline -- the longest of any nation in the world. A
number of major cities and highways border on the ocean. There are also hundreds
of fishing villages, over one thousand small-craft harbors, and numerous fishing
plants. Many native communities are also located close to the shore, near the
marine natural resources upon which they traditionally depend for food. Various
industries, such as pulp and paper mills, coastal shipping, container ports, and
oil refineries, are also located at the shore for obvious marine transportation
advantages.
A rise in mean sea level is expected to have major impacts upon Canada's
coastal resources and infrastructure. Fortunately for Canada, a large proportion
of the coastline rises fairly steeply out of the sea, in the form of rocky shores
and fjords, and is thus not at risk of flooding and erosion. Much of Canada is
also remote. As a consequence of Canada's particular geography and relatively
low population densities, the potential impacts in Canada of rising sea level,
while expected to be of substantial significance and requiring specific policies
and strategies for adaptation, are not expected to be catastrophic or even
severe. This is very much in contrast to countries that possess much more
exposed coastal lowlands or that simply do not have the physical space to
consider alternatives for human resettlement, even if they wanted to do so.
In much of Canada, coastal impacts arising from higher ocean temperatures,
changes to river runoff, and related changes to the oceanography, circulation
patterns, ice cover, and hydrological cycle may be more important than those
resulting from sea level rise. For example, Pacific cod are already at the
southern limit of their distribution and may move north if water temperatures
increase substantially. Canadians are generally more concerned with noncoastal
impacts, such as potential shifts in agricultural and forestry patterns,
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hydroelectric power generation and lower water levels in the Great Lakes. (These
impacts are addressed by the "RUMS" subgroup of IPLC work group 3.)
In Canada, the assessment of sea level rise and the development of adaptive
options is still in its infancy. In the context of climate change, four recent
studies have been carried out: three relate to the impacts of sea level arise
on specific coastal cities (Charlottetown, Prince Edward Island; St. John, New
Brunswick; and Vancouver, British Columbia), and the fourth provides an overview
of impacts in Atlantic Canada. Generally, these studies have been based on the
hypothetical scenario of a one-meter rise, which is then superimposed upon the
20- and 100-year flood levels. This information is then superimposed on maps
of coastal resources to estimate the resources at risk. The Vancouver study also
looked at scenarios of 2- and 3-meter rises in sea level (Figure 1). It can be
concluded from these studies that the economic impacts of sea level rise can be
estimated reasonably well. However, the ability to predict the impacts on natural
ecosystems generally, and on marine ecosystems in particular, has not yet
advanced very far, which reflects the complexities of those systems and the level
of scientific ignorance.
POTENTIAL IMPACTS AND POSSIBLE ADAPTIVE OPTIONS
To review some of the specific impacts that might occur in Canada and some
of the potential adaptive options, it is useful to adopt a general hypothesis
of a one-meter rise in sea level (as opposed to looking at a 5-meter rise) over
the next 50 years. Based on present trends and predictions, a change of this
magnitude is a useful starting point for examining the need for coastal zone
management decisions over the next 10-25 years.
We caution that Canadian studies have not yet considered the vertical
movement of the Earth's crust. Data for the east coast show considerable
spatial variability. For example, in the Gaspe Peninsula, land is rising as
much as 40 centimeters per century; while in southern Newfoundland (400
kilometers to the east), land is subsiding about 50 centimeters per century; and
at the northern tip of Newfoundland (a further 400 kilometers north), it is
rising at 100 centimeters per century (Figure 2). Thus a rise in global sea
level would not necessarily imply a relative rise in sea level at all locations;
it might simply decrease the current rate at which sea level is falling. Similar
spatial variability has been observed on the west coast, where both tectonic
processes and glacio-isostatic rebound contribute to sea level change. The
removal of groundwater and the extraction of offshore and nearshore hydrocarbon
resources may also cause subsidence and compaction. The key points are that all
of the contributing processes have to be integrated to arrive at the overall net
change of mean sea level, and that these changes will vary from place to place.
Following are some of the key impacts expected in Canada and the adaptive
options to deal with them.
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Figure 1. Geologic map of the low-'iying Fraser River Delta region of heavily
populated Greater Vancouver, B.C. Map shows the location of dykes to prevent
flooding of deltaic islands. Broken line marks seaward limit of the delta
foreshore. Arrows indicate direction of present advance or retreat of the delta
front, solid bars denote no change (R.E. Thomson, personal communication).
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1.3
CO
QC
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h-
LU
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1.0 -
HALIFAX TIDE GAUGE
1900
1920
1940
YEAR
1960
1980
Figure 2. Sea level at Halifax, Nova Scotia is already rising at the rate of
0.3 meters per century. This is thought to be post-glacial adjustment, the
greenhouse effect could greatly accelerate the trend.
Coastal Infrastructure
With a rise in sea level, coastal infrastructure related to human settlement
and industrial development on all coasts will be subjected to some level of
increased flooding. In some cases, this risk will be new; in others, existing
flood risks will be exacerbated by increased water levels. Coastal
infrastructure so affected may be grouped into three general categories, namely:
existing permanent structures that would suffer loss or damage solely
attributable to a rise in sea level. Replacement or preventive
strategies, including resettlement, would require major new
expenditures. However, depending on the magnitude of the potential
loss or damage, investment in adaptive options may be unavoidable. The
loss of valuable waterfront land would also fall into this category, but
it might be offset by reclamation/landfill projects.
existing nonpermanent structures with finite life expectancies, which
would normally need to be replaced within the next 50-75 years anyway.
With careful planning, the incremental cost of taking sea level rise
into account when structures are replaced may be negligible in these
cases.
• new or planned infrastructures. The opportunity exists now to design
such structures to avoid or minimize the impact of sea level rise, also
at minimal cost.
In short, advance planning taking sea level rise into account before
construction is the most intelligent and cost-effective approach to the
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development of new coastal infrastructure. Based on the studies to date, the
cost of replacing or modifying coastal infrastructures in Canada in response to
sea level rise could be in the range of U.S. $3-4 billion or more. A large
fraction of this cost could be avoided by incorporating sea level rise into
routine maintenance and reconstruction costs.
Homes, Buildings, and Roads
In most coastal cities, a number of waterfront properties and structures
will be subject to flooding from a one-meter rise in sea level. Higher levels
will increase the risks posed by surface waves, tides, ice jams, storm surges,
river runoff, and sea ice. Accurate risk assessment will require detailed data
compilation and flood zone mapping at the local level.
The mitigative options range from permanent floodproofing of individual
structures frequently subjected to flooding to temporary protective measures
for areas subject to infrequent flooding. Where there are extensive lowlands
and the value of the affected infrastructure justifies it, a system of protective
dikes may be created. In the residential area of Richmond, British Columbia,
south of Vancouver, which constitutes high-price real estate located on a delta,
a diking system already exists. However, it would need to be topped off to allow
for higher sea levels, storm surges, and waves. Further new diking would be
needed if flooding threatens other farmlands within the river valley. In the case
of much less valuable property, such as the Village of Tuktoyaktuk (comprising
Inuit homes, oil company exploration shorebases, and an airport) located on the
shores of the Beaufort Sea and Arctic Ocean, it may be more cost-effective to
actually move the location of the town, or at least the flood-prone sections,
to higher ground. Fortunately for Canada, few situations will actually require
large-scale human resettlement.
Finally, new development on the waterfronts of Canada's major cities (for
residential, commercial, industrial, transportation, and recreational purposes)
continues to draw considerable business investment, simply because the waterfront
is one of the most desirable places to be. Property zoning, construction codes
and standards, and coastal zone planning processes need to take into account
the explicit possibilities of sea level rise.
Municipal Sewers and Water Supplies
A rise in sea level will affect the operation of sewer outfalls. In
addition, there will be flooding of existing storm and sanitary sewers located
near the water, which will result in either corrosion of the sewer pipes or a
backing up of the sewer systems resulting from inhibited outflows from the higher
sea levels at the outfall to the sea. Such flooding will in turn cause property
damage and create a health risk, including possible contamination of the drinking
water system. In light of the overriding public health considerations, a
modification of the affected sewage and water supply systems is inevitable. In
many communities, new sewers and sewage treatment systems are being planned at
a cost of billions of dollars. To protect those investments, it is essential
to design now for higher sea levels in the future.
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Ports, Small-Craft Harbors, Breakwaters, and Fish Processing Plants
By their very nature, such facilities need to be located near the water's
edge. In Atlantic Canada alone, there are over 1,000 small-craft harbors, over
100 federal government wharves, 13 ferry terminals, 21 marine service centers,
and over 500 fish-processing plants.
The routine maintenance and replacement of wharves probably could be planned
to take into account higher sea level. Wharves will definitely need to be
raised. Old Federal wharves, for example, are only 1 meter above normal high
tides, but newer wharves are meters higher. Fish plants would have to be moved
further inland or somehow modified to keep the work areas dry. For small-craft
harbors, a rising sea would (at least slightly) reduce maintenance dredging
requirements.
On the other hand, changes in currents, circulation, wave and ice patterns,
river deposition, and the resulting changes in shoreline erosion patterns could
more than offset such savings. Site-specific assessments and engineering studies
would be needed. Not only might breakwaters have to be raised to afford better
storm protection from higher seas, but their location and configuration might
need to be changed to adapt to new wave refraction patterns and changes in the
way rivers deposit sediment.
Roads, Bridges and Causeways
Canada has an extensive network of roads, small bridges, and causeways
throughout its coastal region. Many of these structures would be vulnerable to
a one-meter sea level rise. The corrective measures would include relocating
or raising roads, reinforcing and raising causeways, and raising bridges -- all
at a cost significantly greater than normal maintenance costs. Some major new
causeways are at the planning stage -- e.g, the causeway to Prince Edward Island
-- but proper planning can allow for higher sea level and changing ice regimes.
Erosion
Coastal erosion is a problem in many parts of Canada, especially on the
east coast (Figure 3). In some cases, shores are retreating as much as 5 meters
each year. Sea level rise is generally expected to aggravate the problem.
However, the actual response of vulnerable shorelines will also depend on changes
to wind and wave patterns, currents, the geology and geomorphology, the ice
regime, local land subsidence, and sediment supply limitations. Our ability to
predict the timing and magnitude of changes to erosion patterns will require
further research on a site-specific basis. Realistically, however, the
implementation of shoreline protection measures will only be economically
feasible for those areas where the value of the shoreline investment is
sufficiently high, such as residential and recreational developments, harbors,
power plants, and other infrastructure.
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Figure 3. Accelerated erosion can be expected in places where an increase in
mean sea level would allow wave-induced erosion to attack vulnerable cliffs
instead of dissipating on the beach, as in this area at the head of the Bay of
Fundy.
Tidal Power
One of the more interesting coastal development concepts in Canada is that
of tidal power in the Bay of Fundy, where the tidal range is as much as 10-12
meters in some locations. From numerical models, it has been calculated that
an increase of 1 meter in sea level at the ocean entrance (Georges Bank) would
increase the tidal range at the head of the bay by about 1.7% -- that is, by 20
centimeters. Therefore, the height of the tidal power barrage would need to be
raised by about 1.2 meters. Fortunately, the increase in tidal range also
results in greater power output, so that if development proceeds, the increased
cost of engineering and construction will be roughly balanced by the increased
revenues from power generation.
Estuaries
The question of impacts in our estuaries has not generally been resolved
and requires further research and site-specific studies. In general, one would
expect a rise in sea level to extend partway upstream, which would raise water
levels and salinities. However, water levels will also be directly controlled
by the extent of river outflows and ice cover. Outflows will vary from one part
of the country to another and require accurate predictions of temperature and
precipitation.
In the St. Lawrence River, a related concern is the expected lowering of
water levels in the Lower Great Lakes by 30-80 centimeters, which would decrease
the outflow of the St. Lawrence River by 20%. This, in turn, would not likely
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decrease water levels in the river. The net result of these complexities,
including crustal movements, is considerable uncertainty in the expected rise
or fall of sea level in our estuaries, and it is too soon to design adaptive
strategies. Much more basic and site-specific hydraulic research needs to be
conducted before we even know what conditions we need to adapt to. (Note: The
drop in lake levels is independent of sea level rise, and is generally, expected
to result from increased evaporation at higher temperatures).
Agricultural Lowlands
A small percentage of Canada's agricultural production takes place near
the ocean shoreline, primarily in the Fraser River delta and in low-lying lands
on the east coast. Many of these areas are already diked, and they also have
"aboiteaux," which are essentially tidal gates that allow water to drain from
these lands during low tide. The solution to combat sea level rise will be to
gradually increase the height and extent of these structures. Moreover, new
dikes and weirs may need to be built along the shores of the Fraser and St.
Lawrence Rivers as rises in sea level extend farther upstream.
Marshes, Wetlands, and Wildlife Habitat
The key areas that may be affected are easy to identify and are located
mainly in the major estuaries and deltas (the Fraser, St. Lawrence, MacKenzie
Rivers) and low-lying lands along the southern shores of Hudson Bay and on the
east coast. However, the impacts are not so easy to predict.
No doubt, a sea level rise will inundate parts of these habitats. But
where topographic gradients permit, and if sea level changes slowly enough, these
productive systems will hopefully reestablish themselves farther up the
shoreline, and various biological species and their food supplies will recolonize
or adapt to their new surroundings. It is also possible that such habitat may
not be reestablished. For large remote areas, such as Hudson Bay, it is very
likely that no adaptive options are practical, except to allow nature to run
its course. For less remote areas, critical habitat might be replaced by manmade
development of new habitat at nearby locations, but at considerable effort and
cost.
For some fish and other species of economic importance, new habitat is
already being created as part of a Fish Habitat Management Policy, which strives
to achieve no net loss of natural habitat. On the west coast of Canada,
significant amounts of new habitat for salmon have been created by planting eel
grass in several major salmon estuaries. Further habitat development is a
practical means of mitigating losses of salmon and trout habitat from sea level
rise in estuaries and rivers.
Economic approaches also exist to replace lost production of certain
economically valuable fish species that spawn or grow in estuaries and the
nearshore. Salmon are being produced on a large scale through artificial
enhancement, in which eggs from wild fish are recovered during the spawning
season and grown in temperature-controlled hatcheries to an appropriate size
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before being released to the sea. This approach does not resolve the habitat
problem per se, but it does contribute to sustainable development and economics.
Another solution to the economic problem is commercial aquaculture. In
Canada, a considerable aquaculture industry has developed over the past decade,
mainly for salmon, oysters, and mussels. The industry's value has grown from
$13 million in 1982 to $100 million in 1988, mainly on the Pacific coast, and
further major expansion, especially to the east coast, is projected. Clearly,
there is an economic opportunity here that can also assist in mitigating the
effects of rising sea level.
Finally, it must be noted that the key climate issue facing fisheries in
Canada is not sea level rise, but the changes in water temperatures, circulation
patterns, wind-induced upwelling, and other factors that will determine the
future distribution, recruitment, and production of fish. This has major
implications for national and international resource management strategies and
agreements, fishing industrial strategies, and regional economics. (See
Everett, Volume 1, for additional discussion of response strategies to protect
fisheries).
FUTURE ACTION
From a coastal zone management point of view, a considerable degree of
skepticism exists in Canada regarding the risk of sea level rise over the next
few decades and beyond. It must be recognized that while research and
understanding of climate change takes place at national and international levels,
a large part of the decision making to mitigate local and regional effects takes
place at the local or regional level of government. At what stage of research
and assessment will there be sufficient knowledge and understanding to encourage
or persuade natural resource managers and local officials to actually allow for
higher sea levels in planning for habitat management and protection; for the
owners of real estate and infrastructure in the coastal zone to actually spend
money to floodproof existing buildings or to invest in diking and other
protective measures, or to make the increased investment in planned coastal
works needed to avoid future flooding, or even to ensure that rising sea level
is taken into account in existing coastal planning and decision making processes?
Whatever that point of credibility may be, it is clear that we are still far from
reaching that point.
Where, then, do we go from here? I believe that the following actions are
needed:
Continue research on global climate change to reduce current
uncertainties in the prediction of sea level rise resulting from global
warming.
Encourage further research and monitoring related to sea level change,
which must include the contribution of vertical movements of the Earth's
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crust and groundwater depletion to relative sea level change as well as
global warming effects.
Develop regional models for climate change, and carry out
multidisciplinary site-specific studies that integrate all the factors
that influence net changes to water levels in estuarine and coastal
areas, including interactions among precipitation and runoff, tides, ice
cover, crustal movements, erosion, sedimentation, storm surges, and
waves.
• Improve the scientific understanding of marine coastal ecosystems in
order to conduct ecological impact assessments related to rising sea
level.
Develop detailed inventories and mapping of coastal infrastructure and
natural resources in areas potentially affected by changes in sea level,
in order to facilitate improved impact assessments.
Continue research into coastal geomorphology and sedimentology in order
to understand coastal erosion processes, to predict the impacts of
higher sea levels, and to develop adaptive strategies.
Encourage multidisciplinary impacts research related to sea level.
Encourage the innovation and development of adaptive options.
Facilitate the public dissemination of information and research results
relating to sea level rise.
Encourage those involved with coastal zone management, building
standards/codes, property zoning, and sustainable development planning
to take into account the future possibilities for rising sea levels.
Development of flood-prone lands must be discouraged, by legal
prohibition if necessary.
BIBLIOGRAPHY
Anon. 1989. The full range of responses to anticipated climatic change. United
Nations Environment Program and Beijer Institute, April.
Forbes, L.B., R.B. Taylor, and J. Shaw. 1989. Shorelines and rising sea levels
in eastern Canada," EPISODES, Vol. 12, No. 1, p. 23-28.
Lane, P. et al. 1988. Preliminary study of the possible impacts of a one-meter
rise in sea level at Charlottetown, Prince Edward Island. Climate Change Digest,
Report No. CCD 88-02, Environment Canada, Ottawa, Canada.
Martec Limited. 1987. Effects of a one-meter rise in mean sea level at Saint
John, New Brunswick and the lower reaches of the Saint John River. Climate
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Change Digest, Report No. CCD 87-04, Environment Canada, Ottawa, Canada.
Sanderson, M. 1987. Implications of climatic change for navigation and power
generation in the Great'Lakes. Climate Change Digest, Report No. CCD 87-03,
Environment Canada, Ottawa, Canada.
Scott, D.B., and D.A. Greenberg. 1983. Relative sea level rise and tidal
development in the Fundy Tidal System. Canadian Journal of Earth Sciences,
20(10):1554-1564.
Smith, J.V. 1989. Possible impacts of mean sea level rise scenarios on downtown
Vancouver. Unpublished manuscript prepared for Atmospheric Environment Service,
University of Waterloo, Ontario, Canada.
Stokoe, P. 1988. Socioeconomic assessment of the physical and ecological
impacts of climate change on the marine environment of the Atlantic region of
Canada - Phase 1. Climate Change Digest, Report No. CCD 88-07, Environment
Canada, Ottawa, Canada.
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THE LOWLANDS OF THE MEXICAN GULF COAST
MARIO ARTURO ORTIZ PEREZ
CARMEN VALVERDE
Institute de Geografia
Universidad Nacional Autonoma de Mexico
Mexico City, Mexico
NORBERT P. PSUTY
Center for Coastal & Environmental Studies
Rutgers - The State University of New Jersey
New Brunswick, New Jersey
LUIS M. MITRE
Institute de Geologia
Universidad Nacional Autonoma de Mexico
Mexico City, Mexico
ABSTRACT
Mexico's Gulf of Mexico coast is largely lowland subject to a large range
of marine influences. Of six large lowland areas that are subject to relative
widespread flooding, four are within deltaic systems.
The coastal zone has been undergoing considerable change as a result of port
development related to the extraction of oil and to the concentration of oil
refineries and petrochemical plants. This area has also undergone a great
expansion of commercial agriculture, cattle ranching, and high-cost tourist
development.
There are, at present, many conflicts between the development interests and
the local economies based on the coastal resources. The intensity of
exploitation is currently causing serious deterioration of the environment, which
is produced by a combination of the cultural processes superimposed on the
natural changes. The losses of marshlands, mangroves, and other aspects of the
coastal aquatic system are problems that need to be addressed. Although attempts
have been made to control some of the changes by constructing coastal protection
devices, these "solutions" have been neither well-planned nor successful. An
awareness of the dynamics of the coastal system and the changes driven by a
rising sea level must be introduced into the decisionmaking process.
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INTRODUCTION
Approximately two million Mexicans live within five meters above sea level.
Although a one-meter rise would inundate only a fraction of the nation's coastal
zone, it would threaten some of the most valuable land, including tourist
resorts, port facilities, and the wetlands that support an important fishing
industry.
The intent of this paper is to summarize the present state of knowledge
concerning the physiographic information, the wetland areas, and the
socioeconomic aspects of the Mexican Gulf Coast and to identify some of the
impacts to the system as a result of a future sea level rise.
IMPACTS OF SEA LEVEL RISE
Physical Effects
Sea level rise particularly threatens the barrier islands along the Gulf of
Mexico; as sea level rises, they will gradually narrow and some will shift
inland. The islands in front of the southern portion of the Laguna Madre will
certainly shift landward, and additional inlets are likely to form, further
segmenting these islands. On the other hand, the barrier in front of the
Tamiahua Lagoon will narrow at first, although it will eventually break up as
well.
The high, dune-lined barrier islands near Veracruz, Alvarado, and
Coatzacoalcos have sufficient size and mass to resist erosion, at least in the
early years. There will be some loss of sediment and there will be a slight
shift of the beach into the dune zone, but the effects will be limited. Along
the Tabasco-Campeche barrier system, the effects will vary: In western Tabasco,
the barriers in front of most of the smaller lagoons will be removed by overwash
and breaching, creating a very indented shoreline. The area from Tupilco,
Tabasco, to Champoton, Campeche, is very low but very wide. Along this segment,
the coast will erode at a very rapid rate as sea level reaches to higher levels
and removes sediment from the low-lying beach ridges. The oil port of Dos Bocas
will be increasingly exposed to storm effects and breaching of the jetties and
shore protection structures.
The very narrow barrier along the Yucatan Peninsula will diminish greatly
in size and probably break up. The salt-evaporation ponds at Progresso will be
threatened as they are initially overtopped by inundation with higher sea level
and then erosion as they become exposed to wave attack. The barrier island at
Cancun will become every narrower and more liable to storm damage as sea level
rises, thus threatening all existing and future infrastructure.
Mexico's wetlands would also be vulnerable to a rise in sea level,
especially given the impacts of economic development. Their inundation would
normally be balanced by an upward growth as organic and inorganic matter
accumulates to a new level. The problem of sea level rise is compounded in
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Mexico because nearly all of the major rivers leading to the vast wetland areas
are dammed and the sediment supply has been attenuated for decades. The product
of the sea level rise and a decreasing sediment supply will lead to a loss of
wetland area and a loss of primary productivity of the wetlands, the estuaries,
and the adjacent nearshore areas. This could lead to serious deterioration of
the local fisheries industries, independent of problems of pollution and
overfishing.
The wetlands of Laguna Madre and the Tamiahua Lagoon have already shown the
effects of a limited sediment supply. Their bordering wetlands are very narrow.
The Alvarado Lagoon and the Papaloapan lowlands will show a considerable change
both as a result of the higher water level and the severe loss of sediment supply
coming into the estuary.
The Grijalva lowlands will be the most seriously affected because it is the
largest wetland area in Mexico and because of local subsidence and sediment
starvation associated with the Malpaso Dam. Wetlands are already migrating onto
the slightly higher coastal beach ridges and sand dune topography, while the
bodies of open water are increasing and the shoreline is migration inland. The
new population centers there and the petroleum industry will be affected as the
water table rises and it becomes more difficult to drain the surface water off
the land and lead the sewage away.
Socioeconomic Implications
Port activity could be affected by the sea level rise, especially in areas
where the infrastructure is essentially at beach level, such as at Campeche,
Ciudad del Carmen, Frontera, Dos Bocas, and parts of Coatzacoalcos and Veracruz.
In Carmen, Frontera, and Dos Bocas, there is no higher ground to accommodate a
landward retreat. The landscape is only a few meters above sea level and any
increase will expose these sites to greater storm damage.
Much of the lowland is used for some type of economic activity. Oil
exploration is certainly a common use throughout much of the coastal plain, and
it is especially prevalent in the Tabasco lowlands. In addition, cattle pasture,
coconut plantations, cacao, maize, sugarcane, lumbering, and fishing are
important economic pursuits. With the exception of fishing, all of the other
economic activities will be adversely affected by a higher sea level because of
the changing salinities and water table. Whereas the entire area will not be
affected uniformly, the net effect will be a loss of surface area where each of
these economic activities can be practiced. The petroleum industry will be able
to conduct its exploration phase despite sea level rise. However, some of the
stationary infrastructure may be negatively affected as shoreline erosion or
higher water levels begin to encroach upon these structures.
Responses
One can reasonably expect that revenue-producing activities such as tourist
beaches, ports, and petroleum activities will be protected with traditional
coastal engineering measures. The casualties in this process will almost
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certainly be the environment and people pursuing traditional activities who lack
the necessary resources to hold back the sea.
The coastal environment in Mexico is currently being exploited in manners
likely to have an adverse impact in the long run. If we are unable to adequately
address current environmental problems, how can we prepare for consequences of
a rise in sea level that is still decades away?
Nevertheless, Mexico does have institutions that are capable of planning for
the future, provided that the actions do not substantially undermine economic
growth. In this regard, it seems wise to direct future coastal development to
areas that are at least three meters above sea level; not only would this prevent
future environmental impacts, but it would leave these areas less vulnerable to
flooding even in the short term. Similarly, along the ocean coasts, tourist
facilities should be set back from the shore; this would make them less
vulnerable to hurricanes and would enable the beach to survive accelerated sea
level rise.
But perhaps the most important first step in planning for sea level rise
would be increased awareness on the part of the public in general and
governmental officials in particular. Information transfer is a slow process.
This is an area where researchers and universities can play an important role,
rather than being outside observers and critics of governmental processes. The
scientists and economists in Mexico need to begin discussing the implications
of global climate change, so that we can better inform the policy makers of
possible responses.
We note in particular that the Sea Grant College programs of California and
Texas are interested in collaboration with Mexican scientists. We strongly urge
these organizations to collaborate with the relevant Mexican Universities on the
issue of sea level rise, with the goal of a bilateral conference on sea level
rise similar to the Miami conference but focused on the common coastal problems
facing states on either side of the U.S./Mexican border.
THE COASTAL ENVIRONMENT OF MEXICO
Coastal Geomorphology
The Mexican coast on the Gulf of Mexico has a length of approximately 2,500
km. The coastal plain has a width varying from 30 to 150 km. The coastal relief
generally is even and low, being traversed by more than 25 important rivers and
incorporating 23 coastal lagoons of very different sizes. The coastal inlets
are very important owing to the different transitions between the barrier
islands, river mouths, and deltas, linking floodplains, lagoons, marshes, swamps,
and mangroves.
The rocky coasts appear in short sections and are of low altitude; some
are composed of compact volcanic rocks forming isolated promontories on the
general coastal outline. On the Caribbean margin, the coast is rectilinear and
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rocky with short sections of indented configuration. Escarpments are low and
formed in calcareous rocks incorporating a narrow abrasion and accumulation
platform, isolated from the open sea by a coral barrier.
The predominant types of coast are sandy beaches (1,629 km), followed by the
swampy coast and marshes (389 km), very important around the estuaries and
lagoons; the rocky coast has a length of 382 km.
Climate
The regional climatic characteristics of the Mexican Gulf Coast are the
dominant pluviometric system and the yearly temperature distribution (Garcia,
1989). Garcia divides these elements into three broad zones that from north to
south are as follows:
• The Tamaulipas northern coast, which is hot and arid, characterized by
temperatures higher than 18°C during all the year, with a yearly rainfall
of less than 800 km. Seasonally, it has an extreme climate, with a
yearly thermal range of more than 14°C. During the winter it receives
cold wind masses and during summer torrential rains associated with
cyclones or tropical storms.
• The central part of the littoral is subhumid toward the north and humid
at the south, with an average yearly temperature that varies from 22°C
to 26°C and a yearly rainfall between 1,000 and 1,500 mm, increasing to
the south. During the winter the coast receives north winds, that is,
cold wind masses, and during autumn, the easterly tropical waves are
common. The rest of the year the trade winds are dominant.
• The southeast section comprises the complete Yucatan Peninsula. It has
a circulation system similar to the above, with the exception of the
temporary stationary high pressure cell over the south-central section
of the gulf. The high pressure cell is responsible for a series of
climatic zones that vary from a dry semi arid condition at the northwest
end of the peninsula to a subhumid climate toward the south and
southwest interior.
The gulf is a favorable area for tropical cyclones and their accompanying
floods and storm tides (Jauregui, 1967). Almost 35% of the cyclones originating
in the Caribbean Sea touch or cross the Mexican coasts. Winters contribute storm
waves caused by the north winds, in addition to the frontal rains and orographic
rainfall created when the humid air masses collide with the slope of the Sierra
Madre.
Waves and Currents
Three types of wave regimes are found at the Gulf of Mexico and the
Caribbean coast (Lankford, 1977):
• waves and storm surge associated with the tropical cyclones;
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• waves and storm surge associated with the movement of polar wind masses
known in Mexico as north winds (Nortes); and
• waves and wind surge that is generated within the limited fetch of the
gulf basin.
The dominant winds show a preference for directions from the northeast,
east, and southeast quadrants. The wind waves typically have short periods of
between 5 and 7 seconds, and the average heights are of 2.3, 2.3, and 1.4 m from
the northwest, north, and northeast, respectively (Lankford, 1977). In general
terms they can be considered as intermediate to low energy waves, except for the
north wind and hurricane situations, where waves of more than 4.5 m have been
observed.
The hurricanes occur in the summer, causing intense storms. The cyclonic
paths show a preference in their course for the Yucatan Peninsula and its
platform, crossing it, and more frequently approaching the northwest coast than
the southwest coast.
The Nortes develop between October and February. Each year between 15 and
20 Norte events occur, each one with a duration of 1 to 5 days. It is frequent
that they exceed 100 km/hr, creating storm tides that inundate lowlands, erode
the shores, and transfer sediment in numerous directions. There is a movement
of sands in the dune fields, with an orientation from north to south, prograding
the coastal lagoons to the lee.
Cultural and Economic Features
Demography
The coastal zone of the Gulf of Mexico is shared by six states of the
Federation: Tamaulipas, Veracruz, Tabasco, Campeche, Yucatan, and Quintana Roo,
with a total of 57 municipalities which together in 1980 had a population of 2.8
million, representing the 4.1% of the total population of the country (Table 1).
Even though the Gulf of Mexico coastal zone has a long tradition of human
settlement, at present it does not have a dense population. In recent decades
there is a slight tendency toward an increasing population, especially in the
urban areas. In the year 2000, it is estimated that the coastal zone will record
a population of 4.5 million inhabitants, that is, 4.7% of the total population
of the country.
Distribution of Human Settlements
Of the 2.8 million coastal inhabitants in 1980, 70% lived at an altitude
between 1 m and 5 m, mainly along the coast or at river borders very near their
mouths. About 60% of the coastal population reside in cities (Table 2); 44.9%
live in cities with more than 100,000 inhabitants.
474
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Ortiz, et al.
Table 1. Total Population of Mexico and the Gulf of Mexico Coastal States and
of the Coastal Zone, 1960-2000
Area 1960 1970 1980 1990 2000
Country 34,923,129 48,377,363 66,846,833 78,140,006 1,802,174
Coastal States 5,080,858 7,138,668 10,090,396 1,244,617 14,950,947
% Total Country 14.55 14.76 15.09 15.93 16.29
Coastal Zone 1,236,269 1,864,189 2,792,613 3,526,055 4,303,529
% Total Country 3.54 3.85 4.18 4.51 4.69
% Total Coastal States 24.33 26.11 27.68 28.33 28.78
Source:Censos Generales de Poblacion (1960, 1970, 1980).
Table 2. Distribution of the Coastal Zone Population by Size of the Settlement,
1980 (Size of the settlement by number of inhabitants)
1-999 1,000- 15,000- 20,000- more than Total
14,999 19,999 99,999 100,000
No. of villages
(%)
Total Population
(%)
5,129
96.0
572,937
20.8
194
3.6
540,510
19.7
3
0.06
54,391
2.0
8
0.02
345,597
12.6
6
0.1
1,236,337
44.9
5,341
100.0
2,749,772
100.0
Source: General Population Census (1980).
Cities
In general, all the states that constitute the gulf coastal zone have
important cities (Table 3). There are other smaller cities that during the last
decades have obtained great importance, registering a high rate of demographic
growth, such as Ciudad del Carmen in Campeche and Cancun in Quintana Roo.
Most of the cities with more than 15,000 inhabitants perform harbor
functions; included here are the largest with the exception of Matamoros.
Port Facilities
The region has 56 ports, of which 17 are sea ports and the rest are fluvial
ports. Major ports are located in the States of Tamaulipas, Veracruz, Tabasco,
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Table 3. Population of the Cities With More Than 15,000 Inhabitants, 1960-2000
City
1950
1960
1970
1980
1990
2000
Campeche
Carmen
Cancim"
Chetumal
Cozumel
Tamp i co
Matamoros
Veracruz
Coatzacoalcos
Minatitlan
Tuxpan
Alvarado
Panuco
Gtz. Zamora
Progreso
31272
11603
43874
21164
69506
34656
128434
72489
147551
84016
179263
103631
33273(5)
7247
2332
94345
45846
101221
19501
22455
16096
8840
6615
4480
13339
12855
2915
124894
92327
153705
37300
34350
23262
12548
8818
6518
17060
23685
5858
185059
137749
230220
69753
68397
33901
15792
14277
9099
21352
56709
19044
267957
188745
305456
186129
145268
56037
22633
26652
15037
30183
64928
20807
313314
234697
415456
211255
168239
64940
26109
30483
17347
34190
80850
26115
371414
282108
511678
264489
208388
77986
30571
37040
20772
39672
Source: General Population Census (1950, 1960, 1970, 1980).
alt was not possible to make a projection of the Cancun population, because it
is of recent creation and has no population register for the period 1950-1970.
and on the coast of the Yucatan Peninsula. The gulf coastal zone is important
because of the petroleum industry, both in production as well as in processing.
From the coastal zone of Tamaulipas, Veracruz, Tabasco, and Campeche is extracted
most of the Mexican oil. In 1985 the zone had 370 fields (S.P.P. 1986, p. 88-
110). The processing industry is represented by petrochemical refineries. The
most important petrochemical complex is Coatzacoalcos-Pajaritos-Minatitlan-
Cosoleacaque-Cangrejera; it is primarily located along the lower Coatzacoalcos
River. The complex has 33 petrochemical plants: 12 in Cosoleacaque, 11 in
Minatitlan, 13 in Pajaritos, and 21 in Cangrejera. It also has a refinery in
Minatitlan, with a capacity of 258 thousand barrels per day.
In 1985, this complex, together with the one at Ciudad Madero, also located
in the gulf coastal zone, had the highest production in the country. The
production obtained was 968 million barrels of crude oil and 1,186,667 million
cubic feet of natural gas (S.P.P. 1986, p.47), representing 98.1% and 90.2%,
respectively, of the total production in the country. With regard to
petrochemicals, in 1984 the production of refined oil was 200 million barrels
and petrochemicals amounted to 8.5 million metric tons; that is 41% and 74% of
the yield in the country.
Equally important is the oil-line and gas-line net in the State of Tabasco
that starts at the Sonda de Campeche with a terminal at the port of Dos Bocas.
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Ortiz, et a/.
Also, Campeche has the majority of maritime production platforms in the Gulf of
Mexico, with a total of 48 (Ecodevelopment, 1988).
Recently the first nuclear electric plant at Laguna Verde started to
function. It is located on the Veracruz coast 70 km northeast of Veracruz. The
plant has two units, each one with a capacity of 654,000 kilowatts.
Even though the gulf coastal zone and the Mexican Caribbean have had an
uneven touristic development, it is important to point out the touristic
installations exist in some points of this region. Located in the Caribbean,
Cancun is the principal touristic node. In only one decade it has risen to
become the most important tourist site in the country. Its development has been
totally planned. It was principally created to satisfy an international demand.
In 1988 it was able to offer lodging in 9,520 rooms.
Veracruz and Cozumel are also considered to be important touristic centers.
In 1988 they were able to offer 4,400 and 2,320 rooms respectively. Veracruz
covers principally the demand for national tourism, while Cozumel is important
for international tourism.
The ports and installations mentioned having the greatest exposure to
effects caused by the sea level increase are Tampico, Alvarado, Coatzacoalcos,
Dos Bocas, Frontera, and Ciudad del Carmen. Each has an altitude that varies
between 0 and 3 meters.
LAND USE
At the coastal zone, the combination of different elements of the hydrologic
cycle creates two great natural systems: (1) the coastal lands system and (2)
the coastal waters system (Toledo, 1984); both are highly productive.
Use of the Land of the Coastal System
The use of the land (Table 4) of the first mentioned systems, the coastal
lands, can also be divided in two: (1) one of natural origin and (2) the other
introduced by man.
In the Tamaulipas coastal strip, dry shrub vegetation is dominant. Forest
cover is located in well-defined areas, presenting some variants depending of
the rainfall requirements. A small portion at the northwest and north of the
Yucatan Peninsula completely lacks vegetation.
Among the land uses introduced by man, one is extensive cattle raising that
takes great advantage of the natural pasture characteristic of the zones. New
pastures that have technically modified some ecosystems as the forest have also
been introduced. The use of the land for natural and induced pasture covers the
largest surface area (25%) of the coastal zone. Most of the cattle production
in the zone is destined for the internal market, principally in the central part
of the country.
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Table 4. Use of the Land in the Coastal Zone of the Gulf of Mexico
Use of the Land
Surface in km2
Partial Total
Percentage
Partial Total
Pasture ground
Bush 6257
Tamaulipas Bush 375
Mesquite 1278
Rosettophyle Bush 1809
Cacicuale Bush 2795
Forest
Low Perennifoil 979
High Subperennifoil 7335
Medium Subperennifoil 1118
Low Subperennifoil 1558
Savanna
Mangrove
Tular and popal
12167
10011
4365
4504
5685
0.8
2.6
3.8
5.7
2.0
15.0
2.3
3.2
25.0
12.9
22.5
8.9
9.2
11.6
Agriculture
Temporal
Irrigation
Without irrigation
Total
3472
1070
316
48826
4542 9.3
7.1
2.2
0.6
100.0
Of less importance is the use of the agricultural land in its two forms,
natural and irrigated. For the latter, the most important zone is located at
the north of the coastal region (Tamaulipas) near the U.S. border, principally
dedicated to the cultivation of cereals. In non-irrigated agriculture, the
commercial monocultivation plantings (sugarcane and bananas) are located
principally in Veracruz and Tabasco.
Use of the Coastal Waters System
The water system is one of the most important systems in the coastal zone
for its fragility as well as for its ecologic conditions, and because it is
highly productive. It can be divided into two subsystems, both intimately tied
478
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Ortiz, et al.
through physiographic and ecologic processes in a way that -- on one hand --
there is the vegetation typical of the system (mangrove, Tular, and Popal) and
--on the other hand -- there are the waters.
The mangrove is principally limited at the border of the coastal lagoons and
in the mouths of the rivers. The most important associations are located in the
Tabasco and Campeche littorals. The red mangrove is characteristic of this
community, reaching heights up to 25 meters; it is used for marine construction
and in the manufacture of charcoal (Ecodevelopment Center, 1988).
The Popal, or marsh, consists of an association of hydrophytes, including
Thalia, Cyperus, Colathea. and Heliconia. Very often, it is found together with
tulares. The greatest extension of this type of vegetation is located at the
south of Veracruz and in Tabasco. Commonly it is burned during the dry season
to take advantage of the land for cultivation.
Economic Importance of the Coastal Zone
The Gulf of Mexico coastal zone has played an important part in the
development of the country. At the beginning of the 20th century, it was
distinguished for plantation agriculture (sugarcane, banana, and sisal, among
others). Later, it acquired importance for commercial cattle raising,
principally for the internal markets. During the last decades, the oil industry
has become the most relevant economic activity. It is important to point out
that the coastal states (Tamaulipas, Veracruz, Tabasco, Campeche, Yucatan, and
Quintana Roo) contribute 14.7% of the gross internal product of the country, and
the coastal zone contributes 3.9%.
At present, plantation agriculture is still the most important in the
coastal zone (INEGI, 1985). The region contributes 47.3% of the sugar production
in the country. Of importance is the irrigation agriculture, especially in the
coastal plain of the State of Tamaulipas that produced 41.5% of the national
sorghum that year.
Cattle raising has been acquiring great importance, principally the breeding
of bovine cattle. The region had 26.4% of the national production of this type
of cattle in 1983. But, undoubtedly, the oil industry has distinguished this
region for its crude production as well as for petrochemicals (see industrial
installations).
FISHING
The Gulf of Mexico and the Caribbean coastal zone with its 2805 km of
coastline, its 771,500 km2 of exclusive economic zone, and a broad continental
shelf, represent a significant fishing zone, even though not the most important
in the country. Outstanding within the region are the Campeche sound and some
tropical fisheries.
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Fishing in the region, even though limited principally to the littoral zone,
including the coastal lagoon systems, is also carried out in the shelf. The
State of Campeche has excelled in this type of fishing. As a whole, the zone
had a 1983 production of 275,493 tons (INEGI, 1985).
When studying the fisheries of the region, great differences are noted
between the Gulf of Mexico and the Caribbean. The first presents a sustained
production, carried out principally on the continental platform. In 1983, it
registered a value of production of 3,842,141 million pesos. The most important
species captured are shrimp, oyster, clam, crab, sea fish, mullet, and snook.
In the Caribbean zone, even though the fishing activity is not so important, some
fisheries have developed that have economic importance (snail and lobster). The
value of the fishing production of the zone represented in 1983 a value of 7576.5
million pesos. Among the fisheries of the region, the most important are the
following:
Shrimp
Shrimp represent a great economic value, and a considerable part of the
production is exported. Shrimp from the Gulf of Mexico have a benthic habitat;
they are distributed from the littoral lagoons up to 200 meters depth on the
continental platform (Ecodevelopment, 1988). According to the catch figures
for 1985, the Gulf of Mexico littoral contributed 25,149 tons, which represented
33.8% of the national production (Secretaria de Pesca, 1977). In 1984, 100
shrimp cooperatives were registered, with bigger vessels destined to catch shrimp
in the open sea. Seventy-nine cooperatives shrimped in the estuaries and
lagoons. The former reported 76.9% of the shrimp production and the latter 23.1%
(op.cit.). Most of the estuary shrimp are obtained at Laguna Madre and Tamiahua
Lagoon (97.2%).
Oysters
The oyster resource commercially exploited in the Gulf of Mexico's littoral
is principally the sand bank oyster or American oyster (Crassostrea virqinica)
and, of less importance, the mangle oyster (Crassostrea rhizophora).
The oyster fisheries that have developed in the Gulf of Mexico's littoral
are the most important in the country; 96% of the national production originates
from them. The principal oyster fisheries are located in the following coastal
lagoons: Laguna Madre, Laguna de Pueblo Viejo, Tamiahua, Lagunas Carmen and
Machona, and Laguna de Terminos.
In the Gulf of Mexico, 52 cooperative societies exploit the oyster, but only
11 of them register 80% of the total production. Together, the 52 cooperatives
employ approximately 15,000 fishermen.
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Ortiz, et al.
GOVERNMENTAL RESPONSES TO COASTAL ENVIRONMENTAL PROBLEMS
Social Context
The developing countries present numerous problems, which in some instances
become more serious because of the inadequate handling of the resources they
have. A clear example of this situation are the Mexican shores of the Gulf of
Mexico and the Caribbean.
Recently, the region has registered a remarkable economic growth. Going
from an almost isolated rural region, commercial cattle raising, tropical
plantations, the petroleum activity, and tourism have dramatically altered the
landscape.
One can question whether these changes have been for the better. The
development of the region has often proceeded as if the only objective is to
maximize current revenues without regard for the future. The economic growth
of the region has had high social and environmental costs. Toledo (1984), for
example, argues that petroleum exploitation is responsible for a substantial
degradation of the environment. Similarly, the extensive growth of cattle
raising and agriculture has been at the expense of the natural vegetation.
Even though the area has registered an accelerated economic growth, much of
the population receives no benefit; many people are economically marginal,
performing economic activities in the traditional way, in large part because the
people inhabiting the coastal regions are not trained to compete within the new
labor markets. Yet the introduction of the new economical activities has greatly
altered their standard of living.
Another aspect that characterizes the urban development of the region is
the spontaneous settlements, principally inhabited by people left behind by
economic development. Nolasco (1979) estimates that for the year 1990,
Coatzacoalcos and Minatitlan will have a "marginal" population of 182,488 and
123,931 inhabitants, respectively, representing 86% and 73% of the total
population. This enormous population is not only marginal socially and
economically within the urban space, but it is spatially relegated to those
places with the most adverse physical conditions for urbanization, potentially
the most exposed to the negative effects of sea level rise.
Environmental Regulation
Given the threat to coastal environments, Mexico has taken some measures
-- but because they were started too late, they have a corrective more than a
preventive character.
One of the first actions was the Federal Law to Prevent and Control
Environmental Pollution, issued in 1971. For the first time, the Mexican
Legislature considered the importance of controlling the environmental
deterioration and created offices to enforce environmental laws.
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North America
However, it was not until 1980 that important steps were taken to protect,
the environment. In 1981, the Public Works Law was issued, which required those
planning the construction of buildings to consider the environmental impact.
In 1982, the Federal Protection of the Environment Law entered into effect
and with it important advances were obtained, even though the scope was confined
to controlling air and water pollution. In 1988, the General Law of Ecologic
Balance and Environmental Protection brought remarkable changes in how Mexican
institutions conceptualized problem. Under this law, regulations have been
developed that focus on the entire ecology, considering conservation,
restoration, and improvement of the environment, as well as on the protection
of natural areas, flora, and fauna (wild and aquatic). Also, the new law refers
to the reasonable utilization of the natural elements, encouraging estimates of
the economic benefits of protecting ecosystems and preventing air, water, and
soil pollution.
This law defines "environmental impact" to include environmental
modification caused by human or natural action. Thus it would appear to require
consideration of sea level rise due both to natural factors and to the greenhouse
effect. Currently, implementation has centered only on the impacts of human
activities. Even under this more restrictive interpretation, however,
considering sea level rise appears to be required, since the environmental
implications of new projects will be different if sea level rises. The
Secretaria de Desarrollo Urbano y Ecologia (SEDUE)-Urban Development Ecology
Department is currently in charge of evaluating the environmental pollution.
At this point, one might ask who makes the decisions in the management of
the Mexican littoral zone. In accordance with Merino and Sorensen (1988), a
great number of jurisdictions and powers on the littoral are identified, but
unfortunately there is no integrating program for the coast.
Table 5 shows the many agencies involved in coastal zone management; the
vast majority of these offices are managed by the federal government. This
condition is one of the main difficulties confronted within a coastal zone in
carrying out integrated planning. Although the Committees in Charge of the
Planning and Development of the States (Coplades) theoretically carry out a
coordinated effort, a lack of administrative coordination is observed in
practice. The same condition is also observed among the federal agencies.
According to Merino (1988), there are five types of impediments to an
integrated management of the coast: (1) lack of proper identification of the
problem; (2) scant coordination among government agencies; (3) lack of economic
means; (4) lack of continuity and governmental inefficiency; and (5) improper
knowledge of resources and ecosystems. These problems apply to sea level rise
as well as to other coastal problems.
We would add two other impediments to that list. First, like most of the
other countries represented in this report, there is a lack of environmental
education and public awareness in Mexico of the implications of the many threats
to the ecology. Moreover, one must consider the environment within the context
482
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Ortiz, et al.
Table 5. Government Agencies With Powers or Mandates Over the Coastal Zone
Government
Level
Federal
Federal
Federal
Federal
Federal
Federal
Federal
Federal
Federal
Federal
State
Federal
State
Government
Agency
Secretariade
Programacion y
Presupuesto
Secretaria de Desarrollo
Urbano y Ecologia
Secretaria de Energia
Minus e Industria
Paraestatal
Secretaria dePesca
Secretaria de Marina
Abbreviation
SPP
SEDUE
English Name
Attributes
and Functions
SEMIP
SEPES
SM
Secretoria de Turismo SECTOR
Secretariade SCT
Comunicacidn y
Transporte
Secretariade SG
Gobernacion
Secretaria de Relaciones SRE
Secretaria de Agriculture
y Recursos Hidraulicos
Comit6s de Plancacidn
del los Estados
SARH
COPLADE
Gobiernos de los Estados —
Municipal Gobierno Municipal
Budget and Programming
Ministry
Urban Development and
Ecology Ministry
Energy, Mines and
State Industries
Ministry
Fishing Industry
Marine Ministry
Tourism Ministry
Communications
Transport Ministry
Ministry of the Interior
Ministry of Foreign
Affairs
Agriculture and Hydraulic
Resources Ministry
State Development
Planning Committees
(one for each State)
State Governments
Approval of plans and
budgets of other ministeries
Control of urban centers,
environmental regulations,
creation and management of
park and reserves, control over
the ZFMT.
Control over oil and mineral
extraction.
Fisheries regulation and
promotion.
Coastal and oceanic surveillance.
Contingency facing management.
Tourism promotion and
development plans in touristic
areas.
Construction and operation
of ports and navigation
services.
Control over islands and their
underwater platforms.
Permits and concessions on
foreign activities on the coastal
and Exclusive Economic Zones.
Control over fresh waters, dumps,
and river discharge.
Development planning for
the state, coordination between
federal and state governments.
General planning and definition
of the state priorities.
Municipal Governments Local actions and powers.
Table taken from Merino (1987).
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North America
of other priorities. Mexico has serious economic problems, and the attention
of policy makers is focused on activities that generate foreign exchange such
as oil production. Although this is a reasonable response to the financial
crisis, one must hot lose sight of the fact that people's well-being does not
depend on economic activities alone.
CONCLUSION
The gulf coastal plain is a very important part of the cultural, natural,
and economic base of the Mexican nation. It is already being affected by the
encroachment of the sea into the coastal plain. Some of the features can absorb
the changes and retain most of their characteristics, albeit after a landward
migration. However, many other features are suffering the many impacts of human
interference with natural processes, with pollution, and a deteriorating natural
system. The impacts of a rising sea level are yet another negative element that
has to be absorbed along with the others. The combination of sediment deficits,
subsidence, and coastal pollution is magnifying the effects of sea level rise.
The causes of the problem are not simple, nor will the solution be simple.
It will be difficult to command the attention of policy makers faced with more
pressing economic and social problems. Nevertheless, some preparation of sea
level rise and other consequences of global warming are clearly warranted. The
general history of environmental protection suggests that a problem must be
studies for years, sometimes decades, before governments can implement solutions.
Accordingly, the highest-priority response in Mexico should be for coastal
environmental scientists and engineers to begin exploring the possible
consequences. A major conference in Mexico on the topic is clearly warranted.
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Toledo, Alejandro. 1984. Como destruir el paraiso, El desastre ecologico del
Sureste, Centre de Ecodesarrollo, Mexico.
West, R.C., N.P. Psuty, and B.C. Thorn. 1969. The Tabasco Lowlands of
Southeastern Mexico. Coastal Studies Series. Baton Rouge, LA: Louisiana State
Univeristy Press.
Zavala, J. 1988. Regionalizacion natural de la zona petrolera de Tabasco,
Casos de Estudio, INEREB, Mexico.
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RAISING MIAMI -- A TEST OF POLITICAL WILL
TED MILLER
and
WILLIAM HYMAN
The Urban Institute
Washington, DC
ABSTRACT
Miami and the remainder of metropolitan Dade County are built on
extraordinarily porous water-bearing rock and sand, which lies 1.6 meters below
the surface, extends down to a depth of 45 meters, and extends out under the
ocean. Shallow dikes with supplemental pumping will not keep out a rising sea,
which simply would float the freshwater table up from below. Even though fill
can be strip-mined on publicly held local lands and transported to the area by
barge, if the sea level rose one meter, more than $600 million of public
investment would be required in Dade County to raise streets and improve canals,
drainage, and pumping, a sum equal to a 1% rise in the local capital budget for
the next 100 years. Landowners might incur additional costs to raise buildings.
Even if the investment were made, the county might be more vulnerable to
hurricane damage.
The cost estimates given here assume the streets will be raised as they
are reconstructed, roughly at 35-year intervals. If the county does not raise
streets in advance of sea level rise, costs incurred as a result of sea level
rise might be an order of magnitude higher. Increasing construction costs today
to raise streets above the levels of adjoining lots, however, for the sake of
future sea level rise will require a good deal of public education and foresight
from policymakers.
INTRODUCTION
This paper uses a case study of Miami to illustrate the likely impacts of
sea level rise on a major city. Specifically, we examine the impacts that global
climate change, coupled with sea level rise, could have on Dade County's water
control and drainage systems, building foundations, roads, bridges, airports,
sewage transport and treatment systems, and water supply.
Although it varies in actual practice, the nominal replacement cycle for
most infrastructure is 30 to 50 years; some water supply investments have 100-
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year lives. Because communities are essentially locked into capital stock for
a relatively long time, much of the present infrastructure could be vulnerable
to rapid climate change. Sea level rise, temperature change, and changes in
precipitation patterns, for example, all could alter the balance between water
supply and demand before much of a community's capital stock is due to be
replaced. The nature and pattern of precipitation could affect drainage
requirements, as well as highway design and maintenance. In addition, household
relocation in response to climate change could radically alter the population
growth projections on which capacity decisions about water, highway, and
wastewater treatment systems are based.
The uncertain, yet potentially imminent, impact of global climate change
already has increased the riskiness of infrastructure investment. Applying
design standards and extrapolating from historical data still might not provide
reasonable assurance that water and power supply, dam strength and capacity,
bridge underclearances, or storm sewerage capacity will be adequate given the
long lives of these facilities.
The National Flood Insurance Program's maps identifying the 100-year
floodplain and 500-year floodway will no longer be reliable as a basis for local
building and zoning ordinances designed to minimize flood losses.
Especially in coastal areas, the possibility of accelerated change in global
climate may soon require careful decisions regarding how and when to adapt the
infrastructure. Emphasizing life-cycle costing and upgrading during
reconstruction, in anticipation of future changes, could yield large, long-term
cost savings.
Corporate investment analysts have developed methods, including decision
theory, portfolio analysis, and chance-constrained programming, to guide
decisionmaking under uncertainty. Infrastructure analysts at all levels of
government might be wise to adapt these methods to their work.
Growing uncertainty about future temperature, precipitation, and sea levels
might dictate a reassessment of existing standards and safety factors for
ventilation, drainage, flood protection, facility siting, expansion capability,
and resistance to corrosion, among others. Prompt identification of inevitable
changes could allow communities time to adjust design standards based on
geographic location -- for example, on roadbed depth and home insulation levels
-- and thus realize significant savings.
THE METHODOLOGY AND ASSUMPTIONS
We assumed that a gradual sea level rise would be managed through strategies
such as raising the land in low-lying areas, upgrading levees and dikes with
pumped outflows, retreating selectively from some areas, and increasing the
freshwater head, roughly in proportion to sea level rise, to prevent saltwater
intrusion into the aquifer. The case study does not examine how climate change
might affect beach erosion or discuss related actions that might protect the
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developed barrier islands of Miami Beach and Key Biscayne, which largely lie
within 1 meter of sea level.
Preliminary analyses and estimates by local engineers and planners,
undertaken at our request, formed the primary basis for the case study. Further
information was drawn from Rhoads et al. (1987) and from the Comprehensive
Development Master Plan for Dade County (Metropolitan Dade County Planning
Department, 1979, 1988).
Our analyses assumed a 1-meter rise in sea level. The temperature and
precipitation impacts of global climate change were estimated by applying the
percentage changes, by season, indicated by two climate change models (Jenne,
1988), to historical climate data from 1950 to 1980. The models examine the
weather changes that might result from an effective doubling in carbon dioxide
levels. Both the Goddard Institute for Space Studies (GISS) and the Geophysical
Fluid Dynamics Laboratory (GFDL) models suggest Greater Miami's (essentially Dade
County's) average temperature could rise from 26°C to 29°C (75°F to 80°F). Both
models suggest the precipitation level might remain reasonably constant.
DADE COUNTY'S WATER SUPPLY INFRASTRUCTURE
Greater Miami exists within an unusually complex environmental setting.
An intricate water management system already has evolved to protect the area
against flooding, to provide freshwater, to irrigate nearby agricultural lands,
and to limit saltwater intrusion, which could harm the Everglades National Park
and contaminate much of the potable water supply. The effects on the
infrastructure of an effective doubling in carbon dioxide will be shaped by the
hydrology and existing water management system.
Miami is a hydrologic masterwork, a densely populated area bounded by water
from below and on all sides. When the city was first developed, the entire
southern tip of Florida was a mangrove swamp called the Everglades or River of
Grass. The Everglades often was awash in freshwater. The initial settlement
was built on local high points of the Atlantic Coastal Ridge, 10 to 23 feet
above sea level, and immediately adjacent to Biscayne Bay and the Atlantic Ocean.
Today, most of Greater Miami is on lower ground. It was made habitable
through drainage and reclamation (Metropolitan Dade County Planning Department,
1979). Water drainage from the Kissimmee River Basin and Lake Okeechobee begins
northwest of Miami and runs through canals to Miami and other coastal cities.
To the northwest are three water conservation areas used in the South Florida
water management system. South and west of the inhabited area is the Everglades
National Park, a unique ecology. On the east, Miami is bounded by the Biscayne
Bay and the Atlantic Ocean.
Just a few feet below Miami's surface lies the Biscayne Aquifer, the major
freshwater supply for the area. Maps in the Dade County Comprehensive Plan show
that the height of the water table varies by about 3 feet between seasons, but
exceeds sea level in most of the aquifer. The water table is very close to the
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surface except along the high points of the Atlantic Ridge. In the wet season,
water flows less than 5 feet below 34% of Miami streets (measured by Dan Brenner,
Assistant Highway Engineer, City of Miami Department of Public Works, 1986),
The Biscayne Aquifer is wedge-shaped. It is 100 to 200 feet deep along
and below Biscayne Bay and averages 100 feet in depth in the developed area.
West of the city, it falls off rapidly and ends near the Dade County line.
Because of the aquifer's shape, much of the water can be tapped only by wells
dug in or just west of Miami.
The seaward edge of the aquifer is saltwater. In many cases, the cone of
depression for the wells comes close to the salt line in the dry season. Since
the 1940s, Miami has used freshwater pressure to prevent further saltwater
intrusion into the aquifer. Currently, control structures and canals are used
to create a 2- to 3-foot head differential (Metropolitan Dade County Planning
Department, 1979). As a result, there is saltwater intrusion from 0.25 to 2
miles inland in the developed areas and about 5 miles in the Everglades National
Park where the aquifer is shallower.
The Biscayne Aquifer is one of the most permeable in the world, an
extraordinarily transmissive layering of sand, solution-riddled limestone, and
sandy limestone roughly 100 times more permeable than packed sand (Metropolitan
Dade County Planning Department, 1979). Wellfields are recharged simply by
channeling water across the aquifer and letting it percolate down (South Florida
Water Management District, 1987). The height above sea level and groundwater
discharge areas of the aquifer change constantly in response to such relatively
minor factors as rainfall and tides (Metropolitan Dade County Planning
Department, 1979).
Because of Miami's high temperatures, reduced evaporation loss makes the
Biscayne Aquifer a much better place than shallow surface lakes to store water
for use in the dry season (Metropolitan Dade County Planning Department, 1979).
Furthermore, overuse of surface storage would destroy the unique Everglades
ecology, which requires cyclic drying.
In the remainder of this paper, we present the case study results.
Specifically, we discuss Dade County's possible responses to sea level rise; how
the various parts of the infrastructure could expect to fare and what
improvements might have to be made; and what the costs of climate change/sea
level rise are likely to be.
HOW WILL DADE COUNTY RESPOND TO SEA LEVEL RISE?
Because of the Porous Aquifer, Diking Alone Will Not Control Sea Level Rise
In most coastal communities, the major challenge of a 1-meter rise in sea
level would be to control surface inundation. The solution in both New Orleans
and the Netherlands has been to dike the water at the surface and pump out the
modest seepage into ditches behind the dikes.
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To apply this approach in Miami would require building a dike that holds
water back for the entire depth of the Biscayne Aquifer. Essentially, a water-
impermeable barrier would be needed along the length of Broward and Dade Counties
to a depth of 100 to 150 feet. Otherwise, the pressure of the seawater would
cause it to rush into the aquifer below the surface and push the freshwater in
the aquifer up more than 3 feet, raising it very close to the surface. If the
freshwater were pumped out, it gradually would be replaced by saltwater and the
freshwater storage capacity of the aquifer would be lost.
Raising Land and Increasing the Freshwater Head Might Be Primary Responses
A very preliminary analysis suggests two primary responses to sea level
rise. First, raise the land in low areas rather than trying to dike. Second,
increase the freshwater head roughly in proportion to sea level rise, thus
maintaining the freshwater storage capacity of the aquifer. The latter method
will not raise the water table notably more than sea level rise alone.
Thus, if sea level rose 3.3 feet, Miami might raise its freshwater head by
2 to 3 feet to control the infiltration of subsurface seawater into the aquifer,
as well as raise or build surface levees and add pumping capacity in developed
low-lying sections. Even this approach might not work because the necessary
water may not be available, especially during droughts. According to the Dade
County master planning staff, Miami could face a water supply deficit in the 21st
century. The most practical solution to the shortage would be to purify sewage
effluent for use in cooling towers and for lawn watering, or to desalinate water
at three times the cost.
For the purposes of this report, consistent with Rhoads (1987), we have
assumed that selective retreat, levees with pumped outflows in selected low-
lying areas, and elevation of some facilities and structures, as well as an
increase in the freshwater head to protect the aquifer, would be the most cost-
effective combination solution on the mainland. For a discussion of the
appropriate intervention for Miami Beach and other developed barrier islands,
primarily beach nourishment, consult Leatherman (1989).
Sea Level Rise May Necessitate Increased Coastal Defense
In coastal communities such as Miami, sea level rise could stimulate
extensive upgrading of coastal defense structures such as dikes, saltwater guard
locks, and pumping systems to prevent inundation, erosion, storm surges, and
reduce saltwater intrusion into aquifers and rivers. Currently, these structures
are such a minor category of infrastructure that they are not inventoried or
included in needs assessments.
A 1-meter rise in sea level would not inundate much of the developed Miami
mainland, although it would increase considerably the risk of flooding,
especially during hurricanes. One area at risk of inundation is the large, low-
lying area south of Miami, a low-density residential area built on land reclaimed
by adding fill. Levees and water control structures used for flood protection
in these areas should prevent inundation if they are upgraded. Structures in
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these areas generally sit on piles and fill already raised 1 to 1.5 meters above
the land surface to reduce flood risks.
Dade County's water management system includes about 1,000 kilometers of
canals, 400 kilometers of levees, and 30 control structures (Metropolitan Dade
County Planning Department, 1979). It seems unlikely that the canals would
require rebuilding, but they might have to be dredged more frequently. The
levees (dikes) probably would be raised in selected areas, which can only be
identified through detailed studies. Robert Hamrick at the South Florida Water
Management District estimates it could cost approximately $7,000 per linear
kilometer to raise the levees 60 centimeters with mounds of crushed limestone,
which is extensively quarried in local open pits. The fill is scooped from a
copious supply that lies virtually at the surface on public lands, and then is
loaded on flat-bottomed barges and sprayed onto the tops of the levees.
Interpolating from the analysis in Weggel (1989), we estimate that $60 million
could be spent on canal and levee improvements if sea level rose 1 meter over
the next 100 years. Hamrick also suspects that the 30 control structures in Dade
County would be redesigned and replaced at an estimated cost of $1.6 million
each, a total of $48 million in 1988 dollars.
The current water management system relies mainly on gravity drainage.
With sea level rise, much pumping capacity might have to be added to prevent
subsurface saltwater intrusion. Both the capital and operating costs could be
large.
HOW WILL THE PRESENT INFRASTRUCTURE FARE?
Building Foundations Are Adequate
A preliminary examination of the structural stability of footings and
pilings suggests that buildings are not likely to suffer structural instability
from a 1-meter rise in the water table. When a building is on coral rock or
limestone, concrete footings with reinforcing steel frequently provide structural
support. A monolithic slab with flared ends to a depth of 45 to 60 centimeters
is a typical foundation for a residence, since most residential structures and
commercial buildings are too close to the water table to have basements. Larger
residences might have both seatings and footings. Tall buildings, including
residential condos, are most likely to rest on piles, although other techniques,
including spread footings and compacting, are used to provide structural support.
Flooding raises little possibility of structural instability due to settling
or foundation cracking, for example, because the foundations are overdesigned
by a factor of 1.5 to 2.0, according to engineers at Florida Atlantic University.
Currently, regulations and permitting procedures, including Dade County Flood
Criteria and criteria of the National Flood Insurance Program, require most new
construction to be on raised lots to prevent flood damage.
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One-Third of the Streets Night Need To Be Raised
A typical city street consists of a 4-centimeter layer of asphalt
constructed over a 20-centimeter lime rock base. Beneath the base is a subgrade,
with its top 15 centimeters compacted to a minimum of 95% of its maximum density.
If the sea level and water table rose roughly 1 meter, given the annual
fluctuations in the water table and its proximity to the surface, the subgrade
and base of many city streets would be subject to a certain amount of saturation.
Complete structural failure would occur if a heavy load were to pass over the
surface. To prevent collapse, vulnerable streets would have to be raised by 1
meter.
Dan Brenner of the City of Miami Department of Public Works estimates that
approximately 34% of street and highway mileage -- 400 kilometers -- is 1.5
meters or less above the water table. Raising streets by 1 meter during
reconstruction, according to the Department of Public Works, would cost between
$450 and $55 per linear meter (remember that fill is cheap) with minimally
improved transitions to adjacent properties. Reconstructing the 400 kilometers
to adjust for a 1-meter rise in sea level could add roughly $237 million to the
$1.4 billion reconstruction cost of these projects. If a 2.5% rate were used
to compute further costs, expected costs would be minimized by raising a Miami
street even though the subbase clearly would not be affected by sea level rise
in the next 10 years, but as long as there were a 38% or greater chance that sea
level rise would be substantial enough to affect the subbase after 10 years.
(This cost estimate for raising streets omits substantial private costs for
better drainage, raising of some yards (especially at newer buildings where the
structure itself already is raised), raising lots at reconstruction, and positive
sewage pumping from the houses to the mains in some areas.)
If sea level rise required streets and buildings to be raised, the
connectors from buildings to the sewer interceptors also would have to be
rebuilt. Pump stations also might have to be raised and modified to maintain
the same driving force (differential in inside versus outside pressure), and
overflow structures might need to be improved.
In the City of Miami, the costs of adapting elevated houses and other
building connections to existing sewer lines would be the responsibility of
private property owners. The remainder of the costs would be public. The Miami
Department of Public Works estimates that the costs to raise and modify pump
stations, modify overflow structures and miscellaneous appurtenances, and raise
manholes alone could be $8 million.
The aesthetic and drainage impacts of raising streets could be dramatic.
Except for recently constructed houses (which often are raised to meet flood
ordinances), people's houses, yards, and garages would be 1 meter below the
streets (and canals), a situation strongly reminiscent of the Dutch countryside.
Some yards and houses surely might be raised when they are reconstructed, and
yards might be raised or flanked by covered exfiltration trenches. Fortunately,
there are no basements.
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Many Causeways and Bridges Could Be Raised at Reconstruction
The causeways running from Miami across Biscayne Bay to Miami Beach are
between 1.5 and 3 meters above sea level and might be at risk of structural
weakening and failure. They also would be vulnerable if higher sea level
increased hurricane storm surges. These potential impacts could be avoided if
reconstruction over the next 100 years used design features to mitigate the
effects of sea level rise. On the other hand, if modifications were not made
during reconstruction, the cost of retrofitting the bridges could be
substantially higher.
Except for steel drawbridges, most bridges in Miami are constructed of
concrete and steel, with a life expectancy of 50 years. Only those near the
coast have epoxy-coated reinforcing bars, a practice introduced in 1970 to fight
corrosion. Without remedial action, the effects of sea level rise might include
the following:
• Pavement failure in low-elevation bridge approaches.
• Erosion beneath low-lying bridge abutments and consequent differential
settlement, stresses, and strains.
• Potential lifting of corrugated steel and box culverts.
• A drop in the elevation of fenders on the piers over navigable waters.
(Fenders protect against damage from vessels bumping into the
substructure.)
• Reduced underclearances on navigable waterways.
• Reduced accessibility inhibiting proper inspection and maintenance.
• Added wave "slapping action."
• Increased likelihood of flood backwaters, particularly for bridges that
have underclearances of 3 to 6 feet over non-navigable waters.
Regardless of improvements over the next 100 years, bridges with piers and
piles in both Biscayne Bay and in rivers could experience deeper scouring,
although the waterflow velocity under non-storm conditions would decrease because
of the increased water depth. Scouring also could increase if storms became more
frequent or severe.
Airports Might Need Better Drainage
Miami International Airport is a major international hub. Located in
northwest Miami, its airfields and aprons cover 20 square kilometers. Unlike
the majority of major commercial airports, most of the surface area is asphalt
pavement. The aprons are concrete. The asphalt varies in thickness from 5 to
40 centimeters depending on the base. An extensive drainage system allows storm
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runoff to empty into ditches by the airfield, then into the Blue Lagoon and the
Tamiami Canal. The groundwater elevation ranges from 60-90 centimeters to 1
meter, runways 2.7 to 3.0 meters, and taxiways and aprons 24 to 27 meters. A
1-meter rise in groundwater would not flood the pavement or base, but would
affect drainage retention capacity and exfiltration during a storm. If several
large pumping stations were constructed to draw down the airport water table at
the onset of a storm, acceptable operating conditions could be maintained.
Drainage interconnections and related improvements such as pump stations, dikes,
and culverts might cost $30 million (Tripp, 1989).
The likely impact of sea level rise on one of Miami's wastewater treatment
facilities, located on Virginia Key, also was assessed. Since Virginia Key has
no freshwater beneath the surface, intrusion is not an issue. The treatment
plants are approximately 3 meters above sea level. Berms and dikes reach
elevations of approximately 4 meters, while sterile fill material from the sludge
plants has accumulated to elevations around 30 feet. A severe hurricane
producing higher storm surges still could wash out portions of the island. If
the activated sludge treatment plants were still in operation as sea level rise
accelerated, the berms and dikes on the island might have to be raised to prevent
processed sludge from being washed into Biscayne Bay. Another possible effect
of a hurricane is that dirt beneath the plant could be washed out, causing the
piping to collapse.
Storm Sewers and Drainage Trenches Might Require Major Upgrading
Miami relies primarily on localized drainage and canal systems, involving
exfiltration that carries surface storm water to subsurface groundwater. Highly
permeable soils make this a cost-effective form of stormwater drainage, except
in low-lying areas where there are fine soils that do not drain well. Where
natural drainage systems are not effective, or tidewaters and easterly winds
increase the water head pressure at discharge outlets to the bay, a positive
drainage pipe system is used.
Standards for storm sewers vary at the federal, state, and local levels.
Interstate highway storm sewers are designed for 10-year storms. On arterial
streets in areas of high population density, 3-year storms serve as the design
standard. On local streets, Miami's system is designed for a rainfall rate of
3.75 centimeters per hour. Ponding occurs three or four times per year on local
streets with this type of storm drainage (City of Miami Department of Public
Works, 1986).
In 1988, Miami started a 12-year, $267 million program to reduce flooding
and ponding. This program includes constructing 225 kilometers of exfiltration
trenches at a cost of $105 million, as well as positive drainage construction
at a cost of $55 million. These systems are designed to provide protection
against flooding from 25-year storms (City of Miami Department of Public Works,
1986).
Even with these planned improvements, if sea level rises 1 meter, flooding
and ponding problems could be worse than they are today, especially because the
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wpter table will be closer to the surface. The costs of adequate future flood
protection almost certainly would be several hundred million dollars.
Water Supply Night Be Reduced Unless Hurricanes Increase and Demand for
Electricity Could Increase
Miami's water supply could be reduced by water used to prevent saltwater
infiltration. Some wellfields almost certainly would have to be relocated
farther inland. Potentially more important than the actual water expenditure,
sea level rise would raise the aquifer closer to the surface, putting it within
e^sy reach of the roots of more plants. Using evapotranspiration and soil
moisture models, Rhoads (1987) estimates that soil moisture deficiency
probabilities could double, assuming no change in rainfall.
The warmer temperatures also could raise water demand, most notably for
commercial cooling towers. Indeed, Linder et al. (1987) project that increased
air-conditioning needs in south Florida could raise peak electricity demand by
20%.
Although the solution to these problems will require detailed study, one
alternative is to increase capacity to produce desalinated water -- e.g., by
bpiling and cooling, reverse osmosis filtration, or some new technology --or
to use purified effluent as a backup supply for drought periods. Full cost
pricing of this water would encourage greater conservation and thus reduce
demand. Another complexity requiring study is the need to maintain some water
in the water conservation areas, since the water containments are designed to
function with a vegetative lining.
The largest uncertainty about water supply is the impact that climate change
will have on hurricanes. Hurricanes historically have contributed substantially
tp aquifer recharge (Metropolitan Dade County Planning Department, 1979). Rising
temperatures could increase hurricane frequency and intensity -- a mixed blessing
that would ensure an adequate water supply but inflict billions of dollars in
wind and flood damage.
POTENTIAL COSTS OF CLINATE CHANGE TO MIAMI
Table 1 shows that the total costs to make the improvements and repairs
discussed in the previous section of this paper could easily exceed $600 million.
The costs could be much higher if changes in sea level or global climate came
through abrupt "sawtooth" shifts, making it difficult to adapt infrastructure
pHmarily during normal repair and replacement.
The infrastructure costs suggested here are large but not unmanageable.
We estimate that the costs could be accommodated by increasing annual capital
spending by 1 to 2% for the next 100 years.
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Table 1. Probable Infrastructure Needs and Investment in Miami in Response
to a Doubling of C02 (millions of 1987 U.S. dollars)
Infrastructure Needs
Costs
Raising canals/levees
Canal control structures
Pumping
Raising streets*
Raising yards
Pumped sewer connections
Raising lots at reconstruction
Drainage
Airport
Sewer pipe corrosion
Water supply
Total
$60
$50
not estimated
$250 extra reconstruction cost
not estimated
not estimated
not estimated
$200-300
$30 not estimated; retrofit costs more
than raising at reconstruction
minimal
not estimated
$600+
*Assumes streets will be raised as they are reconstructed, roughly at 35-year
intervals. If the county does not raise streets in advance of sea level rise,
the cost may be an order of magnitude higher.
THE POLITICS OF ANTICIPATING SEA LEVEL RISE
Cost-effective adaptation to global climate change will require complex,
careful decisions about how and when to adapt the infrastructure. Life-cycle
costing and expensive upgrading in anticipation of future changes will be
essential. To accomplish this will require strong leadership. It will also
require careful examination of the available options for controlling the sea.
Hard political decisions will need to be made concerning how well Dade County
can afford to protect its coastal exposures and how the costs will be split among
affected property owners, local governments, the Metropolitan Dade County
government, the State of Florida, and the Federal Government.
The economic cost of climate change is not the only expense Miami faces.
However, local officials also will incur substantial political costs as they
attempt to meet the impending infrastructure crisis. Suppose Miami chooses the
most cost-effective course and acts in anticipation of a rising sea. Bridges
and roads could be raised as they come due for reconstruction. Water, sewer,
and drainage facilities could be modified to counteract the effects of an
anticipated rise in sea level. City officials might have to educate the bond
market. Raising bridges or streets, for example, could be viewed as
overbuilding. It could be an uphill battle to convince bond underwriters that
the city actually was pursuing a strategy that protects investors.
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Even if no extra costs were involved, raising streets could prove quite
controversial. Few people will like looking up at the street from their living
room windows. Worse, no one will feel comfortable the first time runoff from
a hurricane pours down the edge of the streets into drainage ditches in their
yards. Imagine the hue and cry when some of those ditches overflow.
The political price of such pre-emptive action could be high. Taxpayers
would be asked to pay extra taxes to help underwrite infrastructure improvements
because sea level might rise at some uncertain future date. Given voters'
general aversion to tax increase of any kind, candidates or elected officials
pursuing such a strategy could face problems at the polls. There would
undoubtedly be considerable political debate over spending money in anticipation
of an uncertain event versus using that money to address known current problems.
Opposition to anticipatory action might not be the only political reaction.
Lobbying and political organizing could focus on location issues, that is, what
parts of the city will be considered priority areas and thus will be the first
to be protected.
Inaction also is politically risky. Imagine voter reaction if nothing is
done in advance of sea level rise until the transportation system is affected.
Road collapses make headlines, especially if people are killed as a result.
Emergency repairs to roads and bridges, even if undertaken before any damage
occurs, can cause massive traffic delays. That kind of spending can break
budgets, as outside contractors are needed to do work that normally would be done
locally. Emergency raising and rebuilding of the lowest 5% of the streets, one
seventh of those that might need to be raised before the rise in sea level
reaches one meter, could cost $240 million at normal construction prices, about
half the total amount the city spends currently on capital construction. Bridges
and bridge approaches would have to be reconstructed simultaneously, adding
further costs. Raising streets during normal reconstruction would be far less
disruptive. Again, unduly massive hurricane damage really could generate
controversy.
Miami officials seem unlikely to take any major anticipatory action on
global climate change until some precipitating event, possibly a direct hit by
a major hurricane. Other possible incentives might be revision of engineering
design standards to require consideration of possible sea level rise, or the
availability of federal matching funds for planning responses to global climate
change or for risk-reduction activities.
Regardless of the approach Miami officials choose, much public education,
campaigning, and political acumen will be required. The city faces a long, hard
row to high ground.
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BIBLIOGRAPHY
City of Miami Department of Public Works. 1986. Storm Drainage Master Plan,
Executive Summary, Miami, FL: City of Miami Department of Public Works,
September.
Jenne, R. 1988. GISS and GFDL Climate Projections. Denver, CO: National
Center for Atmospheric Research.
Leatherman, S. 1989. Cost of Defending U.S. Open Coast from Rising Sea Level.
College Park, MD: University of Maryland.
Linder, K.P., M.J. Gibbs, and M.R. Inglis. 1987. Potential Impacts of Global
Climate Change on Electric Utilities. Fairfax, VA: ICF Incorporated. 824-CON-
AEP-86. December.
Metropolitan Dade County Planning Department. 1988. Comprehensive Development
Master Plan for Dade County, Florida. Miami, FL: Metropolitan Dade County
Planning Department. April.
Metropolitan Dade County Planning Department. 1979. Comprehensive Master Plan
for Dade County, Florida. Miami, FL: Metropolitan Dade County Planning
Department. July.
Rhoads, P.B., C.C. Shih, and R.L. Hamrick. 1987. Water Resource Planning
Concerns and Changing Climate: A South Florida Perspective. In Proceedings of
the Symposium on Climate Change in the Southern United States: Future Impacts
and Present Policy Issues, conducted by the Science and Public Policy Program,
University of Oklahoma. Washington, DC: U.S. Environmental Protection Agency,
pp. 348-363.
South Florida Water Management District. 1987. Water Resources Data and Related
Technical Information to Assist Local Government Planning in Dade County. West
Palm Beach, FL: South Florida Water Management District.
Tripp, R. 1989. Personnal communication to the Urban Institute from Howard,
Needles, Tammen and Bergendoff, 1989.
Weggel, J.R., S. Brown, J.C. Escajadillo, P. Breen, and E.L. Doheny. 1989. The
Cost of Defending Developed Shorelines along Sheltered Waters of the United
States from a Two-Meter Rise in Mean Sea Level. In: The Potential Effects of
Global Climate Change on the United States. J. Smith and D. Tirpak, eds.
Washington, DC: U.S. Environmental Protection Agency.
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ACCOMMODATING SEA LEVEL RISE IN DEVELOPING WATER
RESOURCE PROJECTS
ROBERT H. SCHROEDER, JR.
Chief, Planning Division
U.S. Army Corps of Engineers
New Orleans District
New Orleans, Louisiana
ABSTRACT
Apparent sea level rise along the Gulf of Mexico coast varies from about 3
to 35 millimeters per year. In developing civil works projects, this factor must
be accommodated. Much of the central coastal area consists of marshlands that
are about 25 to 50 cm above see level. Small rises in sea level therefore can,
inundate large areas. Changes in sea level can also cause saltwater to intrude
into brackish estuaries, killing the marsh grasses and converting marshlands into
open water. These marshes are valuable for the production of fish and fur
bearers, for recreation, and for their social attributes. Several projects and
studies under way are aimed at reducing the rate of loss occurring at present-
-estimated to be about 100 square kilometers per year. Sea level rise is one
of several variables being considered in developing plans to save this coastal
area.
INTRODUCTION
Sea level rise is one of the many factors that influence the planning and
development of federal water resource projects in coastal areas of the United
States. It affects both sides of the scale used by planners attempting to
balance development with environmental preservation.
Federal participation in a water resource development project results from
congressional action based on impartial studies by the U.S. Army Corps of
Engineers. The process begins when a local government seeks congressional
assistance in solving a specific water-related problem. The U.S. Congress
responds by asking the Corps of Engineers to determine the economic,
environmental, and social feasibility of a project to solve the problem and the
appropriate level of federal participation.
The U.S. Army Corps of Engineers is the largest engineering organization
in the United States. The U.S. Congress has given the Corps the mandate to
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provide engineering services in times of both war and of peace. The Civil Works
elements of the Corps of Engineers are concerned with the development of water
resource projects. Military officers fill the top leadership position in the
Corps; the staff consists of primarily civilian professionals. In the New
Orleans District in Louisiana, for example, 7 military officers and over 1,300
civilians work with the Corps of Engineers. The Corps works closely with many
other federal agencies, including the Environmental Protection Agency, the Fish
and Wildlife Service, the National Marine Fisheries Service, and the Soil
Conservation Service. It also works with many state and local agencies. The
costs of Corps projects are generally shared with a local or state government.
Corps regulations (Engineering Circular 1105-2-186) concerning future sea
level rise require that a sensitivity analysis be done to determine if whether
and how potential projects would be affected. That determination is based on
an extrapolation of historic local sea level rise as the minimum level and curve
III (i.e., 1.5-meter rise by 2700) of the National Research Council report (1987)
as the high level (see Figure 1 in Titus paper on effects of sea level rise).
Since it may be 25-35 years before we can determine which sea level rise scenerio
is appropriate, projects sensitive to sea level rise should be designed to allow
for future modification should it become necessary.
EFFECTS OF SEA LEVEL CHANGE
The impact of changing sea level on the development of water resource
projects depends on the project. We examine several examples.
Navigation Channel Projects
For channel projects, rising sea level would increase available depth,
assuming no change in sedimentation which would have a small but positive effect
on shipping. On the other hand, onshore facilities built at or near historice
sea level could be damanged. In developing projects of this type, planners must
provide for sea level rise in the design of onshore facilities and should
recognize that future channel maintenance costs may be less than current ones.
Navigation Locks
This paper defines navigation locks as structures designed to raise vessels
from waterways that are tidal to water surfaces at higher (nontidal) elevations
(see Figure 1). Because the height of the gates and walls of these structures
is a function of the higher elevations, sea level rise should have little impact
on their design. Again, as sea level rises, the required lift will decrease,
resulting in slightly lowered operating costs.
Saltwater Guard Locks
These locks designed to prevent saltwater intrusion into freshwater basins
that are at or near sea level. During high tides, the oceanside water levels
exceed those on the inside (Figure 2). For this type of structure, any increase
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OCEAN SIDE
LAND SIDE
MSL
Navigation Lock
Figure 1. Diagram of navigation lock.
OCEAN SIDE
LAND SIDE
MSL
Salt Water Guard Lock
Figure 2. Diagram of a saltwater guard lock.
in sea level will require a like increase in the height of the walls and gates.
This can be accomplished by either building the structure initially to
accommodate future sea level rises or constructing the lock so that it can be
added to in the future.
Food Control Channels and Levees
As sea level rises, the effective carrying capacity of a channel dike
(leveed) decreases. The only way to make up for such a decrease is to add to
the heights of the dikes. To accommodate future increases in sea level, it is
usually prudent to acquire the necessary real estate when the original dike is
built, and to do any necessary relocation of utilities to conform with future
conditions. The dike itself can be raised in the future as conditions change.
Hurricane Protection Dike
This special type of levee is one of the public works structures most
sensitive to changes in sea level. Typically, a hurricane protection dike is
built to encircle a major populated area. That area is often at or below sea
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level. These dikes are usually built to protect against the most severe
meteorological events possible for the area (the Standard Project Flood). As
shown in Figure 3, the populated area is, in effect, a bowl, and any overtopping
of the dikes would cause water to pond and flood the city. It is imperative that
these dikes be upgraded as sea level rises. As with other types of dikes, it
is prudent to acquire sufficient rights-of-way and perform all utility
relocations to conform to future changes.
LAND LOSS IN LOUISIANA
Projects designed to protect barrier islands or coastal marshes are
particularly vulnerable to changes in sea level. To illustrate the problem of
developing this particular type of project to accommodate future sea level
changes, an area along the central Gulf of Mexico will be used.
Located in the State of Louisiana, the coastal area consists mostly of low-
lying marshlands less than 1 or 2 meters above sea level. As a result, small
changes in sea level inundate large areas of the coastal marsh. This area
contains 40% of the coastal marshes of the United States and is suffering 80%
of the national coastal marsh loss. These marshes were formed over geologic time
as the Mississippi River migrated across the coastal area following natural
geologic processes. Today, those lands are under attack from a number of
sources. No single cause can be pointed to as the culprit. Coastal and deltaic
processes are too complex to permit easy answers. Each force - natural and
human-induced - acts upon the other, synergistically intensifying and
accelerating each effect.
HURRICANE TIDE
Hurricane Levee
Figure 3. A hurricane protection dike used to surround a populated area and
protect it from the most severe meteorological events.
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Causes of Land Loss
Nature is responsible for a share of the marsh loss. The long-term forces
of sea level rise, subsidence, compaction, saltwater intrusion, and erosion have
caused significant changes in the relative land and water surface elevations.
Compaction and subsidence together are estimated to average 0.6 meters per
century, but the rate ranges from about 4 meters at the mouth of the active delta
of the Mississippi River to 1 meter at Grand Isle to less than 1/2 meter in the
western portion of the state. Historical data indicated that sea level rise is
an additional 0.15 meters per century. Accordingly, changes in eustatic sea
level forecast by many investigators (Boesch, 1983; Hoffman, 1983; Nummendal
1983: Templet, 1985) are currently being exceeded by relative sea level rise
along the Louisiana coast.
Both sea level rise and subsidence accelerate saltwater intrusion and
erosion, changing the marsh habitat. Erosion eats away at Louisiana's 70,000
kilometers of tidal shoreline and at the barrier islands. The erosion causes
the shore and barrier beaches to retreat from 3 to 12 meters each year.
The gradual erosive effect of daily natural forces on the barrier islands
is dramatically accelerated by hurricanes and storm tides. Big storms cause
massive damage by cutting through islands and widening and deepening passes, such
as that which occurred on one of the Chandeleur Islands that was widened during
Hurricane Juan.
Though natural forces play an important role in coastal land loss, the
activities of people are also a major cause. Flood control is indispensable in
the floodplain of the Mississippi River and its tributaries. This flood
protection and the economic development in Louisiana's coastal wetlands have
caused much of the marsh loss.
Flood control dikes on the rives have changed the annual hydrologic regime.
In a natural hydrologic cycle, the swollen Mississippi and Atchafalaya Rivers
would overflow their banks every spring, flooding the marshes with nutrient-and
sediment-rich water. The sediments and nutrients would build and sustain the
natural diversity of the marsh. Since dikes were built for flood control and
protection of national and international navigation, the only water that flows
into the marshes is rainfall. Each year, 183 million tons of sediment are
carried down the river. This material is not building new marsh as it did prior
to the levee construction; rather, it is dropping off the edge of the Continental
Shelf into the deep waters of the Gulf of Mexico.
In this fragile coastal environment, activities in the interest of economic
development interact with and intensify the natural processes. Leveeing,
channelization, oil exploration, and agricultural, urban, and industrial
expansion have accelerated the rate of marsh loss. The marshes are laced with
13,300 kilometers of navigation, drainage, and petroleum access canals that
segment the marsh.
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With no annual flood of fresh water to hold back intruding saltwater, the
marshes and cypress swamps that are not tolerant to salt are being destroyed and
replaced with open-water ponds. These open-water areas increase the interface
between water and marsh, causing more erosion. Across the Louisiana coast, one
hundred square kilometers of marshlands are lost each year.
Effects of Land Loss
What will this loss of a half million hectares of Louisiana's coastal marsh
mean to the economy of the nation, to the development of the state, and to the
people who live, work, and play in the coastal marshes?
About $300 million in marsh real estate value will be lost by 2040.
Moreover, as marshes are lost, the Gulf of Mexico's estuarine-dependent fishery
will decline. By the year 2040, commercial and recreational fish and wildlife
harvests will be down to about 70 percent of the present harvest. The impact
on the nation's economy will be an annual loss of $114 million. Sport fishermen
and hunters will lose 4 million activity-days of recreation by 2040 as compared
with today. The annual economic impact of this to the nation will be $19
million.
Loss of the coastal marshes threatens most of the national, state, and
local development investment in the coast. This includes about 250 kilometers
in portions of major waterways built by federal and state governments. The banks
of these waterways will be lost to erosion. The cost of the increased
maintenance dredging that will be required in these waterways could exceed $50
million a year.
Hurricane protection dikes will have to be enlarged and shielded from
erosion. About 90 kilometers of federal hurricane protection projects, including
the "Lake Pontchartrain and Vicinity," the New Orleans to Venice," and the
"Larose to Golden Meadow" projects, will have to be protected to maintain the
current level of protection. The estimated coasts could exceed $38 million.
Roads, pipelines, and utilities will require relocation. Nearly 160
kilometers of federal and state highways, about 44 kilometers of railroad tracks,
2,500 kilometers of oil and gas pipelines, and 620 kilometers of utilities and
telephone lines will have to be relocated. These relocations would cost billions
of dollars.
Property will be lost or will have to be protected at great expense. About
1,800 business, residences, camps, schools, electric power substations, water
control structures, pumping stations for gas, oil, and water, and storage tanks
will have to be protected or relocated.
Ongoing Projects
Land loss is a significant national problem, and the U.S. Army Corps of
Engineers has several projects and studies that specifically address this
problem. Protecting people along the Mississippi River from flooding requires
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a system of river dikes which confine the water that historically flooded the
marshes adjacent to the river and prevent the annual nourishment of those marshes
essential for their maintenance.
The Corps of Engineers and the State of Louisiana plan to restore a portion
of the marsh flooding cycle in a way compatible with flood protection. Three
freshwater diversion projects are scheduled for implementation in the Louisiana
coastal areas. Those projects will introduce fresh water from the Mississippi
River into the adjacent marshes and estuaries. Fresh water diverted through
these structures will restore and enhance wetland vegetative growth by
establishing desirable salinities. These salinities and much-needed nutrients
carried by fresh water will increase the productivity of the marshes' fish and
wildlife.
Another tool to help offset coastal land loss is the use of dredged material
to build new or restore sinking marshes. Over 1,200 hectares have been created
through the Corps of Engineers' maintenance dredging program. Creation of
another 7,500 hectares through the future enlargement of the Mississippi River
is planned.
Diverting sediment to create new lands has also helped to mitigate some of
the ongoing losses. In addition to those already constructed, the Corps of
Engineers is studying the cost-effectiveness of a system of uncontrolled sediment
diversions within the active delta of the Mississippi River.
The Corps of Engineers' regulatory program has been a major influence on
human activity in the coastal zone. Each year the Corps' New Orleans District
issues between 1,500 and 2,000 permits, and processes between 2,000 and 2,500
permit applications. Permitted work is inspected to ensure that it conforms to
Corps criteria, which include measures designed to prevent as much damage to
marshes and other wetlands as possible. For example, the permit applicants are
required in some cases to construct a wooden road over the marshes, rather than
dredging an access canal.
Louisiana Coastal Area Studies
Several ongoing studies are attempting to develop long-term solutions to
the coastal loss problems. The costs of these studies are being shared by the
federal government and the State of Louisiana. In these studies, specific areas
will be targeted for preservation or enhancement. Obviously, every acre of the
coastal marshes cannot be saved, but many acres can.
Many factors will be used to determine which area exhibit the highest
likelihood of success. Topography will play a major role -- shallow water areas
not subject to high wave energy would be a prime location. Other factors would
include cost, proximity to populated areas, availability of a sediment supply,
and environmental considerations. The Corps/state study is using a variation
on the usual federal benefit-to-cost evaluation methodology. In this study,
alternatives will be compared based on cost-effectiveness. A full array of both
structural and nonstructural solutions will be analyzed.
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Sea level rise will complicate this already complex situation. Since many
of the solutions being considered do not Involve hard structures, but rather
Include such approaches as freshwater diversion, sediment diversion, dredge spoil
placement, and regulatory control, It Is likely that sea level rise can be
accommodated. •
BIBLIOGRAPHY
Boesch, D.F., Levin, D., Nummendal, D., and Bowles, K. 1983. Subsidence In
Coastal Louisiana: Causes, Rates, and Effects on Wetlands. Washington, DC:
U.S. Fish and Wildlife Service, Division of Biological Services.
Hoffman, J., D. Keyes, and J. Titus. 1983. Projecting Sea Level Rise to the
Year 2100. Washington, DC: U.S. Environmental Protection Agency.
Nummendal, D. 1983. Future sea level rise along the Louisiana coast. Shore
and Beach, April.
Templet, P. 1985. Land loss in Louisiana: A White Paper. Zachary, LA:
Templet Resources.
U.S. Army, Corps of Engineers. 1988. Guidance on the Incorporation of Sea Level
Rise Possibilities in Feasibility Studies. Engineering Circular 1105-2-186 Draft
V 1.31, 20, Washington, DC: U.S. Corps of Engineers
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