United States
Environmental Protection
Agency
Office Of
The Administrator
(A101F)
171 R-92-008
April 1992
N-/EPA
Sea Level Rise Issues And
Potential Management Options
For Local Governments
Printed on Recycled Paper
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DISCLAIMER
This report was furnished to the U.S. Environmental Protection
Agency by the student identified on the cover page, under a National
Network for Environmental Management Studies fellowship.
The contents are essentially as received from the author. The
opinions, findings, and conclusions expressed are those of the author
and not necessarily those of the U.S. Environmental Protection
Agency. Mention, if any, of company, process, or product names is
not to be considered as an endorsement by the U.S. Environmental
Protection Agency.
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Sea Level Rise Issues and Potential Management
Options for Local Governments
by
Hudson Slay
Duke University
School of the Environment
December 13, 1991
Prepared as a final report for EPA Fellowship (#U-913518-01-0) under the National Network For
Environmental Management Studies (NNEMS) Program. ental Protection
fcm 5 lbrary im Floor
77W8sUsckspr>i', ,, ..3'
Chicago, 1L 60GC1-— J
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Abstract
This report was produced as part of a National Network of Environmental
Management Studies Fellowship sponsored by the United States Environmental Protection
Agency Work was conducted from June until November 1991 while the author was an
intern with the Marine and Estuarine Protection Section, EPA, Region I (Boston) and a
student at Duke University, School of the Environment. The report is intended to advise
local governments in addressing sea level rise. Potential impacts of sea level nse are
reviewed and a case study of Chatham, MA is presented. The case study incorporates a
geographic information system (GIS) and considers three different sea level nse scenarios
which may be useful for general planning purposes. Management options and guidelines tor
assessing sea level are also offered to assist local governments address this issue.
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Table of Contents
Page
Executive Summary . . . • • • •
2
Introduction .
Impacts of Sea Level Rise
Flooding . . • • • • • '
Coastal Erosion •••••••''
Saltwater Intrusion . . • • • •
Alteration of Critical Habitat . . • •
Possible Strategies .
Entrenchment versus Retreat •••••' :^
Planning ...••••••
Case Study-Sea Level Demonstration Project
Introduction ...-•••••
Methods 2J
Marsh Conditions ...••••• ^
Possible Impacts of Sea Level Rise . . • • • '99
Conclusions ..-••••••
Use of a Geographic Information System (GIS)
Introduction . . • • • • • • ,~
Procedure . . • • • • • • o't
Results . ™
Limitations and Benefits ...-••• ^
Cost Limitations . . • • • • •• • ^
Conclusions ...-•••••
Options for Addressing Sea Level Rise . . • • • .31
Guidelines for Sea Level Rise Assessment
Education ....-•••• ^
Research ...-••••• ^
Mapping
Planning and Policy Implementation JO
Conclusion . . • • • • • • .37
oo
Acknowledgements ...••••••
00
Notes °°
Appendices
References
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EXECUTIVE SUMMARY
This report is intended to advise local governments in addressing sea level rise. Potential
impacts and their significance to sea level rise are presented to give an idea of the complexities of the
issue. In addition, a case study was conducted in Chatham, MA to demonstrate how sea level me
impacts can be addressed on the local level. Finally, results and other information obtained from the
case study is used to establish general procedures to assist local decision makers in assessing sea level
nse.
During recent geologic time the level of the sea has fluctuated from 300 feet below to 20 feet
above present sea level, depending upon global temperature (Titus et_aL, 1991) fn atmospheric
greenhouse effect keeps the Earth warmer than it would be otherwise; but scientists believe that this
namral warming is behig supplemented by the so-called "greenhouse gases" (methane, carbon dioxide,
chlorofirocarLs, nitrous oxides, ozone, and water vapor), some of which result from human
activities. On the Atlantic coast of the United States, sea level has been rising at a rate of about 1
foot per century (Titus etaL, 1991). The historical change in sea leve coupled with *e uncertonty
of global warming has generated several estimates of an acceleration of sea level nse in the future
(Titus, 1991).
Initial predictions of accelerated sea level rise have been refined and downscaled considerably
as continued research reveals the subtle changes that result from global warming. TheCurrent
scenarios for global (eustatic) sea level rise by the year 2100 are 50 cm, 100 cm, and 200 cm (Titus,
1989) with a current best estimate of 65 cm (25.9 inches) (H>CC, 1990). Relative sea level nse
which considers movement of the land relative to the water may exceed these estimates in areas that
are subsiding due to recent glaciations.
Accelerated sea level rise is anticipated to alter both natural and developed areas and will
require different planning and legal strategies to deal with the impacts. An increase in flooding,
coastal erosion, and salt water intrusion will result from an increase in sea level Sea level nse is
also anticipated to have an impact on critical coastal habitat, specifically wetlands. Coastal wetlands
serve as nursery areas for several commercial fisheries, buffer tides and storm surges, filter
pollutants, and provide wildlife habitat (Mitsch and Gosselink, 1986). A majority of these areas are
well protected under current regulatory schemes, but their future existence is uncertain. Wetlands
have been able to maintain themselves by migrating landward as sea level rises. This migration may
be prevented in areas with steep slopes, dense development, or engineering structures Therefore,
planning for sea level rise should consider mechanisms that will preserve this critical habitat.
A case study was conducted in Chatham, MA to identify habitats vulnerable to sea level rise
and to suggest some options to protect these resources. A geographic information system GIS) was
used to determine what coastal areas will be impacted by several different rises in sea level. Chatham
was chosen because of the community's interest in coastal issues as well as the availability of
mapping information for use in the GIS analysis. A salt marsh was selected to describe current
conditions, how those conditions evolved, and what will occur to the marsh as sea level continues to
rise. The case study reveals difficulties related to the current regulatory structure that may prevent
the maintenance of critical habitat as sea level rises.
The difficulties in conducting an assessment of sea level have identified the regulatory
limitations of preserving habitat vulnerable to sea level rise. Mechanisms which consider sea level
rise are suggested to overcome these limitations and promote habitat preservation. In addition,
guidelines for an assessment of sea level rise are presented and may be useful to local officials.
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Introduction
„
dioxide chlorofluorocarbons, nitrous oxides, ozone, and water vapor; iro
emissions are reduced considerably today (IPCC, 1990).
SPS by refreezing the meltwater runoff in the subfreezmg snow (Meier, 1990).
The current rise scenarios for global
9
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Table 1. Summary of Key Greenhouse Gases Affected by Human Activities
Atmospheric
concentration
Pre-industrial (1750-
1800)
Present day (1990)
Current rate of change
per year ^^^^
5=====================
Atmospheric
lifetime (years)
Carbon
Dioxide
ppmv
280
353
1.8
(0.5%)
=====
(50-200)*
===
tlethane
ppmv
0.8
1.72
0.015
(0.9%)
10
======
CFC-11
pptv
0
280
9.5
(4%)
i
65
======
CFC-12
pptv
0
484
17
(4%)
=======
130
____—= — =====
====&——
Nitrous
Oxide
ppbv
288
310
0.8
(.25%)
============
150
===========
ppmv = parts per million by volume; ppbv = parts per billion (thousand million) by volume;
pptv=parts per trillion (million million) by volume.
* The way in which CO2 is absorbed by the oceans and biosphere is not simple and a single value
cannot be given.
(FromlPCC, 1990)
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Figure 1. Estimates of Future Sea Level Rise
4.0
m
e
Ul
Ul
oc
Ul
Ul
S
EPA (1983) High
• EPA (1983) Mid-High
IPCC (1990) Low
WMO(1M5)Low
• OMd Volume E^imau of Meier (1985) Augmented With Therm., Exp^ion E^ima^ of NRC (1983)
SOURCES:
Environmenu, Protection Agency. 1983. Project^ P^ ..,. T .„.„:„ Washinglon( D.c ; ^
Scientific
Meier, M.F. 1990. "Reduced (.ic) Ri« in Sea Level." Nature. 343:115.
Meier, M.F. et „. 1985. G..ciere, Ice Sheet, and V, T n... W.ahington, D.C, N.tion-U Academy Rre».
fcK^l^
rDS^ion.^^;^^" h $M UVd ReSUWl18 from *»—- AtmOSPheric O-fc- ««*.• Changing
of Carbon Dioxide and i
World Meteorological Organization. 1985. Intemation.1 A— _____ .
Variations and Associated Imp.,... Geneva: WMO.
jreenhouseGases in
(From Titus, et al. 1991)
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to coastal habitat and coastal lowlands as sea level rises. These impacts will be discussed briefly to
establish the significance of sea level rise to each.
Impacts of Sea Level Rise
Sea level rise may physically alter natural and developed coastal areas and require different
planning strategies to account for these changes. The impacts of sea level rise "^ ^^f*.
flooding inundation, erosion, and salt water intrusion (Titus and Greene, 1989) All of these
fm^actf are relevant to sea level rise because each is superimposed on the global, mean waterlevel
Davidson and Kana, 1988) yet each will occur to varying degrees depending upon the physical
conditions.
Flooding
Most of the structural damages and financial losses caused by large storms such as hurricanes
and northeasters, are due to flooding. Flooding of coastal lowlands is expected to grease with
rising sea level because each storm surge or tidal exchange will occur on a higher base level (Titus
et S U91) Tte increase in tidal flooding may accelerate upland loss, cause vegetation changes
wkhin salt marsh ecosystems and, in many instances, eliminate salt ^^^f^-^^^
are currently mapped by the Federal Emergency Management Agency (FEMA) for government
subsS insurance purposes. In general, the maps delineate flood zones in relation to the impact
of the s^i tical 100 yeaTflood. The zones affected by the 100 year flood are the A-zone and the
V^-zone The A-zone is flooded by the 100 year flood, while the V-zone is flooded and subjected to
wave action and runup (FEMA, 1989). In the A-zone, flood elevation increases will be proportional
To In S^WSSl but in the V-zone, flood elevation increases will be greater than the increase
in «« level (Table 2) (IEP no date). This means that there will be an increase in the percentage ol
he Too year flood zone affected by wave action and runup. Therefore, if global warming causes an
increase in storm frequency (IPCC, 1990), then physical flood damages may escalate in both
severity and in areal extent.
Aside from the physical impacts of increased flooding, there are also economic i
associated with insuring low lying coastal property through government subsidies The National
F ood Insurance Program (NFIP) was established in 1968 to allow owners of floodI pro.property
to purchase insurance protection against flood losses and damage which is generally notAvailable
from private insurance companies (FEMA, 1989). The insurance program is administered by the
Federal Insurance Administration, a component of FEMA, to eligible property owners in
communities which participate in the NFIP. Community participation entails implementing and
ero^Tmeasures to reduce future flood risks in areas delineated to be Special Flood Hazard Areas
(SFHA) (FEMA 1989). The program was intended to prevent or discourage unwise development
within SFHA but in many instances, development has been encouraged by the guarantee of
Subsidized insurance. Rising sea level and continuation of the NFIP will result in increased
government spending of federal tax dollars to provide insurance for unwise development to a very
small percentage of the population. This spending will continue until some serious reforms are
made to consider both currently insured properties as well as properties which will be located m
SFHA as the sea encroaches.
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Table 2. Effects of sea level rise on V-zone flood elevations.
Flood
Elevations:
Present Conditions
Surge elevation = 11'
Depth of water (d) = 4'
Hw/4' = .78
Hw = 4' x .78
= 3.12'
11' + 3.12' = 14.12'
Future Conditions
Surge elevation = 12'
Depth of water (d) = 5'
Hw/5' = .78
Hw = 5' x .78
= 3.90'
12' + 3.90' = 15.90'
Hw is wave height
Hw/d is a standard used for relative wave height
Flood elevation is sum of Hw and surge elevation.
(From IEP, Inc., no date)
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Coastal erosion
Coastal erosion is probably the most noticeable effect of rising sea level. This is evident in
areas where development has been impacted or lost, and the recreational beach width has been
significantly reduced. Erosion occurs most often in large chunks associated with storms (either
northeasters or hurricanes) and will intensify if storm frequency increases as global temperatures get
warmer A rise in sea level results in beach erosion since sea level is the primary control of shore
position (Leatherman, 1989). The Bruun (1962) rule often is used to determine shoreline retreat due
to sea level rise. According to the Bruun rule the amount of shoreline retreat depends on the
average slope of the entire beach profile. However, in most cases shoreline retreat is a little
understood, extremely complicated process, and not thought to be entirely related to the slope of the
beach profile (Pilkey and Davis, 1987). As the shoreline retreats in response to sea level rise
developed areas will be subjected to increasing forces of the ocean and temporary solutions will be
used to maintain these developed areas.
Coastal erosion is only a problem if development or structures are present and become
vulnerable to erosion (Pilkey, 1980). Since coastal erosion places human development at risk there
are structural and nonstructural methods used to prevent the immediate loss of this development.
Renourishing beaches with sand and raising barrier islands in place have been offered as possible
nonstructural, cost effective manners to moderate coastal erosion (Titus, 1990). However, once
beach renourishment projects are initiated, they require long term financial commitments and
continual maintenance. The "life" of the nourished beach is usually overestimated, and the costs
associated with initial and subsequent renourishments are underestimated (Pilkey, 1988). If sea level
rises at an accelerated rate the shortened life of renourished beaches will increase both the frequency
of replenishment and the costs of these long term projects. Structural methods of protecting
development include bulkheads, seawalls, revetments, levees, and groins. These structures are
usually expensive, and do not prevent coastal erosion; in fact, they may accelerate erosion adjacent
to the structure or elsewhere within the coastal system.
Saltwater intrusion
A rise in sea level will increase the landward extent of ocean influences subjecting some areas to
increases in salinity. When saltwater intrusion is mentioned with respect to accelerated sea level
rise it can refer to either shifts in estuarine salinity or an increase in the salinity of drinking water
aquifers (Titus, 1988). In estuarine systems there is a fresh water/saltwater interface which results in
a salt wedge where less dense freshwater floats above saltwater (Edgerton, 1991). The position of
the salt wedge fluctuates within the estuary depending upon the amount of freshwater runoff into the
system and the extent of tidal and/or storm influences. An increase in sea level rise causes the salt
wedge to move further inland and convert brackish and freshwater areas to more saline
environments. The estuarine environment may also be impacted by an increase in temperature
caused by global warming that is anticipated to change rainfall patterns and alter freshwater runoff
to estuarine areas (Bigford, in press, 1991). This may have significant negative impacts if the
runoff contains pollutants because the estuary's ability to flush out and dissipate contaminants is
expected to decrease as increasing salinity reduces .circulation (Edgerton, 1991). The cumulative
impact of freshwater runoff fluctuations coupled with salinity changes may alter estuarine and
nearshore water conditions shifting fish habitat and stocks (Bigford, in press, 1991). Rapid changes
in these conditions could negatively impact some economically important, commercial fisheries.
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In coastal areas, freshwater aquifers usually flow toward adjacent bodies of water Excessive
groundwater pumping can cause a reversal of this flow and may result in saltwater intrusion when
the recharge area is in a location susceptible to salinity changes such as a river mouth (NRC 1987)
Even though saltwater intrusion is thought to be primarily drought dependent (Hull and Titus' 1986)
an increase in coastal storms combined with the elevated base for the storm surge will result in
higher flood elevations and may cause saltwater contamination of the groundwater.
Alteration of Critical Habitat
Human destruction of coastal wetlands (specifically salt marshes) has been greatly reduced
through regulations1, yet there are no provisions to protect the significant amount of coastal wetlands
susceptible to loss/impact from an acceleration in sea level rise (U.S. EPA, 1991). An estimated
7,000 square miles of coastal wetlands may be lost as a result of a one meter rise in sea level (Titus
1991). These wetlands serve as vital ecological and economic links at the land-water interface. A
large percentage of economically important, commercial fisheries depend on coastal wetlands for
nursery areas. They also buffer high tides and storm surges, filter pollutants, and provide wildlife
habitat (Mitsch and Gosselink, 1986). The importance of the protective functions of wetlands (i e
buffering high tides and storm surges) will become more apparent as larger coastal areas are
subjected to more frequent flooding and inundation.
Coastal wetlands have been able to respond to the relatively slow rates of sea level rise during
the past 5,000 years (Matthiessen, 1989). They keep pace by migrating landward if sediment
supplies are sufficient to maintain the marsh above sea level and prevent drowning (Figure 2) (Titus,
1988). The elevation of the marsh above mean sea level determines the duration and frequency of '
tidal flooding which creates the different vegetation zones; the regularly flooded marsh is known as
the low marsh, the irregularly flooded marsh is known as the high marsh, and the portion of the
marsh that is only flooded by the highest spring tides is known as the transition zone (Figure 3)
(Appendix A). As sea level rises, vegetation zones shift landward; that is, low marsh is converted
to either open water or tidal flats, high marsh is converted to low marsh, and transition/upland area
is converted to high marsh (Titus, 1988). Landward migration of coastal wetlands may be
prevented by natural barriers (steep, rocky shores) and man-made barriers (bulkheads, etc.). In the
presence of barriers, ecosystem migration is prevented as the wetlands get squeezed between the
rising sea and the barrier resulting in decreased acreage of these valuable areas (Figure 4) (Titus,
The U.S. Environmental Protection Agency (EPA) has estimated losses of coastal wetlands for
the United States (Table 3). The slightest rise scenario (50 cm) is expected to result in 17 to 43
percent loss of coastal wetlands by the year 2100; losses increase when development and dryland are
protected with engineering structures (Titus, 1991). Therefore, it is important to consider protected
shorelines versus unprotected shorelines with respect to wetlands. In areas with protected shorelines
all wetlands may be lost while in areas with unprotected shorelines the wetlands may only narrow.
The importance of this idea is that the maintenance of a narrow marsh is better than no marsh at all,
aside from the fact that length of wetland shoreline seems to be more important in providing habitat'
than the area of the wetland (Figure 5) (Titus, 1991). However, other wetland functions will be
affected by a decrease in marsh area, such as maintenance of water quality by filtering upland
runoff, and buffering both tidal and storm surges.
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Water
2075
33%
2075 MSL
LOW SCENARIO
1980 MSL
EXISTING
Figure 2. Impact of sea level rise on wetlands around Charleston, South Carolina,
as reported by Kana and others (1988). Shift in wetlands zonation along a shoreline
profile. Assuming an accretion of 5 mm/yr, the various zones of vegetated wetlands
would be squeezed, while the area of tidal flats would expand.
(From Titus, 1988)
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SALT MARSH
TRANSITION ZONES
A FEW SELECTED REPRESENTATIVE SPECIES
(NOT ALL FLORA SHOWN ARE TO SCALE)
Pi«ch
Pine
SPRING TIDE
HIGH-
Gluiwoft Sea,
_ Lavender
Perennial
Glasswott
Uroch
Rockwnd
Seauecd* Lettuce
Figure 3. Salt Marsh Transition Zones
Gross
(From U.S. EPA, 1981)
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Figure 4. Evolution of a Marsh as Sea Level Rises
5000 Years Ago
-5- Sea Level
B
Today
Sedimentation and
Peat Formation
V Current
""" Set Level
.. Past
Sea Level
Future
Substantial Wetland Loss Where There is Vacant Upland
Future
Sea Level
Current
Sea Level
Future
Complete Wetland Loss Where House is Protected
in Response to Rise in Sea Level
Future
-t. Sea Level
"" Current
Sea Level
(From Titus, 1988)
11
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Table 3. Impact of sea level rise on the United States (billions of 1988 dollars)'
Sea level scenario
If no shores protected
Land lost
Wetlands lost (%)
Dry land lost (sq mi)
Value of lost property
Cost of coastal defense
50cm
17-43
3300-7300
78-188
0
If densely developed dryland is protected
Land lost
Wetlands lost (%) 20-45
Dry land lost (sq mi)
Value of lost property
Cost of coastal defense
Open coast
Sheltered waters
If all dryland is protected
Land lost
Wetlands lost (%)
Dry land lost (sq mi)
Value of lost property Q
Cost of coastal defense ?
2200-6100
?
32-43
25-32
5.13
100cm
26-66
5100-10300
165-451
0
29-69
4100-9200
?
73-111
54-92
11-33
50-82
0
0
200cm
29-76
8200-15400
411-1407
0
33-80
6400-13500
7
194-285
145-203
30-101
66-90
0
0
9
(From Titus, 1991)
Figure 5. Although a one meter rise would
generally reduce area of wetlands, it would not
necessarily reduce the shoreline length or
wetland-open water interface. A: Original
condition. B: With 1 meter sea level rise.
(From Titus, 1991)
['•''I Marsh
3'| Contours in maters
12
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The threat to sea level rise to coastal wetlands can be offset by two factors: 1) lowland^flooding
preservation of current coastal wetlands.
Possible Strategies
Entrenchment versus Retreat
elsewhere.
nen
re so.
The entrenchment versus retreat issue also concerns the fate of wetlands and other coastal
™
more so.
retrauo avoid Mure difficulties, and will probably allow the survrval of valuable coastal
wetlands.
13
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Table 4. Options for allowing wetlands to migrate landward.
Policy
Description
I. Prevent areas from being developed
(undeveloped areas only)
1. Prohibit development
2. Buy coastal land
II. Allow development
A. Defer action
3. Order people out later
4. Buy people out later
5. Rely on economics
B. Presumed mobility
6. Prohibit bulkheads
7. Leases
Statutes or regulations prevent construction in particular areas.
conservancies purchase land onto whi
Ignore sea level rise on the assumption that the government will
fTtnl7^rm™ StmCtUreS When « le"el riseTeno^
for them to interfere with landward migration of ecosystems.
Ignore sea level rise on the assumption that the government buy
ou properties when sea level rises enough for them to interfere
with ecosystem.
End subsidies to coastal development but otherwise ignore sea
level rise on the assumption that governmental action will never
be necessary because people will voluntarily abandon their
properties, provided that the government does not subsidize the
protection or construction of such property.
Do not interfere with private activities today, but explicitly
notify property owners that as sea level rises they will not be
allowed to construct bulkheads to protect their properties.
Do not interfere with private activities today but convert (with
compensation if necessary) property rights of current owners to
long-term leases which expire after 99 years, or conditional
leases, which expire whenever the sea rises enough to inundate
the property. Underlying ownership could belong to the public
or private conservancy group.
(From Titus, 1991)
14
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Shifting development away from coastal lowlands through legislation may present problems with
the constitutional takings clause under the 5th Amendment of the Constitution. The Supreme Court
has recently decided to hear a case in South Carolina in which a landowner is suing the state
because of a state law which prohibits development too close to the shore (Greenhouse, 1991). The
landowner is claiming that the government is "taking" his property by not allowing him to develop
his oceanfront lots, and therefore, he deserves just compensation pursuant to the 5th Amendment.
In the previous Supreme Court takings case in 1987 the majority opinion (5 to 4 vote) ruled that
there was no taking, however the two Justices who wrote the majority opinion have retired and have
been replaced with two Justices who will most likely vote the other way. The outcome of the case
will play a significant role in determining what legislative actions can be taken to encourage retreat
and habitat preservation as sea level rises without having to compensate affected property ownners.
Planning
A new approach to wetlands protection will be necessary to deal with accelerated sea level rise.
An effort will have to be made to look beyond preserving the wetlands presently in danger and
devise a way of protecting new wetlands from future threat (Fischman, in press, 1991). It is
uncertain how this will be done given that some of today's wetlands are not protected by laws and
regulations, much less areas that are not yet wetlands. In New England, the following planning
measures for sea level rise have been recommended:
1) require coastal community post-disaster plans so citizens and officials will know
how sea level rise may affect them;
2) delineate sea level projections on all town maps;
3) inform the public of the risks surrounding long term sea level rise;
4) allow property owners to sell their property to government or a conservancy and
lease it for 50 or 100 years;
5) investigate legal rights of lands coming under state jurisdiction due to changing
tidal ranges; and
6) prohibit hard shoreline protection structures, except when the coastal area protected
is in the public interest (Matthiessen, 1989).
The planning window for dealing with most coastal activities related to sea level rise is 20 to 50
years. During this time frame many of the structures and activities within a town will seek permits
from state and local regulatory agencies (IEP, no date). Therefore, regulations should be modified
today to avoid or at least minimize any possible takings problems, and impacts associated with
activities or structures that would be affected by a future sea level rise.
Federal and state regulatory agency involvement will increase with the increasing magnitude of
sea level rise impacts (Davidson and Kana, 1988). However, local governments have a chance to
establish their own policies concerning sea level rise today. The policies can be initiated through
zoning ordinances, building codes and local tax structure (Davidson and Kana, 1988). Policies
created by local government or agencies will probably be much more accurate and helpful than those
established by state or federal agencies, and will reduce dependence on the fiscal uncertainty of such
agencies (Davidson and Kana, 1988).
15
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Currently, planning for sea level rise on the local level is not a top priority in most cases. Most
activity is related to dealing with issues as they surface (so called, "putting out the fires") rather
than long range, speculative planning. However, the uncertainty of sea level rise should encourage
policy establishment of some type to address the impacts. Even if the policy is one of "no action"
or "hands off," this will eliminate the inevitable .series of "fires" that will result from accelerated sea
level rise by notifying people today of what action will be taken when sea level rises to a certain
level. Local responses to sea level rise will depend upon various time frames of:
-the rate of sea level rise and related change
-useful life of structures and infrastructure
-financial life of structures and infrastructure
-political tenure of decisionmakers
-technological life and technological changes (Davidson and Kana, 1988)
In many cases, sea level rise is an issue surrounded initially by skepticism, but natural occurrences,
such as storms, will produce noticeable changes in the physical conditions of the coast related to sea
level rise and will increase interest and concern (Davidson and Kana, 1988). Recent storms on the
east coast (Hurricane Bob, August 1991 and two northeasters during late October and early
November 1991) resulted in a large amount of property damage due to the dynamic response of the
shoreline. Increased citizen awareness of coastal hazards immediately following such storms should
be considered an opportunity to make some regulatory changes which integrate sea level rise and its
associated impacts.
Case study-Sea level demonstration project
Introduction
The goal of this demonstration project was to select a coastal community, assess the possible
impacts of accelerated sea level rise on its critical habitat and lowlying coastal property, and identify
possible steps to address sea level rise that the local government could take to protect their
resources. Important criteria in the selection of a town were: 1) the general receptiveness of the
community to the idea of sea level rise and its associated issues, 2) the presence of wetlands or
other habitat vulnerable to sea level rise, 3) mapping information, and 4) the proximity to Boston,
MA (location of the EPA Region I offices where this internship project was conducted). These
criteria were met by consulting with EPA personnel to discuss their ideas for a good site, and any
possible contacts that might assist in getting the project underway. Initially, there were two possible
study sites (Barnstable and Chatham) both located on Cape Cod, MA that satisfied the criteria.
However, Chatham was chosen due to the availability of mapping information necessary to
incorporate a GIS.
Chatham is located on the southeast corner of Cape Cod (Figure 6). Accelerated sea level is of
interest here because of a recent breach of the Nauset barrier beach which has resulted in impacts
similar to those anticipated with an increased rise in sea level. Nauset Beach, locally referred to as
North Beach, a barrier island to the east of mainland Chatham, was breached January 2, 1987
during a northeaster (Wood, 1988). The breach caused physical, chemical, and biological
16
-------
Assessing Impacts of Sea
Level Rise in Chatham, MA
-------
changes in Chatham Harbor and Pleasant Bay, and intensified erosive forces along the shoreline
Prior to the breach tidal flow in Chatham Harbor was constricted by North Beach overlapping with
Monomoy Island which prevented full tidal exchange and impacted the bay's resources and wL
quality (Wood, 1988). The breach increased tidal range within Chatham Harbor and Pleasant Bay
which is analogous to the effect of sea level rise, although it is not identical3 (Figure 7)
Subsequently, tidal exchange has improved water quality and the bay's resources, but the increased
tidal range has caused significant shoreline erosion and some marsh changes which are similar to
those expected as sea level rises.
In Massachusetts, relative sea level has been rising at a rate of approximately 2.9 mm/year for
he past 60 years (Giese etal., 1987). This rate is expected to increase during the next century due
to global warming and is anticipated to impact coastal resources. Chatham has been losing about 1
acre of up and per year due to relative sea level rise (Giese eTal., 1987). This upland lost has
undoubtedly increased since the breach and a further increase is anticipated as sea level continues to
rise. The breach has eliminated most of the protection which North Beach had afforded Chatham by
allowing open ocean force waves to enter Chatham Harbor. This has transformed the calm
navigable harbor into an area hazardous to navigation and has caused the eastern shore of Chatham
to erode dramatically (Wood, 1988). The breach of North Beach was not unexpected; it had been
predicted in 1978^ There was also research that had detailed the geologic changes of North Beach
during the last 150 years (Wood, 1988). The breach is part of the process of inlet formation
migration and eventual inlet closing which many barrier beach/island systems undergo This'allows
large quantities of sand to enter the sound and form a large flood tide delta. After the inlet has
closed, the flood tide delta will eventually be incorporated into the existing island and provides a
migration surface for barrier island retreat. As sea level rises North Beach will continue to migrate
landward until it eventually welds onto mainland Chatham at which time the erosive forces
experienced today will be standard (Wood, 1988). An increase in erosion will intensify the threat to
development that already seems to have reached immense dimensions.
In response to the increased erosion, the Town of Chatham took an official "hands off" policy
and decided to let nature take its course. The owners of property directly affected by erosion
caused by the breach felt the town should allow them to protect their property in any manner in
which they saw fit. The property owners interest in the issue intensified during the winter when
northeasters sent 10 to 15 foot waves through the inlet and eroded large chunks of the shoreline but
interest waned somewhat when fairer weather redeposited some of the sediment removed during'
storms (Wood, 1988). The controversy between the town and the property owners resulted from the
uncertainty of the geologic classification of the property which determines whether or not any
protective structures are allowed by law (Appendix B). The Town of Chatham was not entirely
responsible for this controversy; they were merely following the regulations set up by state and
federal government. However, some of the controversy could have been avoided if some definitive
decisions had been made prior to the breach concerning the potential impacts, and what preventive
measures, if any, were allowed. This is analogous to the problem with accelerated sea level rise in
some respects; the confidence in estimates of sea level rise is not sufficient enough in some cases to
make definite predictions of the anticipated impacts, much less establish policies to address these
impacts. Indecision seems to prevail even though research has identified some highly probable
impacts of sea level rise that may be extremely costly in the future if no prior planning is
conducted. 6
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Change in tidal range
Absolute sea level
rise
New
high tide
New
low tide
+6"
-6"
Original tidal range
High tide
Low tide
New
high tide
New
low tide
Area
Inundated
by SLR
Figure 7. Comparision of a change in tidal range and a change in .sea level
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Methods
Chatham was chosen as the study site due to community interest, but there were additional
criteria tor site selection. A salt marsh ecosystem was chosen within Chatham to examine the
potential impacts of sea level rise. The site was visited with EPA staff to make an initial
qualitative assessment of marsh resources. The marsh chosen is located on the eastern shore of
Chatham along Morris Island Road adjacent to Stage Harbor. The dike that the road is built upon
was constructed in 1958 by the U.S. Army Corps of Engineers to prevent Stage Harbor from filling
with sand (Wood, 1988). The dike connects Stage and Morris Islands with mainland Chatham and
hteraUy paved the way for development on each of these islands. The marsh system was examined
to determine if the breach had caused any changes as well as to determine what effects accelerated
sea level nse may have on the marsh. Site visits were intended to construct a narrative description
of current marsh conditions. This description was used to propose how the current marsh conditions
evolved and how sea level rise may impact the area.
The availability of mapping information was important to the project in order to integrate a
geographic information system (CIS). By using a CIS, various sea level rise scenarios can be
projected onto different data layers (a data layer consists of information of one type e g roads
structures, or elevation contours) to determine what areas are inundated by sea level rise or
subjected to increased flooding. The single most important class of data is elevation contours
Elevation contours found on typical maps generated by the United States Geological Survey (USGS)
are presented in ten foot intervals. In order to determine if any low lying areas are affected by
slight rises in sea level, more precise contour intervals (either one or two foot intervals) are
necessary. This criteria narrowed the number of possible sites to Barnstable and Chatham MA
There were difficulties involved in obtaining the mapping information; in one case the computer
work was still in progress, in the other, there were concerns of the legal implications of releasing
the data. Therefore, deadlines were set up for obtaining the mapping information and finalizing a
study site or sites. Chatham was selected as the study site because relatively complete mapping
information was thought to be readily available. The CIS was to be integrated into the case study
but mapping data for the field site could not be obtained. However, data for another nearby coastal
area ot Chatham was obtained and will be given as an example of how a GIS can be used in
assessing sea level rise.
Marsh Conditions
The salt marsh that lies east of the dike is low in elevation, has hummocky zones of vegetation
and is protected from the harbor by moderately sized dunes. The microtopography within the marsh
is highly variable as is indicated by the atypical vegetation zonation. Vegetation zonation is
determined by hydrologic regime (flooding) which depends on marsh elevation above mean sea level
(U.S. EPA, 1981). There are three general zones within salt marshes: 1) the intertidal zone (tidal
flats and low marsh), 2) high marsh, and 3) transition zone (see Figure 3). The intertidal zone is
flooded twice daily by the ebb and flow of normal tides; the high marsh is either flooded by spring
tides or not flooded at all during some seasons; and the transition zone is flooded only during
extreme storm tides (U.S. EPA, 1981). These flooding characteristics cause varying environmental
conditions which result in different types of vegetation. In the study marsh, the areas of high and :
low marsh are not distinct. This may be related to the alteration of marsh hydrology caused by the
20
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however stoceTs burred 35 years ago, toe effects today are probably rnstgmficant.
likely in the event of accelerated sea level nse.
Possible Impacts of Sea Level Rise
21
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[uality and shifts in salinity may jeopardize
Conclusions
The exposure of Chatham to open ocean-force waves and the increase in tidal range within the
harbor has revealed effects similar to those anticipated with a rise in sea level A kJfetoSalt
marsh was identified and examined to determine its vulnerability to sea level rise ColoSon of
--V^
hat marsh migration is likely to occur as sea level rises. Presently? any ^iTSS^^
^tae fou^^SS^cf8 ^ S6em t0 ^ Primarfly SteCP Sl°PeS However, kiSuk to
subjects the area to much higher wave energy conditions.
Use of a Geographic Information System (GIS)
Introduction
rise Itwn £ H f " exhlblt h°W * GIS Can be used in an Assessment of sea level
nse (two, four, and six foot scenarios) and its impacts. The use of GIS is increasing in popularitv
with resource planners and managers due to its ability to establish the "big pictoe " P *
or issue of interest. A GIS is not capable of—J-'-i'- - - ^
hut mo, K f i • -j T • ~"r *" ""fe exactly what may occur as sea lev
but may be useful in identifying possible impacts. In order to utilize this tool in everyday „
technTgy6"16111' ^^ StratCgieS ^ ^ ^^ tO overcome the Current cost limitations
Procedure
S"8 v^K y COmPleied Comprehensive mapping of the entire town of Chatham The
was initiated by several different departments within the town government (Robert '
To11' Pers°hnal.cfommunicati-)- There were a few projects which had invo/ved obtaining
topographic information, but this information was of little use to any other branch of
government due to its specific nature. Therefore, various departments pooled piieS monies for
oTEoltn 7 ^ "^ for aerial P^ography and to o£rin digital fiTof Z Sf
of the collected information. Interdepartmental cooperation financed 65-70% of the project and
convinced the voters to finance the remainder of the project.
An index of all digital map files/paper maps was obtained from the town to determine which
area to concentrate on. Mapping information was not available for the study site (see previous
section) because the consultant had not finalized the work for this area. Therefore, an area that had
been completed was selected and obtained as digital files in AutoCAD (Computer Assiste?DrawinS
'
100 dS a' ^ lGS SdeCted C°Vered 4 dfaWingS °r tileS With «* ^ntag nealy
The desired data layers were selected and the files were saved as .dxf (drawing exchange files)
to allow import into Arc/Info (EPA GIS system). Once the files had been imported to Arc/Info, the
22
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layers of each tile were broken into coverages which is the way Arc Info stores mapped ^
TtefeSi^in AutoCAD drawings do not have the same topological requirements as Arc/Info
coverages Therefore, extensive Siting was required to create whole, connected arcs out of line
friS 'as weU as polygons, or area features. In addition, extensive contour coding was required
as w , .
Following coverage editing, the 4, 6, and 8 foot contours were attached to tte 2 foot contour
whicTwal assumed to be mean sea level. This assumption was made because the shore me found in
The digM files represents mean low water (Robert Duncanson, personal ^™^y*^
tidal rLge is 3.7 feet. Therefore, mean sea level was approximated by adding one half of the tidal
ranee to mean low water resulting in a shoreline location at approximately the 2 foot (1.85 )
Sou ° A^lygon coverage was then created for each sea level rise scenario to determine what
contour. _ . _
area would be inundated.
Results
The rnaus represent an area of South Chatham located on the shore of Nantucket Sound. The
maoS Z e^ompTsseTapproximately 1100 acres and extends from the Harwich Chatham border
S^BuSsf cTk and Hiding Beach. The maps generated for each sea level nse (wo four and
?x feet) approximate the area that may be inundated by an immediate nse in mean sea level
Seurei 8A 8B 9A 9B, 10A and 10B)*. Approximate acreages of the areas that will be inundated
by S scenaS'hate bein estimated. A 2 foot rise in mean sea level will --date approxim^
132 acres- a 4 foot rise approximately 162 acres; and a 6 foot nse approximately 200 acres. Each
rise wnHmpactTouses and other structures by either inundation, increased possibility oflooding,
Nation from mainland areas, or saltwater intrusion into freshwater supplies. As expected, these
imS wUlJrLe with increasing sea level. A large amount of tidal marsh m this area will be
ZaSed by Kristin sea level. These areas will either shift landward, get squeezed between the
nigS development, or be inundated entirely. These impacts depend on the nse^scenano
bu moreimportantly the rate of rise which is not depicted by the maps. There will also be impacts
on the NSet Sound shoreline. Engineering structures in this area may be ^I™^*™
°n 1 levd and require reconstruction or at least increased maintenance. A groin field is located on
hordirSta^^Harwich/Chatham border. The present elevation of these structures was not
avaSSe but each rise scenario indicates that the shoreline may simply retreat around these
suture leaving them as hazards in the ocean. Each rise scenano displays inundation of the
£S££ area to varying degrees. This probably would not be *e^^^
will most likely retreat landward in response to nsmg sea level and not simply be ^^.
beach response will depend on the rate of sea level rise, future sediment supplies and the effect of
engineering structures on sediment movement. It is important to recognize that these are
approbate impacts and there are limitations of applying this technology to detect changes in the
coastal system.
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ESTIMATED IMPACTS FROM
A/ Berm, Jetty or Retaining Wall
A/ Building
^v Dirt Road
A/ Paved Road or Bridge
Tidal Marsh or Swamp
«•
v^k^tei.
^W"'iO
risPe, in sea
P1ease
.
ions of the tidal marshes are " alrM* .;ii.n> ;' ,
level, and therefore ^ only addiUona! areal K i J«Zi?\der- Wal-fr, a> m
in sea level are shown auamoim a™as that would be inundated with
-
thai
sea
a rise
EPA Region I
Scale 1:12,000
1991
1 inch = 1000 feet
FIGURE 8A
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2 FOOT RISE IN SEA LEVEL
River or Water
A/Estimated Mean Sea Level
(2 foot contour)
Additional area inundated
by rise in Mean Sea Level
This map is to be used for general planning purposes ONLY. Locations
of current and predicted sea level are approximate and may contain error
Original data courtesy of the Town of Chatham, MA. Sea level rise scenarios
anf maps developed by contract sta f in conjunction with EPA Region I
later Management Division personnel. Tor more information aboul this
map please contact:
Geographic Information Center
EPA Region I FIGURE SB
PIM-91
Boston, MA 02203
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ESTIMATED IMPACTS FROM
A/ Berm, Jetty or Retaining Wall
A/Building
A/ Dirt Road
A/ Paved Road or Bridge
o
Tidal Marsh or Swamp
fs
level, and therefore
in sea level are shown.
o
arshes
that
rise
SPA Region I
Scale 1:12,000
Draft November, 1991
1 inch = 1000 fed
FIGURE 9A
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4 FOOT RISE IN SEA LEVEL
A River or Water
A/ Estimated Mean Sea Level
(2 foot contour)
$888: Additional area inundated
by rise in Mean Sea Level
\
this map is to be used for general planning purposes ONLY.
\ehaei::1,'.vtfAWi?v;.'vla s.
map please contact:
Geographic Information Center
EPA Region I FIGURE 9B
Boston, MA 02203
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ESTIMATED IMPACTS FROM
A/ Berm, Jetty or Retaining Wall
A/ Building
A/ Dirt Road
A/ Paved Road or Bridge
Tidal Marsh or Swamp
Tx;-.7-r Sk°ws a Possible scenario for the impacts of a rise in sea level.
The area shown is a portion of the town of Chatham, MA. Please note that
PfJJi101!8!,,!0 I if |Mdal marshes are already partially under water at mean sea
in sea level are h6 °D addlllonal areas ^hat would be inundated with a rise
EPA Region I
Scale 1:12.000
Draft November, 1991
1 inrh = 1flfl ft font
FIGURE 10A
-------
6 FOOT RISE IN SEA LEVEL
A/ River or Water
A/ Estimated Mean Sea Level
(2 foot contour)
$$$$: Additional area inundated
- by rise in Mean Sea Level
. ,
' «».«,.'" ,,.,r O
*. » «b 1 A. A n A AAnTAf^t"
map please contact:
Geofiraphic Information Center
EPA8 Region 1
PIU-OI
Boston, MA 02203
FIGURE 10B
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Limitations and Benefits
woufd^rnjdafedtr:; fr^fri^ ^ ™™ «ievei -~ * «. ^
n
* a "SnT«y fT r°JeCting differem ^ leVdS °nt° flX6d C0ntour «**»*»• * si-** t
taking a snapshot of the area at one point in time. This may not reflect any readjustment of the
contours as sea level rises which may be caused by an increase in tidal inundation,'storm su'ge
conm rg'h ^^ energy,(16;' S 2 f00t S6a levd dse does not necessarily indi^e hat the 4 foot
the slopes that "restrict" sea level rise may^m^^
eadjustment or "slumping;- of elevation contours will occur which may result in a more gradual
s ope This may increase inundation (by rising sea level), but may also provide a slope that will
allow landward migration of the tidal marsh. Using a GIS may not give the exact location ofTe
sea, but will give a better idea of the results of different sea level rises. This may allow plannTng to
integrate S ilsue S^T*"*' PrCdeCti°nS °f S6a level rise should be on ^ town map kyjrs to
1989). Even though there are slight limitations to using a GIS in assessing^seTleve^rise^thT'
benefits of such a system in linking local government activities (permitting, planning etc') toeether
and establishing the "big picture" of current conditions as well as possible future con'dWons afe
inVcu.U3.DlC. In ciQClltlOn to thp^JP hpn^fifrc it cKfMilr! KQ «-»Ai+rtJ-j 4-u,.* j A. e Deneilts it snould be noted that due to the increased popularity and
knowledge of the usefulness of GIS, new systems are becoming more user friendly.
Cost limitations
The cost involved with establishing a GIS will probably be the most prohibitive feature of
conducting such an analysis. Several creative strategies will be necessary to enable the use of such
fn^n i 7Ue !° t?e re°ent mCreaSe in the number of Afferent GIS systems and the increase
in technology, system hardware has become reasonably affordable. The most prohibitive cost to
establishing a system is obtaining data of desired detail (Marcy Berbrick, personal communication).
Data costs could be minimized if a state or regional planning agency became involved In
Massachusetts, studies using GIS could be initiated by a federal agency, and the costs could be
shared between the state coastal zone management office, the Cape Cod Commission (a regional
planmng agency), and the coastal towns themselves. After a decision has been made concerning the
necessary data the amount of financial involvement will be left up to the town. A town may decide
to purchase and share a GIS system or just the data with another town in order to decrease the initial
costs. Such an effort may convince voters that a GIS would be beneficial to the town and result in
funding allocation to complete the project. As this technology becomes more available and the cost
declines, these types of projects will be easily implemented
Conclusions
GIS can be used to assess the possible impacts of different sea level rises. The procedure
conducted with the mapping data in Chatham was probably not the most efficient, but does establish
a general idea of possible sea level rise impacts and suggests that long range planning will be needed
to address some of these impacts. Creative strategies can be used to overcome initial costs
limitations of a GIS and may be used to convince voters of the utility of such a system. The
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Options for Addressing Sea Level Rise
particular local situations.
any habitat that might have been preserved if the structure had not been bmlt.
The dramatic acceleration of shoreline erosion in Chatham, directly west of the breach in North
B Jh haSati some of the same entrenchment responses that may occur as sea level rises.
uJht ^ereTrisK vTew the inlet separating North and South Beach. This renewed interest in
^etment ^rZlTbut with cost' anticipated to be clos* to $1 mfflion the town ,s requestmg
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assistance from FEMA. If assistance is granted, the federal government will pay for 75% of
construction costs, and Chatham and the state will split the remaining 25% of the costs with the
town alone responsible for all future maintenance costs. If the project does not reSve Serai
approval it wil be funded entirely by the town and construction will begin inTa^l^L
Wood, personal communication). In defense of the town, this may be the only alternative sini
here are revetments located along the shoreline to both the north and south which will con tinS to
focus storm waves toward the bluff, sustain erosion and threaten Main Street.
***** "** not be ** °^ economically viable resource
6 nSe' ™6re m °ther reS°Urces found on ^ coast *hich aS
mav d, recreatl°nf beach areM« or Wstorical st™tures. Recreational beach areas
may dnve the local economy, at least seasonally and therefore will be a valuable resource whicT
may warrant protection as sea level rises. "Protection" for recreational beaches may be
C f h renourishment' but *e long term financial commitments should be compared
6 H tOUnSm reVenUeS> HiSt°riCal StrUCtUreS ^ "^ be economically important
i, th n h , T°,n ? Pr°teCt SUCh a StrUCtUre Should consider whether <* not protection
s m the public interest and if the type of protection needed would prevent future maintenance of
another valuable resource. It may be helpful to establish some cause and effect relationships of
projects to protect a particular resource and its effect on all of the other resources. This may give a
better idea of where an economic assessment should be focused. In general, responses to s2 £S
rise which might impact these resources should consider the long term implications of the
protection.
**** * ** land/water interface, engineering structures should be
in areas where wetland migration is likely to occur. It is important recognize that
. ^lA6 10St ^ t0 natUfal barrierS (le" Steep Sl°^' Therefore'prmectfon of
Proh h r, , d 5e a *? Pn°nty in °rder t0 preserve as much of *** h*bitat as possible.
Prohibiting hard structures may be acceptable in undeveloped areas, but there will be problems in
deve oped areas which have been "grandfathered" under present regulations. The current
regulations can be altered to require an overlay zone (U.S. EPA, 1991) that will increase the
setback regulate long term development, and allow unimpeded ecosystem migration within the
si levd rise Z°ne W inCOIp°rate both recent md anticipated shoreline changes caused by
In developed areas, construction of new bulkheads should be allowed only where they will not
prevent marsh migration, and if any bulkheads are damaged more than 50% then reconstruction
should be prohibited and structure removal required (Klarin and Hershman, 1990) This type of
regulation would probably be more feasible. A bulkhead prohibition will have to emphasizethe
importance of ecosystem preservation to the public health, safety, and general welfare (Fischman, in
press, 1991). Such a regulation should also address the economic uses of property if the regulation
deems the property unbuildable. Currently, these requirements are sufficient to avoid a challenge of
a regulatory takings under the Fifth Amendment of the Constitution. However, the U.S Supreme
Court has recently agreed to hear a case concerning a regulatory taking, and may redefine the
authority of state governments to protect public health and safety (Greenhouse, 1991) If the Court
makes a decision, it will either maintain its current position on regulatory takings, or will broaden
its interpretation of regulatory takings and allow the private property owner to obtain compensation
for restrictions placed on their property for the good of the public
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be inconsistent with regulations within the buffer.
long term conservation.
33
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sea level rise policy has been proposed in Massachusetts which will require any construction in thP
100 year floodplam to be evaluated for the effect of a relative sea leve? rise $A CZM ?Q8Q\ ™
SwatTd8 , lanHWaid bOU"daiy " the mea" 'OW water U"e which wiuTroba^y not move
Guidelines for Sea Level Assessment
The case study generated the need for some guidelines or a procedure to assist a
assess the impacts of sea level rise. These guidelines are presented below The^co
impacts of sea level rise (presented in the introductory sections of this report) "
frol theT Pr°POSed t0 d£al With Sea level rise" Although some of the info™
to
and
to —* " Political consntsd
Education
P°tential impacts of sea level rise is essential in estabUshing a
^^
.mportant m establishing an understanding among the public that regu,a™*
34
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deal with these impacts. The responses to sea level rise (entrenchment, retreat and all of the
variations) should be presented along with the multifaceted implications of each to emphasize the
deferences between what are conceived to be the accepted methods and their alternatives. Pubkc
eduStion is also important in getting the support of those people (town citizens) who appropriate
funds for programs that address sea level rise.
-The public should be informed of the historical basis of sea level rise and why the atmospheric,
greenhouse effect is anticipated to accelerate sea level rise.
-An emphasis should be placed on the uncertainty of accelerated sea level rise and the costs
associated with taking action now versus taking action in the future.
There is a need to emphasize the dynamic nature of the coastal environment and how it is likely to
claTe witi!TincrL? in sea level (can cite a specific event, such as the breach of North Beach, to
emphasize the possible impacts of sea level rise {both physical and economic}).
Research
Research is an integral part of identifying the coastal systems and what activities that need to be
managed within the systems that may be impacted by sea level rise. It is also necessary to _
determine the "big picture" of the range of possible impacts. This information will be necessary to
estoblish effective regulations or planning measures. Research activities should be comprehensive,
but do not have to be extremely detailed to identify possible impacts. Some of the recommended
"research" may already be a part of the daily activities of town government and will simply need to
be networked together. Studies of sea level rise impacts conducted in similar locations may
supplement the local research effort.
-A shoreline inventory should be conducted to identify biological and geological characteristics.
Developed and undeveloped areas should also be identified with respect to the biological and
geological characteristics.
-Coastal processes (erosion, flooding, inundation, etc.) should be monitored (ffiP, no date) to
identify changes related to sea level rise. These activities can be carried out by networking existing
local government efforts together to fill in the gaps and establish a larger local interest in sea level
rise. Some of the long term, less technical monitoring can be carried out by concerned local
residents.
-Estuarine salinity changes and water quality should be evaluated. This can be done by recognizing
certain indicators such as a change in the biological organisms and whether or not this change is
influenced by salinity.
-An assessment of the economic impact of the different sea level rise scenarios is needed. This can
be conducted after initial research has identified habitat and its relative location to developed and
undeveloped areas.
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Mapping
Mapping of coastal areas is essential to research and planning for sea level rise The usability
and justification of the relatively high costs of mapping isstrengthened by itslffitive^ess f "
research and planning The use of a geographic information system allows integration of several
. bl§ ftUre"' F°r 6Xample' ^^ hazard «" can be overlayed on^he
" °f * Site SpedflC r^ul^ons wiU be
more
-Accurate, large scale mapping of coastal areas from low level aerial photography may assist in
ground £ t0 idemify 10ng tCrm SUbtlG ChangeS that m difficult to monitor on the
-Elevation contour data are most important because they will reveal the area that may be impacted
by a modest rise m sea level. This will indicate how much upland, marsh or development is below
a certain elevation and how much of a rise in sea level will be required to impact the area The
elevation contours are needed up to either the 10 or 20 foot contour depending upon the tidal range
For example, if tidal range is +/- 9.5 feet then the 10 foot contour will only reveal 5 feet of
dryland that may be impacted.
-The use of a CIS can integrate all data layers and project sea level rise onto these layers (i e
zoning, habitat, structures, etc.) to determine the potential impacts.
-Sea level rise scenarios can be also be projected onto FEMA NFIP floodplain maps to determine
future flood elevations. This will assist in directing development away from these high hazard
areas.
Planning and Policy Implementation
Planning for sea level rise weighs the risks associated with the uncertainty of global wanning
The costs of implementing some type of management strategy today to deal with sea level rise
tomorrow are far less than the costs associated with implementing a management or mitigation
strategy after sea level has already risen. Planning efforts will integrate the information generated
from research and mapping efforts, but policy implementation will depend primarily on the
effectiveness of the local government to convince the public that these policies are necessary.
-It is necessary to define what activities can be carried out in the immediate future, and base future
goals and activities on this original idea.
-Comprehensive long term planning needs should be listed and prioritized to construct some feasible
goals within a specific time table (IEP, no date).
-Existing regulations can be examined for localized sensitivity to sea level rise to determine if
changes are necessary or feasible. Decisions will have to be made to determine whether or not the
effort of altering regulations now to consider future sea level rise will be more beneficial than
dealing with it as it happens.
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-The planning window for sea level rise is 20 to 50 years in order to deal with development and
structures that may be impacted by sea level rise in the future (IEP, no date).
-It is important to find out what other communities are doing to deal with these issues. It would be
beneficial to see if policies intended to address impacts of sea level rise function as they were
planned (e.g., has a policy of presumed mobility held up in the courts, or has the bulkheaduig
prohibition functioned anticipated). This will give an idea of how similar policy proposals can be
altered to function in a manner suitable to the needs of the town.
-Local officials should determine if additional steps beyond presumed mobility, a bulkheading
prohibition, or sea level policy are necessary to preserve critical habitat as sea level rises.
-The costs of planning implementation will be linked to the type of sea level policy that is adopted.
If a policy simply networks existing legislation and agencies together the costs will be minimal.
"Wait and See" policies are risky because historical information indicates that sea level is likely to
continue rising to a level which will pose a threat to development and critical habitat.
-If a plan of no action is implemented, the town will still be the bearer of some costs at some time
in the future. These costs may include cleanup after storms, building engineering structures, or oss
of fishery habitat and therefore income to the local fishing industry. The costs of inaction need to
be weighed against the costs of a plan and its implementation.
-The political climate will probably be more conducive to a sea level policy following a storm or
devastating event which is clearly related to sea level rise (Titus, 1984). This is also the time to
emphasize public education efforts.
-Workshops organized on the state or regional level by organizations such as the Massachusetts
Coastal Zone Management Office or the Cape Cod Commission may be of assistance for
troubleshooting and educational potential.
Conclusion
A review of the literature and the case study have identified potential effects of sea level nse.
Management options have been presented to encourage coastal communities to begin thinking about
how to address this issue now as well as in the future. Finally, guidelines for an assessment of sea
level rise are presented and may be useful to local officials.
37
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ACKNOWLEDGEMENTS
I would like to thank Marcy Berbrick for the crash course in Arc/Info, her advice, and technical
expertise. I am grateful to JoAnne Sulak and Kyla Bennett for their suggestions and for read ng
preliminary drafts and to Rosemary Monahan for coming up with the project. Andrew Young
mtroduced me to the Town of Chatham and provided some valuable background information
Robert Duncanson of the Chatham Water Quality Laboratory furnished tte mapping data and
mTmSfs^nwK6 °f fe*tiom: SuPP°rt for this study was provided by an EPA Fellowship
Pro ram National Network for Environmental Management Studies (NNEMS)
NOTES
1. Current wetland regulations under section 404 of the Clean Water Act (CWA) provide adequate
protection for coastal wetlands, but not for freshwater wetlands. The is a yearly loss of about 300 000
acres of freshwater wetlands, and many of these are "permitted" losses. However developers and the
wlvh w^aVu ^T^ ?£ BUSh Administration to change the method used to delineate wetlands,
which will result m a loss of protection for millions of acres of wetlands. The proposed method wil
impart salt marshes and result in some loss. In addition, inland wetlands that are connected to the
coastal system may suffer further impacts and overload the protective functions of salt marshes.
2. Raising land such as barrier islands, has also been suggested as a cost effective response to sea level
nse This will be considered to be a form of entrenchment because of the uncertainty of the capability
of this mechanism to preserve coastal habitat. m*u«my
3. A change in tidal range is analogous to an increase in sea level, but it is not identical. For example
sea level nse will elevate both the low and high tides, whereas a change in tidal range will elevate the
high tide, but lower the low tide (see Figure 7).
4. These maps do not appear as they were plotted due to size and color limitations of the reproduction
For further information concerning the CIS section contact: JoAnne Sulak, U.S. Environmental
Protection Agency, Region I, Marine and Estuarine Protection Section, John F. Kennedy Federal
Building, Boston, MA 02115). y
5. This is similar to the Maryland Critical Areas Act which establishes a wetland buffer and limits
development densities adjacent to the buffer (Klarin and Hershman, 1990).
38
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Appendix A. List of typical New England salt marsh plants.
(From U.S. EPA, 1981)
COASTAL WETLANDS OF REGION I
Just as the permanently saturated areas of an inland wetland may be identified
by the vegetative cover, so too, may the tidal zones of a coastal marsh be deter-
mined by the changes in vegetation as one progresses from one zone to the next.
For the purpose of administration of existing laws and regulations, the identifica-
tion of the following three zones should be sufficient: (1) The inter-tidal zone;
(2) the high marsh; and (3) the transition zone between high marsh and upland.
A wetland boundary is often difficult to delineate in the transition zone, but one
should be able to tell complete wetland from complete upland using this manual.
The following listing of plant species separated by zonal location are typical of
New England coastal marshes.
1. The Inter-Tidal Zone. This is the lowest part of the marsh, subject to
twice daily flooding by the ebb and flow of normal tides.
ALGAE (SEAWEED)
Ascophyllum nodosum Knotted Wrack
Enteromorpha intestinalis Green Seaweed
Fucus vesiculosis Rockweed
Rhodymenia palmata Dulse
Ulva lactuca Sea Lettuce
VASCULAR PLANTS
Spartina alterniflora Salt Marsh Cordgrass
2. The High Marsh. This is the area subject to flooding only by the higher
spring tides. At some seasons there may be intervals of no tidal flooding.
GRASSES AND RUSHES
Distichlis spicata Spike Grass
Juncusgerardii Black Grass
Spartina patens Salt Meadow Cordgrass
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Appendix A.
SHRUBS AND HERBS
Atrip/ex sp. Qrach
ARlterhtenu"°'iusf ,. Marsh Aster
Bacchant hahmifblia Groundsel Tree
Iva frutescens Marsh Elder
Limomum carohmanum Sea Lavender
Plamago ohganthos Seaside p|antajn
"ea PurP^cens Sa,t Marsh F|eab
Sohdago sempev,rens Seaside Goldenrod
Suaedaspp. SeaBlite
°f
Salcorma europaea Samphjre
Sahcorma v.rg.mca Perennja|
int 3t'h .The Jruansition Zone- Flo°dmg occurs only by extreme storm tides Grades
into the brackish area, influenced by freshwater mixing.
GRASS-LIKE SPECIES
Agrostisalbavar. palustris Redtop Grass
Seaside Wild Rye
Switch Grass
mn*««tnli* Reed GraS
Rushes *
SHRUBS AND HERBS
Amelanchierlaevis Shadbush
Myncapensytonica Bayberrv
Oenotherabiennis Evening Primrose
as=r- ssr-r-
Sa|twort
Sand s
cattail
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Appendix B. Wetlands Protection Bylaws.
(Town of Chatham, Conservation Commission, 1988)
2.05 Coastal Banks
(1) Preamble
r ,' i hanks are likely to be important to storm damage prevention
*1 -» *-*>•* n A TM*6vCTitlOn ttiiv* **ww»« » , g „_.__ c t.*\v*m
. .—„,
a buffer. or it m,y serve only on, role.
Coast,, Ban,, composed of
s y
The supply of sediment ,. «™°«cdesfsr°™ "h, continued existence
storm damage and
Stal weuanus ianw"-»— --
flooding.
isss, . ,,
ways .
(2) Definition
Zones A, AO, AH, A1-A30, A99, V. and
,., No ne» bu,khe,d. "",-nt,.,^. groin or other^oasu,
ments are met:
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Appendix B.
U) a coastal engineering structure or modification th»v»
to shall be designed and constructed so as to m^-
mize using best available measures, adverse effects
on adjacent or nearby coastal beaches due to changes
in wave action, and «-nanges
(ii) the applicant demonstrates that no method of protect-
ing the building other than the proposed coastal
engineering structure is feasible.
(iii) protective planting designed to reduce erosion may
be permitted. '
(iv) the applicant provides sufficient evidence that the
building was constructed pursuant to a Notice of
intent filed before August 10, 1978.
(b) Any project on a coastal bank or within 100 feet of the top
of a coastal bank, other than a structure permitted und^r
Section 2.05(3)(a), shall not have an adverse Sfect due to
£:; rri0: °r, f. ™:em_en'_ * ***™< *™ *. C0astai
C°a U eaChS °r land SubJect to tidal action or
of a
(O The Permit and the Certificate of Compliance for any project
100 feet of the top of a coastal bank permitted bv
tnTch".^'05 w ^e *etlands Regulations, promulgated under
the Chatham Wetlands Protection By-law requires that no
coastal engineering structure, such as a bulkhead, revetment
groin, or seawall shall be permitted on or within 100 feet of
a coastal bank at any time in the future to protect the
project allowed by this permit." P^eci tne
2.06 Salt Marshes
(1) Preamble
fisherTe"1165 *" important to the Protection of wildlife, marine
-
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Appendix B.
Land within 100 feet of a salt marsh is likely to be sigmftcant to
Se protecTion and maintenance of salt marshes, and therefore to
the protection of the wetland values these areas contain.
The following characteristics of salt marshes are critical to one or
more of the wetland values above:
(a) the growth, composition and distribution of salt marsh
vegetation;
(b) the flow and level of tidal and fresh water; and
(c) the presence and depth of peat.
(2) Definitions
r.-sfw w««~?v3?
characterized by a plant community consjsting of. but not
?nS?Id to 40% or more of any of the following specjes: Salt
ri«^££^£S>?1=
„< ium~..
"mm^nisV; SahrnarTh BulVush (s'cirpu. robustus); or Cattails
(Typha spp.).
,„> -Spring TM.« » * "
s:
moon are in phase (new and full moons).
r, feet
with an Sh.V applicable requirements of these regulates.
another.
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