United States Environmental
Protection Agency
Office of Air and
Radiation
EPA 430R07004
February 2008
« v\ Background Documents
ij Supporting Climate Change
Science Program Synthesis
and Assessment Product 4.1:
Coastal Elevations and
Sensitivity to Sea Level Rise
J.G. Titus
Environmental Protection Agency
and
E.M. Strange
Stratus Consulting Inc., editors
These technical documents were prepared and approved for publication by the U.S. EPA Office of Air and Radiation in
accordance with EPA peer review policies. The draft document underwent peer review by external subject-matter
experts. The comments of all reviewers were carefully considered and incorporated, wherever possible, throughout the
revised technical documents. The information in this document was developed and presented in a manner consistent
with EPA's Guidelines for Ensuring and Maximizing the Quality, Objectivity, Utility and Integrity of Information
Disseminated by the Environmental Protection Agency. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use. Please send comments to James G. Titus, U.S. Environmental
Protection Agency, Washington, D.C. 20460.
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This document should be cited as:
Background Documents Supporting Climate Change Science Program Synthesis and Assessment
Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise, J.G. Titus and E.M. Strange
(eds.), 2008. EPA 430R07004. U.S. EPA, Washington, DC.
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Preface
Sea level has risen approximately 30 cm (1
foot) along most of the U.S. Atlantic and Gulf
coasts in the last century.1 In the next century,
however, rising atmospheric and ocean
temperatures are likely to expand ocean water
and melt glaciers, and thereby accelerate the
rise in sea level. By the end of the 21st century,
global average sea level is likely to be rising
1.5-9.7 mm/yr even if polar ice sheets do not
begin to disintegrate, according to the
Intergovernmental Panel on Climate Change.2
Additional contributions from the Greenland
and Antarctic ice sheets could be negligible or
add as much as 4 mm/yr.3 Because of regional
subsidence, sea level has risen, and almost
certainly will continue to rise, 1-2 mm/yr more
rapidly than the global average along the mid-
Atlantic Coast.4 Thus, by 2100, sea level could
be rising 3-16 mm/yr.5 Over the next century
:See, e.g., Zervas, C.E., 2001, Sea Level Variations of
the United States 1854-1999, NOAA Technical Report
NOS CO-OPS 36, Silver Spring, MD: National Oceanic
and Atmospheric Administration.
2IPCC at Table 10.7; Meehl, G.A., T.F. Stacker, W.D.
Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A.
Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper,
I.G. Watterson, A.J. Weaver and Z.-C. Zhao, 2007,
Global Climate Projections. In: Climate Change 2007:
The Physical Science Basis. Contribution of Working
Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change, Solomon,
S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B.
Averyt, M. Tignor and H.L. Miller (eds.). United
Kingdom and New York: Cambridge University Press,
Cambridge,
3Ibid.
4See, e.g., Titus, J.G. and V. Narayanan, 1996, The
Probability of Sea Level Rise, Washington, DC: U.S.
Enviromnental Protection Agency, at chapter 9
(discussing methods for projecting relative sea level rise
when given projections of global sea level rise).
5The global rate would be 1.5-13.6 mm/yr; IPCC at
Table 10.7 (adding "sea level rise" to "scaled up ice
charge"). Ibid.
sea level is expected to rise 30 to 90 cm (1 to 3
feet) along the mid-Atlantic coast.6
Rising sea level inundates low-lying lands,
erodes shorelines, exacerbates flooding, and
increases the salinity of estuaries and aquifers.
The ramifications can be broadly divided into
two categories: the human impact and the
environmental impact. The human impacts
include flood damages, land and structures lost
to the sea, costs of protecting land and
structures from the sea, the indirect economic
and human toll from the migration necessitated
by the entire loss of a community, and the costs
of shifting to alternative water supplies when
the original supply becomes saline.
This collection of papers focuses on some of
the environmental impacts of sea level rise on
the mid-Atlantic Coast of the United States. All
but two of these papers were prepared to
support a forthcoming report by the United
States Climate Change Science Program
entitled Coastal Elevations and Sensitivity to
Sea Level Rise.
Figures a-d provide an overview of the primary
environmental impact examined by this report.
Tidal wetlands are found where the elevation of
the land is between high and low tides, with
tidal marshes generally above mean sea level
and tidal flats below mean sea level, (a) When
sea level was rising rapidly, tidal wetlands
would tend to be a narrow fringe along the
shore, determined by the slope of the land. But
wetlands have been able to keep pace with the
relatively slow rate of sea level rise during the
last several thousand years. As sea level rose,
new wetlands would form inland; but the
seaward boundary of tidal wetlands did not
retreat to the same extent, and the area of tidal
6The global rise would be 19-77 cm. Ibid.
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[ ii BACKGROUND DOCUMENTS SUPPORTING CCSP SAP 4.1 ]
wetlands increased, (b) Today, the area of tidal
wetlands—i.e., the land between the high and
low tide shorelines—is much greater than the
amount of dry land within a similar elevation
range above the high tide shoreline. But there is
a limit to the rate of sea level rise with which
tidal wetlands can keep pace, (c) And if the sea
rises more rapidly, most of the existing tidal
wetlands will be lost, and the total area of tidal
wetlands will decline to the narrow fringe
determined by the slope, (d) Finally, in places
where developed lands along the shore are
protected from tidal inundation, new wetlands
may not form inland and almost all tidal
wetlands may be lost. Because the tidal
wetlands support fish and wildlife, a loss of
tidal wetlands could cause populations of birds
and fish to decline or relocate.
Examining the magnitude of this environmental
impact requires us to address several questions,
which are enumerated in the prospectus for
Coastal Elevations and Sensitivity to Sea Level
Rise:
• How much dry land is immediately above
the tides and hence potentially available for
the creation of new wetlands (wetland
migration) as sea level rises?
• To what extent can existing tidal
wetlands—especially the vegetated
wetlands—keep pace with rising sea level?
• Which species depend on the tidal wetlands
that are potentially at risk if sea level rises?
In Section 1.1, Titus and Wang evaluate the
first question. They collected the best available
topographic information as well as data on tides
and wetlands. Based on standard interpolation
methods, they create maps of lands depicting
elevations relative to spring high water, that is,
the average elevation of the high tides during
full and new moons. Because tidal wetlands
generally extend up to approximately spring
high water, those maps provide elevations
relative to the upper boundary of tidal
wetlands. Finally, they quantify the area of
lands close to sea level. In Section 1.2, Jones
and Wang provide additional details on the
Titus and Wang approach to quantifying the
area of land close to sea level by interpolation.
This paper also explains the authors' approach
5,000 Years Ago
Sea Level
Current
v Sea Level
Past
Sea Level
Future
Substantial Wetland Loss Where
House is Moved or Upland is Vacant
Complete Wetland Loss Where House is Protected
with Bulkhead in Response to Rise in Sea Level
Future
Sea Level
Current
Sea Level
LEGEND
Sedimentation and.
Peat Formation
Marsh
Future
_5_ Sea Level-
— Current
Sea Levek
Fish and Midlife that rely on the marsh
Available at
http://www.climatescience.gov/Library/sap/
sap4-l/sap4-1 prospect us-final.litni
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[ PREFACE iii ]
to extending that type of analysis to include
forthcoming data sets on shore protection and
the vertical accretion of wetlands. Finally, Titus
(in Section 1.3.1) and Cacela (in Section 1.3.2)
estimate uncertainty ranges for the results
developed in the previous two sections.
Chapter 2 has two papers that examine the
ability of wetlands to keep pace with rising sea
level through mechanisms collectively known
as "wetland accretion." Section 2.1, by Reed et
al., is the heart of the analysis: a panel
assessment of the potential for wetland
accretion in the mid-Atlantic from the south
shore of Long Island to Virginia Beach. (They
excluded North Carolina because the wetland
accretionary processes are very different there.)
This paper describes wetland accretionary
processes and how they vary across different
geomorphic settings. It also contains the
panel's assessment of the potential for future
wetland accretion. In Section 2.2, Titus, Jones,
and Streeter generate GIS data and a set of
maps to succinctly summarize the results of the
Reed et al. analysis—and document a data set
available for other researchers interested in
modeling changes in mid-Atlantic wetlands.
(The complete set of maps appears in Section
2.1 instead of 2.2 to facilitate the discussion of
the various mid-Atlantic subregions.)
This report does not quantitatively integrate the
results from the separate studies. However, an
informal examination of the maps produced in
these studies shows that accelerated sea level
rise is likely to cause a loss of intertidal habitat,
with higher rates of sea level rise causing a
correspondingly greater loss of habitat. What
are the consequences?
Ideally, we would develop an ecological model
of the impacts of habitat loss throughout the
mid-Atlantic as sea level rises. Given time and
resource constraints, we had to limit our
modeling to a single county and provide more
qualitative descriptions for the rest of the
region. Chapter 3 presents 20 papers that
examine the species that depend on the
vulnerable habitats. In Section 3.1, Jones and
Bosch present an overview of the habitats that
could be altered or lost as a result of sea level
rise and the animal species found in these
habitats, with emphasis on tidal marshes,
estuarine beaches, tidal flats, and submerged
aquatic vegetation. Eighteen brief literature
reviews follow, each discussing the coastal
ecosystems of a multicounty coastal region.
These papers focus on the animals that depend
on the vulnerable habitats for food, shelter,
spawning, or nursery areas. Although it was not
possible to discuss every bay, river, or tidal
creek, we examine a representative sample.
Five locator maps8 show the specific areas that
these papers discuss. Finally, Section 3.20 is a
modeling study, which quantifies the impact of
sea level rise and six scenarios of shore
protection on the fish and bird species that
inhabit Barnegat Bay and the smaller estuaries
adjacent to Long Beach Island, New Jersey.
This pilot study quantitatively integrates the
three questions addressed by this report.
Chapters 1 and 2 are mapping assessments that
rely mostly on published data and peer-
reviewed scientific literature. Chapter 3,
however, relies on a more diverse group of
sources—including web sites, and emails and
oral statements from experts. These types of
sources are necessary because, in most cases,
there is no peer-reviewed journal article that
addresses the presence of a particular species at
a particular location. Nevertheless, as long as
an author reviews the reliability of a source,
these more informal sources can be just as
useful as a published scientific article. For
example, an individual making a general
statement about environmental vulnerability
may not be as reliable as a peer-reviewed
article doing the same thing; but a refuge
manager stating species of birds that she has
personally seen on her refuge would generally
be at least as reliable as a journal article that
mentioned that particular refuge in passing. In
every case where these papers rely on a source
that is not a peer-reviewed report, the footnote
documenting the source includes enough
information for a reader to understand the
8Maps 3-1, 3-2, 3-3, 3-7, and 3-8.
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[ iv BACKGROUND DOCUMENTS SUPPORTING CCSP SAP 4.1 ]
author's basis for assuming that the source is
reliable for the fact cited.
Throughout Chesapeake Bay, tidal and
intertidal lands are threatened by sea level rise.
Although coastal wetlands may migrate inland
in some locations, Chesapeake Bay is likely to
experience a significant loss of tidal wetland
habitat with even a small increase in the rate at
which sea level rises—and if sea level rises
more than 10 mm/yr—most saline and brackish
wetlands are vulnerable. One would expect
adverse effects on the species that use these
habitats for critical life functions such as
reproduction and feeding, but we know too
little to determine cause and effect relationships
or to quantify the impacts. In intertidal areas,
deeper water will reduce light penetration,
which can inhibit the growth and survival of
submerged aquatic vegetation; whether these
areas can transgress inland onto current marsh
areas that become inundated is highly uncertain
and depends on a variety of physical factors.
Although beds of submerged aquatic vegetation
play a critical role as nursery and food source
for many fish and other aquatic species, we do
not know the extent of consequences of the loss
of submerged vegetation for these species—
similarly, the impacts of substantial marsh loss
on the species that feed on the fish that directly
rely on the marsh are not quantified. The
impact on birds is also unclear: Some species
may be able to move inland to nest and find
food—but perhaps only if nearshore farms,
forests, and nontidal wetlands are not
consumed by coastal development. Changing
migration patterns with a warmer climate and
shifts in estuarine species composition with
warmer water temperatures are further
confounding factors. Nevertheless, some
species are clearly vulnerable, such as the
horseshoe crab, which relies on estuarine
beaches to reproduce—and the many migratory
bird species that depend on horseshoe crab eggs
to refuel during their long-distance migrations.
Our inability to forecast how complex animal
communities respond to habitat loss as sea level
rises need not obscure the importance of the
few things that we do know. For several
decades, the importance of tidal habitats has
prompted governments and private
conservancies to preserve coastal wetlands and
shallow water habitats. Rising sea level
threatens these habitats, and an accelerated rise
is likely to eliminate much of it. This report
identifies many animal species that will be
forced to adapt to the impacts of rising sea
level. How they might adapt and what
managers might do to increase the likelihood of
successful adaptations are outside the scope of
this report. We hope that this collection of
papers helps motivate the research needed to
answer those questions.
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Summary of the Review Process
In 2006, EPA initiated the review of a series of papers that were written as background for the
U.S. Climate Change Science Program (CCSP) Synthesis and Assessment Product 4.1 Coastal
Elevations and Sensitivity to Sea-Level Rise. These documents were linked to questions in the
SAP4.1 Prospectus. The reviews were intended to serve as "Level One" peer reviews—short,
brief reviews to help the authors ensure that each background paper contained reasonable
assumptions, estimates, and conclusions given the available data.
Potential reviewers were identified on the basis of their areas of expertise, including knowledge
of the specific coastal areas studied. To accommodate the range of topics explored in the papers
(e.g., wetland accretion, GIS mapping, and coastal zone biology), reviewers were sought from a
variety of backgrounds. Candidate reviewers included scientists, engineers, and others involved
with mid-Atlantic coastal research, management, and policy in federal, state, and local agencies,
nonprofit organizations, and the private sector.
For each document, reviewers were given the paper itself, a review charge, and other background
documents as needed to support their review. Many of the papers were relatively brief, and
reviewers were often asked to review more than one paper. Comments sent by reviewers were
compiled in a comment spreadsheet for use by EPA, and each author was sent verbatim
comments on the paper(s) that they wrote. The comments of all reviewers were carefully
considered and incorporated, wherever possible, throughout the revised technical documents.
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Contents
CHAPTER 1. COASTAL ELEVATIONS IN THE MID-ATLANTIC
1.1 Maps of Lands Close to Sea Level along the Middle Atlantic Coast of the
United States: An Elevation Data Set to Use While Waiting for LIDAR
J. G. Titus and J. Wang 1
1.2 Interpolating Elevations: Proposed Method for Conducting Overlay Analysis of
GIS Data on Coastal Elevations, Shore Protection, and Wetland Accretion
R. Jones and J. Wang 45
Appendix A. Area of Land Close to Sea Level, by State 56
1.3 Uncertainty Ranges Associated with EPA's Estimates of the Area of Land
Close to Sea Level
J. G. Titus and D. Cacela 68
1.3.1. Approach
J. G. Titus 69
1.3.2. Implementing the Approach using Geographically Specific
Error Functions Approach
D. Cacela 83
1.3.3. Results
J. G. Titus 101
Appendix A. Low and High Estimates of the Area of Land
Close to Sea Level, by State 103
Appendix B. Low and High Estimates for the Area of Dry
and Wet Land Close to Sea Level, by Subregion 119
Appendix C. Low and High Estimates of the Area of Land
Close to Sea Level, by Region: Mid-Atlantic 130
CHAPTER 2. SITE-SPECIFIC SCENARIOS FOR WETLANDS ACCRETION IN THE
MID-ATLANTIC
2.1 Site-Specific Scenarios for Wetlands Accretion as Sea Level Rises in the Mid-
Atlantic Region
D. J. Reed, D. A. Bishara, D. R. Cahoon, J. Donnelly, M. Kearney, A. S. Kolker,
L. L. Leonard, R. A. Orson, J. C. Stevenson 134
2.2. Maps that Depict Site-Specific Scenarios for Wetland Accretion as Sea Level
Rises along the Mid-Atlantic Coast
J. G. Titus, R. Jones, R. Streeter 175
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[ CONTENTS vii ]
CHAPTER 3. MID-ATLANTIC COASTAL HABITATS AND ENVIRONMENTAL
IMPLICATIONS OF SEA LEVEL RISE
3.1 Overview
A. Shellenbarger Jones 188
3.2 North Shore, Long Island Sound and Peconic Estuary
E. M. Strange 211
3.3 Long Island's South Shore Barrier Island/Lagoon System
E. M. Strange 218
3.4 New York City, the Lower Hudson River, and Jamaica Bay
E. M. Strange 222
3.5 Raritan Bay and the Hackensack Meadowland, New Jersey
E. M. Strange 230
3.6 New Jersey's Coastal Bays
E. M. Strange 234
3.7 Delaware Bay
D. Kreeger and J. G. Titus 242
3.8. Maryland and Delaware Coastal Bays
E. M. Strange 252
3.9 The Atlantic Side of the Virginia Eastern Shore
E. M. Strange 259
3.10 Chesapeake Bay: Local Area Coastal Habitat and Environmental Implications
of Sea Level Rise: Anticipated Effects by Multicounty Region
A. Shellenbarger Jones 263
3.11 The Chesapeake Bay Shoreline near Hampton Roads
A. Shellenbarger Jones and C. Bosch 266
3.12 The Chesapeake Bay Shoreline of Middle Peninsula
A. Shellenbarger Jones and C. Bosch 270
3.13 The Chesapeake Bay Shoreline of Northern Neck
A. Shellenbarger Jones and C. Bosch 274
3.14 Lower Potomac
E. M. Strange and A. Shellenbarger Jones 277
3.15 Upper Potomac
E. M. Strange and A. Shellenbarger Jones 282
3.16 Western Shore Chesapeake Bay Shoreline
A. Shellenbarger Jones and C. Bosch 286
3.17 Upper Chesapeake Bay Shoreline
A. Shellenbarger Jones and C. Bosch 292
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[ viii BACKGROUND DOCUMENTS SUPPORTING CCSP SAP 4.1 ]
3.18 The Chesapeake Bay Shoreline of the Central Eastern Shore
A. Shellenbarger Jones 296
3.19 Virginia Eastern Shore of Chesapeake Bay
E. M. Strange 300
3.20 Sea Level Rise Modeling
R. Jones and E. M. Strange 303
Appendix: GIS Maps of Modeled Habitat Changes 324
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CHAPTER 1. COASTAL ELEVATIONS IN THE
MID-ATLANTIC
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1.1. Maps of Lands Close to Sea Level along the
Middle Atlantic Coast of the United States: An
Elevation Data Set to Use While Waiting for LIDAR
James G. Titus
Environmental Protection Agency
and
Jue Wang
Pyramid Systems, Incorporated
This section should be cited as:
Titus J.G., and J. Wang. 2008. Maps of Lands Close to Sea Level along the Middle Atlantic
Coast of the United States: An Elevation Data Set to Use While Waiting for LIDAR. Section
1.1 in: Background Documents Supporting Climate Change Science Program Synthesis and
Assessment Product 4.1, J.G. Titus and E.M. Strange (eds.). EPA 430R07004. U.S. EPA,
Washington, DC.
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Abstract
This report provides a coastal elevation data set for
the mid-Atlantic for purposes of assessing the
potential for coastal lands to be inundated by rising
sea level. Depending on what we were able to
obtain, our elevation estimates are based on
LIDAR, federal or state spot elevation data, local
government topographic information, and USGS
1:24,000 scale topographic maps. We use wetlands
and tide data to define a supplemental elevation
contour at the upper boundary of tidal wetlands.
Unlike most coastal mapping studies, we express
elevations relative to spring high water rather than
a fixed reference plane, so that the data set
measures the magnitude of sea level rise required
to tidally flood lands that are currently above the
tides. Our study area includes the seven coastal
states from New York to North Carolina, plus the
District of Columbia.
We assess the accuracy of our approach by
comparing our elevation estimates with LIDAR
from Maryland and North Carolina. The root mean
square error at individual locations appears to be
approximately one-half the contour interval of the
input data. We also compared the cumulative
amount of land below particular elevations
according to our estimates and the LIDAR; in that
context, our error was generally less than one-
quarter the contour interval of the input data.
We estimate that the dry land in the region has a
relatively uniform elevation distribution within
the first 5 meters above the tides, with about
1,200-1,500 km2 for each 50 cm of elevation.
With the exception of North Carolina, the area of
nontidal wetlands declines gradually from about
250 km2 within 50 cm above the tides to about
150 km between 450 and 500 cm above the
tides. North Carolina has approximately 3,000
km of nontidal wetlands within 1 meter above
spring high water; above that elevation, the
amount of nontidal wetlands declines gradually
as with the other states. North Carolina accounts
for more than two-thirds of the dry land and
nontidal wetlands within 1 meter above the tides.
We also compare our results to previous studies
estimating the region's vulnerability to sea level
rise. Our results are broadly consistent with an
EPA mapping study published in 2001, which
estimated the total amount of land below the 1.5-
and 3.5-m contours (relative to the National
Geodetic Vertical Datum of 1929). This study
appears to be a significant downward revision,
however, of EPA's 1989 Report to Congress. Our
estimates of the dry land vulnerable to a 50- or
100-cm global rise in sea level are less than one-
half the estimates of the Report to Congress. The
regional estimates of that nationwide study,
however, were based on a small sample.
Therefore, one should not extrapolate our mid-
Atlantic result to conclude that EPA's previously
reported nationwide estimate overstates reality
by a similar magnitude.
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1.1.1 Introduction
During the last two decades, the issue of rising sea
level has spread from being primarily a concern of
coastal geologists (e.g., Pilkey et al., 1982) and
those who measure the tides (e.g. Hicks et al.,
1983; Zervas, 2001) to an issue that concerns
planners, policymakers, and the public at large
(e.g., KRISTOFF, 2005; Dean 2006). One reason is
that the sea is rising 3 mm/yr or more along many
low-lying areas (Figure 1.1.1), enough for some
areas that were developed 50-100 years ago to be
flooded by high tides during new or full moons
(Figure 1.1.2). Another reason is that increasing
concentrations of carbon dioxide and other
greenhouse gases appear to be contributing to a
global warming responsible for at least part of the
current rate of sea level rise (e.g., U.S. EPA, 1996;
IPCC, 2007). Most scientists expect greenhouse
gases to accelerate the rise in sea level (IPCC,
2001a), and some have suggested that it may
already be doing so (Church and White, 2006).
Rising sea level inundates low-lying lands, erodes
wetlands and beaches, exacerbates flooding, and
increases the salinity of estuaries and aquifers
(e.g., IPCC, 2001b). Studies over the last two
decades have identified numerous decisions that
may be sensitive to sea level rise (e.g., NRC,
1987; Williams et al., 1995; Titus and
Narayanan1, 1996). During the Administration
of President George W. Bush, the U.S. Climate
Change Research Program (2003) has actively
promoted decision support research to assist with
adaptation to consequences of climate changes
such as rising sea level. Studies sponsored by the
U.S. EPA have suggested that local governments
may be making the most important decisions
regarding the eventual impact of rising sea level on
the United States. Local governments create the
land use plans and issue the construction permits
that determine whether the areas at risk will be
developed enough to require shore protection as
the sea rises or will remain vacant enough for
wetlands to migrate inland (Titus, 1990, 1998).
Over the last several years, EPA staff and
contractors have met with local governments
concerning possible responses to sea level rise
(Titus, 2005). When we have asked what
information might help them to better prepare, the
most common answer has been better elevation
maps. When senior government officials or
newspaper reporters have asked us about
vulnerability to sea level rise, the most common
request has been for a map showing the lands that
might be flooded. Yet maps depicting lands close
to sea level using the best available data are
unavailable for most areas.2
1 Section 3.1 of that paper is an overview of decisions that
depend on the probability of the sea rising a particular
magnitude.
But see Weiss and Overpeck (2006), which provides a
map server using the USGS national elevation data series.
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[ 4 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
V
R*"8. «~ <
n
Rate of Sea Level Rise
• < -2.00 mm/yr
•-2.00 to 0.00
0.01 to 1.25
• 1.26 to 2,50
2.51 to 3.75
• 3.76 to 6.00
• > 6.00 mm/yr
Figure 1.1.1. Relative sea level rise at locations with at least 50 years of tide station data. (Data Source:
PERMANENT SERVICE FOR MEAN SEA LEVEL, 2003).
For many years, the EPA sea level rise project
avoided this obvious endeavor because we
expected LIDAR3 data (hereafter LIDAR) to be
available soon, which would make moot the entire
exercise. But the LIDAR was slow in coming.
Finally, we decided that a better way to manage
the risk of creating unnecessary information would
be to create an elevation data set anyway; if the
LIDAR does not arrive, then we will have
provided a useful elevation data set; if LIDAR
does become available, then the public will have
even better maps.
This report presents the methods we used to create
maps and a dataset for analyzing the impacts of sea
level rise. We provide elevation data for the
coastal zone from New York to North Carolina.
The purpose of this data set is to identify and
quantify the land that could potentially be
3Light Detection And Ranging (LIDAR) is similar to
RADAR, except it relies on light instead of radio waves.
The LIDAR instrument transmits light out to a target; the
time it takes for the light to return is used to determine
distance. Land elevations are estimated with low-flying
aircrafts with LIDAR instruments.
inundated as sea level rises, so that EPA and other
researchers can (1) evaluate the land potentially
available for wetland migration, (2) identify the
areas that might require shore protection and
quantify shore protection costs, and (3) estimate
the population and assets within the area
potentially at risk to sea level rise. Although this
report has only a few example maps, map
templates accompany the data set that we are
distributing so that those with GIS software can
easily create elevation maps to suit their needs.
Although our focus is on coastal elevations rather
than scenarios of inundation, the elevation of our
study area was broadly guided by the available
literature estimating future sea level rise. IPCC
(2007) estimated that global sea level is likely to
rise 18-59 cm over the next century, but also
indicated that the sea could rise 9-17 cm more if
polar ice sheets begin to disintegrate.4 Along the
mid-Atlantic coast, sea level rise is generally
expected to be 10-20 cm more than the global
average rise.5 Thus, as you examine our maps, you
4IPCC (2007) at table 10.7.
'See, e.g., Titus and Narayanan (1996) at Chapter 9.
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[ SECTION 1.1 5 ]
Photo 1.1.1. Tidal flooding at Ship Bottom, New Jersey (Labor Day 2002).
might reasonably assume that sea level is likely to
rise 30-100 cm in the next century. But IPCC also
estimates that by the 21st century, global sea level
could be rising 4-14 mm/yr,0 which would imply a
rise of 5-16 mm/yr along the mid-Atlantic coast.
Thus a rise of several meters over the next few
centuries is possible. Our maps all provide
elevations up to either 3 or 6 meters above the ebb
and flow of the tides. Our primary motivation for
extending the maps this far inland was to convey at
least a rough sense of the topography of the coastal
zone, and doing so requires one to look above the
elevation that is most immediately at risk.
Nevertheless, sea level could rise 3-6 meters over
the next few centuries.
The next section (1.1.2) discusses our general
approach, which was to obtain the best available
elevation data from the U.S. Geological Survey
(USGS) and other federal, state, and local
government agencies; create an extra contour at
the inland boundary of tidal wetlands; and express
elevations relative to the ebb and flow of the tides.
After that, we describe (1.1.3) how we applied that
approach to the data we were able to obtain, and
explain (1.1.4) our accuracy assessment. The final
section (1.1.5) presents the maps, estimates the
area of land close to sea level, and compares our
results to previous assessments.
Before proceeding with the analysis, a word of
caution on the use of units in this report. We
generally use metric units, with English units in
parentheses where we cite a report whose results
originally used English units. However, when
discussing contour intervals of specific maps used
in the analysis, we refer to the units that the maps
actually used, which are often English units. We
believe that it is more accurate to say (for
example) that the USGS maps of Maryland
include 1-m and 5-ft contour intervals, than to say
that they include 1-m and 1.524-m contours.
Although most writers would normally prefer to
avoid mixing units of measurement, the underlying
reality is that there is currently a relatively
confusing patchwork of available elevation data
sets, and different units of measurement is part of
that reality.
bSee IPCC (2007) at Table 10.7 (high estimate includes
lines called "sea level rise" and "scaled-up ice sheet
discharge").
-------
1.1.2 General Approach
This study is based on the relationship between the
tidal elevations, tidal wetlands, and the reference
elevations used by available elevation data. Figure
1.1.2 illustrates the relationship between these
three factors along a typical shore profile, using
the tidal elevations for Hampton Roads (VA). In
this particular case, mean sea level is 17.2 cm
above NGVD29, which is the reference elevation
used by the USGS topographic maps. Spring high
water is 43 cm above mean sea level, and thus 60
cm above NGVD29. Thus, the 5-ft contour is only
90 cm (3 feet) above spring high water. Because
tidal marshes are found between mean sea level
and spring high water, the 5-ft contour is also 90
cm (3 feet) above the tidal wetlands.
Our general approach has five main steps:
1. Obtain the best elevation data from usual
sources of topographic map data, such as the
USGS, as well as state and local governments
and other federal agencies.
2. Use wetlands data to determine the location of
the upper boundary of tidal wetlands, which
we treat as the land flooded by spring high tide
7 Older maps generally measure elevations relative to the
National Geodetic Vertical Datum of 1929, which was
originally meant to be a fixed reference plane. NGVD was
set equal to the sea level of 1929 at specific reference
stations along the U.S. coast. The reference "plane"
(actually a spheroid) in all other locations was based on
leveling techniques. As a result, even in 1929, NGVD was
not sea level in areas where average water levels diverge
from the ideal "plane" because of winds, freshwater
inflow, and other factors. Since 1929, rising sea level and
subsidence have caused sea level and the NGVD to
diverge 10-20 cm in most areas. Recognizing the
problems with the deteriorating benchmarks, the USGS
and the National Geodetic Survey converted to the North
American Vertical Datum (NAVD) of 1988. The reference
plane associated with this benchmark is based on a single
fixed site. New data generally are relative to NAVD-1988.
See, e.g., NATIONAL GEODETIC SURVEY et al.
(1998).
8 Spring tides refer to the extreme tides that occur during
new and full moons, when the tidal forces of the moon and
sun are aligned. Spring high water is the average height of
high water during spring tides. See, e.g., NOS (2000).
and, hence, the horizontal position of our
wetland supplemental contour.
3. Use tidal data to estimate the elevation
(relative to NGVD29), of spring high water,
which we use as the vertical position of our
wetland supplemental contour.
4. Interpolate elevations relative to the vertical
datum for all land above spring high water
using elevations obtained from the previous
three steps.
5. Use the information from step 3 to calculate
elevations relative to spring high water.
Figures 1.1.3 and 1.1.4 illustrate the results of
these steps for a portion of Long Beach Island
(New Jersey) and the adjacent mainland, including
the portion of Ship Bottom (Figure 1.1.2) that is
often flooded by spring tides. The USGS maps
have a 10-ft contour interval (Figure 1.1.3a), but
the U.S.
Army Corps of Engineers provided spot elevation
data for the islands and some of the mainland
(Figure 1.1.3b). For the mainland areas without
spot elevation data, we created a supplemental
contour representing spring high water and the
upper edge of tidal wetlands. The wetlands data
define the horizontal position of this contour
(Figure 1.1.3a). We used tidal data to define the
vertical position of the contour relative to
NGVD29 (Figure 1.1.4). With that supplemental
contour defined, we interpolated elevations in
between the contours (Figure 1.1.3c), which yields
elevations relative to NGVD29. Finally we
subtract the tidal elevations from Figure 1.1.4 to
express land elevations relative to spring high
water (Figure 1.1.3d).
Difference from Other Elevation Mapping
Assessments
Our approach differs from other elevation mapping
studies in two fundamental ways. First, our final
product represents elevations above the tides rather
-------
25
1.5
0.5
Mean q
Sea Level
-0.5
Figure 1.1.2. Relationship between tides, wetlands, and reference elevations for an example estuarine
shore profile. The example elevations are based on the Hampton Roads (Virginia) Tide Station. See Gill
and Schultz 2001. The wetland characterizations are based on Kana et al. 1988.11
than above a fixed reference elevation such as
NGVD29. Second, we use tidal wetlands data to
produce a single (but important) supplemental
elevation contour, in addition to the conventional
topographic information.
We estimate elevations relative to the sea
because the intended use of these maps is to
analyze the implications of sea level rise. Early
assessments often ignored the difference
between the NGVD29 and mean sea level.
Because (local) mean sea level tends to be 10-20
cm above NGVD29, equating these two
reference elevations was harmless when
analyzing the impact of a 4.5-7.5-m (15-25-ft)
sea level rise by 2030 (SCHNEIDER and Chen,
1980), or even a 50-300-cm rise by 2100
(Barth and Titus, 1984). A more recent
analysis provided maps relative to NGVD29 for
the U.S. Atlantic and Gulf coasts, with an
explicit warning about the difference between
that benchmark and sea level (Titus and
RICH MAN, 2001). The print media generally
ignored the caveat and rewrote the map key from
"1.5 meters above NGVD" to "future shoreline
resulting from 1.5 meter rise in sea level," not
only confusing NGVD29 with sea level but also
equating elevation with shoreline change.'
ySee, e.g., "Coasts in Peril: Exhibit E" in "Life in the
Greenhouse", Time. 157:14:24.29 (April 9. 2001) "These
maps show how much of the shoreline we know today will
Unfortunately, the lack of interest in tidal datums
is not limited to sea level rise assessments: In New
Orleans, flood control engineers used NGVD29
and mean sea level interchangeably for decades,
even though mean sea level was 50-60 cm higher
than NGVD29. As a result, the levee along the
Inner Harbor Navigation Canal (which failed
during Hurricane Katrina) was about 60 cm lower
than intended (INTERAGENCY PERFORMANCE
EVALUATION TASKFORCE, 2006).
It is axiomatic that maps ought to depict the
information they seek to convey rather than leave
it up to the reader's imagination or ability to obtain
additional data. Unfortunately, the absence of a
data layer relating sea level to the fixed vertical
benchmarks has made it impractical for coarse-
scale national mapping studies to provide
elevations relative to the sea.10 As a byproduct of
vanish if sea levels rise by the indicated amount." But see
the -Yew York Times, January 1, 2000 (closely
paraphrasing the caveat that the journal article had
recommended).
' 'Consider for example, the state-scale maps showing land
below the 1.5- and 3.5-m (NGVD) contours in Titus and
Richman (2001). Expressing elevations relative to the
tides would have more than doubled the $75,000 cost of
that study.
Gill. S.K. and J.R. Schultz. 2001. Tidal Datums and
Their Applications, NOAA Special Publication NOS CO-
OPS 1. February 2001.
Tidal Flat
Open Water
(subtrdal)
Upland
Transition
High Marsh
Low Marsh
NAVD 089m
NGVD -0.172m
1.00
0
-1.00
-2.00
Tidal
Range
7.00
6.00
5.00
4.00
3.00
2.00
-------
[ 8 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Figure 1.1.3. Estimated elevations around Long Beach Isiand, New Jersey. The first three maps
show elevations relative to NGVD29 according to (a) the USGS 1:24,000 scale map, (b) spot
elevations provided by the Corps of Engineers where available and USGS data elsewhere, and (c)
our interpolations using wetlands data as a supplemental contour. The final map (d) shows the
same elevations as (c), relative to spring high water. The first map also shows the location of
spring tide flooding depicted in Photo 1.1.1.
Map D
l~ 1200 - 250
~ 150-200
_J 100 -150
¦ 50-100
¦ <50
a Tidal
¦ Wetlands
-------
[ SECTION 1.1 9 ]
Centimeters above
NGVD 1929
60 - 80
CI ¦ I 80-100
I I 100-120
031 > 120
# Tidal Range
Measurement
Measurement
Figure 1.1.4. Elevation of spring high water
relative to NGVD29. The red and black dots
depict the locations of reported observations for
mean tide level and spring tide range,
respectively. The various colors of the land
represent the interpolated values of spring high
water. For the actual values of mean tide level
and tide range observations, see Figures 1.1.6
and 1.1.7, respectively.
this effort, we create such a layer that others may
12
find useful even as LIDAR becomes available.
In ordinary conversations, people refer to
elevations "above sea level." This report provides
elevations relative to spring high water instead, for
two reasons: First, one can map the existing high
water mark more accurately than mean sea level
Wetland maps generally show the upper boundary
of tidal wetlands, but maps illustrating the location
of the shore at mean tide level are rarely available.
Second, showing elevations relative to high
water is more useful than mean sea level,
because the character of land changes
fundamentally once it is subject to the ebb and
flow of the tides: Marsh grasses replace trees,
lawns, or crops that cannot tolerate the saltwater
"NO A A is developing a software tool that converts data
between fixed benchmarks and elevations relative to the
tides, making this aspect of our analysis obsolete as well in
a few years. See, e.g., Parker et al. (2003) and Myers
(2005). Results are available for Pamlico Sound, which we
used.
13
and frequent flooding ' (see generally Teal and
Teal, 1969). Moreover, the land becomes
subject to tidal wetlands regulations,14 and
ownership shifts from the upland owner to the
public in most states (SLADE et al. 1990). By
contrast, elevation above mean sea level implies
little about the impact of sea level rise. Because
tide ranges vary, knowing that a parcel is 50 cm
above mean sea level does not tell one whether it
is even wet or dry land, let alone the rise in sea
level necessary to convert the area to open water.
Difference from Other Sea Level Rise
Impact Mapping Studies
This effort also differs from most sea level rise
impact mapping studies because we report
elevations rather than projected future shorelines.
Maps of future shorelines are important, but
elevations alone say something about vulnerability
to sea level rise.
Converting our results into maps of future
shorelines would represent, in effect, a separate
study—and the final results would be more
speculative. Elevation is a necessary precursor for
estimating shoreline change due to sea level rise.
But projecting future shorelines requires more
questionable assumptions than one must make
when estimating elevations. The Bruun (1962)
Rule produces an approximation of sandy beach
erosion that is useful for some purposes, but many
geologists decline to project erosion of beaches
without applying a more site-specific model
1 'This generalization does not always apply in areas with
low salinity. In nanotidal areas (i.e., areas where the
astronomic tide range is only a few centimeters) the "tidal
wetland" vegetation may be irregularly flooded because of
winds rather than regularly flooded from astronomic tides.
There may be a gradual transition between the irregularly
flooded wetlands and adjacent nontidal wetlands, and even
if the line is well-defined, the elevation is not a function of
the tides. The Pamlico and Albemarle sounds are the most
important example in our study area. Other exceptions
include tidal freshwater forests and areas where extensive
tidal freshwater wetlands are adjacent to nontidal wetlands
with similar vegetation types.
"Clean Water Act § 404, 33 U.S.C. § 1344(a) (1994) and
Rivers and Harbors Act of 1899, 33 U.S.C. §§ 403, 409
(1994).
-------
[ 10 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
requiring data collected over several years (e.g.,
Dean and Maurmeyer, 1983; Cowell and
Thom, 1994; Cowell et al., 1995; Young and
Pilkey, 1995). And sandy beaches are the best
known shores! Wetland accretion is too poorly
understood for coastal scientists to quantify how
rapidly the sea could rise before it began to drown
the wetlands (Kana et al., 1988; Park et al.,
1989; Cahoon et al., 1995).15 The ability to
predict erosion of muddy shores is so poor that for
many geologists, the term "coastal erosion" refers
only to sandy beaches.
Even in areas where we have a good model of
shore erosion, projecting future shoreline can
require a rather cumbersome set of analytical steps.
Future sea level rise is uncertain; so one must
evaluate the implications of several scenarios,
taking care to ensure that one has encompassed the
range of uncertainty. Different readers have
different time horizons, so one typically must
prepare maps for a few different projection years.
Finally, actual shoreline migration will also
depend on the type and extent of human activities
to hold back the sea, so one must consider
alternative shore-protection scenarios. Handling all
these issues well on a regional scale requires too
much effort to be undertaken as a final step of this
study.
Fortunately, coastal elevations do tell us something
about the impacts and responses to sea level rise.
Coastal wildlife managers who want to ensure that
new wetlands are created as sea level rises must
identify the dry land that might be tidally flooded
in the future. The importance of reserving a given
parcel depends on how much the sea has to rise
before the tides inundate the land. The need to
elevate streets and back yards depends on the
land's elevation. Moreover, an elevation map
makes a suitable graphic for those attempting to
convey the broad ramifications of sea level rise to
the general public because it shows both existing
wetlands and the dry land that will be inundated as
the sea rises.
15Elsewhere in this report however, a panel of wetland
accretion specialists provide a consensus subjective
assessment about whether mid-Atlantic wetlands could keep
pace with three sea level rise scenarios. (See Reed et al..
Section 2.1 of this report.)
-------
1.1.3 Application of Our Approach
Step 1: Obtain Best Elevation Data
Table 1.1.1 summarizes the elevation data we
used. For a given state, the order in which the table
lists the data represents the quality of the data and,
hence, the order in which we selected data layers.
For example, in Maryland, we used the 10-ft
contour from the Department of Natural Resources
spot elevation data set in areas where the USGS
maps had a contour interval of 20 feet.16 If USGS
7.5-minute maps had a contour interval of 10 feet
(or better), however, we preferred the USGS data.
For four counties, we had county data with 2- or 5-
ft contours, which was even better.
Our approach was more systematic than one might
initially assume, given the variation in data quality
indicated by Table 1.1.1. Our goal was to estimate
the land potentially inundated by a 1-m rise in sea
level where possible and, where we could not, at
least map the area vulnerable to a 2- or 3-m rise.
Although we would have preferred to rely solely
on a nationwide data set, the USGS 7.5-minute
maps do not have a consistent contour interval—
and for much of the coast their contour intervals
are too great, especially in New Jersey and
Maryland (see Figure 1.1.5). Therefore, we
attempted to supplement the USGS data where
feasible.
Outside North Carolina, the USGS 5-ft contour is
generally within 1 meter above the ebb and flow of
the tides. Therefore, outside North Carolina,
wherever the USGS maps had a contour interval of
5 feet or better, we did not actively seek better
data.
16We obtained LIDAR for the lower Eastern Shore of
Maryland after the analysis was complete. We use that
data to assess the accuracy of our DEM in the section on
Quality Control and Review. The primary data set we
make available to the public will include these LIDAR
data; we will also make the original data set available.
A 20-ft contour interval, by contrast, provides no
information about lands vulnerable to sea level rise
in any meaningful time horizon (although it does
identify areas that are not vulnerable). Therefore,
we made a relatively exhaustive effort to obtain
alternative data in the portions of New Jersey and
Maryland where the USGS maps had a 20-ft
contour interval. Fortunately, Maryland had spot
elevations on a 90-m grid with a vertical precision
(90 percent interval) of 5 feet. Thus, according to
national map accuracy standards (Bureau of the
Budget, 1947; Federal Geodetic Control
Subcommittee, 1998), the Maryland data provide
a 10-ft contour interval at a 1:180,000 scale. The
horizontal scale is considerably poorer than the
USGS 1:24,000 maps; but unlike a map with a 10-
ft contour interval, the spot elevations provide
estimates for points with intermediate elevations,
allowing us to derive, for example, a 5-ft contour
(albeit with twice the vertical error of national
mapping standards). Unfortunately, New Jersey
had no similar statewide data set.
Many counties have elevation data for coastal
floodplain management, pollution runoff
modeling, and identification of areas where slopes
make land undevelopable. Unlike the federal
government, however, the counties usually charge
for the data—sometimes tens of thousands of
dollars per quad. In some cases, the bonds used to
raise the money to collect the data contain
17
restrictions against giving the data away. The
restrictive county policies generally allow the GIS
department to provide the data to a genuine partner
doing work primarily to benefit the county. This
study probably would not—by itself—qualify
because we are analyzing the vulnerability of a
multistate region to rising sea level and creating a
product for researchers who will not, in general,
collaborate with county staff to attain county
objectives. Nevertheless, our collaboration with
17The planning director of Monmouth County, New Jersey,
expressed this concern.
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[ 12 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
four counties led four county GIS departments to
see this effort within the context of a joint federal-
local partnership to understand the implications of
rising sea level:
• Monmouth County (New Jersey): The only
county along New Jersey's Atlantic Coast
where USGS maps have a 20-ft contour
interval.
• Anne Arundel County (Maryland): This
county includes both Annapolis and the largest
low-lying area on Maryland's Western Shore
of Chesapeake Bay.
• Harford County (Maryland): This county
includes the second largest area of very low-
lying lands along the Western Shore.
• Baltimore County (Maryland). Unlike the
other counties, Baltimore insisted that we
provide elevation maps using their superior (2-
ft contour) elevation data before they would
even consider responses to sea level rise.
We also examined some maps that had been stored
in the warehouse where FEMA keeps the
documentation for the flood insurance rate maps.
In general, whenever the USGS maps had contour
intervals greater than 5 feet, FEMA obtained
topographic maps. As a test, FEMA searched their
archives for specific communities in Monmouth
County, New Jersey, and found that for about half
the townships and boroughs, the archives
contained numerous maps with 2-fft contours at a
scale better than 1:10,000. We were tempted to
have those maps all digitized. FEMA, however,
was reluctant to allow the entire collection to leave
their premises—and we were not sure that the
effort was worthwhile for areas with only partial
coverage. We did persuade FEMA to lend us their
map of Kent Island, Maryland, the eastern landing
of the Chesapeake Bay Bridge, where our own
eyes told us that the land is very low but the USGS
maps have a 20-ft contour interval.
The supplemental data sources left us with only 24
quads where we have nothing better than a 20-ft
18
contour interval. All of those quads are along
tidal rivers well inland or upstream from a major
estuary, except for six quads along the north shore
of Long Island, which is dominated by substantial
bluffs, and three quads in northern New Jersey (see
Figure 1.1.5).
Maps with 10-fft contour intervals give some
insight on vulnerability to sea level rise, but not
enough to justify their use if one can find a
practical alternative. Unfortunately for us, most
USGS maps have 10-fft contours in coastal New
Jersey, New York, Pennsylvania, Virginia, the
District of Columbia, and Virginia west of
Chesapeake Bay. For most low land along the
Atlantic Ocean and back barrier bays in New
Jersey (except for Monmouth County, where we
had 2-ft contours), the Corps of Engineers
provided spot elevations with sufficient precision
and density to identify 4-ft contour intervals at a
1:100,000 scale. The District of Columbia
provided 1-m contour data. The City of
Philadelphia provided 2-ft contours. Most of
Pennsylvania's remaining low land is in Delaware
County; because of the high tide range, the 10-fft
contours in that region are only about 150 cm (5
feet) above spring high water.
North Carolina is a special case. Currituck,
Pamlico, and Albemarle sounds have almost no
tides because the areas of these bodies of water are
large compared to their inlets to the ocean. With
the high water mark barely above sea level, the sea
would have to rise more than 1 meter to inundate
the 5-ft contour during a high tide, unlike areas
with larger tidal ranges. In the wake of Hurricane
Floyd, however, the state collaborated with FEMA
to substantially improve the already-good
elevation data with LIDAR. Early on in the study,
18Those 24 quads also included all or part of the upper
tidal portions of the Delaware River (Bucks County,
Pennsylvania, and Burlington County, New Jersey),
Choptank River (Caroline County, Maryland) Wicomico
River (Worcester County, Maryland), and several small
rivers or creeks in New Jersey.
-------
[ SECTION 1.1 13 ]
we obtained LIDAR for most of the low-lying
counties in the state19; and by the end of the study
we had data for the entire state. As we discuss
below, however, the absence of tides and tide data
for this area diminishes the usefulness of our
analysis for evaluating the possible impacts of sea
level rise in North Carolina.
Step 2: Use Wetlands Data to Obtain the
Location of the Upper Boundary of Tidal
Wetlands
We used tidal wetlands to define a supplemental
topographic contour, approximately equal to
spring high water. The precise elevation of that
contour varies, but it is almost always between
zero and the lowest contour above zero. This
supplemental contour is useful and important for
two reasons: First, for many purposes we are
interested in knowing elevations above the tides;
so a contour that defines the upper boundary of the
tides is essential. Second, where elevation
information is poor, a supplemental contour is
likely to be more accurate than elevations
estimated by interpolating with a model.
Table 1.1.2 lists our wetlands data sources. Just as
the USGS provides 7.5-minute quadrangles at a
1:24,000 scale for topography, so too the US Fish
and Wildlife Service's National Wetlands
Inventory (NWI) provides 1:24,000 maps with
broad wetland categories. Several states, however,
have developed their own wetlands maps;
representatives from New Jersey, Maryland, and
North Carolina asked us to use their data instead of
the NWI maps.20
The key limitation of the NWI data is its age: the
aerial photographs for New Jersey were from the
1970s, and the Maryland and North Carolina
19As we discuss, we obtained LIDAR for the rest of the
state after we developed our elevation data. As with the
Eastern Shore of Maryland, we use these data to assess the
accuracy of our procedure and will make the better
LIDAR data available to the public.
2uNew York also provided wetland data for a portion of its
coastal zone. Delaware also has its own wetland data, but
state officials did not specifically ask us to use their data,
and given the cost of interpreting each new data set, we
did not.
21
photographs were from the 1980s. Since then
wetland shores have eroded, low dry land areas
have converted to wetlands, human activities have
22
converted wetlands to dry land, and some
previously drained areas have converted back to
23
wetlands. A second limitation of NWI is scale.
Small fringing wetlands along tidal creeks
sometimes do not show up in the NWI data set,
even though they are large enough to be seen on a
1:24,000 scale map. Given these limitations, and
the availability of data that state agencies trust
more for their uses, we took the three states' advice
and used their data.
We use wetlands only to define the inland limit of
tidal wetlands. Kana et al. (1988) originally
proposed the approach that we apply here. While
surveying marsh transects around Charleston
(South Carolina) and Long Beach Island (New
Jersey), they recalled that low marsh is generally
flooded twice daily and high marsh is flooded at
spring tides but not every day. With an estimate of
mean high water and spring high water, they
reasoned, the wetland zonation can give
supplemental elevation contours at both mean high
water24 and spring high water. PARK et al. (1989)
first applied that approach. Although their
LANDSAT imagery did not distinguish between
low and high marsh vegetation, Park et al.
attempted to do so by obtaining imagery at high
tide during "half moons" (i.e., at mean high water)
and delineating the flooded areas. The NWI and
state wetlands data we used, however, made no
such distinctions.
01See NWI Status Photo Page, accessed April 1, 2005, at
http ://www. nwi.fws. gov/statusphotoage. htm.
"Tidal wetlands are rarely converted to dry land for
development, but occasionally some loss will be permitted
for water-dependent uses such as marinas and ports. See
generally U.S. EPA and U.S. Army Corps of Engineers
(1990) (explaining the federal policy on wetland
mitigation under section 404(b)(1) of the Clean Water
Act).
23Along Delaware Bay, for example, diked wetlands had
been converted to agriculture for more than a century. As
part of an enviromnental mitigation program for a PSE&G
nuclear power plant, most of the coastal zones of
Cumberland County, New Jersey, and areas across the Bay
in Delaware are being returned to nature.
24Mean high water is the average water level at high tide.
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[ 14 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Table 1.1.1. Elevation data sources used in original analysis.
Area Included
Data Source
Scale
Contour Interval or
Eauivalent Precision
Benchmark
New York
Entire state
USGSa
1:24.000
5 or 10 ft
NGVD29
New Jersey
Monmouth County
County datab
1:1,200
2ft
NAVD88
Atlantic coast east of US-9
Corps of Engineers, spot elevations0
2ft
NGVD29
Atlantic, Delaware Estuary
USGS
1:24,000
5 or 10 ft
NGVD29
North Jersey
USGS
1:24.000
10 or 20 ft
NGVD29
Pennsylvania
Philadelphia
City datad
1:2,400
2ft
PVDd
Delaware and Bucks counties
USGS
1:24.000
10 and 20 ft
NGVD29
Delaware
Entire state
USGS
1:24.000
Mostly 5 ft
NGVD29
Maryland
Baltimore County
County data®
1:100
2ft
NAVD88
Anne Arundel County
County data'
1:2,400
5ft
NAVD88
Harford County
County data9, excludes Aberdeen
Proving Grounds
1:2,400
5ft
NGVD29
Kent Island
Hard-copy map FEMA used for flood
insurance rate maph
1:7,200
2ft
NGVD29
Dorchester County and
nearby
Southern part of state, both E
USGS
1:24,000
1 m
NGVD29
USGS
1:24,000
5ft
and W shores
Potomac and Western Shore
USGS
1:24,000
Mostly 10 ft,
some 20 ft
NGVD29
Statewide except for a few
small areas
Maryland DNR spot elevations'
90-m grid
10ft
NGVD29
Northern Eastern Shore
USGS 1:24.000
1:24.000
Mostly 20 ft
NGVD29
District of Columbia
Entire district
City dataj
1:1.000
1 m
NAVD88
Virqinia
Entire state
USGS
1:24,000
5 and 10ft
NGVD29
State LIDAR project with FEMA*
40 cm
Mostly 5 ft, some 2 m
NAVD88
NAVD88
North Carolina
Most of Pamlico and
Albermarle sounds to ocean
Elsewhere USGS 1:24,000
a USGS. Large Scale Digital Line Graphs, http://edc.usgs.gov/products/map.html accessed May 1, 2006.
b U.S. Army Corps of Engineers, St. Louis District. 1999. Intercoastal Waterway, NJ: Spot Elevations (LFHYPELS)._Prepared by ADR,
Inc., Pensauken, NJ. Vertical position accuracy: 1 ft. Horizontal position accuracy: 5.0 ft.
Monmouth County Office of Geographic Information Systems. 1997. Contours. Contour interval: 2 ft. Scale: 1:1200. Complies with
National Map Accuracy Standards.
d City of Philadelphia Water Department, Information Systems and Technology. 1996. Philadelphia Vertical Datum. "The Philadelphia
datum was first established in 1682 by Wlliam Penn with a metal spike in the Delaware River pier at the foot of Chestnut St based on
the mean height." Metadata file accompanying Philadelphia 2-ft contours. NAVD (1988) is 4.63 ft lower than the PVD.
Baltimore County, Maryland. 1997. Baltimore County Topo Data. Towson, Maryland: Baltimore County OIT/GIS Services Unit. Complies
with standards of the American Society Photogrammetry and Remote Sensing as well as with National Map Accuracy Standards.
f Anne Arundel County, Maryland. 1995. Anne Arundel County 1995 Topographic Mapping. Prepared by Photo Science, Inc. (now
EarthData International, Inc.) for Anne Arundel County, Department of Public Works. Scale: Annapolis: Anne Arundel County Office of
Information Technology. Complies with National Map Accuracy Standards.
9 Harford County, Maryland, undated. Harford County 5-ft contour elevation maps. Contour Aberdeen: Harford County GIS Department.
h GEOD Surveying and Aerial Mapping Corporation. Kent Island, Maryland. Map prepared for the Flood Insurance Rate Maps of Kent
Island, Project No. 1381-107. Archived by Dewberry and Davis, Annapolis, Maryland. Provided by the FEMA Flood Insurance
Administration. Scale: Contour. Complies with National Map Accuracy Standards.
' Maryland Department of Natural Resources. 1992. Digital Elevation Models. Vertical position accuracy: 5 ft. Horizontal Accuracy, 33 ft.
' National Capital Planning Commission and District of Columbia Department of Public Works. 2001. Rooftop Elevation and Ground
Elevation. Washington, D.C.: Office of Chief Technology Officer. Complies with the National Map Accuracy Standards.
k Floodplain Mapping Program, North Carolina Division of Emergency Management. May 2002. NC Floodplain Mapping: 50 ft
Hydrologically Corrected Digital Elevation Modelv.1. White Oak, Tar-Pamlico, Neuse, and Pasquotank basins. Vertical accuracy: 20 cm
for coastal counties.
-------
[ SECTION 1.1
ATLANTIC
OCEAN
Contour Intervals
Spot Elevation
Lidar
2 Feet
1 Meter
5 Feet
10 Feet
10 Feet, State Data
20 Feet
Figure 1.1.5. The elevation data used in this study. Rectangles generally signify USGS 1:24,000 data.
The USGS maps had a 20-ft contour interval for the (pink) quads in Maryland where we used state
data, and most or all of the four counties where we obtained 2- or 5-ft contour data (but 10-ft contours
in the City of Philadelphia). We obtained the Maryland LIDAR and some of the North Carolina LIDAR
after interpolating the elevations, and hence use that data to assess the accuracy of our approach.
The final data set we provide has LIDAR for all of North Carolina.
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[ 16 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Table 1.1.2. Wetlands data used in this study
State
Countv
Data Source
Year for
Imaaerv
Scale
Suffolk, Nassau, Rockland,
NWIa
1980,1990
1:24,000
Hudson above Tappan Zee
New York
New York City, Westchester:
Long Island Sound and
Hudson below Tappan Zee
New Yorkb
1974
1:12,000
All but part of Delaware River
Rutgers Land Cover0
1995
30-m grid
New Jersey
Delaware River upstream of
Commodore Barry Bridge
NJ Upper Wetland
Boundary01
1970
1:12,000
Pennsylvania
Entire state
NWIa
1980
1:24,000
Delaware
Entire state
NWIa
1982
1:24,000
Maryland
All but three areas where
data laggedf
Three areas where DNR data
laggedf
MD-DNR8
NWIa
1988-1995
1980s
1:12,000
1:24,000
District of
Columbia
Entire district
NWIa
1983
1:24,000
Virginia
Entire state
NWIa
1990,2000
1:24,000
North Carolina Entire state NC DENRS 1981-1983 and 1994 1:24,000
a U.S. Fish and Wildlife Service. National Wetlands Inventory, http://www.nwi.fws.gov/ [accessed January 2006.] Scale: 1:24,000. The following
types of polygons were treated as tidal wetlands: M2RS (Rocky Shore), M2US (Unconsolidated Shore), E2RS (Rocky Shore) E2US
(Unconsolidated Shore), E2EM (Characterized by erect, rooted, herbaceous hydrophytes), E2SS (Scrub-shrub), E2FO (Forested). In
addition, for areas with a water-regime characterized as N (Regularly Flooded-exposed daily), P (Irregularly Flooded, less than daily), S
(Temporary-Tidal), or R (Seasonal-Tidal), we also used L2EM and PEM (both characterized by erect, rooted, herbaceous hydrophytes),
L2RS (Rocky Shore), L2US and PUS (Unconsolidated Shore), PML (Moss-lichen), PSS (Scrub-shrub), and PFO (Forested). In cases
where the water regime was unknown, we included a polygon-specific inspection.
b New York State Department of Environmental Conservation. 2000. Tidal Wetlands Map: 1974.
0 Rutgers Land Cover. Richard Lathrop. 2000. New Jersey 1995 Level III Land Cover Classification. Grant F. Walton Center for Remote Sensing
and Spatial Analysis, Rutgers University. Reported in: Richard G. Lathrop. 2001. Final Report. Land Use/Land Cover Update To Year
2000/2001. NJ DEP. http://www.nj.gov/dep/dsr/landuse/landuse00-01.pdfaccessed January 2006.]
d New Jersey Department of Environmental Protection. NJDEP Upper Wetlands Boundary/Upper Wetlands Limit for New Jersey.
6 Maryland Department of Natural Resources Wetlands Data. 2001. Chesapeake and Coastal Watershed Services, Geographic Information
Services Division. Minimum mapping unit: % acre. Scale: 1:12,000. Codes same as for NW.
f The three areas where DNR data lagged: (a) Caroline, Talbot counties south of Easton-St Michaels, and parts of Dorchester along the
Choptank River; (b) Cecil and Kent except for Chester River and Chesapeake Bay south of Rock Point; (c) Baltimore County west of Glenn L.
Martin airport and Baltimore City north side of Baltimore Harbor.
9 North Carolina Department of Environment and Natural Resources. 1999. DCM Wetland Mapping in Coastal North Carolina. Scale: 1:24,000
for portions relying on NWI and soils data. (Note: Scale is 1:58,000 for nontidal wetland boundaries areas relying on 30-m grid data [1994
update]. Those boundaries do not inform our elevation data, but do affect calculations of the area of nontidal wetlands vulnerable to sea level
rise.) Polygons with a code of 1, 3, or 15 were treated as tidal wetlands, as well as any polygons identified with the code "e" (estuarine wetland).
-------
[ SECTION 1.1 17 ]
New Jersey and North Carolina were special cases.
For most of New Jersey, we used the 30-m grid
data developed by Richard Lathrop for the State of
New Jersey. These data provide a more detailed
vegetation classification system, and it would have
been possible to differentiate low from high
marsh.25
For much of North Carolina, by contrast, we
lacked the wetlands data necessary to completely
apply our approach. Pamlico and Albemarle
sounds, as well as their tributaries, are nanotidal
estuaries: their astronomic tide ranges are so small
that for most practical purposes there are no tides.
As a result, wetlands data sets misleadingly
classify the wetlands along the shore as "nontidal
wetlands." Unlike true nontidal wetlands, these
wetlands are at sea level and experience the full
force of the tides in the bodies of water to which
they are attached. Thus, unlike nontidal wetlands,
which would eventually be inundated by a rising
sea level, the nanotidal wetlands are already
inundated. But the wetlands data do not distinguish
the nanotidal wetlands from the nontidal wetlands
(other than areas where salinities are high enough
in the estuary to support brackish marsh). Thus, the
wetlands data do not provide the location for the
supplemental contour we would have hoped to
create. North Carolina's LIDAR provided us with
better elevation data than we would have been able
to derive using the wetlands data; but the failure of
the data to distinguish nontidal wetlands from
nanotidal wetlands changes the meaning of any
estimates of the area of tidal wetlands in North
Carolina.
Step 3: Use Information on Tide Ranges
and Benchmark Elevations to Estimate the
Absolute Elevation of the Upper Boundary
of Tidal Wetlands
Creating a supplemental contour using wetlands
data requires us to have an estimate of the
elevation of the upper tidal wetland boundary.
That elevation depends on the elevation of mean
25This study did not make such a differentiation. However,
we provided the data for Ocean County for the study by
Jones and Strange (Section 3.20 in Section 3 of this
report), which did make such a distinction.
tide level26 (MTL) (relative to the benchmark) and
the tidal range.
Relate benchmark elevations to mean tide level.
NOAA's Published Benchmark Sheets (NOS,
2005) and the corresponding National Geodetic
27
Survey (NGS) Data Sheets' provide estimates of
the difference between mean tide level and the
benchmark elevations at 125 locations throughout
the study area. As Figure 1.1.6 shows, the majority
of those locations are in or adjacent to New Jersey.
Observations are especially sparse, by contrast, in
the sounds of Long Island and North Carolina.
Typically, mean tide level in the ocean is approx-
imately 20-30 cm above NGVD29 in the mid-
Atlantic, reflecting the rise in relative sea level
since the benchmark was established. The average
water level in a back bay, however, is often several
centimeters higher than the mean tide level on the
ocean side of the barrier island:28 The cross
sections of inlets and channels are greater at high
tide than low tide. As a result, a flood tide brings
more water into the bay when the inlet is 1 meter
above the bay than the ebb tide carries away when
the inlet is 1 meter lower. Therefore, ignoring
rainfall, the flows during the ebb and flood tides
are in balance only if the average bay level is
somewhat higher than the ocean.
Rainfall and runoff are additional sources of water
in estuaries, further increasing water levels relative
to the nearby ocean. During wet periods, water
levels in back bays behind barrier islands may be
10-30 cm higher than normal. This effect may be
greatest in freshwater tidal rivers, given their
distance from the ocean and prevailing seaward
flow of water. Hence, as Figure 1.1.6 shows, mean
tide level is higher at Philadelphia and
Washington, D.C., than along the shores of
26Mean tide level is the average of mean high water and
mean low water. It is generally very close to mean sea
level (the average water level) but requires fewer data
points to calculate.
27The Published Benchmark Sheets include links to the
NGS information relating mean tide level to the vertical
benclunark elevations.
28For example, the stations inside Little Egg Harbor Bay
near Long Beach Island (New Jersey) show MTL to be
about 1.25 feet above NGVD29.
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[ 18 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Delaware and Chesapeake bays, respectively.
Along major bodies of water, the coverage is
sufficient to estimate the elevation of mean tide
29
level through interpolation. For back bays
lacking such data, we assumed that the elevation of
mean tide level was similar to that of a nearby bay
where data are available. The complete lack of
data for Albemarle and Pamlico sounds was the
most problematic. Fortunately, we had the best
land elevation data—LIDAR—for that area; thus
our need for a supplemental contour based on
wetlands and tidal data was least. NOAA has
developed a hydraulic model to estimate water
levels in Pamlico Sound, but not Albemarle
Sound; we used the NOAA results wherever they
were available (Parker et al., 2003; Myers,
2005).
Use tidal range data to estimate the elevation
of spring high water. Estimates of tide ranges are
more prevalent than the absolute elevation of mean
30
sea level. NOAA's tide tables provide
31
estimates of the mean and spring-tide range at
768 discrete locations in the study area (see Figure
32
1.1.7). As with the elevation of mean tide level,
coverage is poor in Albemarle and Pamlico
sounds, where astronomic tides are small
compared to wind-generated tides; and again we
used NOAA's model for Pamlico Sound. The
NOAA estimates consider only astronomic tides,
whereas tidal wetlands are also found in areas that
are flooded irregularly by the winds. The
distinction is minor in areas with a large tidal
range, but where astronomic tide ranges are small,
29We interpolated elevations using the TopoGrid function
inESRI's Arclnfo Grid module (ESRI, 1998). See the
section on Step 3 for additional details on interpolation
algorithms. The algorithm allowed us to treat intervening
land as a "barrier" in the interpolation. In a back bay, for
example, we use measurements from the bay—but not
nearby ocean locations, because the impoundment effect
of an inlet can elevate mean tide level within the bay.
" See, e.g., NOS (2004). The hard-copy report "Tide
Tables" is now provided online. In 2004 it was still called
"Tide Tables" but more recent versions of the web site
have dropped the traditional title.
The estimates in the NOAA tide tables are long-term
averages.
32EachUSGS 1:24,000 scale map includes an estimate of the
mean tide range, which Park et al. (1989) used in their
assessment.
the wind-generated tides tend to enable wetland
vegetation to form tens of centimeters above mean
tide level, even if the spring tide range is
negligible.
As with mean tide level, we used the available data
to estimate the spring tide range through
interpolation. We then calculated the elevation of
spring high water relative to NGVD29 for the tidal
epoch 1983-200133 as one-half the spring tide
range plus the elevation of mean tide level
calculated in the previous subsection. Based on
various wetland transect studies relating wetland
elevations to the tides (e.g., Kana et al., 1988), we
assume that this elevation also represents the
elevation of the upper boundary of tidal wetlands.
This assumption is only an approximation:
wetlands may extend above spring high water, for
example, in areas with small tide ranges where
winds frequently cause areas above spring high
water to flood. This discrepancy will not affect our
estimate of the amount of dry land within (for
example) 50 cm above spring high water; but it
does lead us to overlook that some of the land (for
example) 50-75 cm above spring high water
would be flooded enough to support tidal wetlands
if sea level rises 50 cm. This error is small
compared to the accuracy of most USGS
topographic maps—but it would be very
significant in areas where LIDAR is available.34
33NOAA's Published Benchmark Sheets adjust estimates
of mean tide level so that they refer to the mean tide level
averaged over a 18.6-yr lunar cycle. See, e.g.. Gill and
Schultz (2001).
4 Commenting on this report, Christopher Spaur of the
Corps of Engineers provided the following: Regularly
flooded tidal marshes have a predictable—and easily
ascertainable—flooding regime controlled by astronomical
tides, and along the Atlantic Coast possess broad areas
dominated by tall-form Spartina alterniflora. Irregularly
flooded marshes are found in areas where the pattern of
flooding is at most partly related to astronomical tidal
regime instead of wind and seasonal tides (e.g., wet and
dry periods causing water levels to vary). These marshes
lack the pronounced break between tall-form Spartina
alterniflora and other marsh plants that occurs in regularly
flooded marshes (Frey and Basan, 1985). Surfaces are
subject to long periods of exposure and inundation (Stout,
1988). Because duration of inundation determines the
lower limits of marshes, the longer duration of inundation
causes the lower limit of marshes to be higher than in an
area where tides dominate. The surface of irregularly
-------
[ SECTION 1.1 19 ]
How accurate is our surface estimating spring high
water? The NOAA data on spring tide range and
mean tide level are based on substantial data and
thus are precise for our purposes. Interpolation
model error, however, can be significant. In large
estuaries with substantial data, the variations of
spring tide range from location to location are on
the order of 5 cm; hence our interpolation error is
likely to be small. In back barrier bays, however,
tide ranges can vary by tens of centimeters. In
many cases, the tide range simply dampens away
from the inlets, and interpolation between stations
can largely account for this dampening. In some
cases, however, there are tidal creeks with no tide
stations. In these locations, our error in calculating
spring tide range—and hence spring high water—
is likely to be on the order of tens of centimeters.
Adjusting tidal elevations to account for sea
level rise. Only by sheer coincidence would the
wetland maps be based on imagery taken during
the midpoint of the 19.6-year tidal epoch that
NOAA used to define local mean sea level. Given
our assumptions, the wetlands maps provide the
location for spring high water the year the photos
were taken. In parts of New Jersey, sea level has
risen 10 cm since the photos were taken (e.g.,
Permanent Service for Mean Sea Level,
2003). Even though this discrepancy is less than 5
cm in most areas, we corrected for it because it is a
systematic error that can be corrected, unlike the
substantial random error resulting from large
contour intervals of most elevation data.
We used the regression coefficients published by
35
the Permanent Service for Mean Sea Level for all
locations with more than 40 years of data (see
Figure 1.1.1). We then estimated the current rate of
sea level rise at intermediate locations through
interpolation. Multiplying that rate by the number
flooded marsh occurs at about mean high water (Reimold,
1977). In the coastal bays, where tidal range is generally
30-50 cm, the elevation range across the marsh surface is
much less and the marshes tend to lack much habitat
below MHW or so. The short form of Spar tin a alterniflora
is dominant on the seaward edge, and the tall form is either
lacking or very local in occurrence along tidal creeks.
The Service obtains the data for the United States from
NOAA's National Ocean Service.
of years between the map date and the NOAA base
year provided us with site-specific adjustments to
our surface estimating the elevation of spring high
water.
Step 4: Interpolate Elevations Relative to
the Vertical Datum for All Land above the
Tidal Wetlands Using Elevations Obtained
from the Previous Three Steps
From the aforementioned steps, we had the
standard elevation contours, plus a supplemental
contour along the upper boundary of tidal
wetlands. We now examine how we used those
contours to characterize elevations of locations
between the contours. Doing so required us to
decide on a rule for addressing data conflicts and
pick an interpolation algorithm.
The primary potential for data conflicts concerned
discrepancies between topographic contours and
the tidal wetland boundary. Along the Delaware
River and parts of Delaware Bay, the upper edge
of the tidal wetlands is about 4 to 5 feet
(NGVD29), so we expected the wetland boundary
to occasionally be landward of the 5-ft contour. In
areas with 2-ft and 1-m contours, we expected to
see a similar overlap even in areas with low tidal
ranges. We limited ourselves to two possible
solutions: Either the wetlands data or the contour
always takes precedence over the other.
We decided that the wetlands data should take
precedence over the contour information, for three
reasons. First, accepting both data sets at face
value, the elevation and wetlands data typically
had a scale of 1:24,000 and hence an allowable
horizontal error of 12 m. But the topographic maps
also have a vertical error of one-half contour
interval. Therefore, by its very terms, the typical
topographic map allows for the possibility that the
5-ft contour may be as low as 75 cm (2.5 ft)
(NGVD29), which would be tidal wetlands in most
37
areas. Second, the wetlands data are newer.
36With the exception of Maryland, we used only one
source of standard topographic data in a given location.
For Maryland, where we used USGS and MD-DNR
information, the USGS contours took precedence.
37USGS has made planimetric updates to most of the maps
since 1970. However, the contour dates are generally from
-------
[ 20 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Because of shore erosion, wetlands may now exist
in areas that had previously been above the 10- or
20-ft contour. Finally, this approach leaves us with
a reasonable landscape. If we gave precedence to
the 5-ft contour, we would be left with a bluff over
the wetlands along the 5-ft contour; removal of the
5-ft contour, by contrast, means that we interpolate
between the wetlands and the 10-ft contour.
In selecting an interpolation algorithm, we had to
consider our three objectives:
• Estimate the amount of land that could be
inundated by rising sea level to the level of
precision allowable by existing data.
• Produce maps depicting the elevations of land
close to sea level.
• Provide an elevation data set for other
researchers.
Estimate the amount of land that could be
inundated. The contours provide polygons of
various elevation classifications. In a location with
a 5-ft contour interval, for example, we have
polygons that represent the land between spring
high water and the 5-ft (152-cm) (NGVD29)
contour, as well as 152 to 304 cm, etc. If spring
high water happens to be 60 cm above NGVD29
in a given area, then we have polygons that tell us
how much land is 0 to 92 cm above spring high
water, as well as 92 to 244 cm, etc. However,
contour intervals and the elevation of the tides
vary, so the polygons in different locations
represent different elevation ranges relative to the
tides. This situation prevents us from simply
adding the calculated area across all localities.38
Estimating the amount of land at particular
elevations requires an assumption about how
elevations are distributed in the land between the
contours.
We considered two approaches for estimating
elevations between contours: using linear
the 1945-1970 period. See, e.g., the order forms provided
by the New York State Center for Geographic Information
(showing the planimetric and contour dates for every
USGS 7.5-minute quad). Accessed on August 12, 2006, at
http://www.nysgis.state.ny.us/mapssales/orderfnn/brantlk.
htm.
38In areas where we have accurate spot elevations (e.g.,
LIDAR), we do not face this problem.
interpolation and using a digital elevation model
(DEM) to fit an estimated land surface through the
contour data we had. We tried the DEM approach
first, because it was going to be necessary for
creating the maps. We quickly concluded,
however, that readily available algorithms would
unreasonably skew our results. When the shore
and the contours are all fairly straight or well-
behaved, results seem reasonable; but when the
contours have sharp turns, the algorithms assume
that a disproportionate amount of land has an
elevation close to that of the contour. In effect, the
algorithms tend to create plateaus on either side of
the contours.39
Therefore, our estimates are based on linear
interpolations; i.e., we assume that elevation is
uniformly distributed between contours. To keep
the calculations manageable, we interpolated
elevations at the quad level.40
Produce maps and elevation datasets. We
interpolated between the contours and spot
elevations using the TopoGrid algorithm provided
by ESRI (1998) software. This procedure was
developed based on Hutchinson's (1988, 1989)
approach to estimating DEMs. The fundamental
insight embodied in that algorithm is that ground
surfaces have many local peaks, but few local
minimums, because water generally flows toward
the sea rather than being impounded. For our
purposes, that aspect was not important because
we are not concerned about slopes; instead we are
concerned with improving the accuracy of
"9In Figure 1.1.8, TopoGrid correctly creates a stream valley
in an area with a fairly simple topography. But when we
applied that algorithm over our entire study area, we found
numerous plateaus along the contours. Someone more skilled
with the algorithm may have been able to set parameters to
better replicate normal topography; but this algorithm was
designed for correct drainage, not for correctly duplicating
the distribution of elevations.
4uFor each quad, we estimated the average elevation of
spring high water (SHW). We then calculated the amount
of land between SHW and the 5-ft contour, and allocated it
proportionally between 0 and 5-SHW. We then calculated
the land between 5 and 10 feet and allocated it between 5-
SHW and 10-SHW. We stored the results in bins of 0.1
feet. We followed this approach twice for each quad, so that
we could distinguish nontidal wetlands from dry land (using
nontidal wetlands polygons from the data sources displayed
in Table 1.1.2).
-------
[ SECTION 1.1 21 ]
elevations at particular locations and correctly
describing the overall distribution of elevations.
Nevertheless, the algorithm's use of stream data to
characterize slopes should tend to ensure that
stream valleys are captured below the lowest
topographic contour, even in areas where the
stream is above the tides (and hence would not
provide a contour)41 We used a cell size of 30
meters because when we began the study, a 10-m
cell size slowed processing time too much.
Before settling on TopoGrid, we tested three other
readily available algorithms: inverse distance
weighting42 (IDW), spline,43 and triangulated
irregular networks (TIN),44 using the (5-ft interval)
contours in the general vicinity of Ocean City,
Maryland. All four algorithms created plateaus
near contours with sharp curves, with
approximately the same amount of land having an
elevation within 15 cm (0.5 feet) above or below
the contour as the amount of land with an elevation
15 to 75 cm above or below the nearest contour.
Figure 1.1.8 compares the four algorithms. Each
started with the same set of set of contours, with a
circular hill to the right, a U-shaped bluff to the
left, a stream valley in between, and a shore that is
otherwise fairly straight. The various colors
represent the elevations that the four algorithms
estimated. Between the 20- and 40- ft contours, the
yellow-brown and pink-red shades in the
TopoGrid and TIN maps suggest that these
algorithms create intermediate elevation contours
that are evenly spaced between the input contours.
IDW, by contrast, assigns virtually all of this land
to elevations of 20, 30, or 40 feet, as if the land
41If there is a 10-fit contour on either side of a creek,
without additional information, an interpolation algorithm
is likely to assume that the land between the contours (the
stream valley) is also at 10 feet.
42IDW interpolates by defining the elevation of a point X
as the weighted average of points A within a given
neighborhood, with the weights being the inverse of the
distance between X and the various points X, possibly
raised to a power. See, e.g., Shepard (1968), Fisher et al.
(1987), and Childs (2004).
43See, e.g., Childs (2004).
44A TIN is a digital data structure that represents terrain
with a series of triangles. We used the ESRI command
"CreateTin". See, e.g.. Price (1999).
were a series of steps. Spline creates 50-ft and 200-
ft hills between the 20- and 30-ft contours for no
obvious reasons. This example generally
confirmed the literature: IDW is more appropriate
when one has many points that already outline the
shape of the surface (e.g., Childs, 2004). Spline
tends to produce spurious hills, especially with
unevenly spaced input data (e.g., Rogers and
Satterfield, 1980; Olsen and Bliss, 1997).
Given the relatively large study area, we needed an
algorithm that required less supervision than
spline.
Our choice between TIN and TopoGrid was a
close call. In areas where the contours are one or
two cells apart, TIN faithfully interpolates between
the contours, whereas TopoGrid seems prone to
horizontal errors of one or two cells. TIN
completely misses the stream valley, however,
treating both the valley and the U-shaped hill as a
single flat area. TopoGrid, by contrast, creates a
stream valley with a reasonably constant slope
between the 10- and 20-ft contours. Similarly, TIN
assumes that all the land within the 40-fft contour is
at precisely 40 feet, whereas TopoGrid creates a
peak in the center just above 45 feet. We decided
to use TopoGrid because we were more willing to
tolerate its one- or two-cell errors than maps that
missed hills and streams.
Step 5: Use the Information from Step 3 to
Calculate Elevations Relative to Spring
High Water
We conducted both sets of interpolation relative to
the fixed benchmark elevation. We created maps
and a data set of elevations relative to spring high
water by subtracting our estimate of the elevation
of spring high water from every data point. We
derived our estimates of the area of land within a
given elevation above spring high water by
subtracting the average elevation of spring high
water within a given USGS quad from the
elevation of the contours between which we were
interpolating. The effect of this conversion is that
our maps show the land below a given contour
(e.g., USGS 5-ft contour) to be lower in areas with
large tide ranges than in areas with small tide
ranges.
-------
[ 22 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
PA
NY
NJ
>
c
z
DC
MD
t
(
iff
DE
ATLANTIC
VA
OCEAN
NC
Elevation of Mean Tide Level
(cm above NGVD29)
5 15 25 35 45 55
Each dot represents one measurement
Figure 1.1.6. Observations of mean tide level used in this study. This map depicts the 125
observations from NOAA's Published Benchmark Sheets and the National Geodetic Survey's data
sheets used in this study to create a surface depicting mean tide level relative to NGVD29.
-------
[ SECTION 1.1 23 ]
S
PA
NY
r^
j
/
) NJ
u
I.'
I
J
VA
s *r'
•v h
NC
£
ATLANTIC
OCEAN
Spring Tide Range (centimeters)
0 30 60 90 120 150 180 270
Each dot represents one measurement
Figure 1.1.7. Observations of tide ranges used in this study. This figure depicts the 768 observations from
NOAA's tide tables used in this study to create a surface depicting spring tide range.
-------
[ 24 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Spline •
4)
LLI
Comparison of
Interpolation Methods
• TIN
¦ TopoGrid
Spline
IDW
TopoGrid
Elevation (ft)
=
10
20
30
I
45
60
200
Figure 1.1.8. Test of four interpolation models. The colors represent the elevations calculated by each
of the four algorithms for the same set of contours. The box to the left shows a cross section of the
elevations as one travels from point A to point B for the surfaces created bv each alqorithms.
-------
1.1.4 Quality Control and Review: Error Estimation
We corrected all the errors and questionable
aspects that we noticed—but a test of what we did
not notice was also necessary. We enlisted Russ
Jones of Stratus Consulting to test the algorithm
and validate the results against an independent data
set. Let us briefly examine the results of the tests
we asked him to perform.
Testing the interpolation algorithm
The intent of the algorithm is to interpolate
between contours. Values that are outside the
contours represent a failure, regardless of whether
the problem is caused by TopoGrid or some other
error. We asked Jones to pick 12 representative
quads, including at least 1 quad for each state,
encompassing the different contour intervals and
data sources. After he picked the quads, we sent
him the DEM (grid) results and the input data (see
Table 1.1.1) representing polygons of land
between the wetlands and the first contour (e.g., 5
ft), the first and second contour (e.g., 5-10 ft), etc.
For each quad, we asked him to compare the areas
of the source contour polygons with those of the
interpolated DEM for the same elevation range
and to produce a histogram of the DEM elevations
by contour polygon.
Table 1.1.3 shows the results of this comparison.
Topogrid did not duplicate the area of dry land
below the lowest contour as well as we had hoped,
with percentage errors of 20 percent or more in 5
of the 12 quads. For the second and third contours,
the percentage error was less than half as great, but
hardly inspiring.
The errors do not seem as large, however, when
viewed as vertical error. The fourth column in
Table 1.1.3 provides the "effective" elevation of
the polygon contour as estimated by the DEM.45
45That is, the elevation below which the DEM estimates an
area equal to the polygon area below the first contour.
For example, the polygon area below the 2-m
contour of the Merry Hill quad is 241 ha. Although
the DEM found only 152 ha below the 2-m (6.56-
ft) contour, it also finds 241 below 6.67 ft.46 In 8 of
the 12 quads, this effective elevation is less than
0.11 feet above the corresponding USGS contour.
The area error is large and the vertical error is
small, because the algorithm created a plateau
along the contour; more land was slightly above
the contour than slightly below it.
Moreover, in most quads, most of the land below
the first contour is tidal wetland. Hence, an error of
20 percent of the dry land is typically about 5
percent of the total land. Thus, if we included all
low land in the denominator, our percentage error
estimates for the lowest contour would have the
same magnitude as for the other contours. This is
particularly true for the Middle River quad in
Baltimore County, Maryland, where the dry land
below the 2-ft (NAVD88) contour is a very narrow
strip adjacent to the tidal wetlands, whose inland
boundary is often 1.5 feet above NAVD88. Thus,
any such dry land in our data set may largely
represent errors in the input data. We are unable to
explain why our algorithm underestimated the low
land below the first contour for the other 10
47
quads, but it may be an artifact related to the
relative complexity of wetland shores.
Comparing results with an independent
dataset
As this study proceeded, LIDAR data became
available for the entire state of North Carolina as
well as Maryland's Eastern Shore south of Rock
Hall (MD DNR, 2004). JONES (2007) converted
46For some of the quads, plateaus emerged at the contours
in spite of our efforts to avoid them.
47We used Corps of Engineers spot elevation data for most
of the Atlantic City quad, so the comparison with the
USGS polygon area represents a comparison of Corps data
to USGS maps more than a test of our algorithm.
-------
[ 26 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
the LIDAR from NAVD88 to NGVD, and then
compared our results to the LIDAR. Table 1.1.4
shows (a) the mean error and (b) the root mean
square error of the DEM, by LIDAR elevation
increment and source of input data. Figure 1.1.9
depicts the difference in elevation estimates for
Maryland, which has the wider variety of data
quality.
Overall, wherever we relied on USGS maps, our
RMS error was approximately one-half the contour
interval. In those areas where the USGS maps had
a contour interval of 2 meters or better, the mean
error was usually less than 1 foot (30 cm). Note,
however, the tendency for the DEM to
overestimate the elevations of the lowest land
while underestimating the elevations of higher
ground. For example, in Maryland where we had
USGS 5-ft contours, the DEM overestimated
elevations by an average of 48 cm in the area
below 50 cm while underestimating elevations an
average of 10 cm in the area between 450 and 500
cm. This pattern occurs for two reasons. First, the
LIDAR has a random error on the order of 20 cm,
and the set of dry land locations where LIDAR
suggests an elevation of 40 cm will include cases
where the true elevation is 60 cm, but few if any
cases where the true elevation is 20 cm because
such land would be tidal wetland. Second, if land
has an elevation between 0 and 50 cm, the error of
our interpolation algorithm will assign some of this
land as between 50 and 150 cm; but by design
none of it will be assigned values below spring
high water (typically about 30 cm NGVD for these
areas).
It would be wrong to conclude, however, that our
analysis is systematically understating
vulnerability to sea level rise. We also created a
similar table (not shown) with the 50-cm
increments based on DEM elevation. That table
shows that most of our lowest DEM elevations are
less than the LIDAR elevation at that location,
while higher DEM elevations overstate the LIDAR
elevation. That pattern resulted largely from the
plateau problem (see previous discussion of Step
4). If the DEM assigns an elevation barely above
the contour, it is often underestimating an
elevation; but if it assigns an elevation barely
below the next contour, it is probably overstating
the elevation. Thus, if the DEM finds a very low
elevation, quite often the land is truly higher; but
when the land is truly very low, often the DEM
assigns a higher value. Does either tendency
dominate?
Table 1.1,4c suggests that the DEM is about as
likely to overstate as understate the amount of land
below a particular elevation. For each data source,
we calculated the cumulative elevation
48
distribution. We then took the area of land below
a particular elevation (e.g., 1 meter) as estimated
by our DEM interpolation, and then looked up the
elevation below which the LIDAR estimated the
same elevation. For example, our interpolated
DEM estimates 24.75 km (excluding tidal
wetlands) below 1 meter SHW in the part of
Maryland where USGS maps have a 1-m contour
interval, and the LIDAR shows the same amount
of land below 72 cm. Thus, the land vulnerable to
a 1-m rise according to the DEM would be
inundated by a 72-cm rise according to LIDAR.
Hence the table shows a vertical error of 28 cm.
Our analysis of the cumulative error shows that
errors offset to a large extent in Maryland, with the
vertical error generally less than Vi contour
interval, and generally less than the mean error
(except for the undocumented Kent Island map
provided by FEMA). In North Carolina, however,
the error appears to be more systematic: the
cumulative error is not substantially less than the
mean error (and in some cases is greater).
Fortunately, we now have LIDAR for all of North
Carolina, so our problems there may have no
practical importance, provided they are confined to
that state. Is Maryland alone a good test of our
method, or must one give weight to North Carolina
as well?
Considering the probable causes of the systematic
error in North Carolina, the accuracy assessment
of Maryland alone is probably more representative
of the error in the rest of the study area. Our
approach of defining a supplemental contour along
the upper boundary of tidal wetlands breaks down
in North Carolina, for three reasons. First, as we
have mentioned, the failure of available wetlands
48The cumulative vertical error in Table 1.1.4c is similar to
the difference between the two contour elevations in Table
1.1.3 and discussed in the last section.
-------
[ SECTION 1.1 27 ]
data sets to distinguish nanotidal wetlands from
nontidal wetlands in Albemarle Sound and its
tributaries led our interpolation to treat them as
ranging in elevation from just above the tides to
50-100 cm above spring high water, even though
some are at sea level. Second, several nontidal
rivers have wide floodplains consisting of nontidal
wetlands, with a bank at approximately the 2-m (or
5-ft) contour. Lacking a supplemental contour,
TopoGrid has no basis for estimating
how much below the 2-m contour those lands
might be, and hence tends to assign elevations
close to, albeit below, the 2-m contour. Finally, as
Figures 1.1.4 and 1.1.6 show, the stations for
estimating mean tide level and spring high water
are sparse.
Table 1.1.3. How well the DEM duplicated the polygons in our input data.
USGS Quad
Name
Central Park
Atlantic
City6
Port Norris
Marcus
Hook
Bethany
Middle River
South River
Ocean City
Broomes
Accomack
Irvinaton
Merry Hill
DEM p. First ^ prror Second Third
. . Elevation ^ . Contour °, . Contour % Error Contour % Error
Lowest Qf Contour po|vgo of Area DEM ofAr0a DEM ofArea
°?«\U Contour . b Area s 'l'a e Area Estimate Area Estimate
<«' (ha) (ha) (ha)
New York
New Jersey
New Jersey
Pennsylvania
Delaware
Maryland
Maryland
Maryland
Maryland
Virginia
Virginia
North
Carolina
10
5
5
10
5
2
5
5
5
5
10
10.1
4.6
5
10.1
5.1
1.25
7.3
5.1
5.8
5.1
10
399.3 428.1
164.2 132.2
202.0 209.9
-6.7 1472.2 -1.5
24.2 1011.4 -5.6
-3.8 522.2 2.6
1350.6 -1.3
146.7 11.0
107.9 0.4
69.2
885.2
54.8
162.4
416.3
84.2
123.7
471.2
87.8
1002.6
28.3
344.5
426.6
108.2
151.6
471.3
-21.2 308.3
-11.7
93.4
-52.9
-2.4
-22.2
-18.5
0.0
2211.8
96.3
444.4
505.3
228.2
1193.9
1309.9
0.3
7.9
-11.0
-5.2
-20.9
-38.2
0.5
2.1
6.56 6.666 151.7 240.8 -37.0 247.8 35.4
257.9
1412.2
117.5
606.4
391.9
607.6
1382.0
1654.6
333.2
-1.7
10.7
-0.9
0.8
16.7
17.4
0.5
13.2
8.4
Total
3184.2 3632.0 -12.3 9551.6 -1.2 8368.4
6.4
For example, the Central Park quad has 428.1 ha below the USGS 10-ft contour according to the input polygon
data, and 428.1 ha below an elevation of 10.1 feet according to the DEM. Therefore, we say that the DEM's
estimated elevation of the USGS 10-ft contour is 10.1 feet, and the vertical error of DEM's estimate of the contour
elevation is thus +0.1 feet.
b For example, area of land (other than tidal wetlands) between 0 and 10 feet in the Central Park quadrangle,
according to our DEM.
c For example, the area of land below the 10-ft contour in the Central Park quadrangle (other than tidal wetlands).
Comparing the difference between the areas of the DEM and polygons is a measure of our procedure.
d The DEM's estimate of 399.3 ha is 6.7% less than the area of the input polygons. Therefore, the error of our
area estimate is -6.7%.
8 The Atlantic City Quad is not a test of the algorithm because we had Corps of Engineers spot elevation data for
most of the quad. However, it does provide an indication of the difference between the Corps data and the USGS
maps.
-------
[ 28 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Table 1.1.4. Accuracy of DEM Results: Comparison with LIDAR
Source:
Maryland Eastern Shore
North Carolina I
Kent Island
1-m
5-ft
MD-DNR
20-ft
5 ft
2m I
Contour (cm)
60
100
152
305
610
152
200
Elevation3
A. Mean Error (Difference between DEM and LIDAR)b
50
60
26
48
102
17
58
56
100
12
18
9
74
-25
54
67
150
0
56
27
71
-67
38
53
200
4
23
54
72
-109
23
27
250
-1
-7
43
59
-155
13
19
300
-7
-9
21
37
-193
2
15
350
-8
12
9
2
-240
-2
7
400
-9
2
3
-35
-276
-4
1
450
-13
-2
-3
-59
-304
-3
-5
500
-42
-9
-10
-80
-341
2
-11
B. RMS Error (Root Mean Square Difference between LIDAR and DEM)°
50
102
38
107
160
18
113
116
100
74
59
70
151
28
92
92
150
72
83
95
146
74
99
87
200
80
41
100
135
124
100
84
250
80
37
71
110
170
100
94
300
76
52
56
91
218
91
96
350
78
57
61
82
263
84
90
400
94
49
63
84
308
77
81
450
121
59
65
98
345
76
73
500
135
71
66
119
387
86
73
C. Vertical Error (Difference in Cumulative Elevation Distributionf
50
-48
3
-21
-36
-54
36
52
100
-65
28
-1
-19
-75
38
80
150
-35
41
3
-18
-93
49
105
200
-30
35
9
-7
-106
52
109
250
-32
-3
23
-12
-110
46
130
300
-30
1
10
-11
-113
52
115
350
-29
-5
-2
-46
-111
73
67
400
-21
-5
-6
-101
-108
94
68
450
7
-14
-7
-104
-101
104
82
500
16
-16
-8
*
*
113
98
a In parts A and B, results are presented for 50-cm increments relative to NGVD29 as measured by LIDAR.
For example, the second row in each case provides results averaged over all lands with elevations
between 50 and 100 cm according to LIDAR. In part C, results are cumulative, and relative to spring high
water as estimated by the DEM interpolations. For example, the second row is based on the area of land
whose DEM interpolated elevation is less than 100 cm above SHW.
b The mean of LIDAR-DEM. For example, in parts of Maryland where USGS maps had a 5-ft contour and
LIDAR showed elevations between 100 and 150 cm, the DEM estimate was 27 cm higher than the LIDAR
value, on average. If LIDAR represents the true elevation, the mean difference represents mean error.
c Root mean square difference is calculated by taking the difference between the LIDAR and DEM
elevations at each point, squaring that value, adding all the squares and dividing by the number of data
points, then taking the square root. If the mean difference is zero, it is the same as the standard deviation.
If LIDAR represents the true elevation, this value is the root mean square error.
d A measure of the sensitivity to sea level rise of an estimate of the amount of land vulnerable to inundation.
For example, in parts of Maryland where USGS maps have a 1-m contour interval (excluding tidal
wetlands), our interpolated DEM estimates 24.75 km2 below 1 meter, while the LIDAR shows the same
amount of land below 72 cm. Assuming LIDAR to be accurate, the land vulnerable to a 1-m rise according
to the DEM would actually be inundated by a 72-cm rise. Hence the table shows a vertical error of 28 cm.
-------
[ SECTION 1.1 29 ]
Difference (meters)
Tidal Wetland
Figure 1.1.9. Elevation as estimated by LIDAR minus elevation estimated by our DEM: Eastern Shore of
Maryland.
-------
1.1.5 Maps and Results
Maps
Figures 1.1.10 to 1.1.14 show our maps using
various scales and formats. Figure 1.1.10 compares
our new maps of Maryland with the coarser-scale
maps published by Titus and Richman (2001).49
At that scale, our new maps do not appear to be a
major improvement over the previous maps—
except that that we have a smaller contour interval.
Unlike the previous effort, however, the current
study provides elevations relative to the tides. In
Figure 1.1.10, the 1-m (spring high water) contour
looks like the 1.5-m NGVD29 contour, but that
varies from place to place. Perhaps more
important, the current data provide maps at a much
larger scale. Figure 1.1.11 shows the area around
Washington, D.C.
Depending on the needs of a particular audience, it
may be useful to distinguish nontidal wetlands
from dry land rather than simply presenting
elevations. Figure 1.1.12 shows the lands along the
Delaware River between the
Delaware/Pennsylvania border and Northeast
Philadelphia. The maps show open water and tidal
wetlands as light and dark blue, respectively. For
other lands, Figure 1.1.12a depicts elevations
relative to the upper tidal wetland boundary using
a 50-cm contour interval with colors following the
spectrum from green to yellow to red. The
contours look relatively smooth outside of
Philadelphia, because we had to interpolate
between the upper tidal wetland boundary and the
USGS 10-fft contour, which is about 2 meters
above the tides. For the city itself we had 2-ft
contours. One limitation of our approach is that we
do not make use of contours below the tidal
wetlands. Both Philadelphia and Gloucester
County, New Jersey, have land below sea level
protected by dikes; it simply shows up as land less
than 50 cm above the tides in our maps.
Figure 1.1.12b is similar, except that the green-to-
red spectrum applies only to dry land; we show
nontidal wetlands using two shades of purple. The
rationale for this format is that elevation alone is
not always the best guide to risk of inundation as
sea level rises. From the perspective of many
property owners and planners, the tidal inundation
of previously dry land represents a significant loss
of property, whereas inundation of nontidal
wetlands may be viewed as less problematic.
Nontidal wetlands tend to be found well inland
from tidal waters. Because a dike runs along the
Delaware River in Gloucester County, New Jersey,
nontidal wetlands are found very close to the river,
albeit on the other side of a dike.
Figures 1.1.13 and 1.1.14 show the entire study
area using the same two formats. At this scale, one
notices that the lowest lands are mostly dry land in
Maryland and Delaware, but nontidal wetland in
North Carolina, and split evenly between the two
in New Jersey.
We are making both our maps and the underlying
data available to the public. We will provide the
maps with and without nontidal wetlands, at the
1:100,000 scale, county by county, state by state,
and a few multicounty and multistate regions. The
maps will generally show elevations above the
tidal wetland boundary, with the 50-cm contour
interval generally used in this report. However, the
county- and 1:100,000-scale maps will use a 1-m
contour interval wherever the underlying
topographic data had a 10-ft contour interval50;
where we relied on maps with a 20-ft contour
interval, we will not include those maps in
materials oriented for the general public. Both the
digital elevations and the coastal wetland maps
will be available from the authors as well.
49We added the tidal wetlands to the Titus and Richman
map to make them more comparable.
-------
[ SECTION 1.1
below 1.5 meters
1.5 - 3.5 meters
above 3.5 meters
Elevation
(Meters)
H Upland
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Tidal
Wetland
j
lj v
y
,*3
, Y T7
\ '/ 1
- \ I
\ *
\
&, 'V%J' ^
A ¦"*v Sb*. ,
\
X
e
-3L
£
r
. **
-U
Ms#
.V v W' •«.
5 ^
\V4S
V'
A
T . \
< M \
X J V
\
/ \
) \
%
f/
itf..
iv'
'fei
4J<¥
\
+4 W< *
ii
i j^5 fi
* 1
/ .
* -V
A . •
" *V >«Of. v
25
ikm
U. g
V »-
Mi -
4 •'
% JVT
<\".V v | -:
' • •
-------
[ 32 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Elevation (meters)
Tidal Wetland 0 1 2 3 4 5 6 Upland
Fiqure 1.1.11. Elevations relative to sprinq hiqh water: Washinqton, D.C., and vicinitv
-------
[ SECTION 1.1 33 ]
^ *i9E
* - \
Elevation (meters)
Upland
¦
,5
_
"
¦
0
OS
Tidal wetland
0 10
vL Tx
lr. 1 ;v
1\ 'h
Elevation (meters)
Dry Land
Figure 1.1.12. Lands close to sea level in Pennsylvania and nearby New Jersey. Map (a) shows elevations
relative to spring high water. Map (b) distinguishes dry land from nontidal wetlands, depicted in purple.
-------
[ 34 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
* ' r> *r *
/
A-J
N
J
r-
/
4^
150
^Dkm
Elevation
(Meters)
Dry Land
H Upland
3.0
2.5
20
1.0
0.5
0.0
Tidal
Wetland
N
Figure 1.1.13. Elevations relative to spring high water: New York to North Carolina.
-------
[ SECTION 1.1 35 ]
l,l .
Wifr
it '' *-t
A~r1>.
V \ VNO
Y V
\ /
\
( V
A
-------
[ 36 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Results
Tables 1.1.5 and 1.1.6 provide our estimates of the
land within 6 meters above spring high water, in
50-cm elevation increments. Although the maps
show that the distribution of elevations varies from
place to place, Table 1.1.5 shows that at the
statewide level, the amount of dry land at various
elevations is fairly uniform. Previous studies that
were forced to rely on 5-m contour intervals and
assume that the dry land below 1 meter is one-fifth
that amount, for example, appear to have made a
reasonable assumption. For the most part, the
amount of dry land within 1 meter of high water is
within 25 percent of the amount of land between 4
and 5 meters. Given the various geological
processes that cause land to form just above sea
level, it is not surprising that that area of land
within 1 meter would be slightly greater than the
area between 4 and 5 meters.
At first glance, North Carolina appears to be an
important exception to this tendency, with less
land below 50 cm than at other elevation
increments. At most of the elevations depicted,
North Carolina has 500-700 km , almost as much
as the 600-800 km for the other seven states
combined. Below 50 cm, however, North Carolina
has only approximately 100 km of dry land. Table
1.1.6 (and Figure 1.1.14) shows why: close to
2,000 km2 of nontidal wetlands. Looking at all
lands above the tides, North Carolina has about
2,000 km2 between 0 and 50 cm, 1,400 km2
between 50 and 100 cm, and 800-900 km2 for each
of the other 50-cm increments below 5 meters.
Thus, considering Tables 1.1.5 and 1.1.6 together
gives us the opposite picture as Table 1.1.5 alone:
more land between 0 and 1 meters than between 1
and 2 meters and other elevation increments.
That result, however, is probably an artifact of the
definition of tidal wetlands. As we have discussed,
the nanotidal wetlands of Albemarle and Pamlico
sounds and their tributaries are generally classified
as nontidal wetlands. These wetlands depend on
sea level, however, as much as most tidal
wetlands: their vertical accretion is in part a
function of sea level rise. The nontidal wetlands
may be vulnerable to sea level rise as well: their
irregular flooding tends to occur either from high
water levels in the sounds or because of a
combination of rainfall and the very slow drainage
that results from being barely above sea level.
Agricultural and other dry lands just above these
nontidal wetlands could become wet if the sea
rose, just as lands above tidal wetlands can be
inundated as sea level rises. Thus, it is somewhat
misleading to classify those wetlands with other
nontidal wetlands in an analysis of sea level rise.
As Table 1.1.6 shows, North Carolina is unique in
that its area of nontidal wetlands below 50 cm is
greater than the area of tidal wetlands; the
remaining states, by contrast, have about 20 times
as much tidal wetlands as nontidal wetlands below
50 cm.
Tables 1.1.5 and 1.1.6 also support previous
assessments suggesting a potential for a significant
net loss of wetlands if sea level rise accelerates.
This report focuses solely on the topographic
vulnerability of wetlands, that is, the ratio of
current tidal wetlands to the area of low land that
could potentially become inundated. Companion
studies are examining the potential for vertical
accretion and the extent to which shore protection
might thwart landward migration. From New York
to Virginia, the area of dry land within 1 meter
above the tides is only about one-fourth the current
area of tidal wetlands. North Carolina has
approximately 3,000 km of wetlands less than 50
cm above the tides, but only 700 km of dry land
within 1 meter above the tides. Figure 1.1.15
shows county-by-county variability of the ratio of
tidal wetlands to dry land within 1 meter above the
tides.51 Because 1 meter is somewhat arbitrary,
Figure 1.1.15b shows a similar ratio, but with the
area of land within one-half the tide range (instead
of 1 meter) above spring high water in the
denominator. This ratio indicates the net loss of
tidal wetlands that would occur if sea level were to
rise one-half the tide range instantaneously. (We
exclude North Carolina because the small tide
range would give us a meaninglessly large ratio.)
Equivalently, this figure shows the ratio of the
average slope immediately above spring high
water to the average slope between spring high
water and the open water. Across the region
depicted, the average ratio is about eight. That is, if
wetlands were able to migrate inland unfettered by
51 Counties that are partly along the ocean and partly along
Chesapeake Bay, Delaware Bay, or Long Island Sound are
split.
-------
[ SECTION 1.1 37 ]
shore protection, but were not able to vertically
accrete, sea level rise would eventually cause the
area of tidal wetlands to decline by 7/8.
Thus, the fate of tidal wetlands in the mid-Atlantic
is likely to depend more on their ability to accrete
vertically than to migrate inland. The potential for
wetlands to keep pace with an accelerated rise is
sea level uncertain (see Reed et al., Section 2.1 of
this report). A priority for additional research
would thus be to determine whether human
activities are impairing—and how they might be
able to enhance—the ability of wetlands to keep
pace with rising sea level.
Comparison with Comparable Studies
Two previous mapping studies funded by the EPA
assessed the amount of mid-Atlantic land
vulnerable to sea level rise. Titus and Richman
(2001) reported results only for the 1.5 and 3.5
contours, relative to NGVD29, without
distinguishing wet from dry land, for each state in
the Atlantic and Gulf coasts. Table 1.1.7 compares
our results to their results for the eight Mid-
Atlantic states. For both elevation increments, this
analysis finds more low land than the previous
effort for every state except North Carolina. In
fact, for the seven states from New York to
Virginia, our estimate of tidal wetlands alone is
greater than the previous estimate of land below
1.5 m. Because the 2001 study was largely based
on the USGS 1° (1:250,000 scale) maps, our
results are almost certainly more accurate. Our
primary reliance on 5- and 10-ft contour
intervals—as well as the coarse (30-m) cell size—
suggests that comparable (or greater)
improvements are likely whenever this assessment
can be revised using LIDAR.
Finally, Table 1.1.8 compares our results to that of
EPA's 1989 Report to Congress, which remains
the sole nationwide estimate of the land vulnerable
to a 50- or 100-cm rise in sea level (Park et al.
1989; Titus and Greene 1989). That study was
primarily designed to estimate the vulnerability to
a 2-m global rise in sea level, for which the
available elevation maps seemed adequate. The
need for an assessment of the more likely and
near-term scenarios led the authors to interpolate
elevations below the contours, primarily using
triangular irregular networks. PARK et al. included
a dynamic model of how wetlands respond to sea
level and provided land loss in 5-year increments,
based on 48 sites equally dispersed around the
nation representing 10 percent of the coastal 7.5-
minute quads. Like this effort, that study used
wetlands data to distinguish dry land and defined
elevations using the USGS 7.5 minute quads—but
the cell size was 500 meters. The Report to
Congress (Titus and Greene 1989) grouped the
sites into seven regions, so that confidence
intervals could (barely) be developed to capture
uncertainty regarding the extent to which the
sample sites were representative of the coastal
zone; the mid-Atlantic region was defined as New
York to Virginia. The authors of the Report to
Congress no longer have the intermediate results,
so our only available comparison is the aggregate
land loss for New York to Virginia. As Table 1.1.8
shows, our estimate of the land vulnerable to a 2-m
rise is about 30 percent less than the estimate52
from the Report to Congress. Our estimates of the
land vulnerable to a 50- or 100-cm rise, however,
are 50-60 percent less than those of the 1989 study.
The key difference is that our newer data suggest
that that dry land is close to uniformly distributed
53
by elevation below 5 meters, although Park et
al. found the dry land to be disproportionately
close to sea level. As the final column shows, the
Report to Congress, in effect, estimated land to be
30—40 cm lower on average than this study.
Does our downward revision for the mid-Atlantic
imply that the Report to Congress also
overestimated the nationwide loss of land
vulnerable to a 50-cm rise by a factor of three?
Probably not: only three of the regions showed
such a disproportionate amount of low land in the
1989 study. Moreover, the Report to Congress was
based on a nationwide sample of 48 sites, only 8 of
52The Report to Congress did not report a confidence
range for the regional estimates of dry land loss because
the central estimates were less than two times the standard
deviation.
530f course, our results assume linearity between
contours—but Tables 1.1.6 and 1.1.7 show elevations to
be fairly uniform from contour interval to contour interval
as well. Our areas with spot elevation data and LIDAR
also show a fairly constant pattern.
-------
[ 38 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Table 1.1.5: Area of Dry Land Close to Sea Level (km2, 50-cm elevation increments)
Elevation
above
Tidal mm r.- t t * m x/ ¦ m -iu New York
New New ^ , .. . . District of ... . . New York North . .. ..
Wetlands Pennsylvania Delaware Maryland _ . .. Virainia ,. to North
. . York Jersev Columbia to Virainia Carolina _
(m) Carolina
< 0
2.4
0.5
82
127
10.2
72
184
2.4
172
651
741
1391
1.0
81
148
11.1
54
265
1.2
177
737
626
1364
1.5
86
150
15.0
52
240
1.4
223
768
582
1350
2.0
86
125
13.4
56
265
1.4
237
785
637
1422
2.5
78
111
11.3
66
226
1.8
253
748
633
1381
3.0
71
108
11.3
69
244
1.8
332
837
572
1409
3.5
67
104
9.8
71
246
1.8
346
846
618
1464
4.0
61
100
9.2
74
231
1.8
338
816
715
1531
4.5
58
99
9.3
75
203
1.7
275
721
567
1288
5.0
52
95
9.1
73
195
1.6
253
679
412
1090
5.5
35
80
8.3
70
164
1.4
254
613
294
907
6.0
20
80
8.2
71
108
1.3
230
519
156
676
Table 1.1.6: Area of Wetlands Close to Sea Level (km
2, in 50-cm increments)
Elevation
above
tidal
Wetlands
(m)
New
York
New
Jersev
Pennsylvania
Delaware
Marvland
District of
Columbia
Virainia
New York
to Virainia
North
Carolina
New York
to North
Carolina
Tidal
Wetlands
149
980
6
357
1116
0.8
1619
4228
1272
5500
< 0
0.4
0.5
5.0
99
1.5
22.2
64
0.04
73
266
2372
2637
1.0
4.8
73
1.5
9.8
57
0.02
75
221
719
940
1.5
3.4
71
1.7
9.2
54
0.03
70
209
394
604
2.0
3.2
64
1.6
8.9
58
0.02
69
204
321
525
2.5
2.8
43
1.1
7.9
41
0.02
73
168
296
464
3.0
2.0
41
1.0
7.8
47
0.02
74
173
259
432
3.5
1.9
40
1.0
7.9
54
0.03
74
178
233
411
4.0
1.9
36
1.0
7.6
47
0.03
74
168
238
405
4.5
1.9
36
0.8
7.5
41
0.05
67
154
219
373
5.0
1.8
35
0.3
7.4
40
0.05
64
148
234
372
5.5
1.7
30
0.4
7.3
42
0.02
81
162
166
328
6.0
1.3
30
0.4
7.5
38
0.02
84
161
79
240
which were in the mid-Atlantic. Nevertheless, until
a nationwide revision of the Report to Congress is
undertaken, those needing a nationwide estimate of
land loss for a 50-cm rise would probably be better
advised to linearly interpolate the 2-m estimate
from that study rather than rely on the reported
results. Doing so yields an estimate at the lower
end of the 8,500 to 19,000 km2 range from the
Report to Congress. Alternatively, viewing our
newer results as a vertical revision, instead of
saying that a 50-cm rise could inundate (or require
shore protection for) 8,500-19,000 km2 of land, it
would seem more reasonable to suggest that this
area of land is vulnerable to a 50-100 cm rise in
sea level.
-------
[ SECTION 1.1 39 ]
~
Figures 1.1.15 Topographic Vulnerability of Tidal Wetlands in the Mid-Atlantic, (a) County-by-county
ratios of the area of tidal wetlands to the area of dry land within 1 meter above spring high water. The
figure shades polygons from our tidal wetlands data set. Small polygons are exaggerated to ensure
visibility, (b) Ratio of tidal wetlands to the area of dry land within one-half the tide range above spring
high water. Calculation of the denominator was undertaken quad by quad, using procedures similar
to the approach for calculating land within 1 meter above spring high water. The map shows county-
by-county ratios
-------
[ 40 MAPS OF LANDS CLOSE TO SEA LEVEL ALONG THE U.S. MIDDLE ATLANTIC COAST ]
Table 1.1.7: Comparison of this Study with Previous Studies (km ).
Elevation
(m)
New
Jersey
Pennsvl
District
Delaware Maryland of Virainia
Columbia
This Study (7.5-minute maps)
<1.5 277 1552 10
1.5-3.5 341 798 53
Titus and Richman (1-degree maps)
<1.5 240 1083 2.5
1.5-3.5 266 638 2.5
452
262
388
172
1737
1158
1547
806
3.2
5.9
1.5
4.0
2061
1322
969
1041
New York
To
Virainia
6092
3941
4230
2930
New York
North To
Carolina North
Carolina
5716
3559
5836
3865
11808
7500
10066
6794
Table 1.1.8. Mid-Atlantic Dry Land Potentially Inundated by Sea Level Rise: Comparison of this study with
EPA's 1989 Report to Congress
Global
Sea Level Rise
(cm)
Relative
Sea Level Rise3 EPA 1989b
(cm) (km2)
This Study
(km2)
This Study's Estimate of the
relative rise reguired to
inundate Corresponding
estimate
from EPA (1989)
50 70 2341 948 112 42
100 120 3121 1697 162 42
200 220 4587 3242 253 33
a The EPA Report to Congress assumed that relative sea level rise in the mid-Atlantic would be 20 cm more
than the global sea level rise over the period being analyzed.
b From Titus and Greene (1989) Table 5 (p. 5-26).
-------
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1.2. Interpolating Elevations: Proposed Method
for Conducting Overlay Analysis of GIS Data on
Coastal Elevations, Shore Protection, and
Wetland Accretion
By Russell Jones, Stratus Consulting Inc., and
Jue Wang, Pyramid Systems, Inc.
This section should be cited as:
Jones, R. and J. Wang. 2008. Interpolating Elevations: Proposed Method for Conducting
Overlay Analysis of GIS Data on Coastal Elevations, Shore Protection, and Wetland
Accretion. Section 1.2 in: Background Documents Supporting Climate Change Science
Program Synthesis and Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea
Level Rise, J.G. Titus and E.M. Strange (eds.). EPA 430R07004. U.S. EPA, Washington,
DC.
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[ 46 INTERPOLATING ELEVATIONS ]
1.2.1 Introduction
Section 1.1 (by Titus and Wang) of this report
and the metadata provided with the elevation
Geographic Information System (GIS) data
document the methods used to generate state-
specific GIS data sets of elevation relative to
spring high water (Jones, 2008, Jones et al.,
2008).\ Titus and Hudgens (unpublished
analysis) generated data on the likelihood of
shoreline protection. In that analysis, the authors
attempted to divide all dry land below the 20-ft
(NGVD29) contour—as well as all land within
1,000 ft of the shore regardless of elevation—
into one of four categories representing the
likelihood of shore protection: shore protection
almost certain (PC), shore protection likely (PL),
shore protection unlikely (PU), and no protection
(NP). Using these two data sets, this section
shows the methods used to quantify the area of
land close to sea level by shore by various
elevation increments and protection category.
However, because the results of the shore
protection analysis are unpublished, we report
only the elevation statistics.
Using the elevation data discussed in Section
1.1, and wetland data compiled from a
combination of the U.S. Fish and Wildlife
Service National Wetlands Inventory (NWI) data
and state-specific wetlands data, we created
summary tables, which we explain in Section
1.2.2. Those tables provide the area of land
within 50 cm elevation increments at the state
level of aggregation and are provided in the
appendix to this section.2 The versions with 0.1-
1 Titus and Wang in Section 1.1 generated the DEM data
by interpolating elevations from a variety of source data
sets for the eight states covered by this report. To make the
elevations relative to SHW, they used the National Ocean
Service's (NOS) estimated tide ranges, NOS estimated sea
level trends, and the NOS published benchmark sheets
along with National Geodetic Survey North American
Vertical Datum Conversion Utility (VERTCON) program
to convert the mean tide level (MTL) above NAVD88 to
NGVD29. See "General Approach" of Section 1.1 for a
brief overview. Jones (2007) created a revised dataset for
North Carolina.
2 Additionally, subregional and regional low and high
estimates of land area are provided in Appendices B and C,
respectively, to Section 1.3.
ft increments were used by the uncertainty
analysis described in Section 1.3.3
Our analysis (as well that of Section 2.1) had to
confront the fact that the attempt to assign a
shore protection category to all dry land close to
sea level was not entirely successful. In some
cases, the state-specific studies failed to assign
land to one of these four categories because (for
example) land use data were unavailable. This
happened particularly at the seaward boundary of
their study areas. They called these areas "not
considered" (NC).
Section 1.2.3 discusses several supplemental
analyses. Using a tide range GIS surface
generated by Titus and Wang, along with the dry
land elevation and tidal wetlands data, we
generated additional sets of tables4. Some of
these tables estimate the area of dry land within
one-half tide range above spring high water.
Assuming that tidal wetlands are within one-half
tide range below spring high water (i.e., between
mean sea level and spring high water), these
tables give us the ratio of slopes above and
below spring high water, that is, the ratio of
existing wetlands to the potential for new
wetland creation. Other tables estimate the area
of potential tidal wetland loss by estimating the
portion of existing tidal wetlands that would fall
below mean sea level if sea level were to rise a
particular magnitude, with and without wetland
accretion.
1.2.2. Estimating Land Area by
Elevation Increment and Protection
Category
We estimated the land area by protection
category using several steps. First, to summarize
the protection data by elevation, it was necessary
3. Horizontal and vertical accuracy issues are addressed in
Section 1.3. An additional discussion on reporting data at
0.1 ft increments is provided here. The increments used
imperial rather than metric units because the interpolation
is facilitated when the contour interval (mostly in imperial
units as well) are an integer multiple of the increment.
4These tables are not provided as the likelihood of
shoreline protection data from which they were generated
are based on an unpublished analysis.
-------
[ SECTION 1.2 47 ]
to first convert the shore protection GIS data
from a vector format (i.e., polygons) into a raster
(or grid) format to match the digital elevation
model (DEM) data. As part of this step, we
developed a procedure to lessen the amount of
land classified as "not considered" (which would
otherwise be enhanced by the vector-to-raster
conversion process). Once this was done, we
were able to quantify the amount of land at
specific elevations by protection category. To
improve our elevation-specific area estimates,
we tailored our approach to the accuracy of the
source data—interpolating lower accuracy data
and using the area estimates directly from the
DEM for those with higher accuracies. We then
provided summary results in tables "rolled up"
by different elevations. The appendix to this
section provides county-by-county results for the
analysis we describe in this section. Section 1.3
provides additional information about variations
in data quality and the associated appendices also
provides results, by state, subregion, and region.
Converting shore protection polygons to
grid
General approach
In converting vector data into grid format,
several considerations need to be taken into
account. Spatially, the size of the raster cell
generated should be based on the estimated
accuracy or minimum mapping unit, as well as
whether the output raster data will be combined
with other data sets. We generated our raster
based on a 30-m cell size to match our DEM
data. In addition, this cell size was not
inappropriate given the source of the
information. Similarly, because the cell
boundaries will inevitably cross the vector
polygons (cell boundaries rarely coincide exactly
to vector polygon outlines of the input data),
different approaches can be taken to transfer the
attributes of a particular polygon to the output
raster cells. The attribute assignment can be
based on the centroid of the cell (i.e., the
attribute of the polygon is assigned to the raster
cell whose center it encapsulates), on the
polygon covering the majority of the cell (or the
combined area of multiple polygons with the
same attribute), or through attribute priority (i.e.,
if any portion of the polygon has a certain
attribute, the cell is assigned that attribute). We
used a combination of approaches in our
analysis. In our initial conversion, we used a
centroid approach. In subsequent reclassification,
we assigned attributes based on attribute values
(i.e., priority approach), and attributed remaining
cells based on proximity of neighboring cells.
The specific methods used are described below.
Approach for avoiding the "not considered"
designation
One of our main goals was to limit the amount of
land classified as "not considered." The original
shapefile dataset had numerous narrow polygons
along the shore classified as "not considered."
Usually, those polygons were not visible in the
county-scale maps that county officials and the
authors had closely examined, which the state-
specific chapters of this report display. Usually,
the polygons of "not considered" resulted
because the planning data used in the state-
specific analyses did not extend all the way out
to the wetland/dryland boundary defined by the
wetlands data set we were using. This occurred
for at least two reasons: In some cases, the
planning data were more precise than the old
NWI wetlands data we used; in other cases, the
planning study had used very coarse land use
data. Whenever the land use data extended
seaward of the wetland boundary, the use of
wetlands data as a "mask" resolved the data
conflict. But if the land use data did not extend
all the way to the wetlands or open water, we
were left with dry land with no protection
category (i.e., not considered).
A related problem was that the shore protection
polygons created by the state-specific studies
sometimes labeled lands as "wetlands" even
though that study ostensibly categorized dry land
by likelihood of shore protection and relied on a
wetlands data set to define wetlands. In several
cases—particularly the Hampton Roads area of
Virginia and some Maryland counties, local data
defined wetlands in areas that the statewide data
set classified as being dry. The study authors
wanted the maps to show those areas as
wetlands—a reasonable objective given that the
local planning data that form the basis of the
-------
[ 48 INTERPOLATING ELEVATIONS ]
studies treated it as wetlands. But we wanted our
results to be consistent with the Section 1.1
estimates of dry land and wetlands that relied on
the wetlands data set rather than local planning
data.
We converted the shapefile planning data
according to the general process shown in
Figure 1.2.1. Figure 1.2.2 shows an example of
the process using GIS data. Specifically, we
recoded any polygons designated as a wetland in
the source protection data as protection unlikely.
We then clipped the data to the extent of the
study area boundary and excluded any polygons
that overlapped with tidal wetland or tidal open
water as determined by the state-specific
wetlands layers. Additionally, we coded any
cells without an attribute as NC. We then
converted the protection data from a vector (i.e.,
polygon) format to raster (grid-based) format
with a cell size of 30 meters to match the
resolution of the elevation data.5 Attributes were
assigned to the cells based on whichever polygon
from the source vector data covered the centroid
of the output raster cell. This approach was
preferable over dominant category, because in
some cases there are narrow environmental
buffers along the shore. The buffers are PL or
PU along an area where the rest of the land is
PC. The buffers are too narrow to be the
dominant shore protection category in a cell.
Thus, using dominant category would create a
downward bias for that category, while picking
the centroid would be expected to yield area
estimates similar to the actual area estimate.
We then subset the raster layer to elevations less
than 20 feet and converted the NC cells back into
a vector format. The result was a vector polygon
layer of NC cells. The resulting polygons were
then overlaid with the original polygon vector
shoreline protection data, and the NC polygons
were assigned the same attribute as any
overlapping polygons. Only individual 30-m
Input Vector Shoreline
Protection Scenario
(polygons)
1
r
Reclass polygons originally coded as
wetland to "PU"
1
Clip data to study area and mask by
tidal wetland or open water from
wetland data set
1
r
Code cells without a shoreline
protection code to "NC"
Convert protection data from vector to
raster (based on centroid)
Select cells classified as "NC" and
subset to elevation <= 20 ft MSHW
Convert "NC" cells to vector format
(polygons)
Overlay "NC" polygons with original
shoreline protection data
Convert back to raster format and
attribute with overlapping polygon
based on priority
Attribute remaining "NC" cells with
attribute of cell within 50 meters of cell
centroid
Merge reclassed cell into original
raster shoreline protection data
Output Raster Shoreline
Protection Scenario
(reclassed)
Figure 1.2.1. Approach used to reclassify not-
considered shoreline protection scenario cells.
5. The conversion from vector to raster was conducted
using ArcGIS Spatial Analyst extension (ESRI, 2006).
-------
[ SECTION 1.2 49 ]
A
B
PU
NC
PL
Original shoreline protection polygons (vector) Original shoreline protection cells (raster)
D
NC raster cells converted to polygons (vector) Final reclassed shoreline protection cells (raster)
and overlaid with original shoreline protection
polygons
Figure 1.2.2. Graphical Representation Showing How Original Shoreline Protection Scenario
Data in Vector Format was Reclassified to Reduce the Amount of "Not Considered" (NC)
Lands.
cells of NC were recoded. Where multiple
polygons overlapped with the NC cells, and none
crossed the cell centroid, attribute assignment
was based on the following priority: NP, PU, PL,
and PC. We used this priority rule instead of
picking the category that accounted for the
greatest portion of the cell because such cells are
generally along the water or wetlands (and
assumed to be water or wetlands in the land use
data set that gave rise to the shore protection
classifications). If any of the overlapping cells
did not contain any of these categories, the cell
remained NC. Finally, any remaining NC cells
were assigned the attribute of any other non-NC
cells within a maximum distance of 50 meters
(centroid to centroid).6 All other NC cells
remained NC. Finally, we merged the
6. Given the cell size of 30 meters, this effectively means
that NC cells would be attributed the same as any adjacent
(including cells diagonal to the NC cell) non-NC cell. Note
also the cell shown by "z" (panel D) remained NC because
it fell entirely within tidal wetlands.
-------
[ 50 INTERPOLATING ELEVATIONS ]
reclassified NC layer with the original raster
version of the protection data.
Estimating area of land at specific
elevations by shore protection category
Combining elevation, protection, wetland,
quadrangle, and county data
Our first step was to segment the final DEM data
(see Section 1.1) by the source data from which
they were derived.7 We needed to do this for two
reasons. First, the interpolations (discussed in the
following section) depended on contour interval.
Second, one of the expected uses of our output
was the creation of high and low estimates; and
the uncertainty would be a function of the data
quality (see Section 1.3).
Using the same resolution and projection as the
elevation data, we generated raster data sets from
the following vector GIS layers: USGS 1:24K
quadrangles, county boundaries, and source data
extent polygons, as well as a nontidal open water
(NO) and nontidal wetlands (NW) layer
generated from wetlands data from each state
data set. We then combined these raster layers
with the elevation data and reclassified shore
protection data to generate a composite raster
layer with attributes from each source data set
(e.g., quadrangle, county, wetland type, source
data name, elevation, and shoreline protection
scenario). We calculated a final protection
scenario attribute field from the shore protection
category and NO/NW wetlands data, with
priority assigned to the wetlands data. The
resulting protection scenario field contained one
of the following categories: NO, NW, PC, PL,
PU, NP, orNC.
Areas with source elevations of 1-m contours or
worse
As noted in Section 1.1, the ESRI GRID
extension function TOPOGRID (ESRI, 2006)
that was used to interpolate contours into a DEM
was spatially biased toward each input contour.
The resultant DEM data therefore contained
"plateaus" on either side of the source contours.
Given our objective of estimating the area of
land within elevation increments of 50 cm, this
was not a significant problem for our source data
sets with contour intervals of 2 feet (60 cm) or
better. But it presented a significant bias in the
lower accuracy data sets. As in Section 1.1, we
corrected for this distortion in the lower accuracy
data sets by redistributing the land area evenly
into 0.1-ft elevation bins between each source
contour elevation interval (e.g., for each 5 feet
for data with a 5-ft contour interval) for each
combination of quadrangle, county, and
protection scenario.8 For the first contour, the
area between SHW and the first contour (e.g., 5-
ft NGVD) was used. We calculated the SHW
value (relative to the NGVD29 vertical datum)
by overlaying the SHW surface generated by
Titus and Wang9 with the quadrangle/county grid
and taking the average for all cells over each
quadrangle/county combination.
The process used for the lower accuracy source
areas is summarized in the following steps with
the tabular data shown in Figure 1.2.3 (for USGS
24K quadrangles in Sussex County, Delaware,
under the PC scenario):
8. This approach effectively generates a linear
interpolation of land area. Lacking site-specific
topographic information, the exact profile of the landscape
cannot be determined. Therefore, this linear interpolation
represents a conservative approach and differences in
coastal profiles at any specific locality could be thought to
average out over the broad areas where this was applied.
Certainly the reader may question any quantification of
land at the 0.1-ft increment; however, to assess
vulnerability of lands to inundation by small rates of SLR
over different time periods, the increment chosen is
necessary. Accuracy issues are discussed in Annex 3.
7. USGS data varied by 24K quadrangle, whereas other
data sets were provided by county or other boundary.
9. The SHW surface was derived by Titus and Wang
through interpolation of local tide gage point data that was
referenced to the NVGD29 vertical datum. See Section 1.1
for full processing details.
-------
[ SECTION 1.2 51 ]
1. Sum the area of land between SHW and
source contour interval or between
successive contour intervals (SHW Table in
Figure 1.2.3).
2. Determine the number of 0.1 -ft elevation
bins between the SITW/first contour or
successive contours.
3. Divide the sum in #1 by the number of bins
in #2.
4. Assign each 0.1 -ft bin the output value from
#3 (NGVD29 Area Distribution Table in
Figure 1.2.3).
For example, using the Assawoman Bay
quadrangle in Sussex County, Delaware, as an
example (highlighted in Figure 1.2.3), the source
data is 5-ft USGS, the SHW value is 2.7-ft
NGVD29, and the total area between SHW and
the 5-ft contour under the PC scenario is 370.53
hectares (ha). The land area was redistributed as
follows:
1. Sum of land between 2.7 and 5 feet (NGVD)
= 370.53 ha
2. Number of 0.1 ft bins: round (5—2.7) / 0.1)
= 23
3. Land area reported in each 0.1 ft bin: 370.53
/ 23 = 26.1 ha
SHW Table
NGVD29 Area
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Figure 1.2.3. Example Tabular Summary Output of Land Elevation for Shore Protection Certain (PC)
Scenario for USGS 24K Quadrangles in Sussex County, Delaware. SHW Table shows land area (in
hectares) of PC between SHW relative to NGVD29 vertical datum and the 5-ft USGS contour.
NGVD29 Area Distribution Table shows how land area in SHW Table was distributed evenly into 0.1-
ft elevation bins. The SHW Area Distribution Table shows the re-distributed NGVD29 Table data
adjusted relative to SHW elevations. The highlighted row pertains to an example in the text.
-------
[ 52 INTERPOLATING ELEVATIONS ]
Figure 1.2.3 for the Assawoman Bay quadrangle
shows that 16.1 ha was input into each 0.1 -ft bin
between 2.7 feet (SHW) and 5 feet. The same
procedure was used for each successive 5-ft
contour.
Areas with source elevations better than a 1-m
contour
For the higher accuracy data sources, the land
area was summarized by larger elevation
increments (e.g., 50 cm and 1 foot) and output
directly from the DEM without any reallocation.
Final output
We subsequently output the land areas by
elevation bin into individual Excel workbooks
for each elevation data source. Individual sheets
within the workbooks were divided by protection
scenario and contained the area of land (in
hectares) within each elevation increment—50
cm and 1 foot for both low and higher resolution
data sets and 0.1 -ft increments where the source
data was 1-m contour or worse.10 Area estimates
were reported from 0 to 20 feet for English unit
tables and from 0 to 7 meters for metric tables. A
second set of Excel workbooks was generated
relative to SHW by subtracting the SHW-
NGVD29 elevation bin reported from each
quadrangle/county record within the
spreadsheets. An example of the output is shown
in the SHW Area Distribution Table in Figure
1.2.3. Therefore, relative to SHW, the 16.1-ha
bins are distributed between 0 and 2.3 feet (after
conversion from 2.7 to 5.0 feet relative to
NGVD29).
Finally, we added two additional sheets to each
Excel workbook: "All Land" and "Dry Land."
The first worksheet summarized all the other
shoreline protection scenario worksheets with the
exception of the NO sheet, and the "Dry Land"
worksheet represented the summary of all
worksheets except NO and NW.
10. In subsequent elevation rollups, to make the data
compatible with the lower accuracy data, we divide the
area of 1-fit increments evenly into 0.1-ft elevation bins.
This differs from the method used for the lower accuracy
data in that the redistribution occurred at 1-ft increments
instead of over the entire contour interval.
Once the individual source, quadrangle, county,
and protection scenario tables were generated,
we were able to summarize total areas for each
scenario or groups of scenarios by various
groupings, including state, county, or various
region (e.g., Chesapeake Bay) where each
quadrangle/county combination could be
assigned to the appropriate region.
In addition to the tables just described, we also
generated land area summaries for each shoreline
protection scenario by elevation taking into
account the uncertainty associated with different
source data sets. This was accomplished by
creating a lookup table of the root mean squared
error (RMSE) associated with each source data
set. By reporting the RMSE by individual
quadrangle, county, and source combination, we
were able to make low and high estimates of land
area similar to the tables generated using the
central estimate. The methods used to generate
the uncertainty tables are in Section 1.3.
1.2.3. Other Products—
Summarizing Land Area Vulnerable
to Inundation
General approach
In addition to the summaries described, we
generated another set of tables showing the area
of tidal wetlands at risk of inundation from SLR
and area of potentially new wetlands resulting
from inundation of lands above SHW under
alternative SLR and protection scenarios.11 To
derive this information we used the summary
statistics tables described and combined them
with lookup tables we developed. The lookup
tables were created for dry land and tidal
wetlands (TW) and provide the following
information: the mean (arithmetic) of full tide
range, the mean of the reciprocal of the tide
range (harmonic mean), the mean SLR rate, the
dominant accretion code, and the percentage of
wetland area with a specific accretion code of the
total wetlands for each quadrangle/county
combination. The sections that follow describe
11 These tables are not provided because the likelihood of
shoreline protection data from which they were generated
are based on an unpublished analysis.
-------
[ SECTION 1.2 53 ]
the methods we used to calculate the values in
the lookup tables.
Calculating average and average reciprocal
spring tide range values
To derive the mean spring tide range (STR) for
each quadrangle/county combination for the dry
land, we overlaid a raster layer of the
combination of quadrangle and county with a
raster surface of spring tide range developed
from interpolation of tide gauge data.12 We then
calculated the average STR using the ESRI
GRID extension function "ZONALSTATS"
(ESRI, 2006), which calculates the mean of the
values of all raster cells in the STR surface that
spatially coincide with the same
quadrangle/county combination. Similarly, we
calculated the reciprocal mean of STR by first
generating the raster layer of the inverse of the
STR surface (1/STR surface) and then
calculating the mean using the inverse layer as
an input into the ZONALSTATS function.
To calculate the average STR and average
reciprocal STR for the tidal wetlands, we first
overlaid the tidal wetland layer for each state13
with a GIS raster layer of accretion data
developed by Titus, Jones, and Streeter (in
Section 2.2) (based on a science panel
assessment and hand-annotated maps delineated
by Reed et al. [in Section 2.1]). We then
calculated the average STR values (mean and
reciprocal mean) using the same procedure that
was followed for the dry land data, but limiting
12. Titus and Wang (Section 1.1) generated vertical
elevations for the tide points using the National Ocean
Service's (NOS) estimated tide ranges, NOS estimated sea
level trends, and the NOS published benchmark sheets
along with National Geodetic Survey North American
Vertical Datum Conversion Utility (VERTCON) program
to convert the mean tide level (MTL) above NAVD88 to
NGVD29.
13. For all states except Pennsylvania, the wetland layer
that was generated by Titus and Wang was used. Titus and
Wang did not include mudflats in the tidal wetlands
classification for Pennsylvania. Because mudflats
represent a significant portion of tidal wetlands in
Pennsylvania, we extracted mudflats from the NWI source
data and added them to the final Pennsylvania wetlands
layer.
our averages to only the wetland/accretion code
combination within a quadrangle/county instead
of using the entire quadrangle/county that was
used in the dry land analysis.
Calculating the dominant accretion code for
tidal wetlands
Because the minimum mapping unit of analysis
(minimum unit of analysis) for dry land was the
quadrangle/county combination, we needed to
have a single accretion code for each
quadrangle/county combination. In addition,
because the accretion potential defined by Reed
et al. (2008) was categorical rather than
representing an average, we needed to use the
dominant accretion code instead of taking an
average. To determine the dominant accretion
code for wetlands within a quadrangle/county,
we first summed the area of tidal wetlands by
accretion code within a quadrangle/county and
divided it by the total area of tidal wetlands for
all accretion codes within a quadrangle/county.
The percentage of each tidal wetlands/accretion
code of the total wetlands within the
quadrangle/county was calculated as % TW
accretion = (Area specific TW accretion total
TW area) * 100.
The accretion code that accounted for the most
tidal wetlands was classified as the dominant
code.
Calculating the accretion code for dry land
To determine the accretion code for each
quadrangle/county combination for dry land, we
overlaid the raster accretion layer with the
quadrangle/county raster layer and assigned the
accretion code based on whichever accretion
code covered the majority of the
quadrangle/county. Where the accretion layer did
not extend far enough inland to cover all nontidal
lands being evaluated, the accretion code nearest
the quadrangle/county dry land being evaluated
was used. Figure 1.2.4 shows an example of the
output in the lookup tables (dry land and tidal
wetland) for Delaware. This table was then used
with the summary elevation statistics tables to
roll up elevations at various increments to
estimate the loss of tidal wetlands as well as the
-------
[ 54 INTERPOLATING ELEVATIONS ]
generation of new wetlands from inundation of
dry lands (these tables are not provided because
the likelihood of shoreline protection data from
which this was generated is based on an
unpublished analysis).
Generating tabular summaries of potential
wetland creation and loss
After we generated the lookup tables, we were
able to summarize the elevation data into tables
that provide information on the potential tidal
wetland creation and loss. For example, using
the elevation by protection scenario data along
with the tide range data in the lookup table, we
were able to calculate the area of tidal wetlands
and the area of dry land within 1 meter or one-
half tide range above spring high water by
protection scenario (results are part of an
ongoing analysis). Similarly, we calculated the
amount of land available for wetland migration
by shore protection likelihood by looking at the
amount of land between mean sea level and
spring high water if the sea level rises 1 meter
(results are part of ongoing analysis).
Additionally, other modifications included
summarizing the area of wetlands below a
particular elevation assuming uniform elevation
distribution, and subdividing quadrangle-specific
estimates by dominant accretion code that was
assigned to both wetlands and drylands.
References
ESRI. 2006. ArcGIS Arclnfo Workstation GRID
Extension and ArcGIS Desktop Spatial Analyst
Extension, v. 9.1 and 9.2. Environmental
Systems Research Institute, Inc., Redlands, CA.
Jones, R. 2007. Accuracy Assessment of EPA
Digital Elevation Model Results. Memorandum
and attached spreadsheets prepared for the U.S.
EPA under Work Assignment 409 of EPA
Contract #68-W-02-027.
Jones, R., J. Titus, and J. Wang. 2008. Metadata
for Elevations of Lands Close to Sea Level in the
Middle Atlantic Region of the United States.
Metadata accompanying Digital Elevation Model
data set. Distributed with the elevation data.
-------
[ SECTION 1 .2 55
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County
Accretion
TW Ha
Total TW Ha % Accretion of Total
Arith Mean STR
Harmonic Mean
Mean SLR Rate
23
Mispillion
Sussex
2
2136.87
2136.87
100
171.53
0.0058
3.21
:
24
Newark East
New Castle
8
225.36
225.36
100
176.8
0.0057
3.21
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Rehoboth
Sussex
2
764.37
764.37
100
143.27
0.0070
3.21:
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26
Saint Georges
New Castle
2
42.66
42.66
100
184.02
0.0054
3.21
27
Seaford East
Sussex
8 90.09
90.09
100
88.21
0.0113
3.21
III
28
Seaford West
Sussex
8 0.99
0.99
100
88.82
0.0113
3.21
iii
29
Selbyville
Sussex
2
17.46
17.46
100
15
0.0667
3.21
30
Sharptown
Sussex
8
561.06
561.06
100
88.21
0.0113
3.21
31
Smyrna
Kent
0
913.05
1579.77
57.8
196.43
0.0051
3.21
32
Smyrna
Kent
2
666.72
1579.77
42.2
196.43
0.0051
3.21
33
Smyrna
New Castle
2
864.18
864.18
100
194.47
0.0051
3.21
3 4
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New Castle
2
3815.37
3815.37
100
193.74
0.0052
3.21
III:
35
Wilmington_S
New Castle
2
254.43
511.02
49.79
176.24
0.0057
3.21
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County
Accretion Arith Mean STR Harmonic Mean STR
Mean SLR Rate
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Georgetown
Sussex
8
157.78
0.0063
3.21
3
Greenwood
Sussex
8
174.77
0.0057
3.21
A
Hickman
Sussex
8
147.98
0.0075
3.21
5
Laurel
Sussex
8
104.05
0.0098
3.21
6
Marcus Hook
New Castle
8
181.17
0.0055
3.21
7
Marydel
Kent
8
188.28
0.0053
3.21
8
Newark East
New Castle
8
177.75
0.0056
3.21
9
Penns Grove
New Castle
8
180.53
0.0055
3.21
10
Seaford East
Sussex
8
149.74
0.007
3.21
11
Seaford West
Sussex
8
100
0.0104
3.21
12
Sharptown
Sussex
8
87.34
0.0115
3.21
13
Trap Pond
Sussex
8
117.82
0.0085
3.21
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New Castle
8
178.8
0.0056
3.21
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Figure 1.2.4. Example of Lookup Tables. Top table: tidal wetland (TW) areas by
quadrangle/county/accretion code, total TW for quadrangle/county, percentage of accretion-specific
area to total, arithmetic mean of STR, harmonic mean (mean of reciprocal) of STR, and mean SLR
rate. Bottom table: dominant accretion code, and arithmetic and harmonic STR means and mean of
SLR rate.
-------
Section 1.2 Appendix
Area of Land Close to Sea Level, by State
By James G. Titus, U.S. Environmental Protection Agency
Russell Jones, Stratus Consulting Inc.
Richard Streeter, Stratus Consulting Inc.
-------
[ SECTION 1.2 57 ]
Table A1. New York (square kilometers)
Meters above Spring High Water
County
0.5 1.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Dry Land, by half meter elevation increment3
Bronx
2.3
2.3
2.3
2.6
2.8
2.8
2.8
2.8
2.8
1.4
Brooklyn
7.4
6.0
6.0
6.7
9.2
9.2
8.4
5.4
5.4
4.9
Manhattan
1.6
1.6
1.6
1.6
1.7
1.7
1.7
1.7
1.7
1.7
Nassau
13.2
17.8
21.2
21.2
13.3
8.8
8.8
8.6
8.1
7.4
Queens
13.2
8.9
8.9
9.6
9.3
9.3
7.4
5.0
5.0
3.1
Staten Island
5.7
5.7
5.7
4.9
2.7
2.7
2.7
2.7
2.7
2.4
Suffolk
36.8
37.0
38.0
37.6
37.6
34.3
33.9
33.4
30.3
29.5
Westchester
2.1
2.1
2.1
2.2
1.9
1.8
1.8
1.8
1.8
1.3
Ellis & Liberty Islands
0.04
0.04
0.04
0.03
0.00
0.00
0.00
0.00
0.00
0.00
Statewide
82.4
81.5
85.9
86.4
78.5
70.6
67.5
61.4
57.8
51.7
Wetlands
Tidal
¦Nontidal Wetlands, by half meter elevation increment
Brooklyn
3.5
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Nassau
43.4
0.3
0.3
0.3
0.4
0.3
0.3
0.3
0.3
0.3
0.3
Queens
7.6
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.0
0.0
0.0
Staten Island
5.4
0.3
0.3
0.3
0.3
0.1
0.1
0.1
0.1
0.1
0.1
Suffolk
82.3
4.1
4.0
2.5
2.4
2.3
1.5
1.5
1.4
1.4
1.3
Otherb
6.9
0.06
0.06
0.06
0.05
0.05
0.04
0.04
0.04
0.04
0.05
Statewide
149.1
5.0
4.8
3.4
3.2
2.8
2.0
1.9
1.9
1.9
1.8
Cumulative (total) amount of land below a given elevation0
Dry Land
82
164
250
336
415
485
553
614
672
724
Nontidal Wetlands
5
10
13
16
19
21
23
25
27
29
All Land
149
236
323
412
502
583
655
725
788
848
901
a For example, Bronx has 2.3 square kilometers of dry land between 0.5 and 1.0 meters above spring high
water.
b Includes Bronx, Dutchess, Manhattan, Orange, Putnam, Rockland, and Westchester counties.
c For example, New York State has 164 square kilometers of dry land less than 1 meter above spring high
water.
Table A2. New York jurisdictions not included in shore protection study (hectares)
Meters above Spring High Water
County
0.5
1.0
1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Tidal Nontidal Wetlands, by half meter elevation increment
Dutchess
7.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Orange
24.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Putnam
126.6
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
Rockland
228.6
1.5
1.5
1.5
1.5
0.9
0.6
0.6
0.6
0.6
0.6
Note: The analysis found no dry land below 5 meters for these jurisdictions.
-------
[ 58 AREA OF LAND CLOSE TO SEA LEVEL, BY STATE ]
Table A3. New Jersey (square kilometers)
Meters above Spring High Water
County
0.5
1.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Dry Land, by half meter elevation increment3
Atlantic
8.1
13.7
14.2
10.9
9.3
8.1
7.8
8.1
7.8
7.8
Bergen
11.4
11.4
11.4
7.5
2.2
2.1
2.1
2.1
2.1
2.1
Burlington
4.6
4.6
4.6
4.5
5.6
5.9
5.9
5.9
5.9
7.3
Cape May
16.2
23.0
20.0
16.3
23.0
21.8
20.6
20.7
19.6
18.1
Cumberland
11.8
10.0
10.0
10.1
11.1
11.1
10.6
9.9
9.9
9.6
Gloucester
6.8
6.7
6.7
6.6
6.0
6.0
6.0
6.0
6.0
5.8
Hudson
11.9
11.9
11.9
9.4
3.5
3.5
3.5
3.5
3.5
3.0
Middlesex
6.5
6.5
6.5
5.7
5.2
5.2
5.2
5.2
5.2
4.9
Monmouth
7.3
7.8
9.9
10.4
9.2
9.0
8.1
7.3
8.2
8.0
Ocean
10.1
22.4
25.2
16.6
12.7
12.9
12.3
11.1
10.0
9.0
Salem
20.0
17.3
17.3
16.7
14.2
14.2
13.7
12.1
12.1
11.8
Otherb
12.4
12.4
12.4
10.8
8.5
8.5
8.5
8.5
8.5
7.7
Statewide
127.2
148.0
150.2
125.5
110.5
108.4
104.5
100.5
98.8
95.0
Wetlands
Tidal
Nontidal Wetlands, by half meter elevation increment-
Atlantic
204.0
14.3
9.1
9.1
9.1
8.7
8.6
8.5
8.4
8.3
8.3
Burlington
42.8
7.6
7.5
7.3
7.3
4.7
4.4
4.4
4.4
4.4
4.6
Cape May
201.4
20.5
15.4
14.9
13.7
10.1
9.8
9.5
7.2
7.0
6.6
Cumberland
212.6
18.1
14.1
14.1
12.0
7.2
7.2
6.8
6.3
6.3
6.1
Gloucester
18.0
6.5
6.3
6.3
5.3
1.3
1.3
1.3
1.3
1.3
1.3
Ocean
124.8
7.9
9.2
8.3
7.4
6.6
5.2
4.7
4.3
4.0
3.8
Salem
110.1
21.8
8.5
8.5
7.5
3.1
3.1
3.0
2.7
2.7
2.7
Other0
66.7
2.8
2.5
2.5
2.1
1.5
1.4
1.4
1.5
1.6
1.5
Statewide
980.4
99.5
72.6
70.9
64.4
43.2
41.0
39.8
36.0
35.5
35.0
Cumulative (total) amount of land below a given elevation0
Dry Land
127
275
425
551
661
770
874
975
1073
1169
Nontidal Wetlands
99
172
243
307
351
392
431
467
503
538
All Land
980
1207
1428
1649
1839
1992
2142
2286
2422
2557
2687
a For example, Atlantic County has 13.7 square kilometers of dry land between 0.5 and 1.0 meters above
spring high water.
b Includes Camden, Essex, Mercer, Passaic, Union, and Somerset above 4.5m.
c Includes Camden, Essex, Mercer, Passaic, Union, Somerset above 4.5m, Bergen, Hudson, Middlesex,
and Monmouth.
d For example, New Jersey has 275 square kilometers of dry land less than 1 meter above spring high
water.
-------
[ SECTION 1.2 59 ]
Table A4. New Jersey jurisdictions not included in shore protection study (hectares)
Meters above Spring High Water
County
0.5
1.0
1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment
Mercer1
4.5
4.5
4.5 4.5 4.5 4.5 4.5 4.5
3.5
0.3
Passaic
11.7
11.7
11.7 14.4 17.7 17.7 17.7 17.7
17.7
18.1
Somerset
0.0
0.0
o
o
o
o
o
o
o
o
o
o
o
o
0.0
2.9
Wetlands Tidal
-
Nontidal Wetlands, by half meter elevation increment-
Mercer3 178
0.4
0.4
o
4^
o
4^
O
4^
O
4^
O
4^
O
4^
0.3
0.0
Passaic 0
1.2
1.2
1.2 0.7 0.1 0.1 0.1 0.1
0.1
0.3
Somerset 0
0.0
0.0
O
o
o
o
o
o
o
o
o
o
o
o
0.0
0.6
a The "not considered"
category includes Mercer County because we calculated these statistics before the
Mercer County results had been incorporated into our data set.
Table A5. Pennsylvania (square kilometers)
Meters above Spring High Water
County
0.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment3
Bucks
3.2
CD
CO
CD
CO
CD
CO
CD
CO
CD
CO
CO
CO
C\J
CO
3.5
3.4
Delaware
4.4
CO
CO
CO
CO
CO
CO
1.3
1.2
Philadelphia
4.9°
3.5 7.2 6.5 6.4 6.4 5.0 4.3
4.6
4.4
Statewide
12.6
11.1 15.0 13.4 11.3 11.3 9.8 9.2
9.3
9.1
Wetlands
Tidal -¦
Nontidal Wetlands, by half meter elevation increment-
Bucks
1.9
0.7
0.7 0.8 0.9 0.9 0.9 0.9 0.9
0.7
0.3
Delaware
0.6
0.6
o
o
o
o
o
o
o
o
o
CD
o
CD
O
0.0
0.0
Philadelphia
3.6
0.5C
0.2 0.3 0.3 0.2 0.1 0.1 0.1
0.1
0.0
Statewide
6.1
1.9
1.5 1.7 1.6 1.1 1.0 1.0 1.0
0.8
0.3
Cumulative (total) amount of land below a given elevationd
Dry Land
13
24 39 52 63 75 85 94
103
112
Nontidal Wetlands
2
3 5 7 8 9 10 11
11
12
All Land
6
21
33 50 65 77 89 100 110
121
130
a For example, Philadelphia has 3.5 square kilometers of dry land between 0.5 and 1.0 meters above spring
high water.
bThis value includes 2.4 square kilometers of dry land below spring high water in Philadelphia, of which
0.87, 0.054, and 0.005 are at least 1, 2, and 3 meters below spring high water, respectively. Most of this
land is near Philadelphia International airport.
cThis value includes 39 hectares below spring high water, of which 3.8 are at least 1 meter below spring
high water. Most of this land is near Philadelphia International airport.
d For example, Pennsylvania has 24 square kilometers of dry land less than 1 meter above spring high
water.
-------
[ 60 AREA OF LAND CLOSE TO SEA LEVEL, BY STATE ]
Table A6. Delaware (square kilometers)
Meters above Spring High Water
County
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment3
Kent
19.2
13.0
13.0
16.2
20.5
20.5
22.0
24.3
24.3
22.2
New Castle
15.4
9.0
9.0
9.6
11.1
11.1
11.3
11.3
11.3
10.7
Sussex: Chesapeake Bay
1.1
1.3
1.6
1.6
2.3
3.4
3.4
4.6
5.7
5.7
Sussex: Delaware Bay
13.7
10.9
10.7
10.8
11.8
11.7
11.6
10.2
10.1
10.2
Sussex: Atlantic Coast
22.7
19.9
18.1
18.1
20.7
22.3
22.3
23.5
24.0
24.0
Statewide
72.2
53.9
52.4
56.3
66.4
68.9
70.5
73.8
75.5
72.9
Wetlands
Tidal
Nontidal Wetlands, by half meter elevation increment
Kent
168.7
9.6
4.3
4.3
4.0
3.1
3.1
3.2
3.3
3.3
3.2
New Castle
73.5
3.5
0.8
0.8
0.8
0.9
0.9
0.8
0.7
0.7
0.7
Sussex: Chesapeake Bay
6.6
1.4
0.9
0.7
0.7
0.9
1.0
1.0
1.5
1.7
1.7
Sussex: Delaware Bay
67.5
4.3
1.2
1.1
1.1
1.0
1.0
1.0
0.7
0.7
0.7
Sussex: Atlantic Coast
40.9
3.5
2.6
2.2
2.2
2.0
1.8
1.8
1.4
1.2
1.2
Statewide
357.1
22.2
9.8
9.2
8.9
7.9
7.8
7.9
7.6
7.5
7.4
Cumulative (total) amount of land below a given elevation
b
Dry Land
72
126
178
235
301
370
441
514
590
663
Nontidal Wetlands
22
32
41
50
58
66
74
81
89
96
All Land
357
452
515
577
642
716
793
871
953
1036
1116
a For example, Kent County has 13 square kilometers of dry land between 0.5 and 1.0 meters above spring
high water.
b For example, Delaware has 126 square kilometers of dry land less than 1 meter above spring high water.
-------
[ SECTION 1.2 61 ]
Table A7. Maryland (square kilometers)
Meters above Spring High Water
County
0.5
1.0
1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment3
Anne Arundel
5.3
5.3
7.4
11.7
11.7
10.9
8.9
8.9
8.9
8.7
Baltimore County
4.8
5.5
6
7.3
8.9
10.1
10.2
7.8
8.7
8.7
Calvert
1.9
1.9
1.6
1.5
1.6
3.4
3.6
3.6
4.6
4.7
Cecil
1.2
1.5
2.1
2.1
2.6
4.2
4.2
4.3
4.6
4.6
Charles
5.8
5.7
7.5
7.5
7.6
12.7
13.1
13.1
8.2
7.8
Dorchester
74
114.3
62.3
48.1
36.9
37
34
25
19.1
17.4
Harford
9.1
8.9
6.3
6.2
6.3
8.4
8.5
8.4
5.2
5.1
Kent
4
6
6.7
6.8
6.4
11.2
11.2
11.2
12.5
12.9
Queen Anne's
1.9
6.5
9.5
11.2
13.5
16.8
19.3
19.3
18.6
18
Somerset
39.2
47
45.5
52.5
19.9
18.5
27.8
28.4
28.7
29.3
St. Mary's
8.2
8.2
11
11.2
11.2
20.9
21.4
21.4
11.4
10.3
Talbot
4.2
12.2
23.2
41.7
44.1
37.1
35
32.3
23.4
19.5
Wicomico
10
13.1
14.7
15
14.6
13.7
14.3
14.3
14.5
13.5
Worcester
11.5
24.1
31.6
36.7
35
32
27.5
25.7
26
26.6
Other6
4.3
4.9
5.4
5.7
6.1
7.1
7.1
7.4
8.4
8.5
Statewide 185.3 265.1 240.7 265.1 226.3 243.8 246.0 231.2 202.8 195.3
Wetlands Tidal Nontidal Wetlands, by half meter elevation increment
Charles
24.2
1.9
1.9
2.2
2.2
2.2
2.4
2.4
2.4
1.5
1.4
Dorchester
424.8
32.5
30.1
20.6
16.2
10.3
6.9
10.1
6.8
4.8
3.1
Harford
29.4
1.4
1.3
1.0
1.0
1.0
1.4
1.4
1.4
0.7
0.6
Somerset
265.4
12.3
7.0
7.2
11.9
3.5
6.0
10.1
7.0
9.3
10.9
St. Mary's
18.7
1.5
1.6
2.1
2.1
2.1
3.9
3.9
3.9
3.0
2.9
Talbot
26.1
0.1
0.6
0.9
1.7
2.2
2.1
2.6
3.8
2.6
2.0
Wicomico
67.0
8.4
3.4
7.3
7.7
5.2
8.9
9.4
8.0
5.5
4.8
Worcester
142.2
2.8
5.4
5.2
6.1
6.1
7.2
6.8
6.4
5.3
5.0
Other0
118.0
3.5
5.9
7.2
8.7
8.1
8.5
7.0
7.2
8.6
8.7
Statewide
1115.8
64.5
57.2
53.8
57.6
40.8
47.2
53.7
47.0
41.3
39.5
Cumulative (total) amount of land below a given elevation0
Dry Land 185 450 691 956 1182 1426 1672 1904 2106 2302
Nontidal Wetlands
64
122
175
233
274
321
375
422
463
503
All Land
1116 1366
1688
1982
2305
2572
2863
3163
3441
3685
3920
a For example, Anne Arundel County has 5.3 square kilometers of dry land between 0.5 and 1.0 meters
above spring high water.
b Includes Baltimore City, Caroline, and Prince George's Counties.
c Includes Baltimore City, Caroline, Prince George's, Anne Arundel, Baltimore County, Calvert, Cecil, Kent,
and Queen Anne's Counties.
d For example, Maryland has 450 square kilometers of dry land less than 1 meter above spring high water.
-------
[ 62 AREA OF LAND CLOSE TO SEA LEVEL, BY STATE ]
Table A8. Washington, D.C. (square kilometers)
0.5
Meters above Spring High Water
1.0 1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment3
Washington, D.C.
2.43
1.16 1.40 1.42 1.81 1.84 1.83 1.80
1.68
1.65
Wetlands
Tidal
-Nontidal Wetlands, by half meter elevation increment
Washington, D.C.
0.79
0.04
0.02 0.03 0.02 0.02 0.02 0.03 0.03
0.05
0.05
Cumulative (total) amount of land below a given elevationb
Dry Land
2.43
3.59 4.98 6.40 8.22 10.06 11.88 13.69 15.37
17.01
Nontidal Wetlands
0.04
0.06 0.09 0.11 0.13 0.14 0.17 0.21
0.26
0.31
All Land 0.79 3.26 4.44 5.86 7.31 9.13 10.99 12.85 14.68 16.41 18.12
a For example, DC has 1.16 square kilometers of dry land between 0.5 and 1.0 meters above spring high
water.
b For example, DC has 3.59 square kilometers of dry land less than 1 meter above spring high water.
-------
[ SECTION 1.2 63 ]
Table A9. Virginia (square kilometers)
Meters above Spring High Water
County
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Dry Land, by half meter elevation increment3
Eastern Shore
45.5
39.8
42.9
43.1
42.6
37.1
36.4
35.6
33.5
33.5
Accomack
29.5
29.1
32.7
32.9
31.3
20.7
20.0
19.1
15.3
15.0
Northampton
15.9
10.7
10.2
10.2
11.3
16.4
16.5
16.6
18.1
18.5
Northern Virginia
2.7
2.7
2.7
2.7
2.9
3.3
3.3
3.3
3.3
3.3
Rappahannock Area
3.5
3.5
3.5
3.5
3.5
6.8
6.8
6.8
6.8
6.8
Northern Neck
16.2
16.2
16.5
16.5
16.7
42.4
46.9
46.9
47.0
47.0
Middle Peninsula
30.6
32.5
42.3
42.5
42.7
37.3
37.4
36.7
26.6
26.4
Gloucester
11.3
12.4
15.1
15.1
13.5
8.5
8.5
7.9
5.6
5.6
Mathews
10.7
11.5
18.2
18.3
17.8
11.4
11.4
11.2
3.7
3.6
Otherb
8.5
8.5
9.0
9.1
11.5
17.4
17.6
17.6
17.4
17.3
Hampton Roads0
65.5
74.0
105.9
119.3
134.1
188.7
198.7
191.9
138.4
116.3
Virginia Beach
24.0
25.2
35.0
44.0
45.3
56.3
54.4
53.6
35.7
25.3
Chesapeake
8.4
10.7
20.2
24.6
29.7
55.7
67.5
68.4
59.9
48.1
Portsmouth
2.7
3.7
5.2
5.2
7.4
11.5
11.5
9.6
4.8
4.8
Hampton
4.1
6.4
12.2
12.2
13.1
14.3
14.3
12.4
4.8
4.8
Norfolk
4.1
6.3
11.3
11.3
14.5
24.5
24.5
20.5
4.2
4.2
York
4.3
5.0
6.5
6.5
6.0
4.8
4.8
4.3
2.7
2.7
Newport News
4.9
4.3
3.2
3.2
3.2
3.5
3.5
3.8
4.7
4.7
Poquoson
3.2
3.4
3.6
3.6
2.7
0.1
0.1
0.1
0.0
0.0
Suffolk
3.4
3.0
2.8
2.8
5.4
8.6
8.6
9.6
11.7
11.8
James City
2.8
2.7
2.5
2.5
2.7
3.8
3.8
3.8
3.9
3.9
Isle of Wight
2.6
2.4
2.4
2.4
3.1
4.9
4.9
5.0
5.2
5.2
Surry
1.0
1.0
1.0
1.0
1.0
0.9
0.9
0.9
0.9
0.9
Other Jurisdictions'1
8.1
8.1
9.3
9.3
11.0
16.5
16.6
16.7
19.4
19.7
Statewide
172.1
176.8
223.0
236.9
253.4
332.1
346.2
337.9
275.0
253.0
Table continued on following page
-------
[ 64 AREA OF LAND CLOSE TO SEA LEVEL, BY STATE ]
Table A9. Virginia (square kilometers) continued
Meters above Spring High Water
County
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Wetlands
Tidal -
—Nontidal Wetlands, by half meter elevation increment
Eastern Shore
945.5
15.8
18.2
24.3
24.5
21.8
12.2
11.7
11.3
7.9
7.6
Accomack
483.5
15.0
17.0
22.0
22.2
20.0
10.6
10.1
9.7
6.9
6.6
Northampton
462.0
0.8
1.2
2.2
2.3
1.9
1.6
1.6
1.6
1.1
1.0
Northern Virginia
10.2
0.3
0.3
0.3
0.3
0.3
0.2
0.2
0.2
0.2
0.2
Rappahannock
Area
26.7
0.8
0.8
0.8
0.8
0.8
0.9
0.9
0.9
0.9
0.9
Northern Neck
57.3
1.8
1.8
1.8
1.8
1.8
3.5
3.9
3.9
3.9
3.9
Middle Peninsula
164.4
8.7
9.4
12.5
12.5
11.9
12.0
11.9
11.7
7.7
7.6
Gloucester
43.5
3.9
4.5
5.7
5.7
5.1
2.9
2.9
2.7
1.7
1.7
Mathews
27.1
2.8
3.0
4.8
4.8
4.9
7.5
7.5
7.5
4.5
4.4
Other8
93.9
2.0
2.0
2.0
2.0
1.9
1.5
1.5
1.5
1.5
1.5
Hampton Roads'
330.2
32.6
31.4
22.6
20.7
28.9
39.3
38.8
39.9
39.8
37.9
Virginia Beach
112.4
10.5
10.0
7.0
7.5
7.3
4.6
3.4
3.3
2.5
1.8
Chesapeake
39.7
12.2
12.7
10.1
7.7
16.1
30.1
30.7
31.8
32.2
31.0
Portsmouth
3.7
5.3
3.5
0.2
0.2
0.3
0.4
0.4
0.3
0.2
0.2
Hampton
14.4
0.1
0.2
0.2
0.2
0.3
0.7
0.7
0.8
1.1
1.1
Norfolk
4.7
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.0
0.0
York
17.0
0.6
1.0
1.9
1.9
1.5
0.6
0.6
0.6
0.4
0.4
Newport News
15.1
0.2
0.3
0.3
0.3
0.2
0.0
0.0
0.0
0.1
0.1
Poquoson
23.7
0.0
0.1
0.3
0.3
0.2
0.0
0.0
0.0
0.0
0.0
Suffolk
26.3
1.5
1.5
0.7
0.7
0.9
1.0
1.0
1.1
1.6
1.6
James City
32.8
0.6
0.6
0.6
0.6
0.5
0.4
0.4
0.4
0.4
0.4
Isle of Wght
28.9
0.9
0.9
0.7
0.7
0.8
1.1
1.1
1.1
1.2
1.2
Surry
11.5
0.5
0.5
0.5
0.5
0.4
0.2
0.2
0.2
0.2
0.2
Other
Jurisdictions9
84.5
13.1
13.1
8.1
8.0
7.1
6.3
6.3
6.3
6.0
6.0
Virginia
1618.9
73.1
75.0
70.4
68.6
72.6
74.3
73.7
74.1
66.5
64.1
Cumulative (total) amount of land below a given elevation"
Dry Land
172
349
572
809
1062
1394
1741
2079
2354
2606
Nontidal Wetlands
73
148
218
287
360
434
508
582
648
713
All Land
1619
1864
2116
2409
2715
3041
3447
3867
4279
4621
4938
a For example, Gloucester has 12.4 km2 of dry land between 0.5 and 1.0 meters above spring high water.
b Includes Essex, King and Queen, King William, and Middlesex Counties.
cExcludes Southampton, Franklin, and Williamsburg.
includes Charles City, Chesterfield, Hanover, Henrico, New Kent, Prince George, Southampton, and Sussex
Counties and the cities of Colonial Heights, Franklin, Hopewell, Petersburg, and Wlliamsburg.
includes Essex, King and Queen, King Wlliam, and Middlesex Counties.
fExcludes Southampton, Franklin, and Wlliamsburg.
includes Charles City, Chesterfield, Hanover, Henrico, New Kent, Prince George, Southampton, and Sussex
Counties and the cities of Colonial Heights, Franklin, Hopewell, Petersburg, and Wlliamsburg.
hFor example, Virginia has a total of 349 square kilometers of dry land less than 1 meter above spring high
water.
-------
[ SECTION 1.2 65 ]
Table A10. Virginia jurisdictions not included in shore protection study (hectares)
Meters above Spring High Water
County
0.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment
Charles City
237.9
237.9
237.9
237.9
296.2
445.5
445.5
445.5
445.5
445.5
Chesterfield
97.5
97.5
97.5
97.5
78.0
67.2
67.2
67.2
67.2
67.2
Colonial Heights
2.6
2.6
2.6
2.6
1.7
1.1
1.1
1.1
1.1
1.1
Franklin
5.1
5.1
19.5
19.7
19.7
24.2
24.5
24.5
35.1
36.4
Hanover
1.8
1.8
1.8
1.8
7.6
9.9
9.9
9.9
9.9
9.9
Henrico
57.0
57.0
57.0
57.0
47.4
40.8
40.8
40.8
40.8
40.8
Hopewell
28.1
28.1
28.1
28.1
18.0
10.9
10.9
10.9
10.9
10.9
New Kent
154.0
154.0
154.0
154.0
257.5
372.5
372.5
372.5
372.5
372.5
Petersburg
0.0
0.0
0.0
0.0
0.2
0.3
0.3
0.3
0.3
0.3
Prince George
140.5
140.5
140.5
140.5
178.4
287.8
287.8
287.8
287.8
287.8
Southampton
82.3
82.3
184.4
185.7
185.7
379.0
391.6
391.6
653.7
686.0
Williamsburg
3.7
3.7
3.7
3.7
4.0
5.7
5.7
5.7
5.7
5.7
Wetlands
Tidal
Nontidal Wetlands, by half meter elevation increment
Charles City
2215.5
138.8
138.8
138.8
138.8
108.2
57.9
57.9
57.9
57.9
57.9
Chesterfield
1052.3
26.1
26.1
26.1
26.1
11.2
2.7
2.7
2.7
2.7
2.7
Colonial Heights
52.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Franklin
0.0
67.6
67.6
23.2
22.7
22.7
2.9
1.6
1.6
0.8
0.7
Hanover
114.2
0.0
0.0
0.0
0.0
0.1
0.2
0.2
0.2
0.2
0.2
Henrico
422.5
3.0
3.0
3.0
3.0
3.4
3.8
3.8
3.8
3.8
3.8
Hopewell
73.1
7.4
7.4
7.4
7.4
3.9
1.3
1.3
1.3
1.3
1.3
New Kent
3390.9
169.5
169.5
169.5
169.5
120.1
55.6
55.6
55.6
55.6
55.6
Petersburg
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Prince George
1091.1
57.6
57.6
57.6
57.6
59.3
76.2
76.2
76.2
76.2
76.2
Southampton
0.0
835.8
835.8
383.9
378.3
378.3
421.1
423.9
423.9
399.9
396.9
Williamsburg
39.7
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
-------
[ 66 AREA OF LAND CLOSE TO SEA LEVEL, BY STATE ]
Table A11. North Carolina (square kilometers)
Meters above Spring High Water
County
0.5a
1.0
1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment11
Beaufort
50.4
61.0
66.2
81.9
84.7
80.9
83.3
96.7
68.9
48.8
Camden
16.8
11.3
50.0
39.0
46.5
52.8
26.4
23.1
35.8
22.3
Carteret
51.2
69.8
90.0
107.5
79.1
21.7
15.1
16.5
17.4
13.3
Currituck
19.8
26.4
36.6
57.4
57.2
51.8
32.7
21.6
9.1
5.4
Dare
45.4
22.2
17.9
15.2
15.2
11.7
8.8
5.3
3.3
2.1
Hyde
295.7
141.3
56.4
52.9
51.6
39.5
25.2
18.4
12.0
5.7
Onslow
24.6
10.1
9.9
11.5
14.7
11.6
15.5
17.9
13.6
21.8
Pamlico
24.2
35.4
52.2
53.4
38.6
34.8
30.7
22.7
15.7
9.2
Pasquotank
10.6
28.8
43.4
48.7
47.3
40.6
71.8
93.7
47.8
25.3
Tyrrell
139.9
143.4
49.6
26.1
12.6
3.5
3.2
1.3
0.5
0.0
Other0
60.3
73.7
105.6
138.2
177.8
213.7
292.6
380.4
319.8
227.9
Not Considered01
3.0
2.7
3.8
5.1
7.1
9.4
12.9
18.0
22.5
30.5
Statewide
741.9
626.1
581.6
636.9
632.5
572
618.2
715.6
566.4
412.3
Wetlands
Tidal -
Nontidal Wetlands, by half meter elevation increment-
Beaufort
35.1
68.0
40.9
32.3
32.4
44.6
37.0
24.2
16.4
15.3
12.7
Brunswick
109.2
38.5
8.7
7.4
6.1
6.3
6.2
5.7
5.9
5.0
4.8
Camden
7.1
142.5
7.5
10.6
7.6
10.2
11.8
7.2
7.4
12.5
30.1
Carteret
334.3
34.3
53.0
48.1
44.7
36.2
20.5
10.6
10.9
15.6
12.7
Currituck
124.6
131.8
18.3
13.2
14.6
9.7
8.9
4.2
3.3
4.4
10.6
Dare
167.8
402.2
162.2
61.4
33.8
5.0
1.1
0.4
0.2
0.1
0.1
Hyde
199.3
345.6
153.3
52.9
27.5
19.7
22.1
18.0
22.4
13.7
10.2
Pamlico
111.6
52.8
20.8
12.1
20.8
25.6
16.4
22.5
22.1
13.0
15.2
Pender
38.2
87.2
28.2
18.0
17.5
14.6
14.3
13.6
13.1
13.9
12.2
Tyrrell
3.8
433.4
95.7
32.3
10.7
11.4
10.6
12.8
9.7
5.0
1.1
Other8
137.5
605.1
119.8
96.1
93.4
98.3
94.6
95.7
105.4
100.8
98.7
Not Considered01
3.5
30.9
10.2
10.0
11.7
14.2
15.8
18.7
21.2
19.6
26.3
Statewide
1272.0
2372.3
718.6
394.4
320.8
295.8
259.3
233.6
238
218.9
234.7
Cumulative (total) amount of land below a given elevation'
Dry Land
742
1368
1950
2587
3219
3791
4410
5125
5692
6104
Nontidal Wetlands
2372
3091
3485
3806
4102
4361
4595
4833
5052
5286
All Land
1272
4386
5731
6707
7665
8593
9425
10276
11230
12016
12662
a Includes land below spring high water.
b For example, Beaufort County has 61 square kilometers of dry land between 0.5 and 1.0 meters above
spring high water.
c Includes Bertie, Brunswick, Chowan, Craven, Gates, Hertford, Martin, New Hanover, Pender, Perquimans,
and Washington Counties.
d Includes Bladen, Columbus, Duplin, Jones, Lenoir, Northampton, Pitt and Sampson Counties.
8 Includes Bertie, Chowan, Craven, Gates, Hertford, Martin, New Hanover, Onslow, Pasquotank, Perquimans,
and Washington Counties.
f For example, North Carolina has 1368 square kilometers of dry land less than 1 meter above spring high
water.
-------
[ SECTION 1.2 67 ]
Table A12. North Carolina jurisdictions not included in shore protection study (hectares)
Meters above Spring High Water
County
0.5
1.0
1.5 2.0 2.5 3.0 3.5 4.0
4.5
5.0
Dry Land, by half meter elevation increment
Bladen
0.0
0.0
0.1
1.7
6.8
12.2
33.7
112.2
225.0
691.0
Columbus
0.2
2.1
2.8
8.8
13.9
18.5
21.2
22.9
32.9
39.3
Duplin
0.2
0.1
0.1
0.0
0.5
2.3
6.2
13.7
19.3
55.2
Jones
190.4
116.3
140.3
178.4
224.2
312.0
388.4
525.8
676.4
762.9
Lenoir
0.0
0.0
0.0
0.0
0.5
5.1
11.3
21.2
50.9
96.2
Northampton
6.5
10.4
11.1
19.8
47.7
83.2
114.2
124.7
131.6
140.1
Pitt
105.8
137.0
230.2
303.5
421.4
508.0
710.1
973.0
1106.3
1233.4
Sampson
0.0
0.0
0.0
0.0
0.0
2.5
5.0
8.2
11.4
34.1
Wetlands
Tidal
Nontidal Wetlands,
, by half
meter elevation increment
Bladen
0.0
0.3
20.3
70.1
125.9
214.1
277.6
432.4
644.7
461.4
895.1
Columbus
0.0
20.1
58.2
104.9
134.7
126.8
108.1
86.3
58.1
47.3
143.5
Duplin
0.0
0.0
0.0
0.0
0.0
5.0
9.5
65.3
134.6
112.4
221.9
Jones
350.8
811.1
332.6
246.7
263.8
244.8
251.8
241.0
271.4
242.4
220.7
Lenoir
0.0
0.0
0.0
13.6
40.3
108.4
168.4
246.9
205.3
361.9
405.4
Northampton
0.0
119.8
85.7
73.5
125.2
224.1
192.9
194.0
133.7
82.8
80.3
Pitt
0.0
2142.9
526.3
490.1
479.3
497.3
497.0
500.9
557.6
550.0
456.0
Sampson
0.0
0.0
0.0
0.0
0.0
0.1
70.1
99.5
115.9
100.5
202.1
-------
1.3. Uncertainty Ranges Associated with EPA's
Estimates of the Area of Land Close to Sea Level
Authors: James G. Titus, U.S. Environmental Protection Agency
Dave Cacela, Stratus Consulting Inc.
This section should be cited as:
Titus, J.G., and D. Cacela. 2008. Uncertainty Ranges Associated with EPA's Estimates of the
Area of Land Close to Sea Level. Section 1.3 in: Background Documents Supporting Climate
Change Science Program Synthesis and Assessment Product 4.1: Coastal Elevations and
Sensitivity to Sea Level Rise, J.G. Titus and E.M. Strange (eds.). EPA 430R07004. U.S.
EPA, Washington, DC.
-------
Section 1.3.1. Approach Author: James G. Titus
Introduction
Digital Elevation Model output allows one to
easily generate a point estimate ("best guess") of
the amount of land below a particular elevation
X by simply tabulating the number of points
below X and multiplying by the cell size that
each point represents. The accuracy of available
elevation data varies, however, so the accuracy
of these point estimates of the area estimates will
vary as well. For some purposes, it may be
sufficient to have a "best guess" estimate. But for
other purposes, one needs some sort of
uncertainty range. Fortunately, most elevation
data come with a precision estimate, which
makes it possible to develop an uncertainty
range.
Section 1.3 explains how Dave Cacela and this
author generated an uncertainty range for the
estimates of the amount of land close to sea level
within different shore protection categories and
different elevations, which form the basis of this
report. Section 1.3.1 explains the assumptions
and the basic approach for estimating
uncertainty; Section 1.3.2 explains how the
approach was implemented. Section 1.3.3
provides the results. The final results constitute
the three appendices to this section.
Like Section 1.2, by Jones and Wang, the
starting point is the elevation data set developed
in Section 1.1 by Titus and Wang. The approach
for specifying uncertainty is based on the most
important sources of error in that analysis. The
actual implementation, however, uses the output
from Section 1.2, in which Jones and Wang
overlay the elevation study by Titus and Wang
with the eight state-specific shore protection
studies that Titus and Hudgens developed in
their unpublished analysis mentioned in Section
1.2. Section 1.1 provided cumulative elevation
distributions for dry land and nontidal wetlands;
Section 1.2 subdivided the dry land into the
various shore protection categories. Our
exposition of the approach taken focuses on the
elevation distribution of dry land. But not only
did we apply the procedure to the totals for dry
land, we also applied it to all the other shore
protection categories and nontidal wetlands.
We warn the reader at the outset that this section
switches between metric (standard international)
and English (imperial) units of measurement.
The final results are in metric units—but most of
the underlying elevation data were based on
topographic maps with contour intervals
measured in feet. The point of measurements
provided in this section is generally to explain
the relationship between input data and
assumptions, not to inform the reader about the
magnitude of any particular effect. Therefore, the
reader unfamiliar with one or the other system of
measurements need not attempt to make
conversions. In the few cases where that actual
magnitude may matter, our convention is metric.
Background
Previous assessments of the land vulnerable to
sea level rise have provided an uncertainty range;
but the uncertainty range did not include
uncertainty associated with topographic
information. EPA's 1989 Report to Congress
provided an uncertainty range about the area of
land lost for a rise in sea level of 50, 100, or 200
cm. In Appendix B to that Report to Congress,
Titus and Greene (1989) developed the
uncertainty range, based on a study by Park et al.
(1989), who used a sample of study area sites,
and calculated a point estimate of land loss of
each site. The published uncertainty range used a
simple sampling error approach, treating the
study sites as a random sample from the entire
population of USGS quads. Because Park et al.
did not report an uncertainty range for their
-------
[70 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
sample sites, Titus and Greene made no attempt
to include that uncertainty. In effect, Titus and
Greene assumed that Park et al. accurately
estimated the amount of land at particular
elevations in those areas they assessed. The true
uncertainty associated with their estimates
included both sampling and measurement error;
but the published uncertainty range considered
only the sampling error.
This study uses the elevation data from Section
1.1, as formatted by the analysis explained in
Section 1.2. That data set estimated the
elevations of all land above spring high water.
That is, it estimated elevations for dry land and
nontidal wetlands, but did not estimate
elevations for tidal wetlands. (Knowing that land
is tidal wetland tells us that the land elevation is
below spring high water and above mean low
water, which provides a narrower uncertainty
range about the elevation than if we know only
that the land is below, for example, the 10-ft
contour on a topographic map.) Because they
obtained data for the entirety of the study area,
there is no sampling error. The source of error
stems entirely from the limitations in precision
of the Section 1.1 results.
The overall approach is to make an assumption
about the potential vertical error of the elevation
data and the extent to which that error is random
versus systematic. The magnitude of the error
varies by data source: because we assume that
error is a function of contour interval, which in
turn varies by topographic quad, we calculate
error separately for each topographic quad. Let
us first explain our basis for focusing on vertical
error of the elevation data, and then explain how
low and high estimates for areas were calculated
where the input data were USGS contour maps
and other data with relatively coarse contour
intervals (1 meter or worse), as well as our
procedure for when the data had higher quality
(2 feet or better).
Horizontal and Vertical Precision
Figure 1.3.1 depicts the various sources of data
used to estimate elevations and the areas of land
at particular elevations. In most locations, Titus
and Wang relied on USGS 1:24,000 scale maps
with various contour intervals. The second most
common source of data was LIDAR provided by
Maryland or North Carolina, which give
elevations at various points in a grid.
USGS maps follow the national mapping
standards for vertical and horizontal precision.
The vertical standard is that 90 percent of the
well-defined points along a contour must be
within one-half the contour interval above or
below the stated elevation of the contour. The
horizontal standard is that 90 percent of the
points should be within one fiftieth of an inch
(about half a millimeter). On a 1:24,000 scale
map, the allowable horizontal accuracy would be
12 meters. The LIDAR data sources generally
have vertical precision on the order of 10-30 cm
and horizontal error of less than 1 meter.
To keep the analysis reasonably manageable, this
study ignores the horizontal error and focuses
entirely on the vertical errors. Inspection of the
USGS maps and the maps produced by Titus and
Wang shows that most lowland is in an area
where the contours are hundreds—and often
thousands—of meters apart. Random error on
the order of 12 meters is very small by
comparison and not likely to substantially
change an estimated error range. The horizontal
error of LIDAR seemed even less likely to
matter. In an assessment of the impacts of rising
sea level, what matters is that most of the input
data had contour intervals of 5 feet (150 cm) or
worse, and we are interested in the implications
of a 50-cm rise.
-------
[ SECTION 1 .3 71 ]
PA
MD
fi
/ ^
J c
DC
VA
ATLANTIC
OCEAN
Contour Intervals
| Spot Elevation
Lidar
2 Feet
1 Meter
5 Feet
10 Feet
10 Feet, State Data
20 Feet
Figure 1.3.1. Input Elevation Data used in Section 1.1 to Estimate Area of Land Close to Sea Level.
Quadrangles with a 10-ft contour interval and a 5-ft supplemental contour are shown as 5 feet. The
Maryland data included 5-ft contours drawn from spot elevation with RMS error of 5 feet; hence the legend
calls the data "10 feet, State Data"; USGS 5-ft contours have an RMS error of 2,5 feet.
-------
[72 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Areas with USGS Maps as the Input Data
This analysis assumes that the standard deviation
of error within a neighborhood is one-half the
contour interval, based on National Map
Accuracy standards. For reasons discussed
below, the calculations also assume that half the
error is random and half is systematic, so that the
standard deviation of the uncertainty is one-
quarter the contour interval for areas the size of a
county or larger. These assumptions are adjusted
to address possible error in the estimate of spring
high water (SHW).
Our Initial Model of Vertical Error
Based on a comparison of their model results
with LIDAR from Maryland and North Carolina
(see Section 1.1, Jones 2007, and Jones et al.
2008), Titus and Wang report that the root mean
square (RMS) error1 of their elevation data sets
tended to be approximately one-half the contour
interval of the input contour. (Strictly speaking,
their comparison measured the root mean square
of the difference between the DEM and the
LIDAR, which overestimates the error of the
DEM.2) That finding seems roughly consistent
with the National Map Accuracy Standard that
90 percent of the well-defined points should be
within one-half contour interval of the stated
elevation (Bureau of the Budget 1947)—
"roughly" because they are not identical: If mean
error is zero, a 90 percent confidence limit will
almost always be a wider interval than the range
defined by an estimate plus or minus the RMS
1 RMS error is calculated by taking the difference between
the estimated and actual values for each point, squaring
that difference, taking the sum of squares, dividing that
sum by the total number of data points, and taking the
square root. If the mean error is zero, RMS error is equal
to the standard deviation of the error. If the mean error is
not zero, then RMS error is equal to the square root of the
sum of (a) the square of the mean error plus (b) the square
of the standard deviation of the error.
2 In general, whenever one has two independent
measurements Mi and M2, with random error ei and e2,
variance(Mi-M2) = variance (ei) + variance (e2).
Thus, the variance of one error is equal to the variance of
the difference minus the variance of the other error.
error. In a normal distribution, the 90 percent
interval would encompass a range ±1.64 times
the RMS error (generally called standard
deviation or o in this case).3 But one would
expect the error across all elevations to be
greater than the error at those elevations where
we have a contour. For example, if a USGS map
says that one contour is 5 feet above the vertical
datum and that another contour is 10 feet above
the vertical datum, and then one estimates an 8-ft
contour through interpolation, we would expect
the USGS contours to be somewhat more
accurate than the 8-ft contour derived from the
two USGS contours. So the assumption that 90
percent of the points along the contour are within
one-half the contour interval of the stated
elevation would be roughly consistent with the
assumption that the standard deviation of error
for all elevations is one-half the contour
interval.4 Because Titus and Wang did not know
whether their estimates have a mean error or not,
the more general term "RMS error" better
describes the uncertainty. The contour intervals
vary from place to place—but we know the
contour interval at all locations. Therefore, this
study assumes that RMS error equals one-half
the contour interval for all locations where
contour maps were the underlying source of the
data.
Given that the availability of an estimate of the
RMS error, this author's first thought was that
the low and high estimates could be derived by
simply (a) adding and subtracting the RMS error
from the DEM5 data set developed by Titus and
Wang, cell by cell, and then (b) retabulating the
data. In effect, this approach would add and
3The RMS error band includes about 68 percent of all data
points.
4In the case of normally distributed error, we are saying, in
effect, that 90 percent of the points along the contour are
within 0.5 contour interval, while 90 percent of all points
are within 0.82 (1.64/2) the contour interval of the stated
elevation.
5DEM is an abbreviation for digital elevation model.
Literally, that means the model used to calculate
elevations. People in the business of making elevation
maps, however, often use this term when referring to the
actual set of elevation data points calculated by their
model. The Titus and Wang data set we used has data
points on a 30-m grid.
-------
[ SECTION 1 .3 73 ]
15 ft
C
o
-4—'
03
>
Q)
LU
10 ft
SHW
Area below
1st contour
subtract the RMS
error from the
cumulative
distribution of
elevations. However,
as those authors
discuss in Section
1.1, their DEM
contained plateaus
along the input
contours, which were
artifacts of the
interpolation
algorithm, with no
physical basis.6
Therefore, they
concluded that a
linear interpolation
of elevations
between the contours
would give a better
estimate of the area
of land below a
particular elevation
than the cumulative distribution of their cell-by-
cell DEM output. Therefore, their elevation
density distribution
assumed that elevations were uniformly
distributed between contours. If the input data
said that there are 100 ha of land between the 5-
and 10-ft contours, for example, then there are
20 ha between the 5- and 6-ft contours, they
assumed. Thus, their cumulative elevation
distribution function was a series of line
segments connecting a few points that represent
actual observations based on the contour interval
and the area of land above spring high water land
below specific contours.7 (See the green line in
Figure 1.3.2, discussed below.)
This study assumes that the same logic that
applies for the "point estimates" would apply to
Green dots represent observation from the maps; Green Line represents interpolated central estim^
Red dots represent positive contour error or negative SHW error
Black dots represent negative contour error or positive SHW error
Solid lines: No SHW error or all three SHW error estimates coincide
Dashed lines: SHW error compounds contour error (relative to SHW)
Dotted lines: SHW error offsets contour error (relative to SHW)
Area below
2nd contour
Area below
3rd contour
Figure 1.3.2. Interpolated Elevation Estimates Relative to NGVD29. Central
estimate and high contour error (with and without SHW error, relative to NGVD,
ignoring model error). This case assumes a 5-ft contour interval, a 1 -ft error in
estimating the elevation of spring high water, and contour error of 2.5 feet. Red
dots represent positive contour error and negative SHW error, both of which cause
a positive error in our estimates of elevation relative to SHW.
EPA's effort to estimate an uncertainty range.
Choosing instead to add or subtract one-half
contour interval from the DEM, would (for
example) create data sets with plateaus at 2.5,
7.5, 12.5, and 17.5 feet in those areas where the
USGS data had a contour interval of 5 feet, just
as the Titus and Wang output had plateaus at
SHW, 5, 10, 15, and 20 feet.8
Let us go back to the source information. For
each quad, Titus and Wang provide
• the areas of land that lie below specific
elevation contours from the input data set
(e.g., the area between the 5- and 10-ft
contours in a given quad), and
• their estimate of the elevation of spring high
water relative to NGVD29 (derived from
NOAA tidal datum).
6See Section 1.1.3 at Step 4, and especially Table 1.1.3 in
Section 1.1.4. The large horizontal error but small vertical
error in replicating contours is indicative of large plateaus.
7In an area with a 5-ft contour interval, those points would
be (SHW, 0), (5, A(5)), (10, A(10)), (15, A(15)), (20,
A(20)) ... etc., where A(x) is the area of land between
spring high water and elevation x.
8Their data set also created plateaus just above their spring
high water supplemental contour. Thus, if spring high
water is 2 feet (NGVD29), then the high-elevation estimate
would have a plateau at 4.5 feet; the low-elevation
estimate would have a plateau at 2.5 feet below spring high
water, that is, -0.5 feet (NGVD29).
-------
[74 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Area below Area below Area below
1st contour 2*contour 3*contour
Figure 1.3.3. Interpolated Elevation Estimates Relative to Spring High Water. Central estimate and
high contour error (with and without SHW error, relative to SHW, ignoring model error). This case assumes
a 5-ft contour interval, a 1 -ft error in estimating the elevation of spring high water, and contour error of 2.5
feet.
The estimates of the land below various
elevations were based on simple linear
interpolation of this information.9 Figures 1.3.2
through 1.3.4 illustrate a proposed approach to
generating high and low elevation estimates,
respectively. But before discussing that
approach, let us examine a depiction of the Titus
and Wang analysis (see Section 1.1) used as
input to this study. In Figure 1.3.2 (as well as
Figures 1.3.3 and 1.3.4), the four green dots
represent the values of the input data. This
example quad has a 5-ft contour interval, and
spring high water is estimated to be 3 feet above
NGVD29. The first green dot shows the
estimated elevation of spring high water; this dot
9In some cases, the 5-ft contour was seaward of the
wetland boundary and the Titus and Wang interpolation
disregarded the 5-ft contour on the assumption that it was
obsolete. In those cases, the interpolation created—in
effect—a new 5-ft contour farther inland, which was used
in quantifying the land below 5 feet in a given quad.
appears along the vertical axis because all the
dry land and nontidal wetlands are above spring
high water (by definition). The other three points
show the amount of land (other than tidal
wetlands) below the 5-, 10-, and 15-ft contours.
The green line is the cumulative elevation
distributions that Titus and Wang derived
through interpolation—but transposed so that the
cumulative elevation is on the horizontal axis
and elevation on the vertical axis. The figures are
transposed from the traditional way of depicting
cumulative distribution functions, because the
transposed version gives us the actual profile of a
typical transect or cross section of the land.
Now let us consider a possible way to think
about high and low error. In Figure 1.3.2, the
three red dots with elevations of 7.5, 12.5, and
17.5 feet represent high estimates of the
elevation of the contours. That is, given the RMS
error of one-half the contour interval (2.5 feet),
the 5-ft contour could actually be as high as 7.5
feet. Along the vertical axis, we see three dots.
-------
[ SECTION 1 .3 75 ]
C
o
+J
(0
>
0
LU
I
Area below
1st contour
i
Area below
2nd contour
Area below
3rd contour
Figure 1.3.4. Interpolated Elevation Estimates Relative to NGVD29. Central estimate and low contour
error (with and without SHW error, relative to NGVD, ignoring model error). This case assumes a 5-ft
contour interval, a 1 -ft error in estimating the elevation of SHW, and contour error of 2.5 feet
As previously mentioned, the green dot is the
estimate of spring high water (3 feet). The red
and black dots at 2 and 4 feet, respectively,
represent the possibility that Titus and Wang
over- or underestimated SHW, respectively. The
three red lines represent the alternative high-
elevation cumulative elevation distributions (and
average profile) implied by the three different
estimates of the elevation of SHW. In all these
cases, the profile is steeper than the profile
implied by the input data. The dashed line—
where spring high water is less than estimated—
provides the steepest profile and hence the
greatest error. Put another way, the dashed line
assumes that SHW is lower—and the contour is
higher—than assumed by Titus and Wang; i.e.,
the errors compound. Figure 1.3.3 shows the
same four cases, but with elevations relative to
spring high water instead of NGVD29.
Comparing Figures 1.3.2 and 1.3.3 may help one
visualize the impact of SHW error on the land
profile (cumulative elevation distribution)
assumed in the calculations. Each of the four
profiles has the same shape in Figure 1.3.3 as it
has in Figure 1.3.2. When measured against
NGVD (Figure 1.3.2), the three high-contour
error profiles start at different elevations
(reflecting uncertainty about the elevation of the
lowest spot of dry land, SHW) but coincide after
the first contour (because SHW error has no
impact on the topographic contours). When
measured against SHW (Figure 1.3.3), the
profiles all start out at zero, because error in
estimating SHW has no impact on the
definitional assumption that dry land extends
down to SHW. But the profiles diverge because
errors in SHW have a 1:1 impact on elevations
measured relative to SHW. Whatever the true
elevation of the 5-ft contour relative to
NGVD29, overestimating SHW by 1 foot lowers
the estimated elevation relative to SHW by 1
foot.10
"The error of elevations relative to spring high water
would be 1 foot greater if the red dot (in Figure 1.3.2) was
Solid lines: No SHW error or all three SHW error estimates coincide
Dashed lines: SHW error compounds contour error (relative to SHW)
Dotted lines: SHW error offsets contour error (relative to SHW)
5ft
SHW
Green dots represent observation from the maps; Green Line represents interpolated central estimate
Red dots represent positive contour error or negative SHW error
Black dots represent negative contour error or positive SHW error
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[76 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
All the figures show the implications of errors in
spring high water and elevation estimates. There
is no reason to think that these errors are
correlated and every reason to assume that they
are independent: two different federal agencies
(USGS and NOAA) compiled the underlying
data.11 Therefore, when calculating uncertainty,
we should assume that these errors are
independent. It follows that the total elevation
error is calculated as the square root of the sum
of squares. Thus, in areas where the contour
error is significant, the error in spring high water
makes very little difference. But in areas with
precise elevation data, error in spring high water
can account for about one-half the total error.
Figure 1.3.4 presents a story similar to Figure
1.3.2 but for the low elevation case. The story is
not completely symmetrical because of the first
contour. The contour interval of the USGS maps
at this location is 5 feet; but it is almost
impossible for the USGS contour to have
overestimated the actual elevations by 2.5 feet.
Substantial dry land ("area below 1st contour") is
above SHW (approximately 3 feet NGVD) and
below the first contour. If the low elevation
estimate were to assume that the lowest contour
is at 2.5 feet, there would be an impossible
result: the land above SHW (3 feet) cannot also
be below 2.5 feet. This analysis avoids such an
anomaly by assuming that RMS error is one-half
the actual contour interval used. Thus, if SHW is
between 2 and 4 feet, the lowest contour interval
is 1 to 3 feet; so the low case assumes that the
lowest contour is between 3.5 and 4.5 feet above
NGVD (depending on the error in estimating
SHW) rather than at 2.5 feet.
Although map accuracy standards provide a
basis for the contour-error assumption, the
literature does not provide a good estimate of
uncertainty for SHW. This exposition has looked
at the case where the error in SHW is 1 foot,
because whole numbers can help simplify
numerical illustrations. Our final results,
however, assume that uncertainty for spring high
water is approximately 15 cm (6 inches). Section
1.1 suggests that error is likely to be less than 6
inches, pointing out that the estimates are based
on interpolation of spring tide ranges from more
than 750 sites, and that the variation from site to
site tends to be about 5 cm (2 to 3 inches), or
less. Within a given quad—the unit of analysis
for this study—those errors should cancel to
some extent, causing the error to be less.
Using an Error Function to Represent Low
and High Cumulative Distributions
The previous discussion explains the low and
high estimates as alternative possibilities for the
average shore profile, given the points along the
profile for which observations are available. That
is, the discussion compared the "best guess"
profile estimated by Titus and Wang, with
proposed high and low profiles. Recall, however,
that although one usually displays y = f(x), in
this case, the argument of the function is shown
on the vertical axis. That is, in Section 1.1, Titus
and Wang estimated the area as a function of
elevation. Similarly, this study needs to estimate
the low and high estimates as a function of
elevation.
For computational purposes, it may be useful to
think of error as a function of the best-guess
central estimate. Viewed together, Sections 1.1
and Section 1.2 estimate the area of land within
each shore protection category within each quad
by 0.1-ft elevation increments. Thus, if one can
express low = f(central estimate) and high =
g(central estimate), then one need merely assign
low and high elevations to each area. That is:
A_loWik.low.f(E) = Aik,E
A_highik.high.g(E) — A;k_E
the actual value, and 1 foot less if the black dot was the
actual value.
11 The Section 1.1 estimates of spring high water are based
entirely on NOAA tidal observations and NOAA analysis
relating mean sea level to the fixed reference elevations
used by topographic data (i.e., NAVD88 and NGVD29).
-------
[ SECTION 1 .3 77 ]
Note: H(A1_low) = contour - k*(contour-SHW),
where k represents the ratio of RMS error to contour H(A1_lowest) = contour - k*(contour-SHWH) H(A1_bitlow) = contour - k*(contour-SHWL)
Interval, typically 1/2 SHWH=SHW-SHW_error SHWL=SHW+SHW_error
Figure 1.3.5. High and Low Estimates as a Function of the Best Guess. The difference between the
red line and the green is the high vertical error; the difference between the black line and the green is the
low vertical error. High error is constant beyond the first contour; low error is constant beyond the second
contour. The vertical scale of this drawing is exaggerated below one contour to better display the
relationships at low elevations.
where Ay,E represents the area of land in the ith
shore protection category in the kthUSGS quad
at elevation E, as estimated in Section 1.212; f
and g are the error functions that express low and
high elevation estimates as a function of the
central estimate of elevation, and A low and
A high represent the areas of land at elevation E
in the low and high elevation cases. Figure 1.3.5
shows the low and high elevations as a function
of the central estimate of elevation, i.e., functions
f and g.
Refinements
Our initial model has two important flaws: it
assumes that precision in modeling a single point
is the same as our precision in estimating the
total, and it ignores the model error of our linear
"Jones and Wang overlaid the elevation data from Titus
and Wang with the shore protection likelihood maps from
an unpublished analysis to create cumulative elevation
distribution functions for each of the shore protection
categories. In effect, they subdivided the cumulative
elevation distribution functions estimated by Titus and
Wang, into the separate cumulative distribution functions
for the different categories of likelihood of shore
protection. Thus, all the uncertainties we analyze here
result from the Titus and Wang analysis; but the actual
input data came from Jones and Wang.
interpolation. Let us examine each of these
issues.
Systematic and random error. Intuitively, one
might assume that the precision with which one
can reasonably estimate the area of vulnerable
land is the same as the precision of the input
data. But that is true only if all errors are
perfectly correlated. If we think that all
elevations are likely to have been over- or
underestimated by the same amount, then the
ability to estimate the total is no more precise
than the ability to estimate the elevation of a
particular location. In such a case, there is no
random error; all error is systematic. But that
should rarely be the case.
Most elevation estimates include both a random
and a systematic component. Along the contour,
random errors would be expected as a human
being attempts to trace a contour while viewing
aerial photographs through a stereoplotter;
systematic error might occur through biases
caused by settings in the instrumentation or by
subsiding benchmark elevations. Between the
contours, systematic errors are likely because the
actual "lay of the land" often departs from what
one would expect from a linear interpolation. In
developed areas, people have often filled and
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[78 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
bulkheaded the shore, increasing the amount of
land 50-100 cm above the tides at the expense of
land 0-50 cm above the tides; in undeveloped
areas bluffs occur in some areas, and the land
follows a more gentle slope in other areas.
A sophisticated treatment of this question is
beyond our time and budget constraints.
Therefore, we need a simple parameterization.
Figures 1.3.6 compares the cumulative elevation
distributions of LIDAR collected by the state of
Maryland (see Section 1.1, Jones 2007, and
Jones et al. 2008 for additional details) to the
interpolated results for the area on the Eastern
Shore of Maryland where LIDAR was available
(see Figure 1.3.1), subdivided into four subareas
with varying data quality. The vertical axes omit
magnitudes, which are unimportant for the
purposes here.
The four figures all suggest that systematic error
is well less than one-half the contour interval. In
the areas with a 5-ft contour interval (Figure
1.3.6a), the DEM interpolation is about 1 foot
lower (to the left) than the LIDAR below 3 feet;
but above 4 feet the interpolation and LIDAR are
less than 0.5 feet (15 cm) apart. In the areas with
a 1-m contour (Figure 1.3.6b), the DEM
interpolation and LIDAR are less than 10 cm (4
inches) apart below 1 meter. Above that point,
the DEM interpolation increases to 50 cm greater
than the LIDAR, but the difference is generally
25 cm. In the area that used the Maryland DNR
data—which have an RMS error of 5 feet—the
difference is less than 1 foot (30 cm) below the
10-ft contour (Figure 1.3.6c). It increases to 2.5
feet at the 15-ft contour before declining. In
those areas that rely on USGS 20-ft contours
(Figure 1.3.6d), the DEM underestimates the
elevation by 2 to 3 feet, on average.
These comparisons (as well as the comparison
with North Carolina LIDAR reported by Jones
[2007] and Section 1.1.) lead to two insights
worth applying in this error assessment. First, in
areas the size of a county or two, the cumulative
elevation distribution is within one-half the
nominal RMS error of the data most of the time;
and it almost never exceeds the reported RMS
error. Therefore, one would expect that when
there are many counties (e.g. results for entire
states), the cumulative elevation distribution
would continue to converge and almost never
exceed one-half the nominal RMS error of the
data set. That is, it seems safe to assume that the
systematic error over a large area is no more
than one-half the reported RMS error of the
data. Therefore, this error assessment assumes
that when USGS maps are the input data set, the
low and high estimates are one-quarter the
contour below and above the central estimates
derived by interpolating between those contours
in Section 1.2. that the high error may be greater
than the low error, as displayed in Figures 1.3.2
and 1.3.4.
Model error from linear interpolation. The
potential for linear interpolation to understate
elevations appears to be particularly pronounced
at very low elevations. The approach described
so far assumes, in effect, that below the first
contour, error is proportional to elevation
(relative to SHW). But there is no reason to
assume that precision increases at low
elevations; that was simply an artifact of linear
interpolation in a scheme designed to prevent
assuming the impossible, such as dry land being
below spring high water. These assumptions
seem more defensible on the low end than on the
high end. That is, assuming that the area of land
below elevation X is proportional to X below the
first contour is more unreasonable for the high-
elevation uncertainty than the low-elevation
uncertainty:
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[ SECTION 1 .3 79 ]
Elevation (cm)
Elevation (ft) NGVD
Figure 1.3.6. Cumulative Area of Land Close to Sea Level according to USGS National Elevation Data
(NED), interpolation of the Titus and Wang DEM, and State of Maryland's LIDAR in the area where LIDAR
was available (see Figure 1.3.1). The data are divided according to the best available data other than
LIDAR: (a) USGS maps with 5- ft contours; (b) USGS maps with 1 meter contours, (c) 5-foot contours
created from MD-DNR data in areas where USGS maps had 20-ft contours; and (d) USGS 20-ft contours.
See Section 1.1 and accompanying metadata for more details.
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[80 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
MD DNR Data (nominal 5-ft)
(/) 25000
0)
¦NED
¦DEM Interpolate
¦Lidar
0 2 4 6 8 10 12 14 16 18 20 22 24
Elevation (ft) NGVD
2500
2000
(/>
0)
USGS 20-ft Contour
re 1500
o
0)
CO
0)
1000
500
NED
DEM Interpolate
Lidar
4 6 8 10 12 14 16 18 20 22 24
Elevation (NGVD ft)
Figure 1.3.6. Cumulative Area of Land Close to Sea Level according to USGS National Elevation Data
(NED), interpolation of the Titus and Wang DEM, and State of Maryland's LIDAR in the area where LIDAR
was available (see Figure 1.3.1). The data are divided according to the best available data other than
LIDAR: (a) USGS maps with 5- ft contours; (b) USGS maps with 1 meter contours, (c) 5-foot contours
created from MD-DNR data in areas where USGS maps had 20-ft contours; and (d) USGS 20-ft contours.
See Section 1.1 and accompanying metadata for more details.
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[ SECTION 1 .3 81 ]
Second, the tendency for the DEM interpolation
to underestimate elevations appears to be
somewhat more pronounced than any tendency
to overestimate elevations. In Maryland this is
clearly the case. (Titus and Wang, and Jones,
found that in North Carolina, the interpolation
overestimated elevations of very low land; but
they concluded that the unique situation of North
Carolina was probably to blame in that case.13)
That tends to reinforce our inclination to assume
• The wetlands boundary is at the kink of the
most common concave-up profile. So the use
of wetlands data means that interpolation
already accounts for cases where the profile
is below a linear trend.
• The accuracy assessment shows the Section
1.1 DEM to underestimate elevations close to
spring high water (see Figure 1.3.6):
- In Maryland, they generally found that
more than half of the land between spring
high water and the first contour was
above the midpoint between spring high
water and the elevation of the first
contour.
- The error was particularly great when the
contour interval was large.
• USGS contour selection also creates a
downward bias: Consider an area with a 10-ft
contour. If there is much land below the 5-ft
contour, USGS is likely to reduce the contour
interval to 5 feet or at least collect a 5-ft
supplemental contour. This does not always
occur, but the tendency is enough for a high-
elevation scenario to assume that there is no
land below the 2.5-ft contour.
13Much of North Carolinas coastal wetlands are truly are
classified as nontidal wetlands, and hence the
interpolations in Section 1.1 treated them as uniformly
distributed between SHW and the 5-ft contour, which is
generally more than 1 meter above SHW. (The final results
used LIDAR and hence are not affected directly by this
problem.) Much of those wetlands are at sea level, and
classified as nontidal because the rivers and sounds along
which they are found have an astronomical tide so small
that, for most practical purposes, it is nontidal. When
considering the impact of sea level rise, it would be more
accurate to consider these areas to be "nanotidal wetlands."
• The mathematics limits downside
uncertainty: Because elevations must be
above spring high water, they can only be a
little bit less than the very low elevations
under consideration, while they could be
much higher.
Thus, if the point estimate assumes 100 hectares
within 0.5 feet above spring high water, it is
desirable that the low estimate does not assume
100 hectares to be 2 feet below spring high
water. That does not mean, however, that the
high estimate ought to rule out the possibility
that this land is actually 3 feet above spring high
water. Low bluffs really are common along the
coast—so a high scenario that assumes a low
bluff with an elevation of contour/4 is actually
quite realistic. (By contrast, a high scenario that
assumes an unmapped dike protecting low land
that it contour/4 below spring high water is not
realistic.) Put another way, there is good reason
to not think that there is a large amount of dry
land below high tide—but there is no reason to
think that there is a significant amount of land
just above spring high water. Therefore, the high
scenario should allow for the possibility that
there is no significant amount land barely above
the tides.
Figure 1.3.6 supports this concern. In Figures
1.3.6a and 1.3.6c, the interpolation understates
elevations by about 1 foot below 4 feet in
elevation, and then declines. In Figure 1.3.6d,
where the underlying USGS maps have a 20-ft
contour interval, the interpolation finds as much
land below 3 feet as LIDAR finds below 5 feet,
and as much land below 17 feet as the LIDAR
finds below 20 feet. Thus, at an elevation of one-
quarter the contour interval, the error is about
two-thirds the error seen at the contour. (In
Figure 1.3.6b, the error is fairly minor at all
elevations.)
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[82 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Area below Area below Area below
1st contour 2*contour 3*contour
Green dots represent observation from the maps,
central estimate
Red dots: positive contour error
Black dots: negative contour error
Solid lines: No SHW error
Green Line represents interpolated
Figure 1.3.7. High Elevation Estimates Relative to Spring High Water, including Possible Model
Error (with and without SHW error, relative to NGVD, ignoring model error). This case assumes a 5-ft
contour interval, a 1 -ft error in estimating the elevation of SHW, a contour error of 2.5 feet, and a high-end
error that is always at least one-quarter the contour interval
There is no completely satisfactory way to model
this possibility. The simplest approach would
have been to simply add and subtract one-quarter
the contour interval to the entire distribution, but
this analysis employs a more complicated
approach in part to avoid impossible results in
the low case (e.g., dry land up to one-quarter the
contour interval below SHW). But this is not a
problem with the high scenario. Therefore, the
high scenario assumes that all land is at least
one-quarter times the contour interval above
SHW. In effect, the high estimate assumes that
one can not rule out a bluff with an elevation at
one-quarter the lowest contour interval.
Comparing Figure 1.3.7 to Figure 1.3.3 shows
that this assumption has no impact on elevations
above the first contour.
Areas with Higher Precision Data
In areas with higher precision data, these
considerations are less important. They mostly
apply to problems between contours; and EPA
does not need elevations in increments finer than
50 cm. What is important is that no matter how
precise the elevation data, we will report some
uncertainty because LIDAR measures elevations
relative to a fixed reference plane, while we
report elevations relative to spring high water,
which we estimate imprecisely. As mentioned
above, this analysis assumes that the estimates of
spring high water have an error of 15 cm (6
inches).
In Section 1.1, Titus and Wang used the LIDAR,
spot elevation, and actual DEM results where
contour intervals were 2 feet (60 cm) or less.
Therefore, the interpolation model did not apply
and it would be reasonable to simply add or
subtract the systematic error. We saved some
time, however, by applying the algorithm
developed for USGS data to these results as well
rather than rewriting a separate algorithm.
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Section 1.3.2. Implementing the Approach using
Geographically Specific Error Functions Approach
Author: Dave Cacela, Stratus Consulting Inc.
The objective of elevation uncertainty analyses is
to acknowledge uncertainty about the actual
elevation of any particular geographic region and
to quantify it so that the elevation in a particular
region can be expressed as a range of plausible
values. Consequently, estimates of flooded areas
under any particular scenario of sea level rise can
also be expressed as a range of plausible values.
This section reports the actual methods used to
calculate ranges of plausible elevation that
reflect the reasoning about landscapes,
interpretation of map accuracy, and between-
contour interpolation methods described in
Section 1.3.1. It is intended to describe the
essential features of methodology introduced in
Section 1.3.1 that were actually applied in the
uncertainty analysis in a manner that includes
specific mathematical definitions that allow for
reproducibility.
The reasoning in Section 1.3.1 about uncertainty
is described in terms of two generalized error
functions. One of the functions defines the lower
limit of plausible elevation and the other defines
the upper limit. Considered jointly, the error
functions define the amount of uncertainty about
elevation (vertical error) associated with any
geographic point. To quantify uncertainty in a
particular geographic location, the generalized
error functions are used with parameters that are
specific to that particular location to define
plausible ranges of elevation for that location.
Plausible ranges of elevation determine in this
manner are subsequently translated into plausible
ranges of area that may be inundated by various
sea level rise scenarios.
Magnitude of Uncertainty in the
Data Sources
Uncertainty analyses consider two main sources
of uncertainty. The analyses consider both types
of uncertainty jointly to generate an estimate of
total uncertainty that is specific to each
geographic area in the study.
One source of uncertainty derives from
imprecision in elevation values in the source
data. Each location in the study area is
represented by one of several types of source
data with differing amounts of inherent
precision. As described in Section 1.3.1, the
inherent precision of each type of source data is a
known value that is expressed as the root mean
square error (RMSE) and in the same units of
measure as the vertical units provided (Table
1.3.1). Data with greater inherent precision have
less uncertainty with regard to the true elevation
of a particular geographic point and, conversely,
source data with lesser inherent precision have
more uncertainty with regard to the true
elevation of a particular point. (See Figure 1.3.8
and Table 1.3.1; and Section 1.1 and Section 1.2
for additional details concerning the precision of
the source data used in the study area.)
The second source of uncertainty derives from
the estimated elevation of SHW relative to the
NGVD29 for any particular section of coastline
as derived from local tide gage data. The
elevation of SHW is relevant because the
elevations provided by the source data are
expressed relative to the NGVD29 datum, but
the estimation of inundation is expressed relative
to SHW (see Section 1.1 for a description of how
the elevations relative to SHW were derived).
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[84 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Aggregate Uncertainty
All NGVD29 elevations from the source data are
converted to elevations relative to SHW by:
Ejk = Engvdjk - SHWk (1)
where:
Ejk is the derived nominal elevation of point j
in region k relative to SHW
Engvdjk is the nominal elevation of point j in
region k relative to NGVD29, as provided in
the source data
SHWk is the estimated (NGVD29) elevation
of SHW for region k.
SHWk is not known with absolute certainty; thus
the precision of Ejk is a function of two sources
of uncertainty: (1) the magnitude of uncertainty
inherent in Engvd,jk and (2) the magnitude of
uncertainty in SHWk. In principle, the magnitude
of uncertainty in SHWk could vary by region k,
but in this study SHWk is defined as a constant
value of 0.5 feet. These two sources of
uncertainty were assumed to be statistically
independent; thus, the magnitude of total
uncertainty is estimated with the basic equation:
jk '
P' --l/Pmshw,k +Pngviik (^)
where:
Pmshw.k is the magnitude of uncertainty in
SHWk expressed as RMSE, defined as a
constant value of 0.5 feet
Pngvd.jk ^Cjk Or
Pngvd.jk is a specified the magnitude of
uncertainty in Engvd.jk expressed as RMSE
(feet)14
Pjk is the magnitude of total effective
uncertainty in Ejk (feet)
14For areas described by some types of source data, e.g.,
USGS topographic maps, Pngv4jk is defined as a certain
fraction of the contour intervals used in the base maps, but
for other types of source elevation data not based on
contour intervals, e.g., elevations derived from LIDAR
data, Pngvdjk is a constant (Table 1.3.1). For USGS maps,
P i ig\ ¦- i.j i kC.
Cjk is the magnitude of contour intervals
represented in the relevant source data for
point j,k15
A- is a scalar that varies by source data (e.g.,
0.5; see Table 1.3.1).
(1)
The basic definition of Pjk was not applied
universally to all points in region k. In some
subregions within region k, Pjkis associated with
points j,k, but in other subregions, particularly
regions of low elevation, Pjkis redefined by an ad
hoc function of Ejk that is described below.
Estimating Elevation Uncertainty
The magnitude of uncertainty about Ejk was
defined as Pjk at all relatively high elevations. In
such regions, upper and lower bounds on Ejk
were defined simply as:
Ejki = Ejk-Pjk (3)
Ejku = Ejk + Pjk (4)
where:
Ejk is the nominal elevation of point j,k 16
Ejki and Ejk.u represent the lower and upper
bounds on Ejk, respectively.
However, the simple formulations in Eqult&bns 3
and 4 were considered inadequate for providing
realistic bounds for Ejk in locations with low
elevation, where "low elevations" are defined to
be lower than selected reference elevations. For
estimating Ejku, a reference elevation was taken
to be E'jk , the elevation of "first contour," which
is Ejk corresponding toE„gvd,jk equal to the lowest
nonzero elevation contour in the source data for
region k. For estimating Ejk.i, an additional
reference elevation was taken to beE"jk, the
elevation of "second contour," which is Ejk
corresponding to Engvd.jk equal to the second-
lowest nonzero elevation contour in the source
data for region k.
"For source data not based on a contour interval, such as
SPOT and LIDAR, contour interval was derived from the
RMSE of the source data.
" Nominal elevations were determined from the source
data using interpolation methods described in Section 1.1.
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[ SECTION 1 .3 85 ]
The general uncertainty modeling procedure can
be succinctly described as two complex error
functions. One such function describes the error
in a positive direction, i.e., the amount by which
the "true" elevation, E*jk, could exceed the
nominal elevation Ejk. The other such function
describes the error in a negative direction, i.e.,
the amount by which the "true" elevation, E*jk,
E'jk =(Cjk -MSWHk)
P
]k,u
'jk
gE
jk
jk ¦
J'k
jk
E =E + P
Ljk,u Ljk jk,u
could lie below the nominal elevation Ejk. The
functions are asymmetrical because of the
assumption that the magnitude of errors in the
negative direction will tend to be relatively
dampened if Ejk is lower than E'jk or E"jk
(defined below; see Section 1.3.1 for the
justification of this assumption).
The error function for determining an upper
bound on Ejkis a set of line segments defined as:
(5)
(6)
(?)
IfE]kE]k
where:
SHW is the elevation of mean spring high water for point j,k
gis a constant (e.g., 0.25)
E'jk is the elevation (relative to SHW) of "first contour"
Pjk.u is the magnitude of error in a positive direction
Ejk,u is the upper bound on Ejk-
The error function for determining a lower bound on Ejkis a set of line segments defined by:
E"jk=(2Cjk-MSWHk)
P' =
r Jk
P/A-j -
P' F
r jk jk
P'
mshwr+(*E'Jky
EV-
jk
((E]k-Wlk)(?lk-V'lk))/ (E"lk-Wlk)
jk'' ' jk
jk;
jk
' jk '
jk
If v., >Qand\:... H' ; andY., .. Y.",
//ejA->ev
(8)
(9)
(10)
E jk j = max (0, (Ejk - Pjk j)) (11)
where:
P'jk is a measure of uncertainty analogous to Pjk
E"jk is Ejk corresponding to E"ngvdjk, the elevation of the second-lowest non-zero elevation
contour in the base map for region k
Pjkj is the magnitude of error in a negative direction
Ejk,i is the lower bound on Ejk-
The typical shape of the error functions defined by Equations 1 through 11 are depicted in Figure
1.3.8.
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[86 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
(a)
Nominal Elevation (above MSHW)
(b)
Nominal Elevation (above MSHW)
(c)
0 E'jk E"jk
Nominal Elevation (above MSHW)
Figure 1.3.8. Generalized Error Functions Used to Estimate Uncertainty Bounds on Elevation.
Panel (a) depicts magnitude of uncertainty in a positive direction; panel (b) depicts magnitude of
uncertainty in a negative direction; and panel (c) describes the net effect of the functions depicted in
panels (a) and (b), expressed as positive and negative uncertainty bounds relative to the nominal
elevation.
-------
[ SECTION 1 .3 87 ]
Estimating Ranges of Plausible
Elevation
Before the uncertainty analyses, acreages for a
particular region and protection scenario were
compiled into bins corresponding to elevations
above SHW 0.1-ft increments.17 For example, for
scenarios,
Ak.s.o.i = area between Ejk = 0 feet andEjk = 0.1
foot (hectares)
Ak.s.o.2= area between Ejk= 0.1 feet and Ejk=
0.2 foot (hectares), etc.
Thus, collectively the Ak.s values can be
considered as a density18 with each element
associated with a particular Ejk- Considering the
meaning of Ejk.i and Ejk.u, each Ak,s can be
associated with all three values: Ejk, Ejk.i, and
Ejk.u. By extension, each Ejk elevation can be
associated with three alternative values of Ak,s by
aligning with cases where Ejk = Ejk,i and Ejk =
Ejk,u. In this manner, two additional "densities"
are generated such that for each Ejk there are
three alternative corresponding Ak.s. The
alternative densities have little implicit meaning,
but converting each of the alternative densities to
cumulative distributions provides alternative
elevation profiles that are meaningful for
generating a range of estimates of total flooded
area under various amounts of sea level rise.
Procedural Notes
Data processing and calculations related to the
elevation uncertainty analyses were conducted
with S-Plus software (Professional Developer
version 7; Insightful Corporation, Seattle, WA).
In addition to quality control procedures used
during development of the S-Plus algorithms
used to solve for the uncertainty endpoints,
quality control procedures were conducted
independently from the S-Plus algorithms using
MS-Excel spreadsheets for selected test cases.
17The data used as the basis for the uncertainty analyses
were expressed with a resolution of 0.1 feet (see footnote
14), and the general processing of those data to develop
uncertainty limits were conducted with a resolution of 0.1
feet. Prior to comparisons with elevations of interest (e.g.,
a selected amount of sea level rise), the basic results with
0.1 foot resolution were further subdivided into 10 bins of
equal size to provide a quasi-resolution of 0.01 feet.
18Not strictly a probability density because the sum of all
Hk,s equal a total area in region k for scenarios, not one.
-------
[88 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[ SECTION 1 .3 89 ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[90 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[ SECTION 1 .3 91 ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[92 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[ SECTION 1 .3 93 ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[94 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
NJ Perth Amboy Middlesex 20 ft 20 0.5 0.25 304.8 4.07
-------
[ SECTION 1 .3 95 ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
NY New London Suffolk 10 ft 10 0.5 0.25 152.4 2.15
-------
[96 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
VA Chincoteague East Accomack 5 ft 5 0.5 0.25 76.2 2.81
OeS
VA Chincoteague West Accomack 5 ft 5 0.5 0.25 76.2 1.71
VA Cobb Island Northampton 5 ft 5 0.5 0.25 76.2 2.84
VA Courtland Southampton 5 ft 5 0.5 0.25 76.2 1.7
-------
[ SECTION 1 .3 97 ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
-------
[98 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
VA King and Queen Court King and Queen 10 ft 10 0.5 0.25 152.4 2.98
House
VA Machodoc Westmoreland 10 ft 10 0.5 0.25 152.4 1.61
-------
[ SECTION 1 .3 99 ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
VA Rappahannock Caroline 10 ft 10 0.5 0.25 152.4 2.56
Academy
-------
[ 100 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table 1.3.1. Features of distinct base map data sources related to estimation of elevation uncertainty
Contour
RMS
interval
k
cm
SHW
State
Quadrangle
County
Source
(ft)
(base)3 g
(base)
(ft)b
VA Zuni Isle of Wight 10 ft 10 0.5 0.25 152.4 1.76
a. The values of k listed here are the "base" value of k that relates contour interval to RMS as RMS = k(base) H
contour interval. The procedures for conducting uncertainty analyses allow for universal rescaling of k. These
values were scaled by a factor of 0.5 in the analysis; i.e., we assume that error = 0.25 times the contour
interval in most quads.
b. For these locations, the values of 1 for contour interval and 0 for SHW were provided to trick the algorithm
into calculating "contour error" as RMSE/2. This was necessary because of the format in which Jones and
Wang had saved the central estimate results for those areas with high precision data. The value of g doe not
matter because g had no effect above the contour interval, which is less than the 50 cm increment with
which our results are reported.
c. For these locations, the values of 2 for contour interval and 0 for SHW were provided to trick the algorithm
into calculating "contour error" as RMSE/2. This was necessary because of the format in which Jones and
Wang had saved the central estimate results for those areas with high precision data.
-------
Section 1.3.3. Results Author: James G. Titus
The results from this section are displayed in
Appendices A, B, and C (along with regional
summaries). What we call ''low" and
"high "(elevation) as we explain oar approach in
this section are reversed in the tables, because
the high elevation means less vulnerability and a
lower area close to sea level, and vice versa.
We encourage the reader to examine these tables
and think about both the ratio of the high to the
low estimate and the vertical error implied by a
given line in the table. If the high estimate at 50
cm is greater than the low estimate for 100 cm,
then the vertical error is greater than 25 cm. If
the high estimate at 50 cm is greater than the low
estimate for 150 cm, then the vertical error is
greater than 50 cm.
If the ratio of high to low at 50 cm is great, that
may mean that the uncertainty is great; but it
may also mean that there is an inflection point
nearby. For example, if the data (e.g., LIDAR)
show several times as much land between 50 and
65 cm as between 0 and 50 cm, then even if the
error is only 15 cm, the ratio of high to low could
be very large.19 This happens in some areas with
LIDAR. As a result, if one considers only the
ratio of high to low, one might be surprised that
the areas with LIDAR do not always seem much
more precise than the areas that relied on USGS
5-ft contours. (A second reason that the LIDAR
does not always appear more precise than areas
with 5-ft contours is that the first contour interval
is only 2-3 feet in areas where spring high water
is 2-3 feet above NGVD29. Although the
subsequent contour intervals are greater, the
ratios of high to low get closer to 1 as elevations
19For example, if the LIDAR shows 10 ha between 0 and
50, and 100 ha between 50 and 65, if error is 15 cm, the
high estimate would be 110 ha, and the low estimate would
be less than 10. The ratio of high to low would this be
more than 11.
increase.) Nevertheless, variations in precision
are palpable when one looks at areas with a 10-
or 20-ft contour interval. See the Pennsylvania
tables in Appendix A, where Bucks County has
mostly 20-ft contours but Philadelphia has 2-ft
contours.
Overall, we estimate between 2,374 and 3,221
square kilometers of land within 50 cm above the
tides, and 3,351 to 3,940 square kilometers
within 1 meter above the tides in the middle
Atlantic (see Appendix C). Our input data and
assumptions are based on RMS error; but at the
state and regionwide level, much of the errors
should cancel. The true amount of land close to
sea level is very likely to fall within the ranges
we have estimated.
One final warning: The available output
provided by Jones and Wang (explained in
Section 1.2), which this effort used as input,
extended only to an elevation of 20 feet above
SHW. Therefore, we cannot literally apply our
formula for the high-elevation (low-area) case
for elevations above 20 feet minus "error." In
cases with a 20-ft contour interval, error is 5 feet;
so we cannot apply the low-area formula above
15 feet. The algorithm explained in Section 1.3.2
treats no data as zero, assuming in effect that
there is no land above 20-ft SHW. We
considered suppressing all calculations above 4.5
meters in such cases, but opted instead to
provide the results with an asterisk. That
approach seems more reasonable: In these cases,
assuming that there is no land above 20-ft SHW
is clearly an extreme lower bound. But we doubt
that it seriously distorts the statewide results.
Typically, a state has only a few quads with a 20-
ft contour interval—generally in areas that have
very little low land. So even if we had been able
to correctly apply our formula (i.e., if Jones and
Wang in Section 1.2 had interpolated above 20-ft
SHW) the calculated area would not be much
-------
[ 102 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
greater than zero when considered at the
statewide level. Thus, instead of suppressing our
"low area" estimate, we provide an estimate that
is slightly lower than a rigorous application of
our approach.
References
Bureau of the Budget. 1947. National Map
Accuracy Standards. Government Printing
Office, Washington D.C. Available from:
http://rockyweb.cr.usgs.gov/nmpstds/nmas.html.
Accessed October 1, 2006.
Environmental Protection Agency. 1989. The
Potential Effects of Global Climate Change on
the United States. Report to Congress. EPA-230-
05-89-050. U.S. EPA, Washington, D.C.
Jones, R. 2007. Accuracy Assessment of EPA
Digital Elevation Model Results. Memorandum
and attached spreadsheets prepared for the U.S.
EPA under Work Assignment 409 of EPA
Contract #68-W-02-027. Distributed with the
elevation data.
Jones, R., J. Titus, and J. Wang. 2008. Metadata
for Elevations of Lands Close to Sea Level in the
Middle Atlantic Region of the United States.
Metadata accompanying Digital Elevation Model
data set. Distributed with the elevation data.
Park, R.A., M.S. Treehan, P.W. Mausel, and
R.C. Howe. 1989. The effects of sea level rise on
U.S. coastal wetlands. In The Potential Effects of
Global Climate Change on the United States.
EPA-230-05-89-050. U.S. EPA, Washington,
DC.
Titus, J.G., AND M.S. Greene. 1989. An
overview of the nationwide impacts of sea level
rise. In The Potential Effects of Global Climate
Change on the United States. Report to
Congress. Appendix B: Sea Level Rise. EPA-
230-05-89-052.U.S. EPA, Washington, DC.
-------
Appendix A
Low and High Estimates of the Area of Land Close to Sea Level, by State3
(square kilometers)
al_ow and high are an uncertainty range based on the contour interval and/or stated root mean square error (RMSE)
of the input elevation data. Calculations assume that half of the RMSE is random error and
half is systematic error. For a discussion of these calculations, see Section 1.3 of this report.
-------
[ 104 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table A.1 Low and High Estimates of the Area of Land Close to Sea Level in New York
This value is probably too low because of a data limitation. See Section 1.3 of this report.
Note: A peer reviewer noticed that the draft maps showed Gardiners Island as "likely" even though the text said that it had been changed to "unlikely". The effect of that error was to
overstate the area of land below one meter where shore protection is likely, and understate the area where shore protection is unlikely, by 0.7, 0.9, and 1.1 square miles for the land
within 50, 100, and 200 cm above spring high water. We corrected the maps, but not the quantitative results in this report.
-------
[ SECTION 1.3 105 ]
Table A.2 Low and High Estimates of the Area of Land Close to Sea Level in New Jersey
Meters above Spring High Water
low high low high low high low high low high low high low high low high low high low high
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
probably too low because of a data limitation. See Section 1.3 of this report.
-------
[ 106 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table A.2 Low and High Estimates of the Area of Land Close to Sea Level in New Jersey (continued)
This value is probably too low because of a data limitation. See Section 1.3 of this report.
-------
[ SECTION 1.3 107 ]
Table A.3 Low and High Estimates of the Area of Land Close to Sea Level in Pennsylvania
This value is probably too low because of a data limitation. See Section 1.3 of this report
-------
[ 108 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table A.4 Low and High Estimates of the Area of Land Close to Sea Level in Delaware
-------
[ SECTION 1.3 109 ]
Table A.5 Low and High Estimates of the Area of Land Close to Sea Level in Maryland
Meters
above Spring High Water
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
County
0
.5
1
0
1
5
2
0
2.5
3.0
3.5
4.G
4.
5
5.
0
--Cumulative
(total) amount
of Dry Land below a given elevation-
Anne Arundel
1.7
7.2
6.7
15
12
26
20
39
32
50
44
59
54
68
63
77
72
86
81
94
Baltimore County
2.3
6.6
7.3
13
14
20
21
27
28
36
37
46
47
56
57
65
66
73
75
81
Baltimore City
0.2
2.1
0.9
3.9
1.7
5.7
2.7
7.5
4.2
9.7
5.7
12
7.4
14
9.6
17
12
19
14
21
Calvert
0.4
3.9
1.7
5.8
3.1
7.6
4.6
10
6.1
14
7.6
17
10.0
21
14
26
17
31
21
36
Caroline
0.7
3.2
2.2
6.1
4.1
9.2
6.9
13
9.9
16
13
20
16
23
19
27
23
30*
26
33*
Cecil
0.2
2.5
1.0
5.2
1.8
7.9
3.7
12
5.7
16
7.8
20
11
25
16
29
20
34
24
38
Charles
0.7
12
4.8
21
9.0
30
15
40
22
53
30
67
40
77
53
85
66
93
77
99
Dorchester
30
120
150
215
231
269
282
313
322
348
358
386
396
416
423
439
445
457
462
474
Harford
0.7
17
7.6
25
15
33
22
40
28
49
34
57
42
64
50
69
59
74
65
78
Howard
0
0.01
0.01
0.03
0.01
0.05
0.02
0.07
0.04
0.1
0.05
0.14
0.07
0.2
0.1
0.2
0.1
0.3
0.2
0.3
Kent
0.2
8.4
4.8
16
10
23
16
33
23
45
29
56
37
68
48
80
59
93
71
105
Prince George's
0.2
2.2
0.9
3.9
1.6
5.6
2.9
7.2
4.3
8.9
5.6
11
7.1
13
8.9
16
11
19
13
21
Queen Anne's
0.6
4.1
5.3
12
14
22
24
35
37
50
52
68
69
88
89
107
107
126
125
143
Somerset
17
58
70
101
113
153
168
193
198
210
215
233
240
260
268
289
297
318
327
345
St. Mary's
2.4
16
8.0
28
14
41
24
58
35
79
46
101
62
118
83
129
104
139
120
148
Talbot
2.2
7.8
11
24
30
54
64
99
110
139
149
175
184
210
218
239
245
260
266
279
Wicomico
5.0
15
18
29
32
43
47
58
62
72
76
86
90
101
105
115
119
129
133
142
Worcester
4.4
21
25
48
53
83
88
119
124
153
158
183
187
209
213
235
239
261
265
288
Statewide
69
307
326
570
560
832
812
1104
1053
1350
1267
1596
1500
1833
1737
2045
1960
2243*
2165
2425*
This value is probably too low because of a data limitation. See Section 1.3 of this report
-------
[ 110 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table A.5 Low and High Estimates of the Area of Land Close to Sea Level in Maryland (continued)
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high I
County
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Wetlands
Tidal
Cumulative (total) amount of Nontidal Wetlands below a given elevation
Anne Arundel
12
0.2
0.7
0.6
1.6
1.1
4.8
3.1
8.1
6.3
11
9.5
12
12
14
13
15
14
16
15
17
Baltimore County
10
0.1
0.3
0.3
0.7
0.7
1.0
1.0
1.3
1.3
1.5
1.5
1.7
1.7
1.8
1.8
2.0
2.0
2.2
2.2
2.3
Baltimore City
0.2
<0.01
0.03
0.01
0.04
0.02
0.05
0.03
0.1
0.04
0.1
0.05
0.1
0.06
0.1
0.06
0.1
0.07
0.1
0.08
0.1
Calvert
15
0.1
0.9
0.4
1.3
0.7
1.7
1.1
2.2
1.4
3.0
1.7
3.8
2.2
4.7
3.0
5.7
3.8
6.6
4.7
7.5
Caroline
14
0.3
1.4
0.7
2.6
1.3
4.0
2.5
5.3
3.5
6.4
4.4
7.5
5.3
8.6
6.2
9.8
7.1
11*
8.0
12*
Cecil
13
0.01
0.2
0.04
0.7
0.1
1.2
0.4
1.7
0.8
2.3
1.2
2.8
1.7
3.5
2.2
4.2
2.8
4.9
3.5
5.5
Charles
24
0.1
3.8
1.5
6.5
2.9
9.2
4.8
12
7.0
14
9.3
16
12
18
14
20
16
21
18
23
Dorchester
425
15
46
53
70
76
90
94
104
107
112
114
121
124
129
131
136
137
139
140
143
Harford
29
0.2
2.5
1.2
3.8
2.3
5.0
3.3
6.2
4.3
7.6
5.2
9.0
6.4
10
7.8
11
9.1
11
10
12
Howard
0
0
0.03
0.01
0.04
0.02
0.04
0.03
0.05
0.04
0.06
0.04
0.06
0.05
0.07
0.06
0.08
0.06
0.09
0.07
0.10
Kent
18
0.1
1.1
0.9
2.6
2.0
4.1
3.3
5.4
4.3
6.8
5.2
7.9
6.1
9.3
7.2
11
8.3
13
9.7
14
Prince George's
14
0.1
0.8
0.3
1.4
0.6
2.0
1.0
2.5
1.5
3.2
2.0
3.8
2.5
4.7
3.2
5.6
3.8
6.5
4.6
7.2
Queen Anne's
21
0.2
1.1
1.5
3.0
3.2
4.8
4.9
6.5
6.5
8.1
7.9
9.6
9.5
12
11
14
13
16
15
18
Somerset
265
6.6
16
17
21
23
31
35
40
41
43
45
52
54
60
62
69
71
78
81
90
St. Mary's
19
0.5
2.8
1.7
5.3
2.8
7.8
4.6
11
6.7
15
8.8
19
12
22
16
25
20
28
23
31
Talbot
26
0.1
0.3
0.5
1.0
1.3
2.1
2.5
4.2
4.8
6.2
6.8
8.5
9.1
12
13
15
16
17
18
20
Wicomico
67
5.4
9.9
11
13
16
22
24
29
30
35
37
44
47
54
56
60
62
66
67
70
Worcester
142
0.7
5.2
6.0
10
11
16
17
22
23
29
30
36
37
42
43
48
49
54
54
58
Statewide
1116
29
93
97
146
145
207
203
261
249
304
289
355
341
406
390
451
435
490*
474
531*
Cumulative (total) amount of land below a given elevation
Dry Land
69
307
326
570
560
832
812
1104
1053
1350
1267
1596
1500
1833
1737
2045
1960
2243*
2165
2425*
Nontidal Wetlands
29
93
97
146
145
207
203
261
249
304
289
355
341
406
390
451
435
490*
474
531*
All Land
1116
1214
1516
1539
1832
1820
2155
2130
2481
2418
2769
2672
3067
2957
3354
3243
3612
3510
3849*
3754
4071*
This value is probably too low because of a data limitation. See Section 1.3 of this report
-------
[ SECTION 1.3 111 ]
Table A.6 Low and High Estimates of the Area of Land Close to Sea Level in Washington, D.C.
-------
416
257
159
49
5
4
18
8.8
49
14
0.5
43
0.8
5.2
378
112
57
141
68
392
53
33
36
39
111
ES ASSOCIATED WITH EPA'S ESTIMATES ]
mates of the Area of Land Close to Sea Level in Virginia
low high low high low high
0.5 1.0 1.5
Meters above Spring High Water
low high low high low high low high
2.0 2.5 3.0 3.5
56 111
37 78
20
2.8
33
10
0.1 0.5
0.3 0.9
1.1 3.9
0.5 2
1.8 6.5
0.8 2.7
0.04 0.1
1.5 5.4
0.05 0.2
0.3 0.9
11 43
2.4 9.3
2.4 8.9
2.8 11
3.6
33
2
14
89
7.3
1.7 5.7
0.9 3.2
2 6.8
13 33
-Cumulative (total) amount of Dry Land below a given elevation-
93 159
65 115
29
6.3
44
15
0.3 0.7
0.6 1.3
2.5 5.9
1.2 3
4.1 9.9
1.7 4.2
0.1 0.2
3.3 8.1
0.1 0.3
0.6 1.3
27
5.7
5.5
6.9
8.5
66
14
13
17
21
66 139
4.6 11
3.7 8.6
2 4.8
4.4
26
11
50
137 204
98 149
39
9.7
55
20
0.5 1.3
0.9 1.7
3.8 7.6
1.9 3.9
6.4 14
2.7 5.4
0.1 0.2
5.2 11
0.2 0.3
0.9 1.8
42 92
9
8.7
11
14
21
18
24
28
108 190
7.1 15
5.5
3.1
7
41
12
8.4
14
67
180
131
49
13
0.6
1.2
5.2
2.6
8.7
3.6
0.2
7.1
0.2
1.2
58
12
12
15
19
149
9.7
7.5
4.2
10
55
243
172
71
25
1.9
2.1
9.2
4.7
20
6.8
0.3
16.7
0.4
2.3
141
37
25
44
35
230
22
15
13
19
76
221
160
61
17
0.8
1.5
6.6
3.3
11
4.6
0.2
9
0.3
1.5
74
16
15
19
24
186
12
9.6
5.4
13
67
279
192
87
29
2.6
2.5
11
5.5
26
8.1
0.3
22
0.5
2.8
190
53
32
64
42
268
28
19
18
23
84
258
180
78
21
1.4
1.8
8
4
15
5.7
0.3
12
0.3
1.9
100
24
20
27
29
220
17
13
9.6
16
75
315
211
104
34
3.3
2.9
12
6.3
31
9.4
0.4
27
0.5
3.3
239
69
38
84
48
307
34
22
22
27
93
294
200
94
25
2.1
2.2
9.5
4.8
20
6.9
0.3
17
0.4
2.4
147
39
26
46
36
258
22
16
14
20
84
-------
[ SECTION 1.3 113 ]
Table A.7 Low and High Estimates of the Area of Land Close to Sea Level in Virginia (continued)
low
C
high
1.5
low
1
high
.0
low high
1.5
low
high
2.0
low high
2.5
low high
3.0
low high
3.5
low high
4.0
low high
4.5
low high
5.0
Mathews
4.7
15
13
33
26
54
44
73
62
85
79
97
90
108
101
113
111
117
115
121
Hampton Roads
24
91
78
200
154
333
264
469
381
650
519
848
711
1045
907
1192
1089
1307
1215
1424
James City
0.1
3.8
2
7.2
4.7
11
7
14
9.4
18
12
22
15
26
19
30
23
34
27
39
York
1.4
6
5
13
9.9
21
16
28
23
33
28
37
33
42
38
45
42
48
44
51
Newport News
2.2
6.9
6
11
9.7
15
13
18
16
21
19
25
23
28
26
33
30
38
35
42
Poquoson
1.4
4.5
4
8.8
7.4
13
11
16
15
16
16
17
17
17
17
17
17
17
17
17
Hampton
1.9
5.9
5
18
13
32
25
45
38
60
51
74
65
88
80
93
90
98
95
102
Surry
0
1.4
1
2.7
1.7
4.1
2.7
5.3
3.6
6.2
4.6
7.1
5.5
8
6.4
9
7.2
9.9
8.1
11
Isle of Wight
0.2
3.4
2
6.2
4.2
9.1
6
12.8
8
17
10
22
14
26
18
31
22
35
27
42
Norfolk
1.9
5.8
5
17
13
30
24
42
35
67
52
91
77
115
101
120
118
124
122
128
Virginia Beach
9.3
33
30
69
55
117
94
163
138
219
185
273
241
327
295
368
347
393
378
418
Suffolk
0.7
4.3
3.1
7.1
5.4
10
7.5
15
10
23
13
31
21
39
28
50
37
60
47
73
Portsmouth
1.2
3.9
3.5
9.6
7.6
15
13
22
18
33
27
45
38
56
50
61
58
65
63
70
Chesapeake
3.5
12
11
31
22
57
45
87
69
137
100
205
162
272
229
337
298
385
353
430
Other Jurisdictions
0
9.9
5.7
19
12
29
19
40
26
54
32
67
44
80
56
93
68
106
81
122
Charles City
0
3.2
1.8
6.3
4
9.6
6.2
13
8.4
18
11
23
15
28
19
32
23
37
28
43
Chesterfield
0
1.3
0.8
2.6
1.7
3.9
2.5
4.8
3.4
5.5
4.3
6.2
5
7
5.7
7.7
6.3
8.4
7
8.9
Colonial Heights
0
0.04
0.02
0.1
0.05
0.1
0.07
0.12
0.09
0.14
0.12
0.15
0.1
0.2
0.1
0.2
0.15
0.19
0.16
0.24
Hanover
0
0.02
0.02
0.05
0.03
0.1
0.05
0.2
0.1
0.3
0.1
0.4
0.2
0.5
0.3
0.6
0.4
0.7
0.5
0.7
Henrico
0
0.8
0.5
1.5
1
2.3
1.5
2.8
2
3.2
2.5
3.7
2.9
4.1
3.3
4.6
3.8
5.1
4.2
6.3
Hopewell
0
0.4
0.2
0.8
0.5
1.1
0.7
1.3
1
1.4
1.2
1.6
1.4
1.7
1.5
1.8
1.6
1.9
1.7
2.2
New Kent
0
2.1
1.2
4.1
2.6
6.2
4
9.4
5.4
13
6.9
17
10
21
14
25
18
29
22
34
Petersburg
0
0
0
0
0
0
0
<0.01
0
0.01
<0.01
0.01
<0.01
0.01
0.01
0.02
0.01
0.02
0.01
0.03
Prince George
0
1.9
1.1
3.8
2.4
5.7
3.7
8.1
5
11
6.3
14
8.8
17
12
20
15
23
17
26
Williamsburg
0
0.05
0.03
0.1
0.06
0.1
0.1
0.2
0.1
0.3
0.2
0.3
0.2
0.4
0.3
0.4
0.3
0.5
0.4
0.6
Statewide
54
236
189
479
362
751
585
1029
816
1362
1060
1707
1368
2051
1708
2332
2028
2582
2283
2830
-------
[ 114 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table A.7 Low and High Estimates of the Area of Land Close to Sea Level in Virginia (continued)
Meters above Spring High Water
Jurisdiction
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
0.
5
1.
0
1.
5
2.
0
2.
5
3.
0
3.
5
4.
0
4.
5
5.
0
Tidal
Cumulative (total) amount of Nontidal Wetlands below a given elevation
Eastern Shore
946
7
22
20
48
39
76
63
101
87
114
107
126
119
137
131
146
141
153
149
161
Accomack
484
7
21
19
45
36
70
58
92
80
104
98
114
108
124
119
132
128
138
134
145
Northampton
462
0.4
1.2
1
3.4
2.5
5.9
4.7
8.1
7
9.7
8.8
11
10
13
12
14
14
15
15
16
Northern Virginia
17
0
1
0
2
1
3
2
3
2
4
3
4
3
5
4
5
4
6
5
6
Stafford
6.8
0
0.5
0.3
1
0.6
1.5
1
1.9
1.3
2.3
1.7
2.6
2
2.9
2.3
3.3
2.6
3.6
3
3.9
Alexandria
0.2
0
0.03
0.02
0.07
0.04
0.1
0.06
0.11
0.09
0.11
0.11
0.11
0.11
0.11
0.11
0.11
0.11
0.11
0.11
0.12
Fairfax
4.9
0
0.2
0.1
0.4
0.2
0.6
0.4
0.7
0.5
0.8
0.6
0.9
0.7
1.1
0.9
1.2
1
1.3
1.1
1.4
Prince William
5.1
0
0.2
0.1
0.3
0.2
0.5
0.3
0.6
0.4
0.6
0.5
0.7
0.6
0.8
0.7
0.8
0.7
0.9
0.8
0.9
Rappahannock Area
20
0
0.6
0.3
1.2
0.7
1.7
1.1
2.4
1.5
3
1.9
3.6
2.5
4.2
3.1
4.9
3.7
5.5
4.3
6.2
Fredericksburg
0
0
<0.01
<0.01
0.01
<0.01
0.01
<0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
King George
13
0
0.5
0.3
1
0.6
1.5
1
2
1.3
2.4
1.7
2.8
2.1
3.3
2.5
3.7
2.9
4.1
3.3
4.6
Spotsylvania
0.1
0
0.02
0.01
0.03
0.02
0.05
0.03
0.06
0.04
0.06
0.05
0.07
0.06
0.08
0.06
0.08
0.07
0.09
0.08
0.12
Caroline
6.3
0
0.1
0.03
0.1
0.1
0.2
0.1
0.3
0.2
0.5
0.2
0.7
0.3
0.9
0.5
1.1
0.7
1.3
0.9
1.5
Northern Neck
57
0
2.5
1.2
4.8
2.9
7.3
4.7
9.8
6.4
14
8.1
18
10
22
14
26
18
30
22
34
Westmoreland
14
0
0.5
0.3
1
0.6
1.5
1
2.2
1.3
3.9
1.7
5.6
2.5
7.2
4.1
8.9
5.7
10.6
7.3
12
Richmond
22
0
0.9
0.4
1.7
1
2.5
1.6
3.3
2.2
3.9
2.8
4.5
3.4
5.1
4
5.7
4.5
6.3
5.1
6.9
Northumberland
11
0
0.5
0.3
1.1
0.6
1.6
1
2.2
1.4
3.7
1.8
5.1
2.4
6.6
3.8
8
5.2
9.6
6.6
11
Lancaster
9.8
<0.01
0.5
0.3
1.1
0.7
1.6
1.1
2.1
1.4
2.5
1.8
2.8
2.2
3.2
2.5
3.5
2.8
3.8
3.2
4.2
Middle Peninsula
165
2.6
12
9.5
26
19
40
31
54
44
66
55
78
67
90
79
98
90
106
98
113
Essex
28
0
0.8
0.4
1.5
0.9
2.3
1.5
2.9
2
3.4
2.5
3.9
3
4.4
3.5
4.8
3.9
5.3
4.4
5.9
King and Queen
22
0
0.9
0.5
1.7
1.1
2.5
1.6
3.1
2.2
3.5
2.8
4
3.2
4.4
3.6
4.8
4
5.3
4.4
5.8
King Wlliam
36
0
0.4
0.2
0.7
0.5
1.1
0.7
1.4
0.9
1.7
1.2
2
1.5
2.3
1.8
2.6
2
2.9
2.3
3.3
Middlesex
9.7
<0.01
0.7
0.4
1.4
0.8
2.1
1.4
2.8
1.9
3.1
2.4
3.5
2.8
3.8
3.2
4.1
3.5
4.5
3.8
4.8
Gloucester
44
1.4
5.5
4.5
12
9.1
19
15
25
20
28
25
31
27
34
30
36
33
37
34
38
-------
[ SECTION
1.3 115 ]
Table A.7 Low and High Estimates of the Area of Land Close to Sea Level in Virginia (continued)
Meters above Spring High Water
Jurisdiction
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Mathews
27
1.2
3.8
3.5
8.6
6.7
14
11
19
16
26
22
34
29
41
37
46
44
51
48
55
Hampton Roads
329
12
42
38
74
64
96
84
127
104
167
127
205
164
245
202
285
242
326
279
391
James City
33
<0.01
0.8
0.4
1.5
0.9
2.2
1.4
2.8
1.9
3.3
2.5
3.7
2.9
4.2
3.3
4.6
3.8
5.1
4.2
5.6
York
17
0.19
0.9
0.7
2.7
1.9
4.9
3.7
6.7
5.6
7.4
6.9
8
7.6
8.7
8.2
9.1
8.8
9.5
9.2
9.9
Newport News
15
0.1
0.3
0.3
0.7
0.5
1
0.9
1.3
1.2
1.4
1.35
1.42
1.4
1.5
1.4
1.5
1.5
1.6
1.6
1.7
Poquoson
24
0.02
0.1
0.1
0.4
0.3
0.8
0.6
1.1
0.9
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
Hampton
14
0.06
0.2
0.2
0.4
0.3
0.6
0.5
0.9
0.7
1.5
1.1
2.2
1.8
2.9
2.5
4
3.3
5.1
4.4
6.2
Surry
11
0
0.6
0.3
1.3
0.8
1.9
1.2
2.4
1.7
2.5
2.1
2.7
2.4
2.9
2.6
3
2.7
3.2
2.9
3.4
Isle of Wight
29
<0.01
0.3
0.2
0.6
0.4
0.9
0.6
1.4
0.8
2.2
1
3.1
1.5
4
2.4
4.8
3.2
5.7
4
7.3
Norfolk
4.7
0.1
0.3
0.2
0.5
0.4
0.8
0.7
1.1
0.9
1.3
1.1
1.5
1.3
1.7
1.5
1.7
1.7
1.7
1.7
1.7
Virginia Beach
112
4.2
14
13
25
22
33
29
41
37
46
43
50
48
53
51
56
54
57
56
59
Suffolk
26
0.03
0.2
0.1
0.3
0.2
0.4
0.3
0.8
0.4
1.3
0.5
1.8
1
2.3
1.4
3.1
2.1
6.8
2.9
33
Portsmouth
3.7
2.4
7.7
6.8
8.9
8.9
9.2
9.1
9.5
9.3
9.9
9.6
10
10
11
10
11
10.7
11
10.9
11
Chesapeake
40
4.5
17
15
32
28
40
36
58
44
89
56
120
86
152
116
186
149
217
180
251
Other Jurisdictions
85
0
5.5
3.2
11
6.9
16
10
20
14
22
18
24
20
26
22
28
24
30
26
33
Charles City
22
0
1.9
1.1
3.7
2.4
5.6
3.6
6.8
4.9
7.4
6.2
8
6.9
8.6
7.5
9.2
8.1
9.8
8.6
11
Chesterfield
11
0
0.4
0.2
0.7
0.4
1.1
0.7
1.2
0.9
1.2
1.1
1.2
1.17
1.24
1.2
1.3
1.2
1.3
1.2
1.3
Henrico
4.2
0
0.04
0.02
0.08
0.05
0.12
0.1
0.2
0.1
0.2
0.1
0.2
0.2
0.3
0.2
0.3
0.2
0.4
0.3
0.4
Hopewell
0.7
0
0.1
0.1
0.2
0.1
0.3
0.2
0.3
0.3
0.4
0.3
0.4
0.3
0.4
0.36
0.4
0.37
0.41
0.38
0.42
New Kent
34
0
2.3
1.3
4.5
2.9
6.8
4.4
8.1
6
8.7
7.6
9.3
8.2
9.8
8.8
10.4
9.3
11
9.9
12
Prince George
11
0
0.8
0.5
1.5
1
2.3
1.5
3.1
2
3.9
2.6
4.7
3.3
5.5
4
6.3
4.8
7.1
5.5
7.5
Williamsburg
0.4
0
0.02
0.01
0.03
0.02
0.05
0.03
0.06
0.04
0.07
0.05
0.08
0.06
0.1
0.07
0.11
0.09
0.12
0.1
0.14
Statewide
1619
21
86
72
167
134
240
197
317
260
389
320
459
387
529
455
594
523
657
583
745
Cumulative (total) amount of land below a given elevation
Dry Land
54
236
189
479
362
751
585
1029
816
1362
1060
1707
1368 2051
1708
2332
2028
2582
2283
2830
Nontidal Wetlands
21
86
72
167
134
240
197
317
260
389
320
459
387
529
455
594
523
657
583
745
All Land
1619
1694
1941
1881
2265
2115
2611
2401
2965
2694
3370
2999
3785
3374 4199
3782
4545
4170
4858
4486
5193
-------
744
65
16
149
336
496
188
1.9
267
326
155
1.5
0.03
130
0.02
0.06
55
707
41
2.8
38
90
8.0
166
325
460
149
432
65
0.9
380
556
6349
SOCIATED WITH EPA'S ESTIMATES ]
the Area of Land Close to Sea Level in North Carolina
Meters above Spring High Water
' high low high low high
2.0 2.5 3.0
-Cumulative (total) amount of dry land
109
4.7
0
24
26
127
6.5
0.02
20
50
71
<0.01
0
11
0
0
7.4
433
3.0
0
2.6
15
0.2
35
64
40
12
12
2.4
0
269
22
1368
156
6.8
<0.01
31
46
179
9.2
0.04
32
71
86
<0.01
0
16
0
0
11
482
4.0
0
5.6
20
0.3
43
95
65
17
18
3.7
0
321
38
1757
177
8.2
<0.01
36
59
220
11
0.05
37
87
91
<0.01
0
17
0
0
12
496
4.4
0
7.0
22
0.3
46
116
83
19
24
4.7
0
331
49
1957
235
10
0.01
43
100
287
15
0.1
54
119
102
<0.01
0
22
0
0
17
533
5.6
0
11
28
0.4
55
150
112
25
39
6.5
0
351
68
2388
257
12
0.02
48
115
326
17
0.1
60
143
106
<0.01
0
22
0
0
17
548
6.1
0
13
30
0.4
58
170
131
28
52
7.8
0
358
81
2609
317
15
0.06
55
147
379
22
0.2
78
178
117
0.01
<0.01
27
0
0
21
586
7.7
0.01
18
35
0.8
68
194
161
36
79
10
0
369
106
3030
341
17
0.1
60
157
402
27
0.3
85
201
121
0.01
<0.01
28
0
0
22
600
8.4
0.02
19
37
0.9
71
209
178
40
97
12
0
371
128
3232
401
20
0.2
68
189
421
35
0.4
104
234
131
0.02
<0.01
35
0
0
26
632
11
0.05
23
43
1.5
81
230
202
51
124
15
0.02
374
165
3615
422
22
0.2
74
201
427
42
0.5
111
252
133
0.03
<0.01
36
0
0
26
641
11
0.06
24
45
1.6
85
243
221
55
145
17
0.03
375
192
3803
below a
482
26
0.4
83
232
437
55
0.6
132
273
140
0.07
<0.01
50
<0.01
0
31
660
14
0.1
27
52
2.6
96
263
259
69
189
21
0.06
378
238
4208
given elevation
505 576
28
0.5
89
241
443
65
0.7
140
285
143
0.1
32
1.1
98
256
452
85
0.8
165
300
147
0.2
<0.01 <0.01
52 69
<0.01 <0.01
0
31
666
15
0.2
28
55
2.8
100
274
290
74
227
24
0.07
378
272
4429
0
36
682
19
0.3
30
61
3.8
111
289
350
89
296
30
0.1
379
340
4899
600
35
1.5
105
262
459
100
0.9
175
306
148
0.2
<0.01
72
<0.01
0
37
686
20
0.4
30
64
4.0
116
296
382
94
335
34
0.15
380
387
5131
-------
[ SECTION 1.3 117 ]
Table A.8 Low and High Estimates of the Area of Land Close to Sea Level in North Carolina (continued)
Meters above Spring High Water
County |ow high low high low high low high low high low high low high low high low high low high
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Wetlands
Tidal
—
Cumulative (total) amount of Nontidal Wetlands below
a given
elevation-
Beaufort
35
65
95
105
131
139
162
171
202
215
244
252
272
278
290
294
306
310
320
323
330
Bertie
0.3
110
123
127
132
136
142
147
153
159
167
171
177
181
186
191
200
207
219
225
234
Bladen
0
<0.01
0.1
0.2
0.6
0.9
1.8
2.1
3.3
4.1
6.3
7.3
10
11
15
16
21
23
29
31
36
Brunswick
109
38
44
47
52
55
58
61
65
67
71
73
77
79
82
85
88
90
93
95
98
Camden
7.1
137
146
149
155
157
165
168
175
177
184
187
194
197
201
203
210
214
233
243
258
Carteret
334
34
67
87
117
136
164
180
202
216
231
237
243
247
254
258
267
273
281
286
293
Chowan
0
29
32
34
37
38
40
42
44
46
49
51
56
59
64
70
79
84
91
96
104
Columbus
0
0.2
0.5
0.8
1.3
1.9
2.7
3.2
3.9
4.4
5.1
5.5
6.1
6.4
6.7
7
7.3
7.5
8.0
8.9
11
Craven
12
59
74
80
94
100
115
121
137
142
154
159
170
173
184
188
198
202
213
217
227
Currituck
125
129
144
150
159
164
172
178
184
188
194
196
199
201
203
204
206
209
215
219
221
Dare
168
376
525
553
604
619
651
659
664
664
665
666
666
666
666
666
666
666
666
666
666
Duplin
0
0
0
0
0
0
0
0
0.01
0.03
0.1
0.2
0.5
0.7
1.4
1.8
2.9
3.4
4.7
5.3
6.7
Edgecombe
0
0
0
0
0
0
0
0
0
0
0
0
<0.01
<0.01
<0.01
<0.01
0.01
0.01
0.03
0.05
0.09
Gates
0
78
89
89
93
94
98
99
102
103
107
108
114
115
121
122
126
126
129
129
132
-------
0.2
1.6
81
689
33
17
150
60
14
72
232
124
239
180
70
6.8
623
197
5405
6349
5405
13026
ASSOCIATED WITH EPA'S ESTIMATES ]
ie Area of Land Close to Sea Level in North Carolina (continued)
Meters above Spring High Water
low high low high low high low high low high low
0
0
54
488
11
0
73
36
2.0
31
73
62
113
47
27
0
523
86
3048
0
0
58
538
13
0.07
88
39
2.6
35
81
68
128
52
30
0
554
92
3354
0
0
58
549
14
0.13
93
40
2.7
36
86
71
132
55
32
0
559
96
3465
0
0
61
571
16
0.38
103
42
3.5
40
97
75
145
61
35
0
569
101
3694
0
0
62
578
16
0.5
106
43
3.7
41
106
79
150
66
36
0
0
65
592
18
1.1
114
45
5.9
45
123
84
161
74
39
0 <0.01
571 579
106 112
3794 3992
0
0
66
598
19
1.5
117
46
6.0
46
131
88
165
79
41
0.02
582
118
0
0
69
614
21
2.8
124
48
7.3
49
142
93
175
86
44
0.4
591
128
0 <0.01
0
69
619
21
3.3
126
49
7.6
51
148
96
179
90
46
0.6
593
134
4347
0
71
634
23
4.9
130
51
9.6
54
161
102
189
98
49
1.4
601
145
4509
1368 1757
3048 3354
5687 6384
1957 2388
3465 3694
6694 7354
4087 4269
Cumulative (total) amount of land below
2609 3030 3232 3615 3803 4208
3794 3992
7676 8293
4087 4269
8591 9157
4347 4509
9422 9989
<0.01
0
71
638
24
5.6
132
52
9.9
55
171
106
192
103
51
1.6
606
152
4583
a given
4429
0.01
0
74
653
26
7.6
136
53
11
59
186
113
202
113
54
2.3
614
162
4741
elevation
4899 5131
0.01
0
74
660
26
8.4
137
54
11
60
192
116
206
124
57
2.6
616
168
4818
4583 4741
10284 10912
0.02
<0.01
77
672
28
11
140
56
12
64
201
119
216
137
60
3.6
620
175
4969
5529
4818 4969
11221 11770
-------
Appendix B
Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level,
by Subregion3 (square kilometers)
a The low and high estimates are based on the on the contour interval and/or stated root mean square error (RMSE) of the data used to calculate
elevations and an assumed standard error of 30 cm in the estimation of spring high water. For details, see main text of this Section 1.3.
-------
[ 120 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table B.1 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level - Long Island Sound, New York
Elevations above spring high water
Locality
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Cumulative
total) amount of dry land below a given elevation
Westchester
0.2
1.5
1.1
3.0
2.8
5.8
5.1
8.6
10.0
12.4
Bronx
0.4
2.6
1.8
5.1
4.8
9.8
8.7
14.6
16.9
19.6
Queens
6.2
17.0
14.6
28.1
31.7
48.6
50.7
66.6
76.5
80.8
Brooklyn
3.1
9.1
8.0
15.6
18.8
30.5
34.0
47.4
58.9
62.8
Nassau
2.2
19.2
12.9
44.5
50.9
85.4
85.4
104.1
119.3
132.1
Suffolk
13.7
51.5
43.1
96.8
114.9
181.3
188.6
251.3
318.8
371.4
Total
25.8
100.9
81.4
193.1
223.9
361.4
372.4
492.6
600.4
679.1
Tidal
Cumulative (total) amount of wetlands below a given elevation
Westchester
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
Bronx
1.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
Queens
11.9
0.0
0.2
0.1
0.3
0.4
0.5
0.5
0.6
0.7
0.7
Brooklyn
10.1
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
Nassau
43.7
0.1
0.4
0.3
0.7
0.8
1.5
1.4
2.1
2.6
3.2
Suffolk
72.1
1.5
5.7
4.9
9.8
10.8
15.2
15.1
18.3
20.8
23.8
Total
140.0
1.7
6.4
5.4
11.0
12.1
17.4
17.2
21.3
24.3
28.1
Dry and nontidal wetland
27
107
87
204
236
379
390
514
625
707
All land
140
167
247
227
344
376
519
530
654
765
847
-------
[ SECTION 1.3 121 ]
Table B.2 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in New York Harbor
Elevations above spring high water
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Locality
State
Cumulative
total) amount of dry land below a given elevation
Monmouth
NJ
2.0
5.4
5.9
10.5
15.8
18.7
22.4
24.7
31.2
32.5
Middlesex
NJ
0.4
8.8
4.3
17.4
14.7
31.2
25.4
43.5
45.6
62.0
Somerset
NJ
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
Union
NJ
0.4
6.9
4.2
13.7
12.6
22.7
20.2
29.3
31.7
40.9
Hudson
NJ
0.6
16.2
10.4
32.2
30.6
49.0
46.4
56.9
60.4
67.5
Essex
NJ
0.4
6.1
3.9
12.0
11.3
19.6
17.8
25.3
27.8
32.2
Bergen
NJ
0.9
15.6
10.2
31.0
29.4
44.2
42.5
49.0
51.1
58.2
Passaic
NJ
0.0
0.2
0.1
0.3
0.3
0.7
0.6
1.1
1.3
1.9
Ellis Island
NJ
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Staten Island
NY
0.3
7.8
5.1
15.5
14.9
24.9
23.3
30.8
33.9
39.0
Brooklyn
NY
0.0
0.8
0.5
1.6
1.6
3.1
2.7
4.5
5.3
6.4
Manhattan
NY
0.0
2.2
1.4
4.3
4.2
8.3
7.2
12.1
14.1
17.5
Bronx
NY
0.0
0.6
0.4
1.2
1.2
2.7
2.2
4.4
5.3
6.9
Westchester
NY
0.0
1.3
0.7
2.6
2.3
4.7
4.1
6.1
6.4
8.3
Total
5.1
71.9
47.1
142.6
138.9
230.0
214.9
288.0
314.1
373.7
Tidal
Cumulative (total) amount of wetlands below a given elevation
Monmouth
NJ
7.7
0.1
0.3
0.4
0.6
0.8
0.9
1.1
1.2
1.7
1.8
Middlesex
NJ
21.7
0.1
1.2
0.7
2.3
2.1
3.9
3.5
5.3
5.7
7.8
Union
NJ
2.3
0.0
0.2
0.1
0.3
0.3
0.5
0.4
0.6
0.6
0.8
Hudson
NJ
12.0
0.0
0.2
0.1
0.3
0.3
0.4
0.4
0.5
0.5
0.5
Essex
NJ
0.3
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Bergen
NJ
15.0
0.0
0.6
0.4
1.2
1.1
1.5
1.5
1.5
1.6
2.1
Passaic
NJ
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
Staten Island
NY
4.0
0.0
0.5
0.3
0.9
0.9
1.4
1.3
1.6
1.7
1.9
Bronx
NY
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
Westchester
NY
0.7
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Rockland
NY
2.3
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.2
Orange
NY
0.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Putnam
NY
1.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Dutchess
NY
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Total
67.6
0.2
3.0
2.0
5.8
5.6
9.0
8.6
11.1
12.2
15.5
Dry and nontidal wetland
5
75
49
148
145
239
223
299
326
389
| All land
68
73
142
117
216
212
307
291
367
394
457
-------
[ 122 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table B.3 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in New Jersey Shore
Elevations above spring high water:
County
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Cumulative (total) amount of Dry Land below a given elevation
Cape May
7.6
21.8
23.8
42.0
56.1
73.5
78.4
102.2
124.2
144.1
Atlantic
4.0
13.5
14.0
29.0
40.8
53.9
57.3
71.0
88.5
105.8
Burlington
0.0
2.1
1.3
4.1
4.0
8.9
7.0
15.1
18.4
27.1
Ocean
4.6
18.7
21.8
44.0
67.3
80.6
93.2
106.8
136.6
149.1
Monmouth
2.1
4.9
5.5
9.4
15.3
19.9
26.4
31.8
50.4
54.9
Total
18.3
61.1
66.5
128.5
183.5
236.9
262.3
326.9
418.1
481.0
Tidal
Cumulative (total) amount of wetlands below a given elevation
Cape May
153.2
2.9
12.0
10.2
20.4
22.2
33.1
32.2
42.7
47.6
55.2
Atlantic
204.0
4.8
17.9
14.7
29.2
31.9
50.1
48.3
68.2
82.0
102.9
Burlington
37.3
0.2
9.7
6.2
19.1
18.7
32.7
30.0
41.3
45.8
57.2
Ocean
124.8
2.3
11.6
10.0
21.7
25.8
38.3
39.0
49.4
56.5
65.8
Monmouth
4.4
0.5
0.9
1.0
1.4
1.9
2.3
2.9
3.2
4.8
5.1
Total
523.6
10.7
52.1
42.1
91.9
100.5
156.5
152.4
204.9
236.5
286.3
Dry and nontidal wetland
29
113
109
220
284
393
415
532
655
767
All land
524
553
637
632
744
808
917
938
1055
1178
1291
-------
[ SECTION 1.3 123 ]
Table B.4 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in Delaware Estuary
Elevations above spring high water:
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Locality
State
Cumulative (total) amount of dry land below a given elevation
Sussex
DE
6.4
18.2
15.8
30.8
37.3
55.2
60.0
78.6
103.3
119.7
Kent
DE
8.8
24.8
21.9
40.6
47.9
77.6
86.1
119.2
177.8
209.9
New Castle
DE
7.1
19.0
16.8
29.9
34.4
52.2
54.2
75.0
99.0
119.0
Delaware
PA
0.4
6.1
4.0
12.1
11.5
18.0
17.2
20.7
22.2
25.9
Philadelphia3
PA
3.6
6.1
6.8
12.4
20.0
24.8
31.6
36.8
51.5
54.8
Bucks
PA
0.0
4.4
0.2
8.5
5.3
18.0
11.9
27.4
25.3
42.1
Mercer
NJ
0.0
0.1
0.0
0.1
0.1
0.2
0.2
0.4
0.3
0.4
Burlington
NJ
0.1
4.3
0.4
8.4
5.3
16.4
11.0
24.5
22.5
42.2
Camden
NJ
0.0
3.8
0.1
7.3
4.3
14.8
9.5
22.4
20.4
34.5
Gloucester
NJ
0.2
9.2
6.1
18.4
17.7
33.3
29.6
46.5
53.5
69.3
Salem
NJ
5.9
26.9
21.3
48.7
53.8
84.4
83.9
114.0
135.5
160.3
Cumberland
NJ
3.0
15.8
12.1
28.9
30.3
53.2
49.5
76.9
90.8
114.3
Cape May
NJ
0.4
3.5
2.5
7.5
8.6
19.9
20.9
36.9
55.5
68.0
Total
35.9
142.0
108.0
253.7
276.5
468.0
465.7
679.2
857.7
1060.4
Tidal
Cumulative (total) amount of wetlands below a given elevation
Sussex
DE
67.4
2.1
4.8
4.6
6.2
6.8
8.6
9.0
10.6
12.3
13.3
Kent
DE
168.7
4.9
11.4
10.4
16.6
19.0
24.6
25.9
30.9
38.8
43.5
New Castle
DE
73.5
1.8
3.8
3.5
4.8
5.1
6.7
6.7
8.4
9.7
11.1
Delaware
PA
3.6
0.1
0.8
0.6
1.7
1.6
2.2
2.2
2.3
2.3
2.3
Philadelphia
PA
0.6
0.5
0.6
0.6
0.9
1.2
1.4
1.6
1.7
1.9
1.9
Bucks
PA
1.9
0.0
0.9
0.1
1.9
1.2
4.1
2.9
6.3
6.2
8.2
Mercer
NJ
1.8
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Burlington
NJ
5.4
0.0
0.6
0.0
1.2
0.7
2.3
1.5
3.4
3.1
5.8
Camden
NJ
1.5
0.0
0.3
0.1
0.7
0.5
1.3
0.9
1.9
1.8
2.7
Gloucester
NJ
18.0
0.2
8.8
5.9
17.4
16.8
25.9
25.0
28.8
30.4
33.5
Salem
NJ
110.1
9.6
25.1
22.3
35.8
38.2
49.0
48.9
55.4
60.3
67.6
Cumberland
NJ
212.6
4.7
23.6
18.1
42.1
43.6
65.5
63.5
80.6
89.8
103.2
Cape May
NJ
48.3
4.3
14.7
12.2
25.1
28.2
40.3
41.5
51.2
58.6
63.7
Total
713.5
28.3
95.5
78.5
154.2
163.0
231.8
229.7
281.6
315.1
356.8
Dry and nontidal wetland
64
237
187
408
440
700
695
961
1173
1417
All land
713
778
951
900
1121
1153
1413
1409
1674
1886
2131
a This number includes Philadelphia's 2.4 square kilometers of dry land below spring high water, of which 0.87, 0.26, 0.054, and 0.005 are at least 0.5, 1, 2, and 3
meters below spring high water, respectively. Most of this land is near Philadelphia International Airport.
-------
[ 124 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table B.5 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in DelMarVa Atlantic Coast
Elevations above spring high water:
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Locality
State
Cumulative (total) amount of Dry Land below a given elevation
Northampton
VA
5.1
14.5
13.0
16.8
17.9
20.6
21.4
24.6
30.5
35.0
Accomack
VA
7.5
22.6
20.1
37.7
44.5
61.7
65.8
81.2
103.7
118.9
Worcester
MD
3.7
18.6
21.7
42.4
77.5
102.8
134.0
154.6
219.1
234.6
Sussex
DE
11.1
32.4
27.6
53.5
64.5
94.9
104.2
139.5
196.5
234.2
Total
27.4
88.1
82.5
150.3
204.4
280.0
325.4
399.9
549.9
622.7
Tidal
Cumulative (total) amount of wetlands below a given elevation
Northampton
VA
436.4
0.3
0.8
0.7
2.1
2.8
4.4
4.6
5.2
5.8
6.1
Accomack
VA
327.3
1.3
4.1
3.5
10.4
13.5
20.7
21.9
26.2
31.2
33.7
Worcester
MD
118.5
0.4
4.3
5.0
8.8
14.1
18.1
23.4
27.0
36.0
37.6
Sussex
DE
41.0
1.7
4.9
4.2
7.5
8.8
12.2
12.9
15.7
18.9
20.7
Total
923.3a
3.7
14.1
13.4
28.7
39.2
55.4
62.7
74.1
91.9
98.1
Dry and Nontidal wetland
31
102
96
179
244
335
388
474
642
721
All Land
923
954
1025
1019
1102
1167
1259
1311
1397
1565
1644
a Includes 375 square kilometers of tidal mudflats in Northampton and Accomack counties.
-------
[ SECTION 1.3 125 ]
Table B.6 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in Hampton Roads, Virginia
Elevations above spring high water
Locality
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Cumulative (total) amount of Dry Land below a given elevation
Virginia Beach
9.3
33.0
30.3
68.7
93.6
163.2
184.7
272.9
378.1
418.2
Chesapeake
3.5
11.9
10.8
30.6
44.6
86.6
100.4
204.5
353.0
429.7
Norfolk
1.9
5.8
5.2
17.1
24.0
42.4
52.4
91.2
121.7
128.2
Portsmouth
1.2
3.9
3.5
9.6
12.8
22.0
26.7
45.0
62.6
69.9
Suffolk
0.7
4.3
3.1
7.1
7.5
15.2
13.0
31.0
47.3
73.3
Isle of Wight
0.2
3.4
2.1
6.2
6.0
12.8
10.1
21.6
26.8
42.0
Surry
0.0
1.4
0.7
2.7
2.7
5.3
4.6
7.1
8.1
11.2
James City
0.1
3.8
2.2
7.2
7.0
14.2
11.8
22.1
26.7
38.7
York
1.4
6.0
4.8
13.1
16.3
27.7
28.3
37.3
44.3
51.3
Newport News
2.2
6.9
6.1
11.0
12.9
17.9
19.3
24.8
34.9
42.3
Poquoson
1.4
4.5
4.1
8.8
10.9
16.3
16.4
16.6
16.7
16.7
Hampton
1.9
5.9
5.3
18.1
25.4
45.3
51.2
73.8
94.7
102.4
Total
23.8
90.8
78.2
200.2
263.6
468.9
519.0
847.9
1214.9
1423.8
Tidal
Cumulative (total) amount of wetlands below a given elevation
Virginia Beach
111.9
4.2
14.5
13.3
24.9
29.1
40.9
43.5
49.6
56.5
59.3
Chesapeake
39.7
4.5
16.6
15.4
32.1
36.4
58.3
55.7
120.2
180.3
250.8
Norfolk
4.7
0.1
0.3
0.2
0.5
0.7
1.1
1.1
1.5
1.7
1.7
Portsmouth
3.7
2.4
7.7
6.8
8.9
9.1
9.5
9.6
10.3
10.9
11.2
Suffolk
26.4
0.0
0.2
0.1
0.3
0.3
0.8
0.5
1.8
2.9
33.1
Isle of Wight
28.6
0.0
0.3
0.2
0.6
0.6
1.4
1.0
3.1
4.0
7.3
Surry
11.5
0.0
0.6
0.3
1.3
1.2
2.4
2.1
2.7
2.9
3.4
James City
32.8
0.0
0.8
0.4
1.5
1.4
2.8
2.5
3.7
4.2
5.6
York
17.0
0.2
0.9
0.7
2.7
3.7
6.7
6.9
8.0
9.2
9.9
Newport News
15.1
0.1
0.3
0.3
0.7
0.9
1.3
1.4
1.4
1.6
1.7
Poquoson
23.7
0.0
0.1
0.1
0.4
0.6
1.1
1.1
1.1
1.1
1.1
Hampton
14.3
0.1
0.2
0.2
0.4
0.5
0.9
1.1
2.2
4.4
6.2
Total
329.4
11.7
42.4
38.0
74.2
84.5
127.1
126.5
205.4
279.5
391.1
Dry and Nontidal wetland
35
133
116
274
348
596
645
1053
1494
1815
All Land
329
365
463
446
604
677
925
975
1383
1824
2144
-------
[ 126 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table B.7 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in Middle Peninsula and Northern Neck Areas, Virginia
Elevations above spring high water
Locality
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Cumulative (total) amount of Dry Land below a given elevation
Gloucester
4.1
16.0
13.2
32.9
40.5
66.9
66.9
84.2
96.4
110.8
Mathews
4.7
14.8
13.4
33.1
43.9
73.1
78.6
96.8
114.7
120.7
Middlesex
0.2
3.4
2.0
6.8
7.3
14.4
13.1
22.8
28.1
38.9
King William
0.0
1.6
0.9
3.2
3.1
8.4
5.4
17.7
22.7
36.1
King and Queen
0.0
2.9
1.7
5.7
5.5
11.9
9.6
19.0
22.7
32.9
Essex
0.0
3.8
2.0
7.3
7.1
15.5
12.3
27.9
34.2
52.8
Lancaster
0.1
7.0
3.6
13.8
13.8
28.0
24.0
41.5
48.4
67.9
Northumberland
0.0
5.9
2.8
11.5
11.0
24.1
19.2
63.8
84.5
140.9
Richmond
0.0
4.6
2.4
8.9
8.7
18.5
15.0
31.6
38.2
56.5
Caroline
0.0
0.4
0.3
0.9
0.9
1.8
1.5
2.8
3.4
5.2
Spotsylvania
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.5
0.5
0.8
Fredericksburg
0.0
0.1
0.0
0.1
0.1
0.2
0.2
0.3
0.4
0.5
Total
9.2
60.5
42.4
124.2
142.1
263.2
246.0
409.0
494.2
664.0
Tidal
Cumulative (total) amount of wetlands below a given elevation
Gloucester
43.5
1.4
5.5
4.5
11.9
14.7
24.8
24.6
30.8
34.4
38.5
Mathews
27.0
1.2
3.8
3.5
8.6
11.4
19.0
21.6
33.6
48.1
55.1
Middlesex
9.7
0.0
0.7
0.4
1.4
1.4
2.8
2.4
3.5
3.8
4.8
King Wlliam
35.6
0.0
0.4
0.2
0.7
0.7
1.4
1.2
2.0
2.3
3.3
King and Queen
21.6
0.0
0.9
0.5
1.7
1.6
3.1
2.8
4.0
4.4
5.8
Essex
27.5
0.0
0.8
0.4
1.5
1.5
2.9
2.5
3.9
4.4
5.9
Lancaster
9.8
0.0
0.5
0.3
1.1
1.1
2.1
1.8
2.8
3.2
4.2
Northumberland
11.4
0.0
0.5
0.3
1.1
1.0
2.2
1.8
5.1
6.6
10.8
Richmond
21.7
0.0
0.9
0.4
1.7
1.6
3.3
2.8
4.5
5.1
6.9
Caroline
6.3
0.0
0.1
0.0
0.1
0.1
0.3
0.2
0.7
0.9
1.5
Spotsylvania
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
Fredericksburg
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Total
214.3
2.6
14.1
10.5
29.7
35.1
62.0
61.7
90.9
113.5
136.9
Dry and Nontidal wetland
12
75
53
154
177
325
308
500
608
801
All Land
214
226
289
267
368
392
539
522
714
822
1015
-------
[ SECTION 1.3 127 ]
Table B.8 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level in Potomac River
Elevations above spring high water
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Locality
State
Cumulative (total) amount of Dry Land below a given elevation
Westmoreland
VA
0.0
4.7
2.4
9.3
9.0
21.2
15.5
53.0
69.2
112.3
King George
VA
0.0
2.7
1.5
5.4
5.2
11.4
9.0
21.9
27.3
42.8
Stafford
VA
0.0
1.4
0.8
2.7
2.7
5.4
4.6
8.1
9.5
13.5
Prince William
VA
0.0
1.0
0.5
2.0
1.9
3.9
3.3
5.5
6.4
8.8
Fairfax
VA
0.0
2.0
1.1
3.9
3.8
7.6
6.6
10.7
12.4
18.1
Alexandria
VA
0.0
0.4
0.3
0.9
0.9
1.7
1.5
2.5
2.9
4.0
Arlington
VA
0.0
0.2
0.1
0.5
0.5
1.3
0.8
2.6
3.4
5.0
DC
1.6
3.0
2.8
4.4
5.5
7.4
8.9
11.1
15.9
17.7
Prince George's
MD
0.1
1.1
0.5
2.2
1.6
4.0
3.2
5.4
6.6
9.9
Charles
MD
0.7
10.9
4.6
19.4
14.1
38.4
28.3
64.0
74.2
96.0
St. Mary's
MD
1.6
12.0
5.6
19.8
14.9
39.2
27.9
70.1
81.2
99.8
Total
4.1
39.5
20.1
70.4
60.0
141.5
109.5
255.1
308.9
428.1
Tidal
Cumulative (total) amount of wetlands below a given elevation
Westmoreland
VA
14.4
0.0
0.5
0.3
1.0
1.0
2.2
1.7
5.6
7.3
12.0
King George
VA
13.5
0.0
0.5
0.3
1.0
1.0
2.0
1.7
2.8
3.3
4.6
Stafford
VA
6.8
0.0
0.5
0.3
1.0
1.0
1.9
1.7
2.6
3.0
3.9
Prince Wlliam
VA
5.1
0.0
0.2
0.1
0.3
0.3
0.6
0.5
0.7
0.8
0.9
Fairfax
VA
4.9
0.0
0.2
0.1
0.4
0.4
0.7
0.6
0.9
1.1
1.4
Alexandria
VA
0.2
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Arlington
VA
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
DC
0.5
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.2
0.3
0.3
Prince George's
MD
1.6
0.0
0.3
0.1
0.5
0.4
0.8
0.7
0.9
1.2
2.1
Charles
MD
22.9
0.1
3.6
1.4
6.2
4.6
11.3
9.0
15.9
17.8
22.2
St. Mary's
MD
11.7
0.3
1.8
0.8
3.3
2.4
7.1
4.9
12.9
15.4
22.5
Total
81.5
0.5
7.6
3.5
13.9
11.1
26.8
21.0
42.7
50.1
70.1
Dry and Nontidal wetland
5
47
24
84
71
168
130
298
359
498
All Land
82
86
129
105
166
153
250
212
379
441
580
-------
[ 128 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table B.9 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level - Maryland Western Shore
Elevations above spring high water
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Locality
Cumulative (total) amount of Dry Land below a given elevation
Prince George's
0.0
1.1
0.4
1.7
1.3
3.2
2.3
5.3
6.5
10.8
Charles
0.0
0.7
0.3
1.2
0.9
2.0
1.7
2.5
2.7
3.3
St. Mary's
0.8
3.8
2.5
8.0
8.8
18.8
18.2
30.6
38.5
48.4
Calvert
0.4
3.9
1.7
5.8
4.6
10.1
7.6
17.3
21.2
35.7
Anne Arundel
1.7
7.2
6.7
14.6
20.2
38.7
43.5
59.1
80.5
94.3
Howard
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.2
0.3
Baltimore City
0.2
2.1
0.9
3.9
2.7
7.5
5.7
11.9
14.1
21.0
Baltimore
2.3
6.6
7.3
13.0
20.8
27.0
37.0
45.8
74.5
80.7
Harford
0.7
17.3
7.6
25.1
21.7
40.3
34.2
57.1
65.5
78.2
Total
6.1
42.7
27.5
73.4
81.1
147.8
150.3
229.7
303.7
372.7
Tidal
Cumulative (total) amount of wetlands below a given elevation
Prince George's
12.3
0.0
0.5
0.2
0.9
0.7
1.8
1.3
2.9
3.5
5.1
Charles
1.3
0.0
0.2
0.1
0.2
0.2
0.4
0.3
0.4
0.5
0.6
St. Mary's
7.0
0.3
1.0
0.8
2.0
2.2
3.9
3.9
5.9
7.5
8.8
Calvert
14.6
0.1
0.9
0.4
1.3
1.1
2.2
1.7
3.8
4.7
7.5
Anne Arundel
12.1
0.2
0.7
0.6
1.6
3.1
8.1
9.5
12.4
15.3
17.1
Howard
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.1
0.1
0.1
Baltimore City
0.2
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.1
0.1
0.1
Baltimore
10.5
0.1
0.3
0.3
0.7
1.0
1.3
1.5
1.7
2.2
2.3
Harford
29.4
0.2
2.5
1.2
3.8
3.3
6.2
5.2
9.0
10.2
12.0
Total
87.3
0.8
6.2
3.7
10.5
11.6
24.0
23.5
36.4
43.9
53.6
Dry and Nontidal wetland
7
49
31
84
93
172
174
266
348
426
All Land
87
94
136
119
171
180
259
261
353
435
514
-------
[ SECTION 1.3 129 ]
Table B.10 Low and High Estimates for the Area of Dry and Wet Land Close to Sea Level - Chesapeake Bay Eastern Shore
Elevations above spring high water
50 cm
1 meter
2 meters
3 meters
5 meters
Low
High
Low
High
Low
High
Low
High
Low
High
Locality
State
Cumulative (total) amount of Dry Land below a given elevation
Cecil
MD
0.2
2.5
1.0
5.2
3.7
11.6
7.8
20.0
24.3
37.9
Kent
MD
0.2
8.4
4.8
15.9
16.3
32.9
28.8
56.1
71.4
105.2
Queen Anne's
MD
0.6
4.1
5.3
11.9
24.2
35.0
51.6
68.2
125.2
142.6
Caroline
MD
0.7
3.2
2.2
6.1
6.9
12.5
13.2
19.7
25.9
32.9
Talbot
MD
2.2
7.8
11.1
23.7
64.0
98.7
148.7
175.1
265.6
279.4
Sussex
DE
0.5
1.6
1.4
3.3
4.3
7.1
8.5
13.8
26.0
36.3
Dorchester
MD
30.1
120.0
150.4
214.9
281.9
312.9
358.4
386.2
461.6
474.0
Wicomico
MD
5.0
14.9
18.3
28.6
47.1
58.5
76.0
86.2
133.2
141.6
Somerset
MD
17.1
58.4
70.5
100.7
167.8
193.4
215.1
232.5
326.5
344.6
Worcester
MD
0.7
2.7
3.1
5.8
10.6
16.5
23.6
28.4
46.1
53.4
Accomack
VA
5.8
18.4
16.8
40.4
53.3
87.5
94.2
110.4
129.5
138.1
Northampton
VA
2.3
7.2
6.5
15.8
20.8
34.5
39.9
62.8
98.7
123.7
Total
65.3
249.1
291.4
472.4
701.0
901.2
1065.8
1259.5
1734.0
1909.7
Tidal
Cumulative (total) amount of wetlands below a given elevation
Cecil
MD
12.6
0.0
0.2
0.0
0.7
0.4
1.7
1.2
2.8
3.5
5.5
Kent
MD
18.3
0.1
1.1
0.9
2.6
3.3
5.4
5.2
7.9
9.7
14.4
Queen Anne's
MD
21.4
0.2
1.1
1.5
3.0
4.9
6.5
7.9
9.6
14.6
17.9
Caroline
MD
14.4
0.3
1.4
0.7
2.6
2.5
5.3
4.4
7.5
8.0
11.7
Talbot
MD
26.1
0.1
0.3
0.5
1.0
2.5
4.2
6.8
8.5
17.9
19.6
Sussex
DE
6.7
0.6
1.8
1.6
2.7
3.1
4.4
4.8
6.4
10.1
13.1
Dorchester
MD
424.8
14.9
45.8
53.4
70.1
94.4
104.0
113.8
120.6
140.1
142.5
Wcomico
MD
67.0
5.4
9.9
10.7
13.5
24.2
29.2
37.0
44.4
67.0
70.2
Somerset
MD
265.4
6.6
15.7
17.3
21.3
34.8
39.8
45.1
51.5
80.6
90.1
Worcester
MD
23.7
0.3
0.9
1.0
1.6
2.7
4.0
6.3
8.8
18.2
20.8
Accomack
VA
156.4
5.3
16.7
15.3
34.6
44.8
71.8
76.5
88.2
103.2
111.1
Northampton
VA
25.5
0.1
0.4
0.4
1.2
1.9
3.7
4.2
6.2
8.8
10.1
Total
1062.4
33.8
95.3
103.3
155.0
219.5
279.9
313.0
362.4
481.7
526.9
Dry and Nontidal wetland
99
344
395
627
921
1181
1379
1622
2216
2437
All Land
1062
1162
1407
1457
1690
1983
2244
2441
2684
3278
3499
-------
Appendix C
Low and High Estimates of the Area of Land Close to Sea Level,
by Region: Mid-Atlantica (square kilometers)
a The low and high estimates are based on the on the contour interval and/or stated root mean square error (RMSE) of the data used to calculate
elevations and an assumed standard error of 30 cm in the estimation of spring high water. For details, see main text of this Section 1.3.
-------
[ SECTION 1.3 131 ]
Table C.1 Low and High Estimates of the Area of Land Close to Sea Level by Region
Meters above Spring High Water
Jurisdiction low high low high low high low high low high low high low high low high low high low high
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
¦Cumulative (total) amount of Dry Land below a given elevation
L.I. Sound and Peconic
6
31
22
59
42
86
63
111
85
135
106
158
127
181
149
200
170
216
190
229
South Shore Long Island
19
70
59
134
108
198
161
250
216
293
266
335
309
369
347
400
380
429
410
450
NY Harbor/
Raritan Bay Total
5
72
47
143
93
200
139
230
185
260
215
288
240
316
265
343
290
360
314
374
New York
0
13
8 25
16
37
24
44
32
51
40
58
46
65
52
72
59
76
65
78
New Jersey
5
59
39
117
77
163
115
186
153
209
175
230
194
251
213
271
231
284
249
295
New Jersey Shore
18
61
66
129
131
186
184
237
223
283
262
327
304
369
344
409
382
445
418
481
Delaware Bay Total
19
62
52
108
88
154
124
206
166
259
217
312
268
366
321
421
374
470
427
512
New Jersey
3
19
15
36
27
53
39
73
52
94
70
114
90
134
109
154
127
170
146
182
Delaware
15
43
38
71
61
101
85
133
114
165
146
198
178
232
212
267
247
300
281
330
Delaware River Total
17
80
56
146
103
210
152
262
201
315
249
368
296
417
342
467
386
512
430
549
Delaware: fresh
2
6
5
10
8 14
11
19
15
24
19
28
24
32
28
36
32
39
35
42
Delaware: saline
5
13
12
20
17
27
23
33
29
40
35
47
41
54
49
62
56
70
64
77
New Jersey: fresh
0
18
7
35
17
52
28
67
39
83
52
98
65
114
77
130
90
144
102
154
New Jersey: saline
6
27
21
48
37
68
53
82
68
96
82
109
95
121
108
133
119
143
130
152
Pennsylvania
4
17
11
33
24
49
37
61
50
73
61
85
71
96
81
106
90
115
99
123
Atlantic Coast of
Del-Mar-Va Total
27
87
81
148
140
212
200
275
259
334
318
390
373
443
425
495
477
548
529
599
Delaware
11
32
28
53
46
74
64
95
82
117
104
139
126
163
149
187
172
210
196
234
Maryland
3
17
20
40
44
69
74
97
101
123
126
145
148
163
165
180
182
196
199
211
Virginia
13
37
33
55
49
69
62
82
75
94
87
106
99
117
111
129
122
141
134
154
Chesapeake Bay Total
102
466
441
906
791
1357
1193
1827
1587
2334
1973
2859
2448
3378
2962
3818
3446
4234
3865
4633
Delaware
1
2
1
3
3
5
4
7
6
10
9
14
12
18
15
24
20
29
26
36
Maryland
66
290
306
530
515
763
738
1007
952
1227
1141
1451
1352
1670
1572
1865
1778
2047
1966
2213
fresh
9
35
33
70
63
115
106
167
152
212
192
263
243
325
307
394
377
466
449
533
vulnerable
49
187
234
344
379
477
515
605
633
704
731
804
830
892
911
958
974
1011
1024
1058
saline
00
CD
00
39
117
74
171
118
235
167
311
218
385
280
454
354
513
427
570
492
623
-------
[ 132 UNCERTAINTY RANGES ASSOCIATED WITH EPA'S ESTIMATES ]
Table C.1 Low and High Estimates of the Area of Land Close to Sea Level by Region (continued)
Meters above Spring High Water
Jurisdiction
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
low
high
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
District of Columbia
2
3
3
4
4
6
5
7
7
9
9
11
11
13
13
15
14
16
16
18
Virginia
34
172
131
369
268
583
445
805
622
1088
815
1383
1073
1677
1362
1915
1634
2141
1857
2366
fresh
1
26
15
50
33
75
50
106
67
152
89
198
125
244
169
292
214
340
260
394
vulnerable
3 8
7
17
14
26
22
35
30
40
37
44
42
48
46
51
50
53
52
55
saline
30
138
108
302
222
482
373
665
525
896
689
1140
906
1385
1147
1573
1370
1748
1545
1916
Virginia Beach
Atlantic Coast
7
27
25
56
45
99
78
142
118
180
158
219
196
257
235
288
272
299
293
310
Pamlico Albemarle Sounds
621
1028
1186
1519
1684
2052
2239
2601
2774
3108
3274
3629
3827
4244
4449
4789
4932
5173
5269
5441
Atlantic Coast of NC
103
151
182
238
273
336
370
429
458
507
529
579
603
655
682
740
768
829
855
908
Total NY to NC
945
2136
2218
3585
3498
5089
4903
6569
6272
8008
7567
9463
8991
10994
1052012370
1187613515
13001
14486
Wetlands
Tidal
Cumulative amoiint of MnntiHal \A/c»tlanHc hc»lr\\A/ c\ ni\/£»n o I ox/at inn
v_/u 111 u i c4 u v c ^ lulcj i j ciiiiuuiii ui i \Ui i uucii V V c u cj 11 u o uciuvv cj y i vei i l^icvciliuii
L.I. Sound and Peconic
36
1
2
2
4
3
6
4
7
6
8
7
9
8
10
9
11
10
12
11
13
South Shore Long Island
104
1
4
4
7
6
9
8
10
9
11
11
12
11
13
12
13
13
14
14
15
NY Harbor/
Raritan Bay Total
68
0
3
2
6
4
8
6
9
7
10
9
11
9
12
10
13
11
14
12
16
New York
9
0
1
0
1
1
1
1
2
1
2
2
2
2
2
2
2
2
2
2
2
New Jersey
59
0
2
2
5
3
7
5
7
00
CD
7
9
8 10
9
11
9
12
10
13
New Jersey Shore
524
11
52
42
92
72
129
101
157
128
181
152
205
174
227
196
249
216
269
237
286
Delaware Bay Total
497
16
54
45
90
72
121
98
139
121
156
140
173
157
188
172
202
186
214
199
224
New Jersey
261
9
38
30
67
51
92
72
106
91
119
105
132
118
142
129
153
139
161
148
167
Delaware
236
7
16
15
23
20
29
26
33
31
37
35
41
39
46
43
49
47
53
51
57
Delaware River Total
216
12
41
33
64
49
85
65
93
80
101
90
108
97
115
103
122
109
127
116
133
Delaware: fresh
5
0
1
1
1
1
2
2
2
2
2
2
3
2
3
3
3
3
3
3
3
Delaware: saline
69
1
3
3
3
3
4
4
5
4
5
5
6
5
6
6
7
6
7
00
New Jersey: fresh
29
0
10
6
20
12
29
19
31
25
34
29
37
32
40
34
43
37
46
39
48
New Jersey: saline
108
10
25
22
35
30
44
37
47
44
50
47
52
50
55
52
57
54
59
56
62
Pennsylvania
6
1
2
1
4
3
6
00
6
9
7
10
8 11
9
12
9
12
10
12
Atlantic Coast of
Del-Mar-Va Total
757
3
13
13
26
24
38
36
49
47
57
55
64
62
70
68
74
73
78
77
82
-------
133 ]
21
34
27
1132
13
497
142
259
95
0
622
118
45
458
96
4695
710
7401
4486
7401
; Area of Land Close to Sea Level by Region (continued)
Meters above Spring High Water
low high low high low high low high low high low high low high low high
2
0
1
44
1
29
2
26
1
0
14
1
2
12
5
4
5
151
2
88
9
69
10
0
60
12
5
43
6 21
2083 2625
197 255
2374 3221
945 2136
2374 3221
8819 10857
4
5
4
143
2
92
7
79
6
0
49
8
4
37
10
259
3
137
18
101
18
0
119
21
11
87
20 37
2772 3039
275
3351
315
3940
2218 3585
3351 3940
11069 13025
7
9
9
231
2
136
14
110
12
0
92
14
9
69
10
13
16
375
4
194
28
137
29
0
178
30
18
129
33 47
3130 3320
335 374
3959 4512
9
14
13
334
3
189
23
147
19
0
141
21
15
106
12
17
19
489
4
244
38
166
40
0
240
37
25
178
42 57
3401 3562
393 429
4487 5001
11
18
18
425
4
231
32
170
28
0
190
27
21
142
14
22
21
590
5
282
48
182
51
0
302
44
28
230
52 66
3640 3789
448 481
4963 5449
13
22
20
510
5
267
42
188
36
0
239
34
26
179
16
26
23
699
6
329
62
206
61
0
363
52
31
280
61 73
3852 3984
495 525
5381 5864
15
26
22
618
6
315
57
213
45
0
296
40
30
227
17
28
24
809
8
377
79
228
70
0
424
59
35
330
69 81
4045 4173
538 568
5788 6266
16
29
23
724
7
361
74
232
55
0
356
47
33
276
18
31
25
911
9
420
99
242
79
0
481
70
38
373
76 88
4235 4352
583 616
6189 6652
Cumulative (total) amount of land below a given elevation
3498 5089
3959 4512
1295715101
4903 6569
4487 5001
1489017070
6272 8008
4963 5449
1673418957
7567 9463
5381 5864
18448 20826
8991 10994
5788 6266
20279 22760
10520 12370
6189 6652
22208 24521
-------
CHAPTER 2. SITE-SPECIFIC SCENARIOS FOR
WETLANDS ACCRETION IN THE MID-ATLANTIC
-------
2.1. Site-Specific Scenarios for Wetlands
Accretion as Sea Level Rises in the Mid-Atlantic
Region
Authors: Denise J. Reed
Dana A. Bishara
Department of Earth and Environmental Sciences, University of New Orleans
Donald. R. Cahoon, U.S. Geological Survey
Jeffrey Donnelly, Woods Hole Oceanographic Institution
Michael Kearney, University of Maryland
Alexander S. Kolker, State University of New York, Stony Brook
Lynn L. Leonard, University of North Carolina, Wilmington
Richard A. Orson, Orson Environmental Consultants
J. Court Stevenson, University of Maryland
This section should be cited as:
Reed, D.J., D.A. Bishara, D.R. Cahoon, J. Donnelly, M. Kearney, A.S. Kolker, L.L. Leonard,
R.A. Orson, and J.C. Stevenson. 2008. Site-Specific Scenarios for Wetlands Accretion as
Sea Level Rises in the Mid-Atlantic Region. Section 2.1 in: Background Documents
Supporting Climate Change Science Program Synthesis and Assessment Product 4.1, J.G.
Titus and E.M. Strange (eds.). EPA 430R07004. U.S. EPA, Washington, DC.
-------
2.1.1 Introduction
One of the key questions to be addressed by the
U.S. Climate Change Science Program's (CCSP)
sea level rise synthesis and assessment is "To
what extent can wetlands vertically accrete and
thus keep pace with rising sea level; that is, will
sea level rise cause the area of wetlands to
increase or decrease?" Although predictive
models for wetland soil response to sea level rise
have been available for some years (e.g., Krone,
1987) and have been amplified to encompass
biotic as well as mineral contributions to vertical
soil building (e.g., Morris et al., 2002; Rybzyck
and Cahoon, 2002), applying these models over
wetland landscapes requires detailed information
on wetland biogeomorphic processes. Many site-
specific field studies can provide this
information for local areas, but available models
cannot, at present, predict coastal wetland
response to sea level rise over large areas.
To support the CCSP efforts and provide
spatially explicit landscape scale predictions of
coastal wetland response to future sea level rise,
an expert panel approach was used. EPA's
Climate Change Division (CCD), which has the
lead on the sea level rise synthesis and
assessment product for CCSP, determined that
the focus would be on the Mid-Atlantic (defined
here as the Atlantic shore of Long Island to
Virginia). They also provided three sea level rise
scenarios for the panel to consider:
• Current rates: rates and the regions to which
the rates apply were to be determined by the
panel;
• An increase of 2 mm per year above the
current rates (termed here midrange sea level
rise);
• An increase of 7 mm per year above the
current rates (termed here high-range sea
level rise).
The panel's task was to assess for the Mid-
Atlantic region how coastal wetlands would
respond to changes associated with these sea
level rise scenarios. To support this effort, a
literature review of published, and in some cases
unpublished, reports of recent and historical
accretion rates for the Mid-Atlantic was
conducted.
Expert Panel Approach
The panel consisted of a group of experts with
first-hand knowledge of the coastal wetland
geomorphic processes in the Mid-Atlantic. They
convened in a 2-day workshop in February 2006
at the Patuxent Wildlife Research Center in
Maryland. Their deliberations were designed to
ensure that conclusions were based on an
understanding of the processes driving marsh
survival in the face of sea level rise and how the
magnitude and nature of these processes might
change in the future owing to the effects of
climate change and other factors.
To ensure a systematic approach across regions
within the Mid-Atlantic and throughout the
workshop, the following procedures were used:
• A series of geomorphic settings, and in some
cases subsettings, was identified to assist in
distinguishing between the different process
regimes controlling coastal wetland
accretion.1 The settings were chosen to
encompass the vast majority of coastal
wetlands found on the Mid-Atlantic.
'The term accretion is used in this report to describe net
change in the relative elevation of the marsh surface in the
tidal frame. Individual studies have distinguished between
specific measures of elevation change (documented against
a fixed datum) or surface accretion where methods focus
on accumulation of material on or near the marsh surface.
-------
136 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
A suite of processes potentially contributing
to marsh accretion in the Mid-Atlantic was
established and described in general terms. In
addition, likely future changes in current
process regimes due to climate change were
outlined.
The Mid-Atlantic was divided into a series of
regions based on similarity of process regime
and current sea level rise rates. The current
rate of sea level rise and the source of the
tide gauge data supporting that rate were
identified for each region. This rate defined
the first of the sea level rise scenarios and
provided the baseline for the mid-range and
high-range rates.
Within each region, geomorphic settings
were delineated by drawing polygons onto
1:250,000 scale USGS topographic paper
maps, and the fate of the wetlands within
these settings under the three sea level rise
scenarios was agreed upon. The fate of the
wetlands was allocated to the categories
described in Table 2.1.1 based on the
following potential outcomes:
o Keeping pace—wetlands will not be
submerged by rising sea levels and will
be able to maintain their relative
elevation.
o Marginal—wetlands will be able to
maintain their elevation only under
optimal conditions. Depending on the
dominant accretionary processes, this
might mean frequent inputs of sediments
from storms or floods, or the
maintenance of hydrologic conditions
conducive to plant productivity. Given
the complexity and inherent variability of
factors (climatic and otherwise)
influencing wetland accretion, the fate of
these wetlands cannot be predicted by the
panel. However, under the best of
circumstances they are expected to
survive.
o Loss—wetlands will be subject to
increased hydroperiod beyond that
normally tolerated by the vegetative
communities, leading to deterioration and
conversion to open water.
• The paper maps were delivered to the EPA
project officer, who defined a procedure for
converting the polygons into a GIS data base,
designed thematic map categories and map
legends, and contracted with Stratus
Consulting to prepare the maps that appear in
this report. For further details of how the
maps were created and the GIS output
associated with this report, see Titus et al.
(Section 2.2).
Report Content
This report summarizes the background
information provided to the panel, and describes
the geomorphic settings and accretionary
processes identified by the panel for the Mid-
Atlantic. The purpose of this report is not to
provide a complete synthesis of the data
assembled to inform the group or to reiterate the
extensive literature of coastal wetland
accretionary processes. The main focus of the
report is to provide narrative discussion of the
rationale behind the categories of wetland
response to sea level scenarios depicted in the
maps. This is provided by the regions defined by
the panel, and includes a rationale for the
selected current rate of sea level rise, the
assignment of geomorphic settings and
associated accretionary processes, and a
summary of the spatial distribution of the
response categories assigned within each region
by the panel.
-------
[ SECTION 2.1 137 ]
Table 2.1.1. Categories of Wetland Response to Sea Level Scenarios
Category
Summary Outcomes
Current Midrange High-
Range
Description
Loss under current
rates
L
These wetlands are not sustainable under
current circumstances and they are not expected
to be reestablished by natural processes in the
future.
Marginal undercurrent
rates, loss under
midrange scenario
M
L
These wetlands are marginal now and will be lost
if sea level rise rates increase by 2 mm/yr.
Marginal undercurrent
rates, marginal or loss
under midrange
scenario
M
M-L
These wetlands are marginal now and will be
able to keep pace only under the best of
circumstances if sea level rise rates increase by
2 mm/yr.
Keeping pace under
current rates, marginal
under midrange, loss
under high- range
scenario
K
M
L
These wetlands are currently keeping pace and
will continue to do so only under the best of
circumstances if sea level rise rates increase by
2 mm/yr. They will be lost if sea level rise rates
increase by 7 mm/yr.
Keeping pace under
current and midrange
rates, loss under high-
range scenario
K
K
L
These wetlands are currently keeping pace and
will continue to do so if sea level rise rates
increase by 2 mm/yr. They will be lost if sea level
rise rates increase by 7 mm/yr.
Keeping pace under
current and midrange
rates, marginal or loss
under high-range
scenario
K
K
M-L
These wetlands are currently keeping pace and
will continue to do so if sea level rise rates
increase by 2 mm/yr. They will keep pace only
under the best of circumstances or in local areas
if sea level rise rates increase by 7 mm/yr.
Keeping pace under
current and midrange
rates, marginal under
high-range scenario
K
K
M
These wetlands are currently keeping pace and
will continue to do so if sea level rise rates
increase by 2 mm/yr. They will keep pace under
the best of circumstances if sea level rise rates
increase by 7 mm/yr
Keeping pace under all
sea level rise scenarios
K
K
K
These wetlands are currently keeping pace and
will continue to do so if sea level rise rates
increase by 2 mm/yr or 7 mm/yr.
L - Loss, M - Marginal, K - Keeping Pace (see text for definitions).
-------
2.1.2 Recent and Historical Rates
Site-specific field studies of coastal wetland
response to sea level rise have been conducted
across the Mid-Atlantic. Several types of
techniques are used in these studies:
• Historical rates of material accumulation
within the wetland soil. These studies use
defined depth horizons within cores. The
horizons are dated based on radiometric
dating with the decay rate of the radionuclide
(e.g., 137Cs, 210Pb, 14C) determining the
period over which the rates are calculated
(e.g., Lynch et al., 1989; Rooth et al., 2003).
• Surficial accretion of material. Vertical
increments of material are measured relative
to the surface over study-defined periods,
usually months to several years. A marker is
placed on the marsh surface at the beginning
of the study and buried over time (e.g.,
Cahoon and Turner, 1989).
• Net change in marsh elevation relative to a
fixed datum. These techniques, such as the
Sediment Erosion Tables (SETs) (Boumans
and Day, 1993) or Rod Surface Elevation
Tables (Cahoon et al., 2002), measure the net
result of processes both increasing (e.g.,
surface sediment deposition, soil peat
accumulation) and decreasing (e.g.,
compaction, decomposition) elevation. The
datum is established at the start of the study
and measurements are made periodically,
usually at least annually, relative to this
baseline.
Reed and Cahoon (1993) provide a more detailed
account of the techniques and their assumptions
concerning rates of change within marshes.
Table 2.1.2 lists the studies of wetland accretion
in the Mid-Atlantic identified for this study and
includes information on the methodology used as
well as some basic descriptive terms for the
studied marshes (derived from the source
publications). Note that the term "accretion" is
used in Table 2.1.2 generally, as in the rest of the
report, to embrace rates of vertical change no
matter which technique is used. In some studies
multiple methods are used to derive several
accretion rates at the same location. The results,
presented here state by state, were intended to
provide contextual information to the expert
panel rather than define areas of geomorphic or
accretionary commonality.
For coastal wetlands in New York, most of the
identified studies used 210Pb dating to derive
accretion rates. None of the studies for which
primary sources were found included accretion
rates above 5 mm/yr, with most rates between 2
and 4 mm/yr. Interestingly, a number of separate
papers on Flax Pond marshes, examining
accretion in different marsh types and settings,
show rates varying within the Flax Pond system
from 1.6 to 6.3 mm/yr. The very few studies
found for marshes in New Jersey showed great
variation in rates from 3.8 mm/yr to more than
13 mm/yr.
For Delaware, rates of 2-7 mm/yr are common,
with some higher rates found at Indian River
Bay, Little Lagoon Marsh and Port Mahon (Kraft
et al., 1992). Other studies in Delaware have
measured accretion rates >10 mm/yr but these
are largely restored marshes building quickly
toward an equilibrium tidal elevation (R.A.
Orson, Orson Environmental Consultants,
unpublished information). Although previous
work (e.g., Pethick, 1981; Krone, 1987) suggests
that marshes low in the tidal frame are likely to
experience higher accretion rates, using these
restored marsh rates to assess future response to
sea level rise in established marshes would
require an assumption about marsh elevation in
the tidal frame that could not be supported by
data. Most of the rates documented from primary
-------
[ SECTION 2.1 139 ]
sources for Delaware are based on radiometric
dating. This technique incorporates any
compaction of soil layers above the dated
horizon and as such can be considered a more
conservative measure of accretion than
accumulation over a surficial marker horizon.
Radiometric dating also averages rates of
accretion over several decades or more, reducing
the influence of episodic events on the measured
rates.
For Maryland, more of the data shown in Table
2.1.2 are derived from short-term measurements,
some for periods as short as 6 months. Rates
range from very high, e.g., >15 mm/yr of
accretion at fresh marshes in Jug Bay (Boumans
et al., 2002), to highly negative, e.g., a loss of
more than 15 mm in Spartinapatens marshes on
the Patuxent estuary (Childers et al., 1993).
Longer term rates based on pollen or radiometric
dating show positive accretion (negative rates
can only be derived from elevation change
measures such as SET or RSET) of between 1
and 10 mm/yr with great variation from site to
site.
Both back barrier lagoon and riverine marshes
have been studied in Virginia using marker
horizons, SETs, and 210Pb dating. The study by
Darke and Megonigal (2003) on Walkerton
Marsh shows a rate of accretion over a marker
horizon of only 0.12 mm/yr. This is a fresh
riverine system, and it is possible that surface
elevation may be more driven by below-ground
processes and not reflected in the surficial
accumulation measured above the marker.
-------
[ 140 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Table 2.1.2. Summary of published sources of accretion rates, by state, identified as part of this
study.
Location
Accretion
Rate
(mm/yr)
Method
Marsh Type
fresh/
low/ brackish/ Dominate Plant
high salt Community
Geomorphic
Setting
Source
DELAWARE
Assawoman
Bay lagoon
marsh
3.5-8.2
Lead 210 &
Cesium 137
low
Spartina
alterniflora
lagoon
Kraft et al., 1992
Boat house
cove
4.00
salt
estuarine
Carey, 1996 (in
Nikitina et al.,
2000)
Delaware
Bay
3.0-5
Lead 210
salt
bay
Church et al.,
1987
Delaware
Bay
4-5
bay
Kraft et al., 1989
(in Fletcher et al.,
1990)
Delaware
Wildlands
3.40
salt
Carey, 1996 (in
Nikitina et al.,
2000)
Duck Creek
1.30
radiocarbon
dating
estuarine
Pizzuto and
Rogers, 1992
Duck Creek
3.2-3.4
Lead 210 &
Cesium 137
low
Spartina
alterniflora
estuarine
Kraft et al., 1992
Great Marsh
2.9-8.2
Lead 210 &
Cesium 137
low
Spartina
alterniflora
Kraft et al., 1992
Indian River
Bay
2.3-
10.7
Lead 210 &
Cesium 137
low
Spartina
alterniflora
bay
Kraft et al., 1992
Indian River
Bay lagoon
5.0-6.9
Lead 210 &
Cesium 137
low
Spartina
alterniflora
lagoon
Kraft et al., 1992
Leipsic River
2.90
Lead 210
low
salt
Spartina
alterniflora
estuarine
Nikitina et al.,
2000
Lewes
>10
Cesium 137
estuarine
Brickman, 1978
(in Stevenson et
al., 1986)
Lewes
3.30
salt
estuarine
Carey, 1996 (in
Nikitina et al.,
2000)
Lewes
4.70
Lead 210
salt
estuarine
Church et al.,
1981
Lewes
5.00
marker
horizon (<1
year)
estuarine
Stumpf, 1983
Lewes
2.0-3.6
Lead 210 &
Cesium 137
low
Spartina
alterniflora
estuarine
Kraft et al., 1992
Little Lagoon
marsh
2.8-10
Lead 210 &
Cesium 137
low
Spartina
alterniflora
lagoon
Kraft et al., 1992
Mispillion
River marsh
3.6-5.3
Lead 210 &
Cesium 137
low
Spartina
alterniflora
estuarine
Kraft et al., 1992
No specific
location
5.1-6.3
marker
horizon
Stearns &
MacCreary, 1957
No specific
location
5.00
Lead 210
low
salt
Lord, 1980 (in
Armentano et al.,
1988)
Port Mahon
0.04
high
estuarine
Khalequzzaman,
1989 (in Fletcher
et al., 1993)
-------
[ SECTION 2.1 141 ]
Marsh Type
Location
Accretion
Rate
(mm/yr)
Method
low/
high
fresh/
brackish/
salt
Dominate
Plant
Community
Geomorphic
Setting
Source
Port Mahon
2-19.1
Lead 210 &
Cesium 137
low
Spartina
alterniflora
estuarine
Kraft et al., 1992
Pot Nets North
3.90
salt
Carey, 1996 (in
Nikitina et al., 2000)
Rehoboth Bay
3.3-7.6
Lead 210 &
Cesium 137
low
Spartina
alterniflora
bay
Kraft et al., 1992
Rehoboth Bay
2.60
Lead 210
lagoon
Chrzastowski, 1986
(in Schwimmer and
Pizzuto, 2000)
Rehoboth Bay
lagoon
2.3-5.9
Lead 210 &
Cesium 137
low
Spartina
alterniflora
lagoon
Kraft et al., 1992
South Bowers
Marsh
1.8-7.8
Lead 210 &
Cesium 137
low
Spartina
alterniflora
estuarine
Kraft et al., 1992
Wolfe Glade
0.3-3.0
radiocarbon
dating
estuarine
Fletcher et al., 1993
Wolfe Runne
3.70
salt
Carey, 1996 (in
Nikitina et al., 2000)
Woodland
Beach
2.1-6.8
Lead 210 &
Cesium 137
low
Spartina
alterniflora
estuarine
Kraft et al., 1992
MARYLAND
Blackwater
1.7-3.6
Lead 210
estuarine
Stevenson et al.,
1985
Chincoteague
Bay
1.50
back barrier Bartberger, 1976 (in
bay Orson et al., 1985)
Deal Island
Management
Area
4.0- SET
6.4- marker
SET & marker
horizon (6 mo)
salt
Spartina
alterniflora
estuarine
Rooth and
Stevenson, 2000
Jug Bay
SET & marker
11.19-SET horizon (2
16.59-markeryears)
mid
fresh
Typha
angustifolia &
Typha latifolia
estuarine
Boumans et al.,
2002
Jug Bay
SET & marker
5.39- SET horizon (2
9.39- marker years)
low
fresh
Nuphar
advena
estuarine
Boumans et al.,
2002
Jug Bay
-11.1- SET
1,2-marker
SET & marker
horizon (2
years)
high
fresh
Alnus
serrulata
estuarine
Boumans et al.,
2002
Jug Bay
4.30
carbon 14 &
pollen analysis
high
fresh
Typha
angustifolia &
Typha latifolia
estuarine
Khan and Brush,
1994
Jug Bay
4.20
carbon 14 &
pollen analysis
low
fresh
Nuphar
advena
estuarine
Khan and Brush,
1994
Kenilworth
Marsh
1.75
SET (2 years)
riverine
Hammerschlag
(personal
communication,
USGS)
Kingman
Marsh
-5.00
SET (2 years)
riverine
Hammerschlag
(personal
communication,
USGS)
Kings Creek
Preserve
4.0-9.5
Lead 210
salt
Phragmites
australis
estuarine
Rooth et al., 2003
Lower
Pocomoke
River
1.50
pollen dating
estuarine
Douglas, 1985 (in
Stevenson and
Kearney, 1996)
-------
[ 142 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Marsh Type
Accretion
fresh/
Dominate
Rate
low/
brackish/
Plant
Geomorphic
Location
(mm/yr)
Method
high
salt
Community
Setting
Source
Sp. patens,
Spartina
cynosuroides
& Scirpus
Monie Bay
1.5-6.3
pollen dating
brackish
olneyi
estuarine
Ward etal., 1998
Sp. patens,
Spartina
Lead 210,
cynosuroides
Cesium 137 &
& Scirpus
Kearney &
Monie Bay
7.2-7.8
pollen dating
brackish
olneyi
estuarine
Stevenson, 1991
Scirpus
Muddy Creek
3.33
SET (2 years)
high
brackish
olneyi
estuarine
Childers et al., 1993
Phragmites
australis &
Nanticoke
high-
Spartina
Kearney and Ward,
River Estuary
1.8-7.4
pollen dating
low
brackish
cynosuroides
estuarine
1986
Patuxent River
-1.40
SET (2 years)
fresh
estuarine
Childers et al., 1993
Spartina
Patuxent River
4.40
SET (2 years)
patens
estuarine
Childers et al., 1993
Spartina
Patuxent River
24.00
SET (2 years)
patens
estuarine
Childers et al., 1993
Patuxent River
20.70
SET (2 years)
Phragmites
estuarine
Childers et al., 1993
Spartina
Patuxent River
-16.20
SET (2 years)
patens
estuarine
Childers et al., 1993
Patuxent River
-14.50
SET (2 years)
mudflat
Childers et al., 1993
Patuxent River
52.00
SET (2 years)
mudflat
Childers et al., 1993
Brush et al., 1982
(in Orson et al.,
Potomac River
1.7-15.5
estuarine
1990)
NEW JERSEY
Psuty (personal
Great Egg
communication,
Harbor
6.0-10
Cesium 137
lagoon
Rutgers University)
3.80 (no
specifics of
SET & marker
SET or
horizon (3
Spartina
back barrier
Little Beach
marker)
years)
high
alterniflora
lagoon
Erwin et al., 2006
Princeton/
Cesium 137,
Jefferson
Lead 210 &
marsh
12-13.2
pollen/historical
fresh
estuarine
Orson et al., 1990
NEW YORK
Spartina
Cochran et al.,
Alley Pond
3.50
Lead 210
high
salt
patens
estuarine
1998
back barrier
Carmans River
2.7-3.3
Lead 210
marsh
Kolker, 2005
Spartina
Cochran et al.,
Caumsett Park
4.10
Lead 210
high
salt
patens
estuarine
1998
Spartina
Armentano and
Flax Pond
4.7-6.3
Lead 210
low
salt
alterniflora
estuarine
Woodwell, 1975
Spartina
Cochran et al.,
Flax Pond
2.10
Lead 210
high
salt
patens
estuarine
1998
Spartina
Flax Pond
2.5-4.7
historical record
brackish
alterniflora
estuarine
Flessa et al., 1977
Flax Pond
1.60
Lead 210
estuarine
Kolker, 2005
-------
[ SECTION 2.1 143 ]
Marsh Type
Accretion
fresh/
Dominate
Rate
low/ brackish/
Plant
Geomorphic
Location
(mm/yr)
Method
high salt
Community
Setting
Source
Flax Pond
4.00
Lead 210
estuarine
Muzyka, 1976 (in
Richard, 1978)
Flax Pond
2-4.25
marker horizon
(1.5 years)
estuarine
Richard, 1978
Fresh Pond
4.30
Lead 210
estuarine
Clark and
Patterson, 1985
Goose Creek
2.40
Lead 210
high
salt
Spartina
patens
estuarine
Cochran et al.,
1998
Hempstead
Bay
1.4-5
Lead 210
estuarine
Kolker, 2005
Hubbard
County Park
2.3-3
Lead 210
back barrier
marsh
Kolker, 2005
Hunter Island
1.10
Lead 210
high
salt
Spartina
patens
estuarine
Cochran et al.,
1998
Jamaica Bay
2.8-4.4
Lead 210
lagoon
Kolker, 2005
Jamaica Bay
5.0-8
high
lagoon
Zeppie, 1977 (in
Hartig et al., 2002)
Nissequogue
River
3.5-4
Lead 210
estuarine
Kolker, 2005
Shelter Island
3.00
Lead 210
high
salt
Spartina
patens
estuarine
Cochran et al.,
1998
Stony Brook
Harbor
2.4-2.8
Lead 210
high-
low
estuarine
Cademartori, 2000
(in Hartig et al.,
2002)
Youngs Island
4.6-4.8
Lead 210
estuarine
Cademartori, 2000
(in Kolker, 2005)
Youngs Island
3.5-4.8
Lead 210
estuarine
Cochran et al.,
1998 (in Kolker,
2005)
VIRGINIA
Gleason
Marsh
0.27
marker horizon
(19 months)
fresh
Sp.
cynosuroides
& Eliocharis
quadrangulata
riverine
Darke and
Megonigal, 2003
Mockhorn
12.70 (no
specifics on
SET or
marker)
SET & marker
horizon (4
years)
high
Spartina
aiternifiora
back barrier
lagoon
Erwin et al., 2006
Oyster
1-2.2
Lead 210
salt
Spartina
aiternifiora
back barrier
marsh
Oertel et al., 1989
Wachapreague
SET & marker
2.3- SET horizon (4
8.5- marker years)
high
Spartina
aiternifiora
back barrier
lagoon
Erwin et al., 2006
Walkerton
Marsh
0.12
marker horizon
(19 months)
fresh
Pontedaria
cordata &
Acorus
calamus
riverine
Darke and
Megonigal, 2003
-------
2.1.3. Settings and Processes
The fate of coastal wetlands in the Mid-Atlantic
will be determined in large part by the way in
which the accretionary processes change with
climate drivers. These processes vary by
geomorphic setting. The expert panel identified
five primary geomorphic settings with several
subsettings for the coastal wetlands of the Mid-
Atlantic:
• Tidal Fresh Forests (FF)
• Tidal Fresh Marsh (FM)
• Estuarine/Brackish Channelized Marshes
(ES)
o Meander
o Fringing
o Island
• Back Barrier Lagoon Marsh (BB)
o Back Barrier/Other
o Active Flood Tide Delta
o Lagoonal Fill
• Saline Marsh Fringe (SF)
This classification is similar to global scale
assessments of others (e.g., Woodroffe, 2002;
Cahoon et al., 2006) but is more detailed in its
consideration of subsettings to reflect the finer
scale of expert panel assessment.
FF and FM are distinguished based on vegetative
type (forested vs. herbaceous) and the salinity of
the area. ES marshes are brackish and occur
along channels rather than open coasts. ES
Meander marshes would be those bordering
meandering tidal rivers, and ES Fringing are
those bordering wider open channels where tidal
flow is not focused in a specific thalweg. ES
Island marshes are, as the term implies, marsh
islands within tidal channels. BB marshes
occupy fill within transgressive back barrier
lagoons. Where the fill is attached to barrier
islands, the marshes are Back Barrier/Other, and
Flood Tide Deltas are marshes forming landward
of tidal inlets. Lagoonal Fill is frequently
abandoned flood tide deltas where the inlet is
closed and marsh is not supplied with sediment
directly from the inlet. SF marshes are
transgressive salt marshes bordering uplands,
mostly on the landward side of tidal lagoons.
Accretionary processes vary among settings. The
panel identified nine basic processes that
influence the ability of wetlands in these settings
to keep pace with sea level rise:
• Storm sedimentation. Storm-driven
sedimentation typically occurs on time scales
of years to decades, resulting in inputs of
sediments into marshes and forest greater
than those that occur under more common
process regimes. The source can be
sediment-laden floodwaters associated with
high precipitation in adjacent watersheds
(e.g., Pasternack and Brush, 1998), local
resuspension within coastal bays (e.g., Reed,
1989), or overwash of barrier beaches to
bordering marshes (e.g., Donnelly et al.,
2001). The latter effect is more important to
back barrier marshes than to flood tide deltas.
Within ES marshes, storm flooding can lead
to both the import and export of material.
• Tidal Fluxes of Sediment. Although tidal
exchange is limited at the heads of estuaries,
many FF and FM marshes in the Mid-
Atlantic are potentially exposed to tidal
sediment input. Ebb dominance can lead to
export of sediment from the system through
subtidal channels and the deepening of these
channels, especially in BB and SF marshes
(Aubrey and Weishar, 1998). This reduces
sediment availability within the lagoons for
resuspension and transport to marshes during
storms. Within ES marshes, tidal exports
have been shown to result in a substantial
loss of sediment in severely stressed marshes
-------
[ SECTION 2.1 145 ]
(Stevenson et al., 1988). It is possible that as •
the sea level rises, wetland systems could
become flood dominated. The role of tidal
flux in influencing accretion would then be
modulated by the available sediment supply
to the system (e.g., fluvial and oceanic
sources, described separately).
• Peat Accumulation. In freshwater systems •
where productivity is high, the accumulation
of organic material in the wetland soil is a
key driver of accretion. However, both
microbial degradation of marsh peat and
plant die-offs can lead to a drop in marsh
surface elevation (e.g. Nyman et al., 1993;
DeLaune et al., 1994). This process is most
important in FM, and can also be impacted
by changes in salinity increasing the potential
for organic matter decomposition by sulfate-
reducing bacteria. However, the Spartina
patens marshes common in ES are also
characterized by organic soils. BB and SF
marshes are dominated by Spartina
alterniflora. Peat accumulation may not be a
primary driver of accretion in these systems,
but organic-rich soils still occur.
• Ice Rafting. Ice accumulation and movement
during the winter months strip remnant
vegetation from the marsh surface, exposing
the marsh surface. When marsh soil is rafted
with moving ice floes, it can contribute
sediment to the area where the ice floe melts, •
sometimes on the marsh surface (Wood et al.,
1989). The effect of this process on accretion
is localized and can be both erosive and
accretionary.
• Nutrient Supply. Most wetlands in the Mid-
Atlantic are not nutrient limited, so changes
in the supply of nutrients do not have a
substantial effect on accretion. However, in
sandy substrates where soil organic matter is
limited, e.g., BB and some SF marshes, it can
increase plant productivity (Bertness, 1999).
It has less of a role in FF, FM, and ES soils •
that are dominated by fine sediments and are
more organic in nature.
Groundwater. Groundwater can supply
freshwater and nutrients to inshore bays and
tidal wetlands (e.g., Bokuniewicz, 1980).
Reduction in salt stress and increased
nutrition can increase the productivity of
some marshes, but this effect is very
localized.
Fluvial sediment supply. The role of fluvial
sediment delivery to tidal wetlands during
nonstorm conditions varies across the
estuarine gradient. In FF and FM, these
inputs can occur several times per year and
thus provide a recurring source of sediment
(Pasternack and Brush, 1998). Within the
estuary, ES marshes in the vicinity of an
estuarine turbidity maximum are most likely
to benefit as the fluvial sediment is trapped
within a zone of the estuary and is more
available to marshes in that area. Local
streams can also supply individual ES
marshes with sediment. Toward the coast in
BB and SF systems, fluvial input of sediment
is generally minimal, but it could be locally
important where streams discharge directly
into coastal lagoons. In many systems, fluvial
sediment supplies are strongly affected by
dams and local land use practices. In these
systems, future fluvial sediment supplies will
be affected by jurisdictional responses to
climate change.
Herbivory. Although the effects of
herbivory on tidal marshes can be dramatic
(Ford and Grace, 1998) and their role in
limiting regeneration of wetland forests is of
concern, the effects of herbivory on
accretionary processes are indirect and most
likely important only locally. Some recent
work has suggested that grazing by snails can
be an important control on above-ground
productivity in salt marshes (Silliman and
Zieman, 2001); the effect on accretion has
not been documented.
Oceanic Sediment Inputs. The import of
sediment from the ocean by tides and during
storms can be of importance in SF and BB
systems, especially flood tide deltas.
-------
2.1.4. Wetland Responses to Sea Level Scenarios
Table 2.1.1 describes the potential wetland
responses associated with the three sea level
scenarios. The regions delineated by the expert
panel have been described according to
geomorphic setting and wetland response. In all
cases the panel's assessment of wetland response
assumes that human activities that influence
marsh accretionary processes (e.g., dredged
channels that act as sediment sinks and limit the
supply of sediment for accretion) do not change
in the future. The exception to this is where
climate change is considered to influence the
activity (e.g., land use) and thus the accretionary
processes. Each section includes the panel's
rationale and narrative supporting the current sea
level rise rate, the character and distribution of
geomorphologic settings, and wetland response
to future sea level rise scenarios.
New York - Long Island
This region encompasses the tidal marshes on
the Atlantic shore of Long Island. The most
appropriate tide gauge to document current sea
level rise trends is New York City. The current
rate of sea level rise for the area was determined
to be 3 mm/yr, making the two future rates
considered 5 mm/yr and 10 mm/yr. The
geomorphic setting for these marshes is either
BB or SF (Figure 2.1.1).
The dominant accretionary processes are storm
sedimentation and peat accumulation. Future
climate change will result in an increase in the
magnitude of coastal storms, due to increasing
sea-surface temperatures, and their frequency
will be at least as common as at present (Webster
et al., 2005). Thus, there is likely to be a net
increase in storm sedimentation in marshes in
this region. Although sea level rise may drive an
increase in peat accumulation, local
anthropogenic impacts to sediment geochemistry
may currently be leading to peat deterioration.
The response of marshes in this region to climate
change depends in large part on their ability to
cope with the nontrivial anthropogenic impacts
caused from the New York City Metropolitan
Region (e.g., Kolker, 2005). Any increase in
vertical accretion driven by peat accumulation
will occur only up to a threshold level. This
threshold is currently unknown for this region
and has not been assessed for such impacted
marshes as those on Long Island. It has been
identified as -10 mm/yr for Rhode Island
marshes (Bricker-Urso et al., 1989) and >12
mm/yr for marshes in the southeastern United
States (Morris et al., 2002).
In addition, other accretionary processes are also
expected to change (Scavia et al., 2002):
• Tidal fluxes may shift to more ebb
dominance as the tidal prism increases,
exporting more sediment.
• Ice effects will diminish in importance as
climate warms, reducing both destructive and
constructive influences.
• Nutrient delivery from coastal watersheds is
likely to increase, because both climatic
effects and land use changes result in greater
runoff, though it is highly dependent on local
land use practices. This increase could
stimulate productivity in local marsh areas.
• Fluvial sediment inputs will be equal to or
greater than present inputs and may
positively influence marsh accretion locally,
but are also dependent on local land use
practices.
Figure 2.1.2 illustrates that the only marshes in
this region that are expected to survive the
highest rate of future sea level rise are BB
lagoonal fill marshes near Gilgo and Cedar
islands, and those immediately behind Long
-------
[ SECTION 2.1 147 ]
Beach. These are areas where marshes are
currently expanding, indicating adequate
sediment supply from overwash and tidal inlets.
BB lagoonal fill marshes in east and west
Jamaica Bay, and SF marshes fringing Jamaica
Bay, Middle Bay, and East Bay, will be able to
keep pace with midrange sea level rise but are
likely to be lost if sea level increases to 10
mm/yr. These marshes are supplied with
sediment from storm reworking but also require
peat accumulation to retain their elevation.
Marshes in the western part of Jamaica Bay
mostly comprise dredge fill and are subject to
loss factors other than insufficient vertical
accretion. A rate of 10 mm/yr is most likely too
great for them to survive. The BB flood tide
delta marshes adjacent to Jones Inlet will be
marginal at the higher rate of rise and may be
lost, but are likely to survive midrange
predictions. Extensive areas of marsh, both BB
and SF, surrounding Great South Bay, Moriches
Bay, and Shinnecock Bay, as well as those east
of Southampton, are keeping pace with current
rates of sea level rise but will be marginal if rates
increase to 5 mm/yr. Most of these are salt
marshes, and episodic supply of sediment from
storms and organic accumulation may not be
enough to compensate for even an increase of 2
mm/yr over current trends. Loss rates are already
high in the marshes of central Jamaica Bay (38-
78 percent; Hartig et al., 2002). There is no
expectation that these marshes will become more
viable in the future. Many of the marshes in this
region are highly susceptible to human activities
both directly and indirectly, and their survival,
especially under marginal conditions, will
largely depend on how development pressures
and other land use changes influence patterns of
sediment supply and dispersal within this region.
Raritan Bay/New York Bay
This region encompasses the tidal marshes of
Raritan Bay and New York Bay and extends
north to the Hackensack Meadows. The most
appropriate tide gauge to document current sea
level rise trends is Sandy Hook, New Jersey. The
current rate of sea level rise for the area was
determined to be 4 mm/yr, making the two future
rates considered 6 mm/yr and 11 mm/yr. The
geomorphic setting for these marshes includes
small areas of FM along the South River and
Raritan River, with most of the area being ES
and SF marshes (Figure 2.1.3).
The dominant accretionary processes are peat
accumulation and fluvial sediment inputs.
Vertical accretion driven by peat accumulation is
also expected to increase in the future in
response to increased sea level. However, in
most of these marshes, this increase will occur
only up to a threshold level. The exception is the
FM area where peat accumulation should allow
marshes to accrete and even expand in the face
of high-range sea level rise. The threshold level
for ES and SF marshes is currently unknown for
this region, although lower salinity ES marshes
will be less subject to the threshold and more
similar to FM. Fluvial sediment inputs are
expected to increase in this area as climate
changes cause precipitation events to be more
intense and periodic, resulting in flashy runoff
(National Research Council, 2004). Other
accretionary processes are also expected to
change:
• Future climate change will result in an
increase in the magnitude of coastal storms,
and their frequency will be at least as
common as at present, resulting in a net
increase in storm sedimentation in marshes in
this region.
• Tidal fluxes may alter, but the effect is
minimal in this region and the nature of the
effect on accretion is variable.
• Ice effects will diminish in importance as
climate warms.
• Nutrient delivery from coastal watersheds is
likely to increase as both climatic effects and
land use changes result in greater runoff.
• Oceanic sediment inputs to SF may increase
because of an increase in storms.
In this region, human activities could have a
greater direct effect on the viability of the
wetlands than climatic effects on accretionary
processes. Development pressures and land use
changes alter hydrology and nutrient delivery
and facilitate invasions, e.g., Phragmites. This
-------
[ 148 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
can alter plant community structure, which in
turn influences peat accumulation and accretion.
Figure 2.1.4 shows that FM along the tidal
sections of the South River and Raritan River
will survive 11 mm/yr of sea level rise and could
even expand because of their high productivity
and potential for peat accumulation. All the
remaining ES and SF marshes will become
marginal if sea level rise accelerates to 6 mm/yr
and will be lost under the high-range estimate of
11 mm/yr. For the ES marshes to survive the
high-range estimate, sediment input would need
to increase dramatically or plant communities
would need to change to those with greater
potential for peat accumulation. As noted above,
human influence may result in such shifts
whether or not high-range sea level rise estimates
hold true. For the SF marshes to survive 11
mm/yr of sea level rise, a massive increase in
sediment inputs would be required. This is not
foreseen at this time.
New Jersey Shore
This region encompasses the Atlantic shore of
New Jersey from Sandy Hook to Cape May.
Two tide gauges, Sandy Hook and Cape May,
can be used to document current sea level rise
trends for this shoreline. The current rate of sea
level rise for the area was determined to be 4
mm/yr, making the two future rates considered 6
mm/yr and 11 mm/yr. The geomorphic setting
varies along the shore (Figure 2.1.5). At the
northern end, the marshes are mostly ES with
some SF, while farther south along the barrier
island shoreline BB marshes, both back barrier
and lagoonal fill, and SF marshes are dominant.
There are ES and even FM within the tidal
portions of watersheds draining into the back
barrier lagoons.
The dominant accretionary processes are storm
sedimentation and peat accumulation. Future
climate change will result in an increase in the
magnitude of coastal storms due to increasing
sea-surface temperatures, and their frequency
will be at least as common as at present. Thus,
there will be a net increase in storm
sedimentation in marshes in this region. Vertical
accretion driven by peat accumulation is also
expected to increase in the future in response to
increased sea level. However, this increase will
occur only up to a threshold level. This threshold
is currently unknown for this region and there
are few published measurements of accretion in
this area (Table 2.1.1). Other accretionary
processes are also expected to change:
Tidal fluxes may shift to more ebb dominance as
tidal prism increases.
• Ice effects, although marginal now, will
diminish in importance as climate warms.
• Nutrient delivery from coastal watersheds is
likely to increase as both climatic effects and
land use changes result in greater runoff.
Fluvial sediment inputs will be equal to or
greater than present inputs and may influence
marsh accretion locally, especially in the lower
sections of the shore. Coastal wetlands along the
New Jersey shore are keeping pace with current
rates of sea level rise (Figure 2.1.6). However,
under midrange estimates they are all considered
marginal in terms of survival. The marshes close
to the Great Egg River and the Mullica River
may be more likely to survive because they have
localized sources of sediment from the rivers.
Similarly, under the high-range estimates for sea
level rise, most of the coastal marshes on the
Jersey shore are likely to be lost, except those
close to these localized sediment sources.
-------
[ SECTION 2.1
ix
ma
Atlantic
Ocean
Geomorphic Setting
| Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
{ Estuarine, fringe
Estuarine, meander
| Saline fringe
Tidal fresh forest
j Tidal fresh marsh
Figure 2.1.1. Geomorphic Settings for the New York - Long Island Region. Source: Titus et al.
Section 2.2).
PA f IniNiYj
NJ
V:Xmd 1
1
\
¦¦
\
J
is- - "' Long Island
Sound
,6
? m New York
i
r 7
Atlantic
Ocean
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
I
Current rate
Yes
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
Figure 2.1.2. Wetland Response Map for New York - Long Island Region. Source: Titus et al.
(Section 2.2).
-------
[ 150 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Geomorphic Setting
Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarlne marsh
Estuarlne, fringe
Estuarine, meander
Saline fringe
Tidal fresh forest
Tidal fresh marsh
Raritan
Bay
Figure 2.1.3. Geomorphic Settings for the New York - Long island Region. Source: Titus et al.
(Section 2.2).
-------
[ SECTION 2.1 151 ]
Raritan
Bay
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
n
n
Current rate
Yes
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
Figure 2.1.4. Wetland Response Map for Raritan Bay - New York Bay region. Source: Titus et al.
(Section 2.2).
-------
[ 152 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Atlantic
Ocean
Geomorphic Setting
Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
Saline fringe
Tidal fresh forest
Tidal fresh marsh
Figure 2.1.5. Geomorphic Settings for the New Jersey Shore Region. Source: Titus et al. (Section 2.2)
-------
[ SECTION 2.1 153 ]
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
I
No
Current rate
Yes
?
?
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
Atlantic
Ocean
Figure 2.1.6. Wetland Response Map for the New Jersey Shore Region. Source: Titus et al. (Section
2.2).
-------
[ 154 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Delaware Bay
This region encompasses the shores of Delaware
Bay and the tidal portions of rivers flowing into
the bay. Two tide gauges, Philadelphia and
Lewes, can be used to document current sea level
rise trends for this shoreline. The current rate of
sea level rise for the area was determined to be 3
mm/yr, making the two future rates considered 5
mm/yr and 10 mm/yr. The geomorphic setting
varies along the estuarine gradient (Figure 2.1.7).
FM exists along tributaries of the Delaware
River and in the upper tidal reaches of the
Maurice River draining into the bay. Upper parts
of Delaware Bay are bordered by ES marshes,
with SF marshes toward the ocean.
The dominant accretionary processes vary
according to geomorphic setting. Peat
accumulation is important to all wetlands in this
area. Vertical accretion driven by peat
accumulation is expected to increase in the future
in response to increased sea level. However, in
most of these marshes this increase will occur
only up to a threshold level. The exception is the
FM area where, as long as marshes stay fresh,
peat accumulation should allow marshes to
accrete and even expand in the face of high range
sea level rise. However, if these salinities
increase with sea level rise, S042" reduction will
increase, and that could lead to increased rates of
decomposition and offset the rise due to peat
accumulation. The threshold level for ES and SF
marshes is currently unknown for this region,
although lower salinity ES marshes will be less
subject to the threshold and more similar to FM.
Fluvial sediment inputs are important to FM and
are expected to increase in this area as climate
changes cause precipitation events to be more
intense and periodic, resulting in flashy runoff.
Future climate change will result in an increase
in the magnitude of coastal storms due to
increasing sea-surface temperatures, and their
frequency will be at least as common as at
present. Storm sedimentation is important to ES
marshes in this region and is expected to increase
in the future. The SF marshes in the lower bay,
because of the high fetch and their exposure to
oceanic influence, also receive sediment from the
Atlantic. Greater storminess will increase the
availability of these sediments, benefiting the SF
marshes. Other accretionary processes are also
expected to change:
• Tidal fluxes may alter, but the effect is
minimal in this region.
• Ice effects are of minimal importance here
and will diminish in importance as climate
warms.
• Nutrient delivery from coastal watersheds is
likely to increase as both climatic effects and
land use changes result in greater runoff.
Figure 2.1.8 shows that all coastal wetlands in
the Delaware Bay region are keeping pace with
current rates of sea level rise. The FM marshes
along the Delaware and Maurice rivers will
survive 10 mm/yr of sea level rise, the high-
range estimate, and could even expand because
of their high productivity and potential for peat
accumulation. However, under midrange
estimates (5 mm/yr for this region), ES and SF
marshes are all considered marginal in terms of
survival and are expected to be lost under the
high-range estimate of sea level rise.
Sustainability of these marshes in the future will
require either a substantial increase in sediment
inputs or a change in plant community type to
one with a greater potential for peat
accumulation. Any such change in plant
communities might also change the habitat value
of these extensive Delaware Bay marshes. The
role of storm sedimentation in future marsh
accretion will be dependent to some extent on
aspect. Marshes in the New Jersey shore receive
less storm-related mineral sediment because
nor'easters generally blow water out of the
marshes in winter (toward the Delaware shore).
These marshes may also be more remote from
sediments introduced by period ocean waves
from the southeast in summer.
-------
[ SECTION 2.1 155 ]
Maryland/Virginia Shore
This region encompasses the Atlantic shore of
Maryland and Virginia from Cape Henlopen to
Cape Charles. The current rate of sea level rise
for this area is best assessed using an average of
regional gauges rather than data from a single
location. The current rate of sea level rise for the
area was determined to be 3 mm/yr, making the
two future rates considered 5 mm/yr and 10
mm/yr. The geomorphic setting varies from
north to south along this shore (Figure 2.1.9).
Along the Delaware shoreline, BB marshes front
small lagoons such as Rehoboth Bay and Indian
River Bay, with SF on the upland margin. BB
lagoonal fill becomes more important toward the
southern end of Assateague Island. Farther south,
BB flood tide delta marshes are interspersed with
BB marshes along the barrier shoreline, with
extensive BB lagoonal fill in Hog Island Bay and
South Bay, and SF marshes along the upland
margin.
The dominant accretionary processes are storm
sedimentation and overwash from barrier
beaches. Future climate change will result in an
increase in the magnitude of coastal storms due
to increasing sea-surface temperatures, and their
frequency will be at least as common as at
present. Thus, there will be a net increase in
storm sedimentation in marshes in this region.
Vertical accretion driven by peat accumulation is
not as important in this area as in other marshes.
Many of the marshes occur on pre-existing
topographic highs that have been gradually
flooding by rising seas. Tidal fluxes are also of
minimal importance, except on the flood tide
deltas, with local resuspension being the main
source of sediment. Other accretionary processes
are also expected to change:
• Nutrient delivery from coastal watersheds is
likely to increase as both climatic effects and
land use changes result in greater runoff.
• Fluvial sediment inputs will be equal to or
greater than present inputs and may increase
marsh accretion locally. However,
watersheds draining into this region are
generally small.
Figure 2.1.10 shows the accretion scenarios for
this region. All marshes are keeping pace with
current rates of sea level rise. However, should
sea level rise rates increase to 5 mm/yr, the
midrange estimate, they are considered to be
marginal. Their survival is likely to depend on
the frequency of storm impacts to supply
sediments. Under the high range estimate of 10
mm/yr, these marshes will be lost because they
will not be able to maintain their elevation.
-------
[ 156 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Geomorphic Setting
Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
Saline fringe
Tidal fresh forest
Tidal fresh marsh
Delaware
Bay
Figure 2.1.7. Geomorphic Settings for the Delaware Bay Region. Source: Titus et al. (Section 2.2).
-------
[ SECTION 2.1 157 ]
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
¦
Current rate
Yes
?
?
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
No
? - Wetlands would be marginal Yes? = Wetland would be marginal or lost
A
^7
Pennsylvania r* w
New Jers
vr.-'M
;4^,r> 1
Vf
Figure 2.1.8. Wetland Response Map for the Delaware Bay Region. Source: Titus et al. (Section 2.2).
-------
[ 158 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Atlantic
Ocean
Virginia
Geomorphic Setting
Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
Saline fringe
Tidal fresh forest
Tidal fresh marsh
Chesapeake
Bay
Figure 2.1.9. Geomorphic Settings for the Maryland-Virginia Shore Region. Source: Titus et al.
(Section 2.2).
-------
[ SECTION 2.1 159 ]
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
¦
Current rate
Yes
?
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
Figure 2.1.10. Wetland Response Map for the Maryland/Virginia Shore Region. Source: Titus et al.
(Section 2.2).
-------
[ 160 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Chesapeake Bay
This region encompasses the entire Chesapeake
Bay, including the tidal portions of rivers
draining into the Bay, with the exception of the
Lower Maryland Eastern Shore region. Because
of the great area involved, current sea level rise
rates should be determined for the upper part of
the Bay using the Baltimore gauge. The current
rate of sea level rise in this area was determined
to be 3 mm/yr, making the two future rates
considered 5 mm/yr and 10 mm/yr. For the area
south of the Potomac, local knowledge indicates
that these rates should be higher: 4 mm/yr for
current, 6 mm/yr for midrange, and 11 mm/yr for
high-range estimates.
Chesapeake Bay coastal wetlands occur in a
variety of geomorphic settings (Figure 2.1.11).
There is some FF within this region, most
notably near Adelina on the Patuxent estuary.
Throughout the Maryland portion of the
Chesapeake Bay region, FM occurs in the tidal
rivers, with ES marshes bordering the open bay.
On the eastern shore of Virginia from Pocomoke
Sound south, SF marshes occur, in some areas
grading into ES toward the upland. On the
western shore of Virginia, the lower reaches of
the Rappahannock, the York and the James
rivers are bordered by ES fringe marshes with
FM farther from the Bay itself. SF marshes also
occur on the margins of the Bay south of the
Rappahannock River.
The dominant accretionary processes vary
according to geomorphic setting. Peat
accumulation is important to all wetlands in this
area. Vertical accretion driven by peat
accumulation is expected to increase in the future
in response to increased sea level. However, in
most of these marshes, this increase will occur
only up to a threshold level. The exception is the
FM area, where peat accumulation should allow
marshes to accrete and even expand in the face
of high-range sea level rise. The threshold level
for ES and SF marshes is currently unknown for
this region, although it is expected that the ES
marshes may not even reach the threshold here.
Fluvial sediment inputs are important to FM and
are expected to increase in this area as climate
changes cause precipitation events to be more
intense and periodic, resulting in flashy runoff.
Storm-driven sedimentation is important for ES
marshes in this region. Future climate change
will result in an increase in the magnitude of
coastal storms due to increasing sea-surface
temperatures, and their frequency will be at least
as common as at present. Storm sedimentation is
therefore expected to increase in the future. The
SF marshes in the lower Bay may receive
increased sediment in the future from the ocean.
Greater storminess will increase the availability
of these sediments. Other accretionary processes
are also expected to change:
• Tidal fluxes may alter, but the effect is
minimal in this region. In ES an increase in
tidal prism may result in more export from
already stressed marshes.
• Ice effects are of minimal importance here
and will diminish in importance as climate
warms.
• Nutrient delivery from coastal watersheds are
likely to increase as both climatic effects and
land use changes result in greater runoff.
• Herbivory, which is locally important here, is
expected to decrease or remain the same
because of management actions.
Figure 2.1.12 shows the accretion scenarios for
the Chesapeake Bay region (note that the Lower
Maryland Eastern Shore region is discussed
separately below). FF and FM marshes are
keeping pace with current rates of sea level rise,
largely through peat accumulation, and will
continue to accrete at rates at least sufficient to
survive the high-range estimates for Chesapeake
Bay region. There are some coastal wetlands,
however, that cannot keep pace with current
rates and are being lost. Specific areas are at Hog
Island and Plum Tree Island National Wildlife
Refuge on the western shore, and the Tobacco
islands and Hacksneck areas on the eastern
shore. These SF marshes are not sustainable and
will certainly be lost under even midrange
estimates of future sea level rise. The ES
marshes bordering the bay and its tributaries are
all considered to be keeping pace with current
sea level rise rates (3-4 mm/yr in the region) but
are marginal under midrange estimates.
-------
[ SECTION 2.1 161 ]
Consequently, they will be lost if high-range
estimates of future sea level rise are realized.
Lower Maryland Eastern Shore
This region encompasses the tidal wetlands on
the eastern shore of Maryland and Virginia
between the Chester River and the Pocomoke
River. Most of this region lies in the upper part
of Chesapeake Bay, and thus the Baltimore tide
gauge is most appropriate. The current rate of sea
level rise for the area was determined to be 3
mm/yr, making the two future rates considered 5
mm/yr and 10 mm/yr. The very southern part of
this region lies south of the Potomac, and thus,
as for the Chesapeake Bay region, local
knowledge indicates that rates for the southern
portion should be higher: 4 mm/yr for current, 6
mm/yr for midrange, and 11 mm/yr for high
range estimates.
Coastal wetlands on the Lower Maryland Eastern
Shore occur in a variety of geomorphic settings
(Figure 2.1.13). There is some FF in the vicinity
of Salisbury and Wellington where some cypress
occurs within FM areas, and near Wye Mills
farther north. FM occurs in the tidal rivers of the
eastern shore, including the Choptank, Naticoke,
and Pocomoke, with ES marshes bordering the
open bay and on islands within the Bay. Some
SF marshes occur on the north side of Pocomoke
Bay.
The dominant accretionary processes are similar
to those found in similar geomorphic settings in
other parts of Chesapeake Bay. Peat
accumulation is important to all wetlands in this
area and is expected to increase in the future. In
most of these marshes this increase will occur
only up to a threshold level. The exception is the
FM area, where peat accumulation should allow
marshes to accrete and even expand in the face
of high-range sea level rise. Fluvial sediment
inputs are important to FM and are expected to
increase in this area as climate changes cause
precipitation events to be more intense and
periodic, resulting in flashy runoff. Storm-driven
sedimentation is important for ES marshes in this
region and is expected to increase in the future.
The SF marshes in this region are distant from
direct oceanic inputs and will be unlikely to
receive additional sediments in the future from
this source. Changes in tidal flux may be
important in exporting material from already
stressed marshes. Herbivory, which is locally
important here, is expected to decrease or remain
the same because of management actions.
Figure 2.1.14 shows the accretion scenarios for
this region. One of the reasons this area has been
singled out from the other coastal wetlands in
Chesapeake Bay is the extreme rate of wetland
loss already being experienced in the area. Large
areas of the ES marshes are apparently not
currently keeping pace with sea level rise and are
expected to be lost even without acceleration in
sea level rise. These include the Blackwater
National Wildlife Refuge marshes, Bloodsworth
Island and South Marsh Island, as well as Deal
Island and the Grays Island Marsh area east of
Fishing Bay. The remainder of the ES marshes in
the region are considered marginal even under
current sea level rise conditions and they are
expected to be lost if even the midrange estimate
of future rise is realized. Accretion scenarios are
most optimistic for the FM areas of the tidal
rivers, where organic accumulation processes
should allow marshes to keep pace with even
high-range estimates of sea level rise.
Virginia Beach/Currituck Sound
This region encompasses the Virginia tidal
marshes of Back Bay, including Back Bay
National Wildlife Refuge and Northwest and
North Landing rivers. These embayments and
estuaries are the northernmost extent of
Currituck Sound as it extends into Virginia.
There are few tide gauges that reflect the setting
of this area directly. The most appropriate tide
gauges are Sewells' Point in Virginia and
Beaufort, North Carolina. The current rate of sea
level rise for the area based on these gauges was
determined to be 4 mm/yr, making the two future
rates considered 6 mm/yr and 11 mm/yr. The
geomorphic setting for these marshes includes
FF and FM mix along the Northwest and North
Landing rivers, with ES and in Back Bay and BB
marshes immediately behind the barrier shoreline
(Figure 2.1.15).
-------
[ 162 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
The dominant accretionary processes are peat
accumulation within FF and FM, and storm
sedimentation inputs for the marshes
surrounding Back Bay. Vertical accretion driven
by peat accumulation is expected to increase in
the future in response to increased sea level, and
should be adequate to allow FF and FM wetlands
to accrete and even expand in the face of high-
range sea level rise. Storm-driven sedimentation
is important for ES and BB marshes in this
region. Future climate change will result in an
increase in the magnitude of coastal storms due
to increasing sea-surface temperatures, and their
frequency will be at least as common as at
present. Storm sedimentation is therefore
expected to increase in the future. Other
accretionary processes are also expected to
change:
• Tidal fluxes may alter, but the effect is
minimal in this region and the nature of the
effect on accretion is negligible.
• Nutrient delivery from coastal watersheds is
likely to increase as both climatic effects and
land use changes result in greater runoff.
Figure 2.1.16 shows that none of the wetlands in
the area will survive 11 mm/yr of sea level rise.
Although the FF and FM marshes in other areas
have been considered more resilient, in this area
tidal fluctuations are so small that an increase of
2 mm/yr in sea level threatens to introduce both
salinity and a changed hydroperiod to the fresh
parts of the estuary. These wetlands are
considered marginal today because they are
stressed by existing sea level rise conditions. All
the remaining ES and BB marshes will become
marginal if sea level rise accelerates to 6 mm/yr
and will be lost under the high-range estimate of
11 mm/yr. For the ES and BB marshes to
survive, the midrange estimate sediment input
from storms would need to increase, which is
very dependent on actual storm impacts,
frequency, and tracks.
-------
[ SECTION 2.1 163 ]
Atlantic
Ocean
Geomorphic Setting
| Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
| Saline fringe
Tidal fresh forest
j Tidal fresh marsh
17
Figure 2.1.11. Geomorphic Settings for the Chesapeake Bay Region. Source: Titus et al. (Section 2.2).
-------
[ 164 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
¦
Current rate
Yes
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
\/
Figure 2.1.12. Wetland Response Map for the Chesapeake Bay Region. Note that the Lower Maryland
Eastern Shore Region is considered separately. Source: Titus et al. (Section 2.2).
-------
[ SECTION 2.1 165 ]
Geomorphic Setting
Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
Saline fringe
Tidal fresh forest
Tidal fresh marsh
Chesapeake
Bay
Atlantic
Ocean
Figure 2.1.13. Geomorphic Settings for the Lower Maryland Eastern Shore Region. Source: Titus et al.
(Section 2.2).
-------
[ 166 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
. .< <5
A *
* • fj{3Ai.4
Chesapeake
Bay
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
~
Current rate
Yes
?
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
Atlantic
Ocean
Figure 2.1.14. Wetland Response Map for the Lower Maryland Eastern Shore. Source: Titus et al.
(Section 2.2).
-------
[ SECTION 2.1 167 ]
P%{s
, f -St 7*55*--
I v^s
Geomorphic Setting
| Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, tagoonal fill
Estuarine marsh
| Estuarine, fringe
Estuarine, meander
| Saline fringe
Tidal fresh forest
I Tidal fresh marsh
i Atlan
Ocean
Figure 2.1.15. Geomorphic Settings for the Virginia Beach/Currituck Sound Region. Source: Titus et
al. (Section 2.2).
-------
[ 168 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
Current rate
Yes
?
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
TT
Atlantic
Ocean
Figure 2.1.16. Wetland Response Map for the Virginia Beach/Currituck Sound Region. Source: Titus
et al. (Section 2.2).
-------
2.1.5. Summary and Conclusions
This study has shown that the prognosis for the
coastal wetlands of the Mid-Atlantic under
current sea level rise is for the most part good
and that as rates accelerate toward midrange
estimates, a 2 mm/yr increase, their survival
depends on optimal hydrology and sediment
supply conditions. There are exceptions to this
assessment at both local and regional scales and
some variation with geomorphic setting.
For the entire area, tidal fresh forests and
marshes are considered the most sustainable. As
long as salinities do not increase, these systems
build vertically, primarily through organic
accumulation, and are less dependent on mineral
sediment supply. This bodes well for migration
of tidal wetlands upstream along tidal rivers as
sea level rises.
Those marshes that are currently being lost either
locally within Jamaica Bay or at a larger scale on
the Lower Maryland Eastern Shore are unlikely
to be rebuilt or replaced by natural processes as
sea level continues to rise. The Chesapeake
wetlands are for the most part transgressive—
formed as sea level flooded former uplands.
Along the shores of the open Bay, such
migration is limited by physical barriers or land
use preferences, and any areal increase in fresh
marshes along the tidal rivers as sea level rises
will be limited. In back-barrier island marshes,
transgression is impossible, and as such, island
marshes may fare poorly. In Jamaica Bay, the
marshes are built on lagoonal fill and relict flood
tide delta deposits, but development of
Rockaway Beach and dredging of the inlet have
essentially halted these sedimentary processes;
these marshes also are unlikely to be replaced by
natural processes (Gornitz et al., 2001).
Perhaps of more concern are marshes considered
marginal under current conditions, which are not
expected to survive an acceleration of sea level
rise. These marshes are concentrated in the
Lower Maryland Eastern Shore region, and it is
possible that restoration measures could be taken
to improve their vigor or increase their elevation
at least locally. Should they be lost, as predicted
here, natural processes are not in place to rebuild
them, and they could be replaced only by
allowing major conversion of adjacent uplands to
tidal wetlands. Even then, given the highly
altered nature of this system, active restoration of
hydrology and sediment supply pathways would
be necessary to ensure their survival under even
midrange estimates of sea level rise.
Very few brackish or salt marshes in the area can
survive sea level rise rates in excess of 10
mm/yr. Where sediment supply from inlets,
overwash, or rivers is substantial, local areas of
marsh on Long Island could survive. This may
be the case in some other back barrier marshes,
but it will be very dependent on local storm-
driven sediment supply.
This report has evaluated the fate of coastal
wetlands according to three sea level rise
estimates. The large difference, 5 mm/yr,
between the midrange estimate and the high-
range estimate means the study considered how
marshes would respond to rates of 6 mm/yr and
11 mm/yr but not rates in between. Few studies
specifically address the maximum rates at which
marsh vertical accretion can occur. Morris et al.
(2002) used modeling and field data to estimate
that under high sediment supply conditions,
Spartinci altemiflora marshes in the Southeast
could survive sea level rise rates as high as 12.5
mm/yr, and Bricker-Urso et al. (1989) posited a
maximum rate of 14-16 mm/yr for salt marshes
in Rhode Island. However, no studies have
addressed the thresholds for organic
accumulation in the marshes considered here.
Determining the fate of coastal wetlands at rates
of sea level rise between the mid and high
estimates used here requires further elucidation
of variations in this maximum rate regionally
and among vegetative communities.
-------
Acknowledg merits
The contributors to this report acknowledge the assistance of Russ Jones and his team at Stratus
Consulting for preparing the maps shown in this report from our workshop products. Laura Dancer
assisted with expert panel logistics and report preparation. Phillipe Hensel helped us identify some
of the studies outlined in Table 2.1.2, and we wish to especially thank the researchers who provided
unpublished or prepublication data. Don Cahoon and staff of the Patuxent Wildlife Research Center
hosted the panel workshop at their facilities.
-------
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vegetation and soil formation in a rapidly submerging coastal marsh. Marine Ecology
Progress Series 96: 269-279.
Oertel, G.F., G.T.F. Wong and J.D. Conway. 1989. Sediment accumulation at a fringe marsh during
transgression, Oyster, Virginia. Estuaries 12(1): 18-26.
Orson, R.A., W. Panageotou, and S.P. Leatherman. 1985. Response of tidal salt marshes to rising sea
levels along the U.S. and Atlantic and Gulf states. Journal of Coastal Research 1(1): 29-38.
Orson, R.A., R.L. Simpson, and R.E. Good. 1990. Rates of sediment accumulation in a tidal
freshwater marsh. Journal of Sedimentary Petrology 60(6): 859-869.
Pasternack, G.B. and G. S. Brush. 1998. Sedimentation cycles in a river-mouth tidal freshwater
marsh. Estuaries 21: 407-415.
Pethick, J. 1981. Long-term accretion rates on tidal salt marshes. Journal of Sedimentary Petrology
51:571-577.
Pizzuto, J.E. and E.W. Rogers. 1992. The Holocene history and stratigraphy of palustrine and
estuarine wetland deposits on central Delaware. Journal of Coastal Research 8(4): 854-867.
Reed, D.J. 1989. Patterns of sediment deposition to subsiding coastal salt marshes, Terrebonne Bay,
Louisiana: The role of winter storms. Estuaries 12: 222-227.
Reed, D.J. and D.R. Cahoon. 1993. Marsh submergence vs. marsh accretion: interpreting accretion
deficit data in coastal Louisiana. Pages 243-257 in Coastal Zone '93 Proceedings, 8th
Symposium on Coastal and Ocean Management, 19-23 July, 1993, New Orleans, Louisiana.
Richard, G.A. 1978. Seasonal and environmental variations in sediment accretion in a Long Island
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Rooth, J.E. and J.C. Stevenson. 2000. Sediment deposition patterns in Phragmites australis
communities: Implications of coastal areas threatened by rising sea- level. Wetland Ecology
and Management 8:173-183.
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Rooth, J.E., J.C. Stevenson, and J.C. Cornwell 2003. Increased sediment accretion rates following
evasion by Phragmites australis: The role of litter. Estuaries 26(2B): 475-483.
Rybczyk, J.M. and D.R. Cahoon. 2002. Estimating the potential for submergence for two wetlands
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Harwell, R. W. Howarth, C. Mason, D. J. Reed, T. C. Royer, A. H. Sallenger, and J. G. Titus.
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Stevenson, J.C., L.G. Ward, and M.S. Kearney. 1988. Sediment transport and trapping in marsh
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2.2. Maps that Depict Site-Specific Scenarios for
Wetland Accretion as Sea Level Rises along the
Mid-Atlantic Coast
Authors: James G. Titus, U.S. Environmental Protection Agency
Russ Jones, Stratus Consulting Inc.
Richard Streeter, Stratus Consulting Inc.
This section should be cited as:
Titus, J.G., R. Jones, and R. Streeter. 2008. Maps that Depict Site-Specific Scenarios for
Wetland Accretion as Sea Level Rises along the Mid-Atlantic Coast. Section 2.2 in:
Background Documents Supporting Climate Change Science Program Synthesis and
Assessment Product 4.1, J.G. Titus and E.M. Strange (eds.). EPA 430R07004. U.S. EPA,
Washington, DC.
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[ 176 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Abstract
This paper develops maps and a data set
depicting a set of site-specific assumptions for
wetland vertical accretion developed by a panel
of wetland scientists. The panel had drawn
polygons on USGS 1:250,000 scale topographic
maps. For each polygon, for each of three sea
level rise scenarios, the panel indicated whether
tidal wetlands within the polygon would be lost,
keep pace, or be marginal. This paper describes
how we converted the hard-copy polygons into a
GIS database and created a set of maps to
concisely depict the panel's findings.
2.2.1. Background
In Section 2.1, Reed et al.1 explain the basis for
an expert panel assessment of the ability of
coastal wetlands to keep pace with rising sea
level along the mid-Atlantic Coast from the
south shore of Long Island to the Virginia/North
Carolina border. That assessment was a part of
EPA's effort to assess the possible vulnerability
of tidal wetlands to rising sea level, which also
depends on coastal topography2 and coastal
development.
This paper describes our efforts to create a GIS
data layer and maps to depict the panel's
assessment. The panel produced a set of marked-
up hard copy USGS 1:250,000 scale maps and a
:Reed, D.J., D.A. Bishara, D.R. Cahoon, J. Donnelly, M.
Kearney, Alex Kolker, L.L. Leonard, R. Orson, and J.C.
Stevenson. 2008. Site-Specific Scenarios for Wetlands
Accretion as Sea Level Rises in the Mid-Atlantic Region.
Supporting Document for CCSP 4.1, Question 3. New
Orleans, LA: Department of Earth and Enviromnental
Sciences University of New Orleans.
2In Chapter 1, Titus and Wang develop a data set and maps
expressing coastal elevations relative to spring high water,
which is approximately the upper boundary of tidal
wetlands. See Titus and Wang, 2008, Maps of Lands Close
to Sea Level along the Middle Atlantic Coast of the United
States: An Elevation Data Set to Use While Waiting for
LIDAR, in Background Documents Supporting Climate
Change Science Program Synthesis and Assessment Product
4.1: Coastal Elevations and Sensitivity to Sea Level Rise,
EPA 430R07004, Washington. DC: U.S. EPA.
set of spreadsheets. We used the hard copy maps
to define our polygon boundaries and the
spreadsheets to provide descriptions about those
polygons (i.e., attributes).4
The panel drew polygons on the hard copy maps
to approximately identify the areas associated
with five primary geomorphic settings, with
several subsettings. The USGS 1:250,000 scale
topographic maps show roughly where wetlands
exist; but they do not delineate the actual
wetlands. Therefore, we construed each polygon
as representing the panel's intent to identify an
area within which all tidal wetlands could be
associated with one of the following geomorphic
settings or subsettings:
1. Tidal Fresh Forests
2. Tidal Fresh Marsh
3. Estuarine/Brackish Channelized Marshes
a. Meander
b. Fringing
c. Island
4. Back Barrier Lagoon Marsh
a. Back barrier/Other
b. Active flood tide delta
c. Lagoonal fill
5. Saline Marsh Fringe
Each polygon on the maps had an index number.
The associated spreadsheets provided:
• Polygon index number
• Region (as described in the panel report)
• Two columns for geomorphic setting and
sub setting,
• Three columns for the panel's prognosis
for wetland accretion under three
alternative sea level rise scenarios
• Place name (optional)
• Special explanation (if appropriate).
The three sea level rise scenarios were current
rate, current rate + 2 mm/yr, and current rate + 7
mm/yr. For each of these three scenarios the
spreadsheet provided a prognosis for wetland
accretion for each polygon. In most cases, the
prognosis was one of three possibilities: keeping
4In a GIS polygon layer, an attribute table associates
information with each polygon.
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[ SECTION 2.2 177 ]
pace, marginal, and loss (see Section 2.1, Reed et
al. for description). In a few cases, however, the
panel's original assessment was "marginal/loss"
for a particular sea level rise scenario.5
2.2.2. Conversion of the Panel's
Output to a GIS Dataset
Our final data set provides two layers:
• "Raw" consists of the polygons created by
the panel (and the associated attributes),
which identify the geomorphic setting.
• "Wetlands" is a coastal wetlands data set,
with attributes that identify the geomorphic
settings and wetland accretion potential as
defined by the panel.
The Raw Data
Our objective was to convert the hand renderings
into a digital data set suitable for use in a GIS.
The polygons provided by the panel included
tidal wetlands, nontidal wetlands, dry land, and
open water; but the information developed by the
panel applies only to the tidal wetlands within
the polygon. We also inspected the results of our
digitizing to identify and remedy those cases
where a literal digital conversion of what the
panel drew was inconsistent with the panel's
intent. For example, the polygon boundaries did
not include all of the tidal wetlands in some
areas, because the USGS 1:250,000 scale
topographic maps do not show all wetlands or
indicate the head-of-tide (above which wetlands
are nontidal).
The first step toward creating a data set was to
create a tracing of the polygons according to a
procedure developed by Russ Jones. The key
aspects were to faithfully trace the panel
polygons and the registration marks from the
USGS maps. Dana Bishara of the University of
New Orleans overlayed Mylar sheets on top of
the 1:250,000 USGS maps and manually traced
the polygons and registration marks, and sent
them to Jones.
The second step was to digitize the polygons.
Jones provided the Mylars to Digital Data
Services, Inc. (Lakewood, Colorado), who
scanned them to a digital format in color at 300
dots per inch in Tagged Image File Format (tif).
Richard Streeter digitized the polygons into a
GIS using raster-to-vector conversion software.6
See Figure 2.2.1.
The third step was to overlay the polygons with a
wetlands data set. Jones and Streeter created
quad-specific maps in a GIS by overlaying the
polygons on top of the EPA coastal wetlands
data set (Chapter 1, Titus and Wang, see note 2).
Figure 2.2.2 shows the initial "raw" product
from this overlay, for the Salisbury (Maryland)
quadrangle.
5These cases were all either along the South Shore of Long
Island or in the Virginia Beach/Chesapeake area.
6ESRI, 2005, ArcScan software, v. 9.1, Redlands, CA:
Environmental Systems Research Institute.
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[ 178 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Figure 2.2.1. Polygons Created by Wetland Accretion Panel Assessment: Salisbury Quadrangle. The
wetland accretion panel drew polygons on 1:250,000 USGS quads. Panel staff then traced the
polygons onto Mylar. The black lines define subregions; the other colored lines define polygons
representing wetlands of a given geomorphic setting.
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[ SECTION 2.2 179 ]
Figure 2.2.2. Overlay of the Polygons from Wetland Accretion Panel with a Wetlands Data Set:
Salisbury Quadrangle. Each of the shaded polygons has an index number or letter; wetlands outside
the shaded polygons were unassigned and had to be corrected. The light red lines that are not the
boundary of a shaded polygon delineate the subregional boundaries. Note that that the shaded
polygons do not include ail of the tidal wetlands along Chincoteague and Indian River bays, nor the
upper portions of the Choptank, Nanticoke, and Pocomoke rivers.
The fourth step was quality control of the
polygons created by the panel. Figure 2.2.2
shows some of the issues that we addressed in
this step. In many cases, tidal wetlands7 lie
outside of the geomorphic regions defined by the
polygons, and assignments of geomorphic
regions did not match local conditions (e.g.,
active flood tide deltas were not adjacent to
inlets). In some cases, the tidal wetlands
extended farther inland than the polygons. See,
for example, the tidal wetlands that are not
included in a shaded polygon to the west (inland)
of polygon #3 along Delaware Bay; the extensive
7Titus and Wang (see note 2) generated a wetlands data set
from a combination of National Wetlands Inventory
wetlands and state wetlands data sets.
tidal wetlands along Rehoboth Bay (i.e., the bay
between polygons #6 and #7), and the tidal
wetlands along the upper Pocomoke River (i.e.,
the river that runs through polygon #C). In other
cases, wetlands extend farther into the coastal
lagoons than the polygons drawn by the panel
indicated (e.g., the wetlands along polygons #9
and #10). In some cases, the original polygons
omitted wetland areas, particularly in the upper
reaches of estuaries; so we had no information
on geomorphic setting or wetland accretion
potential for wetlands in those areas (see Figures
2.2.2 and 2.2.3).
In general, the panel's polygon boundaries
needed correction for several reasons:
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[ 180 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
(a) Maps using a coarse 1:250,000 scale
routinely show "scale mismatch" when overlaid
with data created at a finer resolution.
(b) The panel's polygon boundaries often
omitted large areas of wetlands, because the
USGS 1:250,000 maps do not show all wetlands.
(c) In some cases, the polygon boundaries did
not track the landforms originally intended (e.g.,
the polygon around an inlet on the 1:250,000
scale map covering open water and missing the
wetlands). This occurred primarily because the
polygons that the panel had drawn were in many
cases drawn to be "indicative" rather than
precise; e.g., on the 1:250,000 map, the polygons
boundaries as drawn sometimes differed from
the actual boundary by approximately 1 cm.
(d) The panel did not have a watershed map, and
in some cases the boundaries that they drew
unintentionally crossed watershed boundaries or
split a boundary. Many of these errors were
apparent with the wetlands overlay.
We brought these cases to the attention of Reed
and Bishara, who used our overlay to hand-edit
the polygon boundaries to more closely follow
the landforms and thus reflect the original intent
of the panel. Streeter digitized the changes into
the GIS. We then examined the maps a final time
and made a small number of additional
corrections. For example, in Figure 2.2.3, some
tidal wetlands were not part of any "polygon" in
the original panel output. The hand-edits
assigned all of those wetlands to the same
categories as the adjacent estuarine wetlands.
Along the Christina River, this left us with
estuarine wetlands upstream from freshwater
wetlands; so we readjusted polygon 5 to include
the upper portion of the tidal river. The net effect
of these changes was to ensure that all tidal
wetlands would be included in one of the shaded
polygons, and associated with the correct
landform and assigned region.
Wetlands Data Set
Our fifth step was to convert the raw data into a
wetlands data set. This step involved both data
processing and some cartography. Our data
processing step involved importing the
spreadsheets of attributes provided by Reed into
the GIS and joining to the polygon layer via the
index number that was common to both files.
Finally, we transferred the attributes in the panel
polygons to the EPA coastal wetlands data
generated by Titus and Wang via a simple
overlay function within the GIS. The final output
of this fifth step is a polygon wetland data set
with attributed defining geomorphic setting,
accretion potential, and subregion. Figure 2.2.4
is an example of the resulting map.
2.2.3 Creating Maps from the Data
The cartographic step involved devising a
reasonable way to portray the results of the panel
assessment. The three main issues we considered
were readability of small polygons, map colors,
and the map legend.
Readability of Small Polygons
The purpose of the map is to show where
wetlands are likely (or unlikely) to keep pace
with sea level rise. We decided early on to use
wetlands data rather than regional boundaries,
because the area and location of wetlands is an
important consideration. In places where the
wetlands are a narrow fringe or widely dispersed
islands, they are likely to be too small to be seen
on a statewide map drawn to scale—not to
mention a map of the entire mid-Atlantic. We
looked at test maps drawn to scale, and the
freshwater tidal wetlands along the Potomac and
Delaware rivers were particularly hard to see.
Therefore, in printing these maps, we set the line
widths to be scale-independent, to accentuate
small areas. The net effect is that every tidal
wetland polygon displays on our maps (unless
overlaid with another wetland polygon).
-------
[ SECTION 2.2 181 ]
^ Polygon Boundary: Saline
Polygon Boundary: Estuarine
| Polygon Boundary: Fresh
25QK Map Boundary
'¦ • Region Boundary
Open Water
Nontidal Wetlands
¦ Tidal Wetlands
Figure 2.2.3. Overlay of the Polygons from Wetland Accretion Panel and Wetlands Data Set: Wilmington
Quadrangle. The fresh/saline interface in the Delaware River is generally viewed as located near the
Delaware/Pennsylvania border. But freshwater wetlands extend farther downstream, according to the
panel. Polygon 5 represents the freshwater tidal marshes of the Delaware River watershed; the panel
viewed the rest of the wetlands in the Delaware River watershed as estuarine marsh. Although the mouth
of the Christina River into the Delaware River (southwest end of polygon 5) is in the freshwater marsh,
the upstream portions of the river are shown as being estuarine marsh. We treated this as unintentional
and altered the boundaries to show this entire river as freshwater marsh. Note also that that polygons
denoting wetland zonation do not include all of the tidal wetlands on the Delaware side of the Delaware
River and Bay.
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[ 182 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
13
New
Jersey
, Shore
Delaware Bay
Lower (
Maryland '
Eastern Shore
Maryland/Virginia
Shore
Geomorphic Setting
| Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuanine marsh
| Estuarine, fringe
| Saline fringe
Tidal fresh forest
| Tidal fresh marsh
Other Tidal Wetlands
Non-Tidal Wetlands
] Map Boundary
Region Boundary
Figure 2.2.4, Wetland data displayed based on attributes provided by the panel for geomorphic
setting. By this point, polygon boundaries had been revised to include most tidal wetlands. Compare
with Figure 2.2.2. A few revisions were still needed, such as along Indian River Bay, where some tidal
wetlands were still outside the polygon boundaries.
Expectation
Loss even at current rates:
Marginal today, loss at +2
rn/yr:
Keeping pace today, marginal
at 2 mm/yr, loss at 7 m/yr
Keep pace +2 mm/yr, loss at
+7 mm/yr
Keeping with +2 mm/yr,
marginal at +7 mm/yr
Keeping pace at +7 mm/yr
Color Reason for Color
Blue
Red
Brown
Yellow
Brown
Light
green
Bold
green
Because it is becoming water anyway
The standard color for a warning
A common color for environmental risk
A compromise between brown and green
Wetlands likely to survive, stay green
Wetlands very likely to survive (remain
green)
-------
[ SECTION 2.2 183 ]
"> Lower
Loss even with today's trend
Marginal today, loss with current +2mnVyr
Marginal today, marginal or
loss with current +2 mm/yr
Keep pace today, marginal wilh current
+2mnVyr, loss with current +7mrrVyr
Keep pace with current +2mnVyr,
loss with current +7 mm/yr
Keep pace with current +2 mnVyr,
marginal/loss with current +7mm/yr
Keep pace with current +2mnVyr,
marginal with current +7mnVyr
Keep pace with current *7mm/yr
Unassigned Tidal Wetlands
Non-Tidal Wetlands
250K Map Boundary
Region Boundary
Figure 2.2.5. Wetland Accretion potential for polygons in the Salisbury quad. At this point, the polygons
still needed revision around Indian River Bay.
Map Colors
The panel provided one of five accretion
possibilities (keep pace, marginal/keep pace,
marginal, marginal/loss, loss) for each of three
sea level rise scenarios. That specification
seemed to suggest a map for each sea level rise
scenario—which could lead us to an unwieldy
proliferation of maps. Putting all the information
on a single map seemed more desirable.
Fortunately, only 8 of the possible 15
combinations (5 accretion sensitivities by 3 sea
level scenarios) occurred, a manageable number
of colors.8 Ignoring the areas of uncertainty (e.g.,
8During an initial review, the total number of combinations
was reduced to 7, because the only polygon where
wetlands were marginal at +7 mm/yr had been erroneously
denoted as such. We've left that combination within the
legend bar because it is an obvious possibility that may
emerge during subsequent review or in other study areas.
marginal/loss) actually leaves us with only 6
sensitivities, for which we defined the following
colors.
We then defined intermediate colors for two
other, more intermediate specifications: marginal
today, marginal/loss at current +2 mm/yr, loss at
current + 7 mm/yr (orange) and keep pace with
current + 2 mm/yr and marginal/loss at current +
7 mm/yr (yellow). Figure 2.2.5 shows the
resulting map for wetland accretion. The zipped
file with which this data is distributed includes
jpg's for the quads and the regions, as well as an
overview map, following that color scheme. The
reader may notice that the polygon boundaries
and map colors in Figures 2.2.4 and 2.2.5 have
been assigned to most of the tidal wetlands that
had been omitted from the polygons in Figure
2.2.2. However, some of the wetlands around
Rehoboth Bay were still unassigned. Similarly,
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[ 184 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
assigning the map colors allowed us to notice a
number of errors. We queried the data to identify
all wetlands that had not been assigned a
geomorphic setting, and looked for other cases
where the geomorphic setting had a clear map
boundary error.9 We corrected the polygons
based on our understanding of the panel's intent
as documented by Reed et al. (see note 1).
Legend
One problematic aspect with maps following the
format of Figure 2.2.5 is that the keys take a lot
of words to repeat the same concepts. A single
color bar would be preferable; but the panel did
not characterize the
wetlands with a single
condition. We
experimented with a pair
of color bars, but people
found that approach too
confusing. The simplest
alternative to a lot of
words appears to be a
table, with a color bar.
(See Figure 2.2.6.)
Maps 2.2.1 and 2.2.2 provide the regional
summary maps that we created based on the
aforementioned considerations. Because the
panel wanted to include subregional maps in the
panel report, we also provided subregional maps.
We do not reproduce those maps here but they
are available with the data product EPA is
distributing.10 The consensus of panel members
was that the accretion map is not valid at large
scales. Therefore, the subregion-specific maps
should not be reproduced without both a warning
and an explanation about why the maps are being
reproduced at this scale.11
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
Current rate
Yes
?
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes?= Wetland would be marginal or lost
Figure 2.2.6. Legend for wetland accretion map.
9For example, the polygon boundaries did not match—or
the geomorphic setting was different—at a quadrangle
boundary.
11 "Upon release of this report, EPA will make the data set
described in this paper available to all researchers.
11 Given the 1 cm errors in the hand renderings. National
Map Accuracy standards would suggest a 1:5,000,000
scale.
-------
[ SECTION 2.2 185 ]
Atlantic
Ocean
Geomorphic Setting
| Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
| Saline fringe
Tidal fresh forest
Tidal fresh marsh
Map 2.2.1. Geomorphic Setting of Tidal Wetlands: Montauk Point to Virginia Beach
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[ 186 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]
Atlantic
Ocean
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
I
i
Current rate
Yes
?
?
No
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
?
No
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
?
No
? = Wetlands would be marginal Yes? = Wetland would be marginal or lost
Map 2.2.2 Potential for Tidal Wetland Accretion in the Mid-Atlantic: Montauk Point to Virginia Beach.
-------
3. MID-ATLANTIC COASTAL HABITATS AND
ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL
RISE
This section should be cited as:
Strange, E.M., A. Shellenbarger Jones, C. Bosch, R. Jones, D. Kreeger, and J.G. Titus.
2008. Mid-Atlantic Coastal Habitats and Environmental Implications of Sea Level Rise.
Section 3 in: Background Documents Supporting Climate Change Science Program
Synthesis and Assessment Product 4.1, J.G. Titus and E.M. Strange (eds.). EPA
430R07004. U.S. EPA, Washington, DC.
-------
3.1 Overview
Author: Ann Shellenbarger Jones, Industrial Economics Inc.
This overview considers the species and habitats
of the mid-Atlantic from Virginia to New York
that are at risk from sea level rise. For different
habitats in this region, the ecological
implications of sea level rise vary in extent and
certainty. Vegetation type, soil type, sediment
inputs, and current ecological health can all
affect the ecological response to sea level rise. In
turn, the animal species that depend on these
habitats for activities such as foraging or nesting
will vary in their responses to habitat changes,
depending on species-specific responses to
changes in inundation, salinity, vegetation
structure and composition, and other habitat
characteristics. Where it is used, shoreline
armoring will influence the ability of both
habitats and biota to adapt to sea level rise. The
following bullets summarize the assumptions on
potential responses of mid-Atlantic habitats to
increasing rates of sea level rise and shoreline
armoring, based on answers to CCSP 4.1
Questions 2 and 31:
• Rising sea level can cause tidal marshes
(e.g., salt, brackish, and freshwater tidal
marshes) to erode at the waterward
boundary; drown in place and convert to
open water; vertically keep pace with sea
level rise through sedimentation and peat
formation; and/or expand inland as areas just
above the level of the tides become
inundated. If sea level rise increases the
salinity of an estuary, the vegetation
composition of brackish and freshwater
marshes may shift to more salt-tolerant
'Question 2: How does sea level rise change the ocean coastline?
Among those lands with sufficient elevation to avoid inundation,
which land along the Atlantic Ocean could potentially erode in
the next century? Which lands could be transformed by related
coastal processes? Question 3: What is a plausible range for the
ability of wetlands to vertically accrete, and how does this range
depend on whether shores are developed and protected, if at all?
In other words, will sea level rise cause the area of wetlands to
increase or decrease?
species. In areas where habitat is lost or
degraded, the myriad species dependent on
marshes—birds, fish, invertebrates, and
mammals—may show decreased growth,
reproduction, or survival.
• Tidal freshwater swamp forests, like
marshes, can retreat at the waterward
boundary; drown in place; keep pace with sea
level rise; and/or expand inland. In addition,
saltwater can induce vegetation shifts or
cause swamps to convert to open water by
oxidizing organic soils or inducing
subsidence. Within the study region, these
swamp forests are found primarily in the
tributaries of Chesapeake Bay. With
inundation, an associated increase in salinity
in the upper reaches of rivers will cause
larger trees to die, opening space for
germination, settlement, and establishment of
marsh macrophytes.
• Marsh and bay islands are found throughout
the mid-Atlantic study region. These isolated
areas provide nesting sites that are protected
from predators and human disturbance for
various bird species, particularly colonial
nesting water birds. Because of their limited
migration ability, these islands are
particularly susceptible to sea level rise.
• Sea level fens are an extremely rare type of
coastal wetland. These fens grow only under
unusual circumstances—where a natural seep
from a nearby slope provides nutrient-poor
groundwater to support their unique
vegetation and where the fens are protected
from nutrient-rich tidal flow. Sea level fens
are present in Delaware's Sussex County
Inland Bays watershed, on Long Island's
South Shore, and on the eastern shore of
Virginia's Accomack County. Because sea
level fen vegetation needs nutrient-poor
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[ SECTION 3.1 189 ]
waters, these unique wetlands might not
survive inundation by sea level rise.
• In nearshore waters, rising sea levels and
deepening waters will shade the deeper areas
of submerged aquatic vegetation (SAV) beds,
limiting photosynthesis. The landward edges
of SAV may move inland onto areas that are
currently tidal wetlands if the water bottoms
have suitable sediments. Seagrasses (e.g.,
eelgrass and widgeon grass) provide food
and shelter for a variety of fish and shellfish,
food for the species that prey on those fish
and shellfish, and physical protection from
wave energy for shorelines. Scientists are not
certain of the likely net change in SAV,
which will depend on the balance between
losses resulting from increasing depth in
current beds and gains due to migration into
inundated shoreline areas.
• Tidal flats may be readily lost with rising
seas, but may also be created temporarily in
areas where wetlands are inundated. Loss of
tidal flats would eliminate a rich invertebrate
food source for migrating birds.
• Estuarine beaches erode, but under natural
conditions the landward and waterward
boundaries usually retreat by about the same
distance. In the built environment, structures
can prevent the system from migrating
inland, in effect causing the beaches to be
squeezed between developed areas and the
water. Society will preserve many beaches
with sand replenishment (beach
nourishment). In areas that do lose beaches,
though, insects and other invertebrates such
as sand diggers, sand fleas, and numerous
crab species will lose their habitats.
Shorebirds that rely on beaches for forage
and nesting will also face more limited
resources.2
• Cliff areas can experience increased erosion
rates, or, if the cliff base is armored, the
erosion rates can decrease. In the latter case,
2Lippson, A.J., and R.L. Lippson, 2006, Life in the Chesapeake
Bay, 3rd ed., The Johns Hopkins University Press, Baltimore,
MD, pp. 26—42. For more detail on beach habitats and the species
that occur in them, see Section 3.1.7 of this section.
however, the armoring can eliminate habitat
for species (e.g., Puritan tiger beetles and
belted kingfishers) that depend on varying
rates of cliff erosion.
This section gives a general description of
vulnerable coastal habitats and potential
ecological consequences of sea level rise and
shoreline armoring in the U.S. mid-Atlantic
region from Virginia to New York. The
information presented here is based on current
scientific understanding as well as the
observations of local experts. In each section that
follows this overview, we begin by describing
the type of habitat (refer to the previous bulleted
list), then discuss potential ecological responses
to sea level rise and to shoreline armoring (if
any) for that type of habitat, presenting case
studies for specific bays, estuaries, and back
barrier lagoons of the mid Atlantic from New
York to Virginia.
Various general assumptions are made in this
section based on other information from the
CCSP and the scientific literature. Assumptions
for marsh survival rely on the response to CCSP
4.1, Question 3 (Reed et al., Section 2.1), which
describes accretion expectations under three sea
level rise scenarios for marshes in the mid-
Atlantic region. The three scenarios are (1) the
current rate of sea level rise, (2) an increase of 2
mm/yr above the current rate, and (3) an increase
of 7 mm/yr above the current rate. The accretion
expectations take into account sediment inputs,
marsh characteristics, and historical processes,
among other considerations.
Changes in salinity are not directly considered in
this section. In the absence of other factors, sea
level rise is expected to drive the salt front
farther upstream in estuaries and tributaries. For
example, one estimate for the Delaware River is
an 11 km movement upstream for the salt front.3
More recent models, however, indicate that any
concomitant changes in freshwater inputs to
tributaries may negate the upstream drive of the
3Hull, C.H.J., and J.G. Titus, 1986, Greenhouse Effect, Sea-Level
Rise, and Salinity in the Delaware Estuary, US EPA 230-05-86-
010, U.S. EPA and Delaware River Basin Commission,
Washington, DC, p. i.
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[ 190 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
salt wedge.4 Although salinity change can have
profound effects on both flora and fauna, we do
not consider it in detail here because of the
uncertainty associated with salinity.
Changes in water depth will be a function of the
rate of sea level rise and the rate of
sedimentation.5 In embayments and estuaries
where the tidal prism increases, increased water
depth is likely.6 In Chesapeake Bay, some
researchers anticipate a water depth increase of
almost 20 percent.7 On the other hand, studies in
England have indicated that estuarine channels
might become both wider and shallower, which
may be an effect of sedimentation and local
geomorphology.8 Increased tidal prism is also
associated with an increase in interior ponding in
marshes, along with tidal creek bank erosion,
which can lead to catastrophic marsh loss (as in
the Blackwater Wildlife Refuge on Maryland's
Eastern Shore).9 We assume that in areas where
marshes are not expected to accrete sufficient
sediment to remain in place, an increase in water
depth will occur over any given area waterward
of the marsh. Shoreline protections can further
affect local water depths and are discussed in
each section as necessary.
3.1.1 TIDAL MARSHES
Tidal marshes are characterized based on
salinity. Freshwater marshes receive significant
4Najjar, R.G., H.A. Walker, P.J. Anderson, E..T. Barron, R..T.
Bord, J.R. Gibson, V.S. Kennedy, C.G. Knight, J.P. Megonigal,
R.E. O'Connor, C.D. Polsky, N.P. Psuty, B.A. Richards, LG.
Sorenson, E.M. Steele, and R.S. Swanson, 2000, "The potential
impacts of climate change on the mid-Atlantic Coastal Region,"
Climate Research 14: 219-233, pp. 224-225.
'National Research Council (U.S.), 1987, Responding to Changes
in Sea Level: Engineering Implications, Committee on
Engineering Implications of Changes in Relative Mean Sea
Level, National Academy Press, Washington, DC, p. 36.
"Levin, D.R., 1995, "Occupation of a relict distributary system by
a new tidal inlet, Quatre Bayou Pass, Louisiana," pp. 71-84 in
Tidal Signatures in Modem and Ancient Sediments, B.W.
Flemming and A. Bartoloma, eds., Special Publication of the
International Association of Sedimentology (vol. 24.), Blackwell
Science, Oxford, U.K.
7Stevenson, J.C., M.S. Kearney, andE.W. Koch, 2002, "Impacts
of sea level rise on tidal wetlands and shallow water habitats: A
case study from Chesapeake Bay," American Fisheries Society'
Symposium 32:23-36.
8Pethick, J., 1993, "Shoreline adjustments and coastal
management: Physical and biological processes under accelerated
sea-level rise," The Geographical Journal 159(2): 162-168.
'National Research Council, 1987, p. 69 (see note 5).
freshwater input and have waters that contain
less than 0.5 parts per thousand (ppt) of ocean-
derived salts. The waters of brackish (estuarine)
marshes are less than 18 ppt. Salt marshes
receive substantial inundation by ocean waters
and have waters that can reach 30 ppt. As
discussed in the following sections, numerous
finfishes, birds, crustaceans, mollusks, reptiles,
amphibians, and mammals rely on tidal marshes
for at least part of their life cycle for resources
such as food, shelter, nursery habitat, and nesting
or spawning sites.
Salt marshes are among the most productive
systems in the world, rivaling the productivity of
agricultural lands. These marshes are the primary
source of much of the organic matter and
nutrients that form the basis of the estuarine food
web.1" Primary productivity includes both
aboveground production (stalks and leaves) and
belowground production (roots and tubers) by
marsh plants as well as benthic algae. Much of
the aboveground primary production is in the
form of cellulose, which most animals cannot
digest. Therefore, most vascular plant material is
consumed by detritivores such as copepods,
amphipods, annelids, snails, and insect larvae.11
In turn, these organisms provide food for
macroinvertebrates such as saltmarsh snails,
ribbed mussels, and fiddler crabs, and small
resident fishes such as mummichogs, sheepshead
minnows, and Atlantic silversides.12 The
abundant invertebrates and small fishes of salt
marshes are food for larger consumers. Bay
anchovies, silversides, and other small schooling
species use salt marshes as nursery grounds and
are a food source for birds and piscivorous
fish.13"14
10Teal, J.M., 1986, The Ecology of Regularly Flooded Salt
Marshes of New England: A Community Profile, U.S. Fish and
Wildlife Service Biological Reports 85 (7.4), 69 pp.
"Currin, C.A., S.Y. Newell, and H.W. Paerl, 1995, "The role of
standing dead Spartina alterniflora and benthic macroalgae in
salt marsh food webs: Considerations based on multiple stable
isotope analysis," Marine Ecology Progress Series 121:99-116.
12Teal, 1986, pp. 21-25 (see note 10).
13McBride, R.S., 1995, "Marine forage fish," pp. 211-217 in
Dove, L.E., and R.M. Nyman (eds.), Living Resources of the
Delaware Estuary. The Delaware Estuary Program.
14Lippson and Lippson, 2006, p. 212 (see note 2).
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[ SECTION 3.1 191 ]
Photo 3.1: Marsh and tidal creek, Mathews County, Virginia
Birds that feed on crustaceans, mollusks, and
fish within salt marshes include clapper rails,
black rails, least bitterns, and many species of
terns and gulls. Fiddler crabs are common in the
diets of clapper rails, egrets, blue crabs,
diamondback terrapins, and raccoons. Some of
the birds are marsh-nesting obligates; others nest
frequently, but not exclusively, in marshes.
Three species of terns (including Forster's tern),
several species of gulls, and the seaside and salt
marsh sharp-tailed sparrows all nest in coastal
salt marshes.
In addition to secondary production within the
marsh, some primary production may ultimately
contribute to the surrounding estuarine food web.
Kneib proposes that this occurs via "trophic
relays," which consist of juvenile fauna that
draw on the detrital food web of the marsh and
then transfer marsh-produced organic matter to
larger consumers as part of the estuarine food
web.17
15
Salt marshes are
characterized by distinct
vegetation zones based on
the degree of tidal
flooding and the salinity
tolerance of marsh plants.
Because they are
regularly flooded by daily
tides, low marsh soils
tend to be more
waterlogged, saline, and
anoxic than high marsh
soils.18 Low marsh is
characterized by
monospecific stands of
smooth cordgrass.
Characteristic bird species
of low marsh include
clapper rail, willet, marsh
wren, seaside sparrow,
and American black duck. Ribbed mussels form
dense clumps on cordgrass roots and fertilize
them by contributing phosphorous and nitrogen-
rich pseudofeces.19 Fiddler crabs enhance
Sparthia spp. survival by aerating the marsh
soils.2"
Tidal creeks and channels frequently cut through
low marsh areas, functioning to drain the marsh
surface and serving as conduits for nekton (small
fish and decapod crustaceans) to enter the
wetlands during high tides and for nutrient-rich
plant detritus to be flushed out into deeper water
with receding tides (see Photo 3.1).21 Several fish
species that are marsh residents and use the low
marsh when it is flooded at high tide are found in
tidal creeks at low tide, including Atlantic
silversides, mummichogs, striped killifish, and
sheepshead minnows. Marsh creeks support
significantly higher densities of these species
than other intertidal habitats.22
l ,All photos are courtesy of Jim Titus, except for Photo 3.3a by
Elizabeth Strange.
l0Erwin, R.W., G. M. Sanders, and D. J. Prosser, 2004, "Changes
in lagoonal marsh morphology at selected northeastern Atlantic
Coast sites of significance to migratory waterbirds," Wetlands
24(4): 891-903.
17Kneib, R.T., 1997, "Tidal marshes offer a different perspective
on estuarine nekton," .• iminal Review of Oceanography and
Marine Biology 35:1-120.
1?LaBranche, I, M. McCoy, and D. Clearwater, 2003, p. 17 in
Maryland State Wetland Conservation Plan, prepared by
Nontidal Wetlands and Waterways Division, Maryland
Department of the Environment.
19Kreamer, G.R., 1995, Saltmarsh invertebrate community, pp.
81-89 in Dove and Nyman, 1995 (see note 14).
20Dove and Nyman, 1995, pp. 81-89 (see note 14).
21Lippson and Lippson, 2006, pp. 202-203 (see note 2).
"Rountree, R.A., and K.W. Able, 1992, "Fauna of polyhaline
subtidal marsh creeks in southern New Jersey: Composition,
abundance and biomass,"Estuaries 15:171-185.
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[ 192 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Characteristic macroinvertebrates of salt marsh
creeks include eastern mud snails, daggerblade
grass shrimp, longwrist hermit crabs, common
Atlantic slippershells, northern quahogs,
softshell clams, razor clams, blue crabs, and
horseshoe crabs. Great blue herons and egrets are
among the many colonial wading birds and other
waterbirds that commonly feed on the small fish
and benthic invertebrates found in tidal creeks. If
creeks deepen, these species will have increasing
difficulty foraging for essential food supplies.
High marsh is briefly flooded once or twice daily
on fewer than 10 days per month and is
dominated by salt hay and spike grass. High
marsh sediment contains more organic material
than low marsh.23"24 High marshes may include a
scrub-shrub community at the upland edge. Salt
shrubs often mark the limit of the highest spring
and storm tides. Characteristic shrubs include
groundsel, saltmarsh elder, and pasture rose. The
marsh edge is typically dominated by salt marsh
elder, whereas groundsel usually dominates the
upland edge. Grasses include those typical of
high salt marsh, including salt meadow grass,
black grass, and switchgrass. The invasive
common reed sometimes occurs in a narrow
fringe along the upland edge of marshes where
salinities are lower because of less tidal flooding
and greater freshwater runoff.
Characteristic birds of high salt marsh include
saltmarsh sharp-tailed sparrows, black rails, and
northern harriers. Many of these high marsh
species are adapted to nesting only in the short
grasses of the high marsh, such as salt hay and
spike grass, and may not thrive in the tall grasses
of the low marsh.
Brackish or estuarine tidal marshes in
estuaries of the mid-Atlantic are typically
dominated by species such as Olney three-
square, saltmarsh bulrush, switchgrass, dwarf
spike grass, black needlerush, narrow-leaved
cattail, big cordgrass, and the invasive common
reed. In mixed communities, the vegetation
occurs in zones. Big cordgrass is the most
23Brinson, M.M., R.R. Christian, and L.K. Blum, 1995, "Multiple
states in the sea level induced transition from terrestrial forest to
estuary," Estuaries 18(4): 648-659.
24LaBranche et al., 2003, p.17 (see note 18).
common near mean high tide (MHT), Olney
three-square at MHT, and switchgrass near the
spring tide line. Brackish marshes support many
of the same species as salt marshes, with some
notable exceptions. Bald eagles forage in
brackish marshes and nest in nearby wooded
areas. Because there are few resident mammalian
predators, small herbivores such as meadow vole
thrive in these marshes.25
Fish species common in the brackish waters of
the mid-Atlantic include striped bass and white
perch, which move in and out of brackish waters
year-round. Anadromous fishes, including
herring and shad, as well as marine transients
such as Atlantic menhaden and drum species, are
present in summer and fall. The most visible
invertebrates of the brackish marshes include
red-jointed fiddler crab, marsh periwinkle,
Atlantic ribbed mussel, and common clam
worm.26
Freshwater tidal marshes are characteristic of
the upper reaches of tributaries of estuaries. They
support a more diverse vegetation community
than more saline marshes. Like salt and brackish
marshes, freshwater tidal marshes can show three
distinct vegetation zones, depending on the
degree of tidal inundation. In general, the lower
tidal zone, exposed only at low tide, consists of
sparsely vegetated intertidal flats. The middle
zone is dominated by wild rice, spatterdock,
pickerelweed, and arrow arum. The upper tidal
zone is dominated by cattails, often with a
diversity of other species such as sensitive fern,
river bulrush, and sweet flag, and sometimes the
invasive common reed.27
In general, the species composition of freshwater
marshes does not appear to be limited by seed
availability. Instead, physical factors limit the
species composition, especially through
flooding. Some species germinate well when
25White, C.P., 1989, Chesapeake Bay: Nature of the Estuary, A
Field Guide, Tidewater Publishers, Centreville, MD, pp. 107-
123.
2"White, 1989, p. 124 (see note 25).
"White, 1989, pp. 97-105 (see note 25).
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[ SECTION 3.1 193 ]
completely submerged; others are relatively
intolerant of flooding.28
Tidal freshwater marshes provide shelter, forage,
and spawning habitat for numerous fish species,
primarily cyprinids (minnow, shiner, carp);
centrarchids (sunfish, crappie, bass); and
ictalurids (catfish). Some estuarine fish and
shellfish can also complete their life cycle in
freshwater marshes.29
Freshwater tidal marshes are also important for a
wide range of bird species, and some ecologists
suggest that these marshes support the greatest
diversity of bird species of any marsh type,
including a variety of waterfowl; wading birds;
rails and shorebirds; birds of prey; gulls, terns,
kingfishers, and crows; arboreal birds; and
ground and shrub species.30 Perching birds such
as red-winged blackbirds are common in stands
of cattail. Tidal freshwater marshes support
additional species that are rare in saline and
brackish environments, such as frogs, turtles, and
snakes.31
In addition to food and shelter for various
species, marshes also improve water quality in
the surrounding river or estuary. The marshes
serve as filters for water draining from
surrounding upland areas. In particular, marshes
work to remove nutrients from runoff, process
chemical and organic wastes, and reduce the
terrigenous sediment load to the water column.32
Marsh processes remove nitrogen and
phosphorus compounds (e.g., nitrates, ammonia,
and phosphates) from the water stream. The
denitrification process (bacterial conversion of
ammonia or nitrates from organic wastes and
fertilizer into nitrogen gas) provides significant
benefits to water quality. High levels of nutrients
in coastal waters from nonpoint source runoff
lead to algal blooms and hypoxia, which can kill
large numbers of fish. Marsh vegetation also
retains much of the terrigenous sediment load
28Mitsch, W.J., and J.G. Gosselink, 2000, Wetlands, 3rd ed., Van
Nostrand Reinhold, New York, p. 275.
29Mitsch and Gosselink, 2000, p. 277 (see note 28).
30Mitsch and Gosselink, 2000, p. 279-280 (see note 28).
3'White, 1989, pp. 107-109 (see note 25).
32Tiner, R.W., andDG. Burke, 1995, Wetlands of Maryland,
U.S. Fish and Wildlife Service, Region 5, Hadley, MA, pp. 146—
147.
from runoff, which can interfere with
photosynthesis in the water column (e.g., for
SAV) and can cause siltation in nearshore areas
(e.g., SAV or oyster beds).
Effects of Sea Level Rise on Tidal
Marshes
The ability of tidal marshes to migrate in
response to sea level rise depends on the supply
of sediment and organic matter that is available
to raise the marsh surface, the local tidal range,
and the slope of nearby lowland. In addition,
shoreline protection structures can block inland
migration. The placement of hard structures
reduces sediment inputs from upland sources and
increases erosion waterward of a structure.
Tidal marshes may keep pace with sea level rise
through vertical accretion and inland migration,
as long as there is a dependable source of
terrigenous sediment and the marsh can maintain
the same elevation relative to the tidal range. In
areas where neither sufficient accretion nor
migration can occur, increased tidal flooding can
stress marsh plants through waterlogging and
changes in soil chemistry, leading to a change in
species composition and vegetation zones. If
marsh plants become too stressed and die, the
marsh will eventually convert to open water or
mudflats (see Photo 3.2).33-34
Steadily increasing relative sea levels may cause
more frequent events such as saltwater flooding,
storm overwash, and wrack deposition. These
events, in turn, can trigger changes in wetland
ecosystems.35 The ability of marsh vegetation to
accrete terrigenous sediment and migrate inland
will determine marsh survival.36Marsh types,
33Callaway, J.C., J.A. Nyman, and R.D. DeLaime, 1996,
"Sediment accretion in coastal wetlands: A review and a
simulation model of processes," Current Topics in Wetland
Biogeochemistry 2:2-23.
34The Plum Tree Island National Wildlife Refuge is an example
of a marsh deteriorating through lack of sediment input and
migration capacity, due to development on its landward side.
Extensive mudflats front the marsh. See Section 3.11 on
Hampton Roads.
35Brinson et al., 1995, p. 655 (see note 23).
3oWard, L.G., M.S. Kearney, and J.C. Stevenson, 1998,
"Variations in sedimentary environments and accretionary
patterns in estuarine marshes undergoing rapid submergence,
Chesapeake Bay."Marine Geology' 151:111-134.
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[ 194 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Photo 3.2: Fringing March and Bulkhead, Monmouth County, New
Jersey
however, have differing capacities for sediment
accretion. Facing increasing rates of sea level
rise, high marshes may not be able to trap and
accrete sufficient sediment, whereas low tidal
marshes, both fresh and estuarine, are more
likely to have this ability. Marshes without
riverine sediment input, such as those that fringe
islands, are at the greatest risk from sea level
rise.J / Sediment transport in low marsh areas is
facilitated by tidal creeks, which frequently
occur in networks throughout broad areas. These
networks are absent in more mature marshes and
in upland areas, limiting sediment input for high
marshes.38
If accretion does not maintain the marsh in place,
migration is also a possible mechanism for
marsh survival. In addition to artificial and
natural barriers (e.g., armoring structures),
sediment requirements also impede wetland
migration. Bare patches and a more mineral
sandy substrate are necessary for lower marsh
vegetation species to migrate onto areas that
once were high marsh. For successful transition,
a variety of factors, including
localized topographic
changes, erosion, deposition
of wrack on high marsh
plants, and ponding, can
contribute to deterioration of
the high marsh organic-rich
peat and allow for
colonization by low-marsh
Spar Una alterniflora39 S.
alterniflora can aggressively
colonize high marsh areas
that have been devegetated
by wrack deposition from a
storm or overwash event.
Even though S. alterniflora
can colonize deteriorated
high marsh areas with
suitable sediment types,
factors that reduce wetland
vegetation's ability to trap
sediments (e.g., construction of roads across
them or reductions in sediment supply) and the
processes that drive deterioration (described
previously) can continue even in the absence of
further sea level rise, resulting in total marsh
loss.4"
Local variation in rates of terrigenous
sedimentation and other processes such as
erosion will determine accretion and migration at
specific sites.41 In addition to anthropogenic or
natural physical barriers, storm-induced erosion
and sediment deficits can preclude migration. In
Chesapeake Bay, scientists estimate that "the
influx of particulates is not high enough to keep
pace with relative sea level rise" on a bay-wide
scale.42 A trend of decreasing sediment inputs
from major mid-Atlantic rivers because of
farmland abandonment in the mid-Atlantic
'Najjar et al., 2000, p. 223 (see note 4).
^Stevenson, J.C., and M.S. Kearney, 1996,
''Shoreline dynamics
on the windward and leeward shores of a large temperate
estuary," pp. 233-259 in Estuarine Shores: Evolution,
Environments, and Human Alterations, K.E, Nordstrom and C.T.
Roman (eds.), John Wiley & Sons, New York; and Najjar et al.,
2000, p. 223 (see note 4).
39Brinson et al., 1995, p. 655 (see note 23).
4flStevenson and Kearney, 1996, p. 238 (see note 38).
41Ward et al. (1998) (see note 36) found that accretion rates tend
to decrease down-estuary in the Nanticoke, an eastern Bay
tributary. Overall, rates in embayment marshes were close to or
less than the local sea level rise and not as spatially patterned as
the tributary marshes. A 0.24 cm/year accretion rate at the mouth
of an estuarine tributary (the Nanticoke) compared to a 0.19
cm/year accretion rate for an interior marsh area ("Variations in
sedimentary environments," p. 125). In Monie Bay, a low organic
content was found, indicating a higher level of mineral soils and
suggesting that accretion rates are lower than relative sea level
rise ("Variations in sedimentary environments," p. 127).
Stevenson and Kearney, 1996, p. 236 (see note 38).
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[ SECTION 3.1 195 ]
region suggests that a lack of sediment may also
affect wetlands outside of Chesapeake Bay.43
Similarly, lagoonal marshes, areas within
embayments or larger marsh systems, and
marshes migrating inland that are remote from
tributary sediment inputs may not be able to keep
pace with sea level rise.44 In areas without
sufficient sediment, wetlands may transition to
tidal flat or open water.
Vegetation type can also affect the ability of a
marsh to accrete sediment. Greater rates of
mineral and organic sediment trapping have been
associated with common reed (as compared to
Spartinci spp.) in both a subsiding creek bank
marsh and a laterally eroding marsh.45
Researchers indicate that belowground
productivity most likely plays a key role in the
ability of the common reed to rapidly increase
substrate level.46 Given the greater ability of
marshes dominated by common reed to meet
increased rates of sea level rise, expected
ecological effects are lower in these areas.47
Effects of Armoring on Tidal Marshes
Shoreline protection can affect both migration
and accretion for wetlands. Increases in wave
energy generated by armoring structures can
eliminate marsh areas waterward of the
structures.48 Sediment scoured from bulkhead
bases in estuaries can "cover spawning habitats
formerly used by forage fish that spawn in the
upper intertidal zone."49 Marsh and tidal areas
43Najjar et al., 2000, p. 223 (see note 4).
44Erwin et al., 2004, p. 892 (see note 16).
45Rooth, J.E. and J.C. Stevenson, 2000, "Sediment deposition
patterns in Phragmites australis communities: Implications for
coastal areas threatened by rising sea-level," Wetlands Ecology'
and Management 8:173-183.
46Ibid.
47At Eastern Neck National Wildlife Refuge, Maryland,
managers are leaving phragmites stands in place as a strategic
action against erosion. See Section 3.17, Chesapeake Bay's
Upper Bay, of this section.
48U.S. Geological Survey (USGS), 2003, "A summary report of
sediment processes in Chesapeake Bay and watershed," p. 55 in
Water-Resources Investigations Report 03-4123, USGS, Reston,
VA.
49Small, D., and R. Caiman, 2005, "Marine shoreline armoring in
Puget Sound and the Washington State Hydraulic Code," p. 1 in
Proceedings of the 2005 Puget Sound Georgia Basin Research
Conference, March 29-31, 2005. Available at:
http://www.engi.washington.edu/epp/psgb/2005psgb/2005piocee
dings/index.html from the Univeisity of Washington, College of
Engineering.
reinforced with armoring that prevents habitat
migration will suffer the greatest loss of
habitat.5"'51 Elimination of these wetland areas
will also reduce the shoreline's ability to buffer
the effects of erosion and floods and to filter
nutrient and contaminant loads in runoff.
Ecological Effects on Tidal Marshes
Where tidal wetlands are lost, the myriad species
that depend on marshes—birds, fish,
invertebrates, amphibians, reptiles, and
mammals—can show decreased growth,
reproduction, or survival resulting from a
decrease in habitat quantity or quality. If salt
marsh areas are lost, avian marsh-nesting
obligates such as Forster's terns, black rails,
clapper rails, northern harriers, American black
ducks, seaside sparrows, and sharp-tailed
sparrows will lose habitat and are likely to suffer
reproductive stress.52 Lagoonal marshes and mid-
embayment areas are particularly susceptible to
changes induced by sea level rise. Tidal flats will
be inundated, and although changes in extent
might be localized at first, scientists anticipate an
overall reduction in forage habitat for shorebirds.
Sea level rise is also advancing the salinity
gradient upstream in some rivers, leading to
shifts in vegetation composition and the
conversion of some tidal freshwater marshes into
oligohaline marshes.53 High brackish marshes
can deteriorate as a result of ponding and wrack-
smothering of vegetation as salinity increases
with rising seas and storms accentuate the
fragmentation of the marshes.54 This process may
allow colonization by lower marsh species, but
50Galbiaith, H., R. Jones, P. Paik, J. Clough, S. Henod-Julius, B.
Hanington, and G. Page, 2002, "Global climate change and sea
level rise: Potential losses of inteitidal habitat foi shoiebiids,
Waterbirds 25(2): 173—183.
51Oystei Bay, New Yoik, has experienced extensive maish loss
as a result of bulkheading. See Section 3.3, Long Island South
Shore.
52Foi example, seaside and shaip-tailed spanows are both
prevalent in at-risk maishes on Viiginia's Eastern Shore. See
Section 3.19.
53Maiyland Department of Natural Resources (DNR), 2005,
Chapter 4, Part 2, p. 49 in Wildlife Diversity> Conservation Plan—
Final Draft, available at:
http://www.dni.state.md.us/wildlife/divplan_wdcp.asp (accessed
Febiuaiy 28, 2007).
54Along the Patuxent Rivei, Maiyland, refuge manageis have
noted maish deterioration and ponding with sea level rise. See
Section 3.16 on the Western Shore.
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[ 196 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
that outcome is not certain.55 Low brackish
marshes may change dynamically in area and
composition as sea level rises. If they are lost,
forage fish and invertebrates of the low marsh—
such as fiddler crabs, grass shrimp, and ribbed
mussels—will no longer be available to the
predators that consume them. Even though more
ponding and "pannes" might provide some
additional foraging areas as marshes deteriorate,
the associated increase in salinity due to
evaporative loss will drive vegetation changes to
less diverse assemblages of salt-tolerant
species.56 In fact, high salt conditions will be
lethal for many species.
If marshes can migrate, changes in vegetation
assemblages will in turn affect the faunal species
that forage, nest, spawn, and seek shelter in tidal
marshes. Factors affecting fauna include reduced
available oxygen, structural changes in
vegetation, and reduction of foraging areas in
tidal flats. In these hypoxic conditions, more
salt-tolerant fishes such as mummichogs and
killifishes become prevalent.57
In areas where marshes are reduced, remnant
marshes might provide lower quality habitat and
pose greater predation risk for a number of bird
species that are marsh specialists and are also
important components of marsh food webs.
These species include the clapper rail, black rail,
least bittern, Forster's tern, willet, and laughing
gull.58 Scientists estimate that as much as 80
percent of the Atlantic Coast breeding population
of Forster's tern and 70 percent of laughing gull
are at risk because of habitat loss due to sea level
rise.59 Populations of some noncolonial species
are also at risk because of their already-low
population sizes, estimated at about 142,000 for
the clapper rail, 102,000 for the willet, and as
little as 13,000
"Stevenson and Kearney, 1996, p. 236 (see note 38).
'"Maryland DNR, 2005, p. 49 (see note 53).
57Stevenson et al., 2002, pp. 25-26 (see note 7).
58Erwin, R.M., G.M. Sanders, D.J. Prosser, and D.R. Cahoon,
2006, "High tides and rising seas: potential effects on estuarine
waterbirds," pp. 214-228 in Terrestrial Vertebrates of Tidal
Marshes: Evolution, Ecology', and Conservation (R. Greenberg,
J. Maldonado, S. Droege, andM.V. McDonald, eds.). Studies in
Avian Biology No. 32, Cooper Ornithological Society.
59Ibid.
to 14,000 for the American black duck.6" The
number of bird species in Virginia marshes was
found to be directly related to marsh size; the
minimum marsh size found to support significant
marsh bird communities ranged from 4.1 to 6.7
ha.61 Particular species may require even larger
marsh sizes; minimum marsh sizes for successful
communities of the saltmarsh sharp-tailed
sparrow and the seaside sparrow, both on the
Partners in Flight WatchList, are estimated at 10
and 67 ha, respectively.62
Effects of marsh inundation on fish and shellfish
species are likely to be complex. In the short
term, inundation could make the marsh surface
more accessible, increasing production.
The benefits, however, will decrease as
submergence decreases total marsh habitat.63 A
marsh loss model, coupled with shrimp survey
data from the National Marine Fisheries Service,
suggests that losses in yields due to marsh loss
could be as high as 50 percent.64
Deterioration and mobilization of marsh peat
sediments increase the biological oxygen
demand in the immediate vicinity and deplete
oxygen levels to below requirement thresholds
for many game fish such as striped bass. In these
hypoxic conditions, more tolerant fish
assemblages including mummichogs and
killifish, become prevalent.65
60Ibid.
0lWatts, B.D., 1993, Effects of Marsh Size on Incidence Rates
and Avian Community Organization within the Lower
Chesapeake Bay, Center for Conservation Biology Technical
Report CCBTR-93-03, The College of William and Mary,
Williamsburg, VA, 53 pp.
°2Benoit, L.K., and R.A. Askins, 2002, "Relationship between
habitat area and the distribution of tidal marsh birds," The Wilson
Bulletin 114(3):314—323.
o3Rozas, L.P., and D..T. Reed, 1993, "Nekton use of marsh-surface
habitats in Louisiana (USA) deltaic salt marshes undergoing
submergence," Marine Ecology Progress Series 96:147-157.
o4Zimmerman, R.J., 1992, "Global wanning: effects of sea level
rise on shrimp fisheries," pp. 58-73 in Proceedings of the
Southeast Fisheries Science Center Shrimp Resource Review,
K.N. Baxter and L. Scott-Denton (eds.), NOAA Technical
Memorandum, NMFS-SESC-299.
o5Stevenson et al., 2002, pp. 25-26 (see note 7).
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[ SECTION 3.1 197 ]
3.1.2 FRESHWATER SWAMP FORESTS
Limited by their requirements for low salinity
water and high sediment inputs, tidal swamp
forests occur primarily in the upper regions of
tidal tributaries in Virginia, Maryland, Delaware,
New Jersey, and New York.66 Tidal hardwood
swamps occur in all of Virginia's major eastern
rivers, and are particularly pristine in the
Pamunkey and Mattaponi rivers. In these rivers,
pumpkin ash and swamp tupelo are the primary
overstory species. In the Potomac River and
farther north, green ash replaces pumpkin ash as
the dominant species.67 Parts of the Pocomoke
River tidal floodplain forests are dominated by
bald cypress. At the upland edges of tidal river
floodplains, loblolly pine, sweetgum, and oaks
can be present.68 Farther north (into New Jersey
and New York), varying tree species are present,
and the habitat is classified as northern Atlantic
coastal plain tidal swamp.69 North Carolina
contains large stands of forested wetlands,
particularly cypress swamps, as discussed in the
review of ecological impacts in North Carolina
(see, for example, Photo 3.3b).7"
Throughout the forested swamps, "hummock-
and-hollow microtopography" dictates where
trees can establish themselves on small elevated
areas above the highest tide levels.71 A species-
rich herb vegetation layer includes a variety of
""NatureServe, 2006, "NatureServe Explorer: An online
encyclopedia of life" [Web application], Version 5.0,
NatureServe, Arlington, Virginia, available at:
http://www.natureserve.org/explorer, accessed September 1,
2006, and "Northern Atlantic coastal plain tidal swamp,"
CES203.282, accessed on September 1, 2006 at:
http://www.natureserve.org/explorer/servlet/NatureServe7searchS
ystemUid=ELEMENT_GLOBAL.2.723205.
"^Fleming, G.P., P.P. Coulling, K.D. Patterson, and K. Taverna,
2006, "The natural communities of Virginia: Classification of
ecological community groups. Second approximation. Version
2.2," Virginia Department of Conservation and Recreation,
Division of Natural Heritage, Richmond, VA, available at:
http://www.dcr.virginia.gov/dnli/ncintro.htm, accessed June 19,
2007.
o8Maryland DNR, 2005, Wildlife Diversity Conservation Plan, p.
1 (see note 53).
o9Westervelt, K., E. Largay, R. Coxe, W. McAvoy, S. Perles, G.
Podniesinski, L. Sneddon, and K. Strakosch Walz, 2006, A Guide
to the Natural Communities of the Delaware Estuary: Version 1,
NatureServe, Arlington, VA, pp. 270-273.
70Mark Brinson of East Carolina University is providing CCSP
and USGS with an analysis of these wetlands. We hope to work
with him to fully reflect these important wetlands.
^Fleming et al., 2006 (see note 67).
species such as jewelweed, arrow arum, and
sedges in the regularly flooded areas; marsh blue
violet, water hemlock, greenfruit clearweed,
false nettle, and ferns are found on the
hummocks (vegetated mounds that rise above the
adjacent wetland area).72 Tidal swamps support a
variety of wildlife, including the prothonotary
warbler, the two-toed amphiuma salamander, and
the bald eagle. Forested wetlands with thick
understories provide shelter and food for an
abundance of breeding songbirds.73 Various rare
and greatest conservation need (GCN) species
reside in tidal swamps, including the Delmarva
fox squirrel (federally listed as endangered), the
eastern red bat, bobcats, bog turtles, and the red-
bellied watersnake.74
Effects of Sea Level Rise on Tidal
Freshwater Swamp Forests
Tidal freshwater swamp forests are considered
globally uncommon to rare, and face a variety of
threats, including sea level rise. According to
Fleming and colleagues, "Crown dieback and
tree mortality are visible and nearly ubiquitous
phenomena in these communities and are
generally attributed to sea level rise and an
upstream shift in the salinity gradient in
estuarine rivers" (see also Photo 3.3a).75
Ecologists in Virginia note that where tree death
is present, the topography is limiting inland
migration of the hardwood swamp and the
understory is being infilled with marsh species
such as Spar Una.11
Ecological Effects on Tidal Freshwater
Swamp Forests
This pattern of crown dieback and marsh species
migration is likely to continue with sea level rise
acceleration. Salinity may increase as areas are
inundated, eliminating vegetation that relies on
the diluting effect of freshwater inputs. Loss of
72Maryland DNR, 2005, p. 1 (see note 53).
73Lippson and Lippson, 2006, p. 218 (see note 2).
74Maryland DNR, 2005, p. 4 (see note 53).
"Fleming et al., 2006 (see note 67).
7oWritten communication, Gary Fleming, vegetation ecologist,
Virginia Department of Conservation and Recreation, Division of
Natural Heritage. Via email to Christina Bosch, Industrial
Economics, September 11, 2006. Subject: Re: Sea level rise
report wrap-up - please respond.
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[ 198 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
tidal swamp forests would
detrimentally affect the varied
fauna that reside there.
3.1.3 MARSH AND BAY
ISLANDS
Islands are common features
of salt marshes, and some
estuaries and back barrier
bays have islands formed by
deposits of dredge spoil.
Many islands are a mix of
habitat types, with vegetated
and unvegetated wetlands in
combination with upland
areas.77 Shorelines can be
composed of marsh or rocky
or sandy beaches. These
islands are important habitats
for birds because they provide
protection from terrestrial
predators such as the red fox.
Birds such as gull-billed
terns, common terns, black
skimmers, and American
oystercatchers nest on marsh
islands. '8 Many islands
provide secluded areas for
important bird colonies (e.g.,
the colonies of the rare black-
crowned night heron on North
and South Brother i slands in
New York; see Section 3.2 on
Long Island Sound). Salt
marsh islands in the New
Jersey back-barrier bays are
feeding and/or nesting sites
for a variety of birds and
turtles, including several
^Thompson's Island in Rehoboth Bay, Delaware, is a good
example of a mature forested upland with substantial marsh and
beach area. The island hosts a large population of migratory
birds. See Section 3.8 of this section.
78Rounds, R.A., R.M. Erwin, and J.H. Porter, 2004, '"Nest-site
selection and hatching success of waterbirds in coastal Virginia:
Some results of habitat manipulation," Journal of Field
Ornithology 75:317-329; Eyler, T.B., R.M. Erwin, D.B. Stotts,
and J.S. Hatfield, 1999, "Aspects of hatching success and chick
survival in gull-billed terns in coastal Virginia," Waterbirds
22:54-59; and Lauro, B., and J Burger, 1989, "Nest-site
selection of American oystercatchers (Haematopus pa Hiatus) in
salt marshes," Auk 106:185-192.
Photo 3.3a: Inundation and tree mortality in tidal freshwater swamp
at Swan's Point, Lower Potomac River
Photo 3.3b. Cypress along Roanoke River, North Carolina
species of tern, oystercatchers, plovers, and
diamondback terrapins (see Section 3.6 on New
Jersey Shore). Artificially enhanced islands,
generally created through dredge spoil, can
provide similar benefits (e.g., Hart-Miller Island
near Baltimore, Maryland); however, dredge
spoil islands can be particularly susceptible to
erosion (see Section 3.16, Chesapeake Bay's
Western Shore, and discussion of Poplar Island
in Section 3.18, Chesapeake Bay's Central
Eastern Shore). Hummocks can also be
considered a type of island (see Photo 3.4).
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[ SECTION 3.1 199 ]
Barrier islands form where
sand accumulates along
sandy coasts with small or
medium tide ranges and
wide continental shelves.7''
They contain many fragile
habitats such as sand
dunes, maritime forests,
and back-barrier marshes
that provide critical habitat
for many coastal species.
Barrier islands are a
common feature of the
U.S. Atlantic Coast.
Effects of Sea Level
Rise on Islands
Depending on their current
elevations, sediment
supply, and rates of
erosion, wetland islands could become the first
habitats to be eliminated as a result of sea level
rise. Sea level rise poses a unique threat to
islands, in that migration is not an option and
sediment inputs may be limited. Some scientists
believe that salt marsh islands in large coastal
lagoons will be more vulnerable to inundation as
sea level rises than fringing marshes because the
lagoons lack inorganic sediments.8" In some
cases, rising sea level may cause additional
islands to form, as portions of peninsulas erode
and higher water levels separate high ground
from the mainland. Many islands along the mid-
Atlantic Coast, and particularly in Chesapeake
Bay, have been lost or severely degraded
because of sea level rise. Although armoring can
be used to protect these islands, it is not
generally employed because the islands are
undeveloped.
Without human interference, barrier islands often
maintain a state of dynamic equilibrium between
sediment exchange, wave energy, and sea level,
migrating inland through a process often called
"overwash" or "barrier island rollover." Under
some circumstances, however, rising sea level
can increase the frequency of inlets, and under
extreme circumstances, sea level rise can cause
the islands to disintegrate or reform several
kilometers inland. The relatively slow rise in sea
level during the last several centuries has enabled
many barrier islands to widen far beyond their
critical width; it follows that accelerated sea
level rise would tend to cause most barrier
islands to narrow.
Ecological Effects on Islands
For island-nesting bird species, the loss of
wetland islands to flooding and erosion is a
serious problem. A shift to mainland marshes is
generally not an option for these species because
of predators present in those marshes. Numerous
species of special concern, including the piping
plover, nest in the protected back-dune areas of
barri er islands. Loss of these habitats could have
a serious effect on such rare species. To the
extent that estuarine and riverine beaches,
particularly on islands, survive better than barrier
islands, shorebirds like oystercatchers might be
able to migrate to these shores.81
The information presented here on barrier islands is very
limited because CCSP4.1 has at least two nationally recognized
barrier-island experts from USGS; hence this background report
is unlikely to be used for the CCSP discussions of barrier islands.
s0Erwin et al., 2004, pp. 891-903 (see note 16).
slMcGowan, C.P., T-R- Simons, W. Golder, and J. Cordes, 2005,
"A comparison of American oystercatcher reproductive success
on barrier beach and river island habitats in coastal North
Carolina,'' Waterbirds 28:150-155.
Photo 3.4: Marsh Drowning and Hummock in Blackwater Wildlife
Refuge, Maryland
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[ 200 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
3.1.4 SEA LEVEL FENS
The mid-Atlantic region contains a few areas of
the globally rare sea level fen habitat. These fens
are unique combinations of plant species, present
in Delaware's Sussex County Inland Bays
watershed, on Long Island's South Shore, and on
the eastern shore of Virginia's Accomack
County.82 Sea level fens generally occur just
above the upper high tide mark, at the bases of
slopes.83 Groundwater seepage from the slopes
provides sea level fens with nutrient-poor fresh
water. The fens occur only where they are
protected from nutrient-rich tidal flow by a
barrier such as a fronting tidal marsh.
The nutrient-poor environment and acidic soils
support a unique mix of vegetation species,
including both freshwater tidal species and
northern bog species, in sea level fens.84 Red
maple, blackgum, sweetbay, and southern
bayberry form the overstory; the herb layer
typically includes twig rushes, beaked
spikerushes, and beakrushes. Carnivorous plants,
including sundew and bladderworts, are also
present.85 The eastern mud turtle and the smallest
northeastern dragonfly (Ncmothemis bella) are
two faunal species known to occur in the fens.86
The animal and plant species listed here are not
exclusive to sea level fens, but many are rare
species.
Effect of Sea Level Rise on Sea Level
Fens
Because these fens are located at the bases of
slopes, they are likely to be inundated by sea
level rise. The Virginia Natural Heritage
Program identifies sea level rise as a primary
threat to sea level fens because of the increase in
82For additional discussion, see Sections 3.8, Maryland and
Delaware Coastal Bays; 3.3, Long Island's South Shore; and
3.19, Virginia's Eastern Shore.
83Virginia Natural Heritage Program, Virginia Department of
Conservation and Recreation. Natural Heritage Resources Fact
Sheet: Virginia's rare natural environments: Sea-level fens.
Accessed on July 17,2007 at:
http://www.dcr.virginia.gOv/natural_heritage/documents/fsslfen.p
df.
84Ibid.
85Fleming et al., 2006 (see note 67).
8oVirginia Natural Heritage Program (see note 83).
salinity and nutrient-rich water inputs.87 The
location of fens below slopes limits the
possibility for migration. During the
development of this report, no studies of the
effects of armoring on sea level fens were
identified.
Ecological Effects on Sea Level Fens
The unique vegetation assemblages and little-
studied animal communities of sea level fens are
likely to be eliminated by sea level rise. The
plant assemblages are unique, but the animal
species identified are present in other habitats.
The habitat is likely to convert to more usual
tidal marsh vegetation and faunal assemblages
following the increased incursion of higher
salinity waters. However, given the slopes at the
landward edges of the fens, migration will be
restricted and survival of any marsh areas will
depend on accretion rates.
3.1.5 NEARSHORE WATERS AND
SUBMERGED AQUATIC VEGETATION
(SAV)
Nearshore shallow water habitats perform a
variety of roles in the aquatic ecosystem. Key
ecological features of the nearshore shallow
water habitat include SAV, oyster reefs, and
nektonic (e.g., fish and decapod crustaceans) and
planktonic inhabitants. In areas without SAV or
oyster reefs, muddy and sandy substrates similar
to those found on tidal flats are present.88 Oyster
reefs are a key resource in intertidal and
nearshore waters; however, they are not
addressed in detail here because many factors
currently affect their success. Over harvest,
nutrient levels, and disease have all significantly
affected oyster reefs.. Changes related to sea
level rise may additionally affect the resource.
For example, if salinity were to increase, oysters
might be able to successfully colonize farther up
estuaries, but in their current areas they would
suffer greater losses from predators and disease.
These possibilities, though, are difficult to
estimate in the presence of annual variability.
This section therefore focuses on SAV, which
provides a wide array of ecological services and
87Fleming et al., 2006 (see note 67).
88Lippson and Lippson, 2006, pp. 126-127 (see note 2).
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[ SECTION 3.1 201 ]
is very sensitive to water depth and substrate.
SAV includes submerged, vascular rooted plants
found in the subtidal and, occasionally, in the
intertidal zone.89 SAV can occur as isolated
patches or form extensive beds. Aquatic
vegetation is distributed throughout the mid-
Atlantic region, dominated by eelgrass in the
higher salinity areas and a large number of
brackish and freshwater species elsewhere (e.g.,
widgeon grass and sea lettuce). During low tides,
SAV can be exposed on estuarine beaches and
tidal flats.9"
Nearshore vegetation plays a strong role in
estuarine and bay ecology, regulating dissolved
oxygen, reducing suspended sediments and
nutrients, stabilizing bottom sediments, and
reducing wave energy.91 SAV communities
regulate the production, uptake, and storage of
nitrogen, carbon, and oxygen in the ecosystem.92
Optimum growing conditions for SAV are highly
dependent on light levels for photosynthesis.
Various interferences—such as increased
turbidity, epiphyte growth on leaves, and
increased water depth—can decrease the light
available to the plants for photosynthesis. Plants
at either end of the growing zone are stressed by
overexposure or sunlight limits. Nutrient runoff
(which boosts algal growth that shades the SAV)
as well as boating and mollusk dredging (which
cause physical disturbance to the beds) can all
have detrimental effects on SAV.93
89Hurley, L.M., 1990, Field Guide to the Submerged Aquatic-
Vegetation of Chesapeake Bay, U.S. Fish and Wildlife Service,
Chesapeake Bay Estuary Program, Annapolis, MD, 48 pp.
9"Maryland DNR, 2005^ pp. 22-23 (see note 53).
91Short, F.T., and H.A. Neckles, 1999, "The effects of global
climate change on seagrasses.'\4<7fwft'c Botanv 63(1999): 169-
19<5.
92Buzzelli, C.P., 1998, "Dynamic simulation of littoral zone
habitats in lower Chesapeake Bay. I. Ecosystem characterization
related to model development," Estuaries 2l(48):659-672;
Buzzelli, C.P., R.L. Wetzel, andM.B. Meyers, 1998, "Dynamic
simulation of littoral zone habitats in lower Chesapeake Bay. II.
Seagrass habitat primary production and water quality
relationships," Estuaries 21(48):673-689.
93Orth, R.J., J.R. Fishman, A. Tillman, S. Everett, and K.A.
Moore, 2001, Boat Scarring Effects on Submerged Aquatic
Vegetation in Virginia (Year 1), Final Report to the Virginia
Saltwater Recreational Fishing Development Fund; Moore, K.A.,
and R.J. Orth. 1997, Evidence of Widespread Destruction of
Submersed Aquatic Vegetation (SAV) from Clam Dredging in
Chincoteague Bay, Virginia, Report to the Virginia Marine
Resources Commission. Both reports are available from VIMS
at: http://www.vims.edu/bio/sav/savreports.html (Accessed
October 16, 2007).
Except for a high predominance of sea lettuce in
New York's Jamaica Bay and the subtidal
reaches stretching from Little Egg Harbor south
to Cape May in New Jersey, the more northerly
SAV beds are largely eelgrass. Research in New
Jersey's coastal bays found a reduced habitat
quality of SAV in areas dominated by sea
lettuce.94
Seagrasses (e.g., eelgrass and widgeon grass)
provide food and shelter for a variety of fish and
shellfish, food for the species that prey on them,
and physical protection from wave energy for
shorelines. Organisms that forage in seagrass
beds feed on the plants themselves, on the
detritus and the epiphytes on plant leaves, or on
the small organisms found within the SAV bed.95
Invertebrates that are common in eelgrass
meadows include polychaetes such as the
common clam worm; mollusks such as bay
scallop and northern quahog; crustaceans such as
blue crabs, hermit crabs, and mud crabs; and
amphipods such as Lysianopsis alba and the
small, shrimp-like Ampelisca abdita. The
commercially valuable blue crab hides in
eelgrass during its molting periods, when it is
more vulnerable to predation. Blue crabs in the
postlarval phase (megalopae) preferentially
inhabit eelgrass beds.96
These invertebrates are in turn consumed by fish
and other predators.97'98 In Chesapeake Bay,
summering sea turtles frequent eelgrass beds.
The endangered Kemp's Ridley sea turtle
forages in eelgrass beds and flats, feeding on
94Sogard, S.M., and K.W. Able, 1991, "A comparison of eelgrass,
sea lettuce macroalgae, and marsh creeks as habitats for
epibenthic fishes and decapods," Estuarine, Coastal and Shelf
Science 33:501-519.
95For blue crabs, see Stockhausen, W.T., and R.N. Lipcius, 2003,
"Simulated effects of seagrass loss and restoration on settlement
and recruitment of blue crab postlarvae and juveniles in the York
River, Chesapeake Bay "Bulletin of Marine Science 72(2):409-
422. For fish, see Wyda, J.C., L.A. Deegan, J.E. Hughes, and
M.J. Weaver, 2002, "The response of fishes to submerged aquatic
vegetation complexity in two ecoregions of the mid-Atlantic
Bight: Buzzards Bay and Chesapeake Bay "Estuaries 25:86-
100.
9ovan Montfrans, J., C.H. Ryer, and R.J. Orth, 2003, "Substrate
selection by blue crab Callinectes sapidus megalopae and first
juvenile instars," Marine Ecology Progress Series 260:209-217.
97USEPA, 1982, Chesapeake Bav: Introduction to an Ecosvstem,
USEPA, Washington, DC,, 33 pp.
98Lippson and Lippson, 2006, p. 181 (see note 2).
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[ 202 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
blue crabs in particular." Various water birds
feed on SAV, including brant, canvas back duck,
and American black duck, which is a U.S. Fish
and Wildlife Service species of concern.1""
Forage for piscivorous birds and fish is provided
by a number of small fishes that are residents of
nearby marshes and move in and out of seagrass
beds with the tides, including mummichog,
Atlantic silverside, naked goby, northern
pipefish, and threespine and fourspine
sticklebacks. Juveniles of many commercially
and recreationally important estuarine and
marine fishes (including menhaden, herring,
shad, spot, croaker, weakfish, red drum, striped
bass, and white perch) and smaller adult fish
(such as bay and striped anchovies) use SAV
beds as nurseries that provide both food and
protection from predators.1"1 Adults of estuarine
and marine species such as sea trout, bluefish,
perch, pickerel, and drum search for prey in the
SAV beds.
Effect of Sea Level Rise on Nearshore
Waters and SAV
Sea level rise may harm seagrass beds through
inundation, increased turbidity, and saltwater
intrusion.1"2 In subtidal areas, rising sea levels
and deepening waters will shade seagrass and
limit photosynthesis. Extensive armoring
coupled with areas of limited natural migration
could significantly decrease seagrass abundance.
Although plants in some portion of a seagrass
bed could decline as a result of such factors,
landward edges may migrate inland depending
on shoreline slope and substrate suitability. The
extent of ecological effects is uncertain because
most changes in seagrass beds occur on a
"Chesapeake Bay Program sea turtles guide, 2003, available at:
http://www.chesapeakebay.net/seaturtle.htm, accessed February
27,2007.
100Perry, M.C. and A.S. Deller, 1996, "Review of factors
affecting the distribution and abundance of waterfowl in shallow-
water habitats of Chesapeake Bay," Estuaries 19:272-278.
101NOAA Chesapeake Bay Office, 2007, "Underwater grasses
and submerged aquatic vegetation," accessed June 19, 2007 at:
http://noaa.chesapeakebay.net/HabitatSav.aspx; Wyda et al.,
2002, pp. 86-100 (see note 95).
102Short andNeckles, 1999, pp. 169-196 (see note 91).
significantly shorter time scale than can be
attributed to sea level rise.1"3
Under optimal conditions, seagrasses could
migrate into deteriorating marshes. For example,
populations of widgeon grass were observed in
marsh potholes that developed as canals formed
through organic marsh deposits.1"4 Kentula and
Mclntire documented eelgrass expansion into a
basin created by sand deposition.1"5 Preliminary
studies of eelgrass in marsh areas being
inundated by relative sea level rise have,
however, shown that the sediment composition
of the low marsh areas may not be suitable for
eelgrass colonization. In areas where inundation
exposed underlying sand, eelgrass beds extended
into the areas, but areas of exposed peat were not
colonized. The difficulty in colonization was tied
to the impermeability of the substrate
(prohibiting seed settlement and germination)
and the high levels of nutrients in the sediment,
particularly nitrogen. These factors changed the
morphology of the eelgrass, making it less suited
to the energy level of its environment.1"6 Unlike
most wetland plants, seagrasses generally require
a low organic content for optimal growth.1"7
When tidal marshes, which have a high organic
content, are submerged, SAV such as Ruppia
maritima can have difficulty revegetating the
substrate. SAV grows significantly better in
areas where erosion provides sandy substrates
rather than fine-grained or high-organic-matter
substrates.1"8
103USFWS Chesapeake Bay Field Office, n.d., "Nutrient
pollution," accessed on July 20, 2006 at:
http://www.fws.gov/chesapeakebay/nutrient.htm.
104Christian, R.R., 1981, referenced in Brinson et al. 1995, p. 654
(see note 23).
105Kentula, M.E., and C.D. Mclntire, 1986, "The autecology and
production dynamics of eelgrass (L. Zostera marina) in Netarts
Bay, Oregon," Estuaries 9(3): 188-193.
10oWicks, E.C., 2005, The Effect of Sea Level Rise on Sea
Grasses: Is Sediment Adjacent to Retreating Marshes Suitable for
Seagrass Growth? Thesis, Marine, Estuarine, and Environmental
Science Program, University of Maryland, College Park; and
preliminary research by Koch.
107Kemp, W.M., R. Batuik, R. Bartleson, P. Bergstrom, V. Carter,
G. Gallegos, W. Elunley, L. Karrh, E. Koch, J. Landwehr, K.
Moore, L. Murray, M. Naylor, N. Rybicki, J.C. Stevenson, and
D. Wilcox, 2004, "Elabitat requirements for submerged aquatic
vegetation in Chesapeake Bay: Water quality, light regime, and
physical-chemical factors," Estuaries 27:363-377.
108Stevenson et al. 2002, pp. 26, 32 (see note 7).
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[ SECTION 3.1 203 ]
The effect of sea level rise on the tidal range will
also have an impact on seagrass, although it may
be detrimental or beneficial. In areas where the
tidal range increases, plants at the lower edge of
the bed will receive less light at high tide, which
will increase plant stress.1"9 In areas where the
tidal range decreases, the decrease in intertidal
exposure at low tide on the upper edge of the bed
will reduce plant stress.11"
Effects of Armoring on Nearshore Waters
and SAV
Areas of shoreline armoring are likely to
experience the biggest losses of seagrass.
Movement of seagrass beds shoreward will be
impeded by shoreline construction and armoring
in developed areas.111 Where inland migration is
not possible, seagrass will decline or be
eliminated as a result of inundation and increased
salinity as seas rise. Nearshore fishes have been
found to be significantly less abundant at
bulkheaded sites, in part because seagrass is not
present.112 Bulkheads and other hard structures
tend to affect the geomorphology of their
locations as well as any adjacent seagrass
habitats. Particularly during storm events, wave
reflection off of revetments can increase water
depth and magnify swash runup on downcoast
beaches.113 AUSGS sedimentation study notes
that these structures tend to increase erosion at
their bases by reflecting wave energy across the
nearshore bottom.114 Similarly, a study of
armoring in estuaries found that "wave energy
reflected from bulkheads causes an increase in
turbulence and erosional energy waterward of
the structure that can result in substrate
coarsening and lowering of the beach profile."115
These physical changes in turn affect the
habitats.
109Koch and Beer, 1996, referenced in Short and Neckles, 1999,
p. 179 (see note 91).
110Short and Neckles, 1999, pp. 179-180 (see note 91).
1 "Short and Neckles, 1999, p. 178 (see note 91).
112Byme, D.M., 1995, "The effect of bulkheads on estuarine
fauna: a comparison of littoral fish and macroinvertebrate
assemblages at bulkheaded and non-bulkheaded shorelines in a
Bamegat Bay Lagoon," Second Annual Marine Estuarine
Shallow Water Science and Management Conference: 53-56.
113Plant, N.G. and G.B. Griggs, 1992, "Interactions between
nearshore processes and beach morphology near a seawall."
Journal of Coastal Research 8: 183-200, p. 190.
114USGS, 2003, p. 50 (see note 48).
115Small and Carman, 2005, p. 1 (see note 49).
As sea level rises in armored areas, accompanied
by erosional energy at the bottom, the nearshore
area deepens with no ability to migrate. In
addition to the effects of increased reflectional
wave energy, which can be dissipated to a large
degree by healthy seagrass communities, light
attenuation increases with the deepening water,
restricting and finally eliminating seagrass
growth. Optimum growing conditions for most
SAV require light levels typically found at up to
1 to 2 meters in depth, generally starting below
the mean lower low watermark.116 Light
reductions from water clarity and epiphyte
growth in most SAV beds are now at 1 meter or
less in depth.117
In addition to the effects of light quantity and
turbulence, high nutrient levels in the water are
also a limiting factor. Despite the protection
from wave energy provided in their interior,
breakwaters appear to be detrimental to seagrass
in the long term. Sediment trapping behind the
breakwater, which increases the organic content,
can limit eelgrass success. Low-profile armoring,
including stone sills and other "living shoreline"
projects, have a more limited impact on seagrass
growth.118 New designs for seagrass-friendly
breakwaters that allow rollover at high tide might
serve to flush out the interior of the breakwater
and eliminate excess nutrient buildup.119
Ecological Effects on Nearshore Waters
and SAV
The extent of ecological effects is uncertain,
because most changes in SAV beds occur on a
significantly shorter time scale than can be
attributed to sea level rise.12" Some species of
seagrass could survive the effects of sea level
ll0Kemp et al., 2004 (see note 107).
117Orth, R.J., and K.A. Moore, 1984, "Distribution and
abundance of submerged aquatic vegetation in Chesapeake Bay:
An historical perspective," Estuaries 7:531-540; Kemp et al.,
2004, p. 365 (see note 107).
118See, for example, National Academy of Sciences, 2006,
Mitigating Shore Erosion along Sheltered Shores, The National
Academies Press. Washington, DC, pp. 46, 57.
119Koch, E.W., L.P. Sanford, S.-N. Chen, D..T. Shafer, and J.M.
Smith, 2006, Waves in Seagrass Systems: Review and Technical
Recommendations. Final Report prepared for the U.S. Army
Corps of Engineers, System-Wide Water Resources Research
Program and Submerged Aquatic Vegetation Restoration
Research Program, ERDC TR-06-15, p. 16.
120USFWS, n.d., Nutrient pollution (see note 103).
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[ 204 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
rise by expanding inland. Submerged vegetation
cannot grow and survive, however, where
increased water depth or increased turbidity
severely restrict the amount of light available for
photosynthesis. Short and Neckles estimate that,
in general, a 50 cm increase in water depth as a
result of sea level rise could reduce the available
light in coastal areas by 50 percent, reducing
seagrass growth in current bed areas by 30 to 40
percent.121 Such reductions in seagrass could
have a significant effect on the many fauna
found in seagrass beds. For example, research
indicates that the abundance, biomass, and
diversity of fishes are higher near seagrass beds
than in unvegetated areas.122
In areas where seagrass is lost, the primary
productivity, the habitat provided to key species,
and the shoreline protection benefits will all be
affected.123 The extent of primary productivity
impact is unknown; autotrophs like
phytoplankton and sediment microalgae are
generally not considered capable of providing
the extent of primary production contributed by
SAV.124 In Chesapeake Bay, the microbenthic
algal community comprises between 3 and 5
percent of the total annual primary production
from all sources.125 Vegetation also increases the
dissolved oxygen content of the water; low
dissolved oxygen in summer (common in many
Atlantic waterways) is a major stressor on biota
such as the blue crab, Atlantic sturgeon, and
striped bass.126 Wrack from submerged aquatic
121Short and Neckles, 1999, p. 178 (see note 91).
122Wyda et al., 2002, pp. 86-100 (see note 95).
123Duarte, C.M., 2002, "The future of seagrass meadows,"
Environmental Conservation 29(2): 192-206.
124Borum, 1996, in Duarte, 2002, p. 199 (see note 123); reviewed
in Buzzelli 1998, p. 659 (see note 92).
125Wendker, S., H.G. Marshall, andK.K. Nesius, 1997, "Benthic
primary production within shallow water sites in Chesapeake
Bay," pp. 148-151 in Proceedings of the Second Marine and
Estuarine Shallow Water Science and Management Conference,
U.S. Environmental Protection Agency, Philadelphia, PA, EPA
903/R/97009, USEPA, Washington, DC.
12oFor blue crabs, see Mistiaen, J.A., I.E. Strand, and D. Lipton,
2003, "Effects of environmental stress on blue crab (Callinectes
sapidus) harvests in Chesapeake Bay tributaries," Estuaries
26(2A): 316-322. For Atlantic sturgeon, see Niklitschek, E.J., and
D.H. Secor, 2005, "Modeling spatial and temporal variation of
suitable nursery habitats for Atlantic sturgeon in the Chesapeake
BayEstuarine, Coastal, and Shelf Science 64(2005): 135-148.
For striped bass, see Coutant, C.C., and D.L. Benson, 1990,
"Summer habitat suitability for striped bass in Chesapeake Bay:
Reflections on a population decline," Transactions of the
American Fisheries Society 119:757-778.
vegetation also plays an important role in beach
communities, providing cover and food to a
variety of amphipods, isopods, and insects,
which are in turn fed on by shorebirds such as
plovers.127
Loss of SAV affects the large number of species
that depend on the vegetation beds for protection
and food. As noted previously, blue crabs are
particularly dependent on seagrass beds,
although some types of shoreline structures (e.g.,
riprap and jetties) can provide similar protective
cover to juvenile crabs.128 By one estimate, a 50
percent reduction in SAV results in a roughly 25
percent reduction in striped bass production.129
Fish abundance and species richness are also
affected by degradation of SAV habitat. A
decline in SAV also affects larger predators,
including shorebirds and sea turtles. Birds that
are primarily herbivorous are directly affected by
the loss of SAV. For diving and dabbling ducks,
researchers have noted a decrease in SAV in
their diets since the 1960s. With the decline of
SAV, the diet of geese and swans has shifted to
agricultural field wastes. For canvasback ducks,
SAV consumption has been replaced by a diet
high in invertebrates and crustaceans. Such diet
shifts have not been possible for all SAV-reliant
species. The decreased SAV in Chesapeake Bay
is cited as a major factor in the substantial
reduction in wintering waterfowl such as redhead
ducks.130
3.1.6 TIDAL FLATS
Tidal flats are found in the intertidal zone. They
have muddy substrates, typically composed of
silt and clay, that support sparse or no
vegetation. In brackish area flats, vegetation is
rare, consisting of occasional clumps of
127Dugan, J.E., D.M. Elubbard, M.D. McCrary, and M.O. Pierson,
2003, "The response of macrofauna communities and shorebirds
to macrophyte wrack subsidies on exposed sandy beaches of
southern California," Estuarine, Coastal and Shelf Science
58S:25^10.
128Maryland Sea Grant, 2001, p. 10 in Research Needs for
Sustainable Blue Crab Production in Maryland, A Workshop
Report, publication number UM-SG-TS-2001-01, prepared by
Maryland Sea Grant College, College Park.
129Kahn, J.R., and W.M. Kemp, 1985, "Economic losses
associated with the degradation of an ecosystem: The case of
submerged aquatic vegetation in Chesapeake Bay," Journal of
Environmental Economics and Management 12:246-263.
130Perry and Deller, 1996, p. 273, 276 (see note 100).
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[ SECTION 3.1 205 ]
saltmarsh cordgrass.
Freshwater flats,
common in Chesapeake
Bay tributaries, can
support herbaceous
species. Tidal flats are
critical foraging areas
for numerous birds,
including wading birds,
migrating shorebirds,
and dabbling ducks
such as mallards and
the American black
duck.
Effects of Sea Level
Rise on Tidal Flats
In areas with low
sediment supplies,
marsh will revert to
unvegetated flats and
eventually to open
water.131 For example, in New York's Jamaica
Bay, several hundred acres of low salt marsh
have converted to open shoals (see Section 3.4).
Except in high-sediment supply areas and in
locations where migration is possible, tidal flats
will gradually become inundated as sea levels
rise.
Effects of Armoring on Tidal Flats
In areas where sediments accumulate in shallow
waters and shoreline protection prevents
landward migration of salt marshes, flats could
become vegetated as low marsh encroaches
waterward, accelerating sediment deposition at
the waterward edge of the vegetated area and
leading to an increase in low marsh at the
expense of tidal flats.132 If sediment inputs are
insufficient, tidal flats will convert to subtidal
habitats.
Photo 3.5: Estuarine beach and bulkhead along Arthur Kills, New Jersey
Shorebirds feed on all trophic levels of beach
invertebrate communities, including primary
consumers (herbivorous insects, amphipods, and
isopods as well as suspension-feeding crabs and
bivalves) and the secondary consumers that feed
on them (crabs, isopods, polychaetes, and
beetles).133 As tidal flat area declines, increased
crowding in remaining areas will lead to
exclusion and mortality of many shorebirds.134 In
some cases, reversion of Spar una marsh to
unvegetated flats could benefit foraging by
wading birds and dabbling ducks. As the flats
become more deeply inundated, however, they
will become unavailable to short-legged
shorebirds.131 Modeling by Galbraith and
colleagues predicted that under a 2°C global
warming scenario,
sea level rise could inundate significant areas of
intertidal flats in some regions.136 Although this
may initially lead only to crowding of remaining
Ecological Effects on Tidal Flats
Loss of tidal flats would eliminate a rich
invertebrate food source for migrating birds.
131Brinson et al. 1995, p. 650 (see note 23),
132Redfield, A.C., 1972, "Development of a New England salt
marsh," Ecological Monographs 42:201-237.
133See, for example, M.D. Bertness, 1999, Chapter 6, "Soft
sediment habitats," pp. 249-312 in The Ecology of Atlantic
Shorelines, Sinauer Associates, Inc., Sunderland, MA.
134Galbraith et al., 2002, p. 173 (see note 50).
135Erwin et al., 2004, p. 902 (see note 16); andErwin, R.W., n.d.,
Atlantic Sea Level Rise, Lagoonal Marsh Loss, and Wildlife
Habitat Implications. Accessed at:
http://www.pwrc.usgs.gov/reshow/erwinlrs/erwinlrs.htm on
March 16, 2006.
13oGalbraith et al., 2002, p. 178 (see note 50).
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[ 206 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
tidal flat forage areas, Galbraith and
coinvestigators further noted that increased
crowding will lead to the exclusion and mortality
of shorebirds.137 Ponds within marshes might
become more important foraging sites for these
birds as mudflats are inundated by sea level
138
rise.
3.1.7 ESTUARINE BEACHES
Estuarine beaches are unconsolidated sandy
shores that are inundated by the tidal cycle.
Throughout most of the mid-Atlantic region and
its tributaries, these beaches front the base of low
bluffs and high cliffs as well as bulkheads and
revetments. The beaches are characterized by
steep foreshores and broad, flat, low tide terraces
(see Photo 3.5).139 Beaches can also occur in
front of marshes, sometimes retreating back over
them through storm-driven overwash processes.
Plants are typically sparse in beach areas,
surviving only above the high tide line with
adaptations for the harsh beach environment,
such as waxy leaves or strong root systems. In
Chesapeake Bay, such plant species include
seabeach and marsh orach (Atriplex cristata), sea
rocket (Cakile edentula), Russian thistle (Salsola
kali), and seablite.14"
The most abundant beach organisms are
microscopic invertebrates (meiofauna) that live
between sand grains, feeding on bacteria and
single-celled protozoans. It is estimated that
more than 2 billion of these organisms can be
found in a single square meter of sand.141 The
meiofauna play a critical role in beach food webs
as a link between bacteria and larger consumers.
The most conspicuous invertebrates of beaches
are the macroinvertebrates that burrow in
sediments or hide under rocks. These include
hermit crabs, beach fleas, worms, beach
amphipods, bivalves, and snails. Various rare
and endangered beetles also live on sandy
shores. Diamondback terrapins and horseshoe
137Galbraith et al., 2002, p. 173 (see note 50).
138Erwin et al., 2004, p. 902 (see note 16).
139Jackson, N.L., K.F. Nordstrom, and D.R. Smith, 2002,
"Geomorphic-biotic interactions on beach foreshores in
estuaries," Journal of Coastal Research Special Issue 36:414-
424.
140Lippson and Lippson, 2006, p. 28 (see note 2).
141Bertness, 1999, 256-257 (see note 133).
crabs bury their eggs in beach sands. Piping
plover (federally listed as threatened), American
oystercatcher, and sandpipers feed on beetles,
larvae, marine worms, mollusks, and other
insects and crustaceans, as well as on horseshoe
crab eggs.142 In mid-Atlantic bays, particularly
Delaware Bay and southern Chesapeake Bay,
horseshoe crabs rely on estuarine beaches for
spawning during high spring tides.143 Migrating
shorebirds and resident gulls and terns feed on
the horseshoe crab eggs. The diamondback
terrapin nests in sandy areas above the high tide
mark and may hibernate along embankments on
muddier shorelines.144
Eggs of species that nest on estuarine beaches
and invertebrate infauna provide forage for
numerous bird species, including migratory
shorebirds and species that nest on nearby barrier
islands, such as the piping plover (federally
listed as threatened). Shorebirds feed on all
trophic levels of beach invertebrate communities
(see Photo 3.6).145 The insects, isopods, and
amphipods found in wrack deposits on estuarine
beaches are also an important source of forage
for birds (see Photo 3.7).146 The abundance of
these organisms has been shown to be highest at
sites with greater wrack. In addition, the
abundance of shorebird species is positively
correlated with the abundance of wrack and
wrack-associated invertebrates.147
142USFWS, 1988, Endangered Species Information Booklet:
Piping Plover, USFWS, Arlington, VA.
143Lippson and Lippson, 2006, p. 32 (see note 2); Dove and
Nyman, 1995 (see note 14).
144Chesapeake Bay Program, 2006, Diamondback terrapin,
available at:
http://www.chesapeakebay.net/diamondback_terrapin.htm,
accessed .Time 13, 2006.
145Dugan et al., 2003, p. 26 (see note 127).
14oJackson et al., 2002 (see note 139).
147Dugan et al., 2003, pp. 32-33 (see note 127).
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[ SECTION 3.1 207 ]
Photo 3.6. Dinnertime along Peconic Estuary Beach, Long Island, New
York
overwash and dune
building, as exhibited by
barrier islands.148'149 The
general lack of vegetation
on the beaches, however,
frequently limits the
ability to retain sediment.
In front of shoreline
protection structures, or
where the land behind the
existing beach has too
little sand to sustain it,
beaches that are not
nourished will erode and
eventually drown as sea
level rises. If impediments
to migration exist or
natural sediment inputs
decline, beaches will be
lost. Through nourishment
efforts, society will
preserve many beaches at
risk of erosion. But in
many areas where homes
are built on the shoreline,
beach loss will be
inevitable.
; "
||g; .
Effects of Armoring
on Estuarine Beaches
ft.
Photo 3.7: Beach with beach wrack and marsh in New Jersey
Effects of Sea Level Rise on Estuarine
Beaches
As with vegetated tidal wetlands, the fate of
estuarine beaches depends on their ability to
migrate or on the presence of sufficient sediment
to allow accretion. Beaches can migrate through
marshes, generally through a process of
Many shoreline
protections interfere with
the survival of estuarine
beaches by both blocking
migration and affecting
sediment retention.
Because of the sediment
trapping effects of many
shore protections,
armoring that traps sand
in one area can limit or
eliminate longshore
transport. This, in turn,
diminishes the constant replenishment of sand
necessary for beach retention in nearby locations.
Areas with bulkheads frequently have artificially
148Jackson et al.. 2002, p. 418 (seenote 139).
149The overwash process is also observed on peninsulas (e.g., the
migration of Bethel Beach over marsh area in Mathews County,
Virginia). See Section 3.12, Chesapeake Bay's Middle Peninsula.
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[ 208 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
elevated land areas, or headlands, because not all
structures are built in a straight line. In areas
with sufficient sediment input relative to sea
level rise (e.g., upper tributaries and upper
Chesapeake Bay), accretion may keep beaches in
place in front of armoring.
In armored areas between headlands, the beach is
likely to become steeper and the sediments
coarser. Waterward of the bulkheaded headlands,
the foreshore habitat will be lost, often even
without sea level rise.15" If the areas between
these headlands are not armored, in most cases
sediment input will be reduced and inundation
will occur with rising sea level.
In many developed areas, estuarine beaches may
be maintained with beach nourishment, although
the ecological effects of nourishment remain
uncertain.151 Beach nourishment will allow
retention in areas with a sediment deficit, but
could reduce habitat value through effects on
sediment characteristics and beach slope.152
Some think that benthic organisms on the
shallow, low tide terrace of estuarine beaches are
less tolerant of burial as a result of beach
nourishment than organisms of the subtidal zone
of more energetic beaches.153 The viability of
horseshoe crab eggs depends on sediment
characteristics that promote drainage and
aeration, and therefore some coastal
geomorphologists predict that egg survival could
be low on beaches that are modified through
beach nourishment.154 On the other hand,
Delaware plans to nourish beaches that lie in
front of marsh for the purpose of preserving
horseshoe crab habitat.155
150 Jackson et al., 2002, p. 420 (see note 139).
151Peterson, C.H. and M..T. Bishop, 2005, "Assessing the
environmental impacts of beach nourishment,'" Bioscience
55:887-896.
152Peterson and Bishop, 2005 (see note 151).
153Nordstrom, K.F., 2005, "Beach nourishment and coastal
habitats: Research needs to improve compatibility," Restoration
Ecology 13:215-222, p. 217.
154 Jackson et al., 2002, p. 421 (see note 139).
155See, for example, Smith, D., N. Jackson, S. Love, K.
Nordstrom, R. Weber, and D. Carter, 2002, Beach Nourishment
on Delaware Shore Beaches to Restore Habitat for Horseshoe
Crab Spawning and Shorebird Foraging, prepared for The
Nature Conservancy, Delaware Bay shores Office, Wilmington,
DE, accessed on June 19, 2007 at:
http: //www. dnrec. state. de.us/fw/hcrabs/FINAL%20Beach%20Ha
bitat%20Restoration%20Report.pdf.
Ecological Effects on Estuarine Beaches
Where beaches are lost, the many invertebrates
that burrow in the sand and species that spawn
on beaches will lose critical habitat. Using high-
precision elevation data from nest sites,
researchers are beginning to carefully examine
the effects that sea level rise will have on
oystercatchers and other shore birds.156 To the
extent that estuarine and riverine beaches,
particularly on islands, survive better than barrier
islands, shorebirds like oystercatchers might be
able to migrate to these shores.157 Loss of beach
will also cause local elimination of beach-
dependent species such as the rare beetles found
in Calvert County, Maryland. Although the
northeastern beach tiger beetle is able to migrate
in response to changing conditions, suitable
beach habitat must be available nearby.158
The degree to which horseshoe crab populations
will decline as beaches are lost is currently
unclear. Early results of ongoing research funded
by New Jersey Sea Grant indicate that horseshoe
crabs also lay eggs in other intertidal habitats in
addition to estuarine beaches, such as sandbars
and the sandy banks of tidal creeks.159
Nonetheless, if these habitats are also inundated,
they will provide only temporary refuges for
horseshoe crabs.
Where horseshoe crabs decline because of loss of
suitable habitat for egg deposition, there can be
significant implications for migrating shorebirds,
particularly the red knot, which is a candidate for
the federal endangered species list. The red knot
feeds almost exclusively on horseshoe crab eggs,
and, to continue its migration, the bird nearly
doubles its weight by feeding on crab eggs.
Researchers from Virginia Tech and the New
''"Rounds, R. and R.M. Erwin, 2002, "Flooding and sea level rise
at waterbird colonies in Virginia," presented at Waterbird Society
Meeting, November 2002, accessed on June 19, 2007 at:
http://www.vcrlter.virginia.edu/presentations/rounds0211/rounds
0211.pdf.
157McGowan et al., 2005, p. 150 (see note 81).
158USFWS, 1994, Recovery Plan for the Northeastern Beach
Tiger Beetle (Cicindela dorsalis dorsalis), USFWS, Hadley, MA.
159Research by Dr. Mark Botton of Fordham College and Dr. Bob
Loveland of Rutgers University, funded by New Jersey Sea
Grant; summarized online and accessed on June 19, 2007 at:
http://www.njmsc.org/Sea_Grant/Research_News/The_Importan
ce_Of_Marginal_and_Restored_Habitats.htm.
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[ SECTION 3.1 209 ]
Jersey Division of Fish and Wildlife report that
the number of horseshoe crab eggs is the most
important factor determining the use of mid-
Atlantic back-barrier beaches by red knots, and
documented a reduction in the number of red
knots throughout the Delaware Bay correlated
with a decline in horseshoe crabs (see also
Section 3.9 on Maryland and Delaware Coastal
Bays.160
3.1.8 CLIFFS
Cliffs and the sandy beaches sometimes present
at their bases are constantly reworked by wave
action, providing a dynamic habitat for cliff
beetles and birds. Little vegetation exists on the
cliff face because of constant erosion. Eroding
sediment augments nearby beaches. Cliffs are
present on Chesapeake Bay's western shore and
tributaries and its northern tributaries (see Photo
3.8), as well as in Hempstead Harbor on Long
Island's North Shore.
Erosion is driven by two key processes:
freeze/thaw and wave undercutting. Recession
rates for cliffs are higher in areas where
undercutting is the dominant erosion method; for
example, Wilcock and coworkers reported
historical erosion rates between 0.3 and 1 ft/yr
for freeze/thaw areas of Maryland's Calvert
Cliffs and rates between 2 and 3 ft/yr for wave
undercut areas.161 On the Sassafras, near its
entrance at the north end of Chesapeake Bay, the
cliffs are receding at rates of 0.9 to 1.4 ft/yr.162
Areas dominated by the freeze/thaw mechanism
frequently have beaches at their base (a higher
toe elevation) that protect the bottom of the slope
from wave energy.163
Effect of Sea Level Rise on Cliffs
Sea level rise may increase rates of cliff erosion
by decreasing the toe elevation, but ecological
impacts of such an increase in erosion rate are
uncertain. If erosion rates are too high, sudden
losses of the cliff face can endanger species that
depend on unvegetated cliffs (e.g., Puritan tiger
beetles). The armoring that is in place, or that
might be increased in response to accelerated sea
level rise, poses more evident threats to the cliff
ecology.
lo0Karpanty, S., J. Fraser, J. Berkson, L. Niles, A. Dey, and E.
Smith, 2006, "Horseshoe crab eggs determine red knot
distribution in Delaware Bay habitats," Journal of Wildlife
Management, 70:1704-1710.
161Wilcock, P.R., D.S. Miller, R.H. Shea, andR.T. Kerhin, 1998,
"Frequency of effective wave activity and the recession of coastal
bluffs: Calvert Cliffs, Maryland," Journal of Coastal Research
14(1 ):256—268.
lo2Maryland DNR, 2002, Sassafras Natural Resources
Management Area Land Unit Plan, Maryland DNR Resource
Planning Program, accessed on June 19, 2007 at
http://www.dnr.state.md.us/resourceplanning/sassafras.pdf.
lo3Toe elevation is the height of the beach before the bluff/cliff
begins.
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[ 210 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Photo 3.8. Emerald Beach along the Elk River in Maryland
Effects of Armoring on Cliffs
Cliffs and headlands could experience increased
erosion rates resulting from disruption in
longshore sediment transport as a result of
nearby sediment-trapping shoreline protections
(e.g., groinfields).164 Alternatively, if the cliff
base is armored, the erosion rates could decrease.
Either outcome could eliminate habitat for
endangered species that depend on varying rates
of erosion. According to the Maryland
Department of Natural Resource's wildlife
diversity conservation plan, naturally eroding
cliffs are "severely threatened by shoreline
erosion control practices."1,65 Because of the
sediment-trapping effects of many types of shore
protection, armoring in one area can diminish the
constant replenishment of sand necessary for
beach retention in nearby locations. Introducing
shoreline protections can subject adjacent cliff
areas to wave undercutting and higher recession
rates. Development and shoreline stabilization
structures that interfere with natural erosional
processes are cited as threats to bank-nesting
birds (e.g., bank swallows and belted
kingfishers) as well as two species of tiger
beetles (federally listed as threatened) at
Maryland's Calvert Cliffs.1®'167The majority of
the identified Puritan tiger beetles live in the
Calvert Cliffs, particularly in Calvert Cliffs State
Park on Chesapeake Bay's western shore.
lo4Wilcock et aL, 1998, p. 259 (see note 161).
^Maryland DNR, 2005, p. 13 (see note 53).
I 'SI W S. 1993, Puritan Tiger Beetle (Cicindela pnritcma G,
Horn) Recovery Plan, Hadley, MA; USFWS, 1994 (see note
158).
lo7The Center for Conservation Biology at William & Mary,
1996, "Fieldwork concluded on bank-nesting bird study," in
Cornerstone Magazine, accessed on .Time 21, 2006, at
https://www.denix.osd.mil/denix/Public/ES-
Programs/Conservation/Legacy/Cornerstone/corner.html.
-------
3.2 North Shore, Long Island Sound and
Peconic Estuary Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats along Long Island Sound
are potentially at risk because of sea level rise.
This brief literature review considers this risk for
the New York portion of Long Island Sound
(hereafter the Sound), including the shorelines of
Westchester, Bronx, Nassau, and Suffolk
counties as well as the Peconic Estuary at the far
eastern end of Long Island. These Long Island
shorelines contain important habitats for a
variety of fish, shellfish, and birds, and a great
deal is known about their ecology and habitat
needs (see Map 3.1). Based on existing literature
and the knowledge of local scientists, this review
discusses the coastal species in areas that could
be at risk because of further habitat loss resulting
from sea level rise and shoreline protection.
There are locations in the study area with
naturally steep shorelines that will interfere to
varying degrees with marine transgression of
tidal wetlands in response to rising seas.
Although it is possible to make qualitative
statements about the possible impacts if sea level
rise causes a total loss of habitat, our ability to
discern what the impact might be if only a
portion of the habitat is lost is more limited.168
168EPA's ambitious goal for these reviews would have had us
address the four possible outcomes resulting from different rates
of sea level rise (or wetland accretion) and whether shores are
protected. In a typical case where area of wetlands is 5 times the
area of land that might become new wetlands as sea level rises,
the four possible outcomes are:
a. Existing wetlands are lost, shore protection prevents new
wetlands forming inland (100% loss).
b. Existing wetlands keep pace, shore protection prevents new
wetlands forming inland (no change, in total acreage, but possible
loss of plants that inhabit the upper portion of the tide range).
c. Existing wetlands lost, no shore protection allows wetlands to
form inland (80% loss).
d. Existing wetlands keep pace, no shore protection allows
wetlands to form inland (20% gain).
We focus on the implication of case a, because the implication of
a total loss of habitat is understood at least qualitatively. The
literature is often insufficient for us to distinguish whether case c
is more similar to "no impact" or to the total loss implied by case
a, and hence, depending on context, the prose that follows may
imply either that such large scale loss is similar to total loss, or
TIDAL MARSH
In 2003, the Long Island Sound Habitat
Restoration Initiative reported that there were
8,425.6 ha (20,820 acres) of tidal wetlands in the
Sound, including all tidal wetland types, with 85
percent of the total in Connecticut.169 Most of the
remaining 15 percent of tidal wetlands found in
the New York State portion of the Sound are
along the shores of Westchester and Bronx
counties.17" In Westchester County, ecologically
important tidal wetlands occur in the county-
owned Marshlands Conservancy property.171 The
Marshlands Conservancy site is the only
mainland breeding area for yellow-crowned
night herons in the region.172
Tidal wetlands are also uncommon along the
north shore of Long Island because of the steep
uplands and sea cliffs created by the terminal
moraine of glaciers, and therefore wetlands are
that because some wetlands will continue to survive, that the
impact is similar to "no impact." In the case of beaches and
possibly mudflats, the absence of shore protection generally
allows the system to survive. We did not examine cases b or d at
all.
lo9Holst, L, R. Rozsa, L. Benoit, S. Jacobsen, and C. Rilling,
2003, Long Island Sound Habitat Restoration Initiative,
Technical Support for Habitat Restoration, Section 1: Tidal
Wetlands. EPA Long Island Sound Office, Stamford, CT, p. 1-7,
Available at:
http://www.longislandsoundstudy.net/liabitat/index.hhn; and
Rosza, R., 1995, "Human impacts on tidal wetlands: History and
regulations, Chapter 2 in G.D. Dyer and W.A. Neiring, eds.,
Tidal Marshes of Long Island Sound, Ecology History and
Restoration, The Connecticut College Arboretum, Bulletin No.
34, December. Available at:
http://arboretum.conncoll.edu/publications/34/FRAME.HTM.
170Holst et al., 2003, p. 1-1 (see note 169).
1 71
New York State (NYS) Department of State, Division of
Coastal Resources, 2004, Significant Coastal Fish and Wildlife
Habitats. Long Island Sound and Long Island, Marshlands
Conservancy. Coastal Resources Online. Available at
http://nvswaterfronts.com/waterfront natural narratives.asp.
172USFWS, 1997, Significant Habitat and Habitat Complexes of
the New York Bight Watershed. USFWS, South New England,
New York Bight Coastal Ecosystems Program, Charlestown, RI;
The Narrows, Complex #20, pp. 611-619.
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[ 212 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
largely confined to former drowned "kettle hole"
embayments such as Mount Sinai.173 There are
some notable areas of marsh in and around Stony
Brook Harbor and West Meadow, bordering the
Nissequogue River,174 and along the Peconic
Estuary. Some marshes around the three large
bays western Long Island Sound (Little Neck
Bay, Manhasset Bay, and Hempstead Harbor)
provide feeding and nesting areas for green-
backed heron, clapper rail, and American black
duck, as well as feeding areas for wading
birds.175
Marshes will be lost where the shorelines are
backed by steep slopes or where shorelines are
hardened. There has already been a significant
loss of the historical area of vegetated tidal
wetlands in Long Island Sound.176 In fact, local
scientists have observed marsh submergence for
decades.177 The full extent and causes of marsh
losses are unknown, but some local scientists
believe that sea level rise may be an important
factor.178 Authors of the Long Island Sound
Habitat Restoration Initiative reported that
emergent marsh, especially low marsh, is
converting to intertidal flat along the shores of
many of the tidal rivers that drain into the Sound,
173
Ron Rosza, coastal ecologist with the Connecticut Office of
the Long Island Sound Program, email entitled Opportunity to
comment on U.S. EPA-sponsored papers related to sea level rise
and related impacts on habitat and species, to Karen Scott, EPA,
2/20/07 (discussing visual observations).
174NYS Department of State, Division of Coastal Resources,
2004 (see note 171). Wetland losses will also occur along
shorelines with steep slopes, even though they are not
hardened—a common characteristic of the north shore of Long
Island.
175USFWS, 1997, The Narrows, Complex #20, p. 613 (see note
172).
17oHolst et al., 2003, p. 1-8 (see note 169).
177
Ron Rosza, written communication to EPA, 2/20/07
(discussing personal observations) (see note 173).
178Mushacke, F., 2003, "Wetland loss in the Peconic Estuary,"
abstract of presentation at the Long Island Sound Tidal Wetland
Loss Workshop, June 24-25, Stony Brook, NY, Workshop
Proceedings and Recommendations to the Long Island Sound
Study, p. 18. Available at:
http://www.longislandsoundstudv.net/liabitatrestoration/more.ht
m. In this abstract, Fred Mushacke, a marine biologist with the
New York State Department of Environmental Conservation,
who has conducted GIS analyses to determine areas of marsh loss
in the Peconic Estuary, stated that "the extent and causes of
vegetative losses are currently unknown and can only be
surmised. It is, however, a synergy of anthropogenic and natural
causes, and may include, but is not limited to, sediment budget
disruption, sea level rise, erosion, subsidence, and
eutrophication."
and concluded that "the biophysical changes in
these marshes bear a striking resemblance to
other eastern seaboard wetlands that scientists
attribute to accelerated relative sea level rise."179
The loss of vegetated low marsh reduces habitat
for several rare bird species that nest only or
primarily in low marsh (e.g., seaside sparrow)
(see Section 3.1). Low marsh also provides
foraging areas sheltered from predators for
dozens of fish species, including small resident
fishes such as mummichog, striped killifish, and
sheepshead minnow, and early life stages of
estuarine and marine transients, which use the
tidal creeks and low marsh for a nursery area
(Section 3.1). Many of these transient fish
species such as weakfish and winter flounder
enter local commercial and recreational fisheries
as adults.18" Diamondback terrapin live in the
creeks of the low marsh, where they feed on
plants, mollusks, and crustaceans.181 Marsh
invertebrates of the Sound's low marsh zones
include rough periwinkles, ribbed mussels,
fiddler crabs, striped sea anemone, and the
common clamworm.182
Some wetlands along Long Island Sound will be
allowed to respond naturally to sea level rise, and
where migration is possible, preservation of local
biodiversity and some regionally rare species is
possible. For example, local planners believe that
Peconic Estuary shorelines around Shelter
Island, Robins Island, the Conscience Point
National Wildlife Reserve, the E. A. Morton
National Wildlife Reserve, Novack, Sag Harbor,
Orient Point and Orient Beach, and Napeague
Bay will be allowed to respond naturally to sea
level rise. Local planners also expect that coastal
lands designated for preservation, conservation,
or recreation in northern Suffolk County will
remain unprotected.
179Holst et al., 2003, p. 1-8 (see note 169).
180See, for example, NYS Department of State, Division of
Coastal Resources, 2004, p. 3 (see note 171).
lslLong Island Sound Foundation, n.d., Plants & Animals of
Hammonasset, available at:
http://www.lisfoundation.org/coastal access/hamm wildlife.html
The Long Island Sound Foundation has been collecting and
disseminating information on the sound for the public since 1992.
182Warren, R.S. and P.E. Fell, 1996,"Phragmites australis on the
lower Connecticut River: Patterns of invasion and spread. As
cited on p. 1-2 of Hoist et al., 2003 (see note 169).
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[ SECTION 3.2 213 ]
Some preservation of species may occur where
"soft" protection is the preferred protection
alternative. For example, local planners believe
that shore protection to hold back rising seas is
"likely" or "almost certain" along the shorelines
of Flanders Bay, where the Flanders Bay
Wetlands occur. The New York State
Department of State, Division of Coastal
Resources has concluded that if protection is
considered necessary, alternatives such as
vegetation-based approaches should be explored.
This agency has asserted that shoreline
hardening "may result in loss of productive
habitat areas which support the fish and wildlife
resources of Flanders Bay Wetlands." Several
rare bird species are found in the Flanders Bay
Wetlands, including least tern, common tern,
piping plover, black skimmer, osprey, and
common loon. Waterfowl also feed in and
around the wetlands. Midwinter aerial surveys
averaged 125 birds per year in the wetlands and
700 birds per year in the adjacent bays over the
period 1986-1996. Diamondback terrapin are
also found in the marshes and beaches along
Flanders Bay.183
Sea Level Fen
A sea level fen vegetation community grows
along Flanders Bay.184 This rare type of coastal
wetland grows only under the unusual
circumstances where there is a natural seep from
a nearby slope providing nutrient-poor
groundwater to support its unique vegetation,
and where there is protection from nutrient-rich
tidal flow (see Section 3.1). Because of the need
of sea level fen vegetation for nutrient-poor
waters, the Flanders Bay sea level fen may not
survive inundation by sea level rise.
183NYS Department of State, Division of Coastal Resources,
2004, Long Island Sound and Long Island, Flanders Bay
Wetlands, pp. 1^1 (see note 171).
184NYS Department of State, Division of Coastal Resources,
2004, Flanders Bay Wetlands, p. 1 (see note 171).
Estuarine Beaches
Barrier beaches are less common than tidal
wetlands in the Long Island Sound study area,
but beaches may be at greater risk because sea
level rise will accelerate shoreline erosion.
Headland erosion is the dominant type of beach
development along the Sound's Long Island
shoreline.185
Notable undeveloped barrier beaches along the
north shore of Long Island include those fronting
Hempstead Harbor,186 the beach-wetland system
on Eatons Neck Point,187 the Port Jefferson
Beaches near the Town of Brookhaven,188 the
Nissequogue Inlet Beaches at the mouth of the
Nissequogue River in the Town of Smithtown,189
and Cedar Point Peninsula in the Peconic
Estuary.19"
The sandy barrier-beach system fronting
Hempstead Harbor is typical of these beach
systems, and shows a characteristic community
progression from the foreshore to the bay side, or
backshore. The foreshore occurs between the
highest and lowest tide zones. The abundant
invertebrate fauna characteristic of this area
provide forage for sanderling, semipalmated
plovers, and other shorebirds that stop over
during migrations.191 Shorebirds feed on all
trophic levels of beach invertebrate communities,
including primary consumers (herbivorous
insects, amphipods, and isopods, as well as
suspension-feeding crabs and bivalves) and the
secondary consumers that feed on them (crabs,
isopods, polychaetes, and beetles).192 The
maritime beach community between the mean
185Long Island Sound Habitat Restoration Initiative, 2003,
Technical Support for Habitat Restoration, Section 5: Coastal
Barriers, Beaches, and Dunes. November 2003. EPA Long
Island Sound Office, Stamford, CT, p. 5-1. Available at:
http://www.longislandsoundstudv.net/liabitat/index.htm.
18oNYS Department of State, Division of Coastal Resources,
2004, Hempstead Harbor (see note 171).
187NYS Department of State, Division of Coastal Resources,
2004, Eatons Neck Point (see note 171).
188NYS Department of State, Division of Coastal Resources,
2004, Port Jefferson Beaches (see note 171).
189NYS Department of State, Division of Coastal Resources,
2004, Nissequogue Inlet Beaches (see note 171).
190NYS Department of State, Division of Coastal Resources,
2004, Cedar Point Peninsula (see note 171).
191Long Island Sound Habitat Restoration Initiative, 2003, p. 5-2
(see note 185).
192See, for example, Bertness, 1999 (see note 133).
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[ 214 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
high tide and the primary dune provides nesting
sites for several rare bird species, including
piping plover, American oystercatcher, black
skimmer, least tern, common tern, roseate tern,
the federally listed threatened northeastern beach
tiger beetle, and horseshoe crab. Dunes and the
upper limit of the backshore beach is used for
nesting by diamondback terrapin.193 They also
nest on dredged sands and have been observed
nesting on artificial dikes in the town of
Fairfield, Connecticut.194
One study involving interviews with local
planners found that nearly all of the Long Island
shoreline of the Sound is "almost certain" to be
protected in response to sea level rise. The study
assumed that property owners fund their own
shore protection. Moreover, the Long Island
Sound Habitat Restoration Initiative cautions,
"Attempts to alter the natural cycle of deposition
and erosion of sand by construction of
bulkheads, sea walls, groins, and jetties interrupt
the formation of new beaches."195
Tidal Flats
Longshore drift, which usually occurs from east
to west along the Sound's Long Island shoreline,
carries some of the material that erodes from
bluffs and later deposits it to form tidal flats and
barrier spits or shoals.196 Shoals along the Long
Island shoreline, particularly around Duck Point,
Baiting Hollow, and the Port Jefferson area,
provide forage for numerous bird species as well
as habitat for shellfish.197 There is hard clam
habitat around the northern bays.198 One of the
largest areas of tidal mudflats on the north shore
is near Conscience Bay, Little Bay, and Setauket
Harbor west of Port Jefferson. Large beds of
193Long Island Sound Habitat Restoration Initiative, 2003, pp. 5-
3, 5-4 (see note 185).
194Ron Rosza, email to EPA 2/20/07 (discussing visual
observations) (see note 173).
195Long Island Sound Habitat Restoration Initiative, 2003, p. 5-7
(see note 185).
1%Long Island Sound Habitat Restoration Initiative, 2003, pp. 5-
1, 5-2 (see note 185).
197Important Ecological Areas in and Around Long Island Sound,
Map Panel 9 of 10 - Riverhead Area and Map Panel 8 of 10 -
Port Jefferson Area, n.d., produced by the USFWS Service,
Coastal Ecosystems Program, Charlestown, RI, for Long Island
Stewardship Initiative. Available at:
www, rpa. org/maps/lismaps .html.
198USFWS, 1997 (see note 172)
hard clams, soft clams, American oysters, and
ribbed mussels are found in this area.199 In
western Long Island Sound, low marsh is
converting to tidal flats as seas rise.2"" As seas
continue to rise and the flats become inundated,
the invertebrates of tidal flats could become less
accessible for feeding by the many wading birds,
dabbling ducks, and shorebirds whose growth
and survival depend on such invertebrate food
supplies.2"1 It is known, for example, that
shorebird abundance is directly correlated with
the abundance of invertebrate forage.2"2
NEARSHORE SHALLOW WATERS AND
SUBMERGED AQUATIC VEGETATION
(SAV)
Eelgrass distribution along the Sound is limited
to the Peconic Estuary.2"3 The Marine Program
of Cornell Cooperative Extension of Suffolk
County is monitoring sites in Bullhead Bay,
Gardiners Bay, Northwest Harbor, Orient
Harbor, Southold Bay, and Three Mile Harbor
(see Map 3.1).204 The U.S. Fish and Wildlife
Service reports that eelgrass beds of statewide
significance are in Orient Bay2"5 and Cedar
199NYS Department of State, Division of Coastal Resources,
2004, Conscience Bay, Little Bay and Setauket Harbor, p. 1 (see
note 171).
"""Ron Rosza, email to EPA, 2/20/07 (discussing visual
observations) (see note 173).
201Erwin, R.M., D.R. Cahoon, D. J. Prosser, G.M. Sanders, and P.
Hensel, 2006, "Surface elevation dynamics in vegetated Spartina
marshes versus unvegetated tidal ponds along the mid-Atlantic
coast, USA, with implications to waterbirds," Estuaries and
Coasts 29:96-106, p. 103.
202See, for example, Evans, P.R., and P. J. Dugan, 1984, "Coastal
birds: Numbers in relation to food resources," in P.R. Evans, J.D.
Goss-Custard, and W.G. Hale (eds.), Coastal Waders and
Wildfowl in Winter, Cambridge University Press, Cambridge,
U.K.
203Eelgrass does not occur along northern Long Island Sound
because of nutrient enrichment.
204Schott, S. 2003. Eelgrass Monitoring: Historic Distribution and
Current Trends. Presentation at the Long Island Sound Tidal
Wetland Loss Workshop, .Time 24-25, 2003, Stony Brook, New
York, Workshop Proceedings and Recommendations to the Long
Island Sound Study. Available at:
http://www.longislandsoundstudv.net/liabitatrestoration/more.ht
m; Tiner, R., H. Bergquist, T. Halavik, and A. MacLachlan.
2003. Eelgrass Survey for Eastern Long Island Sound,
Connecticut and New York. U.S. Fish and Wildlife Service,
National Wetlands Inventory Program, Northeast Region,
Hadley, MA. National Wetlands Inventory report.
205NYS Department of State, Division of Coastal Resources,
2004, Orient Bay, p. 1 (see note 171).
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[ SECTION 3.2 215 ]
Point/Hedges Bank Shallows.2"6 A recent survey
found 15.7 acres of eel grass on the north shore at
Mulford Point, and 194 acres on Fisher's
Island.207
The estuary's eelgrass beds provide food, shelter,
and nursery habitats to a diversity of species,
including worms, shrimp, scallops and other
bivalves, crabs, and fish.2"8 Horseshoe crabs
reportedly forage in the eelgrass beds of Cedar
Point/Hedges Bank, where they are prey for
loggerhead turtles (federally listed as
threatened), crabs, whelks, and sharks. Atlantic
silverside is an important prey species that
spawns here; silverside eggs provide an
important food source for seabirds, waterfowl,
and blue crab, and adults are prey for bluefish,
summer flounder, rainbow smelt, white perch
Atlantic bonito, and striped bass. The Cedar
Point/Hedges Bank Shallows eelgrass beds are
known for supporting a bay scallop fishery of
statewide importance.2"9
The consequences of sea level rise for SAV are
unknown. However, Short andNeckles (1999)
predicted that a 50 cm (19.7 in.) increase in
water depth as a result of sea level rise, which
could occur in this century, could reduce the
light available for seagrass photosynthesis by 50
percent, which would reduce eelgrass growth by
30-40 percent.21" In turn, this would result in
reductions in the productivity and functional
values of seagrass beds. This implies that
reductions in the growth and survival of eelgrass
beds around the Peconic Estuary could harm
local populations of scallops, which support a
valuable fishery, as well as horseshoe crabs and
other species that are prey for many species of
commercial, recreational, and ecological value.
The movement of eelgrass beds shoreward as
seas rise could be impeded by steep shores or
erosion and water turbidity in front of shoreline
protection structures. Local planners believe that
shorelines around Shelter Island, Robins Island,
the Conscience Point National Wildlife Reserve,
the E. A. Morton National Wildlife Reserve,
Novack, Sag Harbor, Orient Point and Orient
Beach, and Napeague Bay will be allowed to
respond naturally to sea level rise. Other
shorelines of the Peconic Estuary are considered
"likely" or "almost certain" to be protected, and
if these shorelines are hardened, SAV will be
unable to migrate in response to sea level rise.
MARSH AND BAY ISLANDS
Several offshore islands in western Long Island
Sound are significant for their colonial wading
bird rookeries. The most important are
Huckleberry Island, Great Captain Island, North
Brother Island, South Brother Island, and Pelican
Island. These islands are rocky and mostly
covered by deciduous forest; their rocky
shorelines provide habitat for species such as
shellfish, sea stars, and barnacles. North and
South Brother islands have the largest black
crowned night heron colony in New York State,
along with snowy egret, great egret, cattle egret,
and glossy ibis.211 The islands' bird colonies are
of regional significance, and loss of island area
with sea level rise could have far-reaching
consequences.
20oNYS Department of State, Division of Coastal Resources,
2004, Cedar Point/Hedges Bank Shallows, p. 1 (see note 171).
207Tiner et al., 2003 (see note 204); see also
http://counties.cce.comell.edii/suffolMiabitat restoration/project
page/StT/eeproiectsStT.htm.
208Peconic Estuary Program, 2001, Peconic Estuary
Comprehensive Conservation and Management Plan, sponsored
by the USEPA under Sec. 320 of the Clean Water Act, Suffolk
County Department of Health Services, Program Office, p. 4-4.
209NYS Department of State, Division of Coastal Resources,
2004, Cedar Point/Hedges Bank Shallows, p. 2 (see note 171).
210Short, and Neckles, 1999, p. 175 (see note 91). 211USFWS, 1997, pp. 612-614 (see note 172).
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[ 216 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
The Long Island Sound Study considers Plum
Island, Little Gull Island, and Great Gull Island
off Orient Point "exemplary" colonial waterbird
habitat, with sites "of national—if not
international—significance."212 The islands are
relatively small and covered with grassy and
herbaceous vegetation. According to the North
Fork Audubon Society, Great Gull Island hosted
1,500 pairs of the endangered roseate tern in
1996 and 7,750 pairs of common tern.213 The
Long Island Sound Study reports that this
population is the second largest breeding
population of the roseate tern in North
America.214
Gardiners Island,215 Robins Island,216 and Cow
Neck217 in Little Peconic Bay are in private
ownership, and therefore staff of the Suffolk
County Department of Planning believe that the
shorelines of these properties will be left in a
natural state. These islands provide habitats for
many rare species such as roseate tern, common
tern, least tern, northern harrier, red-tailed hawk,
eastern mud turtle, and diamondback terrapin.
Even if some protection of the islands' shorelines
does occur, it seems likely that it will involve
vegetation-based approaches rather than
shoreline hardening to help preserve these
valuable habitats.218
212Long Island Sound Study, LIS Stewardship Initiative, a
cooperative effort involving researchers, regulators, user groups
and other concerned organizations and individuals. Accessed
December 4, 2007 at:
http://www.longislandsoundstudv.net/stewardship/stewardship si
tes.htm.
213Fact sheet by North Fork Audubon Society entitled Great Gull
Island IBA. Accessed December 4, 2007 at:
http://www.northforkaudubon.org/Gui/Content.aspx?Page=IBAG
reatGull.
214Long Island Sound Study (see note 212).
215NYS Department of State, Division of Coastal Resources,
2004, Gardiners Island (see note 171).
21oNYS Department of State, Division of Coastal Resources,
2004, Robins Island (see note 171).
217NYS Department of State, Division of Coastal Resources,
2004, Cow Neck (see note 171).
218For example, see NYS Department of State, Division of
Coastal Resources, 2004, Robins Island, p. 5 (see note 171).
-------
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Map 3.1. Locations and Types of Habitat Discussed in this Report: Long Island
-------
3.3 Long Island's South Shore Barrier Island/
Lagoon System Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats along the south shore of
Long Island are potentially at risk because of sea
level rise. The large back-barrier bays of the
south shore include, from west to east,
Hempstead Bay, South Oyster Bay, Great South
Bay, Moriches Bay, and Shinnecock Bay.219
These bays contain regionally significant habitats
for fish, shellfish, and birds, and a great deal is
known about their ecology and habitat needs.
Based on existing literature and the knowledge
of local scientists, this brief literature review
discusses the coastal species in the region that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection (see Map 3.1). Although it is possible
to make qualitative statements about the possible
impacts if sea level rise causes a total loss of
habitat, our ability to discern what the impact
might be if only a portion of the habitat is lost is
more limited. A total loss of habitat is possible if
shores are protected with hard structures and the
wetlands are unable to keep pace with sea level
rise.
Back-Barrier Salt Marshes
There are extensive salt marshes to the west of
Great South Bay in southern Nassau County.22"
These marshes are particularly notable because
much of the historically large area of marsh on
the mainland shoreline of southern Nassau
County has been lost to development and
shoreline armoring, including the mainland
219One other back-barrier bay, Jamaica Bay, is discussed in
Section 3.4, New York City, because it is most often considered
as part of management programs in that area (e.g., the New
York/New Jersey Harbor Estuary Program).
220USFWS, 1997, Great South Bay Habitat Complex #14, pp.
447-467 (see note 172).
marshes of South Oyster Bay221 and the
Hempstead Bay-South Oyster Bay habitat
complex.222
Based on existing studies, a panel of accretion
experts, convened by EPA for this report, expect
that the back-barrier marshes adjacent to Jones
Inlet are keeping pace with the current rate of sea
level rise and may continue to keep pace if the
rate increases by 2 mm/yr. Under this scenario,
wider marshes may survive this modest increase
in the rate of sea level rise, but fringing marshes
are likely to be lost. These scientists also
indicated that if the rate of sea level rise
increases by 7 mm/yr, all of the marshes adjacent
to Jones Inlet will be lost. To the east of Jones
Inlet, the extensive back-barrier and fringing salt
marshes surrounding Great South Bay, Moriches
Bay, Shinnecock Bay, and Southampton are
keeping pace with current rates of sea level rise,
but the accretion panel predicted that their ability
to keep pace will be marginal if the rate of sea
level rise increases by 2 mm/yr, and marshes will
be lost if rates increase by 7 mm/yr (see Reed et
al., Section 2.1).
Opportunities for marsh migration along Long
Island's south shore will be limited. Much of the
mainland shoreline in southern Nassau County is
bulkheaded, and the rural areas that remain in
eastern Suffolk County are likely to be
developed in the future. The state requires a 75-
foot buffer around tidal wetlands to make marsh
migration possible, but outside of this buffer
221NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program, 1998,
Shorebirds, South Shore Estuary Reserve, Technical Report
Series. Available at:
http://www.nvswaterfronts.com/Final Draft HTML/Tech Repor
t HTM/PDFs/C 8A Index pdf.htm.
222USFWS, 1997, Hempstead Bay-South Oyster Bay, Habitat
Complex #15, p. 483—494 (see note 172).
-------
[ SECTION 3.3 219 ]
development and shoreline protection are
permitted. Moreover, where wide areas of marsh
do not keep pace, there will be a net loss even if
marshes can migrate.
Increases in tidal creeks and channels with a
modest increase in sea level rise (2 mm/yr) could
benefit marsh fishes, including many
commercially and recreationally important
marine and estuarine transient species that move
into the marshes for spawning and nursery
habitat. However, where marshes are lost as the
rate of sea level rise increases to 7 mm/yr, local
populations may eventually move elsewhere in
search of suitable nursery and foraging areas. An
overall loss of nursery habitat and forage could
reduce the productivity of the area's highly
valued fishery resources.
The recovery of a number of at-risk bird species
could be impeded if additional marsh area is lost
as a result of sea level rise. For example, the
Dune Road Marsh west of Shinnecock Inlet
provides nesting sites for several species that are
already showing significant declines, including
clapper rail, sharp-tailed sparrow, seaside
sparrow, willet, and marsh wren.223 These
marshes are also the only area in New York State
where black rails are currently found on a regular
basis and the only documented breeding location
for sora rails on Long Island.224
The northern diamondback terrapin feeds and
grows along marsh edges and the nearshore bays
of the south shore. Sites on the south shore
where terrapins reportedly are found include
Captree State Park, east of the Robert Moses
State Park on the Fire Island National Seashore,
the marshes and ditches of Tobay Sanctuary near
Guggenheim Park, and the western section of the
Ocean Parkway, where there are signs
announcing "Turtle Crossings" to protect
terrapins from automobile traffic.225 A local
terrapin expert believes that additional marsh
223USFWS, 1997, p. 418 in Shinnecock Bay Habitat Complex
#12 (see note 172).
224NYS Department of State, Division of Coastal Resources,
2004 (see note 171).
225NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program, 1998
(see note 221).
loss could lead to a "very serious reduction" in
their already low abundance.226
Back-Barrier Beaches
As sea levels rise, the back-barrier beaches will
erode in front of shoreline protection structures,
and will be lost without continual beach
nourishment. Eggs of species that nest on
estuarine beaches and abundant invertebrate
fauna provide forage for numerous bird species,
including migratory shorebirds and species that
nest on nearby barrier islands, such as the
federally threatened piping plover. Shorebirds
feed on all trophic levels of beach invertebrate
communities, including herbivorous insects,
amphipods, isopods, crabs, and bivalves.227
The back-barrier beaches of the south shore
provide nesting sites for the northern
diamondback terrapin,228 the endangered roseate
tern,229 and horseshoe crabs.23" Cedar Beach in
Great South Bay is considered important for the
recovery of roseate tern.21' Shorebirds feed
preferentially on horseshoe crab eggs during
their spring migrations,232 and local biologists
believe that the large numbers of shorebirds west
of Shinnecock Inlet may be due in part to
horseshoe crab spawning in the area.233 Loss of
this food resource could have a significant effect
on migrating shorebirds such as red knot, which
feed almost exclusively on horseshoe crab eggs
during their spring migration, when they must
22oDr. Russell Burke, Department of Biology, Hofstra University,
Hempstead, NY. August 1, 2006. "Diamondback terrapin and sea
level rise." Email to E. Strange, Stratus Consulting, expressing
his opinion about the implications of marsh loss in southern Long
Island for terrapins. (Russell Burke has operated an annual
diamondback terrapin conservation project at the Jamaica Bay
Wildlife Refuge in the Gateway National Recreational Area since
1998.)
227Dugan et al., 2003 (see note 127).
228NYS Department of State, Division of Coastal Resources,
2004, Great South Bay-West, p. 3 (see note 171).
~9USFWS, 1997, p. 454 in Great South Bay, Complex #14 (see
note 172).
230NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program, 1998
(see note 221).
231USFWS, 1997, Great South Bay. Complex #14 (see note 172).
232
"USFWS, 2005, Red knot, Calidris camitus rufa. Fact sheet
available at: http://www.fws.gov/nortlieast/redknot/facts.pdf.
233NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program. 1998
(see note 221).
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[ 220 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
double in weight to support long-distance
migrations.234 A reduction in the area of back-
barrier beach habitat would also negatively
impact nesting by diamondback terrapins.
Although exact numbers are unknown, a
diamondback terrapin expert who has conducted
field studies in the area estimates that currently
only a few hundred female diamondback
terrapins still nest on the back-barrier beaches of
Long Island's south shore.235
Tidal Flats
Of the extensive tidal flats along Long Island's
southern shoreline, most are found west of Great
South Bay and east of Fire Island Inlet along the
bay side of the barrier islands,236 in the
Hempstead Bay-South Oyster Bay complex,237
and around the Moriches and Shinnecock
inlets.238 These flats are important foraging areas
for birds and provide habitat for several edible
shellfish species, including soft clam, northern
quahog (hard clam), bay scallop, and blue
mussel. In Shinnecock Bay, the Shinnecock
Reservation has developed a subsistence
aquaculture program that includes northern
quahog and American oyster.239
Tidal flats and shallow water habitats are heavily
used by shorebirds, raptors, and colonial
waterbirds in spring and summer and by
waterfowl during fall and winter.24" The John F.
Kennedy Bird Sanctuary is a particularly
important feeding area for birds in South Oyster
Bay. In summer, the state threatened least tern
and a variety of herons and egrets forage here,
along with the federally endangered roseate tern.
The sanctuary also provides overwintering
234USFWS, 2005, Red knot. Fact sheet (see note 232).
235Dr. Russell Burke, email to E. Strange, Stratus Consulting (see
note 226).
23oUSFWS, 1997, p. 449 in Great South Bay Habitat Complex
#14 (see note 172).
237USFWS, 1997, p. 484 in Hempstead-South Oyster Bay,
Habitat Complex #15 (see note 172).
238NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program, 1998, p.
4 (see note 221).
239USFWS, 1997, Shinnecock Bay Habitat Complex #12 (see
note 172).
240Erwin, M.R., 1996, "Dependence of waterbirds and shorebirds
on shallow water habitats in the Mid-Atlantic coastal region: An
ecological profile and management recommendations," Estuaries
19:213-219, p. 213.
habitat for abundant waterfowl, including
American black duck, blue-winged, and green-
winged teal.241 Shinnecock Bay supports
populations of wintering waterfowl of statewide
significance.242
The tidal flats around Moriches and Shinnecock
inlets are particularly important foraging areas
for migrating shorebirds. If shoreline waters
become too deep for foraging on these flats,
migrating shorebirds could have insufficient
foraging areas to support their long-distance
migrations. Scientists writing on behalf of the
South Shore Estuary Reserve program have
asserted that "because shorebirds concentrate in
just a few areas during migration, loss or
degradation of key sites could devastate these
populations." These scientists note that local
populations of black-bellied plover, whimbrel,
red knot, sanderling, semipalmated sandpiper,
least sandpiper, and short-billed dowitcher are
already showing declines.243
Nearshore Shallow Waters and
Submerged Aquatic Vegetation
(SAV)
Seagrass beds occur along much of the southern
shoreline of Long Island.244 The consequences of
sea level rise for SAV are unknown. However,
Short and Neckles predicted that a 50 cm (19.7
in.) increase in water depth as a result of sea
level rise, which could occur during this century,
could reduce the light available for seagrass
photosynthesis by 50 percent, resulting in a 30-
40 percent reduction in eelgrass growth. These
researchers suggested that this will, in turn,
result in reduced productivity and functional
values of seagrass beds.245 The importance of
eelgrass beds for the secondary production of the
south shore is indicated by a study of the Great
241USFWS, 1997, p. 487 in Hempstead-South Oyster Bay,
Habitat Complex #15 (see note 172).
242NYS Department of State, Division of Coastal Resources,
2004, Shinnecock Bay, p. 2 (see note 171).
243NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program, 1998, p.
1 (see note 221).
244NOAA, Benthic Habitat Mapping. SAV map accessed
December 4, 2007 at:
http://www.csc.noaa.gov/bentliic/data/nortlieast/longisl.htm.
245Short and Neckles, 1999, p. 178 (see note 91).
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[ SECTION 3.3 221 ]
South Bay by Briggs and O'Connor (1971), who
found that 23 of 40 recorded fish species clearly
preferred naturally vegetated bottom to
unvegetated areas.246
Marsh and Bay Islands
Increased flooding and erosion of marsh and
dredge spoil islands could reduce habitat for bird
species that forage and nest on these islands,
particularly gulls and terns. Erosion on Warner
Island is reducing nesting habitat for roseate tern
and increasing flooding risk during nesting.247
The Hempstead Bay-South Oyster Bay complex
includes a network of salt marsh and dredge
spoil islands that are important for nesting by
herons, egrets, and ibises. Hempstead Bay is the
primary nesting area in Long Island for yellow-
crowned night-herons. Waterfowl such as brant
and American black duck feed and rest in the
shallow waters around the islands and tidal flats
of the complex. An average of 25,000 waterfowl
have been counted on midwinter aerial
surveys.248 Lanes Island and Warner Island in
Shinnecock Bay support colonies of the state-
listed common tern and the federally endangered
roseate tern.249 Carter's Island has supported
nesting by the state endangered least tern.25"
Local planners have indicated that eroding marsh
islands such as those in Great South Bay may
need to be artificially protected to maintain the
vegetated wetlands.
24oBriggs, P.T. and J.S. O'Connor, 1971, "Comparison of shore-
zone fishes over naturally vegetated and sand-filled bottoms in
Great South Bay," New York Fish and Game Journal 18(1): 15—
41; cited in NYS Department of State and USFWS, Southern
New England-New York Bight Coastal Ecosystems Program,
1998, Estuarine Fish, p. 8 (see note 221).
247NYS Department of State and USFWS, Southern New
England-New York Bight Coastal Ecosystems Program, 1998,
Coastal Colonial Waterbirds, p. 6 (see note 221).
248USFWS, 1997, p. 486 in Hempstead Bay-South Oyster Bay,
Habitat Complex #15 (see note 172).
249USFWS, 1997, p. 418 in Shinnecock Bay, Habitat Complex
#12 (see note 172).
250USFWS, 1997, p. 432 in Moriches Bay, Habitat Complex #13
(see note 172).
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3.4 New York City, the Lower Hudson River, and
Jamaica Bay Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats in the region encompassing
New York City, the lower Hudson River, the
East River, and Jamaica Bay are potentially at
risk because of sea level rise. Although the
region is one of the most heavily urbanized areas
along the U.S. Atlantic Coast, there are
nonetheless regionally significant habitats for
fish, shellfish, and birds in the area, and a great
deal is known about the ecology and habitat
needs of these species.
Based on existing literature and the knowledge
of local scientists, this brief literature review
discusses those species that could be at risk
because of further habitat loss resulting from sea
level rise and shoreline protection (see Map 3.2).
Although it is possible to make qualitative
statements about the ecological implications if
sea level rise causes a total loss of habitat, our
ability to say what the impact might be if only a
portion of the habitat is lost is more limited. A
total loss of habitat might be expected if shores
are protected with hard structures and the
wetlands are unable to keep pace with sea level
rise.
Most shorelines in the New York metropolitan
area are heavily modified. Because the remaining
coastal land is at a premium, planners indicate
that most of the shoreline is almost certain to be
protected. The remaining undeveloped land
along the shore continues to be developed and
armored.251 Where protection occurs, New York
City's Waterfront Revitalization Program (WRP)
requires the use of nonstructural alternatives
such as beach nourishment, dune construction,
and vegetation wherever possible. Planners
expect that the only sizeable areas in the New
York City metropolitan area that are unlikely to
be protected are portions of the three Special
Natural Waterfront Areas (SNWAs) designated
by the city: Northwest Staten Island/Harbor
Heron SNWA; East River-Long Island Sound
SNWA; and Jamaica Bay SNWA.
TIDAL WETLANDS
Staten Island. Hoffman Island and Swinburne
Island are National Park Service properties lying
off the southeast shore of Staten Island; the
former has important nest habitat for herons, and
the latter is heavily nested by cormorants.252 The
Northwest Staten Island/Harbor Herons SNWA
is an important nesting and foraging area for
herons, ibises, egrets, gulls, and waterfowl.253
The so-called Harbor Herons Complex includes
three island heronries of regional significance,
including Shooters Island, Pralls Island, and Isle
of Meadows (see subsequent section on islands).
Several tidal emergent, salt, brackish, and fresh
water marshes provide foraging areas for the
birds of the island heronries, including Arlington
251
George Frame, National Park Service, in email entitled
Comments on NYHarbor&RaritanBay papers EPA feb07, to
Karen Scott, EPA, 2/20/07, suggests that "many urban planners
are not preserving undeveloped lands along the shores of the ^^eorge Frame, 2/20/07 email (see note 251).
estuary; even today they are building and hardening in many " 3USFWS, 1997, p. 578 in Arthur Kill Complex, Complex #18
areas." (see note 172).
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[ SECTION 3.4 223 ]
Marsh, Sawmill Creek Marsh, Gulfport Marsh,
Merrill's Marsh, Old Place Creek, Neck Creek
Marsh, and Fresh Kills.254 With the exception of
Fresh Kills, shoreline protection is considered
almost certain in these areas. Loss of these
marshes could have a significant negative impact
on the island heronries because of a lack of
alternative foraging sites nearby.
The Fresh Kills wetland system is one of the
largest tidal wetland systems in the region,
covering an estimated 405 ha (1,000 acres).255
Local planners expect that these wetlands will
probably be allowed to respond naturally to sea
level rise, but migration may not be possible
because of the relatively steep slopes that have
formed near the shore as a result of landfilling
activities.
Manhattan. Most of the shoreline of Lower
Manhattan and the Battery has been bulkheaded
and filled. An exception is the natural shoreline
and wetlands at the mouth of the Harlem River at
New York City's Inwood Hill Park.256 The park
contains low salt marsh and a broad mudflat that
runs from the marsh to the channel of the Harlem
River Ship Canal. Great blue herons are found
along the flat in winter and snowy and great
egrets are common from spring through fall.257
The Lower Hudson River. Although the tidal
Hudson River extends upstream to the dam at
Troy, New York State's tidal wetland regulations
apply to the Hudson River shoreline only up to
the Tappan Zee Bridge. This is the estuarine
portion of the tidal river. Along this stretch of the
river there is relatively little marsh, with the
exception of brackish marshes at the mouth of
the Croton River, in Piermont Marsh, and in a
network of marshes behind Grassy Point near
Haverstraw Bay.258
Piermont Marsh is a 411.6 ha (1,017 acre)
brackish wetland on the western shore of the
lower Hudson River just below the Tappan Zee
Bridge, in the town of Orangetown, in Rockland
County.259 The New York State Department of
State has designated the marsh a Significant
Coastal Fish and Wildlife Habitat, and it has
been designated part of the Hudson River
National Estuarine Research Reserve by the
National Oceanic and Atmospheric
Administration and the New York State
Department of Environmental Conservation
(NYDEC).260
Piermont Marsh is dominated by common reed
and narrow-leaved cattail, along with some salt
marsh species that include smooth cordgrass,
salt-meadow cordgrass, and spike grass, making
it the location of the northernmost occurrence of
salt marsh species on the Hudson. Breeding birds
known to use the marsh for nesting include
relatively rare species such as Virginia rail,
swamp sparrow, black duck, least bittern, and
sora rail. A small number of osprey sometimes
gather in the marsh, particularly during spring
migration. Anadromous and freshwater fish use
the marsh's tidal creeks as a spawning and
nursery area. Killfish, mummichog, fiddler crab,
and blue crab use shallow marsh areas.
Diamondback terrapin, a federal species of
concern, reportedly nest in upland areas along
the marsh.261
Jamaica Bay, located between the boroughs of
Brooklyn and Queens, is the largest area of
protected wetlands in a major metropolitan area
along the U.S. Atlantic Coast. The bay includes
~54USFWS, 1997, p. 579 in Arthur Kill Complex, Complex #18
(see note 172).
255USFWS, 1997, p. 580 in Arthur Kill Complex, Complex #18
(see note 172).
25oUSFWS, 1997, p. 630 in Lower Hudson River Estuary,
Complex #21 (see note 172).
257Fact sheet by New York City Department Of Parks and
Recreation, Inwood Hill Park—Salt Marshes in New York City
Parks. Accessed December 4, 2007 at:
http://www.nvcgovparks.org/sub vour park/historical signs/hs
historical sign.php?id= 12864.
258USFWS, 1997, p. 631 in Lower Hudson River Estuary,
Complex #21 (see note 172).
259Fact sheet on Piermont Marsh Component of the Hudson River
Reserve by the Hudson River Reserve Program, National
Estuarine Research Reserve System. Accessed December 4, 2007
at:http://nerrs.noaa.gov/HudsonRiver/PiennontMarsh.html.
2o0USFWS, 1997, pp. 629, 633 in Lower Hudson River Estuary,
Complex #21 (see note 172).
2o1USFWS, 1997, p. 633 in Lower Hudson River Estuary,
Complex #21 (see note 172).
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[ 224 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
the Jamaica Bay Wildlife Refuge,262 which has
been protected since 1972 as part of the Jamaica
Bay Unit of the Gateway National Recreation
Area, administered by the National Park Service.
The refuge includes numerous salt marsh islands
that are sheltered from the Atlantic Ocean by the
Rockaway Peninsula.
Despite extensive disturbance from dredging,
filling, and development, Jamaica Bay remains
one of the most important migratory shorebird
stopover sites in the New York Bight region.263
The bay provides overwintering habitat for brant,
mallards, American black duck, canvasback
duck, and other waterfowl, and intertidal
mudflats for foraging migrants such as black
skimmer, plovers, and knots.264 The refuge and
Breezy Point, at the tip of the Rockaway
Peninsula, support populations of 214 species
that are state or federally listed or of special
emphasis, including 48 species of fish and 120
species of birds. These areas combined have
been designated as a Significant Coastal Fish and
Wildlife Habitat by the New York State
Department of State and as a Critical
Environmental Area by the NYDEC.265
Spring Creek Park266 is one of only two
remaining areas of salt marsh in the northern
tributaries of Jamaica Bay. Yellow-crowned
night heron, little blue heron, and willet are
202 Jamaica Bay Wildlife Refuge is managed by the National Park
Service, as part of the Jamaica Bay Unit of the Gateway National
Recreation Area. Hie refuge was originally created by the New
York City Parks department in 1951. See "Brochure: The
Jamaica Bay Wildlife Refuge", National Park Service, accessed
November 27,2006 at:
http://www.nps.gov/archive/gate/jbu/jbu_nature.htm. Many
people mistakenly call the refuge "Jamaica Bay National Wildlife
Refuge," but national wildlife refuges are managed by the US
Fish and Wildlife Service, not the National Park Service.
2o3USFWS, 1997, p. 532 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
2o4Hartig, E.K., V. Gornitz, A. Kolker, F. Mushacke, and D.
Fallon, 2002, Anthropogenic and climate-change impacts on salt
marshes of Jamaica Bay, New York City, Wetlands 22:71-89. p.
74, citing Wells (1998).
2o5USFWS, 1997, p. 532 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
2w>See fact sheet on Spring Creek Park by the New York City
Department of Parks and Recreation at
http://nycgovparks.org/sub_your_park/liistorical_signs/lis_histori
cal_sign.php?id= 11227.
found in these marshes.267 The nearby Four
Sparrow Marsh is the other remaining salt marsh
in this part of the bay. It is a particularly
noteworthy as an undisturbed nesting habitat for
four native species of sparrows that are in
decline, the sharp-tailed, seaside, swamp, and
song sparrows, and as a stopover site for some
326 species of migrating birds. Several species
of ducks, gulls, and wading birds also nest in
Four Sparrow Marsh and feed on marsh
mollusks and crustaceans.268
Because of its importance as an area of
significant biodiversity and its uniqueness as a
wildlife sanctuary in a highly developed urban
setting, planners expect that Jamaica Bay's
wetlands will be allowed to respond naturally to
sea level rise. However, wetlands in some parts
of the bay are currently showing substantial
losses. Researchers studying the salt marsh
islands near the John F. Kennedy International
Airport (including Yellow Bar Hassock, Black
Wall Marsh, Big Egg Marsh, East High Meadow
Marsh, Elders Point Marsh, and Jo Co Marsh)
estimated that marsh loss in the area averaged 12
ha (29.7 acres) per year from 1974 to 1999, even
though the area is a national park.269 This
represents an increase in marsh loss of 8 ha (19.8
acres) per year over preceding decades when the
area was not yet part of the Gateway National
Recreation Area. The estimated rate of loss has
been increasing, averaging 18 ha (44.5 acres) per
year over the period 1994 to 1999.270 The reasons
for this accelerating trend in marsh loss aren't
completely clear, though sea level rise has been
implicated as one possible cause.271'272 However,
the Jamaica Bay researchers noted that the
significant marsh loss that is already occurring
"implies that accretion rates in Jamaica Bay may
2o7USFWS, 1997, p. 532 in Jamaica Bay and Breezy Point
Complex #16 (see note 172).
2o8See fact sheet on the Four Sparrow Marsh Preserve by the New
York City Department of Parks and Recreation, available at:
http://www.nvcgovparks.org/sub about/parks divisions/nrg/fore
ver wild/site.php?FWID=21.
2o9Hartig, et al., 2002 (see note 264).
270Hartig et al., 2002, p. 71 (see note 264).
271Hartig et al., 2002, p. 75 (see note 264).
272George Frame, 2/20/07 email (see note 251), suggests that "the
catastrophic loss of salt marshes in Jamaica Bay could be due
mainly to input of nutrients and contaminants from wastewater
treatment plants. Also, past dredging and subaqueous borrow pits
may act as a sediment sink, starving salt marshes. Sea level rise
might be less important."
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[ SECTION 3.4 225 ]
be insufficient, even at present rates of sea level
rise, to compensate for losses due to erosion and
other factors."273
There are significant ecological implications of
marsh loss in this area. Annual marsh primary
production ranges from 700 to 1,500 g/m2 in
Jamaica Bay marshes.274 This primary production
is essential for the larger estuarine food web,
including the production of commercially and
recreationally valuable fish species that use
marshes as nursery areas.275 Kneib (2003)
developed models of marsh nekton production
resulting from marsh primary production in
Georgia marshes and estimated that nekton
production ranges from 15 to 42 kg/ha/yr, a third
of which represents the production of
commercial and recreational species that use the
marshes as nursery areas.276 Thus, loss of these
wetlands, even if the current rate of 18 ha/yr
does not increase as sea level rise increases,
would have an important impact, not just on
marsh primary production but also on the
production of fish and shellfish within both the
marsh and the surrounding estuary. In fact, state
and federal governments with holdings in the
area indicate that some form of protection may
be necessary to protect the significant ecological
value of the bay, including applying sediment to
raise the marsh surface.
Estuarine Beaches
Among the relatively few areas of beach
remaining in the New York City Metropolitan
Area are the beaches of the Rockaways, Coney
Island, and the South Shore of Staten Island.
Beach nourishment is planned or under way for
all of these areas.
Jamaica Bay has been designated and mapped as
a protected beach unit pursuant to the federal
273Hartig et al., 2002 p. 82 (see note 264).
274Hartig et al., 2002, p. 71 (see note 264).
275Teal, 1986 (see note 10).
27oKneib, R.T., 2003, "Bioenergetics and landscape
considerations for scaling expectations of nekton production from
intertidal marshes," Marine Ecology' Progress Series 264:279-
296. (The modeled nekton production estimates were based on an
estimated annual above ground primary production of 1,250
grams dry weight per square meter derived from field data, which
is within the range of the annual primary production estimated for
Jamaica Bay marshes.)
Coastal Barrier Resources Act.277 Much of the
bay's shoreline has been hardened with seawalls
and bulkheads, so estuarine sandy beach habitat
is now uncommon.278 Remaining estuarine
beaches occur off Belt Parkway (e.g., Plumb
Beach) and on the bay islands.279
Several islands in Jamaica Bay contain
mountains of dredged sand (on top of salt
marshes), so they now have sandy beaches.
Sandy beach also exists from Breezy Point tip to
Fort Tilden (at Flatbush Avenue). Floyd Bennett
Field is entirely on top of former saltmarsh and
estuarine beach; this artificial island now has
sandy beach along more than half of its
shoreline, although portions have a bulkhead
farther inland.280
Mud snails are common throughout this habitat,
up to the high tide mark. The snails graze on sea
lettuce and old horseshoe crab shells. Beach
wrack, consisting primarily of straw from
smooth cordgrass and common reed, with small
proportions of sea lettuce, contains insects,
isopods, and amphipods that also provide forage
for shorebirds.281 The abundance of shorebird
species is positively correlated with the
abundance of beach wrack and associated
invertebrates.282
Horseshoe crabs lay their eggs on the small
pockets of beach in the bay, many of which are
found on the bay islands. The shore of Plumb
Beach is a popular horseshoe crab nesting site.283
Diamondback terrapin also nest on sandy
habitats. Diamondback terrapins are the only
277USFWS, 1997, pp. 531-532 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
278Don Riepe, American Littoral Society. August 20, 2006 email
to E. Strange, Stratus Consulting, entitled "Notes from phone
conversation," in which he confirmed his visual observations of
intertidal beaches and shoreline armoring along Jamaica Bay as
discussed in an earlier phone call with E. Strange on August 11,
2006. (Mr. Riepe has served as director of the Northeast Chapter
of the American Littoral Society for 25 years. He is also the
organization's "Jamaica Bay Guardian," and has personally
observed most of the estuarine shores in this area.)
279Ibid.
280George Frame, personal visual observations, 2/20/07 email
(see note 251).
281Don Riepe, 2006 email (see note 278).
282Dugan et al., 2003 (see note 127).
283USFWS, 1997, p. 535 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
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[ 226 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
turtles found in brackish waters. In general,
nesting terrapins show a strong preference for
sandy back-barrier beaches compared to the
ocean-facing beaches of barrier islands.284'285 One
reason for this may be that the back-barrier
beaches are closer to the Spartinci marshes where
terrapins feed and grow.286 In Jamaica Bay,
terrapins nest in uplands, usually above the
beaches; the filled wetlands of Jamaica Bay
provide most of the nest sites for terrapins in this
area.287
Nesting and migrating shorebirds feed on the
invertebrates of the beaches in the study region.
Many of these species nest along the marine
barrier beach at Breezy Point, including the
federally threatened piping plover, the state
endangered least tern, and the state threatened
common tern. These species feed on the small
invertebrates of estuarine and ocean beaches as
well as area mudflats. Breezy Point is also a
concentration area for raptors, waterfowl, and
landbirds passing through the area. Migrating
raptors include the federally endangered
peregrine falcon and the state threatened
northern harrier and osprey.288
Because of the importance of beach species for
estuarine food webs, scientists have raised
concerns about the ecological implications of the
loss of estuarine beaches.289 In addition to the
forage provided by the abundant mud snails and
the small organisms of beach wrack, horseshoe
crab eggs are a critical food source for migrating
shorebirds.29" In addition, continued loss of the
few remaining sandy habitats in the study region
would be particularly serious for diamondback
284Roosenburg, W.M.,1991, "Nesting habitat of diamondback
terrapin: A geographic comparison," Wetland Journal 6:8-11.
285Dr. Russell Burke, 2006 email to E. Strange (personal visual
observation) (see note 226).
28oFeinberg, and Burke, 2003, "Nesting ecology and predation of
diamondback terrapins, Malaclemys terrapin, at Gateway
National Recreation Area, New York," Journal ofHerpetology
37:517-526, p. 520.
287George Frame, 2/20/07 email (personal visual observations)
(see note 251).
288USFWS, 1997, p. 536 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
289Jackson, et al., 2002 (see note 139), reviewing the findings of
J.K. Sullivan, 1994, "Habitat status and trends in the Delaware
estuary," Coastal Management 22:49-79; and Dove andNyman,
1995, pp. 441—447 (see note 14).
290Karpanty et al., 2006 (see note 160).
terrapin, which only nest in these habitats.
Because so few beaches remain, local planners
indicate that beach nourishment in the face of sea
level rise is likely for most remaining beach
habitat in this area.
Tidal Flats
Relatively few tidal flats remain along the highly
modified shorelines of the study region. There is
only a narrow band of shallow subtidal flats
along Lower Manhattan and the Battery.291
However, tidal mudflats are increasing as salt
marshes disappear.292
Large concentrations of shorebirds, herons, and
waterfowl use the shallows and tidal flats of
Piermont Marsh along the lower Hudson River
as staging areas for both spring and fall
migrations.293 Tidal flats provide substrate for
algae such as sea lettuce (Ulva lactuca), an
important food for brants.294
Tidal flats in Jamaica Bay are frequented by
shorebirds and waterfowl, and an intensive
survey of shorebirds in the mid-1980s estimated
more than 230,000 birds of 31 species in a single
year, mostly during the fall migration.295 The
most abundant shorebirds feeding on Jamaica
Bay's tidal flats in fall include plovers,
sandpipers, ruddy turnstone, sanderling, dunlin,
short-billed dowitcher, and greater yellowlegs. In
addition to these species, red knot is seen during
the spring migration. Area mudflats are also
important for waterfowl in winter.296
Inundation with rising seas will eventually make
flats unavailable to short-legged shorebirds,
291USFWS, 1997, p. 630 in Lower Hudson River Estuary,
Complex #21 (see note 172).
292
"George Frame, 2/20/07 email (personal visual observations)
(see note 251).
293USFWS, 1997, p. 633 in Lower Hudson River Estuary,
Complex #21 (discussing the ecological significance and
uniqueness of Piermont Marsh) (see note 172).
294
George Frame, 2/20/07 email (personal visual observations)
(see note 251).
295 1 9 84 study by Joanna Burger of Rutgers University, cited on p.
3 in New York State Department of State andUSFWS, 1998 (see
note 221).
29oUSFWS, 1997, p. 537 in Jamaica Bay and Breezy Point
Complex #16 (discussing the significance of Jamaica Bay, in
particular the bay islands, as a stopover site for migratory
shorebirds) (see note 172).
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[ SECTION 3.4 227 ]
unless they can shift feeding to marsh ponds and
pannes.297 At the same time, disappearing
saltmarsh islands in the area are transforming
into intertidal mudflats.298 This increases habitat
for shorebirds at low tide, but leaves less habitat
for refuge at high tide.
Shallow Nearshore Waters and
Submerged Aquatic Vegetation (SAV)
There is extensive shallow water habitat and high
biological productivity in the part of the Hudson
River from Stony Point south to Piermont Marsh,
just below the Tappan Zee Bridge in Rockland
County. This wide, shallow area is where the
estuary's seasonal (and annual) salt front occurs,
which is the area of greatest mixing of ocean and
freshwater. The salt front functions to
concentrate nutrients and plankton, resulting in a
high level of both primary and secondary
productivity. Thus, this part of the Hudson is a
major habitat area for numerous fish and bird
species. It is a major nursery area for striped
bass, white perch, tomcod, and Atlantic sturgeon
and a wintering area for the federally endangered
shortnose sturgeon. Waterfowl also feed and rest
here during spring and fall migrations. Some
SAV is also found here, dominated by water
celery, sago pondweed, and horned pondweed.299
Sea level rise will affect this productive area
through salinity changes that will influence the
composition and diversity of nearshore
vegetation and associated fauna. However,
changes in the upstream extent of the salt wedge
as a result of sea level rise have not been
analyzed, nor has anyone considered the
ecological implications of such a change.
Marsh and Bay Islands
Regionally important populations of egrets,
herons, and ibises are located on North and
South Brother islands in the East River and on
Shooter's Island, Prall's Island, and Isle of
Meadows in Arthur Kill and Kill van Kull. North
297Erwin et al., 2004, p. 901 (see note 16). (Discussing mudflats
at Forsythe National Wildlife Refuge, New Jersey, and other
northeastern Atlantic coast sites.)
298George Frame, 2/20/07 email (personal visual observation)
(see note 251).
299USFWS, 1997, p. 630 in Lower Hudson River Estuary,
Complex #21 (see note 172).
and South Brother islands have the largest black
crowned night heron colony in New York State,
along with large numbers of snowy egret, great
egret, cattle egret, and glossy ibis.300 The
population of the heronries of Shooter's Island,
Prall's Island, and Isle of Meadows, known
collectively as the Harbor Herons Complex,
constitutes about 25 percent of all nesting
wading birds in New York, New Jersey, and
Connecticut.301 The available research provides
no basis for expecting that these colonial nesting
birds could survive if these islands were
inundated.
Since 1984, an average of 1,000 state threatened
common tern have nested annually in colonies
on seven islands of the Jamaica Bay Wildlife
Refuge, including Canarsie Pol, Jo Co Marsh,
and Silver Hole Marsh, with smaller numbers at
Duck Creek Marsh, East High Meadow, Ruffle
Bar, and Subway Island. The heronry on
Canarsie Pol also supports nesting by great
black-backed gull, herring gull, and American
oystercatcher. The only colonies of laughing gull
in New York State, and the northernmost
breeding extent of this species, occur on the
islands of East High Meadow, Silver Hole
Marsh, Jo Co Marsh, and West Hempstead
Bay.302
Hoffman Island and Swinburne Island are
National Park Service properties lying off the
southeast shore of Staten Island; the former has
important nest habitat for herons, and the latter is
heavily nested by cormorants.3"3
Diamondback terrapin nest in large numbers
along the sandy shoreline areas of the islands of
Jamaica Bay, primarily Ruler's Bar Hassock.3"4
Local experts have reported observing about
3°°usfwS, 1997, p. 614 in The Narrows, Complex #20 (see note
172).
301Steinberg, N. D..T. Suszkowski, L. Clark, and J. Way, 2004,
Health of the Harbor: The First Comprehensive Look at the State
of the NY/N.T Estuary, a report to the NY/N.T Harbor Estuary
Program, Hudson River Foundation, New York, pp. 12-13.
302USFWS, 1997, p. 537 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
303
George Frame, 2/20/07 email (personal visual observation)
(see note 251).
304USFWS, 1997, p. 538 in Jamaica Bay and Breezy Point,
Complex #16 (see note 172).
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[ 228 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
2,000 females nesting in the area.3"5 Although
bay islands may offer more protection from
predators than the mainland, in recent years a
large percentage of terrapin eggs have been
depredated.3"6 Other possible causes of low egg
survivorship include so-called "root predation,"
whereby the roots of beach plants "invade" a
nest and penetrate the eggs and absorb their
nutrients.3"7
It is estimated that between 1974 andl994, the
smaller islands of Jamaica Bay lost nearly 80
percent of their vegetative cover.3"8 There has
been an accelerating trend in the loss of marsh
area, reaching an average annual rate of 18 ha
(44.5 acres) per year between 1994 and 1999.309
Further loss of bay island habitat with rising seas
could eliminate nesting sites for island-nesting
birds, having significant impacts on the
populations of these species, particularly those
with already diminished population sizes such as
the state threatened common tern. A local
terrapin expert has speculated that marsh loss,
combined with loss of beach nesting sites, could
greatly reduce the remaining local population of
diamondback terrapin.31"
305Dr. Russell Burke, 2006 email to E. Strange (see note 226).
See also Feinberg, J.A., and R.L. Burke, 2003 (see note 286), and
Ner, S.E., and R.L. Burke, n.d., Direct and indirect effects of
urbanization on diamond-back terrapins of the Big Apple:
Distribution and predation in a human-modified estuary,
Unpublished manuscript, Department of Biology, Hofstra
University, Hempstead, NY.
30oNer and Burke, n.d. (see note 305).
307Feinberg and Burke, 2003, pp. 517 and 523, and references
therein (see note 286).
308Hartig et al., 2002, p. 71 (see note 264).
Hartig et al., 2002, p. 78 (see note 264).
310Dr. Russell Burke, 2006 email to E. Strange (see note 226).
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[ SECTION 3.4 229 ]
Places Examined by this Review
Location
Specific
General
Islands and Hummocks
Nontidal Ecosystem
Tidal Marsh
Ocean Beach
Estuarine Beach
Mudflats
SAV & Other Shallow Water Habitat
Piermont Marsh
Pelham Bay
North & South
Brother Islands
East
High ,
Spring Creek\Meadow
BrookIyn\ \
'j. Canarsie
"* Pol '
Paerdegat
Basin
Four
Sparrow—
Marsh
lT Gerritsen^.
ork Creek .
Plumb
Beach
Breezy/'
Point
Jo Co
Marsh
Shooters
Island
Dubois
Point
Jamaica'
iRefugeT
Pralls
Island
Island of
Meadows
Silver
Hole
Marsh
Subwayi
Island
Ruffle,
Bar
Morgan
Beach ^ v
Middlesex Sr'
Whale
Creek
Kurihm Conaskonk
ftn / Point tCsandy
rtgl Swuh I Hook
vf vh
\Chingarora '•v ti
Creek "
Atlantic
O c e a n
Monmouth
Map 3.2 Locations and Types of Habitat Discussed in this Report: New York Harbor and Raritan
Bay
-------
3.5 Raritan Bay and the Hackensack Meadowland,
New Jersey Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats in the tidal marshes of
Raritan Bay and the Hackensack Meadowlands
are potentially at risk because of sea level rise.
Raritan Bay is part of the Raritan Bay-Sandy
Hook Bay habitat complex at the "apex" of the
New York Bight. The apex is where the east-
west oriented coastline of New England and
Long Island intersects the north-south oriented
coastline of the mid-Atlantic at Sandy Hook.
This is very significant ecologically, because the
two coastlines tend to concentrate species
migrating between the two areas.311
Based on existing literature and the knowledge
of local scientists, this brief literature review
discusses the coastal species in the region that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection (see Map 3.2). Although it is possible
to make qualitative statements about the possible
impacts if sea level rise causes a total loss of
habitat, our ability to discern what the impact
might be if only a portion of the habitat is lost is
more limited. A total loss of habitat is possible if
shores are protected with hard structures and the
wetlands are unable to keep pace with sea level
rise.
Tidal Marshes
Tidal marshes in this region are mostly estuarine
marsh or saline fringing marsh, with small areas
of freshwater tidal marsh along South River and
Raritan River. According to a panel of accretion
experts, the dominant accretionary processes in
these marshes are peat accumulation and inputs
of river sediments, both of which they anticipate
will increase in the future depending on marsh
type and local conditions.
As a result of the high productivity and the
potential for peat accumulation of tidal
freshwater marshes in the region, the accretion
panel believes that freshwater tidal marshes
along the South and Raritan rivers will
accumulate sufficient sediment to accrete and
even expand as sea level rise increases, even
with a 7 mm/yr increase in the current rate
(Section 2.1).
However, the accretion panel anticipates that
peat accumulation in estuarine and saline fringe
marsh will increase only up to a threshold level,
which is currently unknown. The panel projects
that beyond that threshold these marshes will
become marginal if the rate of sea level rise
increases by 2 mm/yr, and will not survive if the
rate increases by 7 mm/yr. Even at the modest
rate of increase of 2 mm/yr, these marshes will
be lost if hardened shorelines prevent migration
or the marshes are degraded by human activities
(see Section 2.1).
The shorelines of Raritan Bay have the most
natural estuarine and saline fringing marsh
remaining in the region. The southern portion of
Raritan Bay includes large tracts of fringing salt
marsh at Conaskonk Point and from Flat Creek
to Thorn's Creek.312 Local planners expect that
much of the region's shoreline will be protected
from sea level rise; in developed areas,
bulkheading is already common. Therefore,
migration of brackish and saline fringing marsh
will not be possible along most, if not all, of the
shoreline.
As estuarine and saline fringing marshes are lost,
there will be increasing competition for habitat
among the species found in these marshes, and
eventually all of the marsh inhabitants that
311USFWS, 1997, p. 553 in Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172).
312Ibid.
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[ SECTION 3.5 231 ]
depend on these marshes for nesting and other
critical activities will need to move to similar
habitat elsewhere to survive. Marsh loss will also
eliminate the high primary production and
detrital food web of the marsh, which are
important for secondary production throughout
the surrounding estuary.313
These marshes are critical for numerous nesting
and migrating bird species. The salt marsh at
Conaskonk Point provides breeding areas for
green heron, clapper rail, willet, American
oystercatcher, marsh wren, seaside sparrow, and
saltmarsh sharp-tailed sparrow, as well as
feeding areas for herons, egrets, common tern,
least tern, and black skimmer. In late May and
early June, sanderlings, ruddy turnstones,
semipalmated sandpipers, and red knots feed on
horseshoe crab eggs near the mouth of
Chingarora Creek.314 Diamondback terrapin feed
in the marshes and creeks in this area.315
Saltmarsh along the backside of the Sandy Hook
spit is dominated by low marsh cordgrass.316
Characteristic fauna of low marsh include
invertebrates such as ribbed mussel and marsh
fiddler crab, and resident marsh fish species such
as mummichog and sheepshead minnow.317 The
young of a number of marine fish species find
forage and protection in low marsh, including
winter flounder, Atlantic menhaden, bluefish,
and striped bass.318 Characteristic bird species of
the low marsh also inhabit the area, including
clapper rail, willet, and marsh wren.319
New Jersey's Hackensack Meadowlands, in
Hudson and Bergen counties, are renowned for
containing the largest single tract of estuarine
tidal wetland in the New York/New Jersey
Harbor Estuary.32" Before European settlement,
the area included a combination of fresh,
brackish, and saline wetlands as well as large
areas of forest. Subsequently, the Meadowlands
were dramatically altered by a variety of human
activities. Of the remaining wetlands in Hudson
and Bergen counties, only about 1,928 ha (4,763
ac) are tidal wetlands.
The tidal marshes that remain provide regionally
significant habitat for a number of federally or
state-listed species. Diamondback terrapin, a
federal species of concern, is common in the
Sawmill Wildlife Management Area.321 The
state-listed endangered least tern, black skimmer,
and pied-billed grebe use Kearney Marsh as a
feeding area.
Much of the tidal marsh of the Meadowlands are
dominated by the invasive common reed
(Phragmites), a species found in degraded
wetlands with decreased tidal flow.322 As a result
of recent restoration activities, parts of Harrier
Meadow and the Riverbend Wetlands Preserve
now support a mixture of open water and native
high saltmarsh vegetation.323
One result of sea level rise in the Meadowlands
may be conversion of some Phragmites-
dominated marshes into salt marshes dominated
by the native cordgrass, Spartina alterniflora.
This may benefit some bird species, because the
dense physical structure of Phragmites limits
access to the marsh surface by foraging
shorebirds, waders, waterfowl, and other
313Teal, 1986 (see note 10).
314Barnes, S., n.d., New Jersey Audubon Society, Sandy Hook
Bird Observatory, Guide to Birding in Raritan Bay. Available at:
http://www.niaudubon.org/Centers/SHBO/Conaskonk.html.
315USFWS, 1997, p. 556 in Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172).
31oUSFWS, 1997, p. 554 in Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172).
317USFWS, 1997, pp. 554-555 in Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172); Rader, D.N., 1984, Salt-
marsh benthic invertebrates: Small-scale patterns of distribution
and abundance, Estuaries 7(4A):413^120.
318Boesch, D.F., and R. E. Turner, 1984, "Dependence of fishery
species on salt marshes: The role of food and refuge," Estuaries
7(4A):46(M68, p. 465.
319USFWS, 1997, p. 556 in Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172).
320USFWS, 1997, p. 595 in Hackensack Meadowlands, Complex
#19 (see note 172).
321USFWS, 1997, p. 599 in Hackensack Meadowlands, Complex
#19 (see note 172).
322USFWS, 1997, p. 597 in Hackensack Meadowlands, Complex
#19 (see note 172).
323See, for example, Seigel, A., C. Hatfield, and J. M. Hartman,
2005, "Avian response to habitat restoration of urban tidal
marshes in the Hackensack Meadowlands, New Jersey," Urban
Habitats 3:87-116. Available at: http://www.urbanliabitats.org.
324Seigel et al., 2005, p. 88 and references therein (see note 323).
325
" However, George Frame, 2/20/07 email (see note 251), noted
that common reed provides habitat for some species, e.g., birds
such as red-winged blackbirds and spring peepers (Hyla cnicifer)
and other amphibians and reptiles.
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[ 232 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Estuarine Beaches
A local marine biologist with the National
Marine Fisheries Service reports that there are
small areas of estuarine beach all along the
shorelines of this region where there is no
shoreline hardening or marsh, except in low
current areas where mud flats predominate.326
Portions of the estuarine beaches of Sandy Hook
are bulkheaded or armored.327 Sandy beaches are
common along the shores of Staten Island from
Tottenville to Ft. Wadsworth, whereas hardened
shores are more common on the New Jersey side
of Raritan Bay. The southern shoreline of
Raritan Bay includes a number of beaches along
Sandy Hook Peninsula and from the Highlands
to South Amboy. There are also beaches on the
Perth Amboy side, some of which (e.g.,
Keansburg) are popular summer amusement
beach areas. Other beaches are found on some of
the shorelines around small islands within the
Shrewsbury-Navesink River system.328
The estuarine beaches in the region are
extremely important spawning areas for
horseshoe crabs, and the dry, upper beach is used
by nesting terrapins. Many other coastal birds
such as terns, gulls, and black skimmers use the
open sandy areas of beaches for resting and some
nest on the beaches as well.329 The New Jersey
Audubon Society reports that its members have
observed gulls and terns at the Raritan Bay beach
at Morgan on the southern shore, including some
rare species such as black-headed gull, little gull,
Franklin's gull, glaucous gulls, black tern,
sandwich tern, and Hudsonian godwit.33"
Recently, area beaches, especially those on
Sandy Hook Bay, have become important resting
places for several species of seals that frequent
the area during the winter.331
32oFrank Steimle, National Marine Fisheries Service marine
biologist. In July 14, 2006 email to E. Strange, Stratus
Consulting, entitled "Comments on draft report on HRE-
Hackensack/Raritan Bay," describing the area's estuarine
beaches. Frank Steimle has closely observed the New York/New
Jersey Harbor Estuary for over two decades.
327
"* George Frame, 2/20/07 email (personal visual observations)
(see note 251).
328Frank Steimle, 2006 email to E. Strange (see note 326).
329Ibid.
330Barnes, n.d., New Jersey Audubon Society (see note 314).
331USFWS, 1997, pp. 555—556 in Raritan Bay-Sandy Flook Bay
Complex, Complex #17 (see note 172).
Beaches are also important foraging grounds for
birds, especially migrating shorebirds such as
sanderlings, yellowlegs, and oystercatchers
looking for clams and other invertebrates. Red
knots, ruddy turnstones, and laughing gulls feed
on horseshoe crab eggs in the sand of area
beaches.332 Mud snails are common on estuarine
beaches, and beach wrack contains insects,
isopods, and amphipods. The abundance of
shorebird species is positively correlated with the
abundance of beach wrack and associated
invertebrates.333 Recent research indicates that
beach wrack traps horseshoe crab eggs, making
them more available for shorebirds.334
Local planners anticipate that most of the
shoreline along the beach/dune systems of
Raritan Bay and Sandy Hook are almost certain
to be protected as sea level rises. However, it is
uncertain whether beach nourishment or
shoreline armoring will be more common.
If the beaches are armored, beaches will erode
and sediments will not be available for natural
replenishment of sand,.335 This will eliminate the
beach nesting areas of terrapins and horseshoe
crabs and the forage provided to birds by small
beach organisms. The loss of horseshoe crab
eggs will be especially critical for red knot,
which feed almost exclusively on crab eggs
during their spring migration.
If beaches are nourished, their geomorphic
characteristics may be altered in ways that some
scientists believe are unsuitable for many beach
invertebrates, including horseshoe crabs.336
Sandy Hook is considered almost certain to be
protected using approaches that retain natural
shores. The Park Service is currently planning to
build a sand bypass system to replenish a narrow
section of the spit.
332Frank Steimle, 2006 email to E. Strange (personal visual
observations) (see note 326).
333Dugan et al., 2003, p. 32 (see note 127).
334Jackson et al., 2002, p. 418 (see note 139).
335Nordstrom, 2005 (see note 153).
33oJackson, et al., 2002, p. 420 (see note 139), reviewing the
findings of Nelson, W.G, 1993, "Beach restoration in the
southeastern U.S.: Environmental effects and biological
monitoring," Ocean and Coastal Management, 19:157-182, and
Rudloe, A., 1981, Aspects of the biology of juvenile horseshoe
crabs, Limulus polvphemus. Bulletin of Marine Sciences 31:125-
133.
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[ SECTION 3.5 233 ]
Tidal Flats
We have been unable to find any papers
analyzing whether the tidal flats in this region
could keep pace with accelerated sea level rise.
Therefore, in this discussion we consider the
species that would be at risk if the flats are
unable to keep pace.
The area's flats are known foraging grounds for
numerous bird species, diamondback terrapin,337
and horseshoe crabs.338 The thousands of birds
that pass through or reside in and around Raritan
and Sandy Hook bays depend on intertidal
invertebrate food resources as well as the many
small adult and juvenile fishes that feed in these
areas.
The south shore of the Raritan and Sandy Hook
bays, from the confluence of the Shrewsbury and
Navesink rivers west to the mouth of the Raritan
River, consists of a narrow band of salt marsh
habitat, tidal creek, beaches, dunes, and remnant
forests. Some 1,460 ha (3,600 acres) of intertidal
flats extend offshore from these habitats an
average of 0.4 km (0.25 miles).339 The flats are
important foraging and staging areas for
migrating shorebirds, averaging more than
20,000 birds, mostly semipalmated plover,
sanderling, and ruddy turnstone.34" Tidal flats are
also habitat for hard and soft shell clams, which
are important for recreational and commercial
fishermen where not impaired by poor water
quality.
The flats at the mouth of Whale Creek near
Pirate's Cove (see Map 3.2) attract gulls, terns,
and shorebirds year-round.341 The intertidal and
shallow water macroalgae beds provide forage
for brant and dabbling ducks.342 Midwinter
waterfowl surveys indicate that an average of
60,000 birds migrate through the area in
winter.343
Shallow Waters and Submerged Aquatic
Vegetation (SAV)
Little eelgrass is found in this region, primarily
because of poor water quality resulting from high
levels of nutrients and suspended solids.344
Therefore, in this region sea level rise is not an
impact of concern for SAV. Sea lettuce and other
algae substitute for eelgrass as an important food
for Brants and as habitat for invertebrates and
small fishes.345
337Dr. Russell Burke, email to E. Strange (personal visual
observations of terrapins) (see note 226).
338Frank Steimle, July 14, 2006 email to E. Strange (personal
visual observations of numerous species) (see note 326).
339USFWS, 1997, p. 553 in Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172).
340USFWS, 1997, pp. 553 and 556 in Raritan Bay-Sandy Hook
Bay Complex, Complex #17 (see note 172).
341Barnes, n.d. (see note 314).
342Frank Steimle, July 14, 2006 email to E. Strange (personal
visual observations) (see note 326).
343USFWS, 1997, p. 556, Raritan Bay-Sandy Hook Bay
Complex, Complex #17 (see note 172).
344USFWS, 1997, p. 559,Raritan Bay-Sandy Hook Bay Complex,
Complex #17 (see note 172).
345
George Frame, 2/20/07 email (personal visual observations)
(see note 251).
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3.6 New Jersey's Coastal Bays
Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats along the Atlantic Coast of
south-central New Jersey are potentially at risk
because of sea level rise. This region
encompasses the barrier islands, barrier spits,
and back-barrier lagoons of New Jersey's Ocean,
Atlantic, and Cape May counties. The region
contains important habitats for a wide variety of
fish, invertebrates, terrapins, and birds, and a
great deal is known about the ecology and
habitat needs of these species. Based on existing
literature and the knowledge of local scientists,
this summary discusses those species that could
be at risk because of further habitat loss resulting
from sea level rise and shoreline protection (see
Map 3.3). Although it is possible to make
qualitative statements about the ecological
implications if sea level rise causes a total loss of
habitat, our ability to say what the impact might
be if only a portion of the habitat is lost is more
limited. A total loss of habitat might be expected
if shores are protected with hard structures and
the wetlands are unable to keep pace with sea
level rise.
Ocean County has two coastal barrier islands,
Island Beach to the north and Long Beach Island
to the south. Behind these barrier islands are the
bays of the Barnegat Estuary, including Barnegat
Bay, Manahawkin Bay, and Little Egg Harbor;
three inlets; several tidal creeks; and numerous
finger canals.346 The Barnegat Bay National
Estuary Program (BBNEP) includes the
shoreline from the Point Pleasant Canal south to
the Little Egg Harbor Inlet.347
Atlantic County has the back-barrier bays and
tidal wetlands of the Brigantine Bay and marsh
complex, which extends from Little Egg Inlet
j46See USFWS, 1997, Barnegat Bay Complex, Complex #6. pp.
317-330 (see note 172).
347The website for the Barnegat Bay National Estuary Program is
http: //www.bbep. org/.
south to the Great Egg Harbor Inlet,348 and the
Great Egg Harbor Estuary349 contained within
southern Atlantic County and northern Cape
May County. Cape May County has the
important environmental areas of the Cape May
Peninsula, which include the coastal ponds of
Cape May Meadows at the tip of the peninsula
and a network of salt marsh islands and small,
shallow bays connected by a network of channels
and tidal creeks on the peninsula's Atlantic
Ocean side.35"
There have been many efforts to conserve and
restore species and habitats in the barrier island/
back-barrier lagoon system of the study region.
Some of the larger parks and wildlife areas in the
region are Island Beach State Park, Great Bay
Boulevard State Wildlife Management Area, and
the E.B. Forsythe National Wildlife Refuge
(Forsythe Refuge) in Ocean and Atlantic
counties. Parts of the Cape May Peninsula are
protected by the Cape May National Wildlife
Refuge,351 the Cape May Point State Park,352 and
TNC's Cape May Migratory Bird Refuge.353 The
peninsula is renowned as one of the primary
stopover sites for migrating birds along the U.S.
Atlantic Coast. The North Brigantine Natural
j48See USFWS, 1997, Brigantine Bay and Marsh Complex,
Complex #4. pp. 281-307 (see note 172).
j49See USFWS, 1997, Great Egg Elarbor Estuary, Complex #3.
pp. 261-268 (see note 172).
35uSee USFWS, 1997, Cape May Peninsula, Complex #1. pp.
177-195 (see note 172).
351 See http://www.fws.gov/northeast/capemav/.
352 See
http://www.state.ni.us/dep/parksandforests/parks/capemav.html.
353See
http://www.nature.org/wherewework/nortliamerica/states/newiers
ev/work/art 17205. html.
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[ SECTION 3.6 235 ]
Area is a critical nesting area for least terns and
piping plovers and a critical stopover habitat for
a number of migrating shorebirds. Corson's Inlet
State Park and Strathemere Natural Area, which
straddle Corson's Inlet, have historically
provided critical habitat area for black skimmers,
least terns, and piping plovers, and in an
important stopover habitat for migratory
shorebirds. Stone Harbor Point and Champagne
Island, part of the Hereford Inlet system, are
critical nesting areas for least terns, black
skimmers, piping plovers, common terns, and
American oystercatchers, and provide critical
resting and feeding habitat for migrating
shorebirds, including red knot. Marsh islands
behind this inlet system and behind Stone Harbor
host the largest concentration of nesting laughing
gulls in the world.354 The TNC refuge alone
supports an estimated 317 bird species, 42
mammal species, 55 reptile and amphibian
species, finfish, shellfish, and other
invertebrates.355 All of these areas are likely to be
placed at increased risk by rising sea levels.
Tidal Marshes and Nearshore Nontidal
Marshes
There are 18,440.7 ha (71.2 mi2), 29,344.6 ha
(113.3 mi2), and 26,987.7 ha (104.2 mi2) of tidal
salt marsh in Ocean, Atlantic, and Cape May
counties, respectively. Based on a review of
available studies, a panel of accretion experts
convened for this report concluded that marshes
in the study are keeping pace with current local
rates of sea level rise of 4 mm/yr, but will
become marginal with a 2 mm/yr acceleration,
and will be lost with a 7 mm/yr acceleration
except where they are near local sources of
sediments (e.g., rivers such as the Mullica and
Great Harbor rivers in Atlantic County) (see
Section 2.1).
There is potential for wetland migration in the
unprotected parts of Island Beach State Park, the
354Dave Jenkins, acting chief, New Jersey Division of Fish and
Wildlife, Endangered and Nongame Species Program, Trenton,
NJ. E-mail entitled Opportunity to comment on a US EPA-
sponsored paper concerning sea level rise, to Karen Scott of EPA,
7/18/07. (personal visual observations).
355Fact sheet by National Park Service on the New Jersey Coastal
Heritage Trail Route. Accessed December 4, 2007 at:
http://www.nps.gov/archive/neie/migsites.html.
Forsythe Refuge, and other parks and wildlife
management areas in Ocean County.356 Wetlands
may also be allowed to migrate along the
undeveloped shorelines of the Mullica and Great
Egg Harbor rivers in Atlantic County.357
However, with the exception of beaches and a
few areas such as the Forsyth Refuge, most
estuarine shorelines are hardened.358 Local
planners indicate that the developed mainland
and barrier island shorelines of Ocean, Atlantic,
and Cape May counties will almost certainly be
protected. The narrow fringing salt marshes
along protected shorelines north of Barnegat
Inlet could be lost even with a 2 mm/yr
acceleration in rate of sea level rise. Below
Barnegat Inlet natural shorelines are considered
likely to remain because the sea would have to
rise many feet before it would reach US
Highway 9.359 With continued sea level rise,
natural sedimentary processes will be
increasingly disrupted and lead to "drowning" of
marshes. Many typical back-bay areas will likely
become lakes. The invasive common reed may
spread into areas where higher sea levels cause
groundwater discharge to migrate up slope with
greater volume.36"
As marshes along protected shorelines
experience increased tidal flooding, there may be
an initial benefit to some species. This is because
as tidal creeks become wider, deeper, and more
abundant, fish species may benefit because of
increased access to forage on the marsh
surface.361 Fish species such as Atlantic
silverside, mummichog, and bay anchovy move
into the creeks during low tide, but have greater
access and are more common on the marsh
surface during high tide. Sampling of larval
fishes in high salt marsh on Cattus Island, Beach
358Stanton Hales, Richard Stockton College, Biology & Marine
Sciences Programs, Pomona, NJ. E-mail entitled Reviews of
USEPA-sponsored papers, to Karen Scott of EPA 7/25/07.
(personal visual observations).
359Ibid.
3o0Barry Truitt, The Nature Conservancy. Email entitled Review
of Atlantic coast side of the VES, to Karen Scott of EPA,
7/25/07.
3olWeinstein, M.P., 1979, "Shallow marsh habitats as primary
nurseries for fishes and shellfish, Cape Fear River, North
Carolina," U.S. Fisheries Bulletin 77:339-357.
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[ 236 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Haven West, and Cedar Run in Ocean County
showed that high marsh is important for
production of mummichog, rainwater killfish,
spotfin killifish, and sheepshead minnow. The
flooded marsh surface and tidal and nontidal
ponds and ditches appear to be especially
important for the larvae of these species.362
However, as sea levels continue to rise, and
marshes along hardened shorelines convert to
open water, marsh fishes will lose access to these
marsh features and the protection from predators,
nursery habitat, and foraging areas provided by
the marsh.
Loss of marsh area would also have negative
implications for the dozens of bird species that
forage and nest in the region's marshes. Initially,
deeper tidal creeks and marsh pools will become
inaccessible to short-legged shorebirds such as
plovers.363 Long-legged waterbirds such as
yellow-crowned night heron, which forages
almost exclusively on marsh crabs (fiddler crab
and others), will lose important food resources.
High marsh nesting birds such as northern
harrier, black rail, clapper rail, and willet may be
most at risk.364 Eventually, complete conversion
of marsh to open water will affect the hundreds
of thousands of shorebirds that stop in these
areas to feed during their migrations. The New
Jersey Coastal Management Program estimated
that some 1.5 million migratory shorebirds stop
over on New Jersey's shores during their annual
migrations.365 Waterfowl also forage and
overwinter in area marshes. Midwinter aerial
waterfowl counts in Barnegat Bay alone average
50,000 birds.366 The tidal marshes of the Cape
May Peninsula provide stopover areas for
hundreds of thousands of shorebirds, songbirds,
raptors, and waterfowl during their seasonal
3o2Talbot, C.W., and K.W. Able, 1984, "Composition and
distribution of larval fishes in New Jersey high marshes,"
Estuaries 7:434^143.
3o3Erwin et al., 2004 (see note 16).
3o4Dave Jenkins (see note 354).
3o5Cooper, M.J.P., M.D. Beevers, and M. Oppenheimer, 2005,
Future Sea Level Rise and the New Jersey Coast, Science,
Technology, and Environmental Policy Program, Woodrow
Wilson School of Public and International Affairs, Princeton
University, Princeton, NJ, p. 3, citing the New Jersey Coastal
Management Program.
3w>USFWS, 1997, Barnegat Bay Complex, Complex #6. p. 323
(see note 172).
migrations.367 The peninsula is also an important
staging area and overwintering area for seabird
populations. Surveys conducted by the U.S. Fish
and Wildlife Service from July through
December 1995 in Cape May County recorded
more than 900,000 seabirds migrating along the
coast.368
As feeding habitats are lost, local bird
populations may no longer be sustainable. For
example, avian biologists suggest that if marsh
pannes and pools continue to be lost in Atlantic
County as a result of sea level rise, the tens of
thousands of shorebirds that feed in these areas
may shift to feeding in impoundments in the
nearby Forsythe Refuge, increasing shorebird
densities in the refuge by tenfold and reducing
population sustainability because of lower per
capita food resources and disease from
crowding.369
Local populations of marsh-nesting bird species
will also be at risk where marshes drown. This
will have a particularly negative impact on rare
species such as seaside and sharp-tailed
sparrows, which may have difficulty finding
other suitable nesting sites. According to
syntheses of published studies in Greenlaw and
Rising, and Poole and Gill, densities in the
region ranged from 0.3 to 20 singing males per
hectare and 0.3 to 4.1 females per hectare for the
seaside and sharp-tailed sparrows,
respectively.37" Loss and alteration of suitable
marsh habitats are the primary conservation
concerns for these and other marsh-nesting
passerine birds.371 Nonpasserine marsh nesting
3o7See USFWS, 1997, Cape May Peninsula, Complex #1. pp.
177-195 (see note 172).
3o8USFWS, 1997, Barnegat Bay Complex, Complex #6. p. 324
(see note 172).
3o9Erwin et al., 2006 (see note 58).
370Greenlaw, J.S., and J.D. Rising, 1994, "Sharp-tailed sparrow
(Ammodramus audacutus)," in Poole, A. and F. Gill, (eds.), The
Birds of North America, No. 127, The Academy of Natural
Sciences, Philadelphia and the American Ornithologists' Union,
Washington, DC; and Post, W. and J. S. Greenlaw, 1994, Seaside
sparrow (Ammodramus maritimus), in Poole and Gill, as cited in
Chapter 6 of The Barnegat Bay Estuary Program
Characterization Report. Prepared by the Barnegat Bay National
Estuary Program (Scientific and Technical Advisory
Committee), January 2001. Available at:
http: //www. bbep. org/char_rep. htm
371Chapter 7 of The Barnegat Bay Estuary Program
Characterization Report. Prepared by the Barnegat Bay National
Estuary Program (Scientific and Technical Advisory
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[ SECTION 3.6 237 ]
birds may also be at risk, particularly high marsh
species such as northern harrier and black rail,
which are state-listed as endangered. Species that
nest in other habitat but rely on marshes for
foraging, such as herons and egrets, will also be
affected as marshes drown.
Bulkheading is also under way to protect the
vulnerable freshwater ecosystems of the Cape
May Meadows (The Meadows), which is located
behind the eroding dunes of the Cape May
Canal. Freshwater coastal ponds in The
Meadows are found within a few hundred feet of
the shoreline and therefore could easily be
inundated as seas rise. The ponds provide critical
foraging and resting habitat for a variety of bird
species, primarily migrating shorebirds.372
Among the rare birds seen in The Meadows by
local birders are buff-breasted sandpipers, arctic
tern, roseate tern, whiskered tern, Wilson's
phalarope, black rail, king rail, Hudsonian
godwit, and black-necked stilt.373 Because of its
vulnerability to sea level rise and its status as an
ecologically important area, local planners
expect that The Meadows will continue to be
protected in the future.
Estuarine Beaches
Estuarine beaches could largely disappear as a
result of erosion and inundation of sandy habitat
as seas rise. This would eliminate the billions of
invertebrates that are found within or on the
sandy substrate or beach wrack along the tide
line of estuarine beaches.374 These species
provide a rich and abundant food source for bird
species. Small beach invertebrates include
isopods and amphipods, blood worms, and beach
hoppers, and beach macroinvertebrates include
soft shell clams, hard clams, horseshoe crabs,
Committee), January 2001. Available at:
http://www.bbep.org/char rep.htm/Ch7/Chapter%207.htm.
372 Fact sheet by New Jersey Department of Environmental
Protection on Cape May Point State Park. Accessed December 5,
2007 at:
http://www.state.ni.us/dep/parksandforests/parks/capemav.html.
373Fact sheet by Paul Kerlinger, Outdoors Columnist, entitled
"Birding, The Cape May Migratory Bird Refuge." Accessed
December 5, 2007 at:
http://www.capemavtimes.com/birds/capemav-meadows.htm.
374 Bertness, 1999, pp. 256-257, gives an estimate of more than 2
billion microscopic invertebrates per square meter (see note 133).
fiddler crabs, and sand shrimp (see details in
Section 3.1).
To protect estuarine beaches, beach nourishment
is being implemented in developed portions of
the Ocean County shore, particularly in the
northern part, while bulkheading continues to be
used on the bayside shores of the county. TNC,
the U.S Army Corps of Engineers (USACE), and
the New Jersey Department of Environmental
Protection (NJDEP) are undertaking beach
replenishment to protect a mile-long stretch of
sandy beach found in the Cape May Migratory
Bird Refuge that provides nesting habitat for the
rare piping plover and least tern.375
Loss of horseshoe crab eggs as a result of beach
erosion or beach nourishment could have
important implications for the 1.5 million
migratory shorebirds that stop over on New
Jersey's shores to refuel during their annual
migrations.376 Many shorebirds feed
preferentially on horseshoe crab eggs in spring
(e.g., red knot), 377 378 and loss of this food source
could reduce the growth and survival of migrants
if there are insufficient alternative foraging sites
nearby.379 Sanderling, red knot, and ruddy
turnstone prefer sandy beaches for foraging.380 In
spring these migrants must feed nearly
continuously to gain sufficient weight for nesting
and to continue their long-distance migrations.381
Northern diamondback terrapin nests on
estuarine beaches in the Barnegat Bay area.382
Loss of these habitats will make terrapins even
more dependent on areas modified by humans
(roadways). Local scientists consider coastal
375Fact sheet by The Nature Conservancy on the Cape May
Migratory Bird Refuge. Accessed December 5, 2007 at:
http://www.nature.org/wherewework/nortliamerica/states/newiers
ev/work/art 17205. html.
37°Cooper et al., 2005, p.3, citing the New Jersey Coastal
Management Program (see note 365).
377USFWS, 2005 (see note 232).
378Karpanty et al., 2006 (see note 160).
379Although in spring the principal food source of shorebirds is
typically horseshoe crab eggs, the BBNEP reports that in
Barnegat Bay shorebirds feed on invertebrates in marsh mudflats
and beaches. See Chapter 7 of The Barnegat Bay Estuary
Program Characterization Report (see note 371).
380Chapter 7 of The Barnegat Bay Estuary Program
Characterization Report (see note 371).
38'USFWS, 2005 (see note 232).
382Chapter 7 (and references therein) of The Barnegat Bay
Estuary Program Characterization Report (see note 371).
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[ 238 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
development, which destroys terrapin nesting
beaches and access to nesting habitat, one of the
primary threats to diamondback terrapins, along
with predation, roadkills, and crab trap
bycatch.383
Loss of estuarine beach could also have negative
impacts on rare tiger beetles. Two subspecies of
Cicindela dorsalis are found on New Jersey's
coastal shoreline: the northeastern beach tiger
beetle, C. dorsalis dorsalis, which is a federally
listed threatened species and a state species of
special concern and regional priority, and C.
dorsalis media, which is considered rare, though
it has not been considered for state listing. In the
mid-1990s, the northeastern beach tiger beetle
was observed on the undeveloped ocean beaches
of Holgate and Island Beach. The USFWS does
not know whether this species is also found on
the area's estuarine beaches, but studies indicate
that it feeds and nests in a variety of habitats.384
The current abundance and distribution of the
northeastern beach tiger beetle in the coastal
bays is a target of research.385 At present, there
are plans to reintroduce the species in the study
region at locations where natural ocean beaches
remain.386
Tidal Flats
The tidal flats of New Jersey's back-barrier bays
are critical foraging areas for hundreds of species
of shorebirds, passerines, raptors, and waterfowl.
Tidal flats are found in almost all of the coastal
bays, and support invertebrates such as insects,
worms, clams, and crabs that provide an
important food source for these and other birds
that forage in the study region. Some shorebirds
such as semipalmated sandpiper, dunlin, and
383See the website of the Wetlands Institute's terrapin
conservation program at http: //www.terrapinconservation. org.
384USFWS, 1997, Barnegat Bay Complex, Complex #6, pp. 317—
330 (see note 172).
385State of New Jersey, 2005, New Jersey Comprehensive
Wildlife Conservation Strategy for Wildlife of Greatest
Conservation Need, August 2005 Draft, Table CI, p. 61,
available at:
http://www.nifishandwildlife.com/ensp/waphome.htm.
38oState of New Jersey, 2005 (see note 385).
dowitcher forage preferentially on mudflats and
shallow impoundments.387
Important shorebird areas in the study region
include the flats of Great Bay Boulevard Wildlife
Management Area, North Brigantine Natural
Area, and the Brigantine Unit of the Forsythe
Refuge.388'389 The USFWS estimates that the
extensive tidal flats of the Great Bay alone total
1,358 ha (3,355 acres). Inundation of tidal flats
with rising seas would eliminate critical foraging
opportunities for the area's abundant avifauna.
As tidal flat area declines, increased crowding in
remaining areas could lead to exclusion and
mortality of many foraging birds.39"'391 Some
areas may become potential sea grass restoration
sites, but whether or not "enhancing" these sites
as eelgrass areas is feasible will depend on their
location, acreage, and sediment type.392
Shallow Nearshore Waters and
Submerged Aquatic Vegetation (SAV)
The Barnegat Estuary is distinguished from the
lagoons to the south by more open water and
SAV and less emergent marsh. Within the
Barnegat Estuary, dense beds of eelgrass are
found at depths under 1 meter (3.28 feet),
particularly on sandy shoals along the backside
of Long Beach Island and Island Beach, and
around Barnegat Inlet, Manahawkin Bay, and
Little Egg Inlet. Eelgrass is relatively uncommon
from the middle of Little Egg Harbor south to
Cape May,393 particularly locations where water
depths are above 1 meter (3.28 feet), such as
portions of Great South Bay.394
Seagrass surveys from the 1960s through the
1990s revealed an overall decline in seagrass in
Barnegat Estuary from 6,823 ha (16,847 acres) in
387Chapter 7 of The Barnegat Bay Estuary Program
Characterization Report (see note 371).
j88See USFWS, 1997, Barnegat Bay Complex, Complex #6, p.
317 (see note 172).
USFWS, 1997, Brigantine Bay and Marsh Complex, Complex
#4, p. 281 (see note 172).
390Galbraith et al., 2002, p. 173 (see note 50).
391Erwin et al., 2004, p. 892 (see note 16).
392 Stanton Hales (expert judgment based on a career largely
devoted to these issues) (see note 358).
393USFWS, 1997, Barnegat Bay Complex, Complex #6. pp. 317—
330 (see note 172).
j94USFWS, 1997, Mullica River-Great Bay Estuary, Complex
#5. pp. 295-307 (see note 172).
-------
[ SECTION 3.6 239 ]
a 1968 survey to an average of 5,677 ha (14,029
acres) of seagrass beds from 1996 to 1998.395-396
Numerous studies indicate that eelgrass has high
ecological value as a source of both primary397
and secondary production398 in estuarine food
webs. In Barnegat Estuary eelgrass beds provide
habitat for invertebrates, birds, and fish that use
the submerged vegetation for spawning, nursery,
and feeding habitat. In addition, many species
graze on eelgrass, including gastropods, fishes,
ducks, and muskrats.399
Short and Neckles suggested that a 50 cm (19.7
in.) increase in water depth as a result of sea
level rise could reduce the light available for
eelgrass photosynthesis by 50 percent, resulting
in a 30-40 percent reduction in seagrass growth.
The researchers suggested that this will, in turn,
result in reduced productivity and functional
values of eelgrass beds.4""
Results of a study in Barnegat Bay indicated that
shoreline protection may exacerbate this
problem. The study found that where shorelines
are bulkheaded, SAV, woody debris, and other
features of natural shallow water habitat are rare
or absent. These bulkheaded areas have reduced
abundances of fishes compared to sites that were
not bulkheaded sites.4"1
The Barnegat Estuary has 14 yacht clubs, with 4
on Long Beach Island alone. Sailing and sailboat
racing are less popular in Atlantic and Cape May
395Chapter 7 of The Barnegat Bay Estuary Program
Characterization Report (see note 371).
390According to an 7/21/06 email to E. Strange, Stratus
Consulting, from Dr. Paul A. X. Bologna of the Department of
Biology and Molecular Biology at Montclair State University,
Dr. Bologna has conducted SAV monitoring in the Barnegat
Estuary since 1998, but these data are not yet analyzed.
397Thayer, G.W., W..T. Kenworthy, and M.S. Fonseca, 1984, The
Ecology of Eelgrass Meadows of the Atlantic Coast: A
Community Profile, U.S. Fish and Wildlife Service, FWS/OBS-
84/02.
398Jackson, E.L., A.S. Rowden, M..T. Attrill, S. Bossey, and M.
Jones, 2001, Hie importance of seagrass beds as habitat for
fishery species, Oceanography and Marine Biology Annual
Review 39:269-303.
399Chapter 7 of The Barnegat Bay Estuary Program
Characterization Report (see note 371).
400Short and Neckles, 1999 (see note 91).
401Byme, 1995 (see note 112).
counties, 402 with their relatively small and
shallow bays. One possible benefit of the
conversion of marsh to open water would be
increased recreational sailing in the larger barrier
bays that might form. On the other hand, deeper
water would make Little Egg Harbor Bay less
hospitable to windsurfing.4"3
Marsh and Bay Islands
Large bird populations are found on marsh and
dredge spoil islands of the back-barrier bays in
the study region. These islands include nesting
sites protected from predators for several species
of conservation concern, including gull-billed
tern, common tern, Forster's tern, least tern,
black skimmer, American oystercatcher, and
piping plover. Diamondback terrapin, a state
species of special concern and a regional
priority, is also known to feed on marsh islands
in the bays.4"4
Some of the small islands in Barnegat Bay and
Little Egg Harbor are several feet above mean
spring high water,4"5 but portions of other islands
are very low, and some low islands are currently
disappearing. Many of these vulnerable islands
are used by nesting common terns, Forster's
terns, black skimmers, and American
oystercatchers.4"6 With the assistance of local
governments, the Mordecai Land Trust is
actively seeking grants to halt the gradual
erosion of Mordecai Island, a 45-acre island just
west of Beach Haven on Long Beach Island.
Members of the land trust have documented a 37
percent loss of island area since 1930. The
island's native salt marsh and surrounding waters
and SAV beds provide habitat for a variety of
aquatic and avian species. NOAA Fisheries
considers the island and its waters essential fish
402Of 32 yacht clubs in New Jersey, 14 are in Ocean County, and
6 are in Atlantic and Cape May counties combined. The other 12
are evenly divided between Delaware River, Monmouth County,
and North Jersey. Don Robertson's Marine Marketplace: Yacht
Clubs with Web Sites. Available at:
http://www.vachtsales.com/vclubs/ni.html.
403Titus, J., 1998, Windsurfing in a wanner world, Windsurfing
Magazine, March (Windsurfing is more convenient when water is
3^1 ft deep than when over one's head.)
404USFWS, 1997, Barnegat Bay Complex, Complex #6. pp. 317—
330 (see note 172).
405
Personal visual observation by James G. Titus, U.S. EPA.
400 Dave Jenkins (personal visual observation) (see note 354).
-------
[ 240 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
habitat for spawning and all life stages of winter
flounder as well as juvenile and adult stages of
Atlantic sea herring, bluefish, summer flounder,
scup, and black sea bass.4"7 The island is also a
strategically located nesting island for many of
New Jersey's threatened and endangered species,
and it contains a moderate-size black skimmer
colony, common terns, and most recently, a very
small colony of royal terns.4"8
4u7Mordecai Land Trust web site, available at:
http: //www, mordecaimatters. org.
408Dave Jenkins (personal visual observation) (see note 354).
-------
[ SECTION 3.6 241 ]
Map 3.3 Locations and Types of Habitat Discussed in this Report: New Jersey Shore
-------
3.7 Delaware Bay
Authors: Danielle Kreeger, Partnership for the Delaware Estuary Inc., and
James G. Titus, U.S. Environmental Protection Agency
Delaware Bay is part of the larger Delaware
Estuary Ecosystem, the second largest estuary in
North America and home to hundreds of species
of ecological, commercial, and recreational
value. Unlike other estuaries in the Mid-Atlantic,
the Delaware estuary's tide range is greater than
the ocean tide range, generally about 2 meters.
Beaches account for 52 percent of the bay's
shore, with marsh and eroding peat accounting
for most of the remainder4"9
This brief literature review discusses species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection.
Tidal Marshes
Much of the land along Delaware Bay, and for
several kilometers inland, is tidal wetland (see
Map 3.4). The Delaware Estuary has one of the
largest freshwater tidal prisms in the world. As
result, the tidal wetlands vegetation must be
adapted for a wide range in salinity. Delaware
Bay and its tributary creeks have tidal
freshwater, brackish, and salt marshes. These
wetlands are characterized by zones of different
vegetation types, which reflect small differences
in topography and tidal flooding regimes. All
three classes are essential habitat for wildlife,
waterfowl, fish, and other living resources.
In the salt marshes fringing Delaware Bay, the
low marsh is flooded at least once daily and is
4ll9Lathrop, R., M. Allen, and A. Love, 2006, Mapping and
Assessing Critical Horseshoe Crab Spawning Habitats in
Delaware Bay, Grant F. Walton Center for Remote
Sensing and Spatial Analysis, Cook College, Rutgers
University, p. 15, Table 8, accessed on November 15, 2006
at:_http://deathstar.rutgers.edu/projects/delbay/.
generally found between the mean tide level and
mean high water. The bay's low marsh is
dominated by smooth cordgrass, Spcirtinci
alterniflora. The less frequently flooded high
marsh zone has higher plant diversity, and
typically includes Spartinapatens, Iva
frutescens, and Baccharis halimifolia. High
marsh is less common than low marsh and is
likely to be much more vulnerable to sea level
rise. Black rail and the coastal plain swamp
sparrow depend on high marsh habitat. Almost
the entire breeding range of the coastal swamp
sparrow is in the Delaware Estuary.
Historically, much of the bay's shoreline was
diked to reclaim wetlands for farming. However,
in recent decades, dikes have been removed to
support wetland restoration.41" At the same time,
there has been an expansion of the common reed,
Phragmites australis, at higher elevations and in
many of the formerly diked areas.411 Marsh areas
dominated by common reed are thought to
provide lower quality wildlife and fishery habitat
compared to natural cordgrass marshes.412
41"See Weinstein, M.P., K.R. Philip, and P. Goodwin,
2000, "Catastrophes, near-catastrophes and the bounds of
expectation: Success criteria for macroscale marsh
restoration," in Concepts and Controversies in Tidal
Marsh Ecology, M.P. Weinstein and D. A. Kreeger (eds.),
Kluwer Academic Publishers, Dordrecht, The Netherlands,
pp. 777-804; and Able, K.W., D.M. Nemerson, P.R. Light,
and R.O. Bush 2000, "Initial response of fishes to marsh
restoration at a former salt hay farm bordering Delaware
Bay," in Weinstein and D.A. Kreeger, pp. 749-776.
411 Ibid.
412Philip, K, 1995, Tidal Wetlands Characterization-
Then and Now. Delaware Estuary Program, Final Report
to the Delaware River Basin Commission.
-------
[ SECTION 3.7 243 ]
Geomorphic Setting
Back barrier lagoon, other
Back barrier lagoon, flood tidal delta
Back barrier lagoon, lagoonal fill
Estuarine marsh
Estuarine, fringe
Estuarine, meander
Saline fringe
Tidal fresh forest
Tidal fresh marsh
Delaware
Bay
Map 3.4. Tidal Wetlands Along the Delaware Estuary. Source: Titus et al. (Section 2.2), using science
assessment of Reed et al. (Section 2.1).
-------
[ 244 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Can Marshes Keep Pace with Rising Sea Level?
The sustainability of tidal marshes in response to
relative sea level rise depends on the supply of
sediment and organic matter to raise the marsh
surface, the tide range, and the ability of
wetlands to migrate inland, which depends on
both the slope of the nearby lowland and whether
people allow the wetland migration or block it
with shore protection (Section 2.1). The 2 meter
daily tide range enables low and high marsh to
each subsist over an elevation range of close to 1
meter. Hence it would take a 1 meter rise to
submerge all the existing low marsh, or to flood
all of the existing high marsh at the frequency
that defines low marsh. In much of Delaware
Bay, however, tidal marshes appear to be at the
low end of their potential elevation range,
increasing their vulnerability.413 Unlike the
marshes along the back-barrier bays of Delaware
and New Jersey, the tidal marshes of Delaware
Bay grow upward primarily through the
accretion of organic matter, not sediment.
Evidence of wetland loss can be seen in many
areas, such as just inside the mouth of the
Maurice River near Port Norris, New Jersey (see
Map 3.4). In this location, the effects of sea level
rise appear to be acting synergistically with
increased erosive energy to lead to significant
marsh losses over the past 100 years. One
contributing factor here might have been the loss
of the oyster reefs near the mouth during the
1950s and 1960s, which might have afforded
some protection against storm surge and wave
energy. Today, the energy from winter
Nor'easters and other storms directly enters the
mouth, eroding at the marsh edge across a new
embayment and threatening to breach to the river
upstream of the town of Bivalve.414 This idea is
attracting some interest as a possible strategy for
combating shoreline erosion by restoring
nearshore reefs in concert with rehabilitating
intertidal mussel and oyster communities along
413Kearney, M.S., A.S. Rogers, J.R.G. Townsend, E.
Rizzo, D. Stutzer, J.C. Stevenson, and K. Sundborg, 2002,
"Landsat imagery shows decline of coastal marshes in
Chesapeake and Delaware bays," Eos 83( 16): 173.
414This case demonstrates how the effects of sea level rise
must be considered in a local context that considers
multiple physical and ecological factors.
marsh edges as a form of natural armoring.
Nevertheless, it is unlikely that such efforts will
be widespread enough to ensure that all tidal
wetlands accrete vertically at a rate to offset sea
level rise, and seaward losses of marsh are
certain to continue. In other areas of Delaware
Bay, wetlands do not appear to be vanishing as
quickly or at all, and so one must consider the
possibility that some wetlands will keep pace
with rising sea level but others will not.
Considering these factors, Reed et al. (Section
2.1) concluded that with a 2 mm/yr acceleration
in sea level rise, most of the Delaware Bay
wetlands would be marginal, and that the
wetlands will probably convert to open water
along Bombay Hook National Wildlife Refuge
on the Delaware side, and between Fortescue and
the Salem Nuclear Generating Station on the
New Jersey side (see Map 3.5).
Can Wetlands Migrate Inland as Sea Level
Rises?
As a general rule, where the bay's shoreline is
armored, the landward migration of the marsh
will be impeded. Along Delaware Bay, most of
the shore is undeveloped and unlikely to be
armored. Each acre of land submerged, however,
would not necessarily correspond to an acre of
increased wetland habitat: landward migration of
tidal wetlands would occur at the expense of
existing nontidal wetlands along much of the
shore. Moreover, no one has established that the
tidal inundation of the freshwater wetlands
would lead to creation of salt marsh; in many
areas such inundation converts the wetlands to
open water instead.
The Partnership for the Delaware Estuary is
directing attention to the landward fringe of tidal
wetlands, where conversion of nontidal natural
lands to tidal natural lands appears imminent and
important to safeguard against further losses of
tidal wetlands. The Partnership (a National
Estuary Program) is currently leading an
assessment of land use patterns in the landward
buffers adjacent to tidal wetlands to identify
locations where landward migration of tidal
-------
[ SECTION 3.7 245 ]
Will Wetlands Be Converted to Open Water?
Rate of
Sea Level Rise
Current rate
Yes
?
?
No
No
No
No
Current + 2 mm/yr
Yes
Yes
Yes?
7
No
No
No
Current + 7 mm/yr
Yes
Yes
Yes
Yes
Yes
Yes?
No
? = Wetlands would be marginal Yes? - Wetland would be marginal or lost
X
T
/
Pennsylvania r* ? ^ *>
^ - '/ ^1
|r I
VJVMrt*"** -
New Jersey
Map 3.5. Potential for Tidal Wetlands along the Delaware Estuary to Keep Pace as Sea Level Rises.
Source: Titus et al. (Section 2.2), using science assessment of Reed et ai. (Section 2,1)
-------
[ 246 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
marshes might be encouraged, such as
undeveloped agricultural lands and natural
woodlands.
Implications of Habitat Change
The loss of tidal marsh as sea level rises would
harm species that depend on these habitats for
food, shelter, or spawning and nursery habitat,
including macroinvertebrates, finfish, and
wintering waterfowl. Although effects on marsh
biota have not been studied directly, current
understanding of marsh ecology suggests that
changes within the marsh will affect the ecology
of not only the marsh itself but also the entire
estuary.415
Many bird species use or depend on these
marshes, including great blue herons, black duck,
blue and green-winged teal, northern harrier,
osprey, rails, red winged blackbirds, widgeon,
and shovelers. Aquatic species such as
diamondback terrapin, blue crab, killifish,
mummichog, perch, weakfish, flounder, bay
anchovy, silverside, herring, and rockfish rely on
tidal marshes for a nursery area or for feeding on
mussels, fiddler crabs, and other invertebrates.416
Research indicates that fishes and birds feeding
in the marsh are critical for the export of marsh
production to the wider estuarine food web.417
Any reduction of cordgrass habitat would
probably reduce populations of the important
macroinvertebrate species. Macroinvertebrates
associated with cordgrass stands in the low
intertidal include grass shrimp, ribbed mussel,
coffee-bean snail, and fiddler crabs.418 Blue crab,
sea turtles, and shorebirds are among the many
415Kneib, R.T., 2000, "Salt marsh ecoscapes and
production transfers by estuarine nekton in the
southeastern United States," in Weinstein and Kreeger, pp.
267-292 (see note 410).
416See Dove and Nyman, 1995 (see note 14).
417Deegan, L.A., J.E. Hughes, and R.A. Rountree, 2000,
"Salt marsh ecosystem support of marine transients," in
Weinstein and Kreeger, pp. 333-368 (see note 410); and
Kneib, 2000 (see note 415).
418Kreamer, 1995, pp. 81-90 (see note 19); and Kreeger,
D. A. and R. I. E. Newell, 2000, "Trophic complexity
between primary producers and invertebrate consumers in
salt marshes," Chapter 11 in Weinstein and Kreeger, pp.
183-216 (see note 410).
species that prey on ribbed mussels; fiddler crabs
are an important food source for bay anchovy
and various species of shorebirds.419 In turn, the
depletion of these organisms would reduce the
numbers of marsh birds. Wading birds such as
the glossy ibis feed on marsh invertebrates42"
Waterfowl, particularly dabbling ducks, use low
marsh areas as a wintering ground. The black
duck is already in decline, and is considered a
species of special concern by EPA's Delaware
Estuary Program.421 The winter snow goose
population in the bay is currently the largest
population in the eastern flyway, and a primary
source of food for snow geese is the root system
of the smooth cordgrass.422 Diamondback
terrapin, listed as a species of conservation
concern by the Northeast Regional Technical
Committee and as a species of greatest
conservation need in Delaware's Wildlife Action
Plan, would also be impacted both by loss of
wetlands, which are nursery areas for young
turtles, and by loss of nesting beaches.
Tidal creeks and shallow water areas of the low
marsh provide spawning and nursery areas for
finfish that are seasonal residents, year-round
residents, and transients from the wider estuary
that enter tidal marshes only periodically. The
most common fish species of the marsh are
mummichog, spot, white perch, Atlantic
menhaden, Atlantic silverside, bay anchovy, and
sheepshead minnow.423 The abundance of these
species may be affected not only by a loss of
habitat but also by reductions in invertebrate
food supplies.
High marsh is an important habitat for raptors
such as the short-eared owl and for various
species of songbirds that breed or pass through
the high marsh during their migrations to
northern breeding areas.424 Seaside sparrows are
characteristic of cordgrass areas, and sharp-tailed
sparrows are more common in upland areas
dominated by salt hay.425 If marsh migration is
Kreamer, 1995, pp. 81-90 (see note 19).
42"See Dove and Nyman, 1995 (see note 14).
421 Ibid.
422Ibid.
423Rountree and Able, 1992 (see note 22).
424See Dove and Nyman, 1995 (see note 14).
425Ibid.
-------
[ SECTION 3.7 247 ]
impeded by shoreline protection structures and
the area of high marsh is reduced, birds of the
high marsh will decline and species already in
low numbers may be lost.
Beaches
Sandy beaches and foreshores account for 54
percent of the Delaware and New Jersey shores
of Delaware Bay, respectively (see Table 3.1).
Table 3.1 shows additional estimates of the
status of the bay's shoreline, with an emphasis
on the vulnerability of beach habitat. As sea level
rises, beaches can be lost if shores are armored
or if the land behind the existing beach has too
little sand to sustain a beach as the shore
retreats.426 So far, only 4-6 percent of the natural
shore had been replaced with shoreline armoring.
Another 15 and 4 percent of the shore is
developed. However, planners expect that
approximately half of (nonwetland) shores will
eventually require some sort of shore protection.
Although conservation areas encompass 58
percent of Delaware Bay's shores, they include
only 32 percent of beaches that are optimal or
suitable habitat for horseshoe crabs.
Many Delaware Bay beaches have a relatively
thin veneer of sand. Although these small
beaches have enough sand to protect the marshes
immediately inland from wave action, there is
some question about whether some beaches
would survive accelerated sea level rise even
without shoreline armoring.
Beach nourishment has been relatively common
along the developed beach communities on the
Delaware side of the bay. Although beach
nourishment can diminish the quality of habitat
for horseshoe crabs, nourished beaches are more
beneficial than armored shores. In a few cases,
Delaware has nourished beaches with the
primary purpose to restore horseshoe crab
habitat.427
he loss of Delaware Bay's beaches would harm
horseshoe crabs, migratory birds, and other
wildlife. For example, on their annual migrations
from South America to the Arctic, nearly a
million shorebirds move through Delaware Bay,
where they feed heavily on infaunal benthic
invertebrates in tidal mudflats (see subsequent
discussion) and particularly on horseshoe crab
eggs on the bay's sandy beaches and
foreshores.428 The Delaware Estuary is home to
the largest spawning population of horseshoe
crabs in the world, and although these animals
can lay eggs in tidal marshes, their preferred
nesting sites are the mid- and high intertidal
zones of sandy beaches. Map 3.6 depicts the
suitability of the Delaware Bay shore for
horseshoe crab habitat. A sea level rise modeling
study estimated that a 2-ft rise in relative sea
level over the next century could reduce
shorebird foraging areas in Delaware Bay by 57
percent or more by 2100,429 with likely impacts
to horseshoe crabs as well. If these foraging
habitats are lost and prey species such as
horseshoe crab decline, there could be substantial
reductions in the numbers of shorebirds
supported by the bay.43"
Numerous other animals rely on the sandy
beaches of Delaware Bay to lay eggs or forage
on invertebrates such as amphipods and clams.
These include diamondback terrapins, Kemp's
and Ridley sea turtles, red fox, raccoons, and
opossum. When tides are high, numerous fish
also forage along the sandy beaches, such as
killifish, mummichogs, rockfish, perch, herring,
silversides, and bay anchovy.
Tidal Flats
Areas of exposed tidal flats in Delaware Bay
occur between mean sea level (MSL) and mean
low water, and extend primarily along the bay's
shorelines. Intertidal flats are known to be
important foraging areas for finfish as
426Cites in Nordstrom, 2005 (see note 153).
427See, e.g.. Smith et al., 2002 (see note 155).
428Smithet al., 2002 (see note 155).
429Galbraith et al., 2002 (see note 50).
43"lbid.
-------
[ 248 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Table 3.1: The Shores of Delaware Bay: Habitat Type, Likelihood of Shore Protection, and
Conservation Status of Shores Suitable for Horseshoe Crabs
1 Shoreline Length
Delaware
New Jersey
NJ+DE 1
...by Habitat Type (percentage of bay shoreline)3
km
%
km
%
%
Beach 68
74
62
42
54
Armored Shore 3.7
4
8.3
6
5
Organic 20
Total Shoreline 91
22
100
78
148
53
100
41
100
...by Indicators of Future Shore Protection
Protection Structures set back from shore3 2.7
2.9
5.1
3.4
3
Development3 13
15
5.7
3.8
8
...by Likelihood of Shore Protection (percentage of nonwetland shores)
Shore Protection Almost Certain 35
45
17
29
39
Shore Protection Likely 4
5
3
5
5
Shore Protection Unlikely 17
22
18
31
26
No Shore Protection 21
27
20
34
30
...by Suitability for Horseshoe Crab (percentage of bay shoreline)
Optimal Habitat 31.3
34
26.0
18
24
Suitable Habitatb 10.5
12
5.1
3.5
6.6
Less Suitable Habitatb 29.0
32
49.0
33
33
Unsuitable Habitatb 20.0
22
67.0
46
37
... Within Conservations Lands by Suitability for Horseshoe Crab (percentage of equally suitable lands)
Optimal Habitat0 12.9
41
9.6
37
39
Optimal and Suitable Habitat0 13.6
33
9.8
32
32
Optimal, Suitable, and Less Suitable Habitat0 32.2
46
43.3
54
50
All Shores0 44.7
49
92.7
63
58
a Delaware and New Jersey results from Lathrop et al., Table 8 (see text note 409).
b Delaware and New Jersey results from Lathrop et al. (see text note 409) at p.16, Table 9. "Unsuitable"
includes both "avoided" and "disturbed."
c From Lathrop et al. (see text note 409) at p.18, Table 1. Lathrop et al. report results for the categories
separately; we aggregate the categories.
well as migrating shorebirds, including red knot,
ruddy turnstone, sanderling, and semipalmated
sandpiper.431 Although the benthic ecology of the
system is poorly described, rich mudflat
communities of polychaetes and bivalves are
thought to sustain blue crabs, grass shrimp,
killifish, mummichogs, rockfish, perch, herring,
bay anchovy, skates, rays, black ducks, blue and
green-winged teal, mallards, northern harriers,
rails, and great blue herons. These communities
are characteristic of the lower estuary region and
Delaware Bay where salinities are greater than
about 10 ppt. In the lower salinity areas,
polychaetes are replaced with oligochaetes on
the mudflats. At low tide, numerous mammals
forage on mudflats, such as muskrat, opossum,
raccoon, and red fox. Beyond their trophic roles,
the ecological importance of these shallow
subtidal and intertidal habitats is not well
understood in the Delaware Estuary, where little
research and assessment has been devoted to
aquatic bottom habitats.432 The greatest loss of
mud flats generally occurs where migration is
prevented by the presence of shore protection
structures. In the Delaware Estuary, extensive
mudflats exist in many areas, particularly along
sections of the Delaware coastline and within
some of the larger marshland tracts in New
Jersey.
Dove and Nyman, 1995 (see note 14).
"Kreeger, D.. R. Tudor, J. Sharp, S. Kilham, D. Soeder,
M. Maxwell-Doyle, J. Kraeuter, D. Frizzera, J. Hameedi
and C. Collier,. 2006, White Paper on the Status and Needs
of Science in the Delaware Estuary, Partnership for the
Delaware Estuary Report #06-01, 72 pp. Accessed on
November 2, 2006 at
http://www.delawareestuary.org/scienceandresearcli/datase
tsandreports/localandregional.asp.
-------
[ SECTION 3.7
c\
New Jersey
A*«. .
\
\
%.
Delaware >
Habitat Zones
Delaware
Bay
Optimal: undisturbed sand beach;
Suitable: sand beach with only small areas of peat and/or backed
by development;
Less Suitable: exposed peat in the lower and middle iritertidal zone
and sand present in the upper intertidal;
Avoided: exposed peat or active salt marsh fringing the
shoreline.no sand present;
Disturbed: due to beach fill, riprap or bulkheading.
B
,4*
i
0 5 10 Kilometers
1 i I
N
A
Protected Lands
Federal
State
Hon-Gov ei ii mental
Oiganization
Public Utility
Map 3.6. Delaware Bay Shore: Conservation Status and Suitability for Horseshoe Crabs
Source: Lathrop et al. (see text note 409).
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[ 250 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Shallow Waters
Although the direct effect of sea level rise will
be to deepen these waters, shallow water
habitat may increase if wetlands convert to
open water. Therefore, we cannot currently
say whether this type of habitat will increase
or decrease.
Even if we knew the direction of change, the
resulting impacts on the fish and shellfish of
Delaware Bay have not been studied.
Nevertheless, many of the finfish and shellfish
species of nearshore waters and the shore zone
are well known, and habitat changes and loss
of habitat area affect species distribution,
diversity, and abundance. One of the best
known and most popular species of the
nearshore waters is the blue crab, Callinectes
sapidus. Another signature species in the
shallow waters of the Delaware Estuary is the
eastern oyster, Crassostrea virginica. It is not
clear how sea level rise might affect these
animals, but in the case of oyster reefs there is
some concern that natural reef-building is not
occurring fast enough to sustain population
losses from a variety of other factors.433
De Sylva et al. conducted an extensive survey
of finfish in the Delaware Estuary, and found
that bay anchovy, alewife, Atlantic menhaden,
striped bass, hogchoker, and Atlantic croaker
use these shallow waters as a nursery area.434
Other species, including blueback herring,
mummichog, banded killifish, silverside, and
white perch, spawn in these nearshore areas
and move in and out of tidal marshes.
Blueback herring spawn in shallow waters of
creeks over sand or gravel substrate. The
ocean-going bluefish moves into the bay in
summer, where the young congregate in
nearshore areas. Sand, peat/mud, and mud
beaches are also important habitat for some
fish species, including alewife, American.
434De Sylva, D.P., F.A. Kalber Jr., and C.N. Shuster,
1962, Fishes and Ecological Conditions in the Shore
Zone of the Delaware River Estuary, with Notes on
Other Species Collected in Deeper Waters. Information
series. Publication No. 5, University of Delaware
Marine Laboratories, Lewes.
433Ibid.
-------
3.8. Maryland and Delaware
Coastal Bays Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats along in the back-barrier
bays of Maryland and Delaware (hereafter
referred to collectively as the Coastal Bays) are
potentially at risk because of sea level rise. The
Maryland Coastal Bays include Chincoteague,
Sinepuxent, Newport, Isle of Wight, and
Assawoman bays. The Delaware Inland Bays are
three interconnected bays (Little Assawoman
Bay, Indian River Bay, and Rehoboth Bay). The
shorelines of the Coastal Bays contain important
habitats for a variety of fish, shellfish, and birds,
and a great deal is known about their ecology
and habitat needs. Based on existing literature
and the knowledge of local scientists, this brief
literature review discusses the coastal species in
the region that could be at risk because of further
habitat loss resulting from sea level rise (see
Section 3.1, Overview) and shoreline protection
(see Map 3.7). Although it is possible to make
qualitative statements about the possible impacts
if sea level rise causes a total loss of habitat, our
ability to discern what the impact might be if
only a portion of the habitat is lost is more
limited. A total loss of habitat is possible if
shores are protected with hard structures and the
wetlands are unable to keep pace with sea level
rise.
Back-Barrier Salt Marshes
There are an estimated 6,718 ha (16,600 acres)
of salt marsh along Maryland's Coastal Bays,
mostly along the mainland shorelines of
Sinepuxent, Newport, and Chincoteague bays;
there are about 1,012 ha (2,500 acres) of salt
marsh in the northern bays.435 There are an
435Bleil, D., D. Clearwater, and B. Nichols, 2005, "Status of the
wetlands in the Maryland coastal bays," Chapter 6.4 in Wazniak,
C.E., and M.R. Hall (eds.), 2005, Maryland's Coastal Bays:
Ecosystem Health Assessment 2004, DNR-12-1202-0009,
estimated 5,510 ha (13,600 acres) of vegetated
estuarine wetlands in the Delaware Inland Bays,
most of which are tidal salt marshes.436 These
tidal salt marshes are mostly fringing marshes,
but there are also large acreages of back-barrier
marshes, especially in Rehoboth Bay.437
The Delaware's Inland Bays provide one of the
few areas in Delaware for colonial nesting
waterbirds, including herons, egrets, gulls and
terns. The rate of development within the bays'
drainage and associated shoreline hardening
would likely severely limit marsh migration
during sea level rise. Loss of the fringing
marshes and islands of the bays would
significantly reduce or eliminate nesting habitat
for these species in Delaware.438
The Maryland Coastal Bays Program considers
shoreline erosion due to sea level rise and
shoreline hardening major factors contributing to
a decline in the amount of natural shoreline
habitat available for estuarine species in the
Maryland Department of Natural Resources, Tidewater
Ecosystem Assessment, Annapolis, MD, p. 6-33.
436Tiner, R.W., 2001, Delaware's Wetlands: Status and Trends.
U.S. Fish and Wildlife Service, Ecological Services, Region 5,
Hadley, MA. Prepared for the Delaware Department of Natural
Resources and Environmental Control, Watershed Assessment
Section, Division of Water Resources, Dover, DE. Cooperative
National Wetlands Inventory Publication, Figure p. 9, text p. 16.
437Chris Bason, Center for the Delaware Inland Bays, email
communication to Karen Scott, EPA, 5/14/07 (personal visual
observation).
438Kevin Kalasz, wildlife biologist, Natural Heritage &
Endangered Species Program, Delaware Division of Fish and
Wildlife, in email entitled Opportunity to comment on U.S. EPA-
sponsored papers related to sea level rise and related impacts on
habitat and species, to Karen Scott of EPA, 2/16/07 (expert
judgment based on official duty).
-------
[ 252 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Cheaspeake
Accoma
Bar
N o rt h a
Places Examined by this Review
Location
Specific General
n/a Islands and Hummocks
Nontidal Ecosystem
Tidal Marsh
Ocean Beach
~Estuarine Beach
Mudflats
n/a SAV & Other Shallow Water Habitat
Talbot
Dorchester
—/.v/t" of Wight Bay
Skimmer_
Island
Ocean City
Jiini'piixent
Bv\'
Thompson's
Rehoboth
Sussex
Lewes
Cape Henlopen State Park
^-Rehoboth Beach
-Dewey Beach
Bay
Indian River Inlet
Burton
Island
Wicomico
Somerset
Mutton Hunk Fen
Area Preserve
Map 3.7, Locations and Types of Habitat Discussed in this Report: Atlantic Coast of the Delmarva
Peninsula
-------
[ SECTION 3.8 253 ]
northern bays.439 There has been significant
shoreline hardening in Maryland's northern
coastal bays (Isle of Wight and Assawoman),
but little or no hardening in the three
southernmost bays (Sinepuxent, Newport, and
Chincoteague).44" Planners expect shores in
the southern part of Maryland's coastal bays
to remain unprotected. Where natural
shorelines remain, marshes in low-lying areas
may expand inland as seas rise. Much of the
shoreline of Maryland's northern coastal bays
is protected using bulkheads or stone riprap,
resulting in unstable sediments and loss of
wetlands and shallow water habitat.441
Armoring of these shorelines will prevent
inland migration of marshes, and any
remaining fringing marshes will ultimately be
lost. The Maryland Coastal Bays Program
estimated that more than 607 ha (1,500 acres)
of salt marshes have already been lost in the
Coastal Bays as a result of shoreline
development and stabilization techniques.442
Loss of marshes will reduce habitat for many
bird species that use the marshes for roosting,
nesting, or foraging. Such species include
black-bellied plover, dunlin, and horned
grebe, wading birds such as herons and egrets,
migratory shorebirds, rail species, including
Virginia, king, and clapper rails, and many
species of waterfowl.443 Ducks and geese,
including mallards, pintails, blue and green
winged teals, gadwalls, canvasbacks, loons,
buffleheads, mergansers, and golden eyes,
overwinter in the bays' marshes.444 A large
colony of American brant winters in Rehoboth
and Indian River bays.445 The Rehoboth marsh
is known as an important area for colonies of
nesting shorebirds and a food source for
young birds.446 The bays' marshes also
provide nesting habitat for many species of
concern to federal and state agencies,
including northern harrier, American black
duck, Nelson's sparrow, salt marsh sharp-
tailed sparrow, seaside sparrow, coastal plain
swamp sparrow, black rail, Forster's tern,
gull-billed tern, black skimmers, and
American oystercatchers. There is particular
concern for Forster's tern because most of its
breeding range is in the salt marshes of the
mid-Atlantic.447
Marsh loss will also reduce habitat for resident
and transient fish and shellfish species. Marsh
resident fishes include mummichog, Atlantic
silverside, and naked goby. A number of
marine transients, including recreationally and
commercially important species such as black
drum, striped bass, bluefish, Atlantic croaker,
sea trout, and summer flounder, depend on the
marshes for spawning and nursery habitat.
Important forage fish that move into the bays
for spawning include spot, menhaden, silver
perch, and bay anchovy, which are currently
declining all along the Atlantic Coast.
Shellfish species found in the bays' marshes
include clams, oysters, shrimps, ribbed
mussels, and blue crabs.448
439Maryland Coastal Bays Program, 1999, Today's Treasures
for Tomorrow: Towards a Brighter Future; The
Comprehensive Conservation and Management Plan for
Maryland's Coastal Bays, Maryland's Coastal Bays Program,
Berlin, MD, Final Draft, June, p. 45.
440Hennessee, L., 2005, Status of the shorelines in the
Maryland coastal bays, Chapter 6.5 in Wazniak and Hall (see
note 435), p. 6-42.
441Maryland Coastal Bays Program, 1999, p. 6 (see note 439).
442Maryland Coastal Bays Program, 1999, p. 67 (see note
439).
443Dave Wilson, Maryland Coastal Bays Program. In June 13,
2006 email to E. Strange, Stratus Consulting, entitled "Follow
up to my visit," providing review of draft text and recounting
personal observations reported in a meeting on 16 May 2006.
(Dave Wilson is the outreach coordinator for the Maryland
Coastal Bays Program.)
444"Discover Delaware's Inland Bays," n.d., fact sheet,
Document No. 40-01-01/03/03/01 produced with funding
from NOAA by the Delaware Department of Natural
Resources and Environmental Control, Delaware Coastal
Programs. Available at:
www.dnrec.state.de.us/dnrec2000/Librarv/Mi sc/InlandBavs.p
df; and personal observations of Chris Bason (see note 437).
445"Discover Delaware's Inland Bays" (see note 444).
44oDelaware Inland Bays Comprehensive Conservation and
Management Plan, June 1995, Chapter 2: The State of the
Inland Bays, p. 86.
447Erwin et al., 2006, p.16 (see note 58).
448Casey, J., and S. Doctor, 2005, Status of finfish populations
in the Maryland Coastal Bays, Chapter 8.4 in Wazniak and
Hall (see note 435), p. 8-34.
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[254 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE]
Forested Wetlands
Forested wetlands occur along both tidal and
nontidal creeks. Increasing instances of crown
dieback and tree mortality in these wetlands are
generally considered a result of sea level rise and
an upstream shift in the salinity gradient. Where
inland migration is not possible, the understory is
being filled in with marsh plants, resulting in
loss of tree habitats that are critical for many bird
species, including bald eagles and a variety of
breeding songbirds.449
Sea Level Fen
A rare sea level fen vegetation community grows
in the Angola Neck Natural Area along
Rehoboth Bay.45" This extremely rare type of
coastal wetland grows only under the unusual
circumstances where there is a natural seep from
a nearby slope providing nutrient-poor
groundwater to support its unique vegetation and
where there is protection from nutrient-rich tidal
flow (see Section 3.1, Overview, for detailed
description of sea level fens)451 Because of its
location, the Angola Neck sea level fen could be
lost as rising seas move inland, bringing nutrient-
rich waters that are not tolerated by sea level fen
vegetation.
Coastal Plain Ponds
Coastal plain ponds are small, groundwater-fed
ponds that contain many rare plant species.
Because they are near sea level, these unique
plant communities are particularly vulnerable to
sea level rise. Such areas occur in the Delaware
Inland Bays, especially within Assawoman
Wildlife Management Area on Little Assawoman
Bay.452
449Gary Fleming (personal visual observation) (see note 76).
450Delaware Department of Natural Resources and Environmental
Control, Inland Bay Report. Accessed December 5, 2007 at:
http://www.dnrec. state. de.us/DNREC2000/Admin/WholeBasin/I
nlandBay s/li ving. pdf.
451Westerfelt, K, E. Largay, R. Coxe, W. McAvoy, S. Perles, G.
Podniesinski, L. Sneddon, and K. Starkosch Walz, 2006, A Guide
to the Natural Communities of the Delaware Estuary. Version 1,
NatureServe, Arlington, VA, p. 258.
452
" "Kevin Kalasz (see note 438) (personal visual observation) and
Chris Bason (see note 437) (personal visual observation).
Back-Barrier Beaches
The back-barrier beaches of the Coastal Bays
have a number of important ecological functions.
Horseshoe crabs spawn on these beaches,453
and their eggs are an important food source for
migrating shorebirds in spring 454Photuris
bethcmiensis is a globally rare firefly located
only in interdunal swales on Delaware barrier
beaches. The firefly's habitat is at risk because of
beach stabilization and shoreline hardening,
which limits dune migration and the formation of
interdunal swales. Local ecologists favor
research to ascertain whether protecting
infrastructure from sea level rise might also
increase erosion and further limit the formation
of new interdunal swales.455
Northern diamondback terrapin spend most of
their time in the marsh creeks and open waters of
the Coastal Bays, but move onto the back-barrier
beaches to nest and deposit their eggs along the
upper beach.456 Diamondbacks nest on back-
barrier beaches and most types of estuarine
beaches. In Delaware, they are known to next on
beaches of Burton Island.457 They also regularly
nest in residential areas, which may result from
their natal imprint leading them back to former
dune habitat that is now developed.458 A natural
instinct to get to the most suitable nesting habitat
in the dunes nearer the ocean may be the reason
some terrapins cross Route l.459 This has become
a major management concern because many are
killed by traffic.46"
Loss of additional beach habitat due to sea level
rise and erosion below bulkheads and other
protective structures could have a number of
negative consequences for species that use these
beaches for egg-laying, foraging, or other critical
453Dave Wilson, personal visual observation (see note 443).
454Delaware Audubon Society. Important Bird Areas in the
Delaware. Summary available at:
http://www.delawareaudubon.org/birding/globaliba.html.
455
"Kevin Kalasz (see note 438).
45oDave Wilson (personal visual observation (see note 443).
457
"Discover Delaware's Inland Bays" (see note 444).
45 8
Chris Bason (personal visual observation) (see note 437).
459Ibid.
4o0"Discover Delaware's Inland Bays" (see note 444).
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[ SECTION 3.8 255 ]
activities. Because terrapins bury their eggs deep
within sandy sediment, where the eggs are
protected against predators and other dangers, it
is unlikely that they could reproduce in
alternative habitats where it is more difficult to
dig into the sediment to bury their eggs.
Horseshoe crabs rarely spawn unless sand is at
least deep enough to nearly cover their bodies,
about 10 cm (4 in.).461 Shoreline protection
structures designed to slow beach loss can also
block horseshoe crab access to beaches and can
entrap or strand spawning crabs when wave
energy is high.462
Erosion and inundation may reduce or eliminate
beach wrack communities of the upper beach,
especially in developed areas where shores are
protected. Beach wrack contains insects and
amphipod crustaceans such as fleas and beach
hoppers that provide food for many species,
including migrating shorebirds.463 In addition,
horseshoe crab eggs are sometimes ensnared in
the wrack, where they are more accessible to
foraging shorebirds.464 Loss of wrack will
decrease these food sources (for a more detailed
description, see Section 3.1, Overview).
Tidal Flats
Tidal flats are found at the seaward edge of the
shorelines of both the Delaware and Maryland
Coastal Bays. The benthic invertebrates of tidal
flats typically include bivalves, small crabs,
worms, and snails, which are important forage
for shorebirds.465
The low-lying coastal plain and the fine
unconsolidated sediments of the bays makes
their tidal flats particularly susceptible to
inundation from sea level rise.466 In areas where
sediments accumulate in shallow waters and
shoreline protection prevents landward migration
of salt marshes, flats may become vegetated as
low marsh encroaches seaward, which will
further increase sediment deposition and lead to
an increase in low marsh and a reduction in tidal
flats.467 Where sediment deposition is
comparatively low, marsh may revert to
unvegetated flat, at least in the short term, before
the area becomes fully inundated.468
Reduction in the area of tidal flats will reduce
invertebrate food supplies for wading birds,
shorebirds, and dabbling ducks such as mallards
and the American black duck. As rising seas
cover flats with more and more water, they will
become less available to foraging species,
particularly short-legged shorebirds.469 Tidal flats
are critical for migrating shorebirds. Some
researchers predict that as inundation increases
and the area of tidal flats declines, increased
crowding in remaining areas will lead to
exclusion and mortality of shorebirds.47"
Shallow Waters and Submerged Aquatic
Vegetation (SAV)
There are currently about 4,629 ha (11,438 acres)
of SAV in Maryland's coastal bays, mostly
eelgrass. Nearly 85 percent of eelgrass beds are
found along the bayside of Assateague Island.
Eelgrass in Maryland's coastal bays is generally
limited to a maximum depth of about 1.5 m (5
feet)471 Thus, unless conditions change, a 50-
100 cm (20-40 in.) rise in sea level could
potentially make areas where water depths are
greater than 50-100 cm (20-40 in.) inhospitable
to SAV.472
4olWeber, R.G., 2001, Preconstruction horseshoe crab egg density
monitoring and habitat availability at Kelly Island, Port Mahon,
and Broadkill Beach Study areas, Prepared for the Philadelphia
District Corps of Engineers, Philadelphia, PA, p. 4.
4o2Doctor, S., and C.E. Wazniak, 2005, "Status of horseshoe crab,
Limulus polyphemns, populations in Maryland coastal bays,"
Chapter 8.7 in Wazniak and Hall (see note 435), p. 8-92.
4o3Dugan et al., 2003, p. 32 (see note 127).
4o4.Tackson et al., 2002, p. 418 (see note 139).
4o5Burger, J., L. Niles, and K.E. Clark, 1997, "Importance of
beach, mudflat, and marsh habitats to migrant shorebirds in
Delaware Bay "Biological Conservation 79:283-292, p. 284.
^"Johnson, Z.P., 2000, A Sea Level Rise Response Strategy' for
the State of Maryland, Maryland Department of Natural
Resources, Coastal Zone Management Division, p. 9 and Figure
2.
467Redfield, 1972 (see note 132).
4o8Brinson et al., 1995, p. 655 (see note 23).
4o9Erwin, no date (see note 136).
470Galbraith et al., 2002 (see note 50).
471Wazniak, C., L. Karrh, T. Parham, M. Naylor, M. Hall, T.
Carrathers, and R..T. Orth, 2005, Seagrass abundance and habitat
criteria in the Maryland Coastal Bays, Chapter 6.1 in Wazniak
and Hall (see note 435), p. 6-5.
472Short andNeckles, 1999, p. 175 (see note 91).
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[ 256 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Researchers are uncertain whether the natural
overwash process will keep water depths
constant by providing enough sediment for the
bay bottoms to rise as fast as the sea rises. Nor
does anyone know whether inundated marsh on
the mainland would be replaced by SAV. As a
result, we are unable to say whether SAV in this
area will increase or decrease as sea level rises.
The fate of SAV is very important for secondary
productivity in the back-barrier bays of
Maryland. Eelgrass beds are considered essential
habitat for summer flounder and bay scallop and
critical habitat for blue crab, which support
substantial recreational and commercial fisheries
in the coastal bays.473 Therefore, the possibility
of a net loss of eelgrass as sea level rises implies
a risk to the local populations of flounder,
scallop, and crab that are harvested in the coastal
bays of Maryland. SAV is also important for
many nongame species such as sticklebacks,
pipefishes, and seahorses.
At present, SAV is almost absent from the
Delaware Inland Bays because of eutrophication
and turbid conditions in the bays' shallow
waters.474 However, reestablishment of eelgrass
beds has been successful near Indian River Inlet,
where ocean-influenced water quality supports
growth.475 In the future, poor water quality
combined with increasing depth with sea level
rise could impede SAV recovery in other parts of
the bays.
Marsh and Bay Islands
Islands within the coastal bays are important
nesting areas for herons, egrets, black skimmers,
gulls and terns. Laughing gulls, herring gulls,
and great black-backed gulls nest on the marsh
islands of Delaware's Inland Bays. Forster's
473Maryland Coastal Bays Program, 1999, p. 56 (see note 439).
474Delaware Department of Natural Resources and Environmental
Control, 2001, Inland Bay s/Atlantic Ocean Basin Assessment
Report, June, p. 39.
475Delaware Department of Natural Resources and Environmental
Control, n.d., Inland Bays/Atlantic Ocean Environmental Profile.
Section on Water Quality: Water Resource Issues. Available at:
http://www.dnrec. state. de.us/water2000/Sections/Watershed/ws/i
b atlantic env profile.pdf.
terns nest on dead marsh grasses on the
islands.476
Marsh islands within the bays are undergoing
rapid erosion. Big Piney Island in Rehoboth Bay
experienced erosion rates of 30 ft/yr between
1968 and 1981, and is now gone.477 Little Piney
Island is another historical island in Rehoboth
Bay that is completely eroded. Currently, Seal
Island in Little Assawoman Bay is eroding
rapidly after being nearly totally devegetated by
greater snow geese.478 The erosion of the these
island and their potential submergence due to an
inability to keep pace with sea level rise are of
particular concern because these islands protect
other natural and developed shorelines and
marshes from increased erosion.
Hundreds of horned grebes stage for migration at
the north end of Rehoboth Bay near Thompson's
Island. Thompson's Island, part of the Delaware
Seashore State Park, is located between
Rehoboth and Dewey Beach, and is a significant
birding area. Located only a half mile from the
beach is the last stand of mature forest of white
oak and loblolly pine along the Delaware coast.
The island has several other habitat zones,
including salt marsh. Resident species include
some that are difficult to find along the coast,
such as hairy woodpecker and belted kingfisher.
The island is especially significant as a
"migration trap," where migrating birds are
funneled onto the island and "trapped" by 7
miles of inland bays and coast.479
Royal tern is a species that nests only on low-
lying islands.48" Although royal terns visit
Delaware's Inland Bays in the summer, they do
not nest there.481 In the Maryland bays, royal
47o"Discover Delaware's Inland Bays" (see note 444).
477
Swisher, M.L., 1982, The rates and causes of shore erosion
around a transgressive coastal lagoon, Rehoboth Bay, Delaware,
M.S. Thesis, College of Marine Studies, University of Delaware,
Newark.
478Chris Bason (personal visual observation) (see note 437).
479Ednie, A.P., n.dBirding Delaware's Prehistoric Past:
Thompson's Island at Delaware Seashore State Park. Available
at:
http://www.dvoc.org/DelValBirding/Places/TliompsonsIsland.ht
m.
480Buckley, P.A., and F.G. Buckley, 2002, Royal tern (Sterna
maxima), in Poole and Gill (see note 370).
481"Discover Delaware's Inland Bays" (see note 444).
-------
[ SECTION 3.8 257 ]
terns nest only on Skimmer Island, which is
currently only about 10 cm (4 in) above sea
level.
There are numerous small islands in Maryland's
Chincoteague Bay. However, stabilization of the
Ocean City inlets and efforts by the U.S. Army
Corps of Engineers to prevent formation of new
inlets have inhibited the natural formation of new
islands. The Corps has created many small
dredge spoil islands, but most have disappeared
as a result of erosion. These islands typically
provide good nesting habitat for gulls, egrets,
herons, American oystercatchers, glossy ibis,
American black duck, American bald eagle, and
482
osprey.
Many of the small islands in the coastal bays are
currently eroding, and may disappear altogether
as rising seas inundate low-lying areas. Further
loss of these islands because of erosion and sea
level rise could result in severe reductions in
island bird populations. 483
The highest number of nesting American
oystercatchers in Delaware are found nesting in
the Inland Bays. They primarily nest on small
sandy beaches and wrack on islands. Loss of
nesting habitat for this species would
dramatically reduce the population of American
oystercatcher in Delaware.484
482Erwin, 1996, p. 216 (see note 240).
484Kevin Kalasz (see note 438) (expert judgment based on official
duty).
-------
3.9 The Atlantic Side of the Virginia Eastern Shore
Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats in the tidal marshes of the
Atlantic Coast side of the Virginia Eastern shore
are potentially at risk because of sea level rise.
This region contains the largest stretch of natural
coastline along the U.S. Atlantic Coast, almost
all of which is owned by either TNC or the
federal government. The region includes
extensive back-barrier lagoonal marshes and
areas of estuarine beach behind a chain of barrier
islands. Fringing salt marshes occur on the
mainland side of the lagoons.
Based on existing literature and the knowledge
of local scientists, this brief literature review
discusses the coastal species in the region that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection (see Section 3.1, Overview) (see Map
3.7). Although it is possible to make qualitative
statements about the possible impacts if sea level
rise causes a total loss of habitat, our ability to
discern what the impact might be if only a
portion of the habitat is lost is more limited. A
total loss of habitat is possible if shores are
protected with hard structures and the wetlands
are unable to keep pace with sea level rise.
Back-Barrier Salt Marshes
Salt marsh adaptation to sea level rise. Salt
marshes occupy thousands of acres in eastern
Accomack and Northampton counties.485 Marsh
accretion experts believe that most of these
marshes are keeping pace with current rates of
sea level rise, but may be unable to continue to
do so if the rate of sea level rise increases by
another 2 mm/yr (see Section 2.1). Some local
field measurements indicate that accretion rates
may be insufficient to keep pace even with
current rates of sea level rise. Accretion rates as
485Fleming et al., 2006 (see note 67).
low as 0.9 mm/yr (Phillips Creek Marsh) and as
high as 2.1 mm/yr (Chimney Pole Marsh) have
been reported,486 and the average relative sea
level rise along the Eastern Shore is estimated as
2.8-4.2 mm/yr.487
The dominant accretion processes in eastern
Accomack and Northampton counties are storm
sedimentation and overwash from the beaches of
the barrier islands. A panel of accretion experts
recently suggested that if the rate of sea level rise
increases by 2 mm/yr, the survival of marshes in
this area will depend on the future frequency of
storms supplying sediments (see Section 2.1).
Other scientists have suggested that the ability of
the marshes of the Eastern Shore to keep pace
may be constrained by the generally low
sediment supply provided by the small
watersheds of the area.488'489 In 2004, annual
losses of 0.2 and 0.67 percent were reported for
Curlew Bay and Gull Marsh, respectively,
mostly as a result of perimeter erosion to open
water.49" However, in Mockhorn Wildlife Refuge
in southern Northampton County, where
elevations are lower, sediments have
accumulated in shallow waters, and low marsh is
encroaching on adjacent tidal flats.491'492
48oKastler, J.A., and P.L. Wiberg, 1996, "Sedimentation and
boundary changes of Virginia salt marshes," Estuarine, Coastal
and Shelf Science 42:683-700, p. 691.
487May, M.K., 2002, Pattern and Process of Headward Erosion in
Salt Marsh Tidal Creeks, Master's Thesis, Department of
Biology, Eastern Carolina University, Greenville, NC, p. 4,
reviewing the findings of G.F. Oertel, T.F. Wong, and J.D.
Conway, 1989, "Sediment accumulation at a fringe marsh during
transgression, Oyster, Virginia., Estuaries 12:18-26, and B.P.
Elayden, D. Dueser, J.T. Callahan, andH.H. Shugart, 1991,
"Long-term research at the Virginia Coast Reserve," BioScience
41:310-318.
488Christiansen, T., PL. Wiberg, and T.G. Milligan, 2000, "Flow
and sediment transport on a tidal salt marsh surface," Estuarine,
Coastal and Shelf Science 50:315-331, p. 324.
489Reed et al., 2008, Section 2.1.
490Erwin et al., 2004, p. 891 (see note 16).
491Erwin et al., 2006 (see note 58).
-------
[ SECTION 3.9 259 ]
Most wetlands are able to keep pace with rising
sea level today, become marginal with an
acceleration of 2 mm/year, and would be lost
with a more substantial acceleration (see Reed et
al., Section 2.1). Shore protection is unlikely
along much of the mainland opposite the barrier
islands and lagoonal marshes. In those
unprotected areas, marshes are likely to migrate
inland into low-lying areas. Kastler and Wiberg
found that from 1938 to 1990 mainland salt
marshes on the Eastern Shore increased in area
by 8.2 percent, largely as a result of
encroachment of salt marsh into upland areas.493
Sea level rise may also contribute to invasion by
the common reed (Phragmites), which provides
lower quality habitat. Higher sea levels cause
groundwater discharge to migrate upslope with
greater volume. Common reed can invade where
this discharge flows over the marsh surface,
providing lower salinity habitat.494
Impacts on fish and wildlife. Sea level rise is
considered a major threat to bird species in this
area, which is known as the Virginia Barrier
Island/Lagoon Important Bird Area (IBA).495
Biologists at the Patuxent Wildlife Research
Center suggest that submergence of lagoonal
marshes in Virginia would have a major negative
effect on marsh-nesting birds such as black rails,
seaside sparrows, saltmarsh sharp-tailed
sparrows, clapper rails, and Forster's terns.496
The USFWS considers black rail and both
sparrow species "birds of conservation concern"
because populations are already declining in
much of their range.497 A study of Virginia
marshes found that the number of bird species
was directly related to marsh size; the minimum
marsh size found to support significant marsh
bird communities was 4.1-6.7 ha (10-15
acres)498
A diversity of resident and estuarine and marine
transient fish species move in and out of marshes
with the tides to take advantage of the abundance
of decomposing plants in the marsh and refuge
from predators.499 Marine transients include
recreationally and commercially important
species, including black drum, striped bass,
bluefish, and Atlantic croaker. A study in
Virginia showed that nekton abundance and
diversity is greater in fringing marsh than along
intertidal shorelines that are armored.5""
Where sea level rise leads to increased flooding
of the marsh, some fishes may benefit, at least in
the short term, from an increase in tidal creeks
and channels, providing greater access to the
marsh. More water on the marsh surface may
also provide some benefits. For example, in the
salt marshes of the Eastern Shore, resident fishes
such as common mummichog and spotfin
killifish, and invertebrates such as grass shrimp,
forage in shallow waters on the marsh surface to
take advantage of an underutilized food source
and to avoid predators.5"1 However, where
marshes drown, the loss of marsh primary
production will impair the value of the habitat
for fish and shellfish. Virginia's highly valued
commercial and recreational fishing industry
may be harmed if fish and shellfish production
declines in these areas.
Sea Level Fen
A globally rare sea level fen community—one of
only four in Virginia—is found in the Mutton
Hunk Fen Natural Area Preserve fronting
492Erwin et al., 2004, p. 891 (see note 16).
493Kastler and Wiberg, 1996 (see note 486).
494Barry Trnitt (see note 360).
495Watts, B.D., 2006, Synthesizing Information Resources for the
Virginia Important Bird Area Program: Phase I, Delmarva
Peninsula and Tidewater, Center for Conservation Biology
Technical Report Series, CCBTR-06-05, College of William and
Mary, Williamsburg, VA, p. 6.
4%Erwin et al., 2004, p. 901 (see note 16).
497USFWS, 2002, Birds of Conservation Concern 2002, Division
of Migratory Bird Management, Arlington, VA, Table 30.
Available at:
http://www.fws.gov/migratorvbirds/reports/reports.html.
498Watts, 1993 (see note 61).
499See general discussions in Boesch and Turner, 1984 (see note
318); and Kneib, 1997 (see note 17).
500Carroll, R.A., 2002, Nekton utilization of intertidal fringing
salt marsh and revetment hardened shorelines, M.S. Thesis,
School of Marine Sciences, College of William and Mary,
Williamsburg, VA.
501Yozzo, D.J., A. Mannino, andD.E. Smith. 1994. "Mid-summer
abundance of resident sub-adult marsh nekton at the Virginia
Coast Reserve," Virginia Journal of Science 45:21-30, as cited
by Layman, C .A., 2000, "Fish assemblage structure of the
shallow ocean surf zone on the Eastern Shore of Virginia Barrier
Islands," Estuarine, Coastal, and Shelf Science 51:201.
-------
[ 260 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Gargathy Bay in eastern Accomack County.5"2
This extremely rare type of coastal wetland
grows only under the unusual circumstances
where there is a natural seep from a nearby slope
providing nutrient-poor groundwater to support
its unique vegetation, and where there is
protection from nutrient-rich tidal flow (see
Section 3.1 for more description of sea level
fens). The Division of Natural Heritage within
the Virginia Department of Conservation and
Recreation believes that chronic sea level rise
with intrusions of tidal flooding and salinity
poses "a serious threat to the long-term viability"
of sea level fens.5"3 If rising seas reach the
Mutton Hunk Fen Natural Area, the influx of
nutrient-rich waters may destroy the populations
of the rare plant species at this site, including the
carnivorous sundew, and bladderwort.5"4 On the
other hand, sea level rise could cause
groundwater discharge to increase in volume at
some locations, which would benefit fens.5"5
Back-Barrier Beaches
The beaches on the mainland behind the barrier
island complex of the Eastern Shore are small
strips of beach that are relatively stable because
they are protected from high energy wave action.
Where beaches erode in front of shoreline
protection structures and are not replenished, the
many invertebrates that burrow in the sand and
species that spawn on beaches will lose critical
habitat. Rare species that have sometimes been
observed on these beaches include the northern
diamondback terrapin and the northeastern tiger
beetle.506
Tidal Flats
CCSP submissions by the USGS will address the
likelihood that sea level rise will reduce the area
of tidal flats in areas with naturally low sediment
supplies like the Eastern Shore. Loss of tidal
flats would eliminate a rich invertebrate food
source for migrating birds such as whimbrels,
dowitchers, dunlins, black-bellied plovers, and
semipalmated sandpipers.5"7
Shallow Waters and Submerged Aquatic
Vegetation (SAV)
Natural eelgrass beds occur in a number of areas
along the sea side of the Eastern Shore, and are
most abundant in Chincoteague Bay. There are
also some successful eelgrass restoration projects
in South Bay, Cobb Bay, Hog Island Bay, and
Spider Crab Bay.5"8 The potential effects of sea
level rise on eelgrass beds have not been studied
directly. However, Short and Neckles estimate
that, in general, a 50 cm increase in water depth
as a result of sea level rise could reduce the
available light in coastal areas by 50 percent,
resulting in a 30-40 percent reduction in SAV
growth.509 Where this may occur in the
near shore waters of eastern Northampton and
Accomack counties would depend on current
local conditions such as water depth, the
maximum depth of eelgrass growth, and water
clarity. A local expert with The Nature
Conservancy suggests that because eelgrass is at
the southern limit of its range in the Coastal
502Fact sheet by Virginia Department of Conservation and
Preservation on the Mutton Hunk Fen Natural Area Preserve.
Accessed December 5, 2007 at:
http://www.dcr.virginia.gov/natural heritage/natural area preser
ves/muttonhunk. shtml.
503 Virginia Department of Conservation and Recreation, 2001,
The Natural Communities of Virginia, Ecological Classification
of Ecological Community Groups, First Approximation, Division
of Natural Eleritage Natural Eleritage Technical Report 01-1, p.
48.
504Mutton Elunk Fen Natural Area Preserve Fact Sheet (see note
502).
505The authors would like to thank reviewer Barry Truitt for
pointing this out (see note 360).
50oSee information on these species and their status in Virginia,
provided in Chapter 3: Refuge and Resource Descriptions
(specifically pages 3-20 and 3-32) of USFWS, 2004, Eastern
Shore of Virginia and Fisherman Island Nation Wildlife Refuges
Comprehensive Conservation Plan, Northeast Regional Office,
Eladley, MA, available at:
http://librarv.fws.gov/CCPs/eastshoreVA index.htm.
507The Nature Conservancy project profile for the Virginia Coast
Reserve, 2006, available by searching on "field guides" at
http://www.nature.org/wherewework. See also Watts, B.D., and
B.R. Truitt, 2000, "Abundance of shorebirds along the Virginia
barrier islands during spring migration," Raven 71:33-39.
508Information provided in July 12, 2006, email to E. Strange of
Stratus Consulting from Scott Lerberg of the Virginia Seaside
Eleritage Program. Orth, R. J., M. L. Luckenbach, S. R. Marion,
K. A. Moore, and D. J. Wilcox, in press, "Recovery of the
seagrass Zostera marina (eelgrass) in the Delmarva Coastal Bays,
USA," Aquatic Botany.
509Short and Neckles, 1999 (see note 91).
-------
[ SECTION 3.9 261 ]
Bays, global warming may be a greater factor in
its persistence than light reduction.51"
Loss of eelgrass beds could harm local
populations of birds, fish, and shellfish. Various
waterbirds feed on eelgrass beds, including
brant, canvas back, and American black duck.511
Virginia's commercial and recreational fisheries
include many estuarine and marine species that
rely on eelgrass for nursery habitat.512 A number
of highly valued shellfish species are also found
here, including bay scallop, hard clam, and blue
crab.
Marsh and Bay Islands
Several bird species of concern in Virginia and
elsewhere along the Atlantic Coast, including
gull-billed terns, common terns, black skimmers,
and American oystercatchers, nest on shellpiles
on marsh islands.513 The advantage of this is that
the shellpiles are generally free of mammalian
predators. However, marsh islands are also
subject to tidal flooding, which is known to
reduce the reproductive success of island-nesting
birds.514 Therefore, as islands experience more
erosion and flooding as a result of sea level rise,
local populations of island-nesting birds may
decline.
Island shrinking is already apparent along the
Eastern Shore. From 1949 to 1990, Chimney
Pole marsh showed a 10 percent loss to open
water.515 Chimney Pole marsh is directly inside
Quinby Inlet and subjected to high energy wave
action during storms. As early as the mid-1990s,
gull-billed tern nests on Chimney Pole Island
were only a foot above the June high water mark,
indicating its vulnerability to even relatively low
increases in rates of sea level rise.516
Coastal Habitat for Migrating Neotropical
Songbirds
Because of their importance for migrating
neotropical songbirds such as indigo buntings
and ruby-throated hummingbirds, the coastal
areas of southern Northampton County are a
designated Important Bird Area (IB A).517 Not
only are these birds valued for their beauty but
they also serve important functions of dispersing
seeds and controlling insect pests. It is estimated
that a pair of warblers can consume thousands of
insects as they raise a brood.518
Chesapeake Bay is a significant physical barrier
that acts as a bottleneck for migrating birds,
funneling southbound migrants to lower
Northampton County, where they concentrate
within the tree canopy and thick understory
vegetation found within the lower 9.66 km (6
miles) of the peninsula within 188.82 m (200
yards) of the shoreline. Loss of this understory
vegetation as a result of rising seas would
eliminate this critical stopover area for
neotropical migrants, many of which have shown
consistent population declines since the early
1970s.519
510Barry Triiitt (see note 360).
511 Perry and Deller, 1996 (see note 100).
512Wyda et al., 2002 (see note 95).
513Rounds et al., 2004 (see note 78).
514Eyler et al., 1999 (see note 78).
515Kastler and Wiberg, 1996 (see note 486).
516Erwin, R.M., J.G. Haig, D.B. Stotts, B. Traitt, and C.R.
Carlson, 1995, Will the tide tern? Rising sea levels, invasive
species, agricultural pesticides, and nesting gull-billed terns.
Available at:
http://www.vcrlter.virginia.edu/davedocs/VCRASC95/erwin.html
517Watts, 2006, p. 5 (see note 495).
518Mabey, S., B. Watts, and L. McKay, n.d., Migratory Birds of
the Lower Delmarva: A Habitat Management Guide for
Landowners, The Center for Conservation Biology, College of
William and Mary, Willamsburg, VA, p. 7.
519Mabey et al., p. 10 (see note 518).
-------
3.10 Chesapeake Bay: Local Area Coastal Habitat
and Environmental Implications of Sea Level
Rise: Anticipated Effects by Multicounty
Region Author: Ann Shellenbarger Jones, Industrial Economics Inc.
The environmental implications of sea level rise
vary in extent and certainty for different habitat
types. Section 3.1 provides general background
on species and their habitats vulnerable to sea
level rise for the mid-Atlantic. This collection of
short literature reviews describes where impacts
to these vulnerable species may occur in
Chesapeake Bay by taking a walk along its
shoreline, beginning with Norfolk, Virginia, and
continuing up the western side of the bay
(traversing the Potomac and Patuxent rivers and
up to the Susquehanna River), then returning
along the eastern shore of the bay, to the
southern tip of Northampton County.
We rely on various published sources of data and
information on wetlands, shoreline type and
condition, erosion, future shore protection, and
habitat types and locations to characterize
current and potential future shoreline ecology of
Chesapeake Bay.52"
52"Sources for wetlands information: Tiner and Burke,
1995 (see note 32); and National Wetlands Inventory.
Sources for shoreline type and condition: Comprehensive
Coastal Inventory Program, 2005, Shoreline Situation
Reports, Virginia Institute of Marine Science (VIMS),
College of William and Mary, Gloucester Point, VA,
available at http://ccnn.vims.edu/gis/gisdata.html. These
reports, which will eventually be available for all counties
on Chesapeake Bay, include surveys of bank condition
(height, erosion extent, vegetative cover, land use),
presence and condition of fronting marsh or beach, and the
extent and types of shoreline protections.
Source for accretion estimates, unless otherwise noted:
Reed et al.. Section 2.1.
Source for erosion information in Maryland: Maryland
Shoreline Changes Online, from the Maryland Department
of Natural Resources. Available at:
http://shorelines.dnr.state.md.us/sc_online.asp.
These brief literature reviews discuss species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection. Existing literature and knowledge of
coastal scientists in the area are sufficient in
many cases to make qualitative statements about
the possible impact if sea level rise causes a total
loss of habitat, which might be expected if
shores are protected with hard structures or the
wetlands are unable to keep pace with sea level
rise. Our ability is more limited, however, to say
what the impact might be if only a portion of the
habitat is lost. The reviews take account of
shoreline features, anticipated shore protection,
and the potential for wetlands to keep pace with
rising sea level. Where possible, they assess the
combined implications of those factors, to
indicate predicted retention or loss of current
primary habitats. Where available, we delineate
effects associated with a particular location (e.g.
unique shoreline type, endangered and
threatened species) (see Section 3.1 for
descriptions of generalized potential responses).
Map 3.8 illustrates the regions of Chesapeake
Bay and the key locations for which we have
data on the species that depend on habitat
vulnerable to sea level rise. We discuss the
following multicounty sections separately.
Source for shoreline and habitat types: A set of four maps
are available from NOAA's Office of Response and
Restoration for all of Chesapeake Bay, showing seasonal
changes in the Chesapeake (ESI 1993). Detailed digital
maps (GIS format) are available from NOAA's Office of
Response and Restoration for the Virginia portion of
Chesapeake Bay (ESI 2005). These maps provide detail on
shoreline type, nearshore and inshore habitats, and
locations of endangered species.
-------
[ SECTION 3.10 263 ]
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Places Examined by this Review
Location
Specific General
1 •--- Nontidal Ecosystem
»¦¦¦ Tidal Marsh
Ocean Beach
—-»¦» Estuarine Beach
n/a SAV & Other Shallow Water Habitat
Map 3.8. Environmental Importance of Habitat Vulnerable to Sea Level Rise: Locations Examined in
this Report. See legend on next page for location name index and associated habitat.
-------
[ 264 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Legend for Map 3.8
Location Name Index
Habitat (as mentioned in
text for this location).
Location Name Index
Habitat (as mentioned in
text for this location).
1. Cape Henry
Ocean Beach
30. Accotink Bay
Tidal Marsh
2. Lynnhaven Inlet/River
Estuarine Beach
31. Dyke Marsh
Tidal Marsh
3. City Beach Park
Estuarine Beach
32. Roosevelt Island
Tidal Marsh
4. Willoughby Bay
Estuarine beach -
groinfields
33. Anacostia River
Limited tidal marsh,
armoring
5. Grandview Beach Nature
Estuarine Beach
34. Mattawoman Creek
Estuarine Beach
Preserve
6. Plum Tree Island Marsh
Tidal Marsh
35. Port Tobacco
Tidal Marsh
7. Ware Stick Island
Tidal Marsh
36. Zekiah and Gilbert
Swamps
Nontidal marsh
8. Goodwin Islands
Tidal Marsh
37. Cobb Island
Estuarine Beach
9. Pamunkey and Mattaponi
Tidal Marsh
38. Point Lookout State
Tidal Marsh
Rivers
Park
10. Gloucester Marshes,
Tidal Marsh
39. Cove Point
Tidal marsh to north of
Guinea Neck
point, beach to south of
point
11. New Point Comfort
Tidal Marsh
40. Calvert County Cliffs
Cliffs
12. Winter Harbor
Tidal Marsh
41. Jug Bay and Patuxent
River Park
Tidal Marsh
13. Bethel Beach Natural
Tidal Marsh fronted by
42. Shady Side
Tidal Marsh
Area Preserve
Estuarine Beach
14. Gwynn's Island
Estuarine Beach
43. North Point State Park
Tidal Marsh
15. Fishing Bay
Estuarine Beach
44. Aberdeen Proving
Ground
Tidal Marsh
16. Stove Point
Estuarine Beach
45. Elk Neck State Park
Cliffs
17. Mosquito Point
Estuarine Beach
46. Sassafras Natural
Resources Management
Area
Cliffs
18. North Point
(geographic)
47. Eastern Neck National
Wildlife Refuge
Tidal Marsh
19. Hughlett Point Natural
Tidal Marsh
48. Kent Island
Revetments and some
Area Preserve
estuarine beach
20. Westmoreland State
Park
Cliffs
49. Crab Alley Bay
Submerged aquatic
vegetation
21. Colonial Beach
Estuarine Beach
50. Wye Island Natural
Resources Management
Area
Tidal Marsh
22. Intentionally left blank
51. Tilghman Island -
western/bay side
51. Tilghman Island -
eastern side
Mix of fringing tidal marsh
and estuarine beach
Tidal marsh shoreline,
shallow water/tidal flats
23. Chotank Preserve
Tidal Marsh
52. Poplar Island
Tidal Marsh
24. Caledon Natural Area
Cliffs
53. Walnut Point
Armored estuarine beach
25. Crow's Nest Peninsula
Tidal Marsh
54. Saxis Wildlife
Management Area
Tidal Marsh
26. Nanjemoy Peninsula
Tidal Marsh
55. Parkers Marsh Natural
Area Preserve
Tidal Marsh
27. Featherstone NWR
Tidal Marsh
56. Savage Neck Dunes
Natural Area Preserve
Estuarine Beach
28. Occoquan National
Tidal Marsh
57. Cape Charles Coastal
Estuarine Beach
Wildlife Refuge
Habitat Natural Area
Preserve
29. Mason Neck, Mason
Tidal Marsh
58. William B. Trower
Estuarine Beach
Neck State Park, Mason
Bayshore Natural Area
Neck National Wildlife
Preserve
Refuge
-------
3.11 The Chesapeake Bay Shoreline near Hampton
Roads
Authors: Ann Shellenbarger Jones, Industrial Economics Inc.,
Christina Bosch, Industrial Economics Inc.
Overview
The shores of Chesapeake Bay to the south of
Hampton Roads521 are dominated by the north-
facing sandy beaches of Virginia Beach and
Norfolk. To the north, the shores of Hampton,
Poquoson, and York counties are mostly tidal
marsh. The marshes and the species that depend
on them are potentially vulnerable to sea level
rise. The bay beaches, by contrast, appear likely
to survive.
Virginia Beach will be greatly affected by
continued local anthropogenic actions, which
may or may not follow historical patterns that
resulted in the current beach configurations. City
planners anticipate that the shoreline of the City
of Virginia Beach is almost certain to be
protected through armoring or beach
nourishment. Sandy beaches may be retained in
various protected areas owing to nourishment
projects, but will otherwise be eroded in front of
protective structures. A 2002 beach management
plan includes recommendations for long-term
replenishment programs at Chesapeake, Ocean
Park, and Cape Henry beaches.522 If beaches are
521 Hampton Roads is the large harbor between the
confluence of the James and Elizabeth rivers and
Chesapeake Bay. We did not look at the tidal habitat of
Hampton Roads or its tributaries. In general, as indicated
in ESI 2005, the northern shores of the harbor are hardened
with riprap and other artificial structures, while the riparian
shores of the Nansemond river are tidal marsh. See Map
3.8 for indication of level of detail provided by location.
522Virginia Beach, Beaches and Waterways Advisory
Commission, 2002, Virginia Beach Beach Management
Plan, accessed on July 25, 2007, at:
lost in other localities to sea level rise, the few
plants that are well adapted to the harsh beach
environment in these local areas will be lost.
Habitat for invertebrates (e.g., sand diggers, sand
fleas, horseshoe crabs, and mole and ghost crabs)
will be lost. Shorebirds that rely on beaches for
forage and nesting (e.g., turnstones, sanderlings,
and plovers) will face more limited resources.523
Current rates of sea level rise in the Poquoson
marshes and some Hampton areas are converting
marsh to open water; these marsh areas will be
inundated as sea level rise accelerates,
converting marsh areas to tidal flats and then
open water (Section 2.1). Inundation will
eliminate habitat for many marsh inhabitants
such as crustaceans, mollusks, and other
invertebrates. Turtles (e.g., diamondback
terrapins) and birds (e.g., ducks, rails) that forage
on the invertebrates will therefore also lose food
sources. Habitat for fish (described
subsequently) that spend portions of their lives in
wetlands will be lost, as will habitat for birds that
nest exclusively in marshes (known as marsh-
obligates). In this region, the dozens of bird
species that use Plum Tree Island marsh will be
impacted by continued marsh loss. The
ecosystem functions of flood control, erosion
buffering, and nutrient and contaminant filtering
will be lost as wetlands are submerged.524
http://www.vbgov.com/file_source/dept/planning/beach_m
anagement_plan.pdf.
523Lippson and Lippson 2006, pp. 26-42 (see note 2).
524Lippson and Lippson 2006, pp.201-239 (see note 2).
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[ 266 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Let us now examine the habitat vulnerable to sea
level rise and the species that depend on it, from
south to north.
City of Virginia Beach
Sandy beaches with dune systems compose the
Chesapeake Bay shoreline of the City of Virginia
Beach. The sands reach from Cape Henry
(CBIM location 1 on Map 3.8) on the
northeastern edge of the county to the inlet at the
mouth of the Lynnhaven River, past the
Chesapeake Bay Bridge and Tunnel and Little
Creek to the mouth of the James River.525 Net
longshore transport on Virginia Beach's Bay side
is to the west. Overall trends in the last century
show the dunes east of the Lynnhaven inlet
advancing into Chesapeake Bay (CBIM location
2). West from the inlet, erosion, beach
nourishment, and fill operations as well as
condominium development and shoreline
armoring have affected the accretion and erosion
patterns. Dredging activity for navigation in the
Lynnhaven inlet may also be affecting accretion
and erosion, temporarily adding sediment to the
longshore transport system; some Chesapeake
shoreline beaches, such as those at Ocean Park,
have required nourishment multiple times to
maintain their area. The Virginia Beach resort
area on the ocean shore has received beach fill
material since the mid-1950s.526 Given the
extensive patterns of nourishment and shoreline
protection in place today, minimal additional
ecological change from accelerated rates of sea
level rise is anticipated.
Studies of beach nourishment indicate that the
practice may have minimal biological effects if
projects are properly designed, but that projects
also have unknown effects related to changing
beach slopes, sediment characteristics (e.g., grain
size of new material may be different than that of
the native material), and potential loss of bay-
bottom habitat when beaches are extended
525Hardaway et al., 2005, Shoreline Evolution, Chesapeake
Bay Shoreline, City of Virginia Beach, Virginia. Virginia
Institute of Marine Sciences, College of William and
Mary, Gloucester Point, VA.
526Hardaway et al., 2005, p. 9 (see note 525).
waterward.527 Studies that evaluate long-term
effects on biota are not common.528
City of Norfolk
The sandy beaches found in the City of Virginia
Beach continue westward along the Chesapeake
shoreline in the City of Norfolk (CBIM locations
3-4). The rate of erosion is generally low, and
beach accretion occurs along much of the shore.
However, just west of City Beach Park, erosion
potential is higher. Banks up to 10 feet high line
the City Beach Park coast, with breakwaters at
portions of their bases (CBIM location 3).
Groinfields and breakwaters protect the shore
going west across Willoughby Bay (CBIM
location 4).529 The areas protected by groinfields
and breakwaters have been deemed "relatively
stable" by Hardaway et al.53" As evidenced by
the heavily armored status of the shores today,
planners anticipate that shoreline protection is
almost certain along the entire bay side of
Norfolk. Unnourished sandy beaches lacking
protection may be eroded, narrowed, and
eventually lost,531 eliminating the habitat they
provide today for invertebrates and shore birds.
City of Poquoson and City of Hampton
The City of Poquoson is located at the eastern tip
of Virginia's Hampton Roads peninsula (CBIM
locations 5-7). Planners indicate that the
developed portion of the city is almost certain to
be protected, whereas Plum Tree Island Marsh
(also known as Big Salt Marsh, CBIM location
6) and adjacent areas east of the city are already
experiencing loss to erosion and rising sea levels
(Section 2.1). Plum Tree Island Marsh, the
largest saline marsh in the Lower Chesapeake,
covers 4,100 acres, or 44 percent of Poquoson's
9,395-acre total area, and contains salt marsh and
527Jackson et al., 2002, p. 420 (see note 139).
528Nordstrom, 2005, p. 216 (see note 153).
529Berman, M.R., Berquist, H., Killeen, S., Hershner, C.H.,
Rudnicky, T„ Schatt, D.E., Weiss, D., and H. Woods,
2002, City of Norfolk Shoreline Situation Report, Special
Report in Applied Marine Science and Ocean Engineering
No. 378, Comprehensive Coastal Inventory Program,
Virginia Institute of Marine Science, College of William
and Mary, Gloucester Point, VA.
53"Hardaway et al., 2005, p. 9 (see note 525).
531Nordstrom, 2005, p. 215 (see note 153).
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[ SECTION 3.11 267 ]
remnant forested dune hummocks.532 The Plum
Tree Island National Wildlife Refuge has very
limited human access because of the quantities of
unexploded ordnance on the island from its prior
use as a bombing range. The relative isolation of
the area has made it a haven for more than 100
different species of birds, including northern
harrier (Circus cyaneus), black duck (Anas
rubripes), sedge wren (Cistothorus platensis),
sharp-tailed sparrow (Ammodramus caiidaciitus),
bald eagle, peregrine falcon (Falco peregrinus),
black-necked stilts (Himcmtopus mexiccimts), and
little blue heron (Egrettci caeruled). A variety of
mammals (muskrats, red fox, white-tailed deer)
use the higher ground of the refuge. Endangered
sea turtles, primarily the loggerhead, use the
nearshore waters. Oyster, clams, and blue crabs
use the shallow waters and mudflats, and striped
bass, mullet, spot, and white perch, among other
fish, have been found in the nearshore waters and
marsh.533 Across from the marsh in Hampton is
the Grandview Beach Nature Preserve (CBIM
Location 5), which has more than 2 miles of
beach shoreline on Chesapeake Bay and is home
to a population of northeastern beach tiger
beetles (Cicindela dorsalis dorsalis), federally
listed as threatened.534
Tidal wetlands with varying degrees of erosion
are present throughout the area, and some
beaches with low erosion rates line the many
small north-facing islands and higher areas such
as Ware Stick Island (CBIM location 7) and Cow
Island.535 The highest elevation within the long-
established portions of Poquoson is only 10 feet
above sea level.536 Reed et al. in Section 2.1
indicate wetlands loss in Poquoson even with the
532City of Poquoson Comprehensive Plan, 1999,
Environmental Element, accessed on July 17, 2006, at:
http://www.ci.poquoson.va.us/.
533Profile of the Plum Tree Island National Wildlife
Refuge, accessed on July, 20 2006, at
http://www.fws.gov/refuges/ profiles/index.cfm?id=51512.
534USFWS, 1994, p. 6 (see note 158).
535Berman, M.R., Berquist, H„ Dewing, S., Glover, J.,
Hershner, C.H., Rudnicky, T., Schatt, D.E., and Skunda,
K., 2001. City of Poquson Shoreline Situation Report,
Special Report in Applied Marine Science and Ocean
Engineering No. 369, Comprehensive Coastal Inventory
Program, Virginia Institute of Marine Science, College of
William and Mary, Gloucester Point, VA.
536City of Poquoson Comprehensive Plan, 1999 (see note
532).'
current rate of sea level rise. The City of
Poquoson's Multi-Hazard Mitigation Plan
identifies sea level as a threat to the area, noting
in particular that over time there is potential for
increased storm surges, erosion, and loss of
coastal zone land area, including wetlands.537
Loss of coastal zone areas may lead to loss of the
crustaceans, mollusks, and other invertebrates
that live in close association with the wetland
vegetation. Habitat for fish that use the mudflats
and marshes will be lost, as will nesting habitat
for marsh-obligate birds and the protection
provided by the refuge for the numerous resident
and migrating birds (described previously).
York County
Fringing tidal marshes line much of the York
County bay shoreline, and the Goodwin Islands
(CBIM location 8) at the extreme northeast of
the county are made up of extensive marsh
areas.538 The Goodwin Islands are protected as a
National Estuarine Research Reserve (NERR).
Covering 315 ha (777 acres), they are
surrounded by intertidal flats, extensive SAV
beds (121 ha; 300 acres of eel grass and widgeon
grass), and shallow open estuarine waters.539 The
salt marshes are dominated by salt marsh
cordgrass (Spartina alterniflora) and salt
meadow hay (Spartinapatens). Forested wetland
ridges are dominated by estuarine scrub/shrub
vegetation, with a primarily loblolly pine (Pinus
taeda) overstory, and wax myrtle (Morella
cerifera) shrub layer. Mixed oak and pine
communities, including red oak (Ouercus rubra),
loblolly pine, black gum (Nyssa sylvatica), and
cottonwood (Popuhis deltoides), are found on
upland ridges located on the largest island.54" As
537AMEC Earth and Enviromnental Inc., 2004, City of
Poquoson, Virginia, Multi-Hazard Mitigation Plan.
538NOAA, 2005, Environmental Sensitivity Index digital
data for Virginia, obtained from the NOAA Office of
Response and Restoration.
539Chesapeake Bay National Estuarine Research Reserve in
Virginia, Goodwin Islands, accessed on November 20,
2006, at
http://www.vims.edu/cbnerr/reservesites/goodwin.htm.
54"Chesapeake Bay National Estuarine Research Reserve in
Virginia; Virginia Department of Game and Inland
Fisheries. Goodwin Islands National Estuarine Research
Reserve. Accessed on November 20, 2006, at
http://www.dgif.state.va.us/wildlife/vbwt/site.asp?trail=l&
site=CLP06&loop=CLP.
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[ 268 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
of 2002, bald eagles nested on the Goodwin
Islands.541 Presumably, these marsh islands will
experience similar effects as those described for
other marsh islands, and the surrounding tidal
flats and SAV will possibly migrate inland, or
eventually be lost (see Section 3.1 for a general
description of marsh island, tidal flat, and SAV
responses to sea level rise). Reed et al. in Section
2.1 indicate that most lower bay marshes and the
fringing marshes along the York River are
currently keeping pace with sea level rise
through peat accumulation, but would be
marginal with a 2 mm per year increase and lost
with a 7 mm per year increase.
Wrapup
Continued nourishment and breakwater
protection are anticipated for the majority of
Hampton Roads beaches, limiting the likelihood
of additional ecological change.542 At the current
rate of sea level rise, Plum Tree Island marsh is
losing area. With any increase in rates of sea
level rise, continued loss of area is expected
because of the unprotected status of the majority
of the shoreline.543 The numerous bird species
that frequent it will therefore face
reduced resources. Vegetation and associated
fauna may migrate inland as land is lost, but the
developed portions of the city may eventually
limit their migration and survival.544 Though the
York County marshes (including Goodwin
Islands) are keeping pace with the current rate of
sea level rise, it is not known that they will
continue to do so with increased rates of sea
level rise; they may become marginal under a
midrange increase (2 mm per year), and are
likely to be lost under a high-range scenario
(increase of 7 mm per year).545
541Watts, B.D., and C. Markham, 2003, The influence of
salinity on diet, prey delivery, and nestling growth in bald
eagles in the lower Chesapeake Bay: Progress Report,
Center for Conservation Biology Technical Report Series,
CCBTR-03-06, College of William and Mary,
Williamsburg, VA, p. 1.
542Author's analysis from Hardaway et al. 2005 (see note
525), Nordstrom 2005 (see note 153), and Jackson et al.
2002 (see note 139).
543Author's analysis based on Section 2.1, and AMEC
Earth and Enviromnental Inc. 2004 (see note 537).
544Nordstrom (2005) notes that "fixed human development
on eroding shores prevents natural landward migration of
coastal landfonns" p. 215 (see note 153).
545Author's analysis based on Section 2.1.
-------
3.12 The Chesapeake Bay Shoreline of Middle
Peninsula
Authors: Ann Shellenbarger Jones, Industrial Economics Inc.,
Christina Bosch, Industrial Economics Inc.
Overview
The Middle Peninsula region comprises
Chesapeake Bay shorelines of Gloucester,
Mathews, and Middlesex counties. Additionally,
the area includes the Rappahannock and
Piankatank River shorelines of these counties
and several islands in the rivers.
This brief literature review discusses species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection (see Section 3.1 for general
background). Existing literature and knowledge
of coastal scientists in the area appears to be
sufficient in many cases to make qualitative
statements about the possible impact if sea level
rise causes a total loss of habitat, which might be
expected if shores are protected with hard
structures and the wetlands are unable to keep
pace with sea level rise. Our ability is more
limited, however, to say what the impact might
be if only a portion of the habitat is lost. The
overall environmental impact of sea level rise in
this multicounty region is likely to include the
following:
• The tidal estuarine marshes of Gloucester
County are already being submerged, and the
Mobjack Bay-facing marshes of Mathews
County will be marginal with an increase of
2 mm per year in the rate of sea level rise.546
546Author's read of map in Reed et al., Section 2.1 showing
wetlands in this area being converted to open water at the
current rate of sea level rise; and Moore, K., 1976,
Gloucester County Tidal Marsh Inventory. Special Report
No. 64 in Applied Science and Ocean Engineering,
Virginia Institute of Marine Science, Gloucester Point,
VA. pages 42-44.
Marsh vegetation habitat for a range of
species, including crustaceans, mollusks, and
other invertebrates, will be lost. Birds and
fish that forage on these invertebrates will
therefore face a changed or limited food
supply. Nesting habitat for birds will also be
eliminated.547 If marsh vegetation is lost, the
ecosystem functions of flood control, erosion
buffering, and nutrient and contaminant
filtering will be lost as wetlands are
submerged.
• Unnourished beaches in the Middle
Peninsula, such as the natural area preserve
of Bethel Beach, are already experiencing
erosion, and may be lost to accelerated sea
level rise. The few plants that are well
adapted to the harsh beach environment, and
the rare sea-beach knotweed, will be lost.
The population of least terns that nests at
Bethel Beach may also lose habitat.548
• Marsh islands in the Rappahannock and
Piankatank rivers are likely to be lost,
eliminating valuable nesting habitat for
marsh-obligate birds.
Gloucester County
East of Route 17, Guinea Neck, is vulnerable and
already being submerged owing to both erosion
and sea level rise (CBIM location 10).549 The
547 Author's analysis based on biological information
provided in Lippson and Lippson 2006, pp. 201-239 (see
note 2); and Moore, 1976 (see note 546). For more detail
on the impacts of sea level rise to wetland habitat and
species, see Section 3.1.
548Lippson and Lippson 2006, pp. 26-42 (see note 2).
549Author's read of map in Reed et al.. Section 2.1 showing
wetlands in this area being converted to open water at the
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[ 270 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
low-lying area bordering southern Mobjack Bay
and Chesapeake Bay is composed of tidal
wetlands. It is not likely to be protected and will
continue to be lost, decreasing available habitat
for the many birds, fish, and other creatures that
use the marshes and tidal creeks. Some portions
may be able to accrete sufficient sediment or
migrate inland, but planners anticipate the
construction of shoreline protections, which may
preclude migration in protected areas. The 5 to 10
foot higher elevation roughly paralleled by Rte.
17 is likely to limit any inland migration that is
not outpaced by sea level rise. As early as 1976,
though not explicitly linked with sea level rise, it
was observed that formerly reclaimed
agricultural land was being converted back to
marsh and high marsh vegetation species were
migrating inland into forested areas.55" In the
upper reaches of the York River's tributaries,
such as the Pamunkey and Mattaponi rivers, tidal
hardwood marshes show effects of sea level rise
(CBIM location 9). Brackish to freshwater marsh
plants are encroaching on these forested areas.
Tree death is occurring and further inland
migration is hindered by the higher upland
elevation behind the forested marshes.551 Tidal
hardwood marshes provide nesting sites for
piscivorous species such as ospreys, bald eagles,
and double-crested cormorants.552 The freshwater
marshes also host a variety of migratory and
breeding birds.
A study examining the relationship of birds to
vegetation communities in the Lee and Hill
marshes in the lower Pamunkey River indicates
that bird communities may change if high marsh
vegetation is replaced with lower marsh
vegetation. The authors posit that brackish
marshes, because of their locations at transitions
between tidal freshwater and oligohaline
current rate of sea level rise; and Moore, 1976, pp. 42-44
(see note 546).
55llMoore, 1976, pp. 42-44 (see note 546).
551 Gary Fleming, September 11, 2006 email (see note 76)
confirming phone call notes, including information
regarding his work in the Mattaponi and Pamunkey river
freshwater marshes.
552Robbins, C.S. andE.A.T. Blom, 1996, Atlas of the
Breeding Birds of Maryland and the District of Columbia,
University of Pittsburgh Press, Pittsburgh, PA, pp. 44, 92-
94.
marshes, may face greater risk than marshes with
more extreme, nontransitional salinities.
Outlining a scenario in which sea level rise
causes a shift of 100 ha from high marsh big
cordgrass (Spartinci cynasnroides) to low marsh
arrow arum {Peltandra virginica), the authors
estimate a reduction in the number of breeding
red-winged blackbirds that currently depend on
the big cordgrass portions of the marshes.553
However, a change to an arrow arum-dominated
marsh may increase bird density and diversity
during winter, particularly for waterfowl and
shorebirds. Arrow arum dies back in winter,
creating an open mud flat that provides
invertebrate prey to birds.554
Mathews County
The Mathews County shoreline, bordered by
Mobjack Bay to the south, Chesapeake Bay to
the east, and the Piankatank River to the north,
has a mix of marshes and beaches. Planners
indicate that shore protection is likely or almost
certain along Mobjack Bay except for a parcel of
public land near the mouth of the East River. On
the Chesapeake Bay coast of Mathews County,
planners anticipate that the southern third of the
coast is likely to be protected, the middle third is
unlikely to be protected, and the most northern
third, comprising Gwynn's Island (CBIM
location 14) and some Piankatank River
frontage, is almost certain to be protected.
Wetlands and some dunes extend along the
county's southern boundary along Mobjack Bay
and around New Point Comfort (a Natural Area
Preserve) (CBIM location 11). Low elevation
woodlands (maritime forest) extend inland from
the eroding marshes and dune areas and provide
habitat for avian neotropical migrants.555'556 New
553Paxton, B.J. andB.D. Watts, 2002, Bird Surveys of Lee
and Hill Marshes on the Pamunkey River: Possible Affects
of Sea-Level Rise on Marsh Bird Communities, Center for
Conservation Biology Technical Report Series, CCBTR-
03-04, College of William and Mary, Williamsburg, VA,
pp. 2, 25-26.
^ Ibid., p. 17.
555Virginia Department of Game and Inland Fisheries, New
Point Comfort Natural Area Preserve, accessed on August
3, 2006, at:
http://www.dgif. virginia.gov/wildlife/vbwt/site.asp?trail=l
&site=CMT08&loop=CMT.
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[ SECTION 3.12 271 ]
Point Comfort hosts a population of the
northeastern tiger beetle (federally listed as
threatened) and nesting least terns (Sterna
anti liar am).557 Marshes also line tributaries and
the landward facing sides of Winter Harbor
(CBIM location 12), the mouth of Strutts Creek,
just south of Gwynn's Island, and the southern
bank of the Piankatank. On the Piankatank,
marsh areas frequently front higher elevation
areas.558 Beaches, most showing signs of high
erosion rates, front much of the Chesapeake-
facing shore (e.g., adjacent to Winter Harbor,
along Bethel Beach, Rigby Island, and Gwynn's
Island). Marshes and unnourished beaches on the
Piankatank are likely to be lost, because
migration inland will be limited by the greater
than 10 foot elevations. The marsh areas are
expected to accrete sufficient sediment to only
keep pace marginally with a 2 mm per year
increase above current sea level rise rates, and
are likely to be lost with a 7 mm per year rate
increase (Section 2.1). Loss of marsh area will
lead to loss of the species that depend on it, as
described above.559
Bethel Beach (CBIM location 13), a natural area
preserve separating Winter Harbor from
Chesapeake Bay, is currently migrating inland
over an extensive salt marsh area.56" The beach is
undergoing high erosion,561 and is home to a
population of the northeastern beach tiger beetle
(federally listed as threatened) and a nesting site
for least terns, which scour shallow nests in the
sand. In the overwash zone extending toward the
marsh, a rare plant is present, the sea-beach
knotweed (Polygonum glaacam). The marsh is
556Virginia Department of Conservation and Recreation,
New Point Comfort Natural Area Preserve, accessed on
August 29, 2006, at:
http://www.state.va.us/dcr/dnli/newpoint.htm.
557Ibid.
558Berman, M.R., Berquist, H„ Dewing, S., Glover, J.,
Hersliner, C.H., Rudnicky, T., Schatt, D.E., and Skunda,
K., 2000, Mathews County Shoreline Situation Report,
Special Report in Applied Marine Science and Ocean
Engineering No. 364, Comprehensive Coastal Inventory
Program, Virginia Institute of Marine Science, College of
William and Mary, Gloucester Point, VA.
559Lippson and Lippson 2006, pp. 201-239 (see note 2).
56"Gary Fleming email on September 11, 2006 (see note
76), including information regarding Bethel Beach.
561Berman et al., 2000 (see note 558).
also one of few Chesapeake Bay nesting sites for
northern harriers (Circus cyaneas), hawks that
commonly nest in more northern areas.562
Although the shore is able to continue to
migrate, these habitats will remain intact, but
eventual overwash and inundation of the marsh
will lead to the loss of the sea-beach knotweed
and the northeastern beach tiger beetle
population, as well as the nesting area for least
terns and northern harriers.563
Middlesex County
Middlesex County lies on the northern portion of
the Middle Peninsula, bordered on the south by
the Piankatank River and on the north by the
Rappahannock River. The river and bay
shorelines are primarily beach, with marsh areas
in coves and tributaries such as Broad Creek. As
the Rappahannock shore forms a point near Mill
Creek, the shoreline becomes predominantly
marsh. Stove Point (CBIM location 16) is a
defining land feature, an arm of land reaching
south into the Piankatank and forming Fishing
Bay (CBIM location 15). Its entire eastern shore,
approximately 75 percent of which is beach, is
protected by bulkheads and riprap as well as a
continuous groinfield along its length. Roughly a
third of the beach area has high rates of erosion.
The peninsula of Middlesex County north and
east of Fishing Bay is narrowly connected to the
rest of the county between Jackson and Sturgeon
creeks. Groinfields, riprap, and bulkheading
border the whole peninsula and extend into some
of the tributaries, limiting possibilities for
shoreline migration.564
Apart from the southernmost end of Stove Point,
and three small areas on the Rappahannock,
planners indicate that shore protection in
562Virginia DCR Bethel Beach fact sheet, accessed at:
http://www.dcr.virginia.gov/dnli/pgbethel.pdf on August 3,
2006.
563Author's analysis based on biological information for
Bethel Beach (see note 562).
564Berman, M.R., Berquist, H„ Dewing, S., Glover, J.,
Hersliner, C.H., Rudnicky, T., Schatt, D.E., and Skunda,
K., 2000. Middlesex County Shoreline Situation Report,
Special Report in Applied Marine Science and Ocean
Engineering No. 368, Comprehensive Coastal Inventory
Program, Virginia Institute of Marine Science, College of
William and Mary, Gloucester Point, VA.
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[ 272 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Middlesex County is likely or almost certain.
Most of the county along the Rappahannock
River is already protected with groinfields
extending on both sides of Sturgeon Creek.565
Without nourishment, beaches in this area are
likely to be lost. Off shore from Mill Creek in
the Rappahannock River, Parrott Island,
composed of tidal marsh, will not be protected.
All the marsh areas in Middlesex County may
keep pace with a 2 mm per year increase in sea
level rise rates through accretion, but not likely
with a rate increase of 7 mm per year. Similarly,
Berkeley Island in the Piankatank is unlikely to
be protected (Section 2.1). This island will
potentially be inundated and submerged,
presumably leading to loss of habitat for biota
that typically inhabit these ecological
communities. These may include crustaceans,
mollusks, and other invertebrates that feed on
and fertilize the marsh vegetation and the turtles
(e.g. diamondback terrapins) and birds (e.g.
ducks, rails) that forage on them. Habitat for
forage and game fish that spend portions of their
lives in wetlands will be lost, as will nesting
habitat for marsh obligate birds.566 Islands are
also a particularly desirable nesting habitat for
birds, owing to the general absence of larger
mammalian predators.567
Wrapup
The three areas where specific data are available
for the Middle Peninsula are vulnerable to sea
level rise. First, the Guinea Neck marshes will
potentially be converted to open water under an
increased rate of sea level rise scenario of 2 mm
and most likely will be converted at 7 mm
(Section 2.1). Presumably, as in other marsh
areas, this will result in impacts to the
invertebrates such as crabs and shrimp that use
the vegetation,
and the birds that feed on them. Likewise, it will
eliminate nesting and forage habitat for birds and
fish. Second, Bethel Beach may survive with
sufficient sediment input, and continued lack of
shoreline protections, allowing for survival of
the area's northeastern beach tiger beetle and the
rare sea-beach knotweed. The beach portion is
already experiencing high erosion, and it is
estimated that a 7 mm increase in rates of sea
level rise might overwhelm the migration
processes and lead to marsh inundation in these
areas. Third, the tidal marshes in the York River
tributaries (the Pamunkey and Mattaponi rivers)
are already impacted by sea level rise, and
vulnerable to future changes, particularly if
changes in salinity drive changes in vegetative
cover. In the forested hardwood marshes of the
upper reaches, increased salinity is expected to
eliminate the forested marsh, which will reduce
habitat for eagles and other piscivorous birds.568
In the brackish marshes in the lower Pamunkey
River, inundation may occur if rates of sea level
rise increase by 2 mm per year, and is expected
with an increase of 7 mm per year. Inundation
may increase the percentage of low marsh
vegetation (arrow arum), resulting in reduced
numbers of red-winged blackbirds and other
birds that prefer higher marsh areas, yet habitat
for wintering waterfowl would be enhanced
because of the likelihood of increased mud flats
in winter.569
565Berman et al., 2000 (see note 564).
566Author's analysis based on biological information in
Lippson and Lippson, 2006, pp. 201-239 (see note 2).
567Eyleret al., 1999 (see note 78).
568Author's analysis based on discussion with Gary
Fleming, and onRobbins andBlom, 1996 (see note 552).
569Author's analysis based on Paxton and Watts, 2002 (see
note 553).
-------
3.13 The Chesapeake Bay Shoreline of
Northern Neck
Authors:Ann Shellenbarger Jones, Industrial Economics Inc.,
Christina Bosch, Industrial Economics Inc.
Overview
The Northern Neck's Chesapeake Bay shoreline
comprises Lancaster and Northumberland
counties. The Northern Neck has marsh and
beach shoreline, with heavily armored areas
along developed shores of the Potomac.
This brief literature review discusses species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection. Existing literature and knowledge of
coastal scientists in the area appears to be
sufficient in many cases to make qualitative
statements about the possible impact if sea level
rise causes a total loss of habitat, which might be
expected if shores are protected with hard
structures and the wetlands are unable to keep
pace with sea level rise. Our ability is more
limited, however, to say what the impact might
be if only a portion of the habitat is lost. The
overall environmental impact of sea level rise in
this multicounty region is likely to include the
following:
• The tidal marshes may be lost with rising sea
levels, including the marsh-fringed Mosquito
Island. The many rare birds that nest in the
Northern Neck marshes, including least
bitterns, king rails, and black rails, will lose
habitat. In addition, the crustaceans,
mollusks, and other invertebrates that live in
close association with the wetland vegetation
will be lost. Ecological impacts will be
similar to those expected for other marsh
areas that will be lost. That is, habitat for fish
that depend on marshes for nurseries and
spawning will be lost, as will nesting habitat
for marsh obligate birds. The ecosystem
functions of flood control, erosion buffering,
and nutrient and contaminant filtering will be
lost as wetlands are submerged.57"
57llLippson and Lippson 2006, pp. 201-239 (see note 2).
• In Northumberland County, shoreline
protections will preserve inland areas, but
beach erosion will be likely in unnourished
areas. Absent site-specific information for
areas other than Hughlett Point, presumably,
if beaches are lost to sea level rise, the few
plants that are well adapted to the harsh
beach environment will be lost, and
invertebrates, including the northeastern tiger
beetle, sand diggers, sand fleas, and crab
species, will be lost. Shorebirds that rely on
beaches for forage and nesting (e.g.,
turnstones, sanderlings, and plovers) will
face more limited resources.571
Lancaster County
Apart from the peninsular area of North Point
(CBIM location 18) in Lancaster County,
planners indicate that the county's bay shoreline
will almost certainly be protected against rising
sea levels. They also indicate that shore
protection is unlikely on the county's
Rappahannock shore (a primarily agricultural
area near the border with Richmond County) and
on Mosquito Island (CBIM location 17 in the
Rappahannock River). Scrub-shrub, forest, grass
and agricultural land cover dominate the
shorelines. Although inland migration will not be
blocked by protections, the land area is small and
as such has limited space in which migrating
marshes and forests may establish themselves.572
Further reducing the likelihood of the area's
ability to adapt to rising sea levels, planners
anticipate that with a 2 mm per year increase in
571Lippson and Lippson 2006, pp. 26-42 (see note 2).
572Berman, M.R., Berquist, H„ Dewing, S., Glover, J.,
Hershner, C.H., Rudnicky, T., Schatt, D.E., and Skunda,
K., 2001, Lancaster County Shoreline Situation Report,
Special Report in Applied Marine Science and Ocean
Engineering No. 371, Comprehensive Coastal Inventory
Program, Virginia Institute of Marine Science, College of
William and Mary, Gloucester Point, VA.
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[ 274 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
the rate of sea level rise, marshes will marginally
be able to retain current area (Section 2.1).
Lancaster County's bay and river shoreline has
interspersed marsh and beach areas, with beaches
typically occurring at points, and marshes in
coves. Shorelines of Fleet's Bay and Dymer,
Tabbs, and Antipoison creeks are covered by
marshes with minimal erosion rates. Groinfields
stretch from either side of Tabbs Creek in Fleet's
Bay, around Clark Point in Little Bay, and west
of Rones Bay in Dymer Creek. Similar
protections are found at the mouth of Mosquito
Creek and at the end of Mosquito Point on the
Rappahannock River. Riprap is also present
along many discrete portions of the county
shoreline.573 Shoreline marshes will possibly be
maintained through accretion with a 2 mm per
year acceleration in sea level rise, but most areas
will be lost under a 7 mm per year acceleration
scenario (Section 2.1). The Virginia brackish
marshes are home to a large number of rare
birds, including the least bittern, the king rail,
and the black rail. The rails eat insects,
crustaceans, and seeds, and the least bittern feeds
on fish or other small animals.574 Marsh
submersion will lead to loss of these food
sources for these rare birds, and for more
common marsh birds such as the herons and
egrets. Habitat for forage and game fish that
spend portions of their lives in wetlands will be
lost, as will nesting habitat for marsh obligate
birds.575
Northumberland County
Northumberland County is densely developed
along the Potomac River and on the Chesapeake
Bay shoreline. Of 558 miles of Northumberland
County shoreline surveyed, approximately 80
percent had marsh coverage, and the remaining
20 had beach.576 Planners indicate that most of
the county will be protected, leading to likely
loss of unnourished beaches and marsh areas
through erosion and inundation as a result of the
inability to retreat inland and lack of sufficient
sediment inputs. Hughlett Point Natural Area
Preserve, at the midpoint along the Northern
Neck's Chesapeake Bay shoreline, has forest
areas fronted by estuarine marshes and sandy
beaches line most of its shore (CBIM location
19). The preserve hosts a population of
northeastern beach tiger beetles and nesting
diamondback terrapins and provides a resting
point for migratory birds. In addition, gray foxes
(Urocyon cinereoargenteus) and river otters
(Lontra canadensis) are present.577 Presumably,
if beaches are lost to sea level rise, the few plants
that are well adapted to the harsh beach
environment will be lost. Habitat for insects and
other invertebrates such as sand diggers, sand
fleas, and beach tiger beetles will be lost.
Shorebirds that rely on beaches for forage and
nesting (e.g., turnstones, sanderlings, and
plovers) will face more limited resources.578 Loss
of the marsh areas will lead to ecological effects
as described for Lancaster County.
Wrapup
The Northern Neck marshes of Lancaster County
will be marginal with an increase of 2 mm per
year over current rates of sea level rise and will
most likely be lost with an increase of 7 mm,
eliminating habitat for rare marsh birds. The
beaches of Northumberland County are likely to
be eroded in front of the expected shore
protections, and lost without nourishment.
Hughlett Point Natural Area Preserve may be
inundated with an increase of 7 mm in sea level
rise rates, eliminating habitat for a variety of
species, including the federally listed threatened
northeastern beach tiger beetle and migratory
birds.
573Berman et al., 2001 (see note 572).
574Rare Marsh-Nesting Birds of Virginia's Coastal Plan.
Natural Heritage Resources Fact Sheet. Accessed online at
http://www.state.va.us/dcr/dnli/inrslifact.htm on June 13,
2006.
575Lippson and Lippson 2006, pp. 201-239 (see note 2).
576Berman, M.R., Berquist, H., Killeen, S., Hersliner, C.H.,
Rudnicky, T„ Schatt, D.E., Weiss, D., and H. Woods,
2002, Northumberland County Shoreline Situation Report,
Special Report in Applied Marine Science and Ocean
Engineering No. 379, Comprehensive Coastal Inventory
Program, Virginia Institute of Marine Science, College of
William and Mary, Gloucester Point, VA.
577Virginia Department of Game and Inland Fisheries, n.d.,
Hughlett Point Natural Area Preserve, accessed on August
3, 2006, at:
http://www.dgif. virginia.gov/wildlife/vbwt/site.asp?trail=l
&site=CNN12&loop=CNN.
578Lippson and Lippson 2006, pp. 26-42 (see note 2).
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3.14 Lower Potomac
Authors: Elizabeth M. Strange, Stratus Consulting Inc.
Ann Shellenbarger Jones, Industrial Economics Inc.
Species and habitats along the lower Potomac
River are potentially at risk because of sea level
rise. This study region encompasses the estuarine
portion of the tidal Potomac downstream of
Mattawoman Creek to Chesapeake Bay. The
region contains important habitats for a variety
of fish, shellfish, and birds, and a great deal is
known about the ecology and habitat needs of
these species. Based on existing literature and
the knowledge of local scientists, this brief
literature review discusses those species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection (see map in Chesapeake Bay review).
Although it is possible to make qualitative
statements about the ecological implications if
sea level rise causes a total loss of habitat, our
ability to say what the impact might be if only a
portion of the habitat is lost is more limited. A
total loss of habitat might be expected if shores
are protected with hard structures and the
wetlands are unable to keep pace with sea level
rise.
The Lower Potomac's shorelines pass through
St. Mary's and Charles counties in Maryland and
Westmoreland and Northumberland counties in
Virginia's Northern Neck. The Maryland side is
largely rural and agricultural, but population and
development there are growing rapidly.
Northumberland County is densely developed
along the Potomac River and on the Chesapeake
Bay shoreline. Westmoreland County lies
entirely along the Potomac, north and west of
Northumberland County. The county is highly
developed, but also has many conservation areas.
The habitats found in the Lower Potomac and
their likely responses to sea level rise include the
following:
• Freshwater tidal marshes in the Lower
Potomac are found in the headwaters of tidal
tributaries. These marshes are currently
keeping pace with sea level rise, largely
through sediment and peat accumulation, and
are expected to continue to do so (and
possibly expand in some areas), even if sea
level rise rates increase by 2 mm/yr or 7
mm/yr (Section 2.1).
• Brackish tidal marshes border the Lower
Potomac River and the downstream portions
of the estuary's tributaries. These marshes
are keeping pace with sea level rise today,
but are considered marginal with a 2 mm/yr
increase in the rate of sea level rise, and
likely to be lost to open water or replaced by
submerged aquatic plants with a 7 mm/yr
increase above the current rate (Section 2.1).
• Unnourished beaches and tidal flats of the
Lower Potomac are likely to erode as sea
levels rise. Where shores are protected with
bulkheads and revetments, erosion will also
occur.
• The cliffs and bluffs along the Lower
Potomac are unlikely to be protected in most
areas (e.g., Westmoreland State Park,
Caledon Natural Area). Natural erosional
processes will continue, helping to maintain
the beaches below.
• Where submerged aquatic vegetation (SAV)
occurs along coves, shoreline armoring may
lead to loss of SAV due to increased wave
energy.
Lower Potomac, Maryland Shoreline
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[ 276 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
The State of Maryland estimates that there are
close to 3,440 ha (8,500 acres) of coastal tidal
wetlands in the Lower Potomac River watershed,
which extends from the mouth of the Potomac in
St. Mary's County upstream to Mattawoman
Creek in Charles County. This estuarine portion
of the tidal Potomac contains mostly brackish
marsh along the Potomac shoreline, with
freshwater tidal wetlands in the upper reaches of
tributaries such as St. Mary's River.579
In St. Mary's County, the Potomac River
shoreline, as documented in the County
Shoreline Situation Report, is a mix of marsh (20
percent) and beach (35 percent); the remainder is
armored or low vegetated banks. Approximately
30 percent of the shoreline is currently protected,
primarily with riprap. Along both the Potomac
and its tributaries, most of the banks are low (< 5
feet), undergoing minimal erosion, and fully
vegetated.58" The narrow tidal wetlands are about
equally divided between areas considered likely
to be protected and almost certain to be
protected. These marshes are not expected to
keep pace with a 7 mm/yr increase in the rate of
sea level rise, but they might be able to keep
pace with a 2 mm/yr increase in the rate of sea
level rise, depending on how the wetlands are
managed (Section 2.1).
In the Wicomico River, St. Clements Bay, and
Breton Bay, shoreline banks are fronted by
marsh (40 percent of shoreline) and a small
amount of beach (15 percent); under 20 percent
of the shoreline is currently protected.581
Shoreline protections are likely or almost certain
at the mouths of the St. Mary's River, Breton
Bay, and the Wicomico River.
Areas adjacent to more rural areas on the
Maryland side of the Lower Potomac (e.g.,
inland side of St. George's Creek, Clements Bay)
579Clearwater, D., P. Turgeon, C. Noble, and J. LaBranche, 2000,
An Overview of Wetlands and Water Resources of Maryland,
prepared by the Maryland Department of the Environment for the
Maryland Wetland Conservation Plan Work Group, January.
580Berman, M.R., Berquist, H., Dewing, S., Hershner, C.H.,
Rudnicky, T., Barbosa, A., Schatt, D.E., Weiss, D., and H.
Woods, 2003, St. Mary's County, Maryland Shoreline Situation
Report, Comprehensive Coastal Inventory Program, Virginia
Institute of Marine Science, College of William and Mary,
Gloucester Point, VA, Tables 6 and 7.
581Ibid.
are unlikely to have shore protections, allowing
the possibility of shoreline retreat. Tidal
freshwater marshes at the upper reaches of the
Wicomico River, St. Clement's Bay, and Breton
Bay could benefit from more fluvial sediments
resulting from increased storms resulting from
climate change (Section 2.1).
The seasonally flooded Zekiah Swamp
Environmental Area, which feeds the Wicomico
River, contains freshwater tidal marsh that
should be able to maintain pace with a moderate
increase in the rate of sea level rise (Section 2.1).
However, salt-water intrusion could lead to
crown dieback, tree mortality, and potential
infilling of the understory with salt marsh
vegetation such as Spartina.5S2 Nonetheless,
given the swamp's relatively large area and
water volume, if such detrimental effects occur
they are likely to be contained to the Wicomico
River end of the swamp.
At the mouth of the Wicomico are the developed
areas of Wicomico Beach and Cobb Island. Cobb
Island has docks, piers, and sandy beaches along
its Potomac side, beaches and marsh along the
mainland side, and predominantly beach
shorelines along the low (0-5 feet) adjacent
mainland areas (Cobb Neck). Cobb Island is
almost certain to be protected (most areas
already are), which is likely to lead to erosion of
beaches and conversion of tidal flats to open
water without other actions. On the mainland
section, shore protection is likely and armoring is
almost certain to protect the homes along Swan
Point Neck. Wetlands are likely to be inundated
in the western Swan Point section of Cobb Neck
because of armoring and insufficient sediment
accretion.
Farther up the Potomac toward Port Tobacco and
the Nanjemoy Peninsula, the majority of the
Potomac shoreline is unlikely to be protected,
and brackish marshes along the shore will be
able to retreat in response to sea level rise.
Despite armoring of Port Tobacco, accretion
rates for the tidal freshwater marshes at the head
of the Port Tobacco River are most likely
sufficient to allow the marshes to keep pace with
a 7 mm/yr increase in the current rate of sea level
582Fleming et al., 2006 (see note 67).
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[ SECTION 3.14 277 ]
rise. Based on its status as a military site,
protection is uncertain at the Blossom Point
Proving Ground's highly eroding marshes on the
eastern side of the mouth of Nanjemoy Creek.
The Nanjemoy Peninsula is considered an area of
great ecological significance and therefore TNC,
the Conservation Fund, the Conservancy of
Charles County, the Maryland Department of
Natural Resources, and the federal Bureau of
Land Management have all sought to acquire and
carefully manage the area.583 The TNC-owned
rookery along Nanjemoy Creek contains one of
the largest great blue heronries on the East Coast.
Blue herons nesting within the rookery feed on
fish and other aquatic organisms found in the
peninsula's wetlands and the shallow waters of
the creek and the Potomac River; TNC has also
purchased an option for 850 ha (2,100 acres)
along Nanjemoy Creek to protect the dwarf
wedge mussel, a federally and state-listed
freshwater mussel. The creek is one of only four
known sites where the mussel is found within
Maryland, and is considered the largest and most
viable population in the state.584
The remaining shoreline along the Lower
Potomac in Maryland is characterized by highly
eroding beaches up through Mattawoman Creek.
These shorelines are unprotected and primarily
adjacent to agricultural lands, which should
allow for shoreline migration. Two areas of
marsh, one at Halfway Creek and one with high
erosion at Mallows Bay, break up the beach
shorelines in this reach of the Potomac River.
Where brackish tidal marshes are lost, nesting,
foraging, roosting, and stopover areas for
migrating birds would be lost. Significant
concentrations of migrating waterfowl forage
and overwinter in the marshes of the Lower
Potomac in fall and winter, including black duck,
greater and lesser scaup, brant, mallard, Canada
goose, northern pintail, oldsquaw, and scoters.
Herons and egrets feed on fish and invertebrates,
and ducks feed on seeds and submerged plants.
Rails, coots, and migrant shorebirds are transient
species that feed on fish and invertebrates in and
around the marshes and tidal creeks. The rich
food resources of the tidal marshes also support
rare bird species such as bald eagle, which nest
in nearby wooded areas and feed on fish and
invertebrates in marshes and tidal creeks, and
northern harrier, which nest and forage in
marshes.585
Fish species common in the brackish waters of
the region include resident marsh species such as
killifishes, anchovies, silversides, blennies,
gobies, and hogchoker. Striped bass and white
perch move in and out of marshes year-round.
Anadromous fishes, including herrings and shad,
as well as marine transients such as Atlantic
menhaden and drum species, are present in late
spring and early fall.586 The most visible
invertebrates of the brackish marshes are red-
jointed fiddler crab, marsh periwinkle, Atlantic
ribbed mussel, and common clam worm.587
The tidal freshwater marshes support additional
species that are rare in brackish environments.
Green frog, southern leopard frog, redbelly
turtle, Eastern painted turtle, Eastern ribbon
snake, and northern water snake are all found in
the tidal freshwater marshes of the Chesapeake
Bay region. Perching birds such as red-winged
blackbirds are common in stands of cattail.588
Without nourishment, beaches and tidal flats in
front of shoreline protections in this area will
erode as seas rise. These habitats often contain a
high diversity and abundance of species ranging
from microscopic organisms that live between
sediment grains and can reach 2 billion
individuals per square meter589 to filter-feeding
bivalves and deposit-feeders such as fiddler
crabs and mud snails found just below the
surface. In turn, numerous predators feed on
583U.S. Bureau of Laud Management, 2004, Lower Potomac
River Proposed Coordinated Management Plan, prepared in
cooperation with the State of Maryland Department of Natural
Resources, Annapolis. April, p. 72.
584Maryland Department of Natural Resources, 2005, Maryland
Tributary Strategy, Lower Potomac River Basin Summary Report
for 1985-2003 data, Maryland Department of Natural Resources,
Annapolis, p. 2.
s White,
586White,
587White,
588White,
1989, pp. 107-123 (see note 25).
1989, p. 85 (see note 25).
1989, p. 124 (see note 25).
1989, pp. 107-109 (see note 25).
Bertness, 1999, p. 256 (see note 133).
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[ 278 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
these invertebrates, including snails, blue crab,
and a variety of fishes and birds.59"
Lower Potomac, Virginia Shoreline
On the Virginia side of the Lower Potomac,
shoreline protection is almost certain throughout
Northumberland County, with shoreline
protection already in place for much of the
developed land (see Section 3.14). Beaches and
tidal flats line the Potomac shore of
Northumberland County, and low vegetated
banks and brackish marsh edge the many coves
and inlets.591 Most of the county is almost certain
to be protected, leading to erosion of
unnourished beaches and preventing marsh
migration.
In Westmoreland County, from the Yecomico
River to Currioman Bay, most areas are likely or
almost certain to be protected. Much of the likely
protected areas of the Potomac shoreline are
bordered by brackish marshes, which may be
inundated under most sea level rise acceleration
scenarios due to insufficient accretion and the
inability to migrate. In these areas, wetlands may
be replaced by SAV beds.
Farther upstream, Westmoreland State Park has
undeveloped bluffs up to 45.7 m (150 ft) high
with narrow sandy beaches along the shore. With
shoreline protection unlikely, continued cliff
erosion is presumed, which will provide
sediment to maintain the beach toe against
increasing sea level rise.
The highly developed areas near Colonial Beach
are almost certain to be protected. Although
some brackish marshes may be lost along the
Potomac shore, tributaries on either side of the
area are unlikely to be protected, which should
preserve wetland habitats in these areas.
However, unless nourished, the rocky, sandy
shoreline at Colonial Beach may be lost due to
the close proximity of residential development to
the water.
590For general information on the fauna of soft-sediment habitats,
see Bertness, 1999 (see note 133).
591Berman et al., 2002, Northumberland, Table 4 (see note 576).
In King George County, the Mathias Point Neck
area is almost certain to be protected, The
shoreline is a mix of narrow sand beaches,
wooded banks, and marsh areas, with jetties and
docks extending into the water. There is a large
fringing bed of SAV, dominated by milfoil, wild
celery, and hydrilla,592 from the Upper Machodoc
Creek to Mathias Point, with smaller beds
between Mathias Point and Quantico.593
Farther upstream are the Caledon Natural Area
and the adjoining Chotank Creek Natural Area
Preserve, which is part of the Cedar Grove Farm
conservation easements. At the eastern edge of
the Caledon Natural Area, shoreline protection is
likely on the northern side of Chotank Creek.
Protection is unlikely, however, on the southern
side of the creek, which may allow sufficient
area for wetland migration.
The Caledon Natural Area and the Chotank
Preserve provide a diversity of habitats that are
potentially vulnerable to sea level rise and
shoreline protection. Along the shoreline at
Caledon is a narrow strip of sand-gravel beach
backed by freshwater tidal marsh dominated by
cattails and Phragmites. In shallow areas, the
marshes are dominated by pickerelweed and
arrow arum. Marsh areas are backed by swamp
forest of sweet gum and oak. Some of the swamp
trees that have died because of excess standing
water now provide nesting sites for bald eagles.
Red headed woodpeckers are also seen nesting in
these areas.
Even if the rate of sea level rise increases by 7
mm per year, these marshes are likely to be able
to migrate inland. The marshes provide habitat
for catfish, perch, sunfish, and carp, and support
numerous turtles, including the red-eared palm
slider and its close relative the yellow-belly palm
slider, painted turtles, and snapping turtles.
Green heron, great blue heron, and the
592
"Species of SAV are provided as examples; in reality, species
vary annually. Long-term trends in SAV from DC to Maryland
Point are described in Rybicki, N.B. and J. M. Landwehr, 2007,
"Long-term changes in abundance and diversity of macrophyte
and waterfowl populations in an estuary with exotic macrophytes
and improving water quality," Limnology' and Oceanography
52:1195-1207.
593Maryland Department of Natural Resources, 2005, Maryland
Tributary Strategy, p. 15 (see note 584).
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[ SECTION 3.14 279 ]
occasional egret feed on fish and invertebrates in
the marshes. Jones Pond within the marsh was
breached by Hurricane Ernesto and is now tidal.
The pond attracts numerous waterfowl, including
Canada geese, tundra swan, and many duck
species, including mallards, canvasback, and
black ducks. Upstream of Caledon, residential
developments line the shore, which is primarily
composed of sandy beaches along the Potomac,
with freshwater tidal marshes in the upper
reaches of tributaries.594 In the more densely
developed areas, shoreline protection is almost
certain. Similarly, even in the less dense areas,
shore protection is likely. Shoreline protections
will inhibit any inland migration of these
shoreline habitats.
With the exception of the southern edge of the
headwaters of Potomac and Accokeek creeks,
protection is likely or almost certain throughout
this region. Between these creeks lies the 1,619
ha (4,000 acre) Crow's Nest Peninsula, an area
of substantial conservation interest as well as a
target for potential development. The peninsula
is ecologically noteworthy for its 1,416 ha (3,500
acre) of unfragmented mature hardwood forest,
considered the finest remaining example in the
Mid-Atlantic coastal plain, and 283 ha (700 acre)
of undisturbed tidal freshwater marsh. The
marshes include three vegetation zones, defined
according to elevation in relation to mean low
water. Below mean low water is a zone of yellow
pond lily with clusters of American lotus. Next
are mixed stands of pickerelweed, arrow arum,
spatterdock, and wild rice. At the highest
elevation is a zone of marsh hibiscus, smartweed,
cardinal flower, big cordgrass, jewelweed, and
beggar-ticks.595
In addition to their value as a rare example of
pristine freshwater tidal marsh, the marshes of
Crow's Nest Peninsula provide habitat for
numerous bird species, including some 26
species of waterfowl that use the freshwater tidal
marshes and wooded swamps for nesting,
migration, and overwintering habitat. These
include 10 of 13 North American Wildlife
Conservation Association Priority Wildlife
Species. There is also a large great blue heron
rookery along upper Potomac creek that supports
more than 600 nests. The marshes also provide
valuable spawning and nursery habitat for a
number of economically important recreational
and commercial fish species, including striped
bass, alewife, blueback herring, white perch,
hickory shad, and yellow perch.596
Although currently not developed, the potential
for future development makes shore protection
along Crow's Nest Peninsula likely. The fringing
wetlands would be unable to migrate in these
areas if shore protections were implemented (and
potentially unable to migrate in the absence of
protections, given the bank heights in many
areas). However, sediment accretion is likely to
be sufficient to maintain wetlands in place even
if the rate of sea level rise increases by 7 mm per
year above the current rate.
In Aquia Creek, to the north of Crow's Nest
Peninsula, shoreline protection is almost certain.
Several areas already have breakwaters (e.g.,
eastern shore of Aquia Landing) that might
disrupt sediment transport, potentially preventing
sufficient marsh accretion (e.g., in the freshwater
tidal marshes on the western side of Aquia
Landing). Sandy beach occurs near the mouth of
Aquia Creek. The remainder of the county
shoreline north of Aquia Creek is also primarily
sandy beach, about two-thirds considered by
planners as likely to be protected and one-third
almost certain. Without nourishment, these
beaches are likely to be eliminated in areas
where armoring restricts shoreline retreat.
594NOAA, 2005 (see note 538).
595USFWS, 2000, Final Environmental Assessment: Proposed
Accokeek National Wildlife Refuge, USFWS Region 5, October,
pp. 11-12 . 596USFWS, 2000, pp. 12-18 (see note 595).
-------
3.15 Upper Potomac
Authors: Elizabeth M. Strange, Stratus Consulting Inc.
Ann Shellenbarger Jones, Industrial Economics Inc.
Species and habitats along the Upper Potomac
River are potentially at risk because of sea level
rise. The Upper Potomac extends from
Mattawoman Creek upstream to the head of tide
of the Potomac River near Georgetown in the
District of Columbia (DC) and to the head of tide
of the Anacostia River near Bladensburg,
Maryland. The region contains important
habitats for a variety of fish, shellfish, and birds,
and a great deal is known about the ecology and
habitat needs of these species. Based on existing
literature and the knowledge of local scientists,
this brief literature review discusses those
species that could be at risk because of further
habitat loss resulting from sea level rise and
shoreline protection (see map in Chesapeake Bay
review). Although it is possible to make
qualitative statements about the ecological
implications if sea level rise causes a total loss of
habitat, our ability to say what the impact might
be if only a portion of the habitat is lost is more
limited. A total loss of habitat might be expected
if shores are protected with hard structures and
the wetlands are unable to keep pace with sea
level rise.
The Upper Potomac is the tidal freshwater
portion of the river (salinity less than 0.5 ppt). In
this area, the Potomac's eastern shore passes
through Charles and Prince George's counties,
Maryland, and DC; the western shore passes
through King George, Stafford, Prince William,
Fairfax, Alexandria, and Arlington counties in
Virginia.
With accelerated sea level rise, the habitat effects
in this study region may include the following:
• Tidal freshwater marshes are unlikely to be
lost, at least not in their entirety. A panel of
accretion experts convened for this report
concluded that tidal freshwater marshes in
the Chesapeake Bay region can keep pace
with sea level rise, possibly even in the face
of a 7 mm/yr increase in the current rate of
sea level rise (Section 2.1). Thus, it is likely
that the tidal freshwater marshes of Mason
Neck, Dyke Marsh, Roosevelt Island, and the
Anacostia estuary could all keep pace with
sea level rise, even if the rate of sea level rise
increases by 7 mm/yr. However, erosion may
contribute to reductions in the area of
marshes, and migration potential is limited
because of inland development.
• Small pockets of estuarine beach and mudflat
are found at many sites along the shorelines
of the Upper Potomac, and in the DC area
these habitats are backed by coastal wooded
swamps. Some locations (e.g., Indian Head)
have more prominent stretches of sandy
beach, but for the most part unconsolidated
soft-sediment habitats are only a minor
component of the shoreline in the study
region. These shorelines will erode as sea
levels rise, and beaches will be lost except
where there is nourishment.
• Where cliffs and bluffs along the Upper
Potomac are protected to preserve property,
erosional processes may no longer supply
adequate sediment to maintain the beaches
below.
• Where SAV occurs along coves, shoreline
armoring may lead to loss of SAV due to
increased wave energy. Where wetlands
recede, SAV could spread landward via
vegetative spread or if propagules or seeds
reach sites with suitable growing conditions.
Upper Potomac, Maryland shoreline
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[ SECTION 3.15 281 ]
On the Maryland side of the Upper Potomac
River, we do not know whether the Department
of Defense will choose to protect the shoreline at
the Indian Head Naval Surface Warfare Center to
the north of Mattawoman Creek. There is
currently minimal shoreline protection, and if
there is no beach nourishment as seas continue to
rise, sand and mud shorelines will erode. The
town of Indian Head has a developed shoreline
with narrow beaches and piers, and local
planners expect that the town is almost certain to
be protected. Above Fort Washington shoreline
protection is also almost certain; some areas are
already protected with riprap.597 These shorelines
will erode in front of hard structures. Not only
will this eliminate habitat for beach
invertebrates, but increased sedimentation of
nearshore waters will also impair SAV and other
habitat for popular recreational fish species such
as striped bass, largemouth bass, and yellow
perch.
Because of the presence of several large parks
and undeveloped areas, shoreline protection is
unlikely from Indian Head north into Prince
George's County, and the high banks in this area
will prevent migration. However, the tall cliffs
on the Potomac north of the Indian Head facility
are likely to be protected to preserve property at
the top of the cliffs.
Along the natural shorelines of Roosevelt Island
in DC, shore protection is unlikely. The island
consists of both upland and swamp forest as well
as tidal marsh. Fish in the marsh provide food for
herons, egrets, and other marsh birds. Snapping
and painted turtles use the nearshore waters and
shoreline for forage and resting.598 The ability of
the tidal marshes of the island to keep pace with
sea level rise will depend in part on the supply of
sediment. Increased inundation of the swamp
forest with rising seas could result in crown
dieback and tree mortality.599
597Berman, M.R., Berquist, H., Killeen, S., Nunez, K, Rudnicky,
T., Schatt, D.E., Weiss, D. and K. Reay, 2006, Prince George's
County, Maryland—Shoreline Situation Report, Comprehensive
Coastal Inventory Program, Virginia Institute of Marine Science,
College of William and Mary, Gloucester Point, VA.
598National Park Service, Description of Roosevelt Island,
accessed at http://www.nps.gov/gwmp/pac/tri/backgmd.html on
July 20 2006.
599Lippson and Lippson, 2006, p. 218 (see note 2).
Elsewhere in Washington, D.C., the Potomac
shoreline is already largely hardened, and
therefore minimal additional habitat change is
expected as a result of sea level rise. Because it
is a major population center, some form of shore
protection is almost certain throughout the area.
Currently, the District is most likely to use
environmentally sensitive means of shore
protection rather than allowing inland migration.
Some shores of the Anacostia River may prove
an exception to the general approach of
preventing migration. Historically, the Anacostia
included extensive freshwater wetlands. As
human development proceeded, the river was
dredged from its mouth at the Potomac in DC to
Bladensburg, Maryland, and a stone seawall was
built along the shoreline, eliminating virtually all
historical wetlands.6"" The tidal Kingman and
Kenilworth lakes were dredged, but over time
they filled with sediment. In recent decades local
organizations have been working to restore some
of the former wetlands on the sediments in these
lakes. Restoration of the 13 ha (32 acre)
Kenilworth Marsh was completed in 1993;
restoration of the Kingman Lake marshes began
in 2000.601 Other efforts to restore the river
include converting of some seawalls and
bulkheads to woodland buffers. As seas rise,
local planners expect that some marsh migration
may be allowed on Kingman Island, although
parts of the island may also be armored to
continue to protect some dryland uses, resulting
in marsh erosion. Loss of any marsh along the
Anacostia would have a notable impact because
so little of this habitat is left. Monitoring of the
restored habitats demonstrates that these marshes
can be very productive. For example, a recent
bird survey identified 177 species of birds in the
marshes comprising 14 taxonomic orders and 16
families,6"2 including shorebirds, gulls, terns,
passerines, and raptors as well as marsh nesting
o00See website describing wetland restoration in the Anacostia by
Dr. Dick Hammerschlag of the Patuxent Wildlife Research
Center, the lead scientist monitoring recovery of wetland habitats
and biota:
http://www.pwrc.usgs.gov/resshow/liammerschlag/anacostia.cfm.
601Ibid.
o02Paul, M., C. Krafft, and D. Hammerschlag, 2004, Avian
Comparisons between Kingman and Kenilworth Marshes, Final
Report 2001-2004, p. 4. USGS publication available online at:
http://www.pwrc.usgs.gov/resshow/liammerschlag/anacostia.cfm.
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[ 282 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
species such as marsh wren and swamp
sparrow.6"3
Upper Potomac, Virginia shoreline
On the Virginia side, much of the Prince William
County shoreline of the Potomac is sandy beach,
and almost certain to be protected.6"4 In the few
areas where shoreline protection is unlikely,
marshes will have little opportunity to migrate
because most shores are developed. However,
accretion rates in the Upper Potomac are likely
to be sufficient to meet most sea level rise
acceleration scenarios, including a 7 mm/yr
accelerated rate.
Several state parks and federal wildlife refuges in
Prince William County adjoin the Potomac
shoreline. The Potomac River National Wildlife
Refuge Complex includes the Featherstone
National Wildlife Refuge across from
Leesylvania State Park, the Occoquan National
Wildlife Refuge at the confluence of the
Potomac and Occoquan rivers on Occoquan-
Belmont Bay, and the Mason Neck National
Wildlife Refuge across the Bay on the Mason
Neck Peninsula (Mason Neck).
The parklands on Mason Neck Peninsula are
unlikely to be protected, particularly Mason
Neck National Wildlife Refuge and Mason Neck
State Park. However, adjacent sites on the
eastern end of Mason Neck are almost certain to
be protected, which could potentially affect
sediment transport in the area and thus affect the
ability of the Mason Neck marshes to keep pace
with sea level rise.
Wetland loss will reduce habitat for species that
are particular conservation targets in the refuge.
The Mason Neck National Wildlife Refuge was
originally established to protect the federally
endangered bald eagle. Today, the refuge hosts
seven nesting bald eagle pairs and up to 100 bald
eagles during winter. The refuge also has one of
the largest great blue heron colonies in Virginia,
with an estimated 1,600 nests. In addition to
serving as a major heron rookery and a nesting
site for bald eagles, the marsh also provides
nesting areas for hawks and waterfowl and a
stopover for migratory birds.6"5 Herons feed on
fish and other aquatic species in the marsh, and
teals, mallards, and black ducks feed on marsh
plants and seeds.6"6 Six bird species, classified as
"high priority" by the Atlantic Coast Joint
Venture, use the Mason Neck area as
overwintering and migration habitat. These
include black duck, mallard, pintail, greater and
lesser scaup, and the Southern James Bay
population of Canada goose. The ducks and
Canada goose feed on invertebrates, plant
material, and seeds in the flooded marshes and
adjacent rivers and lakes. Other priority species
such as wood duck, American widgeon, redhead,
canvasback, and ring-necked duck use these
habitats for foraging and resting. Wood duck and
green- and blue-winged teal use the emergent
marshes for brood rearing and staging in fall.6"7
Studies in marshes of Virginia's Eastern Shore
have found a direct relationship between marsh
area and the abundance of bird species in the
marsh.6"8
Upriver is Fort Belvoir, where protection is
uncertain given the military nature of the site.
Accotink Bay, adjacent to the fort, has
significant areas of tidal marshes, which may be
threatened by shore protections at Fort Belvoir.
Among the species using the bay are shorebirds,
waterfowl, and ospreys.6"9
Beyond Accotink Bay, the Virginia shoreline of
the Upper Potomac is almost certain to be
"05Xhe Mason Neck NWR was established in 1969 as the first
federally protected refuge for the bald eagle. A profile of the
refuge is available at
http://www.fws.gov/Refuges/profiles/index.cfm?id=51610.
"""Personal observations of J. Bucknam, interpreter, Mason Neck
State Park and USFWS fact sheet "Mason Neck National
Wildlife Refuge, Potomac River National Wildlife River Refuge
Complex," available at:
http://www.fws.gov/nortlieast/facts/MasonNeck06.pdf.
"^Atlantic Coast Joint Venture, 2005, Revised Waterfowl
Implementation Plan—Focus Area Report, Lower Potomac
River, Virginia, pp. 485—486.
"08Watts, 1993 (see note 61).
"09 Virginia Department of Game and Inland Fisheries, Accotink
Bay Wildlife Refuge, Army Garrison Fort Belvoir. Accessed
December 5, 2007 at:
http://www.dgif. state.va.us/wildlife/vbwt/site.asp?trail=l&site=C
MN05&loop=CMN.
"03Paul et al., 2004, p. 11 (see note 602).
"04NOAA, 2005 (see note 538).
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[ SECTION 3.15 283 ]
protected up through Washington D.C., with the
possible exception of habitats within National
Park Service holdings. The freshwater tidal
marsh within the Dyke Marsh Preserve is one of
the last major remnants of the original freshwater
tidal marshes of the Upper Potomac River,610
making it particularly valuable for local
populations of fish, birds, and other wildlife.
The marsh proper is dominated by cattails, along
with several other common freshwater tidal
marsh plants, including arrow arum, sweetflag,
and spatterdock.611 Adjacent to the marsh, the
Hunting Creek embayment contains one of the
largest mudflats along the Upper Potomac River,
providing forage areas for both migratory and
resident birds.612 A survey of the marsh in 2000
found 62 species of fish, 9 species of
amphibians, 7 species of turtles, 2 species of
lizards, 3 species of snakes, 34 species of
mammals, and 76 species of birds in Dyke
Marsh.613 The rare least bittern and the federally
listed bald eagle breed in the marsh, and
scientists at the University of Maryland believe
that other rare species such as black rail and
American bittern could also breed there.614 The
marsh also contains the only known breeding
population of marsh wrens in the upper tidal
Potomac.615 A fish survey between 2001 and
2004 collected longnose gar, a species on
Virginia's candidate list. There was substantial
evidence of the marsh's importance as juvenile
fish habitat, with large numbers of juveniles
collected, including juveniles of striped bass,
American shad, yellow perch, blueback herring,
and alewife. All of these are species that are
important for commercial and recreational
fisheries in the area. Typical marsh residents
such as killifishes, which provide food for these
estuarine species, were also collected.616
Erosion and subsidence are problems in the
marsh today.617 Previous dredging and marsh
removal may be contributing factors, in part
because these activities eliminated the tidal
creeks that drained the marsh.618 Much of the
current emergent marsh is on a shelf of shallow
water about 0.91-1.22 m (3-4 ft) above mean
low tide and is therefore not inundated during the
marsh's typical 3 ft tidal cycle.619
Scientists analyzing current marsh conditions to
make recommendations to the National Park
Service about restoration of the marsh concluded
that responses of the marsh's vegetation
communities to inundation will require
additional study to predict the effects of sea level
rise on the existing marsh or any new marsh that
is created.62"
°10.Tohnston, D.W., 2000, "The Dyke Marsh preserve ecosystem,"
Virginia Journal of Marine Science 51:223-273, p. 242.
611Ibid.
612Ibid.,p. 228.
0l3Engelhardt, K.A. M., S. Seagle, and K.N. Hopfensperger,
2005, Should We Restore Dyke Marsh? A Management Dilemma
Facing George Washington Memorial Parkway, Final Report,
submitted to the George Washington Memorial Parkway,
National Park Service, National Capital Region, McLean, VA, p.
4.
0l4Gates, J.E., and R. Peet, 2005, Birds of Dyke Marsh Wildlife
Preserve Virginia: A Ten-Year Analysis of Transect Count Data.
Unpublished manuscript submitted to Melissa Kangas of the
National Park Service, National Capital Region National Parks,
McLean, VA. September 5. pp. 25-26.
0l5Johnston, 2000, p. 248 (see note 610).
616Mangold, M. F., R.C. Tipton, S.M. Eyler, and T.M. McCrobie,
2004, Inventory of Fish Species within Dyke Marsh, Potomac
River (2001-2004), U.S. Fish and Wildlife Service in
conjunction with Maryland Fishery Resources Office, Annapolis,
MD, October 22.
0l7Johnston, 2000, pp. 229 and 242 (see note 610).
0l8Engelhardt et al., 2005, p. 2 (see note 613).
0l9Engelhardt et al., 2005, p. 3 (see note 613).
o20Engelhardt et al., 2005, p. 7 (see note 613).
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3.16 Western Shore Chesapeake Bay Shoreline
Authors: Ann Shellenbarger Jones and Christina Bosch
Overview
The western shore region of Chesapeake Bay
includes St. Mary's, Calvert, and Anne Arundel
counties and Baltimore City and County.621 Land
types in these counties vary from major urban
areas such as Baltimore and Annapolis to largely
rural areas in Calvert County. The region,
particularly Calvert County, is characterized by
smoothed shorelines, indicating sufficient
sediment supply and longshore transport as
compared to the more jagged eastern shore's
coves, inlets, and islands.622
This brief literature review discusses species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection. Existing literature and knowledge of
coastal scientists in the area appears to be
sufficient in many cases to make qualitative
statements about the possible impact if sea level
rise causes a total loss of habitat, which might be
expected if shores are protected with hard
structures and the wetlands are unable to keep
pace with sea level rise. Our ability is more
limited, however, to say what the impact might
be if only a portion of the habitat is lost. The
major tributaries to Chesapeake Bay on the
western shore are the Patuxent River, a major
Bay tributary bordering Calvert, St. Mary's,
Charles, and Prince George's counties; the South
River and the Severn River in Anne Arundel
County; the Patapsco River on the southern side
of Baltimore; and the Gunpowder River,
straddling the border of Baltimore and Harford
counties. Western shore tidal wetlands are
primarily located in these tributaries, in
particular, at the mouth of the Gunpowder, at Jug
621 This review looks at ecological implications of sea level
rise from Baltimore County through the northern half of
St. Mary's County, including its Patuxent River shoreline.
622Stevenson and Kearney, 1996, p. 234 (see note 38).
Bay in the Patuxent, and in Sullivan's Cove
Marsh and Round Bay Bog on the Severn. Some
of these tributaries have been dramatically
modified with shoreline protections, yet others
have remained largely unchanged. For example,
the Patapsco formerly supported populations of
anadromous fish, but urbanization along its
banks and installation of dams along its course
have since prevented their migration.623 In
contrast, the Severn's steep cliffs and deep
ravines earned it a designation of Scenic River
by the Maryland General Assembly.
The western shore will see a range of impacts
from sea level rise in the future. Despite large
areas of conservation or parkland and restricted
development (e.g. upper Patuxent River, Calvert
Cliffs), loss of key habitats may occur. The large
degree of shoreline armoring from northern
Calvert County through Baltimore will also
affect shoreline retreat. The overall
environmental impact of sea level rise in this
multicounty region are likely to include the
following:
• Partial or complete marsh loss is expected in
many areas. In the upper Patuxent River,
marsh areas have experienced minimal
migration despite inundation. Saltwater
intrusions may shift the fauna dependent on
nontidal wetlands in Shady Side, particularly
freshwater fish. The potential loss of the
wide mudflats at Hart-Miller Island would
eliminate foraging and nesting for the large
bird population, including many sensitive
species.
• Beach loss, particularly in St. Mary's,
Calvert, and Anne Arundel counties along
623Alliance for the Chesapeake Bay, n.d.. River
Summaries, accessed on May 3, 2006, at http://www.acb-
online.org/about. cfm.
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[ SECTION 3.16 285 ]
Chesapeake Bay, may occur in areas without
nourishment. The widespread presence of
shoreline protection can interfere with
longshore transport. Beach loss or reduction
may occur even in areas where shoreline
retreat is possible. Many invertebrates will
lose their habitat, including the northeastern
beach tiger beetle (federally listed as
threatened).
• The cliffs of Calvert County will not be lost,
but effects from increased rates of sea level
rise and impediments to longshore sediment
transport may increase erosion rates above
sustainable levels for the resident
populations. The Puritan tiger beetle
(federally listed as threatened) may lose
essential habitat.
• Effects on nearshore communities may be
observed. In the upper Patuxent River, the
spread of SAV more tolerant of deeper
depths and higher turbidity (Hydrilld) may be
accompanied by a decrease in larger fish,
though its spread may be tempered by
changes in salinity.624
Sediment deposition is fairly high along the
western shore of Chesapeake Bay, both from
land runoff and erosion. Along the bay
shorelines, marsh areas are expected to be
marginal with a 2 mm per year rate increase in
sea level rise and to be lost with a 7 mm per year
increase. The ability to migrate will most likely
determine their survival. In upper reaches of
tributaries, marsh accretion should be sufficient
to meet a 7 mm per year increase in the rate of
sea level rise (Section 2.1). However, localized
areas may have differing rates of accretion,
subsidence, and erosion, and some wetlands on
the western shore are being inundated (e.g., in
Jug Bay on the upper Patuxent). Planners
indicate that shoreline protections are almost
certain throughout much of Anne Arundel and
Baltimore City/County, which will most likely
lead to the loss of both intertidal areas and
wetlands with sea level rise rate increases of 2
mm per year.
624See Section 3.1 for general background on species and
habitats vulnerable to sea level rise for the mid-Atlantic. It
includes overview information on salinity and other factors
not discussed in detail here.
St. Mary's County, Chesapeake shoreline
Beginning at the southern tip of St. Mary's
County, the bay-front shoreline between the
Potomac and the Patuxent rivers is primarily
narrow sandy beaches with low bank heights
(less than 5 feet). Erosion is a significant
problem: more than half the beach is eroding,
although a large portion of the remaining
shoreline is already stabilized with bulkheads or
riprap.625 Erosion is likely to be a problem on the
beaches fronting shoreline protections and may
be so in other areas as well. In general, beach
loss will lead to habitat loss for resident insects
and other invertebrates and forage loss for larger
predators such as shorebirds.626 Estuarine
marshes line the many small coves. Given
existing erosion, these marshes are unlikely to
accrete or migrate sufficiently to retain their
current size, even in unprotected areas. Wetlands
loss harms the crustaceans, mollusks, and other
invertebrates that live in close association with
the wetland vegetation and the turtles (e.g.
diamondback terrapins) and birds (e.g. ducks,
rails) that forage on them.627 At Point Lookout
State Park (CBIM location 38), a loblolly pine
tidal woodland is already being lost to relative
sea level rise. Saltwater intrusion across the
fronting estuarine marsh is killing trees as a
result of salt stress and increased
inundation.628"629 Tidal hardwoods such as
loblolly pines provide nesting sites for
piscivorous species such as ospreys, bald eagles,
and double-crested cormorants.63"
Patuxent River
Erosion is also an issue in the lower Patuxent
River. The St. Mary's County shoreline is a mix
of low to high banks, mostly with trees and
shrubs or residential development, with
625Berman et al., 2003, St. Mary's County (see note 580).
626Lippson and Lippson 2006, pp. 26-42 (see note 2).
627Lippson and Lippson 2006, pp. 201-239 (see note 2).
628Tiner and Burke, 1995, Plate 7 (see note 32).
629Harrison, J.W., P. Stango III, andM.C. Aguirre, 2004,
Forested tidal wetland communities of Maryland's Eastern
Shore: Identification, assessment, and monitoring,
Maryland Department of Natural Resources, Natural
Heritage Program, Annapolis, MD, unpublished report
submitted to U.S. EPA.
63"Robbins and Blom, 1996, pp. 44 and 92-94 (see note
552).
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[ 286 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
significant erosion rates in the higher banks.631
The immediate shores are primarily vegetated
bank with a minimal intertidal area; roughly 15
percent are fronted by sandy beaches and 25
percent by marshes.632 Erosion is prevalent
through all shoreline types. The Calvert County
shoreline is assumed to be similar in this region.
Planners indicate that shoreline protections are
almost certain for the first few miles of the river,
but further up are unlikely. Given current erosion
rates and low rates of accretion near Chesapeake
Bay, marsh areas are likely to be inundated in the
protected areas. Some marsh migration may
occur at the northern end of St. Mary's County,
but the high banks in many locations will inhibit
migration, resulting in net loss of marsh areas.
North from the Prince George's and Charles
County border, large areas of tidal estuarine
marsh line the Patuxent River, changing to tidal
freshwater above the Anne Arundel County
line.633 Shoreline protection is unlikely in this
area. Sediment inputs are predicted to be high
enough to retain marsh area, but naturalists at
Jug Bay in the upper Patuxent River (CBIM
location 41) have observed inundation and
minimal migration of low marsh, with direct
conversion of wooded or high marsh areas to
open water.634 The marsh has decreased visibly
in size over the last 25 years, with the
appearance of more emergent vegetation (e.g.,
spatterdock, Nuphar liiienm) as water depth
increases. In the Jug Bay Sanctuary, as erosion
continues and water levels rise, spatterdock is
becoming submerged and is being displaced by
the highly invasive Hydrilla verticillata, which
can tolerate deeper waters and reduced light, and
higher suspended sediment loads is filling in
open water and unvegetated mudflat areas.
Spatterdock, a perennial, grows before Hydrilla
631 The St. Mary's County Patuxent River shoreline is more
than 40 percent low bank (0-5 feet), 10 percent medium
(5-10 feet), more than 25 percent high (10-30 feet), and
more than 10 percent above 30 feet. Bennan et al., 2003
(see note 580).
632Bennan et al., 2003 (see note 580).
633Tiner and Burke, 1995 (see note 32).
634Phone conversations on April 27 and December 1, 2006,
and email confirmation "Re: Final review of Patuxent
section of report," of discussions about Jug Bay, and 25
years of observations there, between IEc and Greg Kearns,
naturalist. Jug Bay Natural Area.
in the spring, and has not been affected by the
increase in Hydrilla.635 Although Hydrilla may
displace other native vegetation or become
sufficiently dense to prohibit movement of larger
fish, the species does improve water quality (as
compared to the absence of vegetation) by
trapping sediments, contributing oxygen, and
increasing carbon dioxide uptake, and may
provide sheltering habitat for smaller fish.636 The
increasing water depth has also compounded
stress on local vegetation and on the birds that
feed on the plants. Migrating populations of Sora
rails (Porzana Carolina), a marsh-dependent
species that feed primarily on seed and green
plant matter, declined in Jug Bay throughout the
1990s because of overgrazing of one of their
primary food sources (wild rice, Z. aquatica) by
resident Canada geese (Branta canadensis) 637-638
Wild rice restoration efforts have been affected
by the increasing water depths. The rice survives
regular tidal inundation of up to 2 feet, and
usually stands in roughly 6 to 12 inches of water,
but under additional stresses such as the foraging
of resident Canada geese is less resilient.
Unusually cold and wet weather in the spring of
2005 and 2006, with associated higher water
levels in the marsh, hindered wild rice growth in
the lower marsh. Wild rice in the upper marsh
areas was not adversely affected, and even
635Phone conversation, including description of Hydrilla
and its current presence, characteristics, and relation to
spatterdock in the Patuxent marshes. Greg Kearns,
naturalist. Jug Bay Natural Area, December 1, 2006.
636Nonindigenous aquatic species: Hydrilla verticillata,
accessed on May 30, 2006, at
http://nas.er.usgs.gov/taxgroup/plants/docs/liy_verti.html;
Plant Invaders of Mid-Atlantic Natural Areas, accessed on
May 30, 2006, at
http://www.nps.gov/plants/alien/pubs/midatlantic/liyve.ht
m; and phone conversation with Greg Kearns (see note
636).
637Gough, G.A., J.R. Sauer, andM. Iliff, 1998, Patuxent
Bird Identification Infocenter, version 97.1, Patuxent
Wildlife Research Center, Laurel, MD, available at:
http ://www .mbr-pwrc .usgs.gov/id/framlst/infocenter. html.
638Phone conversation, including discussion of sora rail
populations, dependence on wild rice, and efforts to
monitor and restore wild rice. Greg Kearns, April 27,
2006. Confirmed by email "Re: Final review of Patuxent
section of report," on December 1, 2006. Note:
smartweeds (Polygonum spp.) are also important in diets
of sora rails.
-------
[ SECTION 3.16 287 ]
increased its coverage dramatically in some
areas.639"640
Calvert County/Chesapeake shoreline
Returning to Chesapeake Bay at the mouth of the
Patuxent River, Cove Point (CBIM location 39)
has a unique shoreline formation, the cuspate
foreland. The foreland results when sand is
moved along a shoreline predominantly in one
direction, and then hits a geologic formation that
traps the sand. A point forms with sands
accreting on the downshore side of the cusp.
Cove Point Marsh is a 150-acre freshwater,
barrier-beach marsh on the up shore side of the
cusp. Numerous state-defined rare plant species,
including American frog's-bit (Limnobium
spongid), silver plumegrass (Ericmthus
alopecuroides), various ferns, and unique
wetland communities,641 as well as populations
of the northeastern beach tiger beetle, and the
Puritan tiger beetle (both federally listed as
threatened), and the rare leaf beetle Glyptinci
maritima, are present there. The marsh side is
threatened by storm-driven overwash, sea level
rise, and residential development on the south
side, which has disrupted the migration of the
foreland in recent decades. The marsh is
continuing to migrate, but will soon hit the
northern edge of the development. Shoreline
protections to the north may limit sediment
inputs to the marsh that would otherwise allow
accretion to keep up with sea level rise.642 The
marsh area will slowly be lost as the outer edge
is eroded and inundated, endangering the many
639Phone conversation, including description of
observations of vegetation dynamics by Greg Kearns,
April, 27, 2006, and confirmed by email "Re: Final review
of Patuxent section of report," on December 1, 2006.
Aerial photographs described by Kearns have captured
these changes in wild rice coverage.
64"Wild rice also occurs in the freshwater portions of the
York, Potomac, and Choptank rivers (Lippson and
Lippson, 2006, p. 208, see note 2).
641Steury, B., 2002, "The vascular flora of Cove Point,
Calvert County, Maryland," The Maryland Naturalist
45(2): 1-28, pp. 16, 21.
642Email communication from Katharine McCarthy,
Southern Regional Ecologist, Natural Heritage Program,
Wildlife and Heritage Service, Maryland DNR, to Ann
Shellenbarger Jones and Christina Bosch Industrial
Economics. "RE: Calvert Cliffs State Park" including
confirmation of prior emails, and text in draft report. Sent
September 11, 2006.
rare plants in the marsh. The upstream
protections may be leading to significant erosion
and coincidental loss of northeastern beach tiger
beetle larval habitat areas north and south of the
Cove Point pier, the likely causes of decline in
the local population.643
North of Cove Point are the Calvert Cliffs
(CBIM location 40), which formed during the
Miocene epoch when Chesapeake Bay was a
shallow sea. The cliffs are the remnants of the
sea floor, now standing up to 115 feet above the
water. Fossilized remains are exposed as wind
and water erode the cliffs at a rate up to 2.75 feet
per year.644 The area inland of the cliffs in
southern Calvert County is largely undeveloped
(primarily because of the presence of the Calvert
Cliffs Nuclear Power Station), but more
development is present along the northern
shoreline. The northeastern beach tiger beetle
and the Puritan tiger beetle both depend on the
naturally eroding cliffs and the sandy fronting
beaches of the Calvert Cliffs for habitat, both as
larvae and as adults. Puritan tiger beetle
populations at Calvert Cliffs have been declining
in recent years, in part owing to habitat loss.645
The larvae require a moderate amount of cliff
face erosion, although exact rates are unknown.
Continuous erosion prevents vegetation from
establishing on the beaches or cliffs, maintaining
the necessary bare substrate for the beetles. In
areas where cliff erosion is slowed by increased
toe elevation or armoring, the cliff face subsides
into a more modest slope, and vegetation then
stabilizes it. At Calvert Beach, larvae and adults
were absent from the areas stabilized by
vegetation, but were present on sandy bluff
faces.646 According to a beetle expert, in areas
where beach is entirely submerged at high to
mid-tides, few to no Puritan tiger beetles are
present.647 In contrast to areas stabilized by
643Knisley, C.B., 2000, Population decline of the
northeastern beach tiger beetle in Calvert County, MD.
Final Report, submitted to Cove Point Natural Heritage
Trust, January 18.
644Calvert Cliffs State Park, accessed on May 9, 2006, at
http://www.dnr.state.md.us/baylinks/15.html.
645Knisley, 2000 (see note 643).
646USFWS, 1993 (see note 166).
647Peer review comment by Barry Knisely on this section
on the Western Shore Chesapeake Bay Shoreline, received
July 20, 2007.
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[ 288 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
vegetation, as cliff erosion increases because of
loss of toe elevation, winter storm waves shear
off large portions of cliff and may kill larvae in
localized areas.648 If erosion occurred at rates
high enough to shear of areas to a depth below
larvae burrows, Puritan tiger beetles could be
eliminated. Impacts to adult Puritan tiger beetles
may also occur if sea level rise or increased
erosion diminishes the beach habitats used for
foraging.649
Although natural erosion processes are allowed
to continue in the protected cliff areas in the
southern portion of the county, shoreline
protections in the more northern developed areas
are affecting the Calvert Cliffs shoreline. Effects
on longshore sediment transport from upstream
shoreline protections are an identified cause of
increased erosion rates.65" In addition, there is
increasing pressure for shoreline stabilization
along the more southern shoreline (in particular
near Little Cove Point), and revetments and other
shoreline stabilization projects have been
recently constructed or are proposed.651
Unfortunately, overly rapid erosion is also a
threat to the Puritan tiger beetle, owing to
shearing of cliff habitat. Shoreline protections
are almost certain along much of the developed
northern coast of Calvert County, which may
increase erosion rates in the unprotected southern
cliff areas beyond the range required by the tiger
beetles. In the more northern areas where the
cliffs are stabilized, the rocky and sandy toes to
the cliffs will be lost to inundation with sea level
rise, along with the invertebrate community (e.g.,
burrowing amphipods and hermit crabs) that
resides there.
Anne Arundel County
Anne Arundel County has dense residential
development near its primarily sandy bay
shoreline. Shady Side (CBIM location 42), at the
southern end, is located on a peninsula
64Tr.S. FWS, 1993 (see note 166).
649Barry Knisely (see note 647).
65llWilcock et al., 1998 (see note 161).
651Barry Knisely (see note 647); and USFWS, 2006, Pre-
decisional draft biological opinion on "Chesapeake Ranch
Estates/Phase V/Breakwater," Accessed on July 26, 2007,
at:
http://www.fws.gov/northeast/Endangered/tebo/PDFs/CH
E S .RAN CH .BO. revised%20proj ect6 .pdf.
surrounded on two sides by the West River, and
on a third by Chesapeake Bay. The area is
generally at low elevation above the water level
and highly developed.652 Given the already
severely limited state of tidal wetlands, the
primary effect of sea level rise in Shady Side will
most likely be more frequent upland flood
events. Large portions of the shoreline are
already protected, with future protection almost
certain along most of the shoreline.653 The
interior areas of the Shady Side peninsula are
marked by nontidal wetlands. The myriad creeks
and streams that cross the Shady Side wetlands
provide spawning and nursery areas for
freshwater, estuarine, and anadromous fish such
as striped bass, white perch, spot, croaker, and a
variety of forage fish.654 Increased inundation
events in the nontidal freshwater areas with
higher salinity water could cause significant
habitat decline in freshwater species.655 Farther
north in the county, higher elevations limit the
wetlands close to the coastline. However, Anne
Arundel County does have a policy of
encouraging and supporting nonstructural or
hybrid shoreline protection projects. The County
provides free technical support, site evaluation,
and plant plugs (S. alterniflora and S. patens) for
residents.656 With the likelihood of almost certain
shoreline protections throughout, the current
652The elevation ranges from 3 to 10 feet, with an average
of 7. Anne Arundel County Small Planning Area Plan for
Deale/Shady Side, Section X. Land Use and Zoning, p. 71,
accessed on May 5, 2006, at
http: //www. aacounty. org/PlanZone/S AP/D eale S S. cfm.
653More than 75 percent (1,609 out of 2,120) of parcels
studied had shoreline improvements in place. Michael,
J.A., D.A. Sides, and T.E. Sullivan, 2003, The economic
cost of sea level rise to three Chesapeake Bay
communities. NOAA, Maryland DNR, and Center for
Geographic Information Sciences at Towson University.
654Anne Arundel County Small Planning Area Plan (see
note 652).
655Bay waters at Shady Side average between 5-10 ppt
salinity in spring and summer and 10-15 ppt in fall.
Average Surface Salinities Map, accessed on May 30,
2006, at:
http://mddnr.chesapeakebay.net/eyesonthebay/images/bay
_salinity.jpg.
656Anne Arundel County, Maryland, Office of
Enviromnental and Cultural Resources, 2006, Emergent
Marsh Grass Re-Vegetation Program, available at:
http://www.aacountv.org/LandUse/OECR/EmergentGrasse
s.cfrn. Program discussed in phone conversation with Jim
Johnson, May 30, 2006.
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[ SECTION 3.16 289 ]
intertidal areas will be inundated by sea level
rise. The fringing marshes created through Anne
Arundel County's shoreline projects may
provide key habitat for marsh invertebrates in
addition to protecting upland areas. Several rare
birds, including the black rail (Laterallus
jamaicensis), which is listed by the DNR as in
need of conservation, breed in the Anne Arundel
County marshes.657
Baltimore City and County
Planners in both Baltimore City and County
anticipate that shore protection is almost certain
throughout the area. Almost half of the shoreline
already has bulkheads or riprap, particularly
along the Patapsco River.658 The remaining
narrow muddy shores and mudflats, particularly
in the currently less developed sections of the
Patapsco, may be lost because of sea level rise if
shorelines are protected. In the upper portion of
the Back River north of Baltimore, small areas of
wetlands may be able to accrete sufficient
sediment to retain function, but migration will be
prevented by shoreline protection. Directly on
Chesapeake Bay, the large marshes at Edgemere
(North Point State Park, CBIM location 43) and
Hart-Miller Island may be lost to inundation if
the sea level rise rate increases by 2 mm per
year, and most will likely be lost with a 7 mm
per year increase. Hart-Miller Island, created
from dredge material and a haven for migrating
shorebirds, has extensive mudflats that will are
likely to be lost to sea level rise. During spring
and fall migrations, daily numbers of shorebirds
range from 1,000 to 10,000. The most numerous
shorebird species are sandpipers and plovers.
The mudflats are also used as a roost site for
significant numbers of migrating Caspian terns
{Sterna caspia). In 2004, small numbers of three
high conservation priority species nested and
bred on Hart-Miller Island: the coastal plain
subspecies of swamp sparrow (Melospiza
657Robbins andBlom, 1996, p. 122 (see note 552).
658Maryland Coastal Zone Management Program,
Department of Natural Resources, 2004, Development of
the Maryland Shoreline Inventory Methods and Guidelines
for Baltimore County and the City of Baltimore, prepared
by the Comprehensive Coastal Inventory Program, Center
for Coastal Resources Management, Virginia Institute of
Marine Science, College of William and Mary, Gloucester
Point, VA. NOAA Award No. 14-03-889 CZM049.
georgicma), listed by the Maryland Department
of Natural Resources as "In Need of
Conservation in Maryland," the spotted
sandpiper (Actitis maculciria), a rare species in
the state, and the willow flycatcher (Empidonax
traillii), an Audubon WatchList species.659 These
mudflat areas are all susceptible to inundation
from sea level rise. Low-elevation islands such
as Hart-Miller have limited habitat migration
options and will be dependent on accretion rates
(or additional dredged sediment inputs) for
maintenance of habitats. Loss of these islands
and mudflat areas would eliminate the nesting
and foraging opportunities currently provided for
the shorebirds.
Wrapup
The Western Shore will see a range of ecological
impacts from sea level rise in the future. Most
marsh areas near Chesapeake Bay are expected
to be marginal with midrange increase in the rate
of sea level rise (2 mm per year) and to be lost
with a high-range increase (7 mm per year). In
upper tributaries, sediment accretion is likely to
be sufficient to retain current area under a high-
range increase scenario. The extensive shoreline
armoring from northern Calvert County through
Baltimore City and County will limit shoreline
retreat, and eliminate sand and mudflats in front
of the protections. Loss of mudflats will
eliminate a key stopover for migratory birds (i.e.,
Hart-Miller Island). With tree death in high
marsh and higher water levels already visible in
the Patuxent River marshes, sea level rise may
induce changes in vegetation types even at
current rates and therefore impact the species
that rely on them, causing changes similar to
those expected in other Bay tributaries such as
the Pamunkey in Virginia. In contrast to these
potential losses, the protected portions of the
Calvert Cliffs will be allowed to continue
eroding inland, providing the habitat needed by
tiger beetles. Nevertheless, both larval and adult
forms of the beetles may suffer impacts of
reduced habitat caused by increased erosion and
subsequent loss of beach or cliff-face shearing.
659Audubon Important Bird Areas, Hart-Miller site profile,
accessed on May 5, 2006, at
http://iba.audubon.org/iba/view
SiteProfile.do?siteId=371&navSite=state.
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3.17 Upper Chesapeake Bay Shoreline
Author: Ann Shellenbarger Jones, Industrial Economics Inc.
Overview
The "Upper Bay" region encompasses Harford,
Cecil and Kent counties, from the Gunpowder
River to the Chester River. The region is
primarily rural, with several small cities
(Aberdeen, Havre de Grace, Perryville, and
Elkton) along the coast and tributaries.
This brief literature review discusses species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection. Existing literature and knowledge of
coastal scientists in the area appears to be
sufficient in many cases to make qualitative
statements about the possible impact if sea level
rise causes a total loss of habitat, which might be
expected if shores are protected with hard
structures and the wetlands are unable to keep
pace with sea level rise. Our ability is more
limited, however, to say what the impact might
be if only a portion of the habitat is lost. Overall
effects of sea level rise may include the
following:
• Most marsh areas will be retained through
accretion. On Eastern Neck, some areas are
being lost, but efforts are under way to
restore the shoreline using protected S.
alterniflora marshes. Upper Chesapeake Bay
will continue to provide spawning and
nursery habitat for crabs and fish, as well as
provide nesting and foraging habitat for
migratory and residential birds, including
bald eagles and large numbers of waterfowl.
• The cliff areas at Elk Neck State Park and the
Sassafras River NRMA will be left to erode
naturally. The cliff swallows and Puritan
tiger beetle (federally listed as threatened)
will continue to use the unique habitat. Cliff
areas surrounding Grove Point and the
Puritan tiger beetle population inhabiting
them may be impacted because without
nourishment shoreline stabilization may
result in loss of beach areas.
• Although some of the beaches may require
nourishment for retention, the general lack of
shoreline protections will minimize
interferences with longshore sediment
transport. Beaches are likely to remain intact
throughout much of the region.
The Susquehanna, located on the border between
Harford and Cecil counties, provides a large
(though variable) influx of sediment to upper
Chesapeake Bay, as well as almost half of
Chesapeake Bay's freshwater input.66" Much of
this sediment is retained above the mixing zone
(the estuarine turbidity maximum or ETM),
generally above the Chesapeake Bay Bridge.661
This sediment source provides material for
accretion in the tidal wetlands of the region. The
other upper Chesapeake Bay tributaries
characteristically have large sediment loads as
well, and currently receive sufficient sediment to
maintain wetlands and their ecological function.
Freshwater tidal wetlands are spread throughout
upper Chesapeake Bay, particularly in the upper
reaches of the tributaries. Key rivers in the areas
include the Susquehanna, the Elk, the Sassafras,
and the Chester. With the exception of the
Susquehanna, with headwaters in New York that
are not considered in this report, all of the rivers
66llBay Trends and Indicators, Chesapeake Bay Program,
accessed at: http://www.chesapeakebay.net/status/
statusdev. cfm? SID=201 &SUB JECTARE A=INDIC ATO
RS.
661 Chesapeake Bay Program, 2002, The Impact of
Susquehanna Sediments on the Chesapeake Bay, Scientific
and Technical Advisory Committee Workshop Report,
May 2000.
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[ SECTION 3.17 291 ]
in upper Chesapeake Bay have tidal wetlands at
their head. The high eroding cliffs characteristic
of Chesapeake Bay are also found in the region,
particularly at the mouths of the Susquehanna,
Elk, and Sassafras rivers. The remaining
shorelines are primarily a mix of narrow muddy
and sandy beaches and low vegetated banks.
Harford County
The Harford County shoreline is predominantly
marsh. Aberdeen Proving Ground (CBIM
location 44) is its defining feature, constituting
approximately a quarter of the county's area and
the majority of its Bay shoreline, from the
Gunpowder River north almost to the
Susquehanna River.662 The proving ground is
primarily within 5 meters of sea level and
contains a large concentration of tidal wetlands
(20,000 acres). The extent of shoreline
protections is uncertain given the military nature
of the site.663 Structural shoreline protections
throughout the proving ground shoreline would
eliminate the potential for wetland migration.
The wetlands may accrete sufficient sediment to
meet a 2 mm per year increase in sea level rise
rates, but a 7 mm per year increase would result
in loss of the tidal marshes and associated
ecological functions. In particular, the large bird
populations (bald eagles, great blue herons,
double-crested cormorants) that migrate through
and nest in these marshes would be affected.664 If
structural shoreline protections are minimal, a
combination of sediment accretion and inland
migration may occur, and wetlands function are
likely to be retained at approximately current
662A portion of the Aberdeen Proving Ground is located
within Baltimore County.
663,1 Aberdeen Proving Ground Pioneers Approach to
Wetland Mitigation," available at:
http://aec.anny.inil/usaec/publicaffairs/update/
win04/win0420.html. Although some protections are
required at the site under CERCLA actions to prevent
migration of contaminated sediments, the majority of the
shoreline is extensive wetlands. National Priorities List
Fact sheet for Aberdeen-Edgewood available at:
http ://www. epa. gov/reg3 hwmd/npl/MD2210020036. htm,
and
http://www.apg.anny.mil/apghome/sites/directorates/restor
/PDF_ Files/carrolis.pdf.
664Maryland DNR Bald Eagle Fact Sheet, accessed on May
23, 2006, at
http: //www. dnr. state. md.us/wildlife/baldeagle. html.
levels. The headwaters of the Bush River, inland
of the Proving Ground, are tidal and nontidal
wetlands. Large portions of the associated
shoreline are almost certain to be protected,
which will prevent migration of the wetlands.
Accretion in the upper parts of the tributaries
may be sufficient to meet an accelerated sea
level rise (high range estimate of 7 mm per year
above current rates). At the mouth of the
Susquehanna, the shoreline of Havre de Grace is
mostly developed and armored, with minimal
beach or marsh area.
Cecil County
Across the Susquehanna, in Cecil County, the
city of Perryville also has an armored shoreline.
Cecil County comprises minimal low-lying land,
with most areas above the 20-ft elevation. The
majority of the shoreline is not protected,
particularly along the Sassafras and Elk rivers,
and planners indicate that undeveloped areas are
unlikely to be protected in the future. Cliffs line
the mouth of the Elk River at Elk Neck State
Park (CBIM location 45); despite continuing
erosion, planners indicate shore protection is
unlikely.665 The headwaters of the Northeast and
Elk rivers are tidal freshwater wetlands, with
shore protection considered likely because of the
developments on adjacent land. Tidal flats in the
Northeast River's upper reaches and adjacent
wetlands become important fish spawning areas
in the spring.666 Accretion is expected to be
sufficient to meet an accelerated sea level rise
because of the large sediment inputs in the Upper
Bay, but significant armoring in the developed
headwaters could interfere with sediment
transport. If accretion rates are not sufficient,
wetland migration would be difficult in Cecil
County owing to the upland elevation adjacent to
the shorelines; consequently, loss of the large
tidal fresh marshes could occur. The marshes of
the upper reaches of the Elk River are a
spawning and nursery area for striped bass and a
nursery area for alewife (Alosapseudoharengus),
blueback herring (Alosa aestivalis), hickory shad
665Maryland Shoreline Changes Online, from the Maryland
Department of Natural Resources, Available at
http://shorelines.dnr.state.md.us/sc_online.asp.
666NOAA, 1994, Enviromnental Sensitivity Index Maps.
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[ 292 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
(Alosa mediocris), and white perch, as well as a
wintering and breeding area for waterfowl.667
Kent County
At the southern border of Cecil County is the
Sassafras River, shared with Kent County. Near
the mouth of the river are narrow sandy beaches,
backed by low bluffs to high cliffs. Because of
high sediment input and limited shoreline
armoring, beach loss caused by sea level rise is
likely to be minimal. Shore protection is unlikely
throughout most of the river. Portions of beach
and cliff habitat supporting a population of the
Puritan tiger beetle (federally listed as
threatened) at and around Grove Point, however,
may be stabilized resulting in loss of habitat.668
In contrast, on the southern shore, one section of
cliffs at the Sassafras Natural Resource
Management Area (Sassafras NRMA, CBIM
location 46) has a population of the Puritan tiger
beetle. For this reason, the cliffs in the Sassafras
NRMA are allowed to retreat naturally. On the
bay shore south of the Sassafras River, Kent
County has a higher energy shoreline, with
agricultural areas leading down to more
generally developed shorelines. Groins, jetties,
and bulkheads are all in use along portions of the
county's Chesapeake shoreline, but the majority
of the shoreline is unlikely to be protected.
Sandy and rocky shorelines predominate (e.g.,
Gratitude, Rock Hall) along with forested
riparian buffers. Tidal wetlands are rare along
the coast, except in sheltered coves. Shoreline
migration can readily occur in the unprotected
agricultural areas, minimizing ecological losses.
In the sheltered areas near Rock Hall, tidal
wetlands may be lost because of the almost
certain armoring along the developed areas. Loss
of wetlands diminishes habitat for the
crustaceans, mollusks, and other invertebrates
that feed on and provide nutrients for marsh
vegetation and the turtles (e.g., diamondback
667USFWS, 1980, Atlantic coast ecological inventory:
Wilmington, No. 39074-A1-EI-250, USFWS, Washington
D.C. As referenced for the Elk River in the Sealand
Limited Site description of NOAA trust resources,
available at:
http://response.restoration.noaa.gov/book_shelf/207_Seala
nd.pdf (Table 2).
668Barry Knisely (see note 647); USFWS, 1993 (see note
166).
terrapins) and birds (e.g., ducks, rails) that forage
on them. Spawning and nursery areas in marshes
for fish will be lost, as will nesting habitat for
marsh obligate birds.669
At the southern tip of Kent County is the Eastern
Neck National Wildlife Refuge (CBIM location
47). Currently, the greatest rates of erosion in the
county are found here, on the western shore of
the neck and the southeastern tip on the Chester
River.67" Because of its status as a national
wildlife refuge, some shoreline protections are
being introduced, with the goal of preserving
shoreline habitats for the many migratory and
residential birds as well as turtles, invertebrates,
and the Delmarva fox squirrel (Sciurus niger
cinereus), federally listed as endangered. In
many marsh locations, stands of Phragmites
australis are the only areas retaining sediment.671
Practices of removing invasive P. australis
stands and revegetating with native, noninvasive
species have been curtailed in some areas of the
refuge, in recognition of the desirable role that P.
australis plays in retaining soil.672 Higher levels
of substrate accumulation, both below ground
and above ground, have been documented in
stands of P. australis relative to Spartina spp.673
At Eastern Neck, local managers have observed
P. australis migrating upland into forested areas
as inundation at marsh edges increases, although
widespread marsh migration of other species has
not been observed.674
Thousands of waterfowl winter at Eastern Neck,
including Canada geese, tundra swans (Cygtrus
columbianus), and a variety of dabbling and
diving ducks, such as mallards, buffleheads
(Bucephala albeola), red-breasted and hooded
mergansers (Mergus serrator, and Lophodytes
cucullatus), scaup, and pintails.675 Migrating and
669Lippson and Lippson 2006, pp. 201-239 (see note 2).
67llMaryland Shoreline Changes Online (see note 665).
671 Written communication, Tom Eagle, Eastern Neck
National Wildlife Refuge, to Christina Bosch, Industrial
Economics. "Re: Sea level rise report wrap-up - please
respond" confirming text citing Tom Eagle in draft report,
including this sentence, sent September 11, 2006.
672Ibid.
673Roothand Stevenson, 2000, p. 173 (see note 45).
674Tom Eagle (see note 671).
675January 2005 waterfowl survey results for Eastern Neck
National Wildlife Refuge. Accessed online at
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[ SECTION 3.17 293 ]
residential birds are a primary component of the
Eastern Neck ecosystem. Bald eagles nest at
Eastern Neck, usually occupying five to seven
active nests at the forested riparian edge.676 Loss
of upland to open water will decrease eagle
habitat. Historically, Eastern Neck was a site for
black duck (Anas rubripes) nesting, along with
Smith Island, Barren Island, and other locations
in the lower Eastern Shore. However, the three-
square bulrush marshes (Scirpus americcmus) on
Eastern Neck have been largely inundated, as
have the black needle rush marshes (.Jimciis
roemerianus) on Smith Island and other
locations, a likely cause of reductions in black
duck counts.677 Loss of tidal marsh at Eastern
Neck will reduce suitable habitat for resident and
migratory shorebirds. The decreasing size of the
upland forested areas will also diminish critical
habitat for the Delmarva Peninsula fox squirrel,
which resides in forests adjacent to marsh.
Wrapup
Generally, sediment input to upper Chesapeake
Bay is expected to maintain shoreline areas at
current rates of sea level rise; marshes will be
marginal with a 2 mm per year increase in rates,
and lost with a 7 mm per year increase. The
Eastern Neck National Wildlife Refuge and the
Cecil County marshes in the Elk River are the
only areas identified in the Upper Bay as likely
to be negatively impacted because of sea level
rise. Eastern Neck has already lost marsh areas to
open water, and continued loss will limit habitat
for bald eagles, the Delmarva Peninsula fox
squirrel, and marsh birds. Armoring of the
shoreline for developments in Cecil County may
limit sediment transport and accretion to marsh
areas, thus limiting their extent and suitable
spawning habitat for some game fish.
http://www.fws.gov/ northeast/easternneck/ on 8 June
2006.
676Tom Eagle (see note 671).
677Ibid.
-------
3.18 The Chesapeake Bay Shoreline of the Central
Eastern Shore Author: Ann Shellenbarger Jones, Industrial Economics Inc.
Overview
The central eastern shore region covers the area
between the Chester and Choptank rivers. The
shore is jagged and sediment-poor, characterized
by multiple coves and inlets.678 On the northern
end of Kent Island and the Chester River,
marshes are expected to be marginal with an
increase of 2 mm per year in the rate of sea level
rise and to be lost with an increase of 7 mm per
year. South of Kent Island, tidal marshes are
marginally keeping pace with current rates of sea
level rise, and inundation is likely to occur with
an increase in sea level rise rate of 2 mm per year
(Section 2.1). Erosion is also a significant issue.
Planners expect that shorefront development,
particularly on Kent Island and in the Easton-St.
Michaels area, will lead to widespread shore
protection along Chesapeake Bay and the lower
tributaries.
This brief literature review discusses species that
could be at risk because of further habitat loss
resulting from sea level rise and shoreline
protection. Existing literature and knowledge of
coastal scientists in the area appear to be
sufficient in many cases to make qualitative
statements about the possible impact if sea level
rise causes a total loss of habitat, which might be
expected if shores are protected with hard
structures and the wetlands are unable to keep
pace with sea level rise. Our ability is more
limited, however, to say what the impact might
be if only a portion of the habitat is lost. The
overall environmental impact of sea level rise
seems likely to be the following:
• Large areas of marshes and tidal flats,
particularly near the mouth of the Chester
678Stevenson and Kearney, 1996 (see note 38).
and Choptank rivers and around the Eastern
Bay, will be lost. Crabs, juvenile fish, and the
larger fish and waterfowl that feed on them
will all be affected. The area lies in the
Atlantic Flyway, and will affect the ability of
migratory birds to feed on the route south in
the winter.
• Assuming that shores are protected with
structures rather than beach nourishment,
many of the remaining beaches will erode up
to the shore protection structure. This will
reduce the invertebrate population (e.g.,
mudsnails, tiger beetles, crabs) and therefore
stress shorebirds that prey on these species.
• Various marsh areas are likely to be retained.
The upper reaches of tributaries, including
the Chester and Choptank rivers as well as
areas with minimal shoreline protection and
low erosion, such as the Wye Island area, are
likely to retain current marshes. These areas
provide critical spawning and nursery habitat
for anadromous fish. Poplar Island will
provide a large, isolated marsh and tidal flat
area. These regions will continue to support
the fish, crustaceans, birds, and reptiles that
rely on them today.
Chester River and Kent Island
The Chester River forms the northern border of
Queen Anne's County. Planners expect that its
shores are unlikely to be protected from
Chestertown in the upper river down to
Queenstown. Accretion estimates indicate that
marshes along the river will be marginal with an
increase in sea level rise rates of 2 mm per year
(Section 2.1). Fringing tidal marshes are present
throughout this portion of the river, with minimal
large marshes. Migration may be possible, but in
-------
[ SECTION 3.18 295 ]
some areas inshore elevation quickly rises (e.g.,
elevation rises to 20 feet high within 500 feet of
the shoreline along Wilmer Neck) and will
impede migration. Birds that breed in the Chester
River marshes (e.g., Virginia rail, American
black duck) or breed near and feed in the
marshes (e.g., great blue and green herons,
osprey) will be negatively affected by the habitat
and prey loss.679 Along the river southeast of
Eastern Neck, near Queenstown, are large tidal
flats.68" Local planners view shore protection as
almost certain along the developed areas
between Queenstown and Kent Island, at the
mouth of the Chester River. Therefore, unless
sedimentation increases significantly, these tidal
flats are likely to be inundated if sea level rise
accelerates. The Chester River also provides
essential spawning habitat for king and Spanish
mackerel, cobia, and red drum, as well as forage
habitat for flounder and bluefish that feed in
marsh and shallow water areas near the mouth of
the river.681 Loss of tidal flats may result in a
decline in the resident invertebrates and fish that
use the shallow waters as well as the birds that
feed on the flats (e.g., great blue and green
herons).682
Kent Island is highly developed, with shore
protection almost certain along the Chesapeake
Bay side (CBIM location 48). Historically, the
shore along Chesapeake Bay had mostly narrow
sandy beaches with some pebbles along low
bluffs, with some wider beaches with small
dunes. Terrapin Park, north of the Bay Bridge,
still has an extensive dune system. The privately
owned shores, however, are gradually being
replaced with stone revetments. The beaches will
be unable to migrate inland, leading to habitat
loss for the various resident invertebrates,
including tiger beetles, sand fleas, and numerous
crab species. Shorebirds that rely on beaches for
forage and nesting will face more limited
679Robbins andBlom, 1996, pp. 76-77, 92-93, 128-129
(see note 552).
68llTiner and Burke, 1995 (see note 32).
681NOAA's Guide to Essential Fish Habitat Designations in
the Northeastern United States, Summary of Essential Fish
Habitat for the Chester River, accessed on July 20, 2006, at
http ://w ww. nero. noaa. gov/hcd/md2. html.
682Author's analysis based on Robbins and Blom, 1996, pp.
50 and 63 (see note 552).
resources.683 The Eastern Bay side, by contrast,
has several tidal creeks, extensive tidal flats, and
wetlands. Planners expect that only two-thirds of
the these shores are likely or certain to be
protected, because Maryland's Critical Areas Act
will prevent intense development along one-third
of the shore. Given the low accretion rates, the
current marshes and tidal flats in these areas are
likely to be lost, although some marsh may
convert to tidal flat. Extensive SAV beds once
grew in the nearshore areas of Eastern Bay, but
little remains except in Crab Alley Bay (CBIM
location 49), where shore protection is likely or
almost certain.684 Increasing water depths are
likely to reduce—and eventually eliminate—the
existing SAV (largely a mix of Ruppia maritima
and Zcmnichelliapalustris)', a landward
migration onto existing flats and marshes will
depend on sediment type and choice of shoreline
structure (see discussion of SAV in Section 3.1).
The loss of tidal wetlands and probable loss of
SAV would cause losses to fish and birds as
discussed above for the Chester River.
Additionally, large shellfish beds in Eastern Bay
may be affected by the habitat changes, with
uncertain consequences.
Talbot County/Wye River
East of Kent Island across Eastern Bay is the
Wye River, Wye East River, and Wye Narrows.
In the Wye River, recreationally important fish
include striped and largemouth bass, several
catfish and perch species, blue gill, and black
crappie. Many smaller fish inhabit the marshes
and SAV, including mummichog, striped
killifish, menhaden, bay anchovy, hogchoker,
and Atlantic silverside. The Wye River also
produces an abundant blue crab harvest, as well
as oysters and soft-shell clams.685 The Wye East
River and Wye Narrows contain extensive
683Lippson and Lippson 2006, pp. 26-42 (see note 2).
6840rth, R. J., D. J. Wilcox, L. S. Nagey, A. L. Owens, J.
R. Whiting, and A. K. Kenne, 2005, 2004 Distribution of
Submerged Aquatic Vegetation in the Chesapeake Bay and
Coastal Bays, VIMS Special Scientific Report No. 146,
Final report to U.S. EPA, Chesapeake Bay Program,
Annapolis, MD, Grant No.CB973013-01-0, available at:
http ://www. vims. edu/bio/sav/sav04.
685Wye Island NRMA Land Unit Plan, 2004, Prepared by
the Maryland DNR Land and Water Conservation Service,
p. 19.
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[ 296 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
freshwater marsh. Planners view shore protection
as unlikely along the eastern side of the Wye
River and in the Wye Narrows, but almost
certain along the western side (e.g., the Bennett
Point region) and likely along parts of the Wye
East River. If the marshes and tidal flats in these
areas are lost, the juvenile fish nurseries will be
lost and species that feed in the marshes and
SAV (e.g., wading birds, striped bass, blue gill,
blue crabs) will lose an important food source.
Farther upstream on the Wye East River is the
Wye Island Natural Resource Management Area
(Wye Island NRMA, CBIM location 50). Steep
vegetated banks, 1 to 20 feet in height with some
areas eroded to bluffs, are the primary border
around the island, with some areas of estuarine
marsh forming more gradual slopes to upland
areas.686 The marshes of Wye Island support a
large waterfowl population, with a wintering
waterfowl count of 20,000 birds such as mallard,
canvasback, and ruddy ducks and Canada
geese.687 Local planners indicate that adjacent
areas are unlikely to be protected, with the
exception of the area south of Wye Island.
Current erosion rates in the area are low
(approximately 2 feet per year); however,
accretion rates are also low and migration is
impeded in areas by the upland height and by
dense vegetation, which shades the shorelines
and inhibits growth of emergent vegetation.688
Nonstructural and hybrid shoreline protections
have been implemented at the Wye Island
NRMA site to protect the various habitats.689
Maryland DNR will manage Wye Island to
protect its biological diversity and structural
integrity, such that detrimental effects from sea
level rise acceleration are minimized.69"
Ibid., p. 13.
687Ibid., p. 18.
688Ibid„ pp. 33-34.
689Burke, D., E.W. Koch, and J.C. Stevenson, 2005,
Assessment of Hybrid Type Shore Erosion Control
Projects in Maryland's Chesapeake Bay, Phases I and II,
Final Report submitted to the Chesapeake Bay Trust,
Annapolis, MD, p. 9, and further discussions throughout
document.
69llWye Island, 2004, p. 12 (see note 685).
Easton-St. Michaels-Tilghman Island
Planners expect continued development and
shore protection in the general area of Easton
and St. Michaels, including both sides of the
Miles and Tred Avon rivers and most of the land
in between. On the bay side of Tilghman Island
(CBIM location 51), the high erosion rates will
tend to encourage construction of shoreline
protection measures, particularly following
construction of waterfront homes.691 Walnut
Point (CBIM location 53), at the southern end of
Tilghman Island, has been riprapped and
bulkheaded multiple times after continuing
losses of protective measures from storms and
high-energy waves. The multiple waterways
(e.g., Harris Creek, Broad Creek, Avon River)
east of Tilghman Island that flow into the
Choptank are also all highly developed. The bay
side of Tilghman Island has fringing marsh,
nearshore SAV beds, and beaches. On the east
side of Tilghman Island, marshes and tidal flats
are found extensively along the multiple
waterways particularly on the eastern edge of
Harris Creek and the borders of Broad Creek.692
Sea level rise will eliminate most of these marsh
and shallow water areas owing to the inability to
migrate and their marginal ability to migrate with
current sea level rise rates. The loss of beaches
and shallow water habitat will eliminate the
worms, snails, amphipods, sand fleas, and other
invertebrates that live in the beach and intertidal
areas and reduce forage for their predators (e.g.,
oystercatchers, sandpipers, plovers, and glossy
ibises). Shallow water habitats, with their
resident community of bivalves, worms and
other invertebrates, provide a high-density
feeding ground for many predators, including
fish and wading birds. Loss of shallow water
habitat will decrease the SAV that is distributed
throughout the coves. Today the SAV provides
habitat for many fish as well as forage for
waterfowl. Extensive soft-shell clam (Mya
arenaria) beds are also found in shallow water
west of Tilghman Island opposite areas almost
certain to be protected.693 The impact of the
691 Maryland Shoreline Changes Online (see note 665).
692Tiner and Burke, 1995 (see note 32).
693NOAA, 1993, Enviromnental Sensitivity Index
summary maps for Chesapeake Bay, obtained from the
NOAA Office of Response and Restoration.
-------
[ SECTION 3.18 297 ]
armoring and sea level rise on these beds is
unknown.
West of Tilghman Island, Poplar Island (CBIM
location 52) eroded from more than 1,000 acres
during the mid-19th century to less than 10 acres
today. It is now being restored to the footprint of
1847 through the beneficial use of dredge
material, which is creating shallow water, low
marsh, high marsh, and vegetated upland
areas.694 During the creation process, the island
has attracted a variety of wildlife, including great
blue herons, double-breasted cormorants, and
diamondback terrapins.695'696 The final upland
elevations will be 20 feet above mean lower low
water, more than high enough to retain its
functions as sea level rises for the foreseeable
future.
Wrapup
Large areas of marshes and tidal flats,
particularly near the mouth of the Choptank
River and around the Eastern Bay, are likely to
be lost. These marshes are only marginally
meeting current rates of sea level rise, and are
predicted to be lost with a 2 mm/yr increase in
rate. Crabs, juvenile fish, and the larger fish and
waterfowl that feed on them will all be affected.
The central eastern shore lies in the Atlantic
Flyway and marsh loss will affect the ability of
migratory birds to feed on the route south in the
winter. Although the northern side of Kent Island
and the marshes on the Chester River are
keeping pace today, they are expected to be
marginal with a 2 mm/yr increase in sea level
rise and to be lost with a 7 mm/yr increase.
Armoring of developed areas on Kent Island and
south to Queenstown is likely to cause
inundation of tidal flats and some marsh areas up
to the protection structures.
694Poplar Island Environmental Restoration Site, U.S.
Army Corps of Engineers, accessed on July 17, 2006, at:
http: //www. nab .usace. army. mil/proj ects/Mary land/Poplarl
sland/index.html.
695Ibid.
696Robbins and Blom, 1996, double-crested cormorants.
pp. 44—45 (see note 552).
-------
3.19 Virginia Eastern Shore of Chesapeake Bay
Author: Elizabeth M. Strange, Stratus Consulting Inc.
Species and habitats of the Virginia Eastern
Shore along Chesapeake Bay are potentially at
risk because of sea level rise. This study region
includes the bay side of Northampton and
Accomack counties. Shorelines of the region
contain important habitats for a variety of
species, and a great deal is known about their
ecology and habitat needs. Based on existing
literature and the knowledge of local scientists,
this brief literature review discusses those
species that could be at risk because of further
habitat loss resulting from sea level rise and
shoreline protection (see Map 3.8). Although it is
possible to make qualitative statements about the
ecological implications if sea level rise causes a
total loss of habitat, our ability to say what the
impact might be if only a portion of the habitat is
lost is more limited. A total loss of wetland
habitat could occur if shores are protected with
hard structures and the wetlands are unable to
keep pace with sea level rise.
Northampton and Accomack counties have the
greatest area of wetlands and dry land in Virginia
that are vulnerable to sea level rise, estimated at
47,863 ha (184.8 mi2) and 53,923.6 ha (208.2
mi2) for Northampton and Accomack counties,
respectively. Because most of the land in the two
counties is undeveloped or agricultural land, they
also have the greatest potential for wetland
creation than other Virginia shorelines.
Bay Side of Northampton County
The bay side of Northampton County is
characterized by relatively high lands, including
substantial cliffs near the mouth of the bay. This
shoreline has some small areas of salt marsh
within coves, but is most notable for its
beach/dune systems, including some wide sandy
beaches near the Town of Cape Charles.697
697Varnell, L.M., and C.S. Hardaway Jr., 2005, "A risk
assessment approach to management of estuarine dunefields,"
Ocean & Coastal Management 48:767-781.
Estuarine beach/dune systems occur in areas of
stability and sand accretion, such as the mouths
of tidal creeks, embayments, in front of older
dune features such as washovers or spits, and
against structures like jetties and groins. An
estimated 16.42 km (10.2 miles) of dune shore
occur along the bay side of Northampton
County, mostly fronting headlands.698
Shore protection is likely along most of
Northampton's bay side shoreline, with the
exception of the heads of some tidal creeks.
Shore protection often is required on upland
banks and interfluves experiencing erosion.699
Regardless of any shoreline hardening, the high
upland elevation of this area would make marsh
migration difficult. The lack of lowlands, with
the exception of the shoreline near the Town of
Cape Charles, means that the primary impact of
sea level rise on these shorelines will be erosion.
Beach nourishment to protect public beaches is
likely, and recently the Board on Conservation
and Development of Public Beaches provided
$300,000 for a breakwater and beach
nourishment project in the Town of Cape
Charles. The dunes themselves are important for
erosion control of adjoining lands, and therefore
the Commonwealth of Virginia seeks to preserve
them under the Coastal Primary Sand Dune
Protection Act of 1980.7U"
698Hardaway, C.S., Jr., D.A. Milligan, L.M. Varnell, G.R.
Thomas, W.I. Priest, L.M. Menghini, T.A. Barnard, and C.
Wilcox, 2004, Northampton County Dime Inventory, Technical
Report, Virginia Institute of Marine Science, College of William
& Mary, Gloucester Point, VA, p. 5.
099 Lyle Varnell and Scott Hardaway, Virginia Institute of Marine
Sciences, written communication, 2/15/07.
7"uMilligan, D.W., C.S. Hardaway, Jr., G.R. Thomas, L.M.
Varnell, T. Barnard, W. Reay, T.R. Comer, and C ,A. Wilcox,
2005, Chesapeake Bay Dune Systems: Monitoring, Technical
Report, Virginia Institute of Marine Science, College of William
& Mary, Gloucester Point, VA.
701
Varnell and Hardaway, 2005, p. 768 (see note 697).
-------
[ SECTION 3.19 299 ]
The beaches and maritime forests on the bay side
of Northampton County provide habitat for a
variety of species, most notably neotropical
songbirds and the federally listed threatened
northeastern beach tiger beetle.7"1 Evidence for
the presence of these species comes from surveys
in area nature preserves. The Cape Charles
Coastal Habitat Natural Area Preserve (Cape
Charles Preserve)7"2 and the Savage Neck Dunes
Natural Area Preserve (Savage Neck Preserve)7"3
both provide what preserve staff consider
"outstanding" beach/dune and maritime forest
habitat for migratory songbirds. Tiger beetles are
also found on the beaches of both preserves, as
well as the William B. Trower Bayshore Natural
Area Preserve.7"4
Bay Side of Accomack County
The bay side of rural Accomack County is
primarily tidal salt marsh, with low-lying lands
(less than 2 feet above the wetlands) extending
several miles inland. The county as a whole
contains nearly a fifth of the state's dry land
within 2 feet of mean high water (MHW), and
therefore these marshes are among the most
vulnerable in the state.
Local planners expect that most of the bay side
shoreline of Accomack County will remain
unprotected, with the exception of Onancock
Creek, the town of Saxis and the Saxis Wildlife
Management Area near the Maryland border, and
part of the southern shore of Pungoteague Creek.
These unprotected marshes are already migrating
inland in response to sea level rise, creating new
wetlands in agricultural areas at a rate of 16.2 ha
(40 acres) per year (see Section 2.1). Given the
anticipated lack of shoreline protection, and the
'""Virginia Department of Conservation and Recreation, Cape
Charles Coastal Habitat Natural Area Preserve Fact Sheet.
Accessed December 5, 2007 at:
http://www.dcr.virginia.gov/natural heritage/natural area preser
ves/capecharles. shtml.
703Virginia Department of Conservation and Recreation, Savage
Neck Dunes Natural Area Preserve Fact Sheet. Accessed
December 5, 2007 at:
http://www.dcr.virginia.gov/natural heritage/natural area preser
ves/savage.shtml.
704Virginia Department of Conservation and Recreation, William
B. Trower Bayshore Natural Area Preserve Fact Sheet. Accessed
December 5, 2007 at:
http://www.dcr.virginia.gov/natural heritage/natural area preser
ves/wmtrower. shtml.
marginal likelihood of sufficient sediment input
to meet an acceleration in sea level rise of more
than 2 mm/yr, the seaward boundaries of these
tidal wetlands are likely to continue retreating.
The upland elevations are higher in southern than
northern Accomack County, which will make
migration more difficult. Marshes in the
Hackensack area in northern Accomack County
cannot keep pace even with the current rate of
sea level rise (Section 2.1). The likelihood of
armoring along the inland portions of the tidal
creeks south of Onancock could also lead to
greater relative wetlands loss along this shoreline
compared to the northern part of the county.
The salt marshes of Accomack County support a
variety of species, including rare bird species
such as the seaside and sharp-tailed sparrow.
According to a fact sheet by the State of
Virginia, Parkers Marsh Natural Area Preserve in
Accomack County provides excellent habitat for
sharp-tailed sparrow and Peregrine falcon.7"5
Growth and survival of these species could be
reduced where shores are hardened, unless
alternative suitable habitat is available nearby.
A study in the Eastern Shore indicated that bird
communities in large marshes cannot persist in
habitat patches of less than 5 ha (12.4 acres)7"6
Declines in birds where marsh loss is substantial
could have a dramatic effect on local estuarine
food webs. Dr. Michael Erwin of the Patuxent
Wildlife Research Center has noted that
waterbirds and shorebirds are top-level
consumers in marshes and an important link in
energy and nutrient transport among nearshore,
marsh, and upland habitats as well as the
surrounding estuary.7"7 Loss of these birds could
remove a significant amount of biomass from
nearshore habitats (e.g., the total biomass of just
7"5Virginia Department of Conservation and Recreation, Parkers
Marsh Natural Area Preserve Fact Sheet. Accessed December 5,
2007 at:
http://www.dcr.virginia.gov/natural heritage/natural area preser
ves/parkers. shtml.
7u6Watts, 1993, p. 35 (see note 61).
707Erwin, 1996, p. 214 (see note 240).
-------
[ 300 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
one species of wintering waterfowl exceeded
50,000 kg).708
Although gradual inundation in the near term
could increase tidal creeks and channels, making
the marsh surface more accessible for nekton
(i.e., free-swimming finfish and decapod
crustaceans such as shrimps and crabs), as tidal
flooding increases and the accessible area
declines, a decrease in nekton production could
occur. For example, Weisburg and Lotrich
demonstrated experimentally that growth rates of
mummichogs can decrease significantly when
they have no access to tidal marsh.7"9 As marsh
habitats drown, populations of immobile species
that cannot survive when permanently inundated
could be lost. Mobile species will need to find
other suitable habitats, but if these alternative
sites provide lower quality habitat, the growth
and survival of these populations could decline.
Accomack County lacks the dune/beach
shorelines found on the bay side of Northampton
County. Nonetheless, the small patches of beach
that do occur provide important species habitat.
For example, the rare tiger beetle is found in
sandy beach habitat in the Parker's Marsh
Natural Area Preserve.71"
There are four major island complexes on the
bay side of Accomack County, including
Tangier, Smith, Great Fox, and Watts islands.
These islands provide nearly predator-free
nesting for numerous island-nesting bird species.
Erosion and flooding on these islands due to sea
level rise could reduce critical habitat and the
local populations of these species.711
709Weisburg, S.B., and V.A. Lotrich, 1982, "The importance of
an infrequently flooded intertidal marsh surface as an energy
source for the mummichog Fundulus heteroclitus: An
experimental approach," Marine Biology' 66:307-310.
710Virginia Department of Conservation and Recreation, Parkers
Marsh Natural Area Preserve Fact Sheet. Accessed December 5,
2007 at: http://www.state.va.us/dcr/dnh/parkers.htm.
711Watts, 2006, p. 32 (see note 495).
-------
3.20 Sea Level Rise Modeling Study
Authors: Russell Jones, Stratus Consulting Inc., Elizabeth M. Strange, Stratus Consulting Inc.
Introduction
Over the past century, the rate of sea level rise
has increased more than twice the average
historical rate.712 The U.S. EPA estimates that by
2100, sea level will increase nearly 2 feet in
many coastal areas of the United States, with half
of this increase directly attributable to global
warming.713 714 Rising sea level, often associated
with land subsidence, coupled with human
habitation of the shore zone and shoreline
armoring with seawalls and similar structures,
places shoreline property and coastal habitats
and biota at risk.715"716"717
As the sea rises, beaches are eroded and tidal
wetlands are gradually converted to open water.
Seawalls and other armoring structures are often
used to protect shoreline property. However,
such structures also prevent the landward
migration of wetlands that would otherwise
follow sea level rise. In addition, waves scour
away sand seaward of armoring structures,
preventing natural replenishment of sand. The
combination of increased sea level rise and
shoreline armoring can result in the loss of
wetlands, beaches, and other nearshore areas that
712Huybrechts et al., 2001 (see note 1).
713Barth, M.C. and J.G. Titus, 1984, Greenhouse Effect
and Sea Level Rise: A Challenge for This Generation, Van
Nostrand Reinhold, New York.
714Titus and Narayanan, 1995 (see note 3).
715Titus, J.G., R.A. Park, S.P. Leathennan, J.R. Weggel,
M.S. Greene, P.W. Mausel, S. Brown, G. Gaunt, M.
Trehan, and G. Yohe, 1991, "Greenhouse effect and sea
level rise: The cost of holding back the sea," Coastal
Management 19:171-204.
716Douglas, B„ M. Kearney, and S. Leathennan (eds.),
2001, Sea Level Rise: History and Consequences,
Academic Press, San Francisco, CA.
717Wu, S-Y., B. Yarnal, and A. Fisher, 2002,
"Vulnerability of coastal communities to sea-level rise: A
case study of Cape May County, New Jersey," Climate
Research 22:255-270.
are highly valued by humans and are necessary
for the survival of fish, birds, and wildlife.
Unfortunately, potential impacts on shoreline
property are often the sole focus of strategies for
responding to anticipated sea level rise.
However, planning must also consider responses
that will protect natural ecological processes and
coastal resources. Otherwise, there may be
substantial and irreversible losses of coastal
habitats and biota with unintended ecological
and economic consequences.
We conducted a pilot study of coastal Ocean
County, New Jersey, in which we developed and
applied methods for evaluating risks to coastal
ecosystems under alternative sea level rise and
armoring scenarios. The study is one of the first
attempts to quantify not just habitat changes but
also changes in biota in response to sea level
rise.718
The analysis focused on impacts to tidal
marshes, SAV, sandy beaches, and open water.
Maintaining tidal marshes in response to sea
level rise depends on the availability of adjacent
low gradient uplands to allow landward
development of coastal marshes. As sea level
rises, armoring structures will preclude the
718The technical work that forms the basis for this report was
funded by EPA's Office of Atmospheric Programs under Contract
No. 68-W02-027. The report itself was prepared by Stratus
Consulting with corporate development funds. James G. Titus,
the EPA work assignment manager, developed the sea level rise
and armoring scenarios that were evaluated as well as the habitat-
elevation relationships used in the inundation model. Dr. Michael
P. Weinstein of the New Jersey Marine Sciences Consortium,
Sandy Hook Field Station provided valuable assistance with the
analysis of effects on fish production of changes in marsh habitat.
Dr. Michael Kearney of the University of Maryland developed
accretion rates. ICF Consulting Inc. provided elevation data, and
Industrial Economics developed the armoring scenarios in
consultation with local planners. The conclusions presented in
this report are those of the authors and do not represent the
opinions of subcontractors or the official position of the EPA.
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[ 302 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
inland movement of most tidal wetlands, and
will influence the exchange of nutrients, other
allochthonous materials, and organisms from
watersheds to estuaries.
Most critically, without the ability of intertidal
habitats to migrate or accrete sediments seaward
of a structure at an accelerated rate, they will
ultimately "drown" and be eliminated as sea
level rise inundates the shoreline seaward of the
armored structures.
This study considered potential impacts of sea
level rise and shoreline armoring on:
• finfish and shrimp with varying dependency
on SAV and Spartina marshes; and
• birds that depend on coastal habitats for
feeding, resting, or nesting.
The following key questions were addressed:
• What habitat changes are likely to occur?
• What species are associated with these
vulnerable habitats?
• To what extent can habitat and species
changes be quantified?
We first present an overview of the study area
and the habitats and species evaluated. Next we
describe the inundation model developed to
evaluate habitat changes under various sea level
rise and armoring scenarios and defines the
scenarios that were evaluated. We present
methods used to evaluate potential changes in
biota in response to predicted habitat changes,
and then discuss results of the analysis and
directions for future research. The appendix
presents GIS maps of modeled habitat changes.
Study Habitats and Biota
Study Area
The study area included all of coastal Ocean
County, New Jersey, including Barnegat Bay,
inland to the boundary of the zone defined by
New Jersey's Coastal Areas Facilities Review
Act (CAFRA) (Plate 1 in the appendix). The
CAFRA zone includes the area considered by
CAFRA to be vulnerable to sea level rise.
The study area includes a system of barrier
beaches, tidal wetlands, and productive, shallow,
backwater lagoons that are important for
estuarine fish and shellfish, migratory and
wintering waterfowl, migratory shorebirds,
colonial nesting waterbirds, migratory passerines
and raptors, and resident terrapin sea turtles.719
Important habitats include barrier beach and
dune, open water, SAV, intertidal sand and
mudflats, salt marsh islands, and fringing tidal
salt marshes. While recognizing the importance
of all of these habitats, this study examined
potential changes only in the areal extent of tidal
marshes, SAV, sandy beaches, and open water.
Habitat Classification Scheme
Based on review of a number of habitat
classification schemes amenable to analysis
using a geographic information system (GIS), we
selected a classification scheme that was
developed by the Grant F. Walton Center for
Remote Sensing and Spatial Analysis (CRSSA)
at Rutgers University. We selected this scheme
because it links well with National Wetlands
Inventory (NWI) data72" and has many classes
that coincide well with other classification
schemes. It also incorporates some finer scale
data that were developed for use in a study of
habitat loss and alteration in the Barnegat Bay
watershed (Figure 3.1).721
Submerged aquatic vegetation. The SAV of
Barnegat Bay is dominated by eelgrass (Zoster a
USFWS, 1997 (see note 172).
72uCowardin, L.M., V. Carter, F.C. Golet, and E.T.
LaRoe, 1979, Classification of Wetlands and Deepwater
Habitats of the United States, FWS/OBS-79/31.
USFWS, Washington, DC.
721CRSSA, 2000, Rutgers University, 20000731, New
Jersey 1995, Level III Land Cover Classification.
Digital GIS data. Center for Remote Sensing and
Spatial Analysis.
-------
[ SECTION 3.20 303 ]
8ARNEGAT BAY CIS DATA
BURUNGTON
COUNTY
Habitats of the Barnegat Bay Watershed
Developed Highly
|HI Davabped MotteraSey
- LflJiWy Wooded
Developed - Urwooded
Cufcvated - Tilted.' file#
~ CdfcviWsd • V inftjy' BjtiiKfi
| J Grassland - UnmanagBd
Grassland - Inlsnsvely Managed
tirastland - A«port
H Ff'RSl - Oaft Oocnmani
~ Fores! - Oak' Prw
¦I Forest - Pra' Oak
m f oiftst ¦ Pra Dominant
1 Strufe/Shrub - Maed D&wftwusj' CorSerowt
Bars Land
M.yinpjts^iarrs Opftfi Water > 3m Dfipri
H Opwi Water < 3m Depth
Ma-ineEstjar re Submerged Aquatic Vegetalbn Bedt
Ma'ineEsiiarra Ir'aniial flats
MiViftpjtstjarp* Trial C«efci/ EmhaymftntR
=j MannejEs&ianrnii SubtdaJ Poods
Marina Esliar ra D'BcfeBd Lagoons
M.vinfti'E&tiarnA UftMntQlriarftd Sho/ft Sand
H Ma-mRiFstiaisr* ll.i-ontnldalftd She*-* Wiri
B Spalina Warm: Spartira allernrfbra dominant
¦¦ Spalina Mars.'!: Spamra paten?. dcTinar"
H Phraflnr.to. M.vr.h Phragmilfts aj£tr,*:is dominant
B Brackish Tidal/Fresh Tidal Marsh Mixed Specks
RrvBr,'LacustrinB*PatjUrine Open Water
^ ftiver/lacwitrine/Pakitsrtne Unconukdaled Shorn
¦ RimtacuSfriflfrPafcitfrifiG Em#a«n| Marsh MimkJ Spec**
¦ Rrver'lacusErina«PaJjarinB Emergen I Marsh Phragmites austrats dominant
Haidwood De&Aious Swamp
!¦ Prtcti Pine: Lowland
Mix«d Hardwood - Pins - Gedai - Hioly
Whte Cedar Swamp
Ml Mixfiri Deeduojj. twrfflrous ScrutvSlvrub
¦ Mixed Deciduous Coniferous StfutuSlwub Ounet
Foriut: if>rr/Info GRID Data
X-tir«: bbhnbit.ir •»
Sa-urr!#; CRSSA
The Barnegat Bay habitat map data were developed at CRSSA through Hie interpretation
and analysis of a variety of sources including Undsat Thematic Mapper satellite imagery,
aerial photography, land use / land cover and statdnational wetland digital data, The benthie
aquatic and upland'wateihed habitat map* were combined to create one seamless habitat map
for the entire Barnegat Bay ecosystem. This GIS data set is downloadable and is also featured
on CRSSA's Barnegat Bay world wide web site under "Habitat Tours". c RSSA,04/2000
Figure 3.1. Habitats of the Barnegat Bay Watershed. Source: Grant F. Walton Center for Remote
Sensing and Spatial Analysis, Rutgers University.
marina), occurring in dense beds at water depths
of 1 meter or less. SAV beds provide spawning
and nursery areas for epibenthic fishes such as
fourspine stickleback (Apeltes quadracus), naked
goby (Gobiosoma bosci), northern pipefish
(,Syngnathus fuse us), and rainwater killifish
(Lncania parva), and refuge for decapod
crustaceans such as blue crab (Callinectes
sapidus), grass shrimp (.Hippolyte
pleuracanthus), and sand shrimp (Crangon
septemspinosa).723
SAV beds are also important feeding grounds for
waterfowl. Midwinter aerial waterfowl counts in
Barnegat Bay average 50,000 birds, mostly brant
(Branta bernicla), American black duck {Anas
'~USFWS, 1997 (see note 172).
Sogarcl and Able, 1991 (see note 94).
rubripes), scaup (Aythya spp.), mallard {Anas
platyrhynchos), bufflehead (Bueephala albeola),
Canada goose {Branta danadensis), and
mergansers {Mergus spp.).724
Tidal marshes. Marsh vegetation type is largely
controlled by salinity and tidal regime (BBNEP,
2001). Low marsh, which is regularly inundated
by the tide, is dominated by smooth cordgrass
{Spartina alterniflora). Low marsh occurs in
intertidal areas, especially along tidal creeks and
channels,725
The high marsh, which is only irregularly
flooded by saline waters, is dominated by salt
meadow cordgrass (S. patens). The extensive salt
USFWS, 1997 (see note 172).
725T, ,
-------
[ 304 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
marshes along the mainland shoreline and salt
marsh islands of Barnegat Bay are mostly high
marsh.726
The invasive common reed (Phragmites
australis) occurs in a narrow fringe along the
upland edge of marshes where salinities are low
because of less tidal flooding and greater
freshwater runoff727
Extensive networks of creeks ranging from small
tidal rivulets to major subtidal tributaries occur
throughout the Spartina marshes of New
Jersey.728 Marsh creeks support significantly
higher densities of finfish than do SAV beds,
whereas densities of decapod crustaceans such as
blue crab tend to be higher in SAV.729 The fish
fauna of marsh creeks is dominated by small
schooling species such as Atlantic silverside
(.Menidia menidia), mummichog (Fundi/his
heteroclitus), and bay anchovy (Anchoa
mitchilli).
S. altemiflora marsh provides habitat for
songbirds such as seaside sparrow
(Ammodramus maritimus) and long-billed marsh
wren (Telmatodytes palustris), and S. patens
marsh provides habitat for sharp-tailed sparrow
(A. caudacutus) and red-winged blackbird
(Age lain s phoeniceus).730
Phragmites marshes support significantly fewer
larval and small juvenile fish731 and
macroinvertebrates732 than do Spartina marshes.
Spartina marshes appear to have more standing
water on the marsh surface and a more complex
728Sogard and Able, 1991 (see note 94).
729Ibid.; Rountree and Able, 1992 (see note 22).
7i"BBNEP. 2001, The Barnegat Bay Estuary Program
Characterization Report, available from the Barnegat
Bay National Estuary Program at:
http: //www. bbep. org/char_rep. htm.
7,1 Able. K.W. and S.M. Hagan, 2000, "Effects of
common reed (Phragmites australis) invasion on marsh
surface macrofauna: Response of fishes and decapod
crustaceans," Estuaries 23:633-646.
7l2Angradi. T.R., S.M. Hagan, and K.W. Able, 2004,
"Vegetation type and the intertidal macroinvertebrate
fauna of a brackish marsh: Phragmites vs. Spartina,"
Wetlands 21:75-92.
topography than do the generally drier and flatter
Phragmites marshes.733
Sandy beaches. Beach nesting birds include
black skimmer (Rynchops niger) and least tern
(Sterna antillarum), both of which are state-
listed endangered species, and piping plover
(Charadrius melodus), a federally listed
threatened species. According to surveys by the
USFWS,734 Holgate Beach within Barnegat Bay
supported an average of 13 nesting pairs of
piping plover from 1985 to 1995 and 1,500 black
skimmers in 1993. In 1995, 570 nesting black
skimmers were counted in Barnegat Bay.
Holgate Beach and Barnegat Inlet had 400 and
307 adult least tern, respectively.
Beaches are also important spawning habitat for
horseshoe crabs (Linnduspolyphemus).735
Horseshoe crab eggs are an important component
of the diet for migratory shorebirds that use
beaches as a feeding area.
Inundation Model
Model Algorithms
To predict habitat changes under various sea
level rise and armoring scenarios, Stratus
Consulting developed a GIS-based inundation
model. The inundation model includes three
integrated algorithms written in Arc Macro
Language (AML) and run in the GRID module
of Arclnfo software (v. 8.3).
The main algorithm predicts how current tidal
wetland habitats (S. altemiflora, S. patens, and
Phragmites) will change on an annual basis over
200 years based on the relationship of the habitat
to the spring tide range and on estimated
elevation changes relative to mean tide level
(MTL) resulting from net sea level rise. Based on
the available literature, net sea level rise is
defined as the historical sea level rise rate plus
the accelerated rate due to global warming minus
7j3Able and Hagan, 2000 (see note 731).
734USFWS, 1997 (see note 172).
7j5Smith, D.R., P.S. Pooler, B.L. Swan, S.F. Michels,
W.R. Hall, P.J. Minchak, and M.J. Millard, 2002,
"Spatial and temporal distribution of horseshoe crab
(Limuluspolyphemus) spawning in Delaware Bay:
Implications for monitoring," Estuaries 25:115-125.
-------
[ SECTION 3.20 305 ]
the estimated accretion rate for each type of tidal
wetland,736 calculated annually over the 200 year
time period.
Accretion rate estimates were developed for the
project by Dr. Michael Kearney of the University
of Maryland. He considered data from the
literature and his own studies on vertical
accretion rates in barrier lagoonal marshes with a
similar tidal and physiographic setting. Accretion
rates for S. altemiflora in the Virginia Barrier
Islands determined by Pb-210 dating were about
2 mm/yr. Accretion rates of S. patens are
expected to be somewhat less because S. patens
is a planophile species (flatter and closer to the
ground), and therefore less capable of trapping
sediments. By contrast, Phragmites australis is a
large plant with high biomass and effective
sediment trapping, and therefore has a
comparatively high accretion rate. On this basis,
we modeled rates specific to each wetland type
as follows:
• Phragmites australis: 10 mm/yr
• S. patens: 1.5 mm/yr
• S. altemiflora: 2 mm/yr
We recognize that accretion is a very complex
process and that specific rates may vary
significantly over space and time, but for
modeling purposes these habitat-specific
accretion rates were applied uniformly across the
study area.
A second algorithm determines if non-nourished
beach habitat will migrate inland or if migration
will be impeded by an armoring structure,
resulting in inundation. In this algorithm, the
distance the beach would be expected to migrate
inland is calculated using the Bruhn rule, which
states that for each vertical unit of sea level rise,
the beach will migrate 100 units inland.737
The third algorithm predicts the types and areal
extent of tidal wetland habitat that would have
existed in the study area if development had not
7'Titus and Narayanan, 1995 (see note 3); Huybrechts
et al., 2001 (see note 1).
7l7Bruhn. P., 1962, "Sea level rise as a cause of shore
erosion," American Society of Civil Engineers, Journal
of Waterways and Harbor Division 88:117-130.
occurred. This algorithm does not take sea level
rise into account.
Data Layers
Several GIS layers were required as inputs to the
inundation model. All data layers were in
Arclnfo grid format (raster) with a resolution of
30 x 30 m pixel size. By working at a high
spatial resolution, the model is able to address
the spatial heterogeneity of the spring tide as
well as the historical sea level rise rate.
The primary input layers included the following:
current habitat (as of 1995), elevation relative to
MTL (as of 1995), a layer delineating the
historical rate of sea level rise, a layer
delineating the spring tide range, and a separate
layer for each of five armoring scenarios.
Two additional layers were created to delineate
areas where no change in habitat was allowed to
occur. The first of these "masks" covered two
tidal deltas: Beach Haven Inlet and Barnegat
Inlet (see Plate 21 in the appendix). The
assumption was made that river- and tidal-borne
sediments would replenish these areas. The
second mask prevented any alteration of beaches
on the eastern shore of the barrier island, because
the assumption was made that beaches would be
protected from inundation by nourishment with
imported sand.
The "current" habitat layer was created by
combining data from several source layers. The
primary source was 1995 Landsat TM satellite
data created by the Grant F. Walton Center for
Remote Sensing and Spatial Analysis at Rutgers
University.738 The Landsat data were then
combined with another layer from Rutgers of
SAV that showed the extent of this vegetation as
of 1999.739 Data showing the extent of intertidal
flats and subtidal pools, from NWI data,74" were
combined with the other two layers to produce a
CRSSA, 2000 (see note 721).
7y'CRSSA. 1999, Rutgers University, 19991118,
Submerged Aquatic Vegetation in Barnegat Bay —
1999. Digital GIS data, Center for Remote Sensing and
Spatial Analysis.
74uUSFWS, n.d., National Wetlands Inventory, accessed
on December 28, 2001, at http://www.nwi.fws.gov.
-------
[ 306 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Table 3.2. Habitat classifications and elevation ranges
Modeled habitat description Elevation range3
Beach na
Marine/estuarine unconsolidated shore: mud/organic
< = MTL
S. alterniflora
> MTL to LM
S. patens
> LM to HM
Phragmites australisb
> LM
Upland
> HM
Open water
MTL to-1 m
Upland
> HM
SAV beds
< = MTL
Marine/estuarine intertidal flats
< = MTL
Marine/estuarine subtidal pools
< = MTL
Intertidal mixed wetlands
na
a Upper elevations calculations:
HM = [MTL + (Spring tide range/2) + 0.3048 m]
LM = [0.666 * (Spring tide range/2)]
b Phragmites occurs both within the HM range and above HM range.
final composite habitat layer. One final
modification was made to add a strip of wetlands
where unarmored wetland abuts open water
(intertidal mixed wetlands) to more realistically
estimate the current habitat.
The elevation layer was created through
interpolation of USGS DLG contours, U.S.
Army Corps of Engineers point spot elevation
data, and wetland boundaries created by the New
Jersey Department of Environmental Quality.
Elevations were relative to MTL and were
adjusted from the 1969 tidal epoch to 1995 using
the historical rate of sea level rise. Spring tide
range and historical sea level rise rate layers
were generated by interpolation of tide gauge
data.
Modeled Habitats
The model evaluated potential changes in the
areal extent of tidal wetland habitats
(.Phragmites, S. alterniflora, and S. patens),
sandy beaches, SAV, and open water habitat. All
upland habitats were modeled as a single
"upland" category, intertidal habitats were not
modeled, and it was assumed that beach loss
would be minimal because of beach nourishment
of the majority of beaches in the study area.
Using the set of input layers, the program
determines for each 30 x 30 m pixel of habitat,
elevation relative to MTL, spring tide range, and
historical sea level rise rate. The elevation ranges
for specific habitats are shown in Table 3.2.
Changes in habitat type were based on elevation
changes relative to MTL resulting from net sea
level rise (historical sea level rise rate, plus
acceleration rate, minus estimated accretion rate)
over 200 years and the relation of each habitat to
the spring tide range (see Figure 3.2).
Because the habitat and elevation data sets were
derived independently, the initial 1995 habitat
layer does not always correspond to the elevation
range outlined in Table 3.2. These
elevation/habitat "mismatches" are preprocessed
by the model before any further processing by
adjusting the elevation at that location to the
elevation appropriate to the habitat found there.
Scenarios Evaluated
We used the model to examine habitat changes
on an annual basis over a period of 200 years
under various sea level rise rates and armoring
scenarios. In addition, a historical scenario was
developed to predict what type of wetland habitat
would have existed in currently developed areas
in the absence of development. Sea level rise was
not taken into account for this scenario. For all
scenarios, it was assumed that local communities
would replenish beaches as needed.
-------
[ SECTION 3.20 307 ]
(1.1 m*) Upper
limit of High Marsh
(0.53 m») Upper J" High Salt Marsh
limit of Low Marsh
}
Low Salt Marsh
(0.0 m)MTL (1995) "
. Intertidal
flats/Subtidal pools
(-1.0 m*) Lower
limit of S AV
I
}
SAVBeds
Figure 3.2. Hypothetical shoreline profile showing relationship between habitat type and elevation
range relative to 1995 mean tide level (MTL).
The sea level rise and armoring scenarios were
digitally mapped, and changes in the areal extent
of various habitat classes under different
scenarios were quantified. Two accelerated sea
level rise rates were evaluated, 3 and 9 mm
annual increases above the historical rate. For
each sea level rise rate, six levels of response to
sea level rise were evaluated: no armoring;
current level of armoring; armoring scenario 1
(areas where there is a legal right to hold back
the sea); armoring scenario 2 (areas that will
probably be armored based on the best judgment
of local planners); armoring scenario 3 (the same
as scenario 2 except that no armoring is assumed
in areas identified by planners where wetland
migration might occur, because of increased
environmental concerns or doubts about the cost-
effectiveness of shore protection); and armoring
scenario 4 (areas that should not be armored
based on environmental considerations). The
armoring scenarios were developed in
consultation with local planners.
Armoring scenarios assumed placement of
armored structures such as bulkheads on the
landward side of mean high water (MHW)741 or
mean higher high water (MHHW).
742
Methods for Quantifying Changes in Biota
Because the focus of our habitat analysis was on
tidal marshes, SAV, and open water, estimates of
changes in biota focused on species in these
habitats, with a focus on avifauna, finfish, and
nekton. Because of a general lack of data on the
production of such species in these habitats, this
version of the model makes the simplifying
assumption that in most cases species losses will
be proportional to habitat losses. This
assumption can be modified as more data
become available.
741The average height of high waters (maximum height
reached by a rising tide) over a 19 year period.
742The average height of the higher high waters (the
higher of two high waters of a tidal day) over a 19 year
period.
*Note: In the model, "elevations" are determined by mean tide level (MTL) and spring tide range of each cell.
-------
[ 308 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Table 3.3. Modeling assumptions for bird species
1 Species
Habitat
Modeling assumptions 1
Migrating waterfowl — dabbling
ducks
SAV
Stable population until habitat loss exceeds 33%,
then 1:1 decrease in abundance with loss of SAV
Migrating waterfowl — diving ducks
Open water
Increase in wintering habitat, but no increase in
population, because limiting factors are probably
not winter habitat
Loons, grebes
Open water
Increase in wintering habitat, but no increase in
population, because limiting factors are probably
not winter habitat
Mergansers, buffleheads
Open water
25% increase in abundance with increase in area
of open water
Songbirds — marsh wrens
Phragmites marsh
1:1 decrease in abundance with loss of
Phragmites
Songbirds — seaside sparrows
S. alterniflora marsh
1:1 decrease in abundance with loss of
S. alterniflora
Songbirds — sharp-tailed sparrows
S. patens marsh
1:1 decrease in abundance with loss of S. patens
Table 3.4. Modeling assumptions for finfish in SAV and Spartina marshes
Species
Finfish:
fourspine stickleback (Apeltes quadracus)
naked goby (Gobiosoma bosci)
northern pipefish (Syngnathus fuscus)
rainwater killifish (Lucania parva)
Finfish:
Atlantic silverside (Menidia menidia)
mummichog (Fundulus heteroclitus)
bay anchovy (Anchoa mitchilli)
Habitat
SAV
Modeling assumptions
1:1 decrease with loss of SAV
Spartina marsh 1:1 decrease with loss of Spartina marsh
Birds
Table 3.3 summarizes our assumptions about
how the relative abundances of representative
bird species in the study area will change with
changes in the areal extent of different habitats.
These assumptions are based on best
professional judgment. The inundation model
does not consider salt marsh islands or intertidal
sand and mudflats, and assumes that there will
be beach nourishment on the ocean side of the
barrier island, which represents the majority of
the beach habitat. Therefore, our analysis does
not consider potential changes in migratory
shorebirds, nesting shorebirds, or colonial
nesting birds that depend on these habitats.
Estimations of changes in dabbling duck
abundance in SAV are based on the assumption
that current SAV can accommodate a 50 percent
annual variation in bird abundance, but that loss
of greater than 33 percent of SAV habitat will
result in a 1:1 decrease in dabbling duck
abundance. For birds using open water habitats
in winter, increases in open water will provide
increased habitat, but will not result in
population increases, because the limiting factors
on diving duck, loon, grebe, and merganser
populations are not likely to be wintering habitat.
For birds breeding in marsh habitats, the long-
term percent change in bird abundance is
assumed to be the same as the long-term habitat
change.
Relative Abundances of Finfish in Spartina
Marshes and SA V
Relative abundances of fish in SAV and tidal
marsh were modeled on the basis of data from
Great Bay-Little Egg Harbor, adjacent to the
Barnegat Bay study area.743 As indicated in Table
3.4, we assumed that there will be declines in the
growth, survival, or reproduction of the
743
Sogard and Able, 1991 (see note 94).
-------
[ SECTION 3.20 309 ]
Above-ground net primary production 1,250 g dw m"2
Figure 3.3. Production flows to nekton from net annual marsh primary production.
Source: After Figure 1 in Kneib (see text note 276).
dominant species in each habitat, resulting in
declines in abundance proportional to habitat
losses.
Annual Production of Nekton in Spartina
Marshes
We estimated annual production of nekton
(actively swimming fish and shrimp) in Spartina
marshes based on consultation with a local
expert (Dr. Michael Weinstein, Director, New
Jersey Sea Marine Sciences Consortium) and
data and methods in Kneib.744 Kneib used two
alternative methods to estimate the annual
production of nekton in tidal wetlands. First,
Kneib developed an estimate of annual nekton
production by multiplying estimated mean
annual standing stock biomass by a
production:biomass (P:B) ratio. Based on a
review of the scientific literature, Kneib used a
P:B ratio of 2 for marsh fishes, 3 for penaeid
shrimp, and 5 for caridean shrimp. On this basis,
744Kneib, 1997 (see note 17).
Kneib estimated that annual nekton production in
Spartina marshes averages 1.5 g dry weight
(g dw) m"2.
Kneib also developed a simple trophic transfer
model to estimate the annual production of
nekton resulting from the annual above-ground
production of Spartina alterniflora. The model is
based on the premise that the primary production
of salt marshes is linked to the secondary
production of both resident and transient
nekton.745 Kneib's model is summarized in
Figure 3.3.
745Weinstein, 1979 (see note 361); Weinstein, M.P.,
1983, "Population dynamics of an estuarine-dependent
fish, the spot (Leisotomus xanthurus) along a tidal
creek-seagrass meadow coenocline," Canadian Journal
of Fisheries and Aquatic Sciences 40:1633-1638;
Weigert, R.G. and L.R. Pomeroy, 1981, "The salt-marsh
ecosystem: A synthesis," in The Ecology of a Salt
Marsh, L.R. Pomeroy and R.G. Weigert (eds.), Springer
Verlag, New York, pp. 219-230; Boesch and Turner
(see note 318); Deegan, L.A., 1993, "Nutrient and
-------
[ 310 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
The model estimates that a total of 4.2 g dw m"2
of nekton is supported by the original 1,250 g dw
m"2 of above-ground plant production. Of this
total, Kneib assumed that two-thirds (2.8 g) are
resident species (e.g., killifishes such as
Fundulus spp.) and one-third (1.4 g) are
estuarine migrants (e.g., juvenile white shrimp
Litopenoeus setiferns).746 Estimates in other
studies of annual productivity of fish and shrimp
in tidal marshes range from 9 to 16 g dw m"2 yr"1
for shrimp, from 10.2 to 16 g dw m"2 yr"1 for
mummichog (Fundulus heteroclitus), and from
22.1 to 48.5 g dw m"2 yr"1 for total fish (review in
Strange et al.747). Many of these studies estimate
secondary productivity based on the total
regional fisheries yield per unit area of
supporting marsh. These results suggest that
Kneib's estimate of 4.2 g dw m"2 may represent a
lower bound estimate of marsh secondary
productivity.
Results and Discussion
Results of the pilot study make clear that as
armoring increases in response to anticipated sea
level rise, there are likely to be substantial
adverse impacts to certain coastal habitats and
the species supported by those habitats. Even
minimal armoring is predicted to substantially
reduce the abundance and production of finfish
and birds in coastal areas as critical habitats are
lost or converted.
energy transport between estuaries and coastal marine
ecosystems by fish migration," Canadian Journal of
Fisheries and Aquatic Science 50:74-79; Weinstein,
M.P. and S.Y. Litvin, 2000, "The role of tidal salt marsh
as an energy source for marine transient and resident
finfishes: A stable isotope approach," Transactions of
the American Fisheries Society 129:797-810; Kneib,
1997 (see note 17); Kneib, 2003 (see note 276); Deegan
et al., 2000 (see note 428), in Weinstein and Kreeger,
pp. 333-368 (see note 410).
746Kneib, 2003 (see note 276).
747Strange, E., H. Galbraith, S. Bickel, D. Mills, D.
Beltman, and J. Lipton, 2002, ""Determining ecological
equivalence in service-to-service scaling of salt marsh
restoration," Environmental Management 20:290-300.
Habitat Changes
The appendix (map plates) and Table 3.5 show
predicted changes in the distribution of the
modeled coastal habitat types after 200 years
under the different sea level rise and armoring
scenarios. The predicted change in the areal
extent of S. alterniflora is shown in Figure 3.4,
S. patens in Figure 3.5, Phragmites in Figure 3.6,
SAV in Figure 3.7, and open water in Figure 3.8.
Under all sea level rise and armoring scenarios,
there are substantial declines in Spartina
marshes, with more S. patens marsh lost
compared to S. alterniflora marsh. This is to be
expected given the lower accretion rate of S.
patens marsh. The greatest declines in both S.
alterniflora and S. patens occur under armoring
scenario 1 for both 3 and 9 mm accelerated sea
level rise rates.
Phragmites marsh, which is assumed to accrete
at a rate that is five times higher than
S. alterniflora, persists under a 3 mm accelerated
sea level rise rate, but declines under a 9 mm
increase.
SAV increases under armoring scenario 4,
assuming a 3 mm accelerated rate of sea level
rise. In contrast, SAV declines substantially
under all 9 mm scenarios. The greatest decline in
SAV occurs under the assumption of a 9 mm rate
of sea level rise and armoring scenario 1.
Open water habitat increases under all sea level
rise scenarios. The greatest increase occurs under
the unarmored scenario and a 9 mm accelerated
sea level rise rate. Note that because the model
assumes that there will be beach nourishment for
the majority of beaches in the study area, the
extent of sandy beach habitat is relatively
unchanged.
-------
[ SECTION 3.20 311 ]
Table 3.5. Area comparison of current (1995) coastal habitat (in hectares) to estimates modeled under six shoreline protection (armoring)
scenarios and two accelerated sea level rise rates above the historical rate
3 mm1 accelerated sea level rise
9 mma accelerated sea level rise
Scenario
Low salt
marsh S.
alterniflora
dominant
High salt
marsh
S. patens
dominant
High salt
marsh
Phragmite
s australis
dominant
Marine/
estuarine
open water
Sub-
aquatic
vegetation
Low salt
marsh S.
alterniflora
dominant
High salt
marsh
S. patens
dominant
High salt
marsh
Phragmite
s australis
dominant
Marine/
estuarine
open water
Sub-
aquatic
vegetation
Current (1995)
5,036
3,875
1,507
42,903
5,591
5,036
3,875
1,507
42,903
5,591
Unarmored
3,206
966
1,507
52,744
7,433
2,893
739
95
63,077
4,492
Current armoring
1,996
366
1,507
52,740
5,054
2,160
463
95
59,357
2,088
Armoring scenario 1b
1,625
211
1,507
52,737
3,940
1,551
196
95
57,788
954
Armoring scenario 2°
1,951
339
1,507
52,746
4,947
1,990
401
95
59,175
1,729
Armoring scenario 3d
2,081
395
1,507
52,742
5,461
2,143
456
95
59,905
2,231
Armoring scenario 4e
3,000
894
1,507
52,724
6,761
2,741
678
95
62,178
4,114
a 3 mm and 9 mm represent annual accelerated rates of sea level rise above the historical rate.
b Armoring scenario 1 = areas where there is a legal right to hold back the sea;
c armoring scenario 2 = areas that will probably be armored based on the best judgment of local planners;
d armoring scenario 3 = the same as scenario 2 except that no armoring is assumed in areas identified by planners where wetland migration might occur
due to increased environmental concerns, or doubts about the cost-effectiveness of shore protection);
8 armoring scenario 4 = areas that should not be armored based on environmental considerations.
-------
[ 312 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
120%
~ Spartina alterniflora - 3 mm
¦ Spartina alterniflora - 9 mm
100%
60%
40%
20%
0%
Historic Habitat
Unarmored Current Armoring
Armoring
Scenario 1
Armoring
Scenario 2
Armoring
Scenario 3
Armoring
Scenario 4
Figure 3.4. Under 3 and 9 mm accelerated sea level rise above historical levels by 2195 (200 years
from 1995) and unarmored, current armoring, and four policy-derived armoring scenarios involving
different degrees of armoring. (See notes in Table 3.5 for explanation of scenarios.)
-------
[ SECTION 3.20
120%
100%
~ Spartina patens - 3 mm
¦ Spartina patens - 9 mm
60%
40%
20%
Historic Habitat Unarmored Current Armoring Armoring
Scenario 1
Armoring
Scenario 2
Armoring
Scenario 3
Armoring
Scenario 4
Figure 3.5. Comparison of current and historical acreages of S. patens high saltmarsh habitat to
inundation-modeled acreages under 3 and 9 mm accelerated sea level rise above historical levels by
2195 (200 years from 1995) and unarmored, current armoring, and four policy-derived armoring
scenarios involving different degrees of armoring. (See notes in Table 3.5 for explanation of
scenarios.)
-------
[ 314 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
120%
100%
60%
40%
~ Phragmites australis - 3 mm
¦ Phragmites australis - 9 mm
20%
0% ^ , , , , , ,
Historic Habitat Unarmored Current Armoring Armoring Armoring Armoring Armoring
Scenario 1 Scenario 2 Scenario 3 Scenario 4
Figure 3.6. Comparison of current and historical acreages of Phragmites australis (high saltmarsh and
upland) habitat to inundation-modeled acreages under 3 and 9 mm accelerated sea level rise above
historical levels by 2195 (200 years from 1995) and unarmored, current armoring, and four policy-
derived armoring scenarios involving different degrees of armoring. (See notes in Table 3.5 for
explanation of scenarios.)
-------
[ SECTION 3.20
140%
120%
100%
80%
60%
40%
20%
Historic Habitat Unarmored Current Armoring
Armoring
Scenario 1
Armoring
Scenario 2
Armoring
Scenario 3
Armoring
Scenario 4
Figure 3.7. Comparison of current and historical acreages of SAV to inundation-modeled acreages
under 3 and 9 mm accelerated sea level rise above historical levels by 2195 (200 years from 1995) and
unarmored, current armoring, and four policy-derived armoring scenarios involving different degrees
of armoring. (See notes in Table 3.5 for explanation of scenarios.)
-------
[ 316 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
160% -
140%
120%
LO"
G)
O)
r 100%
c
o
0
1 80%
O)
03
o
o
03
c 60%
o
o
0
CL
40%
20%
0% -
Figure 3.8. Comparison of current and historical acreages of open water to inundation-modeled
acreages under 3 and 9 mm accelerated sea level rise above historical levels by 2195 (200 years from
1995) and unarmored, current armoring, and four policy-derived armoring scenarios involving
different degrees of armoring. (See notes in Table 3.5 for explanation of scenarios.)
Historic Habitat Unarmored Current Armoring Armoring Armoring Armoring Armoring
Scenario 1 Scenario 2 Scenario 3 Scenario 4
-------
[ SECTION 3.20 317 ]
~ SAY MSpartina
40 -r
20
0 —r i j —p
-20
-40
-60
-80 ^
-100
Unarmored Current Amoring Armoring Armoring Armoring
Armoring Scenario 1 Scenario 2 Scenario 3 Scenario 4
Figure 3.9. Percent change in relative abundances offish species in Spartina and SAV by 2195
under 3 mm accelerated sea level rise. (See notes in Table 3.5 for explanation of scenarios.)
~ SAV MSpartina
-10 —
-20 ——I
-30 -
-40 -
-50 -
-60 ™ ¦ ¦ ¦ —¦ ¦
-70 * ¦ ¦
-80 ^
-90 J
Unarmored Current Armoring Armoring Armoring Armoring
Armoring Scenario 1 Scenario 2 Scenario 3 Scenario 4
Figure 3.10. Percent changes in relative abundances offish species in Spartina and SAV by 2195
under 9 mm accelerated sea level rise. (See notes in Table 3.5 for explanation of scenarios.)
-------
[ 318 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Table 3.6. Current (1995) estimated annual production of nekton (in kg/ha/yr) in Spartina marsh in
the study area
Production under 3 mm accelerated
sea level rise
Production under 9 mm accelerated 1
sea level rise 1
Scenario
Low estimate
High estimate
Low estimate
High estimate 1
Current (1995)
133,666
374,265
133,666
374,265
Table 3.7. Estimated annual production in 200 years of nekton (in kg/ha/yr) in Spartina marsh in the
study area under different rates of accelerated sea level rise and alternative armoring scenarios3
Production under 3 mm
accelerated sea level rise
Production under 9 mm
accelerated sea level rise
Scenario
Low estimate High estimate
Low estimate
High estimate
No armoring
62,575
175,211
54,491
152,576
Current level of armoring
35,432
99,210
39,353
110,187
Armoring scenario 1
27,533
77,093
26,206
73,377
Armoring scenario 2
34,348
96,175
35,876
100,454
Armoring scenario 3
37,134
103,976
38,983
109,151
Armoring scenario 4
58,413
163,557
51,280
143,583
a See notes in Table 3.5 for explanation of scenarios.
Changes in Relative Abundances ofFinfish in
Spartina Marsh and SA V
Figure 3.9 shows predicted percent changes in
the relative abundances of resident finfish in
SAV and Spartina marsh under 3 mm
accelerated sea level rise and different degrees of
armoring based on data in Sogard and Able.748
Figure 3.10 provides results under 9 mm
accelerated sea level rise. SAV-dependent fish
species increase under the unarmored scenario
and armoring scenario 4 assuming a 3 mm
accelerated rate of sea level rise, but decline
substantially under all scenarios with a 9 mm
rise. By contrast, declines of Spartina-dependent
fish species are substantial under all sea level
rise and armoring scenarios.
Annual Production of Resident and Transient
Marsh Nekton
As indicated in the previous section, results of
Kneib indicate that production of nekton in
Spartina marshes ranges from 15 kg/ha/yr (1.5 g
m"2) based on P:B ratios to 42 kg/ha/yr (4.2 g m"
2) based on trophic transfer of marsh primary
production to nekton.749 To account for
uncertainty, these estimates were used as lower
and upper bound estimates of production. On this
basis, Table 3.6 presents estimated annual
production in the study area under current (1995)
conditions, and Table 3.7 presents predicted
changes by 2195 under the different sea level
rise and armoring scenarios.
Annual production of nekton declines
substantially as Spartina marsh is lost, ranging
from a decline of about 50-75 percent under a 3
mm accelerated sea level rise rate to about 60-80
percent under 9 mm. Such potentially dramatic
declines in the annual production of nekton is of
particular concern because many of these
species, such as spot (Leiostomus xanthurus) and
white perch (Morone americana), are important
for commercial and recreational fisheries.
Changes in Relative Abundances of Birds in
Spartina Marshes, SAV, and Open Water
Figure 3.11 shows predicted changes in the
relative abundances of representative bird
species in SAV, S. alterniflora, and S. patens
under 3 mm accelerated sea level rise and
748Sogart and Able, 1991 (see note 94).
749Kneib, 2003 (see note 276).
-------
[ SECTION 3.20 319 ]
-10
-20
-30
"40 1 1 1 1 -
-50 -
-60 ¦ 1 ¦ m -
-70 1_| -
-80
-90 1—1 1_| LI •—1
-100 -1
Unarmored Current Armoring Armoring Armoring Armoring
Armoring Scenario 1 Scenario 2 Scenario 3 Scenario 4
Figure 3.11. Percent changes in relative abundances of bird species by 2195 under 3 mm
accelerated sea level rise. (See notes in Table 3.5 for explanation of scenarios.)
~ SAY ¦ S. alterniflora ~ S. patens
0 ~i — — — — — — — — —
-10 — — — —
-20
-30 ¦ ¦— ¦ ¦ ¦ ¦
-40 L_ ¦ ¦ ¦ 1_
-50 ¦ ¦— ¦
-60 ¦ m
-70 ™
-80 I— LJ
-90 — |_| LJ
-100 J
Unarmored Current Armoring Armoring Armoring Armoring
Armoring Scenario 1 Scenario 2 Scenario 3 Scenario 4
Figure 3.12. Percent changes in relative abundances of bird species by 2195 under 9 mm
accelerated sea level rise. (See notes in Table 3.5 for explanation of scenarios.)
~ SAY ¦ S. alterniflora ~ S. patens
different degrees of armoring. Figure 3.12
provides results under 9 mm accelerated sea
level rise. The greatest losses occur for songbirds
in S. patens, followed by songbirds in S.
alterniflora. SAV-dependent species such as
dabbling ducks show no change under a 3 mm
accelerated sea level rise rate, and no change
under a 9 mm accelerated sea level rise rate
under the unarmored scenario and with minimal
armoring (armoring scenario 4). However, under
a 9 mm sea level rise, decreases in SAV-
dependent bird species are significant with
current armoring and armoring scenarios 1, 2,
and 3. However, the percent change is still
substantially less than for songbirds in Spartina
marshes.
Conclusions and Directions for Future
Research
The inundation and biological production models
developed for this study function as intended and
can be used to develop an order of magnitude
approximation of changes in the production of
birds, finfish, and shrimp under a variety of sea
level rise and armoring scenarios. Such
information can help guide stakeholders and
decision-makers as they plan responses to
anticipated sea level rise.
One of the unique features of this model is that it
evaluates accretion, sea level rise, and habitat in
a spatially explicit manner (i.e., on a cell by cell
basis). This made it possible to use accretion
rates specific to different marsh vegetation types
-------
[ 320 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
(1.5 mm/yr for S. patens, 2 mm/yr for S.
alterniflora, and 10 mm/yr for Phrcigmites).
Because Phragmites is assumed to accrete at
such a relatively high rate, this vegetation type is
able to keep pace with the 3 mm accelerated sea
level rise rate.
In addition, our model is able to capture local
variation in mean tide level and therefore sea
level rise, rather than treating the entire area as a
homogenous unit. This means the model was
able to consider local tide levels related to
subsidence, etc. The model can also be used to
conduct a sensitivity analysis to examine the
effects of different values of input parameters on
model predictions. Model output can be
generated for any time interval of interest.
The inundation model is flexible, and
assumptions and mapping rules can be revised as
needed for different study sites or to
accommodate improved or additional physical
and biological data. It is important to gather
additional data to test the assumptions of this
version of the model and to improve the
accuracy and reliability of model predictions.
This is particularly important because different
scenarios of sea level rise rates and armoring
may have different impacts on future coastal
habitats than those predicted by our model based
on current data and assumptions. This version of
the inundation model examines potential changes
in tidal marshes, SAV, sandy beaches, and open
water habitats only, and makes a number of
simplifying assumptions about how these
habitats will change in response to sea level rise
and shoreline armoring. Further analysis should
examine other potentially important physical
variables such as slope, overwash, fetch, and
sediment inputs from the surrounding watershed
to determine their relative influence on habitat
predictions.
Future research should also address other
habitats in addition to the four major habitat
types considered here. For example, there are
likely to be changes in the extent and distribution
of intertidal mudflats. Loss of intertidal flats is
expected to lead to declines in shorebirds such as
semipalmated plover (Charadrius
semipalmatus), red knot (Calidris caniitus), and
dunlin (Calidris alpina) that rely on these
habitats for feeding during their migrations and
• 750
over winter. -
Colonial nesting birds such as gulls and terns
nest on salt marsh islands in the bay,751 and loss
of this habitat could also have important
consequences. In 1989, more than 11,000 gulls,
primarily laughing gulls (Lams atricilla), were
observed in Barnegat Bay, and in 1995, 5,000
gulls, mostly herring gulls (Lams argentatus)
and great black-backed gulls (Lams marinas),
were observed. There were 5,000 terns observed
in 1989 and 2,600 in 1995, mostly common tern
(Sterna hirundo). In 1989 there was one colony
of least tern (Sterna antillarum), a state-listed
endangered species, and in 1989 there was one
colony of Forster's tern (Sterna forsteri).
Additional loss of the habitats that these species
rely on from sea level rise may add significant
stress to these populations that are already at
risk.
For this analysis, we make the simplifying
assumption that in most cases species losses will
be proportional to habitat losses. Future versions
of the model should examine other possible
relationships between habitat loss and production
of coastal biota. It will also be important to
validate the assumptions of the trophic transfer
model and the P:B ratio approach to estimating
annual production of nekton. Other changes
might include evaluation of the importance of
the spatial configuration of habitat patches or
patch size. It would also be useful to predict how
sandy beach habitat and biota would change if no
beach nourishment occurs. Beaches are essential
for horseshoe crab spawning, and horseshoe crab
eggs are a critical component of the diets of
migratory birds. Therefore, losses of beaches
could have important consequences for these
species.
75"Galbraith et al., 2002 (see note 50); Galbraith, H., R.
Jones, R. Park, J. Clough, S. Herrod-Julius, B.
Harrington, and G. Page, 2003, "Global climate change
and sea level rise: potential losses of intertidal habitat
for shorebirds," in Ecological Forecasting: New Tools
for Coastal and Marine Ecosystem Management, N.
Valette-Silver and D. Scavia (eds.), NOAA technical
memorandum NOS NCCOS 1, NOAA, Silver Spring,
MD, pp. 19-22.
751USFWS, 1997 (see note 172).
-------
[ SECTION 3.20 321 ]
Despite the limitations of the current version of
the inundation and biological production models,
results of this study make clear that there may be
substantial changes in coastal habitats and biota
in response to sea level rise and shoreline
armoring, and that the model can be used to
evaluate the potential effects of shoreline
armoring on these resources. For this reason, it is
imperative that tools such as these be refined to
the extent possible to provide resource managers
and stakeholders with the information necessary
for planning responses consistent with resource
goals.
The technical work that forms the basis for this
report (this Section 3.20)was funded by
the Global Programs Division of the U.S.
Environmental Protection Agency's (EPA's)
Office of Atmospheric Programs under Contract
No. 68-W02-027. The report itself was prepared
by Stratus Consulting with corporate
development funds. James G. Titus, the EPA
work assignment manager, developed the sea
level rise and armoring scenarios that were
evaluated as well as the habitat-elevation
relationships used in the inundation model. Dr.
Michael P. Weinstein of the New Jersey Marine
Sciences Consortium, Sandy Hook Field Station
provided valuable assistance with the analysis of
effects on fish production of changes in marsh
habitat. Dr. Michael Kearney of the University of
Maryland developed accretion rates. ICF
Consulting Inc. provided elevation data, and
Industrial Economics developed the armoring
scenarios in consultation with local planners.
The conclusions presented in this report are those
of the authors and do not represent the opinions
of subcontractors or the official position of the
EPA.
-------
Appendix: GIS Maps of Modeled Habitat Changes
~ CAFR boundary
Ocean County current wetland habitat
~ Beach
HH Marine/estuarine mud''organic
i I Low salt marsh: Spartina alterniflora
M High salt marsh: Spartina patens
|H High salt marsh/upland: Phragmites australis
HI Upland
j I Open water
I Sub aquatic vegetation
| Marine'est. intertldal flats
H Marine/est. subtidal pools
¦ Intertidal mixed wetlands
Bamegat Bay
Plate 1. The study area along coastal Ocean County, New Jersey, including Barnegat Bay, inland
to the boundary of the zone defined by New Jersey's Coastal Areas Facilities Review Act
(CAFRA).
-------
[ SECTION 3 APPENDIX
Ocean County
Ocean County current wetland habitat
I I Beach
H Marine/estuarine mud/organic
I 1 Low salt marsh Spartina alterniflora
ED9 High salt marsh: Spartina patens
H High salt marsh/upland: Phragmites australis
¦1 Upland
I I Open water
~ Sub aquatic vegetation
Marine.'est intertidal flats
HI Marine/est subtidal pools
¦ Intertidal mixed wetlands
j /profects/9rmofing/a
-------
[ 324 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
County
Ocean County historic wetland habitat (modeled)
I 1 Beach
IH Marine/estuarine mltd/organic
n Low salt marsh: Spartina alterniflora
I 1 High satt marsh: Spartina patens
HI High satt marsh/upland: Phragmites australis
¦¦ Upland
I I Open water
Sub aquatic vegetation
HI Marine/est, intertidal flats
1^1 Marine/est. subtidal pools
¦ Intertidal mixed wetlands
J /proj©cts/arTOring/arrife_apfVrnod<#esu!te mxd
Plate 3. Distribution of wetland habitats estimated by conversion of developed lands into
elevation-dependent wetland types.
-------
[ SECTION 3 APPENDIX
Ocean County
Ocean County wetland habitat by 2195
(3mm acclerated SLR, no shoreline protection)
I I Beach
Marine'estuarine mud/organic
[ 1 Low salt marsh: Spartina alterniflora
@ High salt marsh: Spartina patens
M High salt marsh/upland: Phragmites australis
¦i Upland
1 1 Open water
I I Sub aquatic vegetation
¦ Marlne/est. intertida! flats
H Marine/est subtidal pools
H Intertida I mixed wetlands
j fpro]eds/armorir»9/amfe_ap
-------
[ 326 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Ocean County
t'J
fj
<£ry
-1J
Rf|
's?>7
¦'4
f
Ocean County wetland habitat by 2195
(9mm acceferated SLR, no shoreline protection)
I I Beach
HI Marine/estuarine mud/organic
I l Low salt marsh: Spartina alterniflora
H High salt marsh: Spartina patens
¦I High salt marsh/upland: Phragmites australis
¦¦ Upland
I I Open water
I 1 Sub aquatic vegetation
H Marine/est. intertidal flats
¦ Marine/est. subtidal pools
H Intertidal mixed wetlands
0 1.25 2.5
7.5 10
j /proj©cts/ar
-------
[ SECTION 3 APPENDIX 327 ]
County
Ocean County current wetland habitat
I I Beach
¦I Marine/estuanne mud/organic
I 1 Low salt marsh: Spartina alterniflora
High salt marsh: Spartina patens
H High salt marsh/upland: Phragmites australis
HI Upland
I I Open water
I I Sub aquatic vegetation
Marine/est intertidal flats
¦ Marine/est. subtidal pools
Intertidal mixed wetlands
Current armoring
¦ Current development
j/profects/armonng/amte_afws/modelresiitts mxd
Plate 6. Current armoring scenario —
1995.
currently developed lands shown on top of wetlands as of
-------
[ 328 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
County
Ocean County current wetland habitat
~ Beach
Marine/estuarine mud/organic
I I Low sail marsh: Spartina alterniflora
I 'M High salt marsh: Spartina patens
High satt marsh/upland: Phragmitesaustralis
HI Upland
I 1 Open water
I I Sub aquatic vegetation
HH Marine/est. intertidal flats
|^| Marine/est. subtidal pools
H Intertidal mixed wetlands
Armoring scenario 1
HH Areas where there is a legal right to hold back the sea
j! projects/a rnx>r mg/a mfe_a prVmodeif esu.'ts rnxd
Plate 7. Armoring scenario 1 (areas where there is a legal right to hold back the sea) shown on top
of wetlands as of 1995.
-------
[ SECTION 3 APPENDIX
County
Ocean County current wetland habitat
I 1 Beach
H Marine/estuarine mud/organic
~ Low salt marsh; Spartina alterniflora
139 High salt marsh: Spartina patens
H High salt marsh/upland: Phragmitesaustralis
¦¦ Upland
I 1 Open water
I 1 Sub aquatic vegetation
Marine/est. intertidal flats
[^1 Marine/est. subtidal pools
¦ Intertidal mixed wetlands
Armoring scenario 2
| Areas that will probably be armored based on the best
judgment of local planners
j /pro]?>cJs/anrorrrvgilatnts_ap(Vmo
-------
[ 330 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
County
Ocean County current wetland habitat
I 1 Beach
!¦ Marine,''estuarine mud/organic
I I Low sail marsh: Spartina alterniflora
I *31 High salt marsh: Spartina patens
High saft marsh/upland: Phragmitesaustralis
¦¦ Upland
I 1 Open water
I I Sub aquatic vegetation
H Marine/est. intertidal flats
H Marine/est. subtidal pools
j^H Intertidal mixed wetlands
Armoring scenario 3
HH The same as scenario 2 except for that no armoring is assumed
in areas identified by planners where wetland migration might
occur due to increased environmental concerns, or doubts
about the cost-effectiveness of shore protection
j /proj©cts/artr©rmg/amfe_apis/mode5fesusis mxd
Plate 9. Armoring scenario 3 (the same as scenario 2 except that no armoring is assumed in areas
identified by planners where wetland migration might occur due to increased environmental
concerns, or doubts about the cost-effectiveness of shore protection) shown on top of wetlands
as of 1995.
-------
[ SECTION 3 APPENDIX
County
Ocean County current wetland habitat
I I Beacti
H Marine/estuarine mud/organic
t 1 Low salt marsh: Spartina aiterniflora
Bl High salt marsh: Spartina patens
High salt marsh/upland: Phragmites australis
HH Upland
I I Open water
I J Sub aquatic vegetation
Marine/est. intertidal flats
H Marine/est. subtidal pools
¦ Intertidal mixed wetlands
Armoring scenario 4
H Areas that should not be armored based on
environmental considerations
J /prot«ctVa»mor«r»g/amte_aprs/modelr*Mjlts mxd
Plate 10. Armoring scenario 4 (areas that should not be armored based on environmental
considerations) shown on top of wetlands as of 1995.
-------
332 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE
Ocean County
Ocean County wetland habitat by 2195
(3mm acclerated SLR, current shoreline protection)
[ I Beach
Marine/estuarine mud/organic
I ] Low salt marsh: Spartina altemiflora
I High salt marsh: Spartina patens
H High salt marsh/upland: Phragmites australis
HI Upland
I I Open water
I I Sub aquatic vegetation
H Marine/est. intertidal flats
IH Marine/est. subtidal pools
H Intertidal mixed wetlands
0 1.25 2.5
j /pfOjects/arrrofing/amts._apfs'mod®*esuit» mxd
Plate 11. Distribution of wetland habitat types by 2195 modeled with current shoreline protection
and 3 mm accelerated rate of SLR above the historic.
-------
[ SECTION 3 APPENDIX 333 ]
Ocean County
Ocean County wetland habitat by 2195
(9mm acclerated SLR, current shoreline protection)
I I Beach
WM Marine/estuarine mud/organic
I I Low salt marsh: Spartina alterniflora
3 High salt marsh: Spartina patens
¦I High salt marsh/upland: Phragmites australis
¦¦ Upland
I I Open water
I I Sub aquatic vegetation
HI Marine/est. intertidal flats
¦ Marine/est. subtidal pools
H Intertidal mixed wetlands
0 1.25 2.5
7.5
10
rf Miles
JVprof©ds/a»mormg/amte_apr&'mo
-------
[ 334 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
County
Ocean County wetland habitat by 2195
(3mm acclerated SLR, scenariol shoreline protection)
I I Beach
Bflj Marine/estuarine mud/organic
[ 1 Low sail marsh: Spartina alterniflora
I J High saft marsh: Spartina patens
¦I High salt marsh/upland: Phragmites australis
¦¦ Upland
I I Open water
IM Jl Sub aquatic vegetation
H Manne/est. intertidal flats
H Manne/est. subtidal pools
H Intertidal mixed wetlands
j /proi©cSs/armormg/amss_apfs/modcVe«.i»ts m*d
Plate 13. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
1 (areas where there is a legal right to hold back the sea) and 3 mm accelerated rate of SLR above
the historic.
-------
[ SECTION 3 APPENDIX 335 ]
Ocean County
Ocean County wetland habitat by 2195
(9mm acclerated SLR. scenariol shoreline protection)
I I Beacti
¦I Marine/estuarme mud/organic
I I Low salt marsh: Spartina altemiflora
I 1 High salt marsh: Spartina patens
High salt marsh/upland: Phragmites australis
Upland
I 1 Open water
¦H Sub aquatic vegetation
H Marine,''est, Intertidal flats
Marine/est subtidal pools
¦ Intertidal mixed wetlands
0 1.25 2.5
7.5 10
j /projects/affrcifing/amis^apfs/mocleiesuits mxd
Plate 14. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
1 (areas where there is a legal right to hold back the sea) and 9 mm accelerated rate of SLR above
the historic.
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[ 336 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Ocean County
Ocean County wetland habitat by 2195
(3mm acclerated SLR, scenario2 shoreline protection)
I I Beach
HI Marine,''estuarine mud/organic
Low salt marsh: Spartina alterniftora
I I High salt marsh: Spartina patens
M8 High salt marsh/upland: Phragmites australis
Upland
I I Open water
I I Sub aquatic vegetation
Marme/est. intertidal flats
Marine/est. subtidal pools
| Intertidal mixed wetlands
J /projects/armor«^g/amte_ap»s/mod®^esuits mxd
Plate 15. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
2 (areas that will probably be armored based on the best judgment of local planners) and 3 mm
accelerated rate of SLR above the historic.
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[ SECTION 3 APPENDIX 337 ]
Ocean County
Ocean County wetland habitat by 2195
(9mm acclerated SLR, scenario2 shoreline protection)
I I Beach
H Marine/estuanne mud/organic
~ Low salt marsh Spartina alterniflora
~1 High satt marsh: Spartina patens
H High salt marsh/upland; Phragmites australis
H Upland
I 1 Open water
I I Sub aquatic vegetation
HI Marine/est. intertidal flats
H Marine/est. subtidal pools
¦ Intertidal mixed wetlands
0 1.25 2,5 5 7.5 10
I Miles
j /p^ojea^frnoring/amis^apis/iriodeiresuJte mxd
Plate 16. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
2 (areas that will probably be armored based on the best judgment of local planners) and 9 mm
accelerated rate of SLR above the historic.
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[ 338 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Ocean County
Ocean County wetland habitat by 2195
(3mm acclerated SLR, scenario3 shoreline protection)
I I Beach
m Marine/estuarine mud/organic
I I Low salt marsh Spartina alterniflora
I I High salt marsh. Spartina patens
9 High satt marsh/upland: Phragmites australis
¦1 Upland
I l Open water
I I Sub aquatic vegetation
H Marine/est. intertidal flats
IHI Marine/est. subtidal pools
¦ Intertidal mixed wetlands
j /pfOjexSs/a rmor mg/a esuits mxd
Plate 17. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
3 (the same as scenario 2 except that no armoring is assumed in areas identified by planners
where wetland migration might occur due to increased environmental concerns, or doubts about
the cost-effectiveness of shore protection) and 3 mm accelerated rate of SLR above the historic.
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[ SECTION 3 APPENDIX 339 ]
Ocean County
Ocean County wetland habitat by 2195
(9mm acclerated SLR, scenario3 shoreline protection)
I I Beach
Marine,''estuarine mud/organic
Low sail marsh: Spartina alterniflora
I I High salt marsh: Spartina patens
¦ High salt marsh/upland: Phragmites australis
Upland
I 1 Open water
I E11 Sub aquatic vegetation
H Marine/est, intertidal flats
Marine/est. subtidal pools
H Intertidal mixed wetlands
0 1.25 2.5
7.5 10
J /projed&/ar
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[ 340 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Ocean County
Ocean County wetland habitat by 2195
(3mm acclerated SLR, scenario4 shoreline protection)
I I Beach
H Marine/estuarine mud/organic
I I Low salt marsh Spartina alterniflora
I I High salt marsh: Spartina patens
| High salt marsh/upland: Phragmites australis
¦I Upland
I I Open water
I I Sub aquatic vegetation
H Marine/est. intertidal fiats
Marine/est. subtidal pools
H Intertidal mixed wetlands
0 1.25 2.5 5 7.5 10
I Miles
j /prO|ectsterrTOfirvg'amte_aprVmodfrVes'jlts rrad
Plate 19. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
4 (areas that should not be armored based on environmental considerations) and 3 mm
accelerated rate of SLR above the historic.
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[ SECTION 3 APPENDIX
Ocean County
¦¦r!
r -4
:¦ •; 4
~ * ' y)i l
¥
" 4J
f* A
Ocean County wetland habitat by 2195
(9mm acclerated SLR, scenario4 shoreline protection)
I I Beach
HH Marine,'estuarine mud/organic
0 Low salt marsh: Spartina altemiflora
1 I High satt marsh: Spartina patens
¦I High satt marstVupland: Phragmites australis
¦¦ Upland
~ Open water
fcj Sub aquatic vegetation
Manne/est. intertidal flats
Manne/est subtidal pools
¦ Intertidal mixed wetlands
A $
0 1.25 2.5 5 7.5 10
./
:• 1"'
Tf. .;U
Mfesfc-y J
ft"' V r
p... v;-
T'. '- / vy
V ^
1/>T
mmf/
j fproj«cis/araxM>ingtem&_apfflAnoda9r^ll& trued
Plate 20. Distribution of wetland habitat types by 2195 modeled with shoreline protection scenario
4 (areas that should not be armored based on environmental considerations) and 9 mm
accelerated rate of SLR above the historic.
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[ 342 MID-ATLANTIC COASTAL HABITATS & ENVIRONMENTAL IMPLICATIONS OF SEA LEVEL RISE ]
Ocean County
HI Beach Haven Inlet protected area)
¦I Barnegat Inlet {protected area)
Ocean County current wetland habitat
I I Beach
¦I Marine/estuarine mud/organic
n Low salt marsh: Spartina alterniflora
I High salt marsh: Spartina patens
High salt marsh/upland: Phragmites australis
HI Upland
I I Open water
I I Sub aquatic vegetation
HI Marine/est Intertidal flats
flH Marine/est. subtidal pools
H Intertidal mixed wetlands
0 1.25 2.5 5 7.5 10
Inlet
j7proj«*ts/arrr©ring/arnk_ap'is'mod®*e«ij»ts mxd
Haven Inlet
Barnegat
Plate 21. Distribution of wetland habitats as of 1995 with delta areas that were masked from model
analysis shown in red and black.
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