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

spr

,	Atlantic

0	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
I Tidal fresh marsh

Figure 2.1.1. Geomorphic Settings for the New York - Long Island Region. Source: Titus et al.
Section 2.2).	

vl.. JfealybuHi

r "

Atlantic
Ocean

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 2.1.2. 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
Bar

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

















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















¦

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

?

1

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



e

fc-N.

Pennsylvania^

New J e rs e y

' W

1 T ' t*

r i

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 ]

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

1

A a







v

&
*



.

Ut





Chesapeake
Bay

Atlantic
Ocean

Virginia

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



Chesapeake
Bay

rt1



Virginia

Atlantic
Ocean

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 ]

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

Atlantic
Ocean

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

?

1

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

> X

x

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

Virginia

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 ]

A *

Will Wetlands Be Converted to Open Water?

Rate of
Sea Level Rise







¦









Current rate

Yes

?

?

No

No

No

IMo

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 ]

Geomorphic Setting

Back barrier iagoon, other

Back barrier lagoon, flood tidal delta

Back barrier iagoon, lagoonal fill

Estuarine marsh

Estuarine, fringe

Estuarine, meander

Saline fringe

Tidal fresh forest

Tidal fresh marsh

Atlantic
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.

-------
References

Armentano, T.V. and G.M. Woodwell. 1975. Sedimentation rates in a Long Island

marsh determined by Pb-210 dating. Limnology and Oceanography 20(3): 452-456.

Armentano, T.V., R.A. Park, and C.L. Cloonan. 1988. Impacts on coastal wetlands throughout the
United States, p. 87-140. In Titus, J.G. (ed.), Greenhouse Effect, Sea Level Rise and Coastal
Wetlands. Environmental Protection Agency, Washington D.C.,

Aubrey D.G. and L. Weishar. 1998. Hydrodynamics and Sediment Dynamics of Tidal Inlets.
Springer-Verlag Publishing, New York.

Bartberger, C.E. 1976. Sediment sources and sedimentation rates, Chincoteague Bay, Maryland and

Virginia. Journal of Sedimentary Research 46: 326-336.

Bertness, M.D. 1999. The Ecology of Atlantic Shores. Sinauer Associates, Sunderland,

Massachusetts.

Bokuniewicz, H. 1980. Groundwater seepage into Great South Bay, New York. Estuarine and
Coastal Marine Science 10: 437-444.

Boumans, R.M. and J.W. Day Jr. 1993. High precision measurements of sediment elevation in
shallow coastal areas using a sedimentation-erosion table. Estuaries 16: 375-380.

Boumans, R.M. Ceroni, D. Burdick, D. Cahoon, and C. Swarth. 2002. Sediment elevation dynamics
in tidal marshes: Functional assessment of accretionary biofilters. CICEET Final Report for
the period of 8/15/1999 through 8/15/2002. Cooperative Institute for Coastal and Estuarine
Environmental Technology, Durham, New Hampshire.

Bricker-Urso, S., S.W. Nixon, J.K. Cochran, D.J. Hirschberg, and C. Hunt. 1989. Accretion rates
and sediment accumulation in Rhode Island salt marshes. Estuaries 12: 300-317.

Brickman, E. 1978. Cs-137 chronology in marsh and lake samples from Delaware. M.S. Thesis,
University of Delaware, Newark.

Brush, G.R., E.A. Martin, R.S. Defries, and C.A. Rice. 1982. Comparisons of 210Pb and pollen

methods for determining rates of estuarine sediment accumulation. Quaternary Research 18:
196-217.

Cademartori, E.A. 2000. An assessment of salt marsh vegetation changes in southern Stony Brook
Harbor: Implications for future management. M.A. thesis, State University of New York,
Stony Brook.

Cahoon, D.R. and R.E. Turner. 1989. Accretion and canal impacts in a rapidly subsiding wetland. II.
Feldspar marker horizon technique. Estuaries 12(4): 260-268.

Cahoon, D.R., J.C. Lynch, B.C. Perez, B. Segura, R.D. Holland, C. Stelly, G. Stephenson, and P.
Hensel. 2002. High-precision measurements of wetland sediment elevation: II. The Rod
Surface Elevation Table. Journal of Sedimentary Research 72(5): 734-739.

Cahoon D.R., P.F. Hensel, T. Spencer, D.J. Reed, K.L. McKee, andN. Saintilan. 2006. Coastal

wetland vulnerability to relative sea-level rise: Wetland elevation trends and process controls.
Pages 271-292 in J.T.A. Verhoeven, B. Beltman, R. Bobbink, and D. Whigham (eds.).
Wetlands and Natural Resource Management. Ecological Studies, Volume 190, Springer-
Verlag, Berlin and Heidelberg.

-------
[ 172 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]

Carey, W.L. 1996. Transgression of Delaware's fringing tidal marshes: Surficial morphology,

subsurface stratigraphy, vertical accretion rates and geometry of adjacent and antecedent
surfaces. Ph.D. dissertation, University of Delaware, Lewes.

Childers, D.L., F.H. Sklar, B. Darkes, and T. Jordan. 1993. Seasonal measurements of

sediment elevation in three Mid-Atlantic estuaries. Journal of Coastal Research 9(4): 986-
1003.

Church, T.M., C.J. Lord, III, and B.L.K. Somayajulu. 1981. Uranium, thorium and lead nuclides in a
Delaware salt marsh. Estuarine, Coastal and Shelf Science 13: 267-275.

Church, T.M., R.B. Biggs, and P. Sharma. 1987. The birth and death of salt marshes: Geochemical
evidence for sediment accumulation and erosion. EOS, Transactions, American Geophysical
Union Transactions 68(16): 305.

Chrzastowski, M.J. 1986. Stratigraphy and geologic history of a Holocene lagoon: Rehoboth Bay
and Indian River Bay, Delaware. Ph.D. dissertation, University of Delaware, Newark.

Clark, J.S. and W.A. Patterson, III. 1985. The development of tidal marsh: upland and oceanic
influences. Ecological Monographs 55(2): 189-217.

Cochran, J.K., D.J. Hirshberg, J. Wang, and C. Dere. 1998. Atmospheric deposition of metals to
coastal waters (Long Island Sound, New York, USA): Evidence from saltmarsh deposits.
Estuarine, Coastal and Shelf Science 46: 503-522.

Darke, A.K. and J.P. Megonigal. 2003. Control of sediment deposition rates in two mid-Atlantic
coast tidal freshwater wetlands. Estuarine, Coastal and Shelf Science 57: 255-268.

DeLaune, R. D., J. A. Nyman, and W. H. Patrick, Jr. 1994. Peat collapse, ponding and wetland loss
in a rapidly submerging coastal marsh. Journal of Coastal Research 10:1021-1030.

Donnelly, J.P., S.S. Bryant, J. Butler, J. Dowling, L. Fan, N. Hausmann, P. Newby, B. Shuman, J.
Stern, K. Westover, and T. Webb. 2001. 700 yr sedimentary record of intense hurricane
landfalls in southern New England. GSA Bulletin 113: 714-727.

Douglas, P.G. 1985. Evolution of a brackish estuarine marsh system in the Pocomoke River Estuary.
M.A. thesis, University of Maryland, College Park.

Erwin, R.M., D.R. Cahoon, D.J. Prosser, G.M. Sanders, and P. Hensel. 2006. Surface elevation
dynamics in vegetates Spartina marshes versus unvegetated tidal ponds along the Mid-
Atlantic coast, USA, with implications to waterbirds. Estuaries and Coasts 29(1): 96-106.

Flessa, K.W., K.J. Constantine, and M.K. Cushman. 1977. Sedimentation rates in a coastal marsh
determined from historical records. Chesapeake Science 18(2): 172-176.

Fletcher, C.H., III, H.J. Knebel, and J.C. Kraft. 1990. Holocene evolution of an estuarine coast and
tidal wetlands. Geological Society of America Bulletin 102: 283-297.

Fletcher, C.H., III, J.E. Van Pelt, G.S. Brush, and J. Sherman. 1993. Tidal wetland record of

Holocene sea-level movements and climate history. Palaeogeography, Palaeoclimatology,
Palaeoecology 102: 177-213.

Ford, M.A. and J. B. Grace. 1998. Effects of vertebrate herbivores on soil processes, plant biomass,
litter accumulation and soil elevation changes in a coastal marsh Journal of Ecology 86: 974-
982.

Gornitz, V., S. Couch, and E.K. Hartig. 2002. Impacts of sea level rise in the New York City
metropolitan area. Global and Planetary Changes 32: 61-88.

Hartig, 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(1): 71-89.

Kahn, H. and G.S. Brush. 1994. Nutrient and metal accumulation in a freshwater tidal marsh.
Estuaries 17(2): 345-360.

Khalequzzaman, M. 1989. Nature of sedimentary deposition in a salt marsh: Port Mahon, DE. M.S.
thesis, University of Delaware, Newark.

Kearney, M.S. and L.G. Ward. 1986. Accretion rates in brackish marshes of a Chesapeake Bay
estuarine tributary. Geo-Marine Letters 6: 41-49.

-------
[ SECTION 2.1 173 ]

Kearney, M.S. and J.C. Stevenson. 1991. Island land loss and marsh vertical accretion rate evidence
for historical sea-level changes in Chesapeake Bay. Journal of Coastal Research 7(2): 403-
415.

Kolker, A.S. 2005. The impacts of climate variability and anthropogenic activities on salt marsh
accretion and loss on Long Island. Ph.D. thesis, Stony Brook University, Stony Brook.

Kraft, J.C., M.J. Chrzastowski, S.M. Stedman, and Hi-Il Yi. 1989. Sedimentation rates in coastal
marshes as indicators of relative sea level rise. International Geological Congress, 28th,
Washington, D.C., vol. 2: 220-221.

Kraft, J.C., Hi-Il Yi, and M. Khalequzzaman. 1992. Geologic and human factors in the decline of the
tidal salt marsh lithosome: The Delaware estuary and Atlantic coastal zone. Sedimentary
Geology 80: 233-246.

Krone, R.B. 1987. A method for simulating historic marsh elevations. Coastal Sediments 87 (1):
316-323.

Lord, J.C. 1980. The chemistry and cycling of iron, manganese and sulfur in salt marsh sediments.
Ph.D. thesis, University of Delaware, Newark.

Lynch, J.C., J. R. Meriwether, B. A. McKee, F. Vera-Herrera and R. R. Twilley. 1989. Recent

13n	210

accretion in mangrove ecosystems based on Cs and Pb Estuaries 12: 284-299.

Morris, J.T., P.V. Sundareshwar, C.T. Nietch, B. Kjerfve, and D.R. Cahoon. 2002. Response of
coastal wetlands to rising sea level. Ecology 83(10): 2869-2877.

Muzyka, L.J. 1976. Pb-210 chronology in a core from the Flax Pond marsh, Long Island. M.S.
thesis, State University of New York and Stony Brook University, Stony Brook.

National Research Council. 2004. River basins and coastal systems planning within the US Army
Corps of Engineers. National Academies Press, Washington, D.C.

Nikitina, D.L., J.E. Pizzuto, R.A. Schwimmer, and K.W. Ramsey. 2000. An updated Holocene sea-
level curve for the Delaware coast. Marine Geology 171: 7-20.

Nyman, J. A., R. D. DeLaune, H.H. Roberts, and W.H. Patrick, Jr. 1993. Relationship between
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
salt marsh. Estuaries 1(1): 29-35.

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.

-------
[ 174 MAPS THAT DEPICT SITE-SPECIFIC SCENARIOS FOR WETLAND ACCRETION ]

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
in the Mississippi River Delta. Estuaries 25(5): 985-998.

Scavia, D., J.C. Field, D F. Boesch, R. W. Buddemeier, V. Burkett, D. R. Cayan, M. Fogarty, M.A.
Harwell, R. W. Howarth, C. Mason, D. J. Reed, T. C. Royer, A. H. Sallenger, and J. G. Titus.
2002. Climate change impacts on U.S. coastal and marine ecosystems. Estuaries 25:149-164.

Schwimmer, R. A. and J.E. Pizzuto. 2000. A model for the evolution of marsh shorelines. Journal of
Sedimentary Research 70(5): 1026-1035.

Silliman, B.R. and J.C. Zieman. 2001. Top-down control on Spartina alterniflora production by
periwinkle grazing in a Virginia salt marsh. Ecology 82(10): 2830-2845.

Stearns, L.A. and D. MacCreary. 1957. The case of the vanishing brick dust contribution to
knowledge of marsh development. Mosquito News 17: 303-304.

Stevenson, J.C., L.G. Ward, and M.S. Kearney. 1986. Vertical accretion in marshes with varying
rates of sea level rise. p. 241-259 in Wolfe, D.A. (ed.), Estuarine Variability. Academic
Press, New York.

Stevenson, J.C., L.G. Ward, and M.S. Kearney. 1988. Sediment transport and trapping in marsh
systems: Implications of tidal flux studies. Marine Geology 80: 37-59.

Stevenson, J.C., M.S. Kearney, and E.C. Pendleton. 1985. Sedimentation and erosion in a
Chesapeake Bay brackish marsh system. Marine Geology 67: 213-235.

Stevenson, J.C. and M.S. Kearney. 1996. Shoreline dynamics on the windward and leeward shores
of a large temperate estuary, p. 233-259 in K.F. Nordstrom and C.T. Roman, (eds.).
Estuarine Shores: Evolution, Environments, and Human Alterations. John Wiley and Sons
Ltd., Chichester, England.

Stumpf, R.P. 1983. The process of sedimentation on the surface of a salt marsh. Estuarine, Coastal
and Shelf Science 17: 495-508.

Ward, 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.

Webster, P.J., G.J. Holland, J.A. Curry, and H.R. Chang. 2005. Changes in tropical cyclone number,
duration, and intensity in a warming environment. Science 309: 1844-1846.

Wood, M.E., J. T. Kelley, and D. F. Belknap. 1989. Patterns of sediment accumulation in the tidal
marshes of Maine. Estuaries 12: 237-246

Woodroffe, C.D. 2002. Coasts: Form, process and evolution. Cambridge University Press,
Cambridge, U.K.

Zeppie, C.R. 1977. Vertical profiles and sedimentation rates of CD, CR, Cu, Ni, and Pb in Jamaica
Bay, New York. M.S. thesis, State University of New York, Stony Brook.

-------