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Assessment of Impacts
on Nauset Barrier Beach
and Pleasant Bay
Sea Level Rise:
This report was prepared for
the Pleasant Bay Alliance
by the Center for Coastal
Studies of Provincetown
1
Preamble from Pleasant Bay Alliance
Pleasant Bay is a 9,000-acre estuary located in the Towns of
Orleans, Chatham, Harwich and Brewster, Massachusetts. Due
to its unique and extensive environmental values, the Bay and its
surrounding shoreline and connected wetlands were designated by
the Commonwealth as an Area of Critical Environmental Concern
(ACEC). The four towns that share the ACEC and Pleasant Bay
watershed collaborated in developing a resource management plan
for those areas, and formed an inter-municipal organization, the
Pleasant Bay Alliance, to oversee implementation of plan.
Pleasant Bay provides nursery areas and habitat for a wide variety
of fish, shellfish and other aquatic animals that make up the food
chain for sustainable fisheries. The expansive marshes, beaches
and tidal flats of the inner shoreline and outer beach provide food
and habitat for shorebirds, migratory waterfowl and other terres-
trial animals. The vitality and diversity of these resources rely on
the coastal processes of tides, wind, waves and erosion that trans-
port sediment and tidal waters throughout the system. The coastal
landforms themselves provide other ecosystem services by helping
to filter pollutants from run-off, providing flood and storm dam-
age prevention and, in the case of salt marsh, absorbing carbon
and other toxins that otherwise contribute to global warming.
The management plan recognizes the vital role of natural coastal
shoreline processes in a healthy estuary. The Alliance regularly
monitors changes in the inner and outer shoreline through tide
gage monitoring, aerial imagery, and periodic assessments of those
and other data sources with historic trends. The management
plan also identifies the need for an assessment of potential chang-
es in the Nauset barrier beach system and the Pleasant Bay inner
shoreline and intertidal zone due to sea level rise. The potential
change in sea level, coupled with increased potential for storm
surge, could have significant effects such as loss of coastal habi-
tat and resources, increased coastal erosion, loss of recreational
resources such as beaches and landings, loss of public and private
property and infrastructure, salt-water intrusion into wells and
septic systems, elevated storm surge levels, and more frequent
coastal inundation.
As a first step, the Alliance commissioned this study to (1)
estimate the likely range of sea level rise in the vicinity of the
barrier beach and inner shoreline; and (2) identify and quantify
and characterize potential changes in the Nauset Barrier Beach
and inner shoreline and intertidal zone of Pleasant Bay resulting
from estimated changes in sea level. This information will provide
an important foundation on which to begin to assess potential
impacts to resources and infrastructure, and then develop manage-
ment strategies and policies to address the challenges associated
with sea level rise.
By assessing the system’s response to sea level rise, this study also
examines the role of natural sediment transport processes in the
protection of waterfront property and the preservation of coastal
resources and the values they provide, including habitat, pollu-
tion attenuation, and coastal storm resiliency. Hardening of the
shoreline, while intended to help stem the process of erosion, may
actually worsen the problem.
1
Acknowledgements
This report was prepared for the Pleasant Bay Alliance by the
Center for Coastal Studies of Provincetown:
Mark Borrelli, Ph.D.
Graham Giese, Ph.D.
Steve Mague
Bryan Legare
Theresa Smith
John Ramsey, P.E., M.C.E., Applied Coastal Research and Engineering, Inc.
Preamble from Pleasant Bay Alliance 1
1 Introduction and Executive Summary 2
2 Sea Level Rise: The Nauset Barrier Beach and
Pleasant Bay 2
Past and Present Regional Sea Level Change 2
Past and Projected Global Sea Level Change 3
Projected Regional Sea Level Change for
the 21st Century 4
Factors Influencing Estimates 5
3 Geomorphological Changes in the Barrier
Beach and Inlet System 6
4 Future Geomorphological Changes on the
Inner Shoreline 16
Shoreline Protection Structures and Sea Level
Rise in Pleasant Bay 17
5 Conclusions 19
6 Glossary 20
References 20
The following members of the Peasant Bay Alliance Coastal
Processes Work Group contributed to this report:
Greg Berman, Coastal Resources Specialist, Woods Hole Sea Grant and
Cape Cod Cooperative Extension
Judith Bruce, Pleasant Bay Alliance Steering Committee (Orleans)
George Cooper (Chatham)
Jane Harris, Pleasant Bay Alliance Steering Committee member (Chatham)
Ted Keon, Director, Coastal Resources Department, Town of Chatham
Fran McClennen, Pleasant Bay Alliance Steering Committee (Orleans)
Stephen McKenna, Massachusetts Coastal Zone Management
Chris Miller, Director, Natural Resources Department, Town of Brewster
Carole Ridley, Coordinator, Pleasant Bay Alliance
Amy Usowski, Conservation Administrator, Town of Harwich
Table of Contents
2
1Introduction & Executive
Summary
2
Sea level Rise: The Nauset
Barrier Beach & Pleasant Bay
This chapter examines the anticipated rate of sea
level rise for the region encompassing Pleasant Bay
and the Nauset Barrier Beach.
Regional sea level is a critical factor in assessing the
sustainability of our coastal resources.
Regional sea level has risen approximately 1 foot
over the past century, the highest rate of sea level
rise in almost 3,000 years.
In 2013 the Intergovernmental Panel on Climate
Change (IPCC) estimated a range of possible increas-
es to regional sea level rise in New York City. This
measure of regional sea level also applies through-
out southern New England.
An intermediate estimate of regional sea level
ranges from an increase of .01 ft per year to .03 ft/yr.
This value can be used to estimate local sea level for
the Nauset Beach/Pleasant Bay region by applying
the regional sea level increase to local tide measure-
ments. The resulting increase in tide in the Pleasant
Bay/Nauset region is 1.2 to 2.9 ft by 2100.
Ocean thermal expansion and glacier melting, which
are byproducts of increases in greenhouse gasses,
account for the major part of sea level rise accelera-
tion.
Past and Present Regional Sea Level Change
The water’s edge is one of our planet’s most dynamic
environments. Tidal flats, beaches, marshes, bluffs and
dunes are all finely tuned to the levels of the tides, and
as sea level changes, so do these coastal habitats and land-
forms. Geological processes driven by waves, winds and
tides contribute to coastal change, but sea level provides
the stage upon which these processes play. For example,
in discussing barrier island migration, Berman (2015)
illustrates how landward movement of barrier beaches is
ultimately a response to rising sea level, regardless of the
more immediate mechanism of change such as tidal inlet
formation or storm wave overwash. Thus, in setting out
to assess the impacts due to sea level rise on the shoreline
of Nauset Beach and Pleasant Bay, it is essential to estab-
lish—to the extent possible—the expected behavior of
sea level in the region of New England and Pleasant Bay.
When we speak of regional sea level, it is important to
remember that we are speaking of relative sea level, that is
to say the level of the sea surface with respect to level of
the local land surface. The land surface of southern New
England is undergoing long-term subsidence, or sinking,
so both subsideneand a rising sea surface contribute to
what we refer to as “sea level rise” in the region.
This study assesses the impacts of sea level rise on coastal
resources found on the inner shoreline of Pleasant Bay and the
portion of the Nauset Barrier Beach fronting Pleasant Bay. As
described in detail below, the study finds that the impacts to
coastal resources resulting from sea level rise are considerable,
but vary depending on the estimated range of sea level rise that
is expected to occur.
Using established models and best available climate science
data, three sea level rise scenarios (low, mid and high) were
developed for this study. These are conservative estimates of
projected sea level rise for Nauset Beach/Pleasant Bay and range
from one to three feet over the next 100 years. This magnitude
of sea level rise would increase tide levels in Pleasant Bay by 1.2
to 2.9 ft by 2100.
Regional sea level is a critical factor in assess-
ing the sustainability of our coastal resources. By comparison,
regional sea level has risen approximately 1 ft over the past
century, the highest rate of sea level rise in almost 3,000 years.
Under any projected sea level rise scenario outlined in this
study, the barrier beach and inlet system will remain intact,
but with a different configuration and rate of inlet formation
and evolution than has been exhibited over the past 150 years.
Low-lying barrier beach areas will experience more overwash
(typically during storms) with sediment being deposited in the
back-barrier (bayside) environment. This is a vital process that
allows the barrier to keep pace with rising sea levels. Wider
areas of the Nauset Beach would be expected to experience a
loss of ocean-side beach and intertidal zones resulting in lower
dune heights.
Pleasant Bay may lose a quarter to a half of its 392 acres of
landside intertidal resource area through the end of the century
under the low (1ft/century) and mid (2ft/century) level rise
scenarios, respectively.
Intertidal coastal resources provide
a variety of ecosystem services, include storm attenuation,
pollution filtration and habitat. Public access, and low-lying
infrastructure and property also would be adversely affected
under any sea level rise scenario. Under the highest scenario,
coastal intertidal resources would increase due to inundation
of current upland areas. Installation of Coastal Engineering
Structures to prevent the inland retreat of intertidal resources,
such as salt marsh and tidal flats would lower the elevation
of an eroding beach by denying sediment input and reflecting
wave energy which increases the rates of erosion along the
front and downdrift areas adjacent to these structures.
The assessment of sea level rise impacts to the barrier beach/
inlet system and landside intertidal resources of Pleasant Bay
provides a foundation for further study of specific impacts
to natural resources, public access and public and private
infrastructure and, subsequently, development of management
strategies.
Thanks to the availability of tide records, the regional
sea level history in southern New England during the
20th century is fairly clear. The NOAA tide record for
Boston (Figure 1), which extends back almost 100 years,
indicates a sea level rise trend of 2.8 mm per year (equiv-
alent to about 1 foot per century). A similar rate of rise
is shown by the even longer record for New York City
(Figure 2). However, these recent rates represent a decided
departure from regional sea level change rates in the past.
Geological studies in southern New England (Donnelly
et al., 2004) indicate that for many centuries prior to the
mid-19th century, regional sea levels rose at a significantly
slower rate. A similar acceleration beginning in the 19th
century has been noted in global sea level; a recent study
by Kopp, et al. (2016) reports that 20th century global
sea level rose faster than during any of the previous 27
centuries.
Past and Projected Global Sea Level Change
While sustainability of local coastal resources is tied direct-
ly to regional and localsea level, the processes responsible
for our regional as well as global sea level acceleration
are global in nature. These processes, largely resulting
from anthropogenic global warming, are discussed in the
most recent (fifth) assessment of global climate change
published by the International Panel on Climate Change
(IPCC, 2013). Results from numerical models— “pro-
cess-based” models incorporating both natural processes
and anthropogenic increases in greenhouse gasses and
aerosols—indicate that ocean thermal expansion and
glacier melting account for the major part of the observed
sea level acceleration (Church, et al., 2013). The pro-
cess-based models also have been applied to project future
sea levels, both global sea levels and regional sea levels.
3
Figure 1. Monthly mean sea level at Boston (with the annual signal removed). The NOAA tide station data begin in 1921. The
long-term mean sea level trend is 0.109 inches per year or 0.92 feet per century.
Figure 2. Monthly mean sea level at New York City (with the annual signal removed). The NOAA tide station data begin in 1856.
The long-term mean sea level trend is 0.111 inches per year or 0.93 feet per century.
The IPCC projections of 21st century global sea level
change are shown in Figure 3 together with specific
range estimates associated with two possible scenari-
os for greenhouse gas emissions inputs, referred to as
“pathways”. Only two of four scenarios, low and high,
are shown. Since this figure represents a global average,
it necessarily differs from the individual regional projec-
tions which reflect differing contributions due to regional
climate modes, ocean dynamical processes, movements of
the lithosphere, and changes in gravity due to water/ice
mass redistribution (Church et al., 2013). 1
Projected Regional Sea Level Change for the 21st
Century
Benefiting from recent advancements, the fifth assessment
of global climate change includes, for the first time, 21st
century regional sea level change projections —projections
have been made for nine representative coastal locations
for which long tide records are available. One of those
locations is New York City (NYC) and the IPCC projec-
tion for New York is shown in Figure 4. At the right hand
margin of the figure are four colored vertical bars showing
the range of NYC sea level projections for the year 2100
obtained from four groups of models, each using different
input “pathways” for greenhouse gas emissions inputs.
The projections for “low” input emissions are shown in
dark blue, those for “low-intermediate” inputs in light
blue, those for “high-intermediate” inputs in orange, and
those for “high” inputs in red.
4
Figure 3. Projected global mean sea level rise over the 21st
century from the IPCC fifth assessment of global climate
change. Shaded areas show the likely ranges for the low input
(blue) and high input (red) greenhouse gas emission pathways.
The heavy blue and red lines indicate the median value of each
range. Figure source: Church, et al., 2013. Figure 4. Observed and projected relative mean sea level
change for New York City relative to MSL for 2000. Tide
gauge record (since 1970) shown in brown. Shaded area
indicates spread (5% to 95%) of results of 21 models using
low-intermediate input “pathways.” The black line shows
the mean of the results. Vertical colored bars show 2100
MSL projections (5%, mean, 95%) of four groups of models
with different input “pathways”: low input (dark blue);
low-intermediate input (light blue); high-intermediate input
(orange); and high input (red). Figure adapted from Church,
et al. (2013).
The grey, triangular shaded area in Figure 4 shows the
spread of NYC sea level change projection results from the
“low-intermediate” inputs group of models throughout the
21st century. The results of this group are reasonably similar
to, and intermediate between, the results of the “low” in-
puts and “high-intermediate” inputs groups of models. The
“high” inputs group results are not included because those
projections result from the highest greenhouse gas emis-
sion pathways in the absence of climate change policies-
such as those included in the Paris Climate Agreement of
December, 2015. Figure 4 indicates a likely rise of regional
sea level by 2100, relative to the 2000 level, from a low of
about 1.0 ft (0.3 m) to a high of about 3.0 ft (0.9 m). The
mean projected rise is approximately 2.0 ft (0.6 m).
Because the geophysical processes responsible for sea
level changes for New York City are common to the entire
southern New England/New York region, they will provide
the basis for our assessment of impacts due to sea level
rise on the Nauset Barrier Beach and inlet system (Task
2) and on the inner shoreline of Pleasant Bay (Task 3).
Noting the linearity of the regional estimates in Figure 4,
we annualize the IPCC results to project three 21st century
sea level rise rates for the Pleasant Bay/Nauset Beach study
area: a “low” rate of 0.01 ft/year (3 mm/year), a “mid” rate
of 0.02 ft/year (6 mm/year), and a “high” rate of 0.03 ft/
year (9 mm/year). The following table (Table 1) illustrates
those rates applied to the contemporary (2015) annual
1 It should be noted that these projected global sea level changes differ from,
and are less extreme than, those presented in “Sea Level Rise: Understanding
and Applying Trends and Future Scenarios for Analysis and Planning” (Massachu-
setts CZM, 2013). Drawing from contemporary technical information, including
the then most recent (fourth) assessment of global climate change published by
the International Panel on Climate Change (IPCC, 2007), that report presented
projections of global and regional sea level change based on the most advanced
research then available. Section 13.1.1 of the fifth assessment discusses the
advancements since the fourth assessment that have led to revised projections
such as those illustrated in Figure 3.
2040 0.20 m (0.7 ft) 0.28m (0.5 ft) 0.35m (1.1 ft)
2070 0.29 m (1.0 ft) 0.46m (1.5 ft) 0.62m (2.0 ft)
2100 0.38 m (1.2 ft) 0.64m (2.1 ft) 0.89m (2.9 ft)
YEAR LOW (3 mm/yr) MID (6 mm/yr) HIGH (9 mm/yr)
Estimated Mean Sea Level in Nauset Beach/Pleasant Bay
under Low, Mid and High SLR Scenarios.
Table1. Projected future annual mean sea levels (NAVD88) for
the Nauset Beach/Pleasant Bay region for three representative
years. Levels were calculated for three different rates of MSL
rise (“low”, 3 mm/yr; “mid”, 6 mm/yr; “high”, 9 mm/yr) for
the southern New England/New York region based on Church,
et al. (2013) mean sea levelprojections for New York City.
Local sea level within individual harbors and bays will differ
from the regional, or “outside”, level (see text above).
mean sea level elevation at Chatham Fish Pier, 0.43 ft
(0.13 m) NAVD88. It must be noted that while these
regional sea level rise projections apply to the coastal
waters of the southern New England/New York region,
local sea level within individual systems such as bays and
harbors will differ due to local circumstances and events.
For example, tidal channel shoaling that elevates low
tide levels, but not high tide levels, will result in local
increased mean sea level.
Factors Influencing Estimates
Local sea level change in the Pleasant Bay area during
the 21st century will be determined primarily by the rate
of warming of the global climate system and by the rate
of crustal subsidence. Crustal subsidence in our region
results from a global process known as “glacial isostatic
adjustment” (GIA), whereby our planet’s crust under-
goes both uplift and subsidence in different regions as it
adjusts to past glacial loading. The GIA contribution to
southern New England sea level rise has been estimated
to account for between 33–50% of the observed local
mean sea level rise of 3mm/yr (e.g., Engelhart, 2010).
In contrast, the future contributions to regional sea level
rise due to global warming will be affected by societal
responses to the warming, and may well increase over
the next few centuries (see, for example, Figure 3).
Therefore, despite the linearity of the 21st century sea
level change projections for the southern New England/
New York region indicated in Figure 4 and utilized for
this study (e.g., Table 1), it is important to bear in mind
that over extended time periods the contribution to
regional sea level rise due to global warming is expected
to increase, producing an increasing rate of regional sea
level rise.
Regional sea level rise projections are influenced not only
by uncertainties related to changes in global climate, but
also to uncertainties related to regional geophysical re-
sponses to global climate change. For example, extensive
collapse of ice shelves on the Antarctic Peninsula could
lead to higher sea levels than presently projected. Closer
to home, future changes in the distribution of global sea
level rise throughout the oceans could affect regional
sea levels, and regional changes in storm frequency and
intensity could affect tidal inlets which, in turn, could
affect sea levels as described above.
5
Figure 5. Pleasant Bay and the Nauset Barrier Beach System
3
Geomorphological Changes
in the Barrier Beach & Inlet
System
This chapter estimates changes in the Nauset Barri-
er Beach and Inlet system resulting from potential
sea level rise scenarios.
Nauset Barrier Beach and Inlet system currently
evolves through a 150-year cycle of a tide-dom-
inated inlet development phase followed by a
wave-dominated inlet migration phase.
The 150-year cycle will remain intact under the
current rate of sea level rise of 1 ft per century.
However, if the rate of sea level rise increases, as
anticipated, the 150-cycle will be shortened, and
the barrier island will migrate, or move, toward the
mainland (westward) more quickly.
Under any projected sea level rise scenario, the
barrier beach and inlet system will remain intact,
but with a different configuration. Low-lying
barrier beach areas will experience more overwash
with sediment being deposited in the back-barrier
(bayside) environment. In wide areas, where some
storm waves cannot completely washover the
barrier into the bay, a loss of ocean-side beach and
intertidal zones would likely occur along with a
resultant lowering of dune heights.
Narrow, low-lying barriers slowly migrate landward
as sediment is eroded from the ocean side shore-
line, typically during storms, washes over the island
and is deposited on the bayside shoreline. This is
one of the ways barrier islands can keep pace with
sea level rise.
6
Callout Box 1. Updrift
and downdrift are similar
to upriver and downriver.
There is a direction of net
movement of sediment
along any stretch of
shoreline for a given year,
though sand can move
as the wind and wave
directions change. Along
the Nauset Barrier beach
that direction is from
North to South.
Changes along the Nauset Barrier Beach System, particu-
larly the open ocean shoreline, are
driven by coastal pro-
cesses (storms, winds, waves, tides, etc.) in conjunction
with sea level rise. Estimates of future barrier beach config-
urations can be developed by quantitatively analyzing past
cycles of tidal inlet development and evolution (Giese et
al., 2009), projecting past and current three-dimensional
barrier beach configurations into the future and coupling
them with anticipated rates of sea level rise.
The Nauset Barrier Beach System is an interconnected
configuration of barrier islands and barrier spits (Figure
5). Different forces are at work in shaping the portions of
the barrier beach system updrift and downdrift (callout
box 1) of the North Inlet formed in 2007. Sea level rise
and coastal processes (storms, winds, waves, tides, etc.)
are the main drivers of change along the barrier beach
updrift of the North Inlet. Change along the barrier
beach downdrift of the North Inlet is primarily caused by
tidal inlet processes, with sea level rise playing a lesser
role in the short-term. Tidal inlet processes are related to
the semi-diurnal (twice
daily) tides that move in and out
of the tidal inlets in Pleasant Bay. Sand being carried along
the
open ocean shoreline either enters the inlet, bypasses
the inlet and moves downdrift or is incorporated into a
nearshore bar in and/or around the inlet. This sand is car-
ried by waves and tidal currents and can have a significant
influence on tidal inlet evolution.
The evolution of Nauset Beach has been documented as
occurring in a 150-year cycle (Giese et al., 1988) as shown
in Figure 6. Nauset Beach will lengthen as wave-trans-
ported material arrives from the north. As an
inlet
moves
further south, the water’s path from the open ocean to
Pleasant Bay will
become more circuitous and inefficient.
Over time, given the right conditions a storm will open a
new inlet and the cycle will repeat itself. Immediately after
this point Pleasant Bar will have two inlets as it does at the
time of this writing. If the rate of sea level rise seen during
most of the 20th Century (~1 ft/century) continues, the
150-year cycle will remain relatively intact (Figure 78?).
2
An increase in the rate of sea level rise would be expected
to alter the cycle of barrier beach and inlet development, as
described below.
Based in part on analysis of historical cross sections of
Nauset Beach done for the study area (Figure 8), relation-
ships between the rate of sea level rise and barrier evolu-
tion were developed for the Nauset Barrier Beach System
to estimate changes to the rate of landward migration of
Nauset Barrier Beach and the inlet cycle time scale. Using
the results of Figure 7 and those of the Massachusetts
7
Figure 7. Time series for the ‘low’ sea level rise scenario (1 ft/century). The accretion around Minister’s Point is basedon past shoreline
configurations seen in this area (Giese, 1988) as well as anticipated changes to the tidal inlet. The material is largely removed by 2070
as the inlet migrates south less material is brought into the system and relatively consistent tidal currents will likely remove that material.
This pattern is continued through 2100, though the Chatham Harbor area will likely start to see some deposition (shoaling) past 2100
due to the increasing inefficiency of the inlet as a result of increasing spit length. This figure is focused on the changes to the barrier,
which is to the right of the vertical dashed line. Changes to the inner shoreline will likely occur, but are not represented here.
Figure 6. Historical changes in the Nauset Beach-Monomoy barrier system. From Giese, 1988. It is provided here to give historical
context to the predictions of future shoreline positions.
8
Figure 8. Barrier Beach Cross Sections. The above cross sections were taken from profiles collected in 1888 (Marindin, 1890),
topographic and hydrographic surveys conducted in Pleasant Bay in the 1940-50s and the topographic/bathymetric lidar collected
by the US Army Corps of Engineers in 2010. Dotted lines in profiles represent extrapolated data estimated by the authors.
9
Coastal Zone Management’s (CZM) Shoreline Change
Project, the long- term retreat rate for the barrier beach
north of the inlet was determined to be approximately 4.5
feet/year (1.3 m/yr). Interestingly, in the later part of the
19th century Henry Mitchell, of the U.S. Coast Survey,
determined that the southerly section of the barrier beach
was then migrating west at a rate of approximately 4 feet/
year (1.2 m/yr) (Marindin, 1890; Mitchell, 1871, 1873).
Based on the above analysis, and assuming a simplified
yet widely accepted linear relationship between coastal
retreat and sea level rise, rates of 4.5 feet/year (1.3 m/yr),
9 feet/year (2.7 m/yr), and 13.5 feet/ year (4.1 m/yr) were
calculated for the “low”, “mid”, and “high” scenarios
developed in Task 1.
Recognizing that the time scale will be accelerated in
response to sea level rise, the durationd of the inlet cycle
was adjusted to reflect the “low”, “mid”, and “high”
scenarios developed in Task 1. Although a linear relation-
ship with sea level rise and coastal retreat was assumed
above, a nonlinear relationship in which the time scale
was adjusted by factors of 1, 2, and 3 was determined to
best fit potential inlet cycle scenarios. Application of this
relationship yields inlet cycle estimates of 150 years (the
present or “low” scenario), 100 years (the “mid” scenar-
io), and 75 years (the “high” scenario) (callout box 2),
illustrating the shortened cycle of inlet evolution in the
Nauset Barrier Beach System.
Figure 9 depicts a time series estimate of the “mid” sea
level rise scenario where the rate of sea level rise is 2ft/
century and the cycle shortens to approximately 100
years. North of the inlet(s) barrier widths will vary de-
pending on pre-existing conditions, i.e. narrow, low-lying
areas will experience more frequent overwash (assuming
other variables remain unchanged) and more deposition
in the backbarrier environment, which may help these ar-
eas keep pace with sea level rise for a period of time. Con-
versely, wider areas will have less beach (intertidal and
supra-tidal areas) which will result in less wind-blown
sand and lower dunes. Again, overwash can be expected;
although this overwash will likely not be deposited on the
backbarrier shoreline as it would be unlikely for the water
1 The cycle can be influenced by human-induced changes that alter the system. Such changes could include placement of erosion control structures, large-scale
dredging and other alterations that may impact tidal currents or sediment transport. Any of these changes could alter the 150-year cycle in duration and inlet forma-
tion, migration, and evolution. Other changes such as storm frequency and intensity are important but outside the scope of this work.
Figure 9. Time series for the ‘mid’ sea level rise scenario (2 ft/century). This figure is focused on the changes to the barrier
shorleine, which is to the right of the vertical dashed line. Changes to the inner shoreline will likely occur, but are not represented
here.
10
Figure 10. Example of
overwash events at Pochet
Island. The white arrow
is provided to reference
change in washover fan
through time. This is also
one of the ways that
barrier islands keep pace
with sea level rise. When
overwash occurs the island
increases in elevation in
that area.
Callout Box 2. Coastal
retreat (linear) vs. Inlet
Evolution Cycle (nonlinear).
11
Figure 11 . Time series for the ‘high’ sea level rise scenario (3 ft/century). The longest extent of Nauset Spit occurs around
2070. Inlet formation near Minister’s Point will occur at some point in time between 2070 and 2100, likely closer to 2070 than
2100. This figure is focused on the changes to the barrier, which is to the right of the vertical dashed line. Changes to the inner
shoreline will likely occur, but are not represented here.
to flow across a wide sandy area. In time this could result
in the overall narrowing of barrier beach in these areas.
The steepness of these areas is a critical factor when
considering overwash, inundation and other processes
and changes driven by flowing water.
This cycle of barrier islands narrowing followed by over-
wash during storm events and back barrier deposition
and subsequent widening of the barrier is one way barrier
islands keep pace with sea level rise and is commonly
called “rollover” (Berman, 2015). This is actively oc-
curring along the Nauset Barrier Beach System in places
such as Pochet Island (Figure 10) and will prevent the
islands and spits from ‘drowning in place’ or disappearing
due to sea level rise. Increasing inundation has recently
been shown to aid certain salt marshes along backbarrier
shorelines in keeping pace with sea level rise provided
there is sufficient sediment supply (Kirwan et al., 2016).
It is likely with continued overwash much of the salt
marsh along the backbarrier shoreline in the Nauset
Barrier Beach System will keep pace with the rates of sea
level rise discussed herein. Fringing salt marsh along the
mainland shoreline however, will likely decrease as this
salt marsh has little place to migrate due to development,
infrastructure and shoreline hardening (Borrelli, 2009).
If the rate of the sea level rise accelerates to 3 ft/century
the cycle will take approximately 75 years to complete
(Figure 11). In this scenario it is possible that the 1987
southern inlet will close quickly, followed by rapid south-
ern migration of the single 2007 inlet and a new inlet
formation in approximately 2070. This would represent
an increasing dynamic system and the uncertainty asso-
ciated with future predictions on coastal evolution would
in turn increase accordingly.
Understanding that both sea-level rise and the barrier
beach geomorphology influence water levels within the
Chatham Harbor/Pleasant Bay system, it was critical to
assess the combined influence to provide the most accu-
rate prediction of future water level conditions within the
estuary. To accomplish this assessment, a previously de-
veloped model of flow characteristics within the Pleasant
Bay estuarine complex (Howes, et al., 2006) was updated
with the existing post-2007 breach information, as well
as a future sea level rise predictions presented previously,
where the estimated sea level rise of 1.2 feet (0.38 meters)
was added to the 2007 offshore tide. This estimate was
derived from the mid-range rate of 6 mm/year (~1/4 inch
per year) determined for Pleasant Bay, based on IPCC
(2013) projections for New York City. Figure 12 provides
12
Figure 12. Comparison of measured 2007 tide from offshore of Pleasant Bay during the model simulation duration, and the
projected 2070 tide, including the sea level rise estimate of 1.2 feet for the period between 2007 and 2070.
Figure 13. Comparison of tides at Chatham Harbor, for thee model scenarios, including 2004 pre-breach conditions, 2007 post-
breach conditions, and estimated 2070 system morphology with projected SLR.
13
Table 2. Wetland Resource Areas, Mainland
Pleasant Bay
Beach 71.3 18%
Salt Marsh 257.1 66%
Tidal Flat 63.9 16%
TOTAL 392.3 100%
TOTAL
PERCENT
RESOURCE
AREA
AREA
(ACRES) 2016 392.3 392.3 392.3
2040 323.1 -18% 362.7 -8% 345.3 -12%
2070 340.2 +5% 348.8 -4% 358.0 +4
2100 302.4 -9% 208.9 -40% 370.0 +3%
Total -23% -47% +6%
YEAR LOW % CHANGE MED % CHANGE HIGH %CHANGE
Table 3. Change in Acres of Intertidal Area under Low, Medium and High
SLR Scenarios
Figure 14. Impact of Coastal Structures. Upper Left: change in intertidal area along the mainland shoreline in Pleasant Bay by
2100. The present day intertidal zone (solid green) overlain by future estimated intertidal zones based on three sea level rise
scenarios: Upper Right: Low scenario (Yellow). Lower Left: mid-scenario (Orange). Lower Right: high-scenario (Red). Coastal
structures are highlighted in black. Note the relationship between the intertidal zone and the presence or absence of structures.
14
Figure 15. Example of changes to intertidal areas in subset of Pleasant
Bay based on different sea level rise scenarios
Callout Box 3. Approximate demarcation for this
study of inner shoreline and barrier shoreline.
YEAR LOW % CHANGE MED % CHANGE HIGH %CHANGE
a plot of the estimated upward shift in offshore
tidal elevations, assuming the anticipated increase
in mean sea level.
To simulate the influence of both the different
inlets (i.e. barrier beach geomorphology), as well
as sea level rise on water elevations within the
Pleasant Bay system, a series of model runs were
performed based on (a) different inlet configura-
tions, and (b) different offshore tidal elevations
associated with future sea level rise. Model runs
were made using the 2004 single inlet morphology,
the 2007 post-breach multiple (2) inlet morphol-
ogy following the creation of the North Inlet, and
the projected 2070 single inlet system configura-
tion including the anticipated 1.2 feet of additional
sea level rise.
Figure 13 illustrates the modeled tide ranges
for the three simulations. While the tidal range
(the difference between high tide and low tide)
for 2004 and 2070 is similar, both being single
inlets systems, the increased high tide (and low
tide) elevation is due to the increase in sea level
(Figure 12). As shown in Figure 13, the tide range
with the multiple inlet system (2007) is between
1.2 and 1.6 feet greater than with the single inlet
system in 2004 and 2070, respectively. In addition,
this recent multiple inlet system is responsible for
the approximate 0.5 foot increase in Mean High
Water elevation within Chatham Harbor after the
opening of the 2007 inlet. This recent increase
in tide range also corresponds to improved tidal
flushing within the Pleasant Bay system. Due to
the projected location of the inlet in 2070, it is
anticipated that the tide range will be significantly
15
reduced from the existing multiple inlet system and is
already showing a decreasing trend as measured by tide
range data (Legare and Giese, 2016). Mean High Water
can be anticipated to be approximately 0.7 feet higher in
Chatham Harbor than it was in 2007. It should be noted
that this increase in local Mean High Water is only about
60% of the increase in projected offshore sea levels by
2070.
The formation of new tidal inlets in Pleasant Bay is
dependent on many factors. Perhaps most important are
suitable topographic and bathymetric conditions neces-
sary for initial formation and subsequent maintenance
by natural processes. For example, an inlet would not
be able to form near Pochet Island because a suitable
basin of water of sufficient depth and/or volume in close
proximity to the backbarrier shoreline does not exist.
Typically, when a new inlet forms storm waves overwash
a barrier making a connection between the ocean and
bay. This happens occasionally at Pochet Island as can
be seen by the frequent overwash fans there (Figure 10).
However, for an inlet to stay open, water from the Bay
needs to flow back to the ocean and the water in this area
is not deep enough to sustain substantial “bay-to-ocean”
flow. In fact, one of the reasons inlets form just north of
Minister’s Points is due to the deeper waters in the areas
to the east and south of Strong Island.
The natural movement of sand, erosion and accretion, is
part of a cycle needed to sustain this system. With regard
to the natural resources in Pleasant Bay, erosion (and
accretion) is a natural phenomenon that is part of the
sediment transport process which is vital to the ability
of the system to evolve and keep pace with sea level rise.
Erosion in one area leads to accretion, and preservation
or creation of important coastal resources, in another. To-
ward that end, the policy of Cape Cod National Seashore
is to allow the natural process of erosion to take place
within park boundaries. The sediment that erodes from
the coastal bluffs and beaches to the north of the Nauset
Barrier Beach system is within park boundaries and will
help maintain the Nauset barrier fronting Pleasant Bay
up to and past 2100. If the erosion that takes place north
of the Nauset Barrier Beach system were prevented, the
width and elevation of the barrier would rapidly decrease
and its persistence into the near future would be in ques-
tion. Even preventing seemingly small amounts of erosion
along the bluffs within the Bay itself can have substantial
negative impacts when viewed cumulatively.
Figure 16: Stone revetment along the Pleasant Bay shoreline illustrating the loss of fronting beach, as passive erosion continues
beyond the limits of the structure.
16
4
Future Geomorphological
Changes to Intertidal Coastal
Resources in Pleasant Bay
The changes anticipated in Pleasant Bay along the
intertidal areas on the inner shoreline (callout box 3) as a
result of sea level rise can be illustrated by examining the
evolution of the intertidal zone through time. Here the
intertidal zone is defined as the area between Mean Low
Water and Mean High Water.
The intertidal zone contains significant coastal resources
such as salt marsh and intertidal flats that provide critical
ecosystem services. These services include storm dam-
age prevention, flood protection, shellfish habitat, and
juvenile finfish refuge and nursery. These areas are vital
habitat and feeding areas for many species of vertebrate
and invertebrate animals ranging from shellfish to finfish
and crabs to birds. Birds in particular, both local and
migratory, use these areas to feed, nurse and nest. Salt
marsh and eelgrass are critical areas for predator avoid-
ance, nurseries, as well as locking in sediment with root
matter to reduce erosion and attenuate (dampen) wave
energy. Salt marsh and eelgrass and other vegetation can
sequester toxins and also carbon that could otherwise
contribute to global CO2 levels further increasing global
warming. To a lesser degree unvegetated intertidal flats
themselves dampen wave energy that would reach the
shore thereby reducing coastal erosion.
Three sea level rise scenarios have been developed for
Pleasant Bay based on both global and regional sea level
rise projections. These three sea level rise scenarios (low,
medium and high) were then used to develop three
snapshots of the mainland shoreline within Pleasant Bay
in 2040, 2070 and 2100. First, the extent of the 2016
intertidal zone was documented based on data from
the Chatham tide gauge data and recent and ongoing
tidal studies commissioned by the Pleasant Bay Alliance
(Giese, 2012; Giese and Kennedy, 2015). These data were
used to develop an elevation for MHW and MLW and
the area between these elevations were extracted from
existing elevation data and represented spatially within
a GIS environment. The existing data layers for wetlands
resources for Pleasant Bay were downloaded from the
MassGIS website and were overlain onto the present day
intertidal zone. Resources in the intertidal zone were ex-
tracted based on general wetland category (Table 2). The
intertidal zone for 2016 was then altered to reflect chang-
es to the MHW and MLW based on the three sea level rise
scenarios developed for this study. The projected changes
represent the intertidal zone as a whole. Changes to
distinct resource types (such as beach, flats, salt marsh)
in the intertidal zone could not be determined due to
the uncertainty associated with how these resource types
would respond to not only increases in water levels, but
also the variable natural processes and human alterations
that would occur. However, the changes to the intertidal
zone in total were documented in several ways.
First, a three-dimensional data layer based on the 2016
intertidal zone was used to map the extent of the intertid-
al zone based on the present day topography of Pleasant
Bay and the 3 sea level rise scenarios for 2040, 2070 and
2100. Tabular data on four time periods were calculat-
ed: 2016, 2040, 2070 based on the above-mentioned
GIS data layers (Table 3). Interestingly, the changes in
intertidal zone along the mainland of Pleasant Bay vary
considerably (Figure 14), particularly from 2070 to 2100.
For instance, in the “low” scenario the intertidal zone
decreases by 18% in area from 2016 – 2040, but increases
5% from 2040 – 2070, while finally decreasing 9% from
2070 to 2100. The overall loss for the “low” scenario is
23% from 2016 – 2100.
The “mid” scenario sees the highest overall decrease in
intertidal zone from 2016 to 2100. The intertidal zone
decreases for all time periods for the “mid” scenario: 8%
from 2016 – 2040, 4% from 2040 – 2070, and 40% from
2070 to 2100. The “mid” scenario is the only scenario
where there is a steady decline in intertidal area.
The intertidal zone in the “high” scenario decreases by
12% in area from 2016 – 2040, but increases 4% to acres
from 2040 – 2070, and increases a further 3% from 2070
to 2100. The change from 2016 to 2100 for the “high”
scenario is an increase of 6% in intertidal area. This is
due to increasing inundation of areas heretofore not
reached by tidal waters (Figure 15). None of the scenarios
assume any alteration to the shoreline and/or inundation
prevention actions. It is likely that human intervention to
prevent future flooding of existing low lying upland areas
This section estimates the effects of sea level rise on
the landside intertidal resource areas of Pleasant
Bay.
Pleasant Bay today has approximately 392 acres of
intertidal coastal resources that provide a variety of
ecosystem services.
Pleasant Bay may lose a quarter to a half of its
intertidal resource areas through the end of the
century under the low and medium sea level rise
scenarios, respectively. The loss of intertidal areas is
exacerbated by the presence of Coastal Engineering
Structures which prevent the inland retreat of
intertidal resources, such as salt marsh and tidal
flats. Public access, and low-lying infrastructure and
property also would likely be adversely affected.
Under the high sea level rise scenario, and assuming
nothing is done to prevent inundation, the amount
of intertidal area increases 6% by 2100. This scenario
does not depict the preservation of existing intertid-
al areas, but rather represents the inundation of up-
land areas previously not within the intertidal zone.
17
may alter (lower) the predicted increase in intertidal areas
under the high sea level rise scenario.
Coastal Engineering Structures and Pleasant Bay
A natural shoreline undergoing long-term erosion in re-
sponse to a sediment deficit and/or sea-level rise will ex-
hibit landward migration of the high water line. This nat-
ural passive erosion process can be exacerbated by the
introduction of shoreline armoring (e.g. revetments and/
or seawalls), where the structure may prohibit material
from eroding from the upland, thereby increasing the sed-
iment deficit to both downdrift and fronting beaches. In
addition, if a revetment or seawall is constructed to halt
erosion, the shoreline becomes essentially fixed at that
location as sea level rises. As sea level rises, adjacent nat-
ural landforms (e.g. beaches, dunes, and coastal banks)
will continue to erode and retreat landward; therefore, the
coastal armoring creates an artificial headland. In these
cases, the typical effect is loss of beach and/or salt marsh
fronting the coastal armoring structure (see Figure 16 for
an example) as well as accelerating erosion along adjacent
shorelines due to wave focusing and sediment loss. Many
other types of structures and/or alternatives exist when
addressing coastal erosion, with differing levels of impact
and permanence (Berman, 2015).
Historically, stone revetments have been the primary form
of shore protection in Pleasant Bay. Stone revetments
can provide increased wave dissipation, reduced wave
overtopping, and increased storm protection. This storm
protection is not permanent because seawalls, and to a
lesser extent revetments, can cause accelerated lowering
of the fronting beach over time, which will eventually
destabilize these structures. This lowering of the beach
is caused by a lack of sediment input and increased wave
reflection of the vertical or steeply sloping face of the
structure relative to the natural beach. A lower beach
elevation results in waves breaking closer to the shoreline
with increased overtopping potential. Seawalls and revet-
ments only protect the land directly behind them. Figure
17 shows that if there is no shore armoring in place, the
eroding beach will move landward to maintain the width
of the beach. With a seawall or revetment in place, the
fronting beach becomes narrower with continued erosion,
as the beach cannot migrate landward due to the presence
of the seawall.
During normal wave and tide conditions, the waves may
run-up on the narrow fronting beach. However, as shown
in Figure 18, the waves break further inland during
higher water elevations that could be caused by episodic
storms conditions and/or the influence of sea-level rise.
Without sufficient beach width to dissipate the wave
energy, the waves will tend to overtop the seawall or
revetment and cause lowering of the fronting beach. This
beach lowering is due to the magnified erosion/scour
force of the waves as they reflect from the structure, and
to the deficiency of bank sediment protected by the wall
that otherwise could help replenish the fronting beach
(Silvester and Hsu, 1993).
Figure 17. Chronic beach erosion on unhardened shores (left) and with seawalls in place (right) (image credit: U.S. Army Corps of
Engineers).
Beach
loss
Seawall
Shoreline profile after retreat
Initial shore profile
Beach width
Seawall
Beach loss
Seawall
Initial shore profile
Beach width
Beach width
no change in beach width
Shoreline profile after retreat
Beaches on chronically eroding shores can main-
tain their natural width as they slowly retreat
landward.
Beach loss eventually occurs in front of a seawall
where there is chronic erosion.
Beach
loss
Seawall
Shoreline profile after retreat
Initial shore profile
Beach width
Seawall
Beach loss
Seawall
Initial shore profile
Beach width
Beach width
no change in beach width
Shoreline profile after retreat
18
Along an eroding shoreline, a seawall or revetment may
accelerate the erosion rates of adjacent beaches (USACE,
1984). Erosion in the form of scour along the entire
length of the structure including the ends or edges may
threaten the structure itself as erosion continues. While
the designed revetment may provide storm protection
to adjacent upland, the lack of high tide beach and low
sediment supply along much of the Pleasant Bay shore-
line will likely lower the profile in front of the revet-
ment, eventually causing stones to slump and loosen.
Therefore, revetments do not represent a permanent
shore protection solution in these environments, as they
generally require regular maintenance and repairs to
maintain their effectiveness. Long-term erosion can often
lead to catastrophic failure of the structure. Structural
failure typically will occur during a significant storm
surge event and can be exacerbated if the structure and/
or beach are not maintained. Unlike most “soft” shore
protection measures, revetments often do not exhibit
signs of structural inadequacy, which can lead to a “false
sense of security” for property owners in areas fronted by
these “hard” shore protection measures.
Specific to Pleasant Bay, recent geomorphic changes to
the multiple inlet system appear to indicate that both
the high tide elevation and the tide range are decreasing
subsequent to the formation of the 2007 over the past
few years (Legare and Giese, 2016). While the formation
of both the 1987 and 2007 breaches through the Nauset
Barrier Beach system initially led to significant shoreline
erosion pressures due to increased tide range, and wave
exposure in some cases, much of this influence has begun
to moderate. It appears that the continuation of the long-
term Nauset Beach growth cycle will lead to a decreased
tide range and the associated return to a more stable in-
land shoreline in the coming years. However, this process
will be gradual and occur over a period of decades. Sig-
Figure 18: A schematic
diagram showing the
influence of increased
water levels and
structure interaction
with the natural wave
environment.
5
Conclusions
19
The impacts to the inner shore of Pleasant Bay
and that portion of the Nauset Barrier Beach
fronting Pleasant Bay were shown to be directly
related to ongoing natural process, human alter-
ations and sea level rise. Sea level in and around
Pleasant Bay is rising and the rate of sea level rise
is also increasing. In the last century it rose at a
rate of 1ft/century and future projections forecast
a further increase in that rate.
Changes to landside intertidal coastal resources of
Pleasant Bay north of Ministers Point will include
mostly losses, and some gains in resource areas.
In the Chatham Harbor area, westward movement
of sediment from the barrier beach and barrier
island may create shoaling and possible accretion
of beaches along some sections of the mainland
as noted in Figures 7, 9, and 11 as well as ob-
served historically and most recently following
the 1987 break. Amounts and duration of any
potential accretion have not been calculated. Be-
cause the Chatham Harbor area is so geologically
dynamic and has the highest variability in the
system, any projection carries uncertainty.
Human actions to prevent erosion, such as instal-
lation of coastal engineering structures, in one
place will accelerate erosion of the fronting beach
and adjacent areas.
Long-term preservation of sediment transport
processes and the coastal resources they support
will require balancing preservation of natural
resources with protection of public and private
property, infrastructure, and access points.
All management activities should take into con-
sideration the short-, mid- and long-term impacts
of any proposed alteration and/or maintenance
that may directly or indirectly affect the sediment
transport processes in the Nauset Barrier/Pleasant
Bay system.
nificant nor’easters will continue to create erosion pres-
sures that likely will need to be evaluated on a site-by-site
basis. In the short-term (i.e. the next 20-to-30 years), the
influence of the Nauset Barrier Beach system on water
levels in Pleasant Bay will likely be more significant than
the influence of long-term relative sea-level rise. Overall,
the recent tide data within the Pleasant Bay and Chatham
Harbor system, as well as future predictions of the geo-
morphic migration of the fronting barrier beach system,
support the hypothesis of continued future reduction in
Pleasant Bay high tide elevations. These reductions in
tide elevations, along with westward movement of barrier
beach sediment leading to possible inner shoreline beach
accretion along some sections of the mainland, likely will
significantly reduce or perhaps eliminate the need for
more large-scale armoring of the estuarine shoreline.
Areas in proximity to coastal engineering structures,
particularly those structures designed to prevent erosion
behind them are most impacted by sea level rise. Con-
sequently, the intertidal areas fronting those structures
are among the most vulnerable to increases in sea level.
Coastal engineering structures prevent these areas from
migrating landward and keeping pace with sea level
rise. Ironically, the more effective these structures are at
preventing erosion, the greater the adverse effects from an
ecosystem perspective. Erosion that is prevented in these
areas would have supplied sediment to downdrift areas. In
response, homeowners downdrift of these structures often
install their own structures, which will in turn starve
additional downdrift areas of needed sediment. Naturally
evolving coastal areas are superior to those with engi-
neering structures with regards to providing ecosystem
services as well as responding to future storm events and
ongoing sea level rise.
20
GLOSSARY
Barrier Islands: A detached portion of a barrier
beach between two inlets.
Barrier Spits: A barrier beach attached to the main-
land that extends into open water at the other end.
Coastal Engineering Structures: any structure that
is designed to alter wave, tidal or sediment trans-
port processes in order to protect inland or upland
structures from the effects of such processes.
Downdrift: In the direction of longshore sediment
transport.
Ecosystem Services: Any positive benefit that
wildlife or ecosystems provide to people.
Intertidal: The area of the shore that lies between
the highest astronomical high tide and the lowest
astronomical low tide.
Mean High Water: The average of all the high
water heights observed over a period of time.
Mean Low Water: The average of all the low water
heights observed over a period of time.
Mean Sea Level: The average of sea level heights
over a period of time.
NAVD 88: North American Datum of 1988. A fixed
vertical reference surface adopted as a standard
geodetic datum. The datum was derived from a
general adjustment of elevation data for the United
States, Canada, and Mexico. NAVD 88 should not
be mistaken for Mean Sea Level.
Passive Erosion: After a hard structure is built
along an eroding coastline, the shoreline will
eventually migrate landward on either side of the
structure.
Sequester: To isolate or store away from interaction
with surrounding areas or processes.
Supra-tidal: The area of the shore that lies above
the highest astronomical high tide inundated only
during exceptional tides and/or storm surges.
Updrift: In the opposite direction of longshore
sediment transport.
REFERENCES
Berman, G.A., 2015. Dealing with Coastal Erosion:
The Spectrum of Erosion Control Methods. Marine
Extension Bulletin. Woods Hole Seagrant Program/
Cape Cod Cooperative Extension n. 15-01. 2 p.
Berman, G.A., 2015. The Effect of Sea Level Rise on the
Barrier Beaches of Cape Cod, Martha’s Vineyard, and
Nantucket. Marine Extension Bulletin. Woods Hole
Sea Grant Program/Cape Cod Cooperative Extension.
n. 15-201. 4 p.
Borrelli, M., 2009. 137 years of Shoreline Change in
Pleasant Bay: 1868 - 2005. Pleasant Bay Resource
Management Alliance, p. 29.
Church, J.A., Clark, P.U., Cazenave, A., Gregory,
J.M., Jevrejeva, S., Levermann, A., Merrifield, M.A.,
Milne, G.A., Nerem, R.S., Nunn, P.D., Payne, A.J.,
Pfeffer, W.T., Stammer, D., and Unnikrishnan, A.S.,
2013. “Sea Level Change”. In: Climate Change 2013:
The Physical Science Basis. Contribution of Working
Group I to the Fifth Assessment Report of
the Intergovernmental Panel on Climate Change
[Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K.
Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M.
Midgley (eds.)]. Cambridge University Press, Cam-
bridge, United Kingdom and New York, NY, USA.
Donnelly, J.P., Cleary, P., Newby, P., and Ettinger, R.,
2004. Coupling instrumental and geological records
of sea-level change: Evidence from southern New
England and an increase in the rate of sea-level rise
in the 19th century. Geophysical Research Letters, v.
31, paper LO523.
Engelhart, S.E., 2010. Sea-level changes along the
U.S. Atlantic coast: Implications for Glacial Isostatic
Adjustment Models and current rates of sea-level
change. Publicly accessible Penn Dissertations. Paper
407. University of Pennsylvania (repository@pobox.
upenn.edu).
References continued on page 21
21
Giese, G., S., 1988, Cyclical behavior of the tidal
inlet at Nauset Beach, Chatham, Massachusetts, in
Aubrey, D. G., and Weishar, L., eds., Hydrodynamics
and Sediment Dynamics of Tidal Inlets, Lect. Notes
Coastal Estuarine Stud.: Washington D.C., AGU, p.
269-283.
Giese, G.S., Mague, S.T., Rogers, S.S., 2009. A Geo-
morphological Analysis of Nauset Beach/Pleasant
Bay/Chatham Harbor for the Purpose of Estimating
Future Configurations and Conditions. The Pleasant
Bay Resource Management Alliance, p. 32.
Giese, G.S., 2012. Analysis of tidal data from Meet-
inghouse Pond, Chatham Fish Pier and Boston:
With application to management. Pleasant Bay
Resource Management Alliance, p. 17.
Giese, G.S., Kennedy, C.G., 2015. Analysis of Tidal
Data from Meetinghouse Pond, Chatham Fish Pier
and Boston: January 2012 - June 2015. The Pleasant
Bay Resource Management Alliance, p. 11.
Howes, B., Kelley, S. W., Ramsey, J. S., Samimy,
R., Schlezinger, D., and Eichner, E., 2006, Linked
Watershed-Embayment Model to Determine Critical
Nitrogen Loading Thresholds for Pleasant Bay, Cha-
tham, Massachusetts.: Massachusetts Department of
Environmental Protection.
IPCC, 2007. Climate Change 2007: Synthesis Re-
port. Contributions of Working Groups I, II and III
to the Fourth Assessment Report of the Intergovern-
mental Panel on Climate Change [Pachauri, R., and
A. Reisenger, (eds.)]. IPCC, Geneva, Switzerland.
IPCC, 2013. Climate Change 2013: The Physical
Science Basis. Contribution of Working Group I to
the Fifth Assessment Report of the Intergovernmen-
tal Panel on Climate Change [Stocker, T.F., D. Qin,
G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung,
A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)].
Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA.
Kirwan, M.L., Temmerman, S., Skeehan, E.E., Gunt-
enspergen, G.R., Fagherazzi, S., 2016.
Overestimation of marsh vulnerability to sea level
rise. Nature Climate Change 6, 253-260.
Kopp, R.E., Kemp, A.C., Bittermann, K., Horton,
B.P., Donnelly, J.P., Gehrels, W.R., Hay, C.C., Mitro-
vica, J.X., Morrow, E.D., and Rahmstorf, S., 2016.
Temperature-driven global sea-level variability in the
Common Era. Proceedings, National Academy of
Sciences, v. 113, n. 11, E1434-E1441.
Legare, B., and Giese, G. S., 2016, Analysis of Tidal
Data from Meetinghouse Pond, Chatham Fish Pier
and Boston: July 2015 – July 2016: Center for
Coastal Studies. p.10.
Marindin, H.L., 1890. Cross-Sections of the Shore
of Cape Cod Between Chatham and the Highland
Light-House. Report of the Superintendent of the
United States Coast Survey showing the Progress of
the Survey during the Fiscal Year ending with June,
1889.
Appendix No. 13. Government Printing Office,
Washington. 1890. p. 409 – 457.
Massachusetts CZM, 2013. Sea Level Rise: Under-
standing and Applying Trends and Future Scenarios
for Analysis and Planning. Massachusetts Office of
Coastal Zone Management, Boston, MA. 18 p.
Mitchell, H., 1871. Report to Prof. Benjamin Peirce,
Superintendent United States Coast Survey, Con-
cerning Nausett Beach and Peninsula of Monomoy.
Report of the Superintendent of the United States
Coast Survey showing the Progress of the Survey
during the Year 1873.
Appendix No. 9. Government Printing Office, Wash-
ington. 1875. p. 134 – 143.
Mitchell, H., 1873. Additional Report Concerning
the Changes in the Neighborhood of Chatham and
Monomoy. Report of the Superintendent of the
United States Coast Survey showing the Progress of
the Survey during the Year 1873. Appendix No. 9.
Government Printing Office, Washington. 1875. p.
103 – 107, plus sketch.
US Army Corps of Engineers, 1984, Shore Protec-
tion Manual: Coastal Engineering Research Center.
Vol 1&2. p.652.
22
Photo above: Fran McClennen
Design: Lianne Dunn
