Salt marsh lives on the land between low tide and high tide.
It is populated by marsh grasses and other flora and fauna adapted to daily flooding.
Salt marshes are a major natural resource of Chatham. They provide much of the scenic charm of the town. They protect surrounding properties from the worst threats of storm surge and provide a wealth of ecological services to the flora, fauna, sea life and water quality.
In general, Cape Cod's salt marshes are as valuable as they are iconic. These beautiful, lowlying wetlands are some of the most biologically productive ecosystems on Earth. They play an outsized role in nitrogen cycling, act as carbon sinks, protect coastal development from storm surge, and provide critical habitats and nurseries for many fish, shellfish, and coastal birds.
Unfortunately, according to research from the Marine Biological Laboratory, more than 90 percent of the world's salt marshes are likely to be underwater by the end of the century - unless well-planned actions are taken to preserve the health of the marshes.
Salt marshes are threatened by escalating climate change, particularly sea-level rise. Recent federal studies show that the waters around Chatham are warming and rising even faster than in other parts of the world and faster than previously predicted. A new predictive model of local sea-level rise has recently been developed. This Massachusetts Coastal Flood Risk Model (MC-FRM) projects that sea levels may rise 2 1/2 feet by 2050, and close to 8 feet by the start of the next century along the Cape, with a 5% chance that it could be even worse.
Salt marshes have two natural defenses to sea-level rise, assuming the marsh is healthy (filled with native salt-marsh grasses) and tidally unrestricted. One is to gradually rise in place by building up the substrate level through sedimentation. The other is to migrate to slightly higher land nearby via an available migration path. The alternative is for the marsh to drown, merge into the open sea, and lose much of its protective storm buffering and ecological value.
Sedimentation raises the land, and sea-level rise raises the tides.
The difference between these two rates predicts salt-marsh preservation:
Predicted salt-marsh preservation = Elevation + Sedimentation - Sea-Level Rise
Future salt-marsh intertidal range can be predicted by taking the current ground elevation, adding
anticipated accretion of marsh floor by ongoing sedimentation, and subtracting interim sea-level rise.
If the rate of sea level is greater than the sedimentation rate, then the marsh will drown and become
open sea, no longer offering protection from storm surge.
Currently available elevation contours are not detailed enough for analysis of salt-marsh preservation and there is little available data on sedimentation rates in the Chatham marshes. There is also a need for baseline maps of vegetation (such as phragmites) to measure future success in marsh preservation. ECAC is conducting studies to collect this important data.
ECAC received a grant from Chatham's Community Preservation Act funds to study Forest River, Bucks Creek, Cockle Cove and Oyster Pond marshes during 2024/25 (see CPA 2023 proposal).
This project will systematically overview West Chatham's system of salt marshes to project likely futures. In particular, the project will use existing GIS data and sea-level-rise models to project sea-level rise at a fine grain around each marsh. It will then try to predict if the marsh can withstand that sea-level rise either by the marsh raising its floor or by migration to a nearby area through a migration path. In cases of potential migration, the project will look for possible barriers and issues, such as tidal restrictions or private ownership of land in the migration area and connecting pathways. Where there are such barriers and restrictions, the project will target possible future acquisition or conservation restrictions for the parcels or partial parcels in question.
The Town contracted with the Center for Coastal Studies in Provincetown to conduct the research. Here is Mark Borreli's preliminary report given to the ECAC at its February 2025 meeting:
[You can make the vvideo full screen by clicking on the small rectangle; use ESC to return.]
The final CPA 2024 study report will be posted here when available.
ECAC submitted a proposal for Community Preservation Act funds to contract for coordinated field studies during 2025/26 of the following marshes : Champlain Creek, Cotchpinicut, Frost Fish Creek, Minister's Point, Morris Island, Muddy Creek, Nickerson Neck, Red River, Tom's Neck (see CPA 2024 proposal).
The general goals of this project are:
1. To establish baseline data defining the elevation contours, sedimentation rates and vegetative cover of all the major salt marshes in Chatham.2. To project the future development of each of the salt marshes in Chatham, including areas likely to drown from sea-level rise and areas likely to migrate upland. This may indicate interventions necessary to preserve the health of the marshes and their fauna and flora, such as removing barriers to tidal flushing or supplementing sedimentation.
3. To provide data and projections for Town projects to mitigate climate change, such as modifying low-lying roads and siting utilities.
4. To inform the public about likely changes due to climate change, including at the level of detail of individual properties, at various times in the future.
5. To identify wetlands properties for donation or acquisition by the Town or land trust in order to facilitate future marsh migration or future Town interventions to preserve endangered areas of salt marsh
Pleasant Bay has been extensively studied because of its critical value to the lower Cape. It is the largest coastal embayment on Cape Cod. The Pleasant Bay system is state designated as Outstanding Resource Waters and an Area of Critical Environmental Concern. According to the Cape Cod Commission, the water surface of the Bay covers nearly 6,200 acres, and approximately 11,800 acres of land surface are within the Bay's watershed. Because of the Bay's significance as a regional resource, it requires coordinated management by the surrounding towns. In 1987 the Towns of Orleans, Chatham, Harwich and Brewster applied to the Commonwealth to designate Pleasant Bay an Area of Critical Environmental Concern (ACEC). The Commonwealth's ACEC designation led the towns to develop a resource management plan for Pleasant Bay and formation of the Pleasant Bay Alliance to coordinate management activities.
The Bay has been a historically valuable asset to the people of Chatham. It is of critical importance to Chatham's economy, fin and shell fishing, recreation, and many ecological benefits. Unfortunately, over decades of nutrient inputs from septic systems, fertilizers, stormwater runoff and other sources, the Bay has become extremely degraded. As a result, the Pleasant Bay Alliance and the Town of Chatham have commissioned numerous studies and directed efforts to improve water quality. For information on studies in Pleasant Bay and resulting data, see the Pleasant Bay Alliance website.
Muddy Creek forms the town line between Chatham and Harwich and is part of the Pleasant Bay ACEC. Muddy Creek is a tidal river and sub-embayment of the Pleasant Bay estuarine system which had been severely restricted by construction of an earthen embankment with stone culverts at the creek's discharge to Pleasant Bay where Route 28 crosses the creek. The significant nutrient impairments of the upper and lower part of the creek are well documented. Muddy Creek nutrient-related water quality has been monitored by the Town of Chatham and Pleasant Bay Alliance Water Quality Programs for decades. Studies showed that the creek was seriously degraded by the surrounding residential development, causing a continuing increase in nitrogen loading in Pleasant Bay.
Following more than a decade of coordinated effort, local, state and federal officials invested $6.47 million to improve water quality and ecological vitality in the Muddy Creek impaired tidal-creek system. The project involved replacing the undersized culverts that severely restricted tidal flows in Muddy Creek with a new 94-foot-wide single span bridge and restored tidal channel. Construction of the Muddy Creek Restoration Bridge began in January 2016, in accordance with MassDOT policy for state roads on Cape Cod. The project was completed before Memorial Day 2018.
There is ongoing monitoring and study of Muddy Creek and Pleasant Bay. To access two key studies, see the following documents on the websites of the Pleasant Bay Alliance and the Town of Chatham:
Muddy Creek restoration.
Muddy Creek bridge.
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"The Life and Death of Salt Marshes" by John Teal and Mildred Teal (1983) - This is the classic introduction to the ecology of salt marshes.
"Sippewissett: Or, Life on a Salt Marsh" by Tim Traver (2006) - Tales about a Cape Cod marsh in Falmouth.