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Coastal Habitat Response to Changing Water Levels (SSAM)


All national estuarine research reserves monitor key indicators of estuarine function using the consistent, vetted protocols of the System-wide Monitoring Program (SWMP). This program, in place since the 1990s, produces monitoring data that is used both to detect short-term change and to establish a long-term baseline of environmental conditions at reserve sites.

While SWMP data have been used in addressing coastal management issues, the program was not originally envisioned as one to answer specific, predetermined scientific or management questions. By supplementing SWMP with additional information, however, it can provide a solid foundation for such studies.

NOAA Sentinel Sites

Nationwide, coastal communities share growing concern over their vulnerability to environmental change, particularly rising sea levels. 

The NOAA Sentinel Site Program forms networks of people, expertise, and resources that are focused on the common needs of specific places that people care about. These Sentinel Site Cooperatives are meant to empower communities to become more resilient in the face of climate change and sea level rise.

Sentinel Site Application Modules

As part of the Sentinel Site Program, the reserve system is developing "application modules" intended to detect vulnerabilities and to identify actions that will address them. The first of these sentinel site application modules (SSAM-1) focuses on coastal habitat response to changing water levels.

The Wells Reserve's SSAM-1 Monitoring Plan was approved by NOAA in February 2022.

Download the Monitoring Plan

In its implementation of SSAM-1, the Wells Reserve will examine the interplay of water levels, elevation, and plant communities at scales relevant to local, regional, and national decisionmakers. The reserve will integrate new, relevant SSAM-1 protocols with its existing monitoring program to become a contributing member of the NOAA Sentinel Site Program. In this role, it will provide coastal resource managers with the critical information necessary to inform vulnerability assessments and adaptation planning. 

Implementation Plan


Provide a design and methodological foundation to assess the impacts of changing climate conditions on emergent marsh habitat and provide a basis for comparing these impacts within New England reserves and across the reserve system. 


The primary objective is to detect and quantify long-term changes in the reserve's tidal marshes in response to changes in precipitation and sea level, spread of invasive species, landscape development, and altered hydrology.

Focused objectives are to: 

  1. Establish a network of permanent monitoring sites for assessing wetland characteristics
  2. Establish a network of geodetic benchmarks to tie monitoring sites to local tidal datums and the National Spatial Reference System
  3. Quantify changes in vegetation patterns, hydrology, and wetland surface elevation across spatial gradients and multiple timescales
  4. Determine relationships between wetland characteristics and changing environmental factors
  5. Communicate findings to coastal communities and decision-makers to inform coastal resource planning
  6. Demonstrate marsh monitoring techniques and explain research to educators, students, and members of the public

Questions to be Addressed

Specific questions we anticipate addressing include:

  • How do vegetation cover and community structure change over time in response to sea level rise and other stressors?
  • How does the response to these stressors vary spatially across different marsh habitats and elevation zones?
  • How is wetland surface elevation changing in response to changes in sea level and how do those changes influence sediment accretion and vegetation community structure?
  • Is wetland surface elevation increasing, and is it keeping pace with sea level rise?
  • As sea level rises, do we observe landward movement of marshes with conversion of upland habitat into salt marsh habitat, and a conversion of low elevation marsh to unconsolidated shoreline?

Additionally, our elective monitoring metrics will allow us to evaluate:

  • How are crab abundance and species composition changing in our salt marshes, particularly with the arrival of invasive species and range expansions of other species?
  • Does the arrival and spread of invasive or range-expanding decapods affect salt marsh vegetation or sediment composition?
  • How do sea level rise and altered hydrology affect pore water salinity over time and how does this affect vegetation community structure in different elevation zones?
  • How do hydrological changes at the upland edge translate to subsequent changes in vegetation composition?
  • How does sediment bearing capacity change over time, and how do changes in bearing capacity correlate with changes in above-ground biomass, vegetation species composition, and crab burrow distribution?

Guiding Documents

The SSAM-1 Monitoring Plan was developed using these resources:

  • SSAM-1 Program Plan Development and Review (SSAM-1 Workgroup 2020)
  • Sentinel Sites Program Guidance for Understanding Climate Change Impacts (NERRS 2012)
  • Accurate Elevations for Sea Level Rise Sentinel Sites (NOAA NOS 2019)
  • The Surface Elevation Table and Marker Horizon Technique (NPS 2015)
  • Coastal Habitat Response to Changing Water Levels (NOAA OCM 2016)
  • NERRS Vegetation Monitoring Standard Operating Procedure: Long-term Monitoring of Estuarine Vegetation Communities (NERRS Biomonitoring Workgroup 2020)


The Wells Reserve's SSAM-1 Monitoring Plan comprises these sections:


Communication and Outreach

  • Education Program
  • Coastal Training Program

Site-Based Monitoring Plan

  • Location of Infrastructure
  • Vegetation Monitoring
  • Wetland Surface Elevation Change Measurements
  • Vertical Reference Plan for SSAM-1 Infrastructure
  • Water Levels
  • Water Quality and Meteorological Data
  • Elective Parameters and Protocols



Download the Monitoring Plan

Last update: February 15, 2022

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