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MassBays - Estuary Delineation and Assessment

MassBays is a large and complex system. A detailed characterization of the nearshore estuarine system highlights primary resources that need to be protected and issues to be addressed in order to improve estuarine conditions.

MassBays works primarily in the near-shore, estuarine systems of the region, in light of the strong leadership of Massachusetts’ watershed associations, and the significant and effective investment the Commonwealth has made in ocean planning. To support this work and as an alternative to a coastal delineation that uses municipal boundaries, MassBays uses ecosystem-based landward and seaward boundaries to define the MassBays planning area. Using these boundaries and geospatially available data, a glimpse into the relative ecological condition of estuaries within Massachusetts and Cape Cod Bays was assessed. 

Estuary Delineation and Assessment

The first Estuary Delineation and Assessment Report (EDA) published in 2012 identified 47 embayments within Ipswich Bay, Massachusetts Bay and Cape Cod Bay. The estuary assessment metrics were selected to focus on water quality conditions, estuarine habitat protection and restoration, and improvement of habitat continuity. Several resources and stressors were selected to characterize each embayment, including tidal flats, shorebird habitat and nesting sites, anadromous fish runs, salt marsh, eelgrass beds, shellfish habitat, impervious area, stormwater discharge, land use change, population density, 303(d) impairments, fish barriers, wastewater discharge, designated shellfish growing area classification, and stream crossings.

The final report 2012 Estuary Delineation and Assessment. Geosyntec Consultants, 2012. 

In 2016 MassBays embarked on a comprehensive revision of the EDA in order to: (1) update the existing datasets, (2) characterize and assess non-embayment (or interembayment areas) such as rocky shorelines and beaches, and (3) categorize embayments by type and establish target conditions. EDA 2.0 will therefore serve as a tool to tracking changes in estuarine conditions over time which will provide regular state of the bays reporting as required under Section 320 of the Clean Water Act.

The results of this extensive revision include 68 assessment areas that include embayments, rocky intertidal and (barrier) beaches. The revision also includes additional metrics covering ecological and stressor/use parameters. 

The final report is available below: 2017 Estuary Delineation and Assessment 2.0. Geosyntec Consultants and MassBays National Estuary Program. August 2017 (text only).

Note: Maps are available for download here. Hard copies of the report and maps are available upon request to:

Additional Resources

Estuary Delineation and Assessment Viewer

The EDA 2.0 results will be available shortly as a set of interactive maps that document resources and stressors in each of the embayments.


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