Massachusetts Bays National Estuary Program Estuary Delineation and Assessment 2.0 Massachusetts Bays National Estuary Program Final Report August 2017 Estuary Delineation and Assessment 2.0 Prepare d for and Edited by: Prepared by: Massachusetts Bays National Estuary Program Estuary Delineation and Assessment 2.0 Contents EXECUTIVE SUMMARY .............................................................................................................................. 1 1. PROJECT BACKGROUND .................................................................................................................... 2 2. DELINEATION OF ESTUARINE BOUNDARIES ................................................................................... 3 2.1 Determination of Seaward Boundary ..................................................................................... 3 2.2 Determination of Landward Boundary ................................................................................... 4 2.3 Delineation of Remaining Estuarine Watershed Boundary.................................................... 6 2.4 Delineation of Cape Cod Groundwater Contributing Areas (GWCA) .................................... 6 3. SELECTION OF ENVIRONMENTAL ATTRIBUTES.............................................................................. 7 4. ANALYSIS OF ATTRIBUTES............................................................................................................... 17 4.1 Summary of Analysis ........................................................................................................... 17 4.2 Limitations, Data Gaps, and Next Steps .............................................................................. 25 FIGURES Figure 2.1 Massachusetts Bays National Estuary Program Planning Area ........................................... 2 Figure 2.2 Salem Sound Estuarine Watershed: Freshwater Tributary Inclusion vs. Exclusion ...................5 TABLES Table 3.1 List of new attributes ………………………………. ..................................................................... 7 Table 2.2 List of Attributes and associated statistics applied .....................................................................14 APPENDICES Appendix A: Methodology for Estimating Annual Stormwater Runoff Volume Appendix B: Watershed Delineation Maps Appendix C: Results of Estuarine and Inter-Estuarine Watershed Characterization Massachusetts Bays National Estuary Program Estuary Delineation and Assessment 2.0 Executive Summary In 2012, The Massachusetts Bays National Estuary Program (MassBays) was in the process of updating its Comprehensive Conservation and Management Plan (CCMP) with new, expanded focus on near- shore estuaries and embayments. To facilitate analysis, MassBays undertook an Estuarine Assessment and Delineation (EDA1.0) to accomplish the following: 1. Delineate estuarine watershed boundaries, encompassing all tributary areas that are tidally influenced, as well as open water regions of the estuary that contain important ecological resources; 2. Develop a set of geospatial attributes that can be used to assess the ecological health of each estuarine watershed; and EDA 1.0 resulted in the delineation of 47 estuarine embayments. In response to comments, and recognizing the importance of the role that inter-estuarine habitats (rocky shore areas, dunes, bluffs, and beaches, e.g.) play in the health of estuarine ecosystems, MassBays initiated EDA 2.0. The scope and implementation of EDA 2.0 was as follows: 1. Delineate any inter-estuarine coastal watersheds such that the entire Massachusetts Bays coastline can be assessed, updating existing estuarine watershed boundaries as needed. EDA 2.0 produced a set of 69 estuarine and inter-estuarine assessment areas. The delineations were prepared using topography, attributes of tidal influence, existing USGS and MassGIS watershed boundary lines, and comments and input from MassBays Regional Coordinators. 2. Identify updates to datasets used in EDA1.0 and use these new data to characterize each assessment area. 3. Incorporate a new set of attributes that characterize human uses. New attributes include: Beach closure days Mooring fields Marinas Dredging projects Seawalls and related structures Coastal dunes, coastal beaches, and rocky intertidal shores Public and semi-public beach length Boating access Coastal beach water quality 1 Massachusetts Bays National Estuary Program Estuary Delineation and Assessment 2.0 1. Project Background The Massachusetts Bays National Estuary Program (MassBays) is one of 28 designated Estuaries of National Significance in in the National Estuary Program which is authorized by Section 302 of the Clean Water Act and administered by t he U.S. E n v i r o nmental Protection Agency (EPA). The MassBays Planning area covers more than 1000 miles of coastline a l ong I p s w i c h , Massachusetts and Cape Cod Bays and serves 50 coastal communities from Salisbury, on the New Hampshire border, to Provincetown at the tip of Cape Cod (Figure 2.1). The planning area is divided into five management regions: Upper North Shore, Lower North Shore, Metro Boston, South Shore, and Cape Cod. In 2012, MassBays published the first Estuarine Delineation and Assessment (EDA1.0) which defined and characterized 47 estuarine embayments within the MassBays planning area using ecosystem-based landward and seaward boundaries, and metrics for which data were available across the planning area. With the ongoing revision of the MassBays Comprehensive Conservation and Management Plan Figure 2.1: Massachusetts Bays National (CCMP), MassBays is focusing on priority needs and Estuary Program Planning Area changing ecosystem conditions at the embayment level. To support this effort, MassBays contracted with Geosyntec Consultants (Geosyntec) to conduct a comprehensive update of the 2012 EDA1.0. EDA 2.0 will serve as a tool for assessing and tracking localized trends and changing conditions of estuarine and inter-estuarine species and habitats, providing information for use by resource managers and decision- makers to improve ecosystem health and alleviate the impacts of stressors. The goals of EDA 2.0 were to: 1. Delineate any inter-estuarine coastal watersheds such that the entire Massachusetts Bays coastline can be assessed, updating existing estuarine watershed boundaries as needed. 2. Identify updates to datasets used in EDA1.0 and use these new data to characterize each assessment area. 3. Incorporate a new set of attributes that characterize human uses. 2 Massachusetts Bays National Estuary Program Estuary Delineation and Assessment 2.0 2. Delineation of Assessment Units The basis for the delineation in EDA 2.0 was the set of 47 estuarine assessment units produced in 2012 in EDA1.0. The original process of estuarine watershed delineation generally consisted of the following three steps: 1. Determine a seaward boundary that encompassed the assessment area and any nearby major estuarine ecological resources; 2. Determine a landward boundary that is reflective of the extent of tidal influence within the estuary; and 3. Delineate the watershed that is dictated by the boundaries established in steps 1 and 2. Given the variety of embayment characteristics across the estuaries, the process described above was sometimes varied on a case-by-case basis. For instance, some assessment areas may not have a major freshwater tributary on which to establish a landward boundary. Instead, these watersheds were delineated simply by determining the proximal area contributing to the embayment using topography. Also, several of the areas are located on Cape Cod and are influenced by a groundwater contributing area rather than a typical watershed defined by surficial topography. Where special circumstances dictated a deviation from the general delineation process, best professional judgment was used to determine what the most informative and useful “estuarine watershed” would be. For EDA 2.0, areas of the coast that were not previously characterized during EDA1.0 were delineated and assessed. These areas were generally near-shore stretches of beach or headland that existed between estuaries. The process for identifying and delineating these assessment units was as follows: Step 1: The MassGIS “Drainage Sub-basins” was intersected with the existing estuarine assessment units from EDA1.0. The resulting subbasins and subbasin segments that did not overlap EDA1.0 assessment units and that were also coastal, were selected as the draft basis for the inter-estuarine assessment units. Step 2: The extent of Chapter 91 Jurisdiction was determined by overlaying the MassGIS “Tidelands Jurisdiction Datalayer” on the new EDA 2.0 assessment units. As with EDA1.0, Chapter 91 Jurisdiction is used to indicate the landward extent of tidal influence. In any cases where an inter-estuarine assessment unit from Step 1 extended beyond the Chapter 91 Jurisdiction extent, the assessment unit was trimmed (See section 2.2). Step 3: Some stretches of coastline were divided into multiple sub-basins by the MassGIS “Drainage Sub-basins” layer. When multiple sub-basins were contiguous between existing EDA1.0 assessment units, these sub-basins were merged into a single assessment unit. After completing this process, the draft delineations were reviewed with MassBays Regional Coordinators and revised based on their comments. Some existing estuarine assessment units from EDA1.0 were also updated based on MassBays review (e.g., the Merrimack River assessment unit was split