Buzzards Bay National Estuary Program

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Draft Chapter 2:
Buzzards Bay Watershed, Living Resources, and Governance

About the new Buzzards Bay CCMP Action Plans
The Buzzards Bay NEP is now updating our 1992 landmark Buzzards Bay Comprehensive Conservation and Management Plan (CCMP) to reflect the great progress achieved since that plan was finalized. It will include new goals, objectives, and recommendations to meet the environmental needs for Buzzards Bay and its surrounding watershed throughout the next decade. This new document will also meet the requirements for a Massachusetts Watershed Action Plan, which will enable new funding opportunities through the Commonwealth of Massachusetts.

On this page is a draft action plan from the updated Buzzards Bay Comprehensive Conservation and Management Plan. The text on this page is a public draft provided to invite comment and discussion of the subject by residents and stakeholders. It may contain goals and recommendations that have not yet been endorsed or approved by the Buzzards Bay Steering Committee. The views or information contained here do not necessarily reflect the views of the Commonwealth of Massachusetts or the US Environmental Protection Agency.

We want your feedback on each action plan. First, please read the entire action plan on each page then at the bottom of the action plan pages, click the "rate each recommendation now" button to provide comments on each goal, objective and recommendation contained in this Action Plan. Based on your feedback, we will update and revise all the action plans in the new CCMP.


This page has only a few highlights of this chapter.

Read the actual text of Chapter 2 as a pdf file (1.0 MB), with graphics.

Buzzards Bay: Its Watershed, Living Resources, and Governance

[This web page just has a few opening paragraphs. Open the pdf file above for the entire chapter.]

Buzzards Bay Setting

Buzzards Bay is a moderately large estuary located between the western most part of Cape Cod, Southeastern Massachusetts, and the Elizabeth Islands. The bay is 28 miles long (45 kilometers), averages about 8 miles (12 kilometers) in width, and has a mean depth of 36 feet (11 meters). It is approximately 228 square miles (590 square kilometers) in size. The coastline stretches over 280 miles (470 kilometers) and includes 11 miles (18 kilometers) of public beaches that lure thousands of tourists from Massachusetts and neighboring states.

The Buzzards Bay watershed or drainage basin (Figure 4) covers 435 square miles (1209 square kilometers) and includes all or large sections of 17 municipalities, and smaller portions of three additional communities in Massachusetts and two communities in Rhode Island. A complete list of all the communities and their area and population within the watershed are shown in Table 1.

The ratio of watershed land area to water surface is 1.9:1. This is relatively low compared to other National Estuary Programs and large east coast estuaries such as Chesapeake Bay and Delaware Bay, which have land-to-water ratios of 14.5:1 and 17.3:1 respectively. Approximately 249,000 people reside in the drainage basin at an average concentration of 572 per square mile, or 0.9 people per acre.

The Bay itself is part of an interconnected hydrologic system that includes several rivers. Groundwater seepage accounts for large part of the freshwater inflow to Buzzards Bay, particularly in Wareham, Bourne, and Falmouth which have large sandy soiled glacial outwash plains and till areas. Along its western shore (west of the Cape Cod Canal) the drainage basin is formed by seven major river basins and a number of smaller ones. The largest river basins include the Agawam, Wankinco, Weweantic, Mattapoisett, Acushnet, Paskamanset, and Westport.

As noted above, the eastern shore of Buzzards Bay (Cape Cod Canal to Woods Hole) is drained mostly by groundwater. Several river systems smaller than those on the western shore also drain this portion of the basin. The prominent freshwater streams along the eastern shore are the Back , Pocasset, and Wild Harbor Rivers and Herring Brook.

In general, rivers within the Buzzards Bay drainage basin are slow moving, meandering streams near their headwaters and for most of their freshwater length. Nearing the coast, particularly on the western shore, past glacial erosion of the bedrock created wide river valleys that are now submerged, creating a network of broad fringing tidal estuaries. On average, Buzzards Bay rivers are considerably shorter (usually much less than 20 miles (34 kilometers)) and have smaller drainage areas than other rivers within the state.

Physical Features of the Bay

For past several million years, southern New England periodically submerged and emerged as the climate repeatedly warmed then cooled, and glaciers advanced and retreated across the northern hemisphere, causing sea levels to rise and fall. The last glacial period formed the current shape of Buzzards Bay approximately 15,000 years ago. The southeastern side of the Bay (Bourne, Falmouth, and the Elizabeth Islands) consists of glacial debris deposited by the glacier's leading edge. Consequently, it has a relatively smooth shoreline composed mostly of sand and gravel particles. The northwestern side (Wareham to Westport), with its numerous elongated bays and inlets, was formed by the glacier's retreat to the north. Many of these bays and inlets have since become sheltered from the ocean through the formation of barrier spits.

The distribution and stability of a bay environment depends on three primary physical characteristics of the water: circulation, salinity, and temperature. Tidal currents and wind are the dominant circulation forces in Buzzards Bay because the Elizabeth Islands protect the bay from large, long period, open ocean waves. Complete tidal mixing of Bay water with ocean water is estimated to occur every 10 days (Signell, 1987).

Water temperatures in the Bay range from a summer maximum of 71.6ºF (22 ºC) to 28 ºF (3 ºC) in winter. During colder winters, the upper reaches of the Bay often freeze, whereas during the spring and summer, solar warming keeps surface waters warmer than the deeper waters. The water temperature gradually decreases in relation to depth until a point is reached at which the temperature drops abruptly. Below that point, known as the thermocline, the temperature resumes a gradual drop until the coldest depths are reached at the bottom. The thermocline can act as a barrier to vertical mixing within estuaries and bays. Water turbulence helps to break up the thermocline and diminish layering. The shallowness of the Bay, combined with surface wave mixing and turbulent tidal flow, prevents strong thermal stratification, so that the Bay is well mixed through most of the year.

[etc. Open the pdf version to see maps, tables, and the rest of the text.]

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