Plymouth: Nourishment of Eroded Overwash Areas at Long Beach

Find a description of this featured project funded through the Coastal Resilience Grant Program.

The Coastal Resilience Grant Program provides funding and technical assistance to municipalities and nonprofits to advance innovative local and regional efforts to address coastal flooding, erosion, and sea level rise impacts through communication and public outreach initiatives, vulnerability assessments, planning activities, engineering projects, and natural storm damage protection. 

The summary below describes a featured Coastal Resilience Grant project to highlight the range of projects eligible for funding and to demonstrate some of the lessons learned through project implementation. Coastal Resilience Grant Program - Featured Projects provides links to additional examples.

Project Summary

In Fiscal Year (FY) 2015, the Town of Plymouth received a grant to complete a dune nourishment project at eroded washover areas on Long Beach:

  • Project Category: Shoreline Restoration
  • Summary: The Town of Plymouth filled severely eroded washover areas in the dunes with rounded cobbles, gravel, and sand to increase storm damage protection and flood control for Plymouth Harbor. The mixture of cobbles, gravel, and sand is of similar size and texture to the existing beach sediment and is less susceptible to erosion than using sand alone.
  • Project Funding:
    • FY15 Grant Award: $279,080
    • Match: $162,675 (37% of total project cost)

Community Overview

Located on the South Shore of Massachusetts, Plymouth is New England’s oldest municipality and home to significant historic assets. The downtown waterfront area stretches four and a half miles, making the Town vulnerable to coastal storm and climate change impacts. Long Beach, a narrow barrier beach extending three miles northwest off of Plymouth’s mainland, helps protect the mainland shoreline, harbor, and navigational channel, and is a valuable public recreational resource.

Climate Impact

Severe storms have caused significant erosion on the southern portion of Long Beach. Waves can overtop the existing stone dike along Cape Cod Bay, rush over the dunes at a high velocity, and scour the dunes, creating channelized washover areas. In some of these areas, the dune elevation was so low that water could flow over Long Beach into Plymouth Harbor during above-average tides. These eroded washover areas weaken the storm damage protection function of the barrier beach and increase its susceptibility to breaching in significant coastal storms.

Coastal storm and climate change impacts directly affect Long Beach, including Ryder Way, a gravel road that serves as the only land access for emergency vehicles, 21 private properties, and recreational areas. Bird populations are also significantly impacted because Long Beach is an important nesting area for several species of coastal water birds and an important staging area for migrating shorebirds.

Project Goals

The Town applied for a grant to nourish 10 severely eroded washover areas on Long Beach to help increase its resilience during coastal storm events. Elevating these low-lying washover areas to the same height as the surrounding dune spreads the flow of water over a larger surface area, which helps prevent overwash channels and reduces dune erosion. Filling the washover areas with compatible beach material (i.e., the mixture of sand, gravel, and cobble similar in size to the existing substrate) can increase project longevity by ensuring the material stays in place longer during storms than sand alone.

Approach and Result

The Town worked with the Massachusetts Division of Fisheries and Wildlife’s Natural Heritage & Endangered Species Program to determine the slope and elevation of the mixed-sediment nourishment that will enhance the natural function of the barrier beach while protecting nesting habitat for Piping Plovers and Least Terns, which are both protected by the Massachusetts Endangered Species Act. The Town developed a design plan and completed permitting so that construction could begin after the summer nesting and recreational beach season.

Construction services were provided by the Town’s Department of Public Works (DPW) and involved placing 12,365 tons of natural rounded gravel, cobble, and sand in 10 eroded sites (covering a total area of 106,897 square feet).

In March 2018, severe winter storms impacted the area. Town officials believe that Long Beach would have breached without the cobble nourishment.

Project Photos

view of eroded dune area

Eroded washover area looking north along Plymouth Long Beach prior to the nourishment.

view of eroded dune area

Eroded washover area behind the stone dike looking toward the ocean.

view of dump truck providing sediment for dune restoration

Sediments being added to nourish washover areas during project construction.

view of dune area after nourishment

Filled washover area after the nourishment looking south along Plymouth Long Beach.

view of dune area after nourishment

Filled washover area behind the stone dike looking toward the ocean.

Partners and Other Support

The project was managed by the Plymouth Department of Marine and Environmental Affairs and involved staff from the Plymouth DPW (foreman and heavy equipment operators) and Engineering Divisions. Together, the local project team provided 37% of the total project cost in cash contributions and in-kind services, which included outreach to and coordination with Long Beach property owners to keep residents informed throughout the project. The team worked in consultation with CZM, the Massachusetts Environmental Policy Act Office, and Natural Heritage & Endangered Species Program to secure permits.

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