Coonamessett River Fish Passage & Habitat Improvements, Massachusetts

The Coonamessett River is a small, spring-fed stream that flows into Vineyard Sound. The project site is situated at the downstream end of the river and experiences some tidal influence. Following a long history of mill construction and cranberry cultivation, fish populations and aquatic habitat were in decline. Inter-Fluve was retained by the Town of Falmouth to identify feasible alternatives for improving fish passage at four partial fish barriers, improving fish habitat, and maintaining organic cranberry cultivation and recreational opportunities. Construction, completed in 2018, included hydraulic modeling, sediment sampling, preliminary and final designs, permitting, and construction observation for the removal of two dams, replacement of an understized culvert with a free span bridge, and the channel reconstruction and wetland restoration of three cranberry bogs totaling approximately 30 acres.

The completed project will bring back river herring and trout and provide a barrier for storm surges. Photo credit: Adam Soule

Microtopography, seen here, breaks up the surface and brings the wetland seedbank along with peat and other organic matter to the surface. The technique generates a range of micro-environments that allow a diversity of plant species to become established as well as wetland pools in which amphibians reproduce. Photo credit: Adam Soule

One of the more complex aspects of this project was the construction sequencing to breach all tidal channels at once. On the scheduled breach day, nine excavators (like this one) simultaneously removed the final remnants at each of the levee breach locations as the tide receded.

Fifteen wood placements were installed in marsh channels, each consisting of 2 ‐ 3 logs with rootwads and 3 ‐ 4 vertical snags used to pin and ballast the rootwads.