Route 154, a two-lane State roadway, bisects the Plum Bank Marsh Wildlife Area and connects Old Boston Post Road in the North to Cornfield Point in the South. Within the Marsh, Route 154 incorporates two bridges, and one of these existing bridges is planned by ConnDOT to be replaced. A residential community is located to the south of this bridge, including homes, private property and floating docks and a boat ramp along the downstream southern side of the marsh channel.
Back River is a natural tidal marsh channel, hydraulically connecting marsh to Long Island Sound. Upstream and downstream of the bridge, the Back River bends sharply to the north and continues to meander throughout the marsh. The existing (and proposed) bridge restrain the natural meander of the channel and also result in high velocity flow and eddies and whirlpools. This, possibly with other factors, appears to be contributing to significant erosion of bank edges, loss of marsh area and deep channel scour holes. Scour holes are located within the channel and are deep. Sea level rise also significantly threatens Plum Bank Marsh, including the project area and accelerated erosion along old historical mosquito trenches and loss of the marsh peninsula would significantly increase the flood and erosion risk of adjacent residential areas.
The project goals are to utilize a Natural and Nature-Based Feature (NNBF) approach to mitigate the existing adverse impacts to the marsh and channel, providing both ecological and shoreline protection benefits:
• Ecological: Restore coastal habitat
• Shoreline Protection: Reduce marsh edge erosion
• Public Resource: Reduce adverse impacts to a Connecticut WMA and Marine Protected Area.
• Innovation: Pilot project to evaluate use of NNBFs in conjunction with transportation structures.
• Improve shoreline resilience to sea level rise at the project site.
CIRCA is funding supplemental field surveys, conceptual design, and pre-application meetings for this pilot project with the goal of determining how a living shoreline can be used for marsh channel stabilization.