Save Our Sound
From Coastal Erosion
Coastal erosion has become one of the most recognizable ecological threats facing Cape Cod, Martha’s Vineyard and Nantucket. While wind and rain have always reshaped our cliffsides and shorelines, climate change has accelerated this process. Our coastline is facing an unprecedented threat from sea level rise, storm surge, and erosion, and these risks are becoming more extreme.
In the long run, coastal erosion can cause lasting damage to the environment and natural habitat. Salt marshes, flood plains and dunes, which operate as an integrated system to prevent runoff, to collect and filter pollution, and to protect our shorelines, are decreasing, resulting in more sediment runoff. Coastal erosion also affects our communities through property and infrastructure loss or damage over time, leading to displaced individuals and businesses.
As the coast changes, communities are trying to address and prevent accelerated erosion with three broad approaches—protection, accommodation, and retreat. Protection-based strategies, such as creating a living shoreline by adding natural materials to form a barrier that grows over time, focus on shielding the diminishing beach. Accommodation strategies, including marsh restoration, try to mitigate local hazards by modifying existing natural systems or infrastructure. Retreat strategies focus on removing structures from the advancing tide line.
Specific examples to address erosion include building seawalls, depositing sand onto beaches, and using fiber rolls. These structures can help in slowing the process of erosion, but they can also have adverse effects. If seawalls are implemented only in selected areas, the places along the shore that do not have these protective measures may see even more accelerated erosion because the natural flow of erosion and redeposition is disrupted. Fiber rolls have been shown to help show erosion, but they break down over time and need to be maintained and replaced
The coastline of Monomoy off the elbow of Cape Cod is an example of drastic coastal changes due to erosion and sediment repositioning from storms. Although some coastal erosion and sediment changes occur naturally over time, Monomoy has seen a dramatic change over the span of the past 35 years. For example, the nor’easter of January 1987 created a new inlet through North Beach. This new inlet caused current and wave pattern changes, resulting in South Beach slowly connecting to the mainland. In 1990, South Beach showed signs of inching closer to the mainland, and by 1993 it connected completely. Since then, South Beach has continued to stretch southbound towards South Monomoy, and the waters around North Monomoy have created more sandbars and shallower waters. This storm and others, like the 2007 Patriot Day storm and the 2013 Valentine’s Day storm, have caused residential damage along the coast and significantly changed Monomoy and beaches around the Chatham area.