Cape Cod

Chatham, Massachusetts, United States

Stabilizing an eroding coastline with a system of natural materials and native plants. Coastal communities on Cape Cod have suffered from increasing damage due to sea level rise, growing storm intensity and frequency, and worsening erosion. One property had experienced erosion along the bottom of the bank, and in 2010, a coir fiber roll array was installed to slow this erosion. The array quickly fell into disrepair and required replacement due to inadequate installation techniques and materials not designed for the coastal environment. Wilkinson Ecological Design proposed a nature-based approach that included a properly installed and maintained coir fiber roll array to stabilize the eroding toe of the bank and a reinforced transitional high marsh to provide a second layer of stabilization that would also restore salt marsh species where none existed. The union of these techniques maximizes the stabilizing capabilities of a living shoreline while enhancing the ecological benefits and protective aspects of a salt marsh. After extensive permitting beginning in 2014, the protective bioengineering structures were installed in 2018.

Article Cover: After four seasons of growth, the native plant communities have become well established, providing wildlife benefits and stabilizing soils while conserving the natural beauty of this Cape Cod shoreline. (Photo by Wilkinson Ecological Design)

Producing Efficiencies

The project restored an eroding coastline with a healthy and functioning plant community via the fully vegetated coir fiber roll array and reinforced transitional high marsh. This nature-based solution uses the restored native plant communities to attenuate wave action and reduce the likelihood of future erosion while preserving the natural shoreline’s aesthetics. This nature-forward initiative vastly differs from the traditional coastal engineering structures used today—seawalls, bulkheads, and revetments— that can change sediment distribution and hinder salt marsh migration.

Preconstruction visits to the site revealed the largely eroded bank was in great need of stabilization.

(Photo by Wilkinson Ecological Design)

Using Natural Processes

Naturally vegetated coastlines provide ecological and protective benefits, including wave attenuation, habitat creation, and water filtration. This intervention champions the restoration of salt marsh and maritime shrubland to reestablish a healthy coastal ecosystem and naturally anchor these ecosystem services back into the land. The restoration of these native plant communities not only is integral to the system’s projected life span but also improves the shore’s ability to withstand erosion and provides salt marsh an area to retreat from sea level rise.

The base row of the fiber roll is laid out and the first rows of helical anchors are driven, ensuring the fiber rolls can withstand storm energy and wave action.

(Photo by Wilkinson Ecological Design)

The fiber roll array has been installed and nourished, the trench for the reinforced transitional high marsh has been excavated, and coir and jute blanket materials are being set in place.

(Photo by Wilkinson Ecological Design)

Broadening Benefits

Cape Cod faces increasing coastal flooding due to more frequent storms and sea level rise caused by anthropogenic climate change. Living shorelines like this offer a physical buffer to vulnerable coastal communities while increasing the area’s ecological value and preserving the natural aesthetic. This effort is one of a host of reinforced-marsh projects across Cape Cod designed by Wilkinson Ecological Design to stabilize eroding shorelines without sacrificing the iconic ecological identity that fuels tourism in Cape Cod.

The outer envelope of coir and jute material is being hand-sewn after the cobble and planting medium was added to the reinforced transitional high marsh.

(Photo by Wilkinson Ecological Design)

Promoting Collaboration

The design of a reinforced high marsh was a collaborative project in consultation with the Massachusetts Department of Environmental Protection, the Coastal Engineering Company, and the primary stakeholders on site. The process allowed a novel approach, using a multilayered method to increase the stabilization capabilities of a living shoreline while complying with all local and state regulatory requirements.

The transitional high marsh species are being planted into the completed installation.

(Photo by Wilkinson Ecological Design)

The planted native species are seen establishing during the first season, expanding their root systems while the coir materials hold soils in place.

(Photo by Wilkinson Ecological Design)