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Island Ecosystem Restoration

Island habitat restoration projects must take into account the dynamics of the landform and its ecosystems. Barrier islands, for example, naturally move landward and experience overwash, which takes place when strong storm waves push beach sediments across the island to the bay side. Wildlife on islands has adjusted to, and sometimes relies on, these coastal processes.

In response, coastal engineers can construct restoration projects to accommodate these conditions. Beach nourishment projects can be designed to produce an overwash fan, thereby creating the barrier flat habitat that many shorebirds and shellfish require for nesting and foraging. Conversely, such projects can be designed to prevent natural overwash if necessary.

 

Assateague Island, Maryland

As one of the last undeveloped Atlantic Coast barriers, Assateague Island hosts many rare and important island ecosystems. It is known for its horse population, but indigenous species such as piping plover and least tern also rely on Assateague Island for natural habitats. Starting in the early 20th century, however, the island began eroding at an accelerated rate because jetties at Ocean City Inlet, directly north of the island, interrupted the natural supply of sediment.

To mitigate the jetty-induced erosion, the Corps and its partners, including the National Park Service, Maryland Department of Natural Resources, Maryland Geological Survey and Town of Ocean City, collaborated in 2004 to initiate a long-term renourishment project. The Corps releases dredged sediment twice a year in the nearshore waters at Assateague Island, thereby replicating the natural transport of sediment that is blocked by the Ocean City Inlet jetties. This sediment supplies substrate for the beach and barrier flat ecosystems, where federally threatened species, including piping plovers and the plant seabeach amaranth, are thriving once again. The steady supply of sediment also facilitates the natural process of dune building and it provides substrate for overwash, which extends the bayside marshes. Thousands of shorebirds and waterfowl find food and shelter in these varied island ecosystems.

The sediment nourishment project at Assateague Island encompasses storm damage reduction as well as ecosystem restoration, and it demonstrates how sediment management can preserve and enhance vital coastal ecosystems.

Assateague Salt Marsh

Assateague Salt Marsh
Source: National Park Service

Island Ecosystem Restoration

Protecting Habitats: The endangered piping plover nests and feeds on the barrier flats of Assateague Island, Maryland. The Corps worked with the National Park Service to modify a storm berm to allow overwash that creates the barrier flat ecosystem. This project combines shore protection and environmental restoration by maintaining the berm and also providing the conditions for habitat renewal.