Removing shore protection structures to facilitate migration of landforms and habitats on the bayside of a barrier spit

摘要

Coastal landforms and habitats require space to reform in response to storm damage to increase the likelihood of long-term sustainability. The purpose of this study is to evaluate the potential for removing shore protection structures to allow natural shoreline processes to prevail as part of a strategy to adapt to sea level rise associated with climate change. The location of the study was Sandy Hook Spit, New Jersey, a site managed by the U.S. National Park Service (NPS). A field investigation was conducted to identify the structures that impede migration of landforms and habitats, the function of each structure in protecting resources, and the opportunities to facilitate landform migration by removing the structures or allowing them to deteriorate. Nineteen shore-parallel walls are present along the ocean and bay shore of a 10 km long portion of the spit. Most of the shore protection structures were built when the spit was formerly used by the US Army, and many bulkheads on the bay shore have deteriorated. Sediment will become available to the longshore transport system where protection structures are removed, contributing to spit growth at the ends of drift cells, possibly mimicking the spits that were more conspicuous on the bay shore prior to human alterations. Observations indicate that new habitat can be created by loss and re-creation in a different location by longshore extension, not just by landward migration. Allowing shore protection structures to deteriorate will leave human infrastructure in the landscape. Removing these structures is more costly but can result in a more rapid reversion to a natural system. The time horizon is critical in determining the social, political and economic feasibility of removing structures and the expectations for geomorphic and habitat change. The feasibility of protecting threatened buildings and roads will decrease in the future as sea level rises and the existing protection structures degrade or fall below new design standards. We suggest that functional buildings with less historic value remain in use until threatened by erosion, but little reason exists to build new structures to protect them. A case is made for allowing developed sites to revert to natural processes to establish a precedent and provide good demonstration areas for promoting stakeholder acceptance of retreat strategies.