Effects of bulkheads on estuarine shores: An example from fire Island National Seashore, USA

Bayside bulkheads on Great South Bay, New York at Fire Island National Seashore are evaluated to determine their impact on unprotected areas adjacent to them and to identify alternatives for future protection from coastal erosion. Bulkheads extend along about 18% of the 67.3 km-long shoreline. Annual topographic surveys conducted 2004-2008 at four bulkheads and two control sites reveal that annual retreat can be as great as 3.3 m yr^-1 in the upland and 6 m yr^-1 on the foreshore. Local bulkhead-influenced sand starvation appears to extend up to 68 m alongshore. Sand starvation due to bulkheads is only one aspect of the erosion problem. Lack of fresh inputs of sediment to the bayshore by inlets, overwash and dune migration all contribute to shoreline transgression. Beach nourishment can restore the sediment budget in places but should be introduced in a way that minimizes burial of benthic habitat or creation of large scale exotic environments. The inherent dynamism of natural systems and the adaptation of species to this dynamism prevent restoration of landforms or habitats to stable target states. The closest approximation of a "permanent" solution would be to restore the sediment budget by creating feeder uplands by placing fill sediment at about the height of local natural formations and close to bulkhead ends. Dredging of navigation channels appears to provide a ready source of compatible fill.