Challenge. Quantify potential erosion and toe scour to aid in fast-track design of seawall proposed in response to erosion caused by Hurricane Sandy and the Thanksgiving Day storm

Solution. In fall 2012, Hurricane Sandy undermined sidewalks, an existing decorative wall along State Road A1A, and portions of the roadway. To support the installation of an emergency steel sheet pile seawall along this damaged section of roadway, INTERA quantified potential beach erosion and toe scour during storm events to aid in design of the proposed seawall. We also examined beach fill alternatives to quantify benefits and the reduction of scour at the wall. INTERA examined historical shoreline behavior; developed representative beach profiles; applied the United States Army Corps of Engineers (USACE) cross-shore erosion model, SBEACH, to evaluate storm-induced scour for 10-, 20-, 50-, and 100-year storms; and determined local scour at the seawall for selected wall design lives. Concurrently, INTERA examined minimum (defined by permitting agencies) and desired (defined by client) beach fill templates to quantify their effects on reducing scour at the seawall to support environmental permitting. Qualitative analyses included beneficial effects of beach fill on reducing wave damage potential to upland infrastructure and possible detrimental effects of no beach fill on fronting and adjacent beaches. We also delineated a potential upland source of beach fill material. The permitting agencies approved our analyses without revision.