Barrier Island Morphological Change by Bay-Side Storm Surge

Abstract

Barrier island overwash and breaching are caused by inundation from ocean storm surge and waves or from elevated levels of bay water. According to numerical simulations, a developed barrier island in New Jersey experienced major overwash and some breaching during Hurricane Sandy in 2012 as a result of an extreme rise in bay surge within Barnegat Bay 6 h after peak ocean surge. In this study, a sensitivity analysis was conducted on the effects of peak bay-surge timing and magnitude on the morphological change in the presence and absence of a seawall. Results from the numerical model indicate that the timing of the peak bay surge in the northern portion of Barnegat Bay was a major contributor to the damage observed at nearby locations along the barrier island. By shifting bay-surge timing, island erosion was reduced up to 130%, mostly on the back barrier, the location of the majority of coastal infrastructure. Additionally, simulations show that a seawall protected the island from severe erosion by preventing ocean and bay surge from flowing freely across the island. In the absence of a seawall, the elevation of the island was significantly eroded under Hurricane Sandy conditions, where erosion was exacerbated by increases in bay-surge magnitude.