ASSESSING BARRIER ISLAND VULNERABILITY TO EXTREME GEOMORPHIC CHANGES DURING HURRICANES

Along much of the East and Gulf Coasts of the United States, hurricanes have been responsible for some of the most dramatic changes to beaches – from the creation of large overwash deposits to the opening of new inlets. These changes can have a profound impact on coastal ecosystems and man-made structures and may increase coastal vulnerability during future storms. Through extensive observation and modeling of storm-induced beach evolution, the U.S. Geological Survey has developed a research program to assess the vulnerability of sandy beaches to extreme geomorphic changes during hurricanes.

The response of sandy barrier islands to storms is dependent, in part, on the interactions between beach morphology and offshore oceanographic forcing. Accurate, high-resolution surveys of pre-storm morphology (e.g. beach slope, dune height, beach width) combined with model predictions of the total hurricane-induced water level (surge and waves) provide a means to forecast the type of coastal change that may be expected during a storm. Near-real-time predictions made during approaching hurricanes are used to focus post-hurricane response efforts and to inform the public and emergency responders of possible post-storm conditions. Combined with extensive topographic surveys of the actual beach response, these short-term nowcasts are used to evaluate predictive accuracies and capabilities for longer-term assessments of vulnerability to future storms. Probabilistic modeling of the interactions between a range of hurricane scenarios and long-term profile evolution can be used to assess areas of our Nation's coasts that are more susceptible to extreme storm-induced change.