THE INFLUENCE OF STORMS AND STRATIGRAPHY ON BARRIER ISLAND EVOLUTION: GULF ISLANDS NATIONAL SEASHORE, GULF OF MEXICO
Rates of shoreline loss over the past 60 years have increased. As with other barrier islands in the Gulf of Mexico, reduced sediment supply, storm-impacts, human alteration of the littoral system, and sea level rise have contributed to their deterioration. In 2005, Hurricane Katrina inundated the islands with a 9-m storm surge that expanded existing breaches, destroyed dunes and forests, and scoured the island margins. Individually, however, the islands are experiencing change at widely different rates, and the role of the underlying stratigraphy on this variability is not well constrained. Since 2007, the U.S. Geological Survey (USGS) in collaboration with the National Park Service, has been mapping the seafloor and substrate around the islands as part of the USGS Northern Gulf of Mexico Ecosystem Change and Hazard Susceptibility project. The purpose of these investigations is to characterize the near-surface stratigraphy and identify the influence it may have on island evolution and fate. This presentation highlights recent findings of these studies, and identifies correlations between the Pleistocene-Holocene stratigraphy and island/inlet morphology.