MONITORING HURRICANE EFFECTS ON AQUIFER SALINITY USING ALSM

ABSTRACT During the Atlantic hurricane season of 2004, the Florida Pan Handle, Gulf Coast region, was impacted directly by three hurricanes within approximately a one-month time period. The short temporal span between impacts coupled with the severity of the storms resulted in drastic changes to the littoral zone geomorphology including extensive shoreline erosion and accretion that directly affected the subsurface hydrogeologic environment. The most important direct physical effects of a hurricane are the following: coastal erosion, shoreline inundation owing to higher than normal tide levels plus increased temporary surge levels during storms, and saltwater intrusion primarily into estuaries and groundwater aquifers. Erosion and deposition during the hurricane change the elevation, which causes change in the position of shoreline. The purpose of this study was to investigate the effects of sea level inundation due to the hurricanes on the near shore subsurface freshwater-saltwater interface. By utilizing high-resolution Airborne Laser Swath Mapping (ALSM) altimetry data acquired shortly before and after the three major hurricane landfalls, the change in shoreline topography was estimated to determine both small-scale and large-scale horizontal encroachment and volumetric change in shoreline. This information was used to develop a before and after variable density groundwater flow model to determine the impact of the hurricanes on the subsurface saltwater-freshwater interface. SEAWAT (Langevin 2001