Morphologic Evolution of a Nearshore Berm: One Year Monitoring at Ft. Myers Beach, Florida
Enfinger, Kristopher Jason
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Nourishment in the form of a nearhsore berm has become an important alternative method to protecting shorelines and introducing sediment back into the littoral system. In 2009, a nearshore berm was constructed at Ft. Myers Beach, Florida by the U.S. Army Corps of Engineers through maintenance dredging of a nearby navigational channel at Matanzas Pass. Constructed in the form of a nearshore bar, the berm was one of the shallowest placements in a low-wave energy setting. The Coastal Research Lab at the University of South Florida (USF-CRL) conducted field monitoring for the first four years after the construction. This project discussed herein is a continuation of the previous study. In order to develop an effective coastal management strategy for the Ft. Myers Beach area, this study uses a combination of field techniques and remote sensing techniques to quantify morphological changes over the one-year study period and long term shoreline trends. Seventy-two transects were surveyed four times over the study period from the base of the dune out to -10 ft. In order to determine the dynamic equilibrium of the study area, 2D and 3D morphological analysis was conducted on the profiles. During the study period, Hurricane Irma impacted the study area and generated high waves and wind for the study area. Historical Light Detection and Ranging (LiDAR) from 1998, 2004, 2006, 2007, 2010, 2012, and 2015 is used to extract shorelines. Using an ArcGIS extension, Digital Shoreline Analysis System (DSAS v.4.4), rates-of-change statistics were calculated for the multiple shorelines. End point rate calculations show a consistent transgression of the shoreline with the greatest movement in the northwestern end of the study area, >13 ft./yr. From the field techniques and remote sensing techniques, results indicate the southern portion of the berm area is the most stable and dissipated wave energy during the high energy events. Monitoring should be continued to evaluate when the natural equilibrium profile will fully recover and the stabilization of the nearshore feature.