Variations in Nearshore Bar Morphology: Implications for Rip Current Development at Pensacola Beach, Florida from 1951 to 2004
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In 2002, Pensacola Beach was identified by the United States Lifesaving Association as being the most hazardous beach in the continental United States for beach drowning by rip currents. Recent studies suggest that the rip currents at Pensacola Beach are associated with a transverse bar and rip morphology that develops with the migration of the bars and recovery of the beachface following an extreme storm. Combined with an alongshore variation in wave forcing by transverse ridges on the inner-shelf, the bar cycle (of bar response and recovery to extreme storms) is hypothesized to create both rip current hotspots and periods of rip activity. However, it is unknown at what stage, or stages, the bar cycle is associated with the formation of these hotspots and the greatest number of rips. To determine how the accretional rip hazard varies in response to the nearshore bar cycle, this thesis will quantify the alongshore variation in the nearshore bar morphology on Santa Rosa Island from 1951 to 2004. Aerial photographs and satellite images are collected for the study area and nearshore features are digitized in ArcGIS and evaluated using wavelet analysis. Specifically, a continuous wavelet transform is used to the identify times and locations when a transverse bar and rip morphology is present or is in the process of developing. The findings suggest that the rip-scale variation in bar morphology (~100-250m) is superimposed on an alongshore variation consistent with the scale of the transverse ridges (~1000m). From the outer bar to the shoreline, and as the bar migrates landward, the variation becomes increasingly dominated by the rip-scale variation. Hotspots of rip current activity were found consistently between years at Fort Pickens Gate, San Souci, Holiday Inn, Casino Beach, Avenida 18 and Portofino, as clusters of rip-scale variation.
Barrett, Gemma Elizabeth (2011). Variations in Nearshore Bar Morphology: Implications for Rip Current Development at Pensacola Beach, Florida from 1951 to 2004. Master's thesis, Texas A&M University. Available electronically from