Factors Controlling Longshore Variations of Beach Changes Induced by Hurricane Hermine along Pinellas County Beaches, West-central Florida

Hurricane Hermine, 2016, impacted the coast of west-central Florida and generated high waves superimposed on elevated wave levels which caused significant beach erosion. A total of 122 profiles, spaced about 300 m apart, were surveyed 2 weeks before and one week after the storm to examine the beach changes along three barrier islands along the coast of west-central Florida. including Sand Key, Treasure Island and Long Key. In order to investigates the longshore variations of beach/nearshore changes induced by storm, several parameters were defined and calculated including beach volume changes, berm height, beach width, foreshore slope, as well as sandbar configurations (sandbar height, bar depth, and bar location). At Treasure Island and Long Key, the overall volume gain mainly at the seaward slope of longshore bar is largely equal to the overall volume loss on the dune, dry beach and nearshore, and the volume change represents a largely conserved sand volume above closure depth. The overall sand loss is slightly larger than offshore sand gain at Sand Key. The longshore variation of averaged overall erosion from the dune-beach area represents a general southward decreasing trend, which is consistent with the southward decreasing wave height distribution. Most of the foreshore slope and berm height decreased induced by the storm along all three barrier islands. The only exception occurred at North Sand Key, where berm height increased from the storm, which is induced by overwash from higher storm waves on north Sand Key. The sandbar mostly moved offshore under the storm. Deeper pre-storm sandbar elevation tends to be associated with smaller sandbar elevation changes. Larger pre-storm sandbar height, tend to be associated with decreasing in sandbar height from the storm. The systematically measured beach profiles provide a solid dataset to calibrate process-based models to study beach morphodynamics