MORPHOLOGICAL CHANGES ASSOCIATED WITH TROPICAL STORM DEBBY IN THE VICINITY OF TWO TIDAL INLETS, JOHN'S PASS AND BLIND PASS, WEST-CENTRAL FLORIDA

Tropical Storm Debby impacted the west-central Florida coast during three days from June 24^th to June 26^th, 2012. Debby generated sustained high waves and elevated water level over an extended period of time, and subsequently induced tremendous morphological changes. This study examines the morphology changes in the vicinity of two heavily anthropogenically structured tidal inlets, John’s Pass and Blind Pass, in west-central Florida. John’s Pass is a mixed-energy inlet with a large ebb delta skewed to the south. Blind Pass is a stabilized wave-dominated inlet with a small, developing ebb delta. Specifically, morphology changes over the ebb tidal deltas and surrounding beaches are quantified through pre-storm and post-storm topographic and bathymetric surveys. The studied coast is characteristic of micro-tidal inlets with low wave energy. The regional annual net longshore sediment transport is toward the south, driven by frequent passages of winter cold fronts. TS Debby approached from the south, and in addition to creating generous cross-shore directed sediment transport, it induced substantially elevated longshore sediment transport toward the north, opposite to the regional trend. The extended high waves, elevated water level, and northward-directed forcing associated with Debby induced abnormal morphology changes, as compared to the longer-term changes controlled by southward longshore transport. Beaches to the north of the inlets were eroded much more severely by Debby. In comparison, beaches to the south of the inlets that typically have chronic erosion problems were eroded relatively less severely than expected. Debby also differed from other tropical storms in that it affected the study area for an extended period of time, prolonging its influence on the region. Initial data analysis indicates that the southern portion of the ebb deltas generally gained sand, while the northern portion of the ebb deltas lost sand.