Evolution of Large Scale Three Dimensional Coastal Features During Hurricanes Using Bathymetric Lidar

In this study we have examined a subset of airborne lidar bathymetry for a 200 km section of Gulf of Mexico shoreline (Baldwin County, Alabama to Walton County, Florida). We concentrated upon the evolution of large scaled bar morphology during the high energy hurricane conditions at this area when these features can be rearranged in a matter of hours. We performed the analysis at four conditions: before the hurricane Ivan landfall (April-May, 2004), after hurricane Ivan (November-December, 2004), after hurricane Dennis (July, 2005) and finally after hurricane Katrina (November-December, 2005). Before hurricane Ivan at our study area we observed large scaled well developed rhythmic bar formations. They were progressively and partially or completely destroyed by hurricane Ivan, Dennis and Katrina. Quasi linear bars formed in place and bars moved offshore. We computed different bar characteristics (wavelength, extent, crest and trough elevations and cross-shore distances) to study the changes in formation patterns and length scales of the bar morphology at pre Ivan and post hurricane conditions. We analyzed the wave height data for normal and extreme climatic condition and concluded that large hurricane wave heights yields high energy and hence play a significant role in the evolution of bar morphology during extreme climatic (hurricane) conditions.