Morphodynamics of the Isles Dernieres barrier shoreline, Louisiana. 1984-1989

Abstract

An aerial videotape mapping system was used to monitor spatial and temporal variability of the coastal morphology along the Isles Dernieres barrier shoreline. Between 1984 and 1989, nine sequential annual and post-hurricane aerial videotape surveys were flown covering periods of prolonged fair weather, hurricane impacts, and subsequent post-storm recovery. Morphologic time series were developed to depict spatial and temporal geomorphic changes along the Isles Dernieres low-profile transgressive barrier island system. The net effect of Hurricanes Danny and Juan, in 1985, was the transformation of a high relief landscape dominated by well-vegetated dunes, dune terraces, and washover terraces to one dominated by partially-vegetated washover terraces and unvegetated washover flats. In 1988, Hurricane Gilbert caused extensive geomorphic changes in the central Isles Dernieres where the low-relief, less-vegetated islands were more susceptible to storm-surge processes. Post-storm island morphodynamics were characterized by a gradual build up of the low-relief landforms to high-profile features. The greatest post-storm recovery consistently occurred in areas of greater island width and relief. In addition, the rate of post-storm recovery was controlled by the regional setting of individual islands relative to sand supply. The degree of post-storm recovery was consistently greater in areas where hurricane impact had caused greatest geomorphic change.