ALONGSHORE VARIATION IN DUNE MORPHOLOGY AND STORM IMPACT IN NATIONAL SEASHORES DEPENDS ON THE CORRESPONDENCE OF TRANSPORT POTENTIAL AND SEDIMENT SUPPLY

The height and extent of coastal dune recovery following extreme storms can exhibit considerable variability over short distances, leading to variable storm impact alongshore in National Seashores. The source of this variation is not well understood in general, and is not easily explained by contemporary dune models that ascribe dune height and development to regional variations in sediment availability and beachface slope. In this paper, LiDAR data from the Gulf Islands and Padre Island National Seashore are used to characterize the alongshore variation in dune morphology, and to identify how the variation is related to beach morphology and nearshore state. It is shown that the variation in dune morphology and storm impact in these parks is dependent on the alongshore correspondence of sediment supply and transport potential, which varies with the beach and nearshore state. It is further argued that dune development in the Gulf Islands National Seashore is transport limited by the reflective beachface, while in Padre Islands National Seashore, dune development is supply limited. In this respect, different post-storm management and development strategies are required to ensure dune resiliency.