A NEW METHOD FOR EXAMINING THE NATURAL CONTROLS ON THE DITRIBUTION OF HURRICANE OVERWASH: CAPE LOOKOUT NATIONAL SEASHORE, NORTH CAROLINA

The relatively pristine and undeveloped nature of parks can make them excellent control sites for scientific studies. This is particularly true of parks with ocean shorelines. This study examined the impact of a Category 2 hurricane (Isabel) on the northern portion of Cape Lookout National Seashore (CLNS). The primary goals were to document the alongshore variability in overwash and to test possible controls on that variability. This investigation utilized both field and remote sensing data. Pre- and post- storm photography and satellite imagery were gathered for identifying storm features created by Isabel. The critical dataset was collected in the field. Benchmarks were established every .25 miles on North Core Banks. At each site, the landward distance of overwash penetration was measured. In addition, a pit was dug at the terminus of the overwash fan and the overwash thickness was measured. A sediment sample was collected for standard grain size analysis. Finally, an Overwash Energy Factor (OEF) was calculated at each benchmark by combining the overwash penetration, thickness, and mean grain size. The OEF was used as a proxy for cross-shore storm energy during Hurricane Isabel. In general, the OEF increases gradually from south to north (towards the eyewall), but there is considerable variability within that trend. Several conclusions can be drawn from examining the OEF pattern. The highest OEF values, and thus the most storm energy, were found near modern inlets, at old inlet locations, and in areas extremely low pre-storm elevation. The lowest OEF values were found large remnant dunes were present after the storm. We would like to compare the post-storm OEF pattern with the pre-storm dune height and volume pattern as recorded in USGS LIDAR data to examine the “critical” dune height and volume needed to survive Isabel. We did compare the OEF data with State of North Carolina erosion rate maps and found no correlation between historical erosion rates and cross-shore storm energy, a somewhat surprising conclusion. FEMA Flood Insurance Rate Maps were even less useful. The entire shoreline was mapped as the highest risk V-zone, which OEF data indicate that it is not. *( A. Barnes, B. Blair, C. Bochicchio, S. Bonner, G. Bozdog, L. Garland, J. Jarvis, B. Lowder, T. Phillips, K. Stewart, J. Wetzel)