FORMING A PREDICTIVE MODEL FOR BARRIER ISLAND HYDROLOGY FROM GEOMORPHOLOGICAL CLUES

As one of the few undeveloped coastal barrier island complexes on the Atlantic Coast, Assateague Island National Seashore can provide an accurate representation of Mid-Atlantic barrier island dynamics and hydrology. Historical records and modern aerial photography, along with ground observations, allow a strong link to be drawn between the geomorphology and hydrology of the island. The use of historical maps and photos allow the dating of specific features on the island and help to create a reference timescale. The complete overwashing of the island by two large storms during the last century also assists in developing the time frame for individual features of the geomorphology. Using LIDAR and Color Infrared Photography, the island was divided into simple geomorphologic units with distinct characteristics and properties for each. Field work performed on the island characterized the interactions of the surface and subsurface hydrology. Ground Penetrating Radar, resistivity, well logs, and pond observations show a clear link in the hydrology and geomorphology of the island. The data implies that in reality the geomorphology controls and directs the hydrology of the island, resulting in a far different interaction of the freshwater-saltwater interface than is predicted by current models. Through an understanding of this correlation, predictive maps of the hydrogeology of this and other barrier islands along the coast can be made from a working geomorphic map.