TRACKING BARRIER ISLAND EVOLUTION AND THE APPLICABILITY OF CENTIMETER SCALE GPS AND GIS

Hog and Parramore Islands, off the Eastern Shore of Virginia, show rapid change due to storm overwash, tidal inlet dynamics, longshore current and aeolian processes. The magnitude of the changes that these processes cause and the speed with which they work render traditional surveying extremely difficult. Centimeter scale GPS surveys are an alternative to traditional surveying in this environment, and have proven to be a valuable tool for tracking landform evolution and movement, as well as the sediment dynamics on these barrier islands. Survey coverage for this project at Parramore Island begins in 1997 and continues to the present. The Hog island surveys cover the period from 1998 to the present. By importing the GPS surveys into ArcView GIS it is possible to map the islands and to track geomorphic and volumetric changes in the study area. The use of GIS makes several different strategies possible for studying this evolution; horizontal mapping and cross-sections of the study area, tracking of annual elevation change and the tracking of volume change within slices of the study area bounded by elevation. Parramore Island shows rapid shoreward movement early in the study, followed by a period of dune building and stability. Hog Island’s shoreline and dunes remain relatively stable throughout the study. The rate and location of change along with physical data gathered indicates that aeolian processes currently dominate the study areas.