AN INTEGRATION OF REMOTE-SENSING AND GIS TO EXAMINE THE RESPONSES OF SHRUB THICKET DISTRIBUTIONS TO SHORELINE CHANGES ON VIRGINIA BARRIER ISLANDS

The high-water-shoreline positions in 1852, 1871, 1910, 1919, 1943, 19 55, 1967, 1980, and 1990 for Hog Island, a barrier island located at t he eastern shore of Virginia, were determined with the NOS T-sheets an d aerial photographs. Shrub thicket distributions for northern Hog Isl and were extracted from black/white and infrared: color aerial photogr aphs for the years of 1949, 1962, 1974, and 1989. The overlay operatio ns between shrub age and land age data layers indicated that shrub cov erage on Hog Island was closely related with shoreline changes. By exa mining 138-year shoreline changes on 50-m-interval transects of Hog Is land, it was found that the sine function could describe shoreline cha nge patterns better than earlier used simple models. The overlay betwe en old NOS T-sheets and 1993 TM satellite image suggested that there w ould be at least three types of shoreline changes for different barrie r islands. All these three types of shoreline change patterns could be interpreted with the sine function model. The potential distribution of shrub thickets on Hog Island was simulated based on the shoreline c hange model. The shrub line and shoreline positions were closely relat ed with each other, but there were time lags between shrub thicket exp ansion and shoreline accretion.