FLOOD-TIDE DELTAIC WETLANDS - DETECTION OF THEIR SEQUENTIAL SPATIAL EVOLUTION

Techniques to detect evolution of marsh islands in Great Egg Harbor Ba y, New Jersey are presented in this paper. Aerial photographs and topo graphic maps were digitized. A geographic information system (Gls) was subsequently established with the digitized data. A computer program was also written to carry out necessary computations. Through these ef forts, change in area, shift of centroid, and rotation of marsh island s were quantified. It was revealed that (1) over the recent 51-year pe riod (1940-1992), the areal loss of the entire group of islands has am ounted to slightly under 5 percent, and most individual islands have t he same trends of decrease in area; (2) the centroid of the entire gro up of islands has shifted northeastward, 333 feet to the east and 202 feet to the north, but the trends of individual islands vary; and (3) the entire group of marsh islands has retained its general orientation through the period; however, some individual islands have rotated dra matically These features of marsh island evolution are important to ma intenance of navigation channels because they affect the width of chan nels between the islands and the spatial distribution of sedimentation . These features of marsh island evolution also need to be known for m anagement of the coastal ecosystem because they are indicators of stab ility of biological habitats.