Hydrographic Changes within South Texas, a Historical Perspective Using GIS

During the last century, a variety of anthropogenic and natural events have modified the hydrography of South Texas. While it is difficult to determine the natural causes of change, anthropogenic sources are largely attributable to the expansion of agriculture, transportation infrastructures, urban areas, and sea ports. A set of United States Geologic Survey (USGS) maps of the area generated in1929, 1935, 1955, and 1983, were collected in order to perform a comparative analysis of hydrologic features throughout the region over the last century. Historical maps were geo-referenced within ArcGIS, and the study area was defined. Maps were then split into two classifications landmass and water inundation. A present day measure was obtained using the 2001 National Land Cover Database. Water inundation is represented using the open water classification, and landmass was represented by pooling the existing classifications together, since they represent landmass. Areas of both water inundation and landmass were then computed using Spatial Analyst for each time interval and comparisons were made. The study highlights the immense loss and reduction of water features to the South Texas landscape from the development of the region over time, especially, in the coastal regions where the majority of change has occurred.