Study of Some Effects of Urbanization on Storm Runoff From A Small Watershed

The evaluation of the effects of urbanization on the runoff characteristics of a small watershed is a problem that can be studied by either a short-range or a long- range investigation. Because the long-range type of investigation would require several years for hydrologic data accumulation, it cannot provide any immediate information on the changes in watershed behavior arising as a result of urbanization. A short-range investigation, however, based on synthetic evaluation of present data would provide immediate answers. It is in the realm of this short-range objective that this study of a small urban watershed is directed. This study was made to evaluate the various effects of urbanization on the hydrologic characteristics of a small urban watershed located within Austin, Texas. A linear regression analysis o f data from twenty-four urban and eleven rural watersheds was used to derive equations which would evaluate the past rural conditions and predict future urban conditions for the Waller Creek watershed. The Waller Creek watershed contains two streamflow stations. One i s located at 38th Street and the other at 23rd Street, gaging areas of 2.31 square miles and 4.13 square miles respectively. The watershed above 38th Street is relatively undeveloped when compared to the lower portion of the watershed located between the two stations. The lower portion has extensive residential development and some channel improvement. Results indicate that urban development in the Waller Creek watershed has caused extensive changes in the discharge hydrograph and runoff for the watershed. Prediction of the effects of future development indicate the same trend. The time sequence of the discharge hydrograph will be shortened, the peak discharge will be increased and the unit (in/mi^2) will be increased.