A comparison of modeled flood characteristics to measurements of the 2002 flood on the Guadalupe River, Texas

摘要

There are a number of equations and models for calculating flood probabilities and associated peak discharges, and this paper compares a model and an empirical calculation. We calculated flood characteristics for the upper Guadalupe watershed in central Texas using the Weibull formula and data available from a local gauging station, to the result given by the National Flood Frequency (NFF) program, developed by the U.S. Geological Survey (USGS). During the summer of 2002, the upper Guadalupe watershed received a total of 89 cm (35 in.) of precipitation over a one-week period, producing record flooding. The results from both the NFF program and the calculation of return intervals using gauging station data are compared to the measured peak flows for the summer of 2002. The peak discharges predicted by both the NFF model and from the USGS gauging station data are much higher than the recorded discharge. There may be an increase of flow inputs to the Guadalupe River between the locations of the gauging station and where the flood estimate was made. Assuming an increase from tributaries into Canyon Lake, the estimate of peak discharge obtained from USGS data much more closely matches the recorded flow than the results from the NFF program.