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item Sheridan, Joseph

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 12/3/2001
Publication Date: 12/3/2001
Citation: Sheridan, J.M. 2001. Improved peak flow algorithms for coastal plain watersheds. American Society of Agricultural Engineers Meetings Paper No. 01-2116. Sacramento, CA, 13 pp. ASAE, St. Joseph, MI. 2001.

Interpretive Summary: Computer models are now being used to compute storm peak flows and to estimate the amount of pollutants carried in storm runoff from agricultural areas. For greater confidence in the reliability of predictions made by these computer models, the adequacy of prediction equations used in these models should be tested by comparing model estimations to experimental field data when such data are available. In this study, an equation used by a number of current water quality computer models to estimate storm peak flows was tested for applicability in the Coastal Plain region of the southeastern US. Peak flows computed using the equation were compared to storm peaks measured from 58 storms occurring on seven gaged, experimental areas in the Coastal Plain. The equation was found to overpredict storm peaks from the Coastal Plain study areas by an average of over 400%. Improved peak flow equations were developed for use in the southeastern Coastal Plain region. These equations provide more accurate estimation of storm peaks and, as a result, will permit development of computer models that make more accurate estimates of pollutant movement in storm runoff from agricultural areas in the Coastal Plain. The improved capability for modeling storm runoff and pollutant movement is needed for natural resource and environmental planning and management that is required to improve the quality of the nation's streams, rivers, lakes and groundwater supplies.

Technical Abstract: Computer models used to predict hydrologic and water quality responses from ungaged watersheds often rely on empirical algorithms to represent complex processes that are not well-understood or are not easily represented. For greater confidence in model predictive capability, empirical algorithms should be tested before applying in regions where conditions vary from those where algorithms were developed. An empirical peak flow equation used in many hydrologic and water quality models has shown a tendency to overpredict storm peaks in regions of low relief. In this paper, the peak flow equation was evaluated using 58 storm events on seven experimental watersheds in the southeastern Coastal Plain, a region with low-gradient stream systems and extensive riparian storage. The equation overpredicted peak flows on Coastal Plain watersheds with an average error of over 400%. Improved regional peak flow equations were developed relating storm peaks to drainage area, runoff amount and a drainage network parameter, the Melton ratio. The Coastal Plain peak flow equations provide improved methods for estimating storm peaks from ungaged watersheds in the US Coastal Plain, which is essential to accurate, reliable natural resource and environmental modeling.