Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: October 29, 1999
Publication Date: October 29, 1999
Citation: SHERIDAN, J.M., BOSCH, D.D., WILLIAMS, R.G. HYDROLOGIC RESPONSE OF COASTAL PLAIN WATERSHEDS. ASAE ANNUAL INTERNATIONAL MEETING. ASAE #992121. 1999. Interpretive Summary: Watersheds in coastal regions of the southeastern U.S. have long presented difficulties in predicting peak rates of storm runoff. Improved methods are needed for estimating peak runoff or flood flows that result from storms occurring in coastal regions of the southeastern U.S. To develop this information, storm data from experimental watersheds in coastal areas of the southeastern U.S. were evaluated. By analyzing the storm event dat USDA scientists developed a relationship between storm flood peaks and the respective watershed physical characteristics. Results show that simple watershed characteristics (specifically drainage area and stream channel slope) explained most of the differences in observed peak runoff rates between these coastal watersheds. This information will provide a simple tool to permit more accurate estimation of peak flows of floods that result from storm events occurring on flatland watersheds. This information should provide engineers and scientists with improved prediction methods for use in natural resource and environmental quality applications on watersheds in coastal regions of the southeastern U.S.
Technical Abstract: Watersheds with low topographic relief such as in coastal regions of the southeastern U.S. have long been considered problematic for predicting hydrologic response characteristics. Improved hydrologic design and modeling relationships are needed for predicting storm runoff for ungaged watersheds in regions with low-gradient drainage networks. To develop this information, 46 storm events from eight USDA experimental watersheds in the Coastal Plain and Flatwoods regions of the southeastern U.S. were evaluated. Linear regression analyses were performed on log-transformed watershed physical characteristics and watershed mean peak rate factors that were obtained from optimized unit hydrographs for selected storm events. Results indicate that a two parameter model based on watershed drainage area and main channel slope accounted fro 89% of the variation in watershed mean peak rate factor. This relationship, which provides a unique peak rate factor for each watershed based on readily measured watershed characteristics, provides information needed by federal action agencies and others for characterizing the hydrologic response of ungaged, flatland watersheds. This simple relationship is compatible with existing, commonly used hydrologic methodologies and will permit improved hydrologic modeling capabilities currently needed for natural resource and environmental quality applications on low-gradient watersheds such as in coastal regions of the southeastern U.S.