Estimating Flood Frequency in Gaged and Ungaged Watersheds

Proceedings of the 1999 Georgia Water Resources Conference, March 30 and 31, Athens, Georgia.Estimation of flood frequency is important in jurisdictional wetlands determination and functional assessment, stream classification and restoration, and in assessing urban and agricultural risk in flood prone areas. For example, in utilizing the hydrogeomorphic approach (HGM) for wetland functional assessment for riverine wetlands, the flood frequency variable is required in seven of the suite of fifteen functions. However, site-specific determination of flood frequency has been difficult, especially in ungaged watersheds. One promising method is development of regional dimensionless rating curves. The curves are derived from stage/discharge and channel geometric relationships associated with gaged watersheds. Once the curves are constructed and calibrated to a specific region, flood frequency and channel geometry can be estimated at any point within ungaged as well as gaged watersheds within that region. This method was employed to calibrate the flood frequency variable in the low gradient, riverine HGM guidebook applicable to Western Kentucky. Flood frequency and discharge were determined at several riverine reference wetlands for the purpose of assessing wetland function throughout the Western Kentucky Coalfield Physiographic Region.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202 with partial funding provided by the U.S. Department of Interior, geological Survey, through the Georgia Water Research Insttitute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-397). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors