Application of the U.S. Geological Survey rainfall-runoff simulation model to improve flood-frequency estimates on small Tennessee streams

The U.S. Geological Survey rainfall-runoff simulation model was used in conjunction with National Weather Service climatological data to improve flood-frequency estimates for 52 small drainage basins in Tennessee. The basins range in size from 0.17 to 64 square miles (0.44 to 166 square kilometers) and are distributed throughout the State. Model parameters were determined by calibration with observed data from each site. Average error of peak discharge simulation was about 36 percent. Techniques used in screening data for calibration as well as those used to optimize parameter values are discussed. A scheme developed to assess the relative accuracy of the frequency curves based on observed and simulated data indicated that the simulated data are equivalent to nine years of observed data in defining 2-year floods, and fifteen years in defining 100-year floods. Discharges corresponding to the best estimate of flows for selected recurrence intervals are tabulated for each modeled basin. (Woodard-USGS)