Streamflow Statistics (StreamStats) Web application for Ohio

"October 2006"--P. [iii].; Also available on the Internet; Adobe Reader required.; Includes bibliographical references (p. 14-15).; Final report.; Ohio Department of Transportation State Job No.134265; Harvested from the web on 4/19/07A StreamStats Web application was developed for Ohio that implements equations for estimating a variety of streamflow statistics including the 2-, 5-, 10-, 25-, 50-, 100-, and 500-year peak streamflows, mean annual streamflow, mean monthly streamflows, harmonic mean streamflow, and 25th-, 50th-, and 75th-percentile streamflows. StreamStats is a Web-based geographic information system application designed to facilitate the estimation of streamflow statistics at ungaged locations on streams. StreamStats can also serve precomputed streamflow statistics determined from streamflow-gaging station data. The basic structure, use, and limitations of StreamStats are described in this report. To facilitate the level of automation required for the StreamStats application, the technique used by Koltun (2003) for computing main-channel slope was replaced with a new computationally robust technique. The new channel slope characteristic, referred to as SL10-85, differed from the National Hydrography Data based channel slope values (SL) reported by Koltun (2003) by an average of -28.3 percent, with the median change being -13.2 percent. In spite of the differences, the two slope measures are strongly correlated. The change in channel slope values necessitated revision of the full-model equations for flood-peak discharges presented by Koltun (2003). Average standard errors of prediction for the revised full-model equations presented in this report increased by a small amount over those reported by Koltun (2003), with increases ranging from 0.7 to 0.9 percent. Mean percentage changes in the revised regression and weighted flood-frequency estimates relative to regression and weighted estimates reported by Koltun (2003) were small, ranging from -0.72 to -0.25 percent and -0.22 to 0.07 percent, respectively.A StreamStats Web application was developed for Ohio that implements equations for estimating a variety of streamflow statistics including the 2-, 5-, 10-, 25-, 50-, 100-, and 500-year peak streamflows, mean annual streamflow, mean monthly streamflows, harmonic mean streamflow, and 25th-, 50th-, and 75th-percentile streamflows. StreamStats is a Web-based geographic information system application designed to facilitate the estimation of streamflow statistics at ungaged locations on streams. StreamStats can also serve precomputed streamflow statistics determined from streamflow-gaging station data. The basic structure, use, and limitations of StreamStats are described in this report. To facilitate the level of automation required for the StreamStats application, the technique used by Koltun (2003) for computing main-channel slope was replaced with a new computationally robust technique. The new channel slope characteristic, referred to as SL10-85, differed from the National Hydrography Data based channel slope values (SL) reported by Koltun (2003) by an average of -28.3 percent, with the median change being -13.2 percent. In spite of the differences, the two slope measures are strongly correlated. The change in channel slope values necessitated revision of the full-model equations for flood-peak discharges presented by Koltun (2003). Average standard errors of prediction for the revised full-model equations presented in this report increased by a small amount over those reported by Koltun (2003), with increases ranging from 0.7 to 0.9 percent. Mean percentage changes in the revised regression and weighted flood-frequency estimates relative to regression and weighted estimates reported by Koltun (2003) were small, ranging from -0.72 to -0.25 percent and -0.22 to 0.07 percent, respectively