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 Stream-Stats 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 SL 10-85 , 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.

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