Scientific Investigations Report 2006–5312

A Streamflow Statistics (StreamStats) Web Application for Ohio

By G. F. Koltun, Stephanie P. Kula, and Barry M. Puskas

Abstract

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 Ohio’s StreamStats application, the technique used by Koltun (2003)1 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)1 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 resulting from the change in computational method necessitated revision of the full-model equations for flood-peak discharges originally presented by Koltun (2003)1. 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)1, 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)1 were small, ranging from -0.72 to -0.25 percent and -0.22 to 0.07 percent, respectively.


1Koltun, G.F., 2003, Techniques for Estimating Flood-Peak Discharges of Rural, Unregulated Streams in Ohio, Second Edition: U. S. Geological Survey Water-Resources Investigations Report 03-4164, 76 p


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Contents

Abstract

Introduction

Purpose and Scope

Methods

Processing of Geospatial Datasets

Physical and Hydrologic Setting

Determination of Channel Slope

Generalized Least-Squares Regression Analysis

StreamStats

Limitations

Acknowledgments

References

Summary


Appendix A. Statistical techniques for determining confidence intervals and testing for extrapolation

Appendix B. Basin characteristics used as regressor variables


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Send questions or comments about this report to the author, G.F. Koltun, at gfkoltun@usgs.gov

For more information about USGS activities in Ohio, visit the USGS Ohio Water Science Center home page.



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