U.S. Geological Survey
Open-File Report 02-494

A Geographic Information System Tool to Solve Regression Equations and Estimate Flow-Frequency Characteristics of Vermont Streams

By Scott A. Olson, Gary D. Tasker, and Craig M. Johnston


Estimates of the magnitude and frequency of streamflow are needed to safely and economically design bridges, culverts, and other structures in or near streams. These estimates also are used for managing floodplains, identifying flood-hazard areas, and establishing flood-insurance rates, but may be required at ungaged sites where no observed flood data are available for streamflow-frequency analysis. This report describes equations for estimating flow-frequency characteristics at ungaged, unregulated streams in Vermont.

In the past, regression equations developed to estimate streamflow statistics required users to spend hours manually measuring basin characteristics for the stream site of interest. This report also describes the accompanying customized geographic information system (GIS) tool that automates the measurement of basin characteristics and calculation of corresponding flow statistics. The tool includes software that computes the accuracy of the results and adjustments for expected probability and for streamflow data of a nearby stream-gaging station that is either upstream or downstream and within 50 percent of the drainage area of the site where the flow-frequency characteristics are being estimated. The custom GIS can be linked to the National Flood Frequency program, adding the ability to plot peak-flow-frequency curves and synthetic hydrographs and to compute adjustments for urbanization.


Estimating Flow-Frequency Characteristics of Unregulated, Ungaged, Rural Vermont Streams
Regression Equations
Allowable Range of Basin Characteristics for Use in the Regression Equations
Standard Error of Residuals and Prediction of the Regression Equations
Equivalent Years of Record of Results of the Regression Equations
Prediction Intervals of Results of the Regression Equations
Vermont Flow-Frequency Tool
System Requirements
Data Requirements
Installation of the Vermont Flow-Frequency Tool
Using the Vermont Flow-Frequency Tool
Additional Utilities of Vermont Flow-Frequency Tool
Vermont Flow-Frequency Tool Options Menu
Use of Regression Equations at or near Stream-Gaging Stations
Expected Probability Adjustment to Flood Discharges
National Flood Frequency Program
Selected References
Appendix 1. Use of Regression Equations with Metric Units
Selected References

This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.

Download the report (PDF, 1.0 MB)

Geographic Information System files needed for the Vermont Flow-Frequency Tool click here(ZIP, 3.7 MB)

For NHD data sets needed to run the GIS Tool and the watershed support files, click on URL

To obtain a PDF file of the companion report to this OFR, click here for Water-Resources Investigations Report 02-4238, titled " Flow Frequency Characteristics of Vermont Streams

To download Vermont Flow Frequency GIS Tool, click here

Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.

Send questions or comments about this report to the author, Scott A. Olson ( 603.226.7815.

For more information about USGS activities in Vermont, visit the USGS New Hampshire-Vermont District home page.

U.S. Department of the Interior, U.S. Geological Survey
Persistent URL:
Page Contact Information: Contact USGS
Last modified: Wednesday, December 07 2016, 07:03:47 PM
FirstGov button  Take Pride in America button