Revised techniques for estimating magnitude and frequency of floods in Montana
Open-File Report
81-917
By: Charles Parrett and R. J. Omang
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Abstract
Relations for estimating the flood magnitudes for ungaged sites in Montana have been updated. The State was divided into eight regions and separate multiple-regression equations for each region were developed that relate logarithms of annual flood magnitude to logarithms of basin characteristics for exceedance probabilities of 50, 20, 10, 4, 2, and 1 percent. The standard errors of estimate for an exceedance probability of 1 percent ranged from 39 to 58 percent in the western and central parts of the State and from 47 to 83 percent in the eastern part. The standard errors of estimate indicate a substantial improvement over previous studies. Techniques for transferring annual flood-frequency information at gaged sites to ungaged sites on the same stream have been updated. Included are curves relating flood-frequency information to drainage area for eight major streams in the State. Maximum known flood peaks in Montana are compared with estimated 1-percent-chance flood peaks and with national maximum known flood peaks. Values of flood discharges for selected exceedance probabilities and values of significant basin characteristics for all gaging stations used in the analysis are tabulated. Included are data for 339 stations in Montana and 34 nearby stations in Canada and adjoining States. (USGS)
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Revised techniques for estimating magnitude and frequency of floods in Montana |
| Series title | Open-File Report |
| Series number | 81-917 |
| DOI | 10.3133/ofr81917 |
| Edition | - |
| Year Published | 1981 |
| Language | ENGLISH |
| Publisher | U.S. Geological Survey, |
| Description | iv, 70 p. ill., maps ;28 cm. |
| Google Analytic Metrics | Metrics page |