Equations, applicable statewide, for estimating flood magnitudes having recurrence intervals ranging from 2 to 500 years for unregulated rural streams, with drainage areas ranging from 0.02 to 10,000 square miles (0.05 to 25,900 square kilometers), were derived by multiple regression analyses. A rainfall-runoff model was used in the synthesis of long-term annual peak data for each of 54 small watersheds (drainage areas less than 10.2 sq mi, 26.4 sq km). Synthetic frequency curves generated from five long-term precipitation stations were combined into one synthetic curve and then this synthetic curve was combined with the observed station frequency curve to define the station frequency curve. Synthetic data from the 54 small streams, observed data at 33 small streams, and observed data at 154 large streams were used in the analyses. The most significant independent variables in the regression analysis for estimating flood peaks on Illinois streams were drainage area, slope, rainfall intensity, and an areal factor.

  • Supplemental Notes:
    • Prepared in cooperation with Illinois State Div. of Highways, Springfield.
  • Corporate Authors:

    U.S. Geological Survey

    F Street Between 18th and 19th Street, NW
    Washington, DC    20244

    Illinois Department of Transportation

    Division of Highways, 2300 South Dirksen Parkway
    Springfield, IL  United States  62764
  • Authors:
    • Curtis, G W
  • Publication Date: 1977-7

Media Info

  • Pagination: 40 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00175897
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: USGS/WRI-77-104 Final Rpt.
  • Files: TRIS
  • Created Date: Jun 28 1978 12:00AM