Simulation of flood hydrographs for Georgia streams

Water-Resources Investigations Report 86-4004



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The O'Donnell method was used to compute unit hydrographs and lagtimes for 355 floods at 80 gaging stations in Georgia. An average unit hydrograph and an average lagtime were computed for each station. These average unit hydrographs were transformed to unit hydrographs having durations of one-fourth, one-third, one-half, and three-fourths lagtime, then reduced to dimensionless terms by dividing the time by lagtime and the discharge by peak discharge. Hydrographs were simulated for these 355 floods and their widths compared with the widths of the observed hydrographs at 50% and 75% of peak flow. The dimensionless hydrograph based on one-half lagtime duration provided the best fit of the observed data. Multiple-regression analysis was used to define relations between lagtime and certain physical basin characteristics. Drainage area and slope were significant for the rural stream equations and drainage area, slope, and impervious area were significant for the Atlanta urban-stream equation. A hydrograph can be simulated from the dimensionless hydrograph, the peak discharge of a specific recurrence interval, and the lagtime obtained from regression equations for any site with a < 500 sq mi drainage area in Georgia. For simulating hydrographs at sites with basins > 500 sq mi, the USGS computer model CONROUT can be used. (Author 's abstract)

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USGS Numbered Series
Simulation of flood hydrographs for Georgia streams
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Water-Resources Investigations Report
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U.S. Geological Survey,
v, 41 p. :ill., maps ;28 cm.