by Charles R. Gamble
This report is available as a pdf below
A dimensionless hydrograph developed for a variety of basin conditions in Georgia was tested for its applicability to streams in East and West Tennessee by comparing it to a similar dimensionless hydrograph developed for streams in East and West Tennessee. Eighty-three observed hydrographs in East Tennessee and 38 in West Tennessee were used in the study. Statistical analyses were performed by comparing simulated (or computed) hydrographs, derived by application of the Georgia dimensionless hydrograph, and dimensionless hydrographs developed from Tennessee data, with the observed hydrographs at 50 and 75percent of their peak flow widths. Results of the tests indicate that the Georgia dimensionless hydrograph is virtually the same as the one developed for streams in East Tennessee but that it is different from the dimensionless hydrograph developed for streams in West Tennessee. Because of the extensive testing of the Georgia dimensionless hydrograph, it was determined to be applicable for East Tennessee, whereas the dimensionless hydrograph developed from data on West Tennessee streams was determined to be applicable for West Tennessee.
As part of the dimensionless hydrograph development, an average lagtime in hours, for each study basin, and the volume in inches, of flood runoff for each flood event were computed. By use of multiple-regression analyses, equations were developed that relate basin lagtime to drainage area size, basin length, and percent impervious area. Similarly, flood volumes were related to drainage area size, peak discharge, and basin lagtime. These equations, along with the appropriate dimensionless hydrograph, can be used to estimate a typical (average) flood hydrograph and volume for recurrence-intervals up to 100 years at any ungaged site draining less than 500 square miles in East or West Tennessee.
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