Techniques for simulating flood hydrographs and estimating flood volumes for ungaged basins in central Tennessee

A dimensionless hydrograph developed for a variety of basin conditions in Georgia was tested for its applicability to central Tennessee streams by comparing it to a similar dimensionless hydrograph developed for central Tennessee streams. Statistical analyses were performed by comparing simulated (or computed) hydrographs, derived by application of the Georgia-study dimensionless hydrograph and the central Tennessee dimensionless hydrograph, with 163 observed hydrographs from 38 stations having a wide range of drainage area sizes and basin conditions, at 50% and 75% of their peak flow widths. Test results indicate the two dimensionless hydrographs are essentially the same. Using the Georgia-study dimensionless hydrograph, the standard error of estimate was +/-21.2% at the 50% of peak flow width and +/-24.8% at the 75% of peak flow width. Study results indicate the Georgia dimensionless hydrograph is applicable to central Tennessee streams. Equations for rural and urban basin lagtime were derived from multiple-regression analyses that relate lagtime to physical basin characteristics. At the 95% confidence level, channel length was significant for the rural basin equation and channel length and percentage of impervious area were significant for the urban basin equation. A regression equation that related flood volumes to drainage area size, peak discharge , and basin lagtime also was developed. The flood-hydrograph and flood-volume techniques are useful for estimating a typical (average) flood hydrograph and volume for any specified recurrence interval peak discharge at any ungaged stream site draining areas less than 500 sq mi in central Tennessee. (Author 's abstract)