Rainfall-Runoff Modeling for Improved Peak Flow Estimates in the Black Hills Area of South Dakota

2017PDFTech ReportSD2013-03-FContract or Grant No. 311193Work Unit No. HRY303RainfallRunoffDrainagePeak dischargeHydrologic phenomenaSurface drainageRainfall-runoffpeak-flowhydrologicmodelsBlack HillsSouth DakotaSouth DakotaUnited StatesSouth Dakota. Dept. of Transportation. Office of ResearchHoogestraat, GalenGeological Survey (U.S.)South Dakota. Dept. of Transportation. Office of ResearchUS Transportation CollectionPeak-flow frequency estimates in the Black Hills area of South Dakota are complicated by the occurrence of extreme flood events that do not fit typical statistical distributions. Alternative methods such as a mixed population analysis have been used to help incorporate high-outlier peak-flow events in frequency analyses; however, more information may be needed to help define areas where causal factors for extreme peak-flow events are different than areas where extreme peak-flow events are less common. A rainfall-runoff modeling approach was applied to 18 drainage basins in the Black Hills with a goal of improving future peak-flow frequency estimates. Rainfall-runoff models were developed using the U.S. Army Corps of Engineers\u2019 HEC-HMS software. These event-based hydrologic models were calibrated to several rainfall events that occurred during 2010\u20132013, and some models also used calibration information from the catastrophic 1972 Black Hills flood event. After the HEC-HMS basin models were calibrated, hypothetical storm scenarios were developed to examine the effects of large runoff events over the Black Hills area. Outputs used from the hydrologic models to assess peak-flow characteristics include normalized peak flows and yield efficiency. Normalized peak flows demonstrate a tendency for lower flood risk in the upper parts of the Spring, Rapid, and Spearfish Creek drainage basins, generally corresponding with the location of the Limestone Plateau on the western flank of the Black Hills. Conversely, the middle sections of Elk, Boxelder, and Rapid Creeks along the eastern downslope flank of the Black Hills show the highest normalized peak flow areas. The same general findings are in previous reports on peak flow potential and flooding in the Black Hills area, but a key benefit of this modeling project is that these characterizations previously supported mainly by recorded streamflow history are confirmed using parametric hydrologic models. Application of a rainfall-runoff modeling approach shows some utility in estimating peak-flow characteristics in the Black Hills, but largely results in confirmation of previously reported characterizations. The spatial distribution of normalized peak flows produced from this research helps delineate regions (eastern flanks) where mixed-population analyses should be required and other regions (western Limestone Plateau area) where standard Bulletin 17B procedures may be appropriate