Peak Discharge Under Different Rain Events

The peak discharge of the watershed area under 2 years, 10 years, 25 years, 50 years and 100 years rain were simulated in the HEC-HMS program, using NOAA’s Point Precipitation Frequency Estimates for the Pierre region of South Dakota. The storm duration in this analysis is 1 day under 1, 2,3,6,12 and 24 hours increment. The SCS curve number method was used to determine loss while SCS Unit Hydrograph method was used to transform the unit hydrographs in the analysis. From the previous study, a curve number of 87 was determined for the model. The area of the watershed was calculated to be 0.61 square miles while the average basin slope was calculated to be 2.08. A lag time of 57 minutes was also identified.

Rain EventPeak Flow
2 years123.5 CFS
10 years298.5 CFS
25 years409.4 CFS
50 years497.8 CFS
100 years589.9 CFS