| Regression equations predicting Clark Synthetic Unit Hydrograph (SUH) parameters for time of concentration (tc) and storage coefficient (R) are developed for small watersheds across Indiana [drainage areas = 3-38 square miles (mi2)]. The state is partitioned into three regions: North, Central, and South, with consideration for past regionalization studies of Indiana and geomorphology. The equations are derived using multiple linear regression analysis for 30 watersheds with 90 observed rainfall-runoff events. Clark SUH parameters are optimized using Hec-HMS to match the observed rainfall-runoff events. The optimized Clark SUH parameters are related to geomorphologic parameters estimated using geographic information system (GIS) applications. An extensive list of 29 geomorphologic parameters is considered including parameters related to depression storage, slope, drainage area, basin shape, and stream network. Separate regression equations for tc and R are developed for each region and the entire state. Values for tc and R are predicted using the regression equations and used to model 7 new rainfall-runoff events in Hec-HMS for comparison to the NRCS SUH method. |
