| In this restoration feasibility research for Onondaga Creek, New York the effect of removing a 20-meter high rolled earth dam was evaluated using the TR-20 rainfall-runoff-routing model. Unique to this study is automated calibration with PEST software and incorporation of NEXRAD rainfall data into TR-20. Rainfall recurrence intervals of 2 through 100 years for 24-hour storms were applied to the watershed and the resulting discharge was compared with regional regression estimates for unregulated basins. Darn removal impacts were investigated for partial dam removal and full dam removal. With dam removal, the 10-, 25-, 50-, and 100-year precipitation events under rain-on-snow conditions generated discharge near or in excess of channel capacity. Restoration design would need to consider compound channel design to permit more frequent bankfull flows and to contain the FEMA determined 100-year flows. Removal of the dam resulted in a 200% increase in the 100-year peak discharge. |
