Stream-Profile Analyses Using a Step-Backwater Model for Selected Reaches in the Chippewa Creek Basin in Medina, Wayne, and Summit Counties, Ohio

摘要

The U.S. Geological Survey, in cooperation with the Chippewa Subdistrict of the Muskingum Watershed Conservancy District, performed hydrologic and hydraulic analyses of selected reaches of three streams in the Chippewa Creek basin in Medina, Wayne, and Summit Counties, Ohio to aid in the assessment of alternatives for channel improvements for mitigating flood hazards. Peak flows with a 50-percent annual exceedance probability (the 2-year flood) were estimated from regional regression equations as an approximation of bankfull discharges. Drainage areas of the three stream reaches studied ranged from 29.6 to 188 square miles. The Hydrologic Engineers Center's River Analysis System step-backwater model was used to compute water-surface-elevation profiles for the 2-year flood along selected reaches of the streams. The base model was modified to determine the effects of reducing main-channel roughness coefficients (Manning's n) by 5, 10, 15, and 20 percent on the computed water-surface profiles. Reach-averaged reductions in water-surface elevations ranged from 0.11 to 1.29 feet over the four roughness reduction scenarios.