Improved Stormwater and Flood Analysis developed for Lake County, Illinois

Improved Stormwater and Flood Analysis developed for Lake County, Illinois

Simple models of rainfall losses and relations between streamflow and time during storms provide vital information for stormwater, flood-plain, and water-resources management throughout the United States. The U.S. Geological Survey (USGS) in cooperation with the Lake County Stormwater Management Commission (LCSMC) studied storm rainfall and runoff data for small watersheds (less than 40 square miles in area) in Lake County. Rainfall and runoff data were collected from 1990 to 1995 to develop relations between streamflow and time for storms on the basis of watershed and storm characteristics. These relations are useful for stormwater and flood analysis on watersheds for which rainfall and runoff data are not available. Data for large storms (more than 0.4 inches of runoff) for nine watersheds in Lake County, Ill., (Bull Creek, Terre Faire Ditch, Indian Creek, Green Lake Ditch, North Branch Chicago River, Skokie River at Lake Forest, Skokie River near Highland Park, Squaw Creek, and Flint Creek) were utilized to develop the estimation equations. Charles Melching, USGS hydraulic engineer and principal author of the report, said, "Application of the estimation equations resulted in accurate simulation of 8 of 11 large storms not utilized to develop the equations. These results indicate that application of the estimation equations may result in accurate estimation of streamflow over time from storms for design of dams, detention ponds, culverts, and other flood-control and stormwater-management structures, evaluation of the regulatory flood plain, and other water-resources planning activities in Lake County." The estimation equations should improve stormwater and flood analysis, design, and planning done by the LCSMC and others working in Lake County.

The report, titled "Equations for Estimating Synthetic Unit-Hydrograph Parameter Values for Small Watersheds in Lake County, Illinois," by Charles S. Melching and Jason S. Marquardt, has been released as U.S. Geological Survey Open-File Report 96-474. Copies are available for inspection at the U.S. Geological Survey, 221 North Broadway Ave., Urbana, Ill., and at most large libraries nationwide. Paper and microfiche copies can be purchased at cost from the U.S. Geological Survey, Branch of Information Services, Box 25286, Federal Center, Denver, CO 80225 (telephone: (303) 202-4700). Orders must include check or money order payable to U.S. Department of Interior-U.S. Geological Survey and must specify report number OFR 96-474.