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<br />. <br /> <br />A utility program. FEQUTL (Linsley. Kraeger Associates, 1995). was used to develop tabular <br /> <br /> <br />representations of hydraulic through hydraulic structures including culverts. embankments. dams. and <br /> <br /> <br />overflow, The Federal Highway Administration (FHW A) program WSPRO (U.S. DOT, 1990) was used <br /> <br /> <br />to compute the flow characteristics at bridge openings. <br /> <br />Model Calibration and Verification <br /> <br />A flood in August 1987 was a large stonn event and was used to calibrate the model. For this stonn <br /> <br /> <br />event. rainfall amounts were adjusted to account for spatial variation of rainfall using factors based on a <br /> <br /> <br />isohyetal map developed by DEC. The simulated flood elevations were compared with high water mark <br /> <br /> <br />observations at several stations supplied by the Illinois Department of Natural Resources. Office of Water <br /> <br /> <br />Resources (see Figure 2). In addition. simulated versus observed hydrographs (both discharge and stage) <br /> <br /> <br />at two USGS continuous recording gages were compared. Excellent agreement between simulated and <br /> <br /> <br />observed high water levels. general shape of hydrographs. flow discharges and water levels was achieved. <br /> <br />. <br /> <br />The model was utilized to simulate 30 storm events between 1985-199~ for model verification. Figure 3 <br /> <br /> <br />shows the predicted versus recorded flow volumes and peak flow for these stonn events. . These figures <br /> <br /> <br />show a general agreement between simulated and obse".ed flow volumes and peak discharges. The figurcs <br /> <br /> <br />also indicate that the model under-predicts the flow volume slightly and over-predicts the peak flow. The <br /> <br /> <br />model was then used to simulate 50-years of continuous flow records. The results from this simulation wiII <br /> <br /> <br />be used to statistically determine exceedance probabilities for peak river stages. <br /> <br />The Use of the Model as a Floodplain Management Tool <br /> <br />The FEQ model of lhe West Branch Dupage River has been utilized as a floodplain management tool. <br /> <br /> <br />Structures and development within the floodplain can bc easily modeled and the effects of these projects <br /> <br /> <br />on the continuous simulation record can be detennined. Furthennore. the effects of flood hazard <br /> <br /> <br />mitigation measures can be detennined, For example. the model was utilized to analyzc the effects of <br /> <br /> <br />different reservoir operating scenarios of an existing flood control reservoir located on the West Branch <br /> <br /> <br />which has not been used because of dam safety inefficiencies, The model predicted that the reservoir <br /> <br /> <br />could be utilized to effectively reduce flooding potentials downstream without adversely impacting <br /> <br /> <br />upstream residences. As a result. design measures to rehabilitate the dam to meet dam safety regulations <br /> <br /> <br />and an operation scheme for the reservoir have been proposed, <br /> <br />. <br /> <br />References <br /> <br />DuPage County. Department of Environmental Concerns <br />1995 Digital 2-foot Contour Maoping for the West Branch Watershed <br /> <br />Linsley, Kraeger Associates, Ltd. <br />1995 Unsteadv Flow Solutions. FEO: A Modeling Svstem for Unsteadv Free-Surface Flow in a <br />Network of Channels. Working Draft <br />