Hydraulic Model Study of the Busse Woods Reservoir Dropstructure

The Busse Woods Drop Structure and recreation area is located in Cook County, Illinois in Suburban Chicago. Operated as a typical Soil Conservation Service drop structure since 1976, it is now contemplated that the structure be modified to reduce flood flows downstream of the structure for floods greater than the two-year event. In order to maintain its present low flow capabilities and at the same time decrease the return frequency for high discharges associated with low frequency return interval events, it was proposed by the illinois Department of Transportation (IDOT) that a 2.3 ft high steel box beam be installed 1.2 feet above the crest. Placement of such a beam would modify the existing weir flow into three flow regimes: 1) weir flow at low flows, 2) orifice flow at moderate flows, and 3) a combination of orifice and weir flow when the beam is overtopped at higher flows. This report contains the results of rating curve and sediment erosion tests carried out on a 1:12 geometric scale hydraulic model of half of the structure.