Boneyard Creek Bottleneck Analysis and Channel Capacity Alternatives
Flooding of the Boneyard Creek along the north campus of the University of Illinois at Urbana-Champaign have caused multimillion dollar loses in recent years. One way to investigate the flood problem is to determine the hydraulic carrying capacity of the channel and then compare it with the amount of water to be drained to assess the channel adequacy. The hydraulic performance graph (HPG) method of Yen and Gonzalez is an effective tool for such capacity determination and for bottleneck identification. In this study the method is applied to the campus portion of the Boneyard Creek for the May 1995 condition. The channel capacity has been found inadequate, capable of draining floods having a return period of only a few years depending on the backwater effect of the water level at the exit of the channel. Removal of two buildings over the creek and subsequent modi- fication of the channel between Burrill Avenue and Firelane during 1993-95 increase the capacity locally but not the channel between Wright Street and Lincoln Avenue as a whole. Bottlenecks along the channel for different downstream exit water levels are identified, most seriously around the Mathews Avenue Bridge, near the footbridge behind Daniels Hall, and around the Gregory Street Bridge. Removal of these bottlenecks cannot provide the additional capacity needed to solve the Boneyard flooding problem on campus. In view of the existence of a 3-ft drop of the channel bed at Lincoln Avenue Bridge, four different alternatives of deepening the channel bed are investigated. The alternative of lowering the bed of 1 ft is inadequate. The alternatives of deepening the entire bed by 2 ft or 3 ft or linearly from 0 ft to 2 ft improve the channel capacity to a desirable level, especially if the bottlenecks identified are also removed locally. The linear deepening alternative yields a channel capacity curve almost identical with that of deepening the entire channel by 2 ft.