Disaster Reduction in Dam and Reservoir Designby Krishan P. Singh, Illinois State Water Survey, Champaign, United States,
Document Type: Proceeding Paper
Abstract: Disaster reduction for small- and medium-sized reservoir projects is considered for two specific types of dam failure: 1) during extremely high floods, and 2) when severe reservoir silting negates reservoir utility and exposes downstream areas to environmental disaster. Safeguarding a dam against failure due to high floods is achieved by satisfactory design of the spillway. But economical protection against dam failure also includes a considerably less expensive emergency spillway for operation only when the flood exceeds a 500- or 1,000-year recurrence interval. Conventional dam and reservoir design with an overflow spillway is conducive to storing most of a reservoir's incoming sediment. Lower capacity-inflow ratio reservoirs suffer the most. Water flowing over the spillway is relatively sediment free, and it scours the downstream bed and banks. Sediments in the reservoirs cause recycling of nutrients and pollutants associated with them. Gradual sediment buildup reduces effective reservoir storage capacity and adversely impacts the uses for which the reservoir was originally designed. In the case of dam failure, all the sediments will be sluiced out, covering lands downstream and causing a severe environmental disaster. To minimize sediment deposition, however, requires a conservation-oriented and environmentally desirable dam and reservoir design.
Subject Headings: Reservoirs | Dam failures | Spillways | Sediment | Failure analysis | Environmental issues | Floods
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