THE PIANO KEYS WEIR: A NEW COST-EFFECTIVE SOLUTION FOR SPILLWAYS

Free-flow spillways are simpler and safer than gated ones, but the low specific flow of their traditional shapes requires high spilling nappe depths and thus huge losses of storage (100 x 10m worldwide). A new shape of free-flow spillway (the "Piano Keys weir") can increase the specific flow fourfold or more. It could substantially reduce the cost of most new dams and increase, at low cost. the safety and the storage and/or the flood control efficiency of many existing dams.