Improving the flood control at a lower cost for a future Hydro-Québec hydroelectric facility on the Toulnustouc River, Canada

Prior to the construction of a new hydroelectric facility on the Toulnustouc River, Quebec, Canada, optimization was carried out on the dams and spillway design, resulting in a CAN$6 million reduction in the total project cost while improving flood control. This result was obtained using a new approach to the design of civil works, in which the dam and spillway were in complete interaction with one another. In this approach, the possibility of increasing the freeboard of the dams more than that usually required by Hydro-Québec criteria was allowed. The additional freeboard or reservoir volume is strictly assigned to flood control to reduce the maximum released discharge to existing downstream facilities. The raising of dam crests generates additional cost that is more than compensated for by a reduction in spillway capacity and cost.Key words: flood, control, cost, spillway, dam, optimization, security, freeboard.