Watershed modeling and flood routing for safety assessment of an existing dam

Hydroelectric power resources constitute a renewable and economic means of providing electricity to serve the energy needs of our modem society. As dams get older, there is a need to ensure that their conditions of safety and integrity are also consistent with today's acceptable standards and criteria. This paper outlines the scope and major engineering tasks in the Dam Safety Assessment Program undertaken by Ontario Hydro in Toronto, Canada. Methodologies used to determine the probable maximum flood for a high-hazard dam are presented together with a flood routing model. The 2012 MW R. H. Saunders/Robert Moses Generating Station on the St. Lawrence River is used as an example to illustrate such methodologies adopted for dam safety assessment. It is demonstrated that under probable maximum flood conditions together with extreme wind effects, the main dam of this power station would still have a comfortable freeboard allowance, primarily because of the vast storage capacity of Lake Ontario. The spill capacity is also found to be adequate. The dam meets the requirements and pertinent standards of dam safety assessment.