New approaches for quantifying the risk of a dam break

Construction of dams on streams allows multiple beneficial uses to the popu lation. But in the advent of extreme floods, the structures may fail and fr ee the stored water. Recently built structures respond to more and more dem anding design standards. Older structures, which were deemed safe at the ti me of their construction, might sometimes no longer satisfy these new stand ards. To evaluate the necessity, the importance and the urgency of works th at would make these structures conform again, one of the more and more used approaches consists in resorting to a risk analysis. A risk analysis has b een applied a posteriori on a site where a failure was observed in order to determine whether this approach would have brought the managers to underta ke corrective works. This application shows the limited capacity of the con ventional risk analysis for dams. Two alternative approaches are presented and discussed as a tool to evaluate the risk of a site.