文章引人随机微分方程，采用泄洪风险分析方法评估水电站采用非常泄洪设施对大坝安全所带来的影响，并结合某一工程设置两条非常泄洪洞的可行性进行论证。在充分分析计算条件对风险率灵敏性的前提下，讨论了调洪方案下两条非常泄洪洞启用的条件及相关的泄洪风险，为导流洞改建方案的确定提供依据。分析结果表明该方案基本维持原设计方案的泄洪风险水平，说明设置非常泄洪设施是可行的。

To predict the risk assessment of a dam which constructs two special tunnels for unusual flood release, a method based on stochastic differential equation is developed in this paper. After analyzing the sensitivity of computational conditions on discharge risk, the requirement for useing two unusual tunnels in this project and their discharge risk are discussed, which provides a scientific basis for making decision on unusual tunnel design plan. The analyzed results show that the risk level of unusual tunnel plan can keep the same as that of the original design plan. Therefore, it proves that the unusual tunnel plan is reasonable.