This study proposes a new stochastic approach for optimizing diversion system design and its construction schedule by considering different hydrological and hydraulic uncertainties sources. For this purpose, a multi-objective optimization-simulation model was developed to evaluate the failure of a diversion system to flood. Two objective functions, the expected flood damage (EFD) and cost-benefit (CB) index of a diversion system, are optimized in this study using a non-dominated sorting genetic algorithm II (NSGA-II). The approach is tested for four different compositions of uncertainties (Base Case, Case1, Case2, and Case3) to estimate their impacts based on distance index (D) and the boxplot. Finally, finance constraints are evaluated based on the construction period of the project. The Karun-4 dam, located in Iran, is considered as the case study. The obtained results demonstrate that the hydrological uncertainty with \({D}_{case2}^{basecase}=21.335\) and \({IQR}_{basecase}=2.1M\) has the highest effect on the Pareto optimal front and the hydraulic uncertainty of downstream cofferdam with \({D}_{case3}^{basecase}=5.789\) and \({IQR}_{case2}=1.8M\) has the lowest effect on the Pareto optimal front. The best value of the CB index is related to the base case (66.42%) using the pseudo weight factor. The study indicates that the total investment of the water diversion system is lower than the consultant's plan by 20.23%, 18.33%, 17.28%, and 18.81% when the different components of uncertainty are considered. An implementation period of 6-year and 11-year is the best option for no financial constraints and financial constraints, respectively. The stochastic simulation-optimization approach proposed in the present study provides decision-makers reliable insight into planning dam construction.

本研究通过考虑不同的水文和水力不确定性来源，提出了一种新的随机方法来优化导流系统设计及其施工进度。为此，开发了一个多目标优化模拟模型来评估导流系统洪水故障。本研究使用非支配排序遗传算法 II (NSGA-II) 优化了两个目标函数，即导流系统的预期洪水损失 (EFD) 和成本效益 (CB) 指数。该方法针对四种不同的不确定性组合（基本案例、案例 1、案例 2 和案例 3）进行了测试，以根据距离指数 (D) 和箱线图来估计它们的影响。最后，根据项目的工期对资金约束进行评估。位于伊朗的 Karun-4 大坝，被视为案例研究。获得的结果表明，水文不确定性与\({D}_{case2}^{basecase}=21.335\)和\({IQR}_{basecase}=2.1M\)对帕累托最优前沿和下游围堰水力不确定性的影响最大，\ ({D}_{case3}^{basecase}=5.789\)和\({IQR}_{case2}=1.8M\)对帕累托最优前沿的影响最小。CB 指数的最佳值与使用伪权重因子的基本情况 (66.42%) 相关。研究表明，考虑到不确定性的不同成分，引水系统的总投资比顾问计划低20.23%、18.33%、17.28%和18.81%。6 年和 11 年的实施期分别是无财政约束和财政约束的最佳选择。本研究中提出的随机模拟优化方法为决策者提供了对规划大坝建设的可靠见解。