Multi-objective Optimal Design of Detention Tanks in the Urban Stormwater Drainage System: Uncertainty and Sensitivity Analysis

Design of detention tanks becomes important to the flooding control and drainage service management of an urban stormwater drainage system (USDS). While the hydrological and hydraulic models and methods have been widely developed in the literature for the optimal design and management of USDS, there is not yet a general methodological framework that is applicable for all practical systems. This is mainly because of various complexities in practical USDS, such as different design objectives (i.e., multi-objective design) and local design criteria and policies, as well as variety of inevitable uncertainties in the system. Previous work by the authors has focused on the first two aspects, in which a viable design framework has been developed and applied for multi-objective optimal design of detention tanks in the USDS under conditions of different local design criteria; and this paper deals with the third factor, aiming to explore and extend further the optimal design methodological framework to USDS with uncertainties. A real-life USDS in China is applied for this investigation. Uncertainty analysis is firstly conducted to characterize the importance of different uncertainty factors considered in the studied system. The uncertainty analysis result is thereafter incorporated into the previously developed multi-objective optimal design framework, in which the Monte-Carlo simulation method is adopted for the stochastic process investigation. The case application and analysis indicate different influences of uncertainty factors in the system to the multi-objective design results of detention tanks (total cost and flooding risk) in the studied USDS. The results and findings of this study are also discussed in the paper for their practical implications to the design and management of USDS.