Comparison of Deterministic and Uncertain Approaches in Rehabilitation of Eastern Part of Tehran Stormwater Drainage System

Increase in the urbanization trend in the world and effects of climate changes on the urban stormwaters including frequency and intensity have become a serious issue. Renewable water resources has significant effect in the design and rehabilitation of urban stormwater drainage systems too. While most of the previous studies on the urban stormwater management have been based on the assumption of a specific return period, risk-based design method is an alternative approach considering the effects of more severe events and also preventing over-estimated designs. In the present study, a coupled numerical and multi-objective optimization framework has been developed in the MATLAB programming software to compare the performance of mentioned deterministic and uncertain design approaches applied to rehabilitate eastern part of Tehran stormwater drainage system suffering from lack of sufficient capacity. In this direction, two simultaneous strategies of relief tunnel and storage unit applications have been utilized to minimize conflicting objective functions of “rehabilitation costs” and “flooding volume”. Results show that, although acceptable performance of a rehabilitation strategy proposed by related consultant engineering company to compensate system’s lack of capacity was verified, utilizing the present coupled numerical and optimization model caused significant reduction of rehabilitation costs and/or improvement of the system performance. Additionally, evaluation the results obtained reveals that there is no network sensitivity to return period assumption and consideration of input parameters’ uncertainty in case the present fixed rehabilitation layout considered according to feasibility studies.