Developing a simulation-optimization approach to allocate low impact development practices for managing hydrological alterations in urban watershed

Rapid urbanization and development have led to adverse effects on the urban landscape through flooding and non-point pollutions. Low impact development (LID) techniques, as semi-engineered storm water practices, alleviate urban flooding and pollution. In this study, a simulation-optimization (SO) framework is developed to address the multi-scale, multi-parameter problem of pond and LID sizing and locating. Multi-objective, multi circuit Electimize (MOMCE) optimization algorithm is developed in Matlab environment and coupled to the storm water management model (SWMM) to provide a comprehensive tool for restoring pre-development hydrological condition, while improving stormwater quality. The optimal layout and sizing of ponds and LID techniques are determined for a spectrum of design storms, including 2-, 5-, 10-, and 50-year events considering peak runoff flow and total suspended solids (TSS) loads. It is shown that increasing the return periods of storm events leads to the increased size of detention ponds and LIDs with storage features. Whereas, larger ponds and LID techniques with longitudinal expansion characteristics are more evident in the TSS Load reduction objective. The research indicates that, for a 10-year storm, renovation of old urban tissues in the study area and proper utilization of LID techniques may result in 33 % and 29.7 % reduction of peak flow and TSS loads, respectively.