Urban Stormwater Management by Optimizing Low Impact Development Techniques and Integration of SWMM and SUSTAIN Models

Unsustainable development and rapid urbanization have led to changes in the hydrological characteristics of watersheds, and the risk of flooding has been increased consequently. One of the solutions used for quantitative and qualitative control of urban runoff is green infrastructure and low impact development (LID) based approaches that have attracted the attention of many researchers. In this study, SWMM was used to simulate the rainfall-runoff process in region 1, district 11, Tehran. Six scenarios, including different combinations of several LID types such as Green Roof, Rain Barrel, Bioretention Cell, Porous Pavement, Vegetated Swale, and Dry Pond were developed. Then the SUSTAIN model was utilized to assess each scenario's performance. Optimal solutions were then obtained using non-dominated sorting genetic algorithm-II (NSGA-II), and a cost-effectiveness Pareto frontier curve was performed for all scenarios. Results showed that the selected solutions of scenarios one to six reduced the runoff volume by 53%, 4%, 66%, 72%, 31%, 34%, respectively. Scenario 4, with a combination of rain barrels, porous pavements, and vegetated swales with a runoff volume reduction of 72% and an implementation cost of $ 12.2 million, showed the best performance, comparing the other scenarios' corresponding optimal solutions. Scenario 6 also came in next with a 34% effectiveness and a cost of $ 7.1 million. The combined use of SUSTAIN and SWMM, in addition to the technical evaluation, helped to attain optimized, cost-effective solutions for developed scenarios as well. The results of this study can also help relevant organizations and decision-makers to design, evaluate performance, and implement costs of different LID scenarios.