Two-scale optimal management of urban runoff by linking LIDs and landscape configuration

Abstract

Landscape composition and configuration of urban patches impact greatly on hydrological process, of which low impact development practices (LIDs) have been incorporated worldwide to management stormwater runoff quantity- and quality-related issues. Although optimization design for LIDs has been studied extensively to improve stormwater management at catchment scale, a further study of LIDs-based landscape configuration at site scale has not been fully explored. In this study, a two-scale optimization framework was constructed to integrate spatial layout and landscape configuration of LIDs using SWMM, NSGA-II and GIS techniques. The spatial optimization at catchment scale showed that area of sink landscape almost doubled as the distance to outlets decreased. A further site-scale optimization by a new landscape metric, in terms of CRSS (configuration ratio between patches of runoff sources and sink), was conduct to achieve LIDs-based landscape configuration optimization. Runoff flow and pollution were significantly correlated with CRSS in power function, quantifying CRSS thresholds of 0.57–0.69 as the most adaptive strategies for stormwater management. Notably, the CRSS thresholds were higher for ammonia nitrogen (NH3-N) and suspended solid (SS) pollution, especially targeting source patches of roofs. The optimization in this study could improve the reduction of runoff peak flow of heavy rain, peak concentration of chemical oxygen demand and SS, and initial scouring of NH3-N.