Low impact development planning through a comprehensive optimization framework: Current gaps and future perspectives

The complexity of urban stormwater management has helped position low impact development (LID) optimization as one of the leading-edge research areas worldwide. Some literature reviews have provided valuable background on a specific LID optimization part, such as tools, objectives or planning, etc. However, a systematic review covering a complete optimization process remains lacking. In this study, a comprehensive optimization framework involving seven steps was first constructed. Eighty-eight research papers were retrieved and thoroughly analyzed. Results showed a growing trend about large-scale optimization on numerous small-scale achievements, which would alter optimization objectives (society, environment or ecology, etc.) and furtherly determine tool selection. Nonetheless, large-scale optimization is challenging due to theoretical and technical limitations. Besides, most studies focused on a single scale, of which objective quantification and related multi-scale matching may be problematic. Coupled green-grey optimization is the common conduction for better benefits (average 61% and 54% runoff volume and pollution reduction). Nevertheless, water body (blue) responses have not been fully incorporated into optimization and assessment. Therefore, objectives downscaling decomposition and schemes up-scaling theory were proposed to integrate green-grey-blue system for multi-scale optimization. This study complemented review through an optimization process, contributing to explore future perspectives of this field more comprehensively.