An assessment of the hydrologic effectiveness of low impact development (LID) practices for managing runoff with different objectives.

This study represents an approach to assess the hydrologic effectiveness of low impact development (LID) practices based on the expected runoff process with different objectives and land utilization. The proposed approach is to simulate runoff hydrograph rather than several indices (e.g., runoff initiation, peak flow, and runoff volume) to avoid the uncertainties under a certain rainfall scenario. A rainfall-runoff model of a residential district in China, constructed based on the stormwater management model (SWMM), is auto-calibrated (validated) based on 12 (25) observed rainfall and runoff events using model-independent parameter estimation (PEST). The priority sites and parameters for LID practices for different objectives are auto-calculated using PEST based on the calibrated model and different expected runoff processes. The expected runoff processes are simulated from the calibrated model with four impervious cover scenarios corresponding to 5-year, 2-h duration design storm. The study illustrates that (i) the proposed approach can auto-optimize runoff manage strategies based on LID practices and land; (ii) the design parameters of LID practices can be auto-calculated and that simulated runoff processes are in near perfect agreement with expected runoff processes; (iii) this approach can auto-optimize any specific parameters of the SWMM and LID practices without changing those determined parameters. Our simple, but quantitative, approach for identifying potential LID sites and design parameters based on land can better inform the hydrologic effectiveness of LID practices for managing runoff.