Impact on nonlinear runoff of LID facilities and parameter response in the TVGM model

Abstract

Human activities like urbanization have profoundly altered the underlying surfaces, leading to crucial water security issues, including urban flooding and pollution. Low Impact Development (LID) has been acknowledged as an eco-friendly and promising approach to urban stormwater management. Understanding the nonlinear mechanisms of LID facilities (LIDs) under different rainfall-runoff processes is essential. In this study, we conducted a series of laboratory-scale rainfall experiments to study the runoff generation of LIDs. The urban hydrological time variant gain model (TVGM) was employed to simulate the experiments with consideration of rainfall intensity, initial soil moisture, and underlying surface conditions. The experimental results showed that increases in average rainfall intensity (P_m) or initial soil moisture (W₀) reduced the runoff reduction effectiveness of LIDs. For the first time, a systematic quantitative analysis of the key nonlinear parameters, g₁ and g₂, within TVGM was conducted for LIDs. Based on the simulation results, the parameter g₁ was found to be positively correlated with P_m and W₀, while g₂ showed a significant negative correlation with these factors. Notably, nonlinear infiltration-excess runoff predominated at relatively low rainfall intensities and initial soil moistures, resulting in higher values of the nonlinear parameter g₂.