Impact on Nonlinear Runoff of Lid Facilities and Parameter Response in the Tvgm Model

Abstract

Human activities such as urbanization have profoundly altered the underlying surfaces, leading to critical water security issues like urban water disasters and pollution, which are now global concerns. Low Impact Development (LID) has been acknowledged as an eco-friendly and promising approach to urban stormwater management. Investigating the nonlinear mechanism and influencing factors of the LID rainfall-runoff process is both novel and significant. Therefore, we conducted artificial rainfall experiments and numerical simulations to study runoff generation of LID facilities, using the urban hydrological time variant gain model (TVGM) and correlation analysis, considering multiple influencing factors such as rainfall intensity, initial soil moisture (W0), and underlying surfaces. Based on the results from correlation analysis and numerical simulations, we also quantitatively analyzed the core parameters g1 and g2 in TVGM. Results revealed that both higher mean rainfall intensity (Pm) and W0 weaken the hydrological performance of LID facilities, which outperform permeable surfaces and impermeable surfaces under identical Pm and W0 conditions. Furthermore, as the linear and nonlinear runoff parameters of the TVGM, g1 exhibits a significant positive correlation with Pm and W0, while g2 shows a significant negative correlation with Pm and W0. The quantification results of the parameters indicated that infiltration excess runoff in the initial runoff stage adheres to a nonlinear pattern. Under conditions of lower Pm and drier W0, the infiltration excess runoff process exerts a more pronounced impact on total runoff, resulting in a higher nonlinear runoff coefficient g2 and a lower linear runoff coefficient g1, and vice versa. These research findings will aid in analyzing nonlinear runoff mechanisms of LID facilities and establish a theoretical basis for the simulating and predicting urban rainfall-runoff dynamics.

Keywords: LID, Nonlinear runoff, TVGM, Correlation analysis