Simulation and Evaluation of Collapsible Risk of Low Impact Development Rainwater System in Collapsible Loess Area

To investigate the risk levels of collapse associated with different Low-Impact Development (LID) measures employed in constructing stormwater systems within collapsible loess areas, the study utilized the High-Efficiency and High-Precision Urban Stormwater Model (GAST) to analyze the risk of waterlogging. The aim was to propose a method that integrates the analysis of waterlogging accumulation time with considerations of the correlation between the collapsibility coefficient and soil parameters, thereby assessing the collapse risk level of various LID measures. This method was applied to examine the changing patterns of settlement risk levels in grassed swales and rain gardens under different rainfall return periods (P1 = 20 years, P2 = 50 years, P3 = 100 years) and water accumulation durations (T1 = 0.5 days, T2 = 5 days). Findings reveal a direct correlation between rainfall return periods and collapse risk levels. Specifically, at P3 = 100 years, 50% of the collapse risk level in the study region reaches level III. However, when the water accumulation duration is extended to 5 days, the percentage of locations classified as category III increases to 75%. Despite rain gardens' superior water storage capacity compared to grass swales, they also elevate the risk of collapse. Therefore, diligent monitoring of rain garden durability during prolonged periods of frequent rainfall is essential. The evaluation approach proposed in this research demonstrates a 75% accuracy rate, affirming its initial reliability for evaluating the risk associated with constructing LID stormwater systems in collapsible loess areas. Furthermore, it can be utilized for further investigations into the collapsibility impacts of LID measures in regions characterized by collapsible loess.