Impact of effective impervious surface disconnection on urban hydrographs: A multi-scenario modeling study at the catchment scale

As urbanization continues to advance, the increase in impervious surfaces, especially effective impervious areas (EIA), has resulted in a decrease in infiltration and an increase in surface runoff. Due to the direct impact of EIA on the urban hydrologic cycle, reducing the EIA by redirecting the runoff from the paved surfaces to the receiving pervious area (RPA) is an effective measure for restoring the health of the urban hydrologic cycle. Previous studies have primarily focused on EIA disconnections at the plot scale; however, due to the high heterogeneity of surfaces and the complexity of overland flow paths at the catchment scale, the impact of EIA disconnection on urban hydrographs remains uncertain. In this study, we aimed to evaluate the hydrological response of EIA disconnection by routing runoff from EIA to RPA using the Storm Water Management Model (SWMM) at the catchment scale. Multiple scenarios of factors, including rainfall under different return periods, three EIA disconnection scenarios, three infiltration scenarios, three antecedent soil moisture (ASM) scenarios, and three depression storage of RPA scenarios were considered, and the SWMM was utilized to simulate the hydrological response of EIA disconnection. The results showed that EIA disconnection had a positive effect on runoff control for return periods of less than a 5-yr period, but the effect gradually decreased as return periods exceeded a 5-yr period. Among the various influencing factors, RPA infiltration had the most significant impact on hydrological response. With the high infiltration scenarios, the maximum reduction ratios of peak flow and runoff depth were 28.1 % and 43.9 % when the return period was less than 5-yr, respectively. When the return periods were greater than 5-yr, the maximum reduction ratios of peak flow and runoff depth were 13.6 % and 24.7 %, respectively. With the extremely low infiltration scenarios, there was little variation in the peak flow and runoff depth reduction in different return periods, with maximum values of 2.5 % and 1.9 %, respectively, and the peak flow even increased in the 50-yr and 100-yr return periods after EIA disconnection. Consequently, when the infiltration of RPA was low, it was difficult to reduce peak flow under high return periods by relying solely on the infiltration of RPA. Nevertheless, as the depression storage capacity of RPA was increased, the runoff control effect improved, and the peak flow and runoff depth could still be reduced by 39.0 % and 49.2 %, respectively, even under the condition of a 100-yr return period. This study provides new insights into the impact of EIA disconnection on the hydrologic cycle and offers effective strategies for urban stormwater control and management at the catchment scale.