Stormwater runoff reduction benefits of distributed curbside infiltration devices in an urban catchment

Distributed infiltration systems can benefit downstream water bodies by reducing the runoff flowrate and volume discharges from the catchment. Investigating their runoff flowrate and volume reduction potential at the catchment scale will inform decision makers regarding their efficacy for managing catchment outflows. To this end, we conducted field investigations at the residential catchment scale for three years. The study monitored the catchment for one year before the installation of leaky well systems (preinstallation) and two years after installation (postinstallation). The hydrological model, calibrated to preinstallation catchment outflows, acted as a virtual control tool. Runoff flow outputs from the control model and two years of monitored runoff flow data from the postinstallation period were analysed using statistical methods. The statistical tests showed a significant 13% reduction in average flowrates in storms with a corresponding runoff flowrate of up to 50 L/s. The study further reported the ability of infiltration systems to reduce runoff volume in the catchment by 9%. This reduction was not significant, however, as per the results of the statistical analysis. We then fitted the generalized linear model (GLM) to the monitored and simulated runoff volume data. This enabled us to break down the effect of curbside infiltration systems on runoff volume according to corresponding peak flowrates during the storm. The results of the two-way ANOVA performed to detect significant differences in the regression slopes of the GLM indicated that curbside infiltration systems significantly reduced runoff volume for storms when the runoff flowrates remained below 100 L/s.