Exploring the effectiveness, risks and strategies for implementing sustainable drainage systems in a landslide-prone catchment

Abstract

<p>A well-designed and strategically distributed sustainable drainage system (SuDS) can potentially restore the hydrologic conditions of urban areas to their pre-development state. However, cities situated in sloping or landslide-prone areas rarely adopted this technique. In such terrains, slopes could be potential seepage faces for groundwater discharges, causing uncertainty over the efficacy of SuDS in groundwater replenishment. Moreover, the dynamics of groundwater are intrinsically linked to slope stability, suggesting a potential influence of SuDS on this critical aspect, an area that has not been extensively explored. This study investigated the implementation of SuDS in a landslide-prone catchment, focusing on the effectiveness, risks, and distribution strategies. The effectiveness of SuDS was assessed by runoff volume reduction and groundwater replenishment. The risks were quantified by the minimum safety factor and area subjected to failure. Conclusively, it proposed strategies centered around the spatial distribution of SuDS practices, i.e., uniform, slope-distant and slope-remote distribution (UD, SDD, and SRD, respectively) at implementation ratios of 1.25%, 2.5%, 5% and 10%, aiming to harmonize hydrological efficiency with slope safety. We integrated Storm Water Management Model (SWMM) with Modflow to achieve the surface–subsurface hydrologic simulation and used Scoops3D to perform slope-stability analyses. Results showed that the implementation of SuDS effectively reduced runoff and enhanced groundwater storage. The UD strategy exhibited the highest capacity of runoff volume reduction, while the SDD strategy facilitated the highest groundwater storage. At a low implementation of 1.25%, the slope stability is not significantly affected regardless of distribution strategies. At a higher implementation ratio, more areas become unstable when applying the UD strategy. The SDD and SRD strategies can circumvent this adverse impact. Without much compromise on three objectives, the SDD strategy is most recommended to achieve a balance between runoff reduction, groundwater storage and slope safety.</p>