Effect of spatial allocation of green infrastructure on surface-subsurface hydrology in shallow groundwater environment

Abstract

Green infrastructure (GI) controls surface runoff and restores pre-development hydrological conditions in a more environmental-friendly way. However, shallow groundwater restricts the implementation of GI due to possible groundwater contamination, groundwater flooding, and decline of surface runoff control efficiency. Thus, it is challenging to strike a balance between surface runoff control and groundwater protection. Some design methods have been proposed, but knowledge on how to allocate GI to maximize the benefits and minimize the problems is limited. This study utilized a loosely-coupled hydrological model, named SWMM-MODFLOW, to examine the impact of spatial allocation of GI on surface hydrological performance (e.g., peak and volume reduction of surface runoff and flow of catchment outlet) and groundwater table dynamics (e.g., maximum height of groundwater mound) at an urban catchment at the Kitsap County, Washington State, of the U.S. GI showed good performance in surface runoff reduction even in shallow groundwater environment. It enhanced the formation of groundwater mound but the effect was localized. Porous pavements showed better performance than bioretention cells, particularly in the peak and volume reduction of surface runoff. Bioretention cells allocated aggregately showed slightly better runoff reduction than that allocated distributedly, and GI in upstream areas generated greater groundwater mound than that in downstream areas. The results of this study provide some references for allocating GI in the catchment scale considering surface and subsurface hydrology in shallow groundwater environment.