Effects of Nuanced Changes in Lot Layout and Impervious Area Connectivity on Urban Recharge

The water balance in urban watersheds is strongly controlled by precipitation patterns and the large-scale presence and arrangement of impervious area, within the watershed. While it is well known that the configuration of impervious area within an urban catchment has a predictable impact on the catchment’s rainfall-runoff response, the response of groundwater recharge to urbanization is difficult to estimate. Recent studies have found both increases and decreases when examining recharge’s response to the gross arrangement of impervious surface in the watershed. Very little work has been done to identify how nuanced, small-scale changes in impervious area configuration and connectivity, such as downspout disconnection distance and driveway pitch, impact recharge rates. The objective of this study is to determine the extent to which the amount, arrangement, and connectivity of impervious area in urban residential lots impacts recharge in urban watersheds. We hypothesize that there are some layouts and connectivity schemes that will promote recharge by concentrating infiltration and developing strong, fast-moving wetting fronts that are able to penetrate through the root zone without entirely being extracted by roots. Because existing hydrological models do not capture the arrangement of impervious area at the parcel scale, we will address our research questions by constructing our own, physically-based model of water movement through urban lots. Using our model, we will conduct a factorial experiment wherein we determine how recharge responds to lot layout, connectivity between impervious areas, soil types, and rainfall patterns. Our results will suggest ideal layouts of urban residential lots for achieving various recharge management goals, and our work will also contribute to the larger body of literature that seeks to quantify how urbanization impacts groundwater recharge. Empirical relationships we develop in this study will be useful for scaling up the effects of parcel-level configuration on hydrology to the larger, catchment scale.