Assessing the impact of green infrastructure spatial distributions on hydrological connectivity and runoff reduction using landscape metrics

Despite rapid advances in green infrastructure (GI) research, a critical gap remains that most studies optimize GI for runoff reduction while hydrological connectivity (HC) remains underexplored. In particular, the role of spatial configuration in shaping HC has not been isolated from GI quantity, leaving a research gap in balancing flood mitigation and connectivity preservation.This study addresses this gap by systematically evaluating how three GI spatial strategies (uniform, random, and junction-based) affect runoff, HC, and landscape integrity in an urban watershed (Seattle, USA). 27 scenarios were simulated with VELMA hydrological model over two years under consistent total GI coverage, varying unit size and spatial distribution. Landscape metrics computed by FRAGSTATS were linked to runoff and HC via ordinary least squares regression to quantify how specific configuration attributes drive responses.Results show that increasing GI coverage reduces runoff but weaken HC (p<0.001). Compared to junction-based distribution, more interspersed layouts better preserve HC, albeit with a modest loss of interception efficiency. Runoff reduction is maximized by intermediate-sized GI, whereas HC is better preserved by larger, internally continuous patches placed across multiple locations. Sensitivity analysis across diverse scenarios confirm the robustness of these patterns.These findings demonstrate that spatial pattern, beyond GI quantity, drives multifunctional performance. A hybrid spatial strategy is recommended that deploys intermediate-sized GI for runoff reduction, enhances HC through the integration of GI with other green area, and reserves mid/large junction installations for peak interception. This provides configuration-explicit guidance that closes the gap between runoff-centric design and connectivity-aware GI planning.