Integrating hydrological and economic assessments of soil infiltration enhancement for urban flood resilience.

Urban flooding, exacerbated by climate change and the expansion of impervious surfaces, poses growing risks to sustainable urban development. Enhancing soil infiltration through green infrastructure is a promising nature-based solution, yet its hydrological effectiveness and economic viability under diverse rainfall scenarios remain insufficiently quantified. This study develops an interdisciplinary framework integrating column experiments, physically distributed hydrological modeling, and cost-benefit analysis to assess ceramsite-amended soils for urban flood resilience. In laboratory tests, ceramsite content (C) of 10 %, 20 %, and 30 % increased cumulative infiltration by 8.9 %, 74.0 %, and 138.6 %, respectively, corresponding to modeled infiltration multipliers (K) of 2, 4, and 6. These empirical results informed a distributed GSSHA model of a 14.3 km2 urban catchment, tested under seven design storms with return periods (RP) of 1-100 years. Simulations show that moderate enhancement (K = 2-4 ≈ C = 10-20 %) substantially reduces peak discharge for storms with RP > 10 years, while gains in total infiltration volume plateau under extreme events due to subsurface storage limits. A Weighted Marginal Benefit Index (WMBI) combining hydrological performance with implementation cost identifies K = 2 (C = 10 %) as the most cost-efficient option and K = 4 (C = 20 %) as the best multi-objective solution. K = 6 (C = 30 %) yields the highest infiltration capacity (≈2.7× baseline) but exhibits diminishing marginal returns, being justifiable only under eco-resilience priorities. The proposed hydrology-economy framework supports tiered, context-sensitive design of infiltration measures, offering a transferable tool for data-driven sponge city planning.