How blue-green-gray infrastructure shapes spatiotemporal dynamics of flood resilience

Abstract

Estuarine delta regions (EDRs) face escalating compound tidal-fluvial-pluvial flooding under climate change and rapid urbanization, yet impact assessments often rely on single-time or extreme-value indicators that obscure when blue-green-gray infrastructure (BGGI) benefits emerge, how robust they remain under uncertainty, and how they drive flood resilience. We propose a scenario-process-pattern (SPP) framework that evaluates flood resilience across the initial, peak, and recession phases, linking the hydrodynamic responses to BGGI spatial attributes. Applied to the Pearl River–East River–Shiziyang EDR using MIKE FLOOD simulations of seven design plans under 12 hydroclimatic scenarios, SPP combines tipping-point detection, principal component analysis, and Bayesian mixed-effects modeling to assess phase-specific and integrated resilience. Phase-specific responses include constructed-area water volume, blue-green and drainage-system storage volume, and high depth–velocity flooded area; GIS-derived predictors quantify BGGI spatial attributes including storage capacity, connectivity, and interface coupling. Results show pronounced spatiotemporal heterogeneity in how BGGI shapes flood resilience: plan differences are limited in initial and recession phases but widen at peak, with spatial effects showing subregional asymmetry and clustering around hydraulic control points; under high-hazard scenarios, adaptive plans halve peak constructed-area water volume and shorten high-hazard duration by 4 h, whereas rigid-defense plans exhibit threshold-type failure and inferior integrated resilience robustness. Gray systems primarily curb early risk, green storage and coupling dominate peak attenuation, and connectivity accelerates recession yet can amplify initial flood convergence. SPP provides a transferable, process-based evidence chain to support alternatives appraisal, adaptive flood management, and resilient spatial planning in EDRs.