Current flood protection capacities will become inadequate to protect many low-lying coastal cities from climate change-induced flooding in the future. Under climate change uncertainty, an adaptive strategy is required to provide supplemental flood mitigation. Green Stormwater Infrastructure (GSI) in developed areas has the potential to provide substantial catchment runoff reduction. However, individual properties vary in their Flood Mitigation Capability (FMC) depending on their land characteristics. An effective methodology is needed to evaluate the FMC of properties to help urban planners determine which to target for GSI and when to implement GSI in light of increased climate change impacts. We advance the Hydrology-based Land Capability Assessment and Classification (HLCA+C) methodology for evaluating the FMC of large properties over the long term (80 to 100-year). It builds on the strengths of existing methodologies and uses a land unit analysis approach for assessing FMC, considering interdependent hydrological and geographical variables. The FMC classification system groups properties with similar flood mitigation characteristics, helping urban planners to understand their potentials and limitations for flood mitigation toward the development of adaptive strategies through time. Step-by-step instructions demonstrate how to apply the methodology to any low-lying coastal city.

Studies indicate Green Stormwater Infrastructure (GSI) on industrial land can provide substantial adaptive flood mitigation within urban catchments under climate change. To identify a cost-effective adaptive GSI network, planners need to evaluate flood mitigation capabilities of industrial properties through time and understand key characteristics informing when, where, and how GSI should be implemented for maximum effect. We applied the Hydrology-based Land Capability Assessment and Classification (HLCA+C) methodology to a catchment in Christchurch, New Zealand, to evaluate the capabilities of industrial properties clustered into Storm Water Management (SWM) zones under different climate change scenarios. SWM zone potentials and limitations were assessed to develop the most capable adaptive flood mitigation network with climate change. We prioritised six of twenty SWM zones for inclusion in the network based on their substantial flood mitigation capabilities. To maximise their capabilities through time, we orchestrated, and implemented GSI in zones incrementally, using different implementation approaches based on key characteristics determining their capability. The results indicated that the most capable zone could mitigate climate change-induced flooding, by itself, up to the end of this century under the moderate climate change scenario. However, if its capability was combined with that of five others, together they could mitigate flooding just shy of that associated with the major climate change scenario up to the end of this century. The resulting adaptive industrial GSI network not only provides substantial flood protection for communities but allows costly investments in flood mitigation structures, such as barriers and levees, to be safely delayed until their cost-effectiveness has been confirmed under increased climate certainty.