Evaluating Capability of Green Stormwater Infrastructure on Large Properties toward Adaptive Flood Mitigation: The HLCA+C Methodology

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.