Finding the right bucket in the right place and at the right time: A novel methodology for developing adaptive flood mitigation strategies with climate change

Internationally, many coastal cities will face disastrous flooding with climate change; however, it is difficult to plan for it under high uncertainty. Conventional flood mitigation strategies, such as installing defence structures on the front line are expensive and risky. Green stormwater infrastructures (GSIs) on large, developed parcels of land, located in key locations in a catchment, are capable of providing substantial flood mitigation. Networks of GSI can be designed to act in concert and rolled out when and where needed. However, parcels have different flood mitigation capabilities through time depending on their biophysical characteristics, and an effective methodology for evaluating and comparing them is missing. Here, we present the Hydrology-based Land Capability Assessment and Classification (HLCA+C) methodology. It builds on the strengths of existing methodologies and uses a land unit analysis approach, that assesses interdependent hydrological and geographical variables. We demonstrate the effectiveness of this approach in a Christchurch, New Zealand catchment. Its application led to the identification of an adaptive GSI flood mitigation network for the next 80 years that can mitigate flooding just shy of that associated with the major climate change scenario. Effective flood mitigation is a matter of finding the right bucket in the right place and at the right time