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Rethinking urban storm water management through resilience – The case for using green infrastructure in our warming world

Hettiarachchi, Suresh / Wasko, Conrad / Sharma, Ashish

Abstract

Abstract Urban flooding is one of the greatest threats to life and property, further exacerbated by the impacts of a warming climate. Balancing the increasing demand for liveable space with infrastructure for urban stormwater management presents a planning conundrum. Traditional thinking and design in urban stormwater is reaching limits in adequacy, or have foreboding implementation costs. We argue that a shift in design philosophy from resisting flooding to resilience can reframe this challenge towards viable solutions. We also propose that a simpler way of assessing urban flood resilience is needed to make the shift away from a single event design approach. To that end a Simple Urban Flood Resilience Index (SUFRI) is developed as the basis and the tool for rethinking urban flood management in a future climate. SUFRI offers a “simple” framework for urban flood management as it is based only on hydrologic and hydraulic modelling. We use SUFRI to evaluate the use of green infrastructure in combatting the threat of urban flooding in warmer climatic conditions. Results show that green infrastructure remains effective during more frequent storms (~ 80th percentile) that can occur in warmer climatic conditions and retrofitting or converting a smaller than expected percentage of the urban landscape (up to 5 %) can yield appreciable benefits. Overall, we show that the flexibility and adaptability needed to address the highly variable urban flood response in warmer climates is implicit within resilience based flood management approaches.

Highlights • Shift in urban flood management from flood prevention to urban flood resilience. • An index that can quantify urban flood resilience in a future climate, using only H/H modelling results • Green infrastructure improves urban flood resilience in a future warmer climate. • Green infrastructure has a significant impact on ‘nuisance flooding’. • Effective urban flood management can be achieved using less land area being dedicated to green infrastructure.