Planning Stormwater Retention for Resilience Against Extreme Rainfalls

Rethinking How Cities Prepare for Extreme Rainfall Cities often prepare for extreme rainfall using a single “design storm,” such as a 100-year storm of a predetermined duration. But storms with the same return period can produce very different flooding losses. In “Planning Stormwater Retention for Resilience Against Extreme Rainfalls,” Liu, Qi, and Zhang develop a robust optimization framework that identifies the most damaging rainfall scenario for a city based on its existing drainage and retention infrastructure. Case studies of Toronto, Manhattan, and New Orleans show that the storm a city should prepare for changes with local infrastructure and climate conditions. The analysis also challenges the idea that greener is always more resilient; although green infrastructure offers important environmental benefits, concentrated gray infrastructure can become more valuable when rainfall is severe or budgets are tight. In Toronto, robust planning could save an estimated $6 million annually today and as much as $1.5 billion annually by 2050.