What America’s half-trillion dollar flooding problem needs

Flooded basements, mold growth, and rotting wood are all symptoms of the alarming uptick in flood damage facing property owners nationwide. Its costs, which can reach nearly a staggering half a trillion in the U.S. each year, are surging as the impact of climate change worsens. And that impact is becoming unpredictable, with 29% of flood claims coming from outside what are typically considered “high risk areas.” The search for an answer to this crisis has been focused disproportionately on insurance premiums and incentives, along with state-backed schemes to ensure reinsurance companies can be counted on. And while important, that approach will never work on its own; one need only look at population growth in places like Florida to see why. An effective solution to the flooding challenge must focus on innovation, and that means looking not only at where we build and its related insurance consequences, but how we build. URBAN DESIGN FOR VULNERABLE CITIES Cities are our vital economic centers, but they’re also traditionally the areas hardest hit by flooding, which paralyzes commerce and runs up damage. Cities have extensive impervious land cover—such as parking lots, roads, and rooftops—that neither absorb water nor properly drain it, leading to significant water damage. For instance, a Salt Lake City study found that increased paved and built-over surfaces had a far greater effect on flooding than changes in rainfall, driving up to 240% more flooding intensity in smaller storm events. While we typically think of cities like Miami or New Orleans as vulnerable outliers, in America’s economic epicenter, New York, half of the residents—4.4 million people—are exposed to extreme flood risk. While the response to this risk isn’t one-size-fits-all, there are numerous success stories that offer useful lessons we can draw on to better protect our cities from flooding without completely reinventing the wheel. Rotterdam, for example, has deployed a “sponge city” approach that in