The way the federal government analyzes intense rain events isn’t keeping up with the reality of climate change, and that has serious implications for infrastructure projects and the availability of, and rising cost of, flood insurance.
Severe rainstorms, sometimes described as “atmospheric rivers” or “torrential thunderstorms,” are making the concept of a “1-in-100-year flood event” obsolete, according to a report from First Street Foundation, an organization focused on weather risk research.
These events are occurring more frequently due to the impact of climate change, but federal rainfall analysis, managed by the National Oceanic and Atmospheric Administration, isn’t keeping up with the new weather conditions, First Street says.
Half the people in the U.S. live in a county where a 1-in-100-year flood is at least twice as likely now as it had been in the past, coming once every 50 years instead of every 100 years. In some areas, a so-called “1-in-100-year” rainfall could now happen far more frequently—as often as every 5 to 10 years.
The outdated analysis has serious implications for the way infrastructure projects are initiated and designed. And, because FEMA’s federal flood insurance program greatly underrepresents the number of people that could fall into FEMA’s Special Flood Hazard Areas, millions of Americans may be unaware of their current flood risk.
Inaccurate flood risk data due to underestimating the impact of rainfall also impacts the cost and availability of flood insurance—this is especially true for property that isn’t close to the ocean or inland bodies of water.
The government is working to remedy the situation, though. NOAA, as reported by CNN, says it is working on a revamped approach to its rainfall analysis that is expected to be completed in 2027.