FEMA flood maps are based on historical observations only and don't include current and future risks like observed sea level rise. 75% of them are out of date and 16% of those are from the 1970s or 1980s1. Over 40 million Americans have a 1% chance of flooding from heavy rainfall in any given year, yet FEMA maps only identify 13 million– leaving more than 27 million people unaware of their real flood risks 2.
Over the course of a 30 year mortgage, these 40 million at-risk Americans have a 1 in 4 chance of flooding from rain alone, and may have additional flood risks from high tides and storm surge. As sea levels continue to rise, sea surface temperatures continue to increase, and the atmosphere continues to warm, floods will increase in both frequency and severity, putting more and more Americans at risk.
First Street Foundation is a registered 501(c)(3) tech non-profit that quantifies and communicates the increasing risks associated with sea level rise and flooding. We do this by conducting breakthrough research, and translating the results through digital tools that simplify and visualize.