Researchers find flood risk in U.S. much greater than government estimate

July 2, 2020

Researchers found that millions more Americans are threatened by flooding than suggested by government estimates.

A nonprofit research and technology group known as the First Street Foundation used a new model to assess flood risk and found that 70% more properties in the U.S., or 14.6 million properties, face substantial risk for flooding.

The group said its model differs from FEMA’s because it uses current climate data, maps precipitation as a stand-alone risk and includes areas that FEMA has not mapped.

“In environmental engineering, there is a concept called stationarity, which assumes that today is going to be like yesterday, and tomorrow is going to be like yesterday,” said First Street Foundation’s chief data officer Ed Kearns. “This concept used to work, but with a changing environment it’s a poor assumption and no longer does. FEMA’s method assumes stationarity, First Street’s does not.”

Since 1895, the average annual precipitation in Indiana has increased by 5.6 inches, or about 15%, and is projected to continue to rise.

First Street Foundation projections found that 1.7 times the number of properties face substantial risk of flooding compared to FEMA estimates. That number is expected to increase by 4.4% over the next 30 years.

The foundation’s report found that Indianapolis had the greatest number of properties at risk, while Peru had the greatest proportion of properties at risk.

Brownsburg was found to have the greatest relative growing risk over the next 30 years, with a 15% change in the number of properties at risk from flooding.

The foundation has a website where the public can find their own community’s updated flood risk, called FloodFactor.

Locally, Indiana University’s Environmental Resilience Institute has an online tool to help Indiana communities understand how climate change will affect them directly.

The Hoosier Resilience Index makes available community-specific information for every community in the state of Indiana.

Several Indiana cities have partnered with ERI to develop climate action plans.

Researchers find flood risk in U.S. much greater than government estimate