Extreme precipitation risks currently underestimated

A database that infrastructure planners use to determine how best to design a bridge, building or new tunnel vastly understates the risk of extreme precipitation events, a report shows.

The big picture: The current NOAA precipitation expectations, used to determine the risk of a "100-year" rainstorm and even rarer events, are not keeping pace with the warming climate, the First Street Foundation concludes in an analysis.

• The report uses a new, peer-reviewed flood model to examine how climate change already has shifted the odds of extreme precipitation events across the U.S.
• It compares the model's findings with what is contained in the NOAA database, known as Atlas 14.
• The climate change-related trends are projected to continue as warmer ocean and air temperatures provide more water vapor for storms to convert into heavy precipitation.

Between the lines: First Street shows that more than 51% of Americans live in an area now twice as likely to experience a 1-in-100-year flood event, compared with expectations from Atlas 14.

• The biggest positive corrections to NOAA's data came in the Northeast, Ohio Valley, and Texas and Louisiana coastlines.
• Some areas saw decreases compared to Atlas 14, including parts of the Plains and intermountain West.
• Studies show that climate change is increasing the frequency and magnitude of precipitation extremes, along with contributing to hotter, more frequent and long duration heat waves as well as stronger hurricanes.

NOAA is in the process of updating its database for Atlas 15, but this is not expected to begin rolling out until 2026.

• The government's outdated estimates may help set the design standards for the vast sums of infrastructure spending in the Biden administration's climate and infrastructure laws.
• If that is the case, it would mean many large projects would be outdated and vulnerable as soon as they are completed, First Street founder and CEO Matthew Eby told Axios in an interview.

Yes, but: Besides First Street, a nonprofit, many climate startups exist to help prepare companies and communities for changing risks where existing data falls short.