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An unexpected item is blocking cities’ climate change prep: obsolete rainfall records

Published on February 15, 2022

In Seattle, the 1-in-25-year storm could be more than 20% worse by the 2080s. Image Credit: Peter Mooney (CC BY 2.0)

American cities are poised to spend billions of dollars to improve their water systems under the federal infrastructure bill, the largest water investment in the nation’s history.

Those new sewers and storm drains will need to withstand rainfall that’s becoming more intense in a changing climate. But as cities make plans to tear up streets and pour cement, most have little to no information about how climate change will worsen future storms.

Many cities are still building their infrastructure for the climate of the past, using rainfall records that haven’t been updated in decades. Those federal precipitation reports, which analyze historical rainfall data to tell cities what kinds of storms to plan for, are only sporadically updated by the National Oceanic and Atmospheric Administration.

Rainfall reports for some states are 50 years old, which means they don’t reflect how the climate has already changed in recent decades. And states themselves have to pay for those updates.

In the Pacific Northwest, both Portland and Seattle partnered with the University of Washington’s Climate Impacts Group. The research team created an online tool so cities in Oregon and Washington could see how extreme rain would shift. In Seattle, the 1-in-25-year storm could be more than 20% worse by the 2080s.

Realizing the scale of that change, Seattle enhanced a major stormwater control project that was underway. The Ship Canal Water Quality project was planned with a 14-foot diameter tunnel, designed to capture stormwater so the system isn’t overwhelmed in big storms. The climate change projections spurred the city to upsize it to 18 feet wide.

“We’re thinking this is a 100-year investment, so we need to be using our best information about what 100 years is going to look like and not designing things now that will be obsolete,” says Leslie Webster, drainage and wastewater planning manager at Seattle Public Utilities. “We’re confident that the change in sizing will provide a lot more resilience in the future. But, you know, it also increased the price tag significantly.”

Continue reading at NPR

Originally written by Lauren Sommer for NPR
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