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Here's how California's flooding risk could be higher than we think

New study raises concerns over California's flood risk
New study raises concerns over California's flood risk 02:53

SACRAMENTO — A national flood assessment tool could be out of date. A new study says this tool is not taking into account how many more severe events are happening because of climate change and how new construction could be at a higher risk. 

The study by the First Street Foundation found that 1-in-100-year events are now expected more often because of climate change. Their research found people across the country are now being affected in a way they weren't 20 to 30 years ago. 

"It feels like the 1-in-100-year event occurs every ten years in some places it is because we're not measuring it accurately," said Dr. Jeremy Porter, the head of climate implications research at the First Street Foundation.

The tool many use to track heavy precipitation and flooding risk is from the National Oceanic and Atmospheric Administration, or NOAA, and is called Atlas 14. States across the country use it to inform the engineering design of transportation infrastructure, such as roads and bridges.

In the study, they compared NOAA's Atlas model with First Street Foundation's new precipitation model that incorporates the effects of a warming climate.

It found that over half the population, roughly 51% of Americans, live in areas that are now twice as likely to experience a severe "1-in-100-year flood" event as expected from Atlas 14.

Porter said the way NOAA has been tracking these events, especially heavy rainfall events and flood risk, is not keeping up with our changing climate. 

"Those heavy, heavy events we have been seeing in the past few years just weren't being captured in the record and NOAA also, because of funding primarily, produced these results in sort of regions one region at a time," Porter said. "As we started to produce these models in different regions, you would start to see these man-made boundaries at a state where precipitation estimates in one state were different than estimates in another state, which has to do with how the models were created."

This means an area's risk could be higher than depicted in NOAA's model. 

CBS13 reached out to the National Weather Service for comment about their Atlas product, and they said they are in the process of an update. 

"NOAA is in the process of developing Atlas 15, which will incorporate historical changes in rainfall intensity since the release of Atlas 14 volumes, as well as modeled estimates of future climate conditions," said John P. Moore III, a public affairs specialist and meteorologist with the National Weather Service.

But the new product would not be released until 2027 after it undergoes testing and additional data additions. 

"This in no way substitutes for the rigor of the Atlas product suite, but it does provide an opportunity to use our observations, trend analysis and climate models to test methodologies that will most accurately reflect our future climate," Moore said. 

Yet, Porter said it still leaves some Northern California areas at a higher risk than they thought. 

"Around the mountains and you could see on the east side of the mountains and right on the Nevada/CA border there were these pockets where we saw a huge underestimation of risk in that area," Porter said. 

A concern highlighted by the study is the recent funding for infrastructure projects through the Infrastructure Investment and Jobs Act (IIJA). The First Street Foundation says the majority of those projects will require significant engineering expertise, including the development of design standards to withstand climate-related risk exposure today and into the future.

"It means that all of the infrastructure that we are building over the last 20, 30, 40 years has been designed to a standard to remove excess water and excess precipitation to protect both roadways to protect city streets, to protect communities at large. We are not designing them to the proper standard because the tools we are relying on are out of date due," Porter said.

First Street Foundation said they have opened up using their model to the National Weather Service until the new Atlas model is created. 

There has been no word yet on if the National Weather Service will take them up on this offer.

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