Annenberg Radio News

Scientists talk about the looming threat of megaflood in the American west

A webinar hosted by the Huntington-USC Institute on California and the West discussed the possibility of extreme flood events in the American west

Photo of a flood

California hasn’t seen a megaflood for more than 150 years.

The Great Flood of 1862 killed more than 4,000 people — about one percent of the state’s total population.

Now scientists warn these megafloods could very well happen in our lifetimes along the Pacific coast of North America, including California.

The problem: climate change.

Dr. Daniel Swain is a climate scientist at the Institute of the Environment and Sustainability at UCLA. He spoke at the event today.

“Last summer, some very localized, localized, but quite extreme flooding in places that are normally very dry like Death Valley. And as recently as this past week in the interior southeastern deserts and the Imperial Valley of California. Those are not anywhere near on the spatial scale or magnitude of what happened in 1862. We are getting hints.”

Dr. Swain studies causes and impacts of extreme weather on our warming planet and he told me about the rising risk.

“We think that the the likelihood of seeing an event of this magnitude at some point in the next 40 years typically is about 50 to 60%. So perhaps even more likely than not over the next 40 years, that’s a pretty significant risk cumulatively. And so, again, it could be this year, it could be 10, 20 years from now. But, you know, over time, the cumulative risk goes up quite a bit.”

William Cowan is an affiliated scholar at the Huntington-USC Institute on California and the West. His work blends environmental history, Indigenous studies and critical disaster studies. He offered this advice: “Really know where you live and really know your geography, really know your landscape and know your high ground and you know, know where your your dams and channels are. And also, keep in mind, ARs are historic. They’re powerful, but they’re not all bad. It’s part of the freshwater system. It’s an important part. The rivers in the sky connect directly to the rivers on the land.”

As the world grapples with extreme climatic events, studying the looming threats to prepare humanity sounds more and more like a must, rather than a homework assignment to put on the back burner.

William Cowan: When is a good time to care

Prachi Singh: About the climate change?

William Cowan: Yesterday.