FLOODSFlooding in California: What Went Wrong, and What Comes Next
Battered by storm after storm, California is facing intense flooding, with at least 19 lives lost so far and nearly 100,000 people evacuated from their homes. And there’s no sign that the storms will be letting up soon.
Battered by storm after storm, California is facing intense flooding, with at least 19 lives lost so far and nearly 100,000 people evacuated from their homes. And there’s no sign that the storms will be letting up soon.
Below, experts from across the Columbia Climate School help to explain this devastating weather and what it means in the broader conversation of climate change and disaster response.
Unusual, but Not Unheard of
“The floods are due to recurrent waves of atmospheric rivers that typically lead to very high rainfall. These are not unusual for California,” said Upmanu Lall, an engineering professor and director of the Columbia Water Center. Atmospheric rivers are air currents that carry large amounts of water vapor through the sky.
Modeling by the U.S. Geological Survey predicted a devastating scenario like we’re seeing now, Lall said. The projections were based on the storms that caused disastrous floods in California in 1861-62.
“There is sedimentary evidence from a UC Santa Barbara study that such a phenomenon recurs in California about every 250 years,” Lall added.
El Niño/La Niña Effects
El Niño and La Niña — climate patterns in the Pacific Ocean — can influence where atmospheric rivers make landfall, and how frequently, said Lall.
He explained that atmospheric rivers are born in the warm waters of the tropical Pacific. During the La Niña phase, atmospheric rivers will typically be born in the western Pacific and make landfall on the northern part of the U.S. West Coast. Conversely, during an El Niño phase, atmospheric rivers are more likely to be born in the central or eastern Pacific, and make landfall in Southern and Central California.
“As the Pacific transitions from La Niña to El Niño, which may be happening now, the birth locations and the landfall locations can shift to intermediate locations and one typically gets this sequence of events that can cover different parts of California,” said Lall. “The reason this is critical for flooding is that we get several such storms spaced a few days apart from similar birth locations.”
Forecasts vs. Preparation
The US Geological Survey modeling and past disasters made it clear that this type of weather was possible, and that local agencies should be prepared.
