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ENVIRONMENT
Climate Change Contributed to Oroville Spillway Collapse, Study Says
By Pam Wright
12 hours ago
weather.com
00:46
Oroville Dam Built on Crumbling Rock
A forensic investigation into the Oroville dam failure has uncovered explosive new information.
At a Glance
- Warming in 2017 increased the Sierra Nevada's early‐season runoff by 30 percent, UCLA researchers say.
- As warming continues, the potential for runoff‐based flooding may rise even higher, putting more infrastructure and people in danger.
A new study suggests global warming and its impacts on the Sierra Nevada's snowpack and runoff contributed to the collapse of central California's Oroville Dam spillway in February 2017.
The study published this month in the Journal of Geophysical Research Letters investigated temperature impacts on snowpack and runoff‐driven flood risk in the Sierra Nevada during the extremely wet year of 2016–2017.
The team of researchers from the University of California Los Angeles determined that warming that year increased the Sierra Nevada's early‐season snowpack runoff by 30 percent.
"In the Feather River Watershed, historical warming increased runoff by over one third during the period of heaviest precipitation in February 2017," the authors wrote. "This suggests that historical anthropogenic warming may have exacerbated runoff conditions underlying the Oroville Dam spillway overflow that occurred."
Under a deluge of heavy rain that lasted for days, Oroville Lake to rose to dangerous levels, forcing officials to open the spillway gates. The power of the water released crumbled the patched and repatched spillway and weakened the integrity of the dam. Nearly 200,000 residents living downstream were evacuated.
A 584-page report conducted by an independent forensics team and released Jan. 5, 2018, by the Association of State Dam Safety Officials and the U.S. Society on Dams found that there was no one single factor that led to the collapse of the spillway, but it came from a "long-term systematic failure."
One factor stood out from the report: As crews began constructing the tallest dam in the United States in 1966, contractors warned the California Department of Water Resources (DWR) that the 3,000-foot spillway was being built on unstable ground.
The UCLA study highlights the inadequacies of decades-old infrastructure in the Golden State that were "designed for the climate of the past and not for the rapidly changing climate of the future," Climate Signals notes.
"Our big dams were designed to capture smaller floods than what we expect in the future," said Daniel Swain, a UCLA climate scientist and lead author of an earlier study on California's climate-related weather extremes. "We can make some changes on the margins, but these structures were built for a climate that we no longer have."
The study led by Swain concluded that global warming was leading to a 300 to 400 percent increase in the likelihood of flooding events similar to California’s 1862 Great Flood in the coming decades.
Swain said it was imperative that water officials re-think management strategies with a future, warmer climate.
"Increasing water stored behind California’s big dams gives us a nice buffer against a couple years of drought, but this saved water can become a liability because it reduces the reservoir space available to capture flood water," said Swain. "A higher risk of big floods necessitates bigger safety margins, which means storing less water behind dams for dry times."
As warming continues, the potential for runoff‐based flooding may rise even higher, putting more infrastructure and people in danger, the UCLA researchers warn.
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