This article from the Sacramento Bee reports why it is imperative to build Auburn Dam quickly.
It was the greatest flood in recorded California history, 43 days of rain and snow that swamped the state, killed thousands of people and forced the newly elected governor to take a boat to his inauguration at the Capitol.
Now a group of climatologists says global warming will increase California’s risk to repeat performances of the devastating flood of 1862.
In a study published Monday in the scientific journal Nature Climate Change, the scientists say climate change will increasingly expose California to a phenomenon they call “precipitation whiplash,” in which drought or drought-like conditions will alternate with intensely rainy winters. Rain and snow will become concentrated in narrow windows of time at the peak of winter, instead of being spread between October and April.
Californians already got a taste of whiplash in the winter of 2017, when the wettest winter ever recorded in Northern California snapped the historic five-year drought, the article said.
“The already distinct contrast between California’s long, dry summers and relatively brief, wet winters will probably become even more pronounced,” the scientists wrote.
When scientists discuss climate change’s impact on California, they usually talk about worsening droughts: Warmer winters will diminish the Sierra Nevada snowpack, the argument goes, making it harder to store precipitation for the summer months that follow. Hotter summers will put additional strains on water supplies.
The Nature Climate Change article shines an uncomfortable spotlight on California’s flood risk from climate change. “In some circles the increasing risk of flood could have been overlooked to date,” said UCLA climatologist Daniel Swain, a co-author of the article.
The article’s conclusions could be particularly troubling for Sacramento, which is generally considered the second-most flood-prone major city in America after New Orleans.
The region has spent $2 billion in the past 20 years to strengthen levees along the Sacramento and American rivers, and reduce other vulnerabilities, but the risk remains significant. Portions of the region still lack 100-year flood protection, including 25 percent of the city of Sacramento. That means those areas couldn’t withstand a storm with a 1-in-100 chance of occurring in a given year, and property owners in those areas generally are required to buy flood insurance.
The Sacramento Area Flood Control Agency, or SAFCA, says it is committed to achieving a minimum of 200-year flood protection, the threshold established by the Legislature in 2007. A total of $2.4 billion worth of projects is in the pipeline, including work on levees around Natomas and Arcade Creek that’s scheduled to begin later this year. SAFCA also is working with federal officials on a plan to raise Folsom Dam, which could push the region’s flood protection to as high as 300 years.
Yet much of the work on SAFCA’s to-do list is years from completion. And even 300-year flood protection might not be enough. Experts say a mega-flood similar to 1862 could overwhelm even the most advanced levees and other defenses. The U.S. Geological Survey, in a 2011 study, said the 1862 disaster was probably a 500- or 1,000-year storm.
The 1862 storm was pure catastrophe. “Drowning deaths occurred every day on the Feather, Yuba and American rivers,” the magazine Scientific American recalled in a 2013 article. “In one tragic account, an entire settlement of Chinese miners was drowned by floods on the Yuba River.” The water was 30 feet deep in some places, and Gov. Leland Stanford took a rowboat from the governor’s mansion to his inauguration.
Although flood control obviously has improved since the 19th century, there are now millions of people and billions of dollars of property in close proximity to levees and reservoirs. The Geological Survey’s study said a storm akin to 1862 could cause $400 billion in property damage statewide and another $325 billion in business-interruption expense.
“We’re absolutely not ready for a storm that size,” said Jeffrey Mount, a water expert at the Public Policy Institute of California. Mount didn’t contribute to the Nature Climate Change article but is familiar with its findings.
Retrieved April 23, 2018 from http://www.sacbee.com/news/state/california/water-and-drought/article209325929.html