It’s been quite some time since California got a good soaking and this last series of storms has definitely left its mark. Just this morning an additional 15 gates were opened on the Sacramento Weir.
“Excuse me? Sacramento Weir?” We’ve been hearing this a lot the past few days at Cal OES. Even from residents in the Sacramento region. So, we thought it would be helpful or at least interesting to explain what all this “Weir” talk is about.
Sacramento Valley has a history of floods that goes back as long as people have populated the region. Prior to flood management, the Sacramento Valley would become an “inland sea,” nearly every year during the winter months.
In fact, in January 1850, a major flood devastated the new city of Sacramento, as well as other low lying towns in the region. Then again, in 1862, the largest flood in California’s recorded history, also known as “The Great Flood,” inundated the Sacramento and San Joaquin valleys for an extent of 300 miles. It was so bad that state government was forced to relocate from Sacramento to San Francisco for 18 months.
In order to control these storm flows, the Sacramento River Flood Control Project was created. And in 1916, the city built the Sacramento Weir to protect itself from excessive flood stages. In the following decades, the state added 5 more weirs upstream.
The Sacramento Weir is the only weir that is manually operated, all others overflow by gravity on their own. It consists of 48 wooden gates that divert Sacramento and American River floodwaters to the west down the mile-long Sacramento Bypass to the Yolo Bypass.
The Department of Water Resources operates the weir, but before the gates are unlatched, specific protocols set by the Army Corps of Engineers must be met. For one, the river must reach 27.5 feet at a specific gauge with a forecast to continue rising. Because the weir’s gates must be manually opened, they must be manually closed, too. And that cannot be done until the water recedes below the weir gate levels of 25 feet.
There are currently 35 gates open and floodwaters are flowing into the Yolo Bypass. However, additional gates may be opened if the river continues to rise in order to reduce the risk of urban flooding.
Watch the video below, which is a compilation of the sights and sounds of the latest round of Sacramento Weir gates being opened on January 11, 2017.