On Monday, February 7th, freeways in northern California were jammed with 100,000 people rushing to escape a possible flood, as a 30-foot wall, holding back gallons and gallons of water, might collapse. They’d been directed to leave their homes and head toward the Chico Silver Dollar Fairgrounds—a designated evacuation spot for the area. How does something like this happen?
Well, if you live in California, you might know that the Golden State was facing a drought in the last couple of years. Where a drought is a problem of not enough rain or water, Californians now have the opposite problem: too much water. With unexpectedly high rainfall, the Oroville Dam, about 75 miles north of Sacramento, was getting pretty full. What happens when dams get full of water and they can’t hold it any more?
The Oroville Dam has what is called an auxiliary (or additional) spillway. This is for all the extra water to spill into if the levels get too high. It’s basically like a moat or trough with big, 30-foot walls on either side to hold the water in.
But on February 7th, as water owed into the spillway, part of the wall unexpectedly collapsed. The concern was that if the hole in the wall got any bigger, the entire wall might come down, sending too much water into the river, and flooding Oroville and other towns. Fortunately the damage to the spillway was repaired, the evacuation was lifted (or called off ), and people returned to their homes. It’s a fortunate ending, but experts are keeping their eyes on the dam and making sure that the repairs hold for future storms.