A 1000-year flood that rearranged boulders and buckled roads in Death Valley is the latest chilling window into how poorly prepared California is for the now-inevitable El Niño storms.
The same October weather system that stranded 200 cars in mudslides swamped the desert national park that’s usually one of the driest places in the country. Death Valley usually only gets about 10cm of rain per year. One storm dropped 7.5cm of rain in five hours.
How much water swept through canyons which are normally dry this time of year? According to a report in the Los Angeles Times yesterday, about 2633 cubic metres per second was flowing out of Grapevine Canyon, “10 times that of a 100-year flood.” The terms 100-year flood or 1000-year flood are a way of measuring the size of a flood as related to statistical occurrence in any given year. A 1000-year flood has a .1 per cent chance of happening.
Use the slider to view these USGS images of Death Valley from October 2014 and October 2015
Ranger Paul Forward described the floods this way:
“It started with heavy hail,” he recalled. “Three hours later, the dry wash was transformed into floodwaters 100 feet wide with 20-foot waves. The air was filled with the sounds of massive boulders grinding against each other as they rolled down the canyon.”
Mud and rocks ended up causing severe damage to several sites in the park, including Scotty’s Castle, a 1920’s-era structure that’s a popular tourist site. But the most troubling part is the damage to local infrastructure, which had recently and specifically been reengineered for strong storms. The visitors’s center sewage system was obliterated, and local roads were thrashed:
Just north of Scotty’s Castle, a 100-yard-long section of a newly paved two-lane road designed to withstand severe flooding was lifted up by roiling water, then slammed down on a nearby boulder field.
Can you imagine what would happen if El Niño wiped out a water treatment plant like that in a big city? This is further proof that our best-prepared isn’t good enough for the storms that are coming.
On the bright side, 2016 will be a great year for wildflowers in the park.
Badwater Basin, the lowest point in the US, filled with water
Scotty’s Castle was submerged in up to four feet of mud
Roads remain closed after asphalt was washed away creating six-foot ravines
[LA Times]