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Home » Level 5 atmospheric river to trigger drought-affected flooding in California

Level 5 atmospheric river to trigger drought-affected flooding in California

Filled with a classic atmospheric river pattern, the storm could cause flash flooding and dangerous debris flows across a large portion of the region that has already been ravaged by recent wildfires.

With each successive storm, the potential for moisture increases, culminating Sunday with a possible Category 5 atmospheric river event.

“An environmental river designated as Category 4 or 5 is capable of producing significant rainfall over three or more days, perhaps more than 10-15 percent of a normal year’s rainfall in some locations,” Marty Rolfe, said the director of the Center for Western Weather and Water Extremes at UC San Diego.

An atmospheric river is a narrow band of moisture that is concentrated in the atmosphere, crossing a distance of more than two miles from the ocean. They can be transported in vapor form, which is 20 times as much water in the Mississippi River, as in liquid.

By the time it arrives Monday morning, the parade of storms could drop 8 to 12 inches of rain in parts of Northern California and add 1 to 3 feet of snow to the High Sierra. For a drought-prone area, one foot of rain is too much, too fast, and too soon and will likely cause runoff, flash flooding, and debris flows in burn-scarred areas.

Race to stop the waste flow

Burn scars, the scorched landscape left behind by the Dixie fire, near the Mount Leeson and Caldor fires, not far from South Lake Tahoe, are susceptible to flooding and debris flows. . This deadly and fast-moving mass of water, rock, soil and vegetation can wreak havoc on downstream communities, destroying homes and infrastructure. These geological hazards are a byproduct of burnt soil, which can be as waterproof as pavement. Rain that would otherwise be absorbed by the soil can now run off quickly after a fire.

An emergency response team in the watershed, led by Cal Fire, is deployed in advance of heavy rains to assess post-fire hazards, such as debris flows, flooding and identify areas most susceptible to rain. Is.

“Erosion in the sharpest and most severely burned parts of a burn area is the most difficult to treat, and usually poses the greatest risk to life, safety and property,” says Lynette Round, Cal Fire’s communications manager. happens.”

“Areas of concern are those with hazard values ​​(houses, roads, etc.) under burned steep areas with moderate to high ground gravity,” Round says. “For the Dixie Fire, it will be primarily along the Highway 70 corridor and parts of the Indian Valley and Genesee Valley. For the Hat Fire, it will be along parts and areas of the Highway 50 corridor. Below the Cosumnes River. ,” adds the round.

You don’t have to look far to see such devastation in California. In January 2018, weeks after the Thomas Fire scorched the hills of Santa Barbara County, people living on hillsides in the burned areas were devastated by multiple debris flows after powerful January storms hit them. …

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