Atmospheric Rivers Provide Important Rainfall, Create Dangerous Flooding
SACRAMENTO (CBS13) — A river of moisture could be on the way this weekend that could provide relief from the drought, but similar rivers have caused dangerous conditions.
On a dry, sunny day, the Merry family enjoys a stroll on the K Street Mall. Little Yuba is about to experience his first big rain, all courtesy of an atmospheric river heading this way.
Hydrologist Allan Haynes says they start with a storm near Alaska in the Pacific Ocean.
"It comes across the Pacific, and it's on a large enough scale, maybe hundreds of miles, that it's able to tap into deep moisture in the tropics," he said.
The moisture is channeled on a narrow path aimed right at California. When it hits the coastal mountains and the Sierra, it's rung out of the clouds and brings big rains.
"They produce like 30 to 50 percent of the annual precipitation," he said.
But too many of them can be a bad thing.
They've been responsible for just about every devastating Northern California flood, like one that hit the Yuba-Sutter area in 1997. In 1861, it rained for 44 days, flooding Sacramento and turning K Street into a waterway. The state Capitol was moved to San Francisco.
Haynes says we usually see a half-dozen events a year, but lately that number has dwindled to two.
"We kinda rely on them, recharge, refill out reservoirs, to put down some high-elevation snow. And use that water as it melts off in the spring and summer," he said.
