Calif. Storm Prompts Debris Flow Concerns
Tuesday, October 13, 2009
Residents across California worried Tuesday about possible flash floods and mudslides as a storm began showering areas devastated by wildfires.
Sandbagging and other preparations were being made in neighborhoods under threat, including Santa Barbara County and the Los Angeles-area foothills. The rains began before dawn across much of the state but were expected to intensify in the evening and into Wednesday.
"It's something we prepare for every year," Los Angeles County fire Inspector Frederic Stowers said. "We know the fires go through and do a lot of damage. Within L.A. County, much of the slopes burned are going to be critical."
People living around burn areas near the 250-square-mile Station Fire in Angeles National Forest were warned to brace for possible flows of mud, ash and debris with rainfall of up to 4 inches. Los Angeles County's average rainfall for October is less than half an inch.
The Pacific storm was expected to drop 3 to 6 inches of rain in Santa Barbara County, where an 8,700-acre fire burned in May, before it moves on to the San Gabriel Mountains, where the U.S. Geological Survey recently warned of massive debris flows near the areas burned in September.
Debris flows occur because the ground in recently burned areas has little ability to absorb rain, which instantly runs off, carrying ash, mud, boulders and vegetation.
The National Weather Service issued a flash flood warning through Wednesday for the Santa Barbara burn areas. A flash flood watch for the Los Angeles-area foothills was to take effect at 6 p.m. Tuesday and last through Wednesday afternoon.
Stowers said thousands of sandbags were distributed to fire stations throughout Los Angeles County, including more than 10,000 at a station near La Canada Flintridge.
"We try to allocate as many sandbags as necessary to all of our residents," he said. "We've had a lot of fires, not including the Station Fire, close to homes."
Stowers also cited gusty winds forecast throughout the week as a concern, but said mud flows will depend on how much rain the storm brings. Incident management teams were ready to help with possible evacuations, plus swift water teams, he said.
Areas of concern in Los Angeles County include Tujunga, La Crescenta and La Canada Flintridge.
In Northern California, forecasters issued high wind warnings for the mountains, where gusts up to 60 mph are expected, and advisories for lower elevations, where gusts are expected to reach 50 mph.
Some areas in Marin and Santa Cruz counties were deluged by more than 3 inches of rain since the storm swept in overnight.
"There's an awful lot of moisture in this system falling pretty heavily in quite a few places," National Weather Service forecaster Diana Henderson said. "With it being the first significant system of the rain season, drains are backed up, oil and other materials are starting to rise on the streets. It's just ugly out there."
Areas hit by wildfires last summer, including forests in Santa Cruz and Monterey counties, are being monitored for flooding and debris slides. CalFire spokesman Daniel Berlant said firefighters removed dead vegetation and felled trees after the fires to prepare for autumn and winter storms.
"We quickly turn from wildfire response to flood response," Berlant said.
Authorities are warning motorists to drive slowly over San Francisco Bay area bridges where high winds and heavy rains create dangerous conditions.
CHP Sgt. Trent Cross said authorities see about three times as many crashes on wet weather days as on sunny days. He said speed is mainly to blame.
National Weather Service spokeswoman Jamie Stern noted the storm was atypical for the season. She said Los Angeles County's average October precipitation over the past 30 years was 0.37 inches.
"This is generally the type of storm that we would see in January," Stern said. "It came down from the gulf of Alaska and managed to pick up a little extra energy from a residual typhoon that was dying way out in the Pacific Ocean."
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