Rain forecast in L.A. sparks fears of mudslides, traffic gridlock

It’s poor form to complain about rain, even a whole lot of it, when you really need it.

So Southern California will just have to grin and bear it beginning Wednesday night when the first of two major storms move into the region.

The storms are expected to deliver the largest rainfall since the spring of 2011. It comes as Southern California and most of the state struggles through a historically dry stretch. Last year was the driest calendar year in L.A.’s recorded history. Since the beginning of the rain year in July, only 1.2 inches of rain have fallen in downtown L.A. Now it’s going to rain -- a lot -- with possibly more than four inches pouring down in some valley and foothill areas as a result of the second storm.

PHOTOS: Los Angeles prepares for rain storms

“It’s been almost three years since we’ve had rain like this,” said Bill Patzert, a climatologist for Jet Propulsion Laboratory in La Cañada Flintridge. “This is not a February or March miracle, but any rain is sweet, because everything is so dry.”

So much rain in such a small period of time has firefighters, public works and law enforcement officials girding for the inevitable problems involving traffic, accidents and possible mudslides.

“We haven’t had weather in a while,” said L.A. County Fire Department Inspector Tony Akins.

While the rain is badly needed, it would take several seasons of above-normal rainfall to bust the drought gripping California.

Eleven of the last 15 years have seen below-normal rainfall, making dry weather the norm over an extraordinarily long period, he said. Even if L.A. got two inches of rain, the city would still be only about 30% to 40% of normal for this time of the year.

Stuart Seto, a weather specialist for the National Weather Service in Oxnard, said the storm expected to hit the region Friday could linger through Monday. He said the heaviest rain should fall Friday morning through the afternoon.

The rain should help replenish some groundwater storage basins, bring temporary relief to desiccated foothill areas that are prone to wildfires and add snow to mountain areas. In the meantime though, it’ll bring some complications.

Law enforcement and fire officials expect an uptick in traffic accidents as the long-awaited rain mixes with accumulated oil on roadways to create an extra slick surface. The risk of vehicles hydroplaning and crashing increases under these conditions. Like many agencies, the L.A. County Fire Department is working with the National Weather Service to calibrate staffing and strategy, Akins said.

“We’re in constant communication with the National Weather Service as part of our routine operations,” he said.

He said inmate crews at fire camps are prepared to respond to a variety of potential issues, such as mudslides, debris flows and flooding. Areas that have been razed by wildfires, such as the hills above Glendora, are especially vulnerable to these because fire renders the ground moisture-averse, causing rainfall to slide downhill. Akins said fire stations will pass out sandbags to residents who request them.

Chris Jeffers, city manager for Glendora, said the city has an alert system to let residents know if they need to evacuate or take other action. He said the city is in contact with weather and county fire officials, L.A. County flood control, the U.S. Forest Service, police and other agencies. Jeffers said the Colby fire, which scorched nearly 2,000 acres last month, had “severely damaged” the hills above Glendora.

“The fire and severity are very reminiscent of the 1968 fires which led to the horrific debris and mudflows in 1969,” he said. “More damage was incurred to property as a result of the 1969 mudflows than the fire itself.”

Jeffers said the forecasts don’t suggest there will be “substantial negative impact on the burn areas” from the first storm. But he said the city is more on guard for the second rain event, which is expected to include thunderstorms.

“This is the storm that has us concerned at this point,” Jeffers said.

He said that officials from the county’s flood control department have helped the city do survey of residents within the burn area, visiting about 150 homes, to offer advice on how to mitigate risks to their properties. They have also visited about 60 residents who might need assistance in case of an evacuation order, Jeffers said.

Patzert of JPL said one of the problems that surface when it hasn’t rained in a long time and then rains a lot is that storm sewers haven’t been flushed out -- and suddenly they can get overwhelmed. Some degree of flooding could probably happen even in urban areas, he said.

With the rains coming, law enforcement officials are warning people to slow down on streets and freeways and to clean gutters. But with Southern California stuck in a dry rut for so long, county Supervisor Don Knabe reminded people that they also need to shut off their sprinkler systems.

“Your yard won’t need to be watered until later next week,” he said. “At the very least.”

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