North Coast officials on the lookout for mudslides as Wednesday marks the start of the rainy season

North Coast officials have their eyes peeled for potential mudslides ahead of Wednesday's storm, which is expected to drop an inch or more of rain over the next few days on fire-scarred hillsides.

Rainfall is expected to soak local counties ravagewd by wildfires, as well as Butte County, where the most destructive fire in California's history continues to burn.

In addition to claiming lives and destroying buildings, last year's wildfires burned trees, brush and grass, including hillside vegetation that helped stabilize slopes.

“We've lost all of our grasses, all of our trees, all of our shrubbery in some areas,” said Dale Carnathan, emergency manager for the Lake County Sheriff's Office. “It is concerning.”

Lake County is among the areas facing a flash flood watch issued by the National Weather Service. It warned “flash floods and debris flows will be a particular threat in the wildfire burn areas” in Lake, Butte and Shasta counties from Wednesday afternoon to Friday morning.

Carnathan does not expect this week's rain will trigger an emergency response in Lake County. Still, the rains could endanger stretches of Highway 20, including some of the main routes in and out of the county. But those roadways at risk fall under Caltrans' jurisdiction, Carnathan said.

Matthew Rosenberg, a spokesman for the state Department of Transportation, said Caltrans had already done emergency contract work along Highway 20 in areas impacted by the Mendocino Complex fire, which burned about 410,000 acres. The work included removing fire-damaged trees, repairing culverts and planting new trees to control erosion, Rosenberg said.

“I'm told that those trees are mature enough that they should hold back erosion,” Rosenberg said. But, he added, they have crews “ready to go” in case of flooding or mudslides.

Rosenberg said Caltrans was ready with resources and equipment near Butte County's Camp fire and the Woolsey fire in Ventura and Los Angeles counties in case the rain causes problems there.

PG&E in a statement said its crews will be on the lookout for downed trees into power lines or otherwise damaged equipment or interrupted service. The utility company, which faces billions of dollars in liability after its equipment was implicated in many of last year's wildfires, planned to continue cleanup work in the face of the rain.

“PG&E has been preparing for storms such as this for many months,” Michael Lewis, the utility company's vice president of electric operations, said in the statement. “PG&E has a plan, and we want to encourage our customers to have a plan as well.”

Sonoma County officials have been working with property owners and contractors to ensure that proper measures have been put into place to minimize runoff of any hazardous debris that could go into storm drains. They launched a concerted effort in the aftermath of last year's fires to prevent toxic ash from going into the local watershed from rains that came last November.

County Supervisor David Rabbitt in a statement said he hopes the storm system will bring “a slow steady rain that will fill our reservoirs without creating havoc on our roads or elsewhere.” Both reservoirs at Lake Mendocino and Lake Sonoma are near their authorized water supply levels.

Ben Horenstein, director of Santa Rosa Water, said the city has been preparing for the potential that steady rains could loosen the earth where last year's Tubbs fire roared through the northern part of Santa Rosa.

“But (with) the trees that died and the shrubs that died, the roots have lost their grip,” Horenstein said. “And new plantings, if there are any, haven't taken hold compared to what was there previously.”

The city is focusing on keeping stormwater gutters clear, expecting a “higher than normal debris load” because of construction zones and abandoned properties after the fires, Horenstein said. However, he did not believe a mudslide threat was imminent.

He expects the “bone-dry” ground will absorb most of the rain, although debris slides could be possible later in winter, particularly in the burn zones where wildfires roasted trees.

“This is the year to be most vigilant for land movement,” he said.