Emergency officials preparing for heavy rain, potential mudslides within CZU Lightning Complex burn area

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Workers clear a fallen tree by a storm drain in the Dennis Martin Creek in anticipation of heavy rainfall over the next few days at a Thornewood Preserve entrance along Old La Honda Road in Woodside on Jan. 26. Photo by Magali Gauthier.

Local emergency responders and town officials are preparing for heavy rain and damaging winds — and the potential for mudslides in areas in and around the CZU Lightning Complex burn area — beginning tonight (Jan. 26) as an atmospheric river makes its way toward the Bay Area.

Cal Fire CZU has issued evacuation orders for parts of Santa Cruz and San Mateo counties due to an increased risk of potential debris flow in and around the burn scar. In San Mateo County, the evacuation zones include Coastanoa and Año Nuevo State Park; the communities of Loma Mar, Butano Canyon and Dearborn Park; and Butano State Park. Pescadero High School, which served as a shelter for those impacted by the CZU fires last summer, has been set up again as a temporary shelter for evacuees. (A live interactive map showing debris flow advisories and evacuation warnings and orders is available on Zonehaven’s website.)

Woodside Fire Protection District Chief Rob Lindner said Monday that he didn’t expect communities within the district would see the debris flow that residents closer to the burn scar could see since “we’re on the east side of Skyline (Boulevard).”

“But we have the streams that flow down from Skyline, so we’ll be consistently monitoring that to make sure we’re keeping everyone safe as much as we can,” he added. “Historically where it really impacts us is the prolonged storms.”

The fire district has personnel on standby in case additional staffing is needed, Lindner said.

Cecile Juliette, a public information officer for Cal Fire CZU, said the agency is preparing for the worst case scenario, which could include mudslides and debris flows in and around the CZU Lightning Complex burn area. When the earth gets scorched by fire, it stops absorbing water and holding debris in place, she said. When a lot of rain falls, it can cause the debris sitting on top of the mud to slide down, and mudslides can happen at speeds of 35 to 40 miles per hour, she said.

“One positive thing is we do have the time to plan and prepare,” Juliette said. “If they’ve been given the (evacuation) order, they need to leave.”

According to the National Weather Service, rain will develop in the North Bay this afternoon before spreading south through the Bay Area overnight, with heavy rain and damaging southerly winds. High wind warnings and flash flood watches are in effect throughout the region.

The atmospheric river is forecast to stall over Monterey County on Wednesday, while rain showers will persist throughout the Bay Area into Thursday. Dry weather is expected for much of Friday.

The National Weather Service noted that the heaviest rain should end by around sunrise Wednesday for the CZU Lightning Complex burn area.

“Daylight will reveal what massive logs, debris and mud do when encountered by heavy rain-rates,” the weather service said.

Towns prepare

Sindhi Mekala, a senior engineer with the town of Woodside, said in an email that town crews start preparing for storm season in late October or early November.

They start by cleaning the roadside drainage swales, stormwater inlets, storm drains and culverts and any drainage swales that are part of easements.

Manuel Arellano cuts a fallen tree and Ernesto Espinoza clears the pieces after it was pulled out of the Dennis Martin Creek by a storm drain in anticipation of heavy rainfall over the next few days at an entrance of Thornewood Preserve on Old La Honda Road in Woodside on Jan. 26. Photo by Magali Gauthier.

Sandbags and sand are available at Town Hall (2955 Woodside Road) for residents to use. Hot spots around the town are checked prior to, and during, the storm, he said. Any low-hanging branches or dead trees that might fall into the roadway during heavy winds are trimmed or removed.

A “Winter storm watercourse protection” notice to all residents is available on the town’s website.

In Portola Valley, Public Works Director Howard Young said in an email that the town’s maintenance crews annually prepare for storms by inspecting and cleaning public streets and right of way storm drain ditches and catch basins. Additional street sweepings may occur after major storm events based on conditions and debris, he added.

They try to keep the trail system clear — its water bars, storm drains and catch basins. They also check parks, buildings and grounds’ storm drains, gutters and drainage systems.

Portola Valley also provides emergency sand and sandbag supplies for its residents and restocking materials.

More information is here for Portola Valley residents about cleaning their private storm drains.