First Big Winter Storm May Cause Mudslides in Southern California

Just 10 days ago we had 90+ temperatures with high winds that drove wildfires through the local hillsides and housing developments. Now comes the rain, and given the amount of water that's supposed to fall in the next day or so, mudslides are almost a given:

Residents living near the scorched hillsides of Yorba Linda were buying fences and concrete barriers – even renting tractors – as they prepared Monday for a fast-approaching rainstorm and the threat of mudslides.

City officials there planned to begin calling for voluntary evacuations in some neighborhoods as early as 8 a.m. today, and warned residents not to take the danger lightly. The Orange County Fire Authority was sending swift-water rescue teams to wait for the storm in Yorba Linda, and mapping out possible landing sites for emergency helicopters.

The storm is expected to plow into Orange County late this afternoon and could soak the region through Thanksgiving Day. Forecasters think it could deliver up to 1.5 inches of rain along the coast and up to 2.5 inches in the inland foothills and canyons.

“We aren't sure if the rain will merely soak the ground or cause an entire hillside to come down,” said Dave Gruchow, Yorba Linda's assistant city manager. “It's not an exact science, but we are assuming the worst-case scenario and preparing for that.”

The wildfires that flared across northern Orange County earlier this month stripped away the protective grasses and vegetation that would otherwise hold the hillsides in place. If the rain falls hard enough, it can loosen mud and debris to pour down those hillsides.

On the way back home yesterday we passed through a number of areas that were scorched in the fires last week, including both the Sylmar fire areas and the Brea area where the fire burned right down to the edge of the 57 freeway. This is the first big rain of the winter season (we don't get rain here for the most part from April through October) and with 1-1.5" forecast, things could get pretty dicey.

The first rain of the season also creates more than a little bit of carnage on the freeways. The oil, grease and rubber which has built up on the roads for six months all comes up with the first rain, and Californians don't know how to drive on slick roads. The morning commute on Wednesday could be a real mess.

We're leaving at 5am tomorrow to head back north. Hopefully the rain, slides and highway carnage won't mess up our trip. The good news is this will be a storm with a tropical "fetch", meaning temperatures will stay pretty moderate and there won't be any snow falling over the Grapevine as we try to escape from Los Angeles.