Persistent rainfall raises landslide risk in Bay Area

SAN RAFAEL (KTVU) -- The persistent rains in the Bay Area has dramatically increased the chances of mud and landslides and the threat for more slides lingers.

In San Rafael on Tuesday, a home was virtually destroyed when a mudslide crashed into the home as the occupants rushed to evacuate the residence.

The land has not significantly moved around the home in the 300 block of Mountain View Avenue, which was been red tagged along with the home next door.

But there is a possibility that more damage could be done if the hillside, precariously perched above nearby homes in the neighborhood, moves down hill again.

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"If this rain keeps up for another month-and-a-half, I think landslide activity is just beginning," said Eric Olsborg, a geologist for Brunsing Associates.

He said any Bay Area home, business or person near a hill is susceptible to slides.

"We have a number of hillsides that have moved in the past," Olsborg said. "We have landslides (and) people living on landslides that don't even know they're on landslides because they moved and they've dormant for many years," Olsborg said.

The water streaming out of the San Rafael home that was destroyed during the landslide home is likely not just runoff because the muddy red color is a strong indicator that the water is literally eating this hill away.

Geologists say more land is likely to come crashing down.

"There's sub-surface erosion going on which weakens the slope and they're going to be more activity," Olsborg said.

The abundance of water can take long time to drain out and allow the land to restabilize.

"Once the water builds up, they can start moving and continue moving even after the rain quits," Olsborg said, adding that another landslide he worked on continued to move through the summer and into the following rainy season.

By KTVU reporter Tom Vacar.

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