L.A. County Blamed for Landslide Damage : Housing: A geologist for Calabasas and Agoura Hills says guidelines allow building in unsafe areas. Another expert disagrees.


The recent spate of landslides in Agoura Hills and Calabasas may have been the work of nature, but a leading geology consultant said Monday that poor planning and faulty engineering are to blame for damage to houses and roads.

Former state geologist Jim Slosson laid much of the blame for the recent slope failures at the feet of Los Angeles County officials, who gave the go-ahead to build all of the homes threatened or destroyed by moving earth.

In the past several weeks, two houses in Agoura Hills have been rendered unlivable by landslides. Several more are threatened by shifting dirt. And geologists warn that additional saturated hillsides probably will give way even after the rains subside.

Slosson, now serving as city geologist for Calabasas and Agoura Hills, claimed the county’s geology guidelines are too lax and allow building in slide-prone areas without proper safeguards. Both cities were under county jurisdiction until they incorporated to exert control over land-use decisions.

“If good planning had been used and good engineering had been used, 90% of these failures would not have occurred,” Slosson said, adding that the remaining 10% were in areas that never should have been developed in the first place.


County geologist David Poppler disagreed, explaining that the county requires builders to file detailed geology reports for new projects, and to stick by them. But, he said, “slopes do fail. Calabasas and Agoura Hills are not unique.”

Poppler concluded that “there will always be differences of opinion as to how much is enough. Some people are more conservative than others with regard to what they feel is adequate.”

Hundreds of hillsides slide each year in remote areas all over Southern California, which is crisscrossed by a virtual freeway map of faults and mountain ranges.

So the same dramatic mountains that make Calabasas and Agoura Hills beautiful places to live also make them potentially treacherous places.

“It really is very simple,” said Donn Gorsline, a geology professor at USC. “If you look at slopes and think there is the potential for slides, you are going to have slides. It’s that simple. It’s a fact of life.”

But the threat of slope failure grows when hillsides are altered to make way for roads or houses. Faulty grading and reinforcements often do not become apparent until the earth is saturated by water, increases in weight and begins to slide downhill.

Then it is too late.

Slosson said that the threat can be eliminated when proper safeguards are taken. That includes not building in some areas. He pointed to geology guidelines in the city of Los Angeles--stricter than those in Los Angeles County--as an example.

Just one slide has been reported in the portion of the Santa Monica Mountains under the control of Los Angeles. That one, in Studio City, forced the evacuation of several residents after one house was damaged and five others were threatened.

But that is little consolation to Calabasas resident Mark Hayes, whose three-bedroom house on Valdez Road in Old Topanga is threatened by sliding earth. Hayes knew there were landslides all around him so he went above and beyond what was required of him by the county.

“There’s enough concrete and steel in here to build four houses,” said Hayes. “You never think in your wildest dreams that it’s going anywhere, but then it does. Now I don’t know what we’re going to do.”