LAKE OSWEGO, Ore. -- The fact that homes in Lake Oswego were damaged by slides this week came as no real surprise to Portland State geology professor Scott Burns, who studies landslides.

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Sky-8 photo

The mud slide hit the back of the Lake Oswego home.

He says Portland is one of the prime landslide areas in the nation. But the state doesn't require residents be warned that their homes sit on a high hazard site.

He said the main ingredients of slides are loose soil, steep slopes and water and that Oregon has plenty of all three.

After landslides killed five people in 1996 in Western Oregon, the state launched a plan calling for landslide hazard maps. State geologists developed taxpayer-funded maps but the state never formally adopted them after some city and county officials complained that they represented a regulatory headache that might restrict development.

The maps label large portions of hilly areas, including chunks of Lake Oswego and Portland's West Hills, as hazardous.