PORTLAND, Ore. - Portland's west hills are notorious for landslides because of the steep slopes in the area and homes perched on hillsides at steep angles.

On Wednesday, a home in the 6400 block of Southwest Burlingame Place broke free of its foundation and slid at least 100 feet down a hillside.

No one was injured but the damage was extensive.  So what about other homes in the neighborhood?  Are they in danger of sliding as well?

Early maps of the neighborhood do show the possibility of slides.  They also show that the home that slid and the two below it were built right on a historic drainage.

"I don't think this is the factor that actually triggered the slide because this house has been sitting here for quite a long time and has made it through some of the biggest storms we have ever seen," said Bill Burns, an engineering geologist for the Oregon Department of Geology and Mineral Industries.

Burns said landslides are products of steep, unstable slopes loosened by moisture.  The west hills of Portland are underlain by loess (windblown deposits known for instability) and the house was at the steeper part of a slope that Burns estimated as 20 to 40 degrees.

How the hillside got wet enough to give way, though, is a question, Burns said.  The Portland area got rain this week but it is just the beginning of the city's notorious rainy season.  So, investigators might look for broken water lines or springs.

The home had recently been remodeled and some work was done on the foundation.

State Mapping Project

State geologists are in the middle of a project to map areas so everyone will know if they are living or building in a slide-prone zone. 

They are concentrating on southwest Portland and Washington County but eventually, the entire state will be mapped.

You can learn more about the mapping project on the Oregon Department of Geology and Mineral Industries Web site. 

Insurance Coverage

Are you covered in the event of a landslide?  If you are relying on a typical homeowners insurance policy, the answer is no.

According to the Northwest Insurance Council and a few insurance companies we checked with, a typical policy excludes movements of the earth, and that means earthquakes and landslides.

Homeowners can purchase additional coverage through a surplus lines carrier, either as a rider or as a difference in conditions policy. Most insurance carriers do not offer the additional coverage.

A less expensive thing that a homeowner can do is to cover their land with plastic during the rainy season or install drainage systems that keep water off their property.