I was driving in the rain today and wondering when it would start. The Landslides. We who live in Portland Oregon, and have for at least a few years, know that when it rain a lot, the hills give way and houses come tumbling down. I found a great article on landslide prevention, and it happens to be from the Oregonian. Enjoy! Or move to the flat NE PDX like I did.
“Tips on Preventing Landslides
February 9, 2011
By James Mayer, The Oregonian, Portland, Ore.
Feb. 09—Here’s the Number 1 tip for avoiding a landslide: Move to East Portland or Kansas or some other largely flat area.
But if you live Portland’s West Hills, you probably already have most of the natural ingredients for a landslide: steep slopes, heavy winter rains, and the scene of past bill burns, Oregon landslides.
Then if you add in some human triggers, like adding water to slopes, dumping yard debris down a hillside, or removing material at the bottom of a slope, you could really upset the delicate balance of forces holding your hillside together.
“You could move the could move the balance all the way out of whack and have a landslide,” Bill Burns, engineering geologist for the state Department of Geology and Mineral Industries, told a crowd of West Hills residents tonight at the Oregon Health & Science University auditorium.
A panel of experts spoke to the group, organized by the Southwest Hills Residential League.
Burns said the state began studying Portland landslides in earnest after the winter of 1996, when three bad storms caused hundreds of millions of dollars in damage, five deaths, and 10,000 landslides, 300 of them in the Portland West Hills.
That prompted a statewide landslide information database.
And now the state has just released the first new maps from a project using laser beams to map the earth surface, removing the mask of vegetation to see what the ground really looks like. This allows you see where landslides have occurred in the past, Burns said.
“The next step is to use the existing slides and computer models to determine where landslides may occur in the future,” he said.
Burns said floods and earthquakes have been studied much more thoroughly, and the regulations dealing with them are more effective. He hopes that the ongoing landslide studies will improve the environment for more regulation.
One of the stark realities of landslides is most people don’t have insurance that covers them.
Ron Fredrickson, manager of the consumer team at the state insurance division, noted that the typical home owner policy specifically excludes landslides.
It is possible, even common, for home owner to buy earthquake insurance, but landslide insurance is harder to come by.
You must got a specialized type of coverage called “differences and conditions” insurance. It’s not widely available, and not cheap—it might set you back $2,000 to $3,000 a year, Fredrickson said.
A home owner has to make a decision about risk and whether the insurance is worth it, he said, noting however, that the folks who lived on Southwest Burlingame Place whose homes were smashed by a slide in 2008 “wish they had it.”
Doug Morgan, supervising engineer for the city’s Bureau of Development Services, explained that the city’s first building codes were enacted in 1892, but grading and slopes were not regulated until 1972, creating an 80-year legacy of unregulated hillside development in the West Hills.
Since 2002, the city has had a landslide hazard overlay zone that requires new development to have a geotechnical study.
Morgan said the new DOGMI maps could form the basis for new standards.
He offered several tips for home owners:
- Make sure your storm water isn’t emptying out on to a slope. It adds weight to the slope, and weakens the soil.
- Clean gutters and downspouts, and make sure downspouts are connected properly.
- Do a video inspection of your drainage system to check for leaks and blockages, and to make sure the water is discharging in a safe place.
- Turn off all your water, then check your water meter and see it if it still showing water flowing somewhere.
- Clear catch basins
- Check ditches and culverts. Clear if possible, and if not, report to city maintenance bureau.
- Maintain existing vegetation.”
To see more of The Oregonian, or to subscribe the newspaper, go to http://www.oregonian.com.
Copyright (c) 2011, The Oregonian, Portland, Ore.