Before and After: Photos Show Mudslide's Destruction [60 Miles N.E. From Seattle]

NBC News ^ | 24 March 2014 | Jon Sweeney

[zeestephen]

A mudslide in Washington state turned a square mile of Snohomish County into complete devastation and claimed the lives of at least eight people and destroyed dozens of homes. The slide, which occurred around 11 a.m. PT Saturday, turned land that spanned neighborhoods into "quicksand." [18 more "missing"]

[Jack Black]

I seem to recall that one Love Creek home was buried with the occupant inside, and was left as is and is now a gravesite.

I believe more than one. Some were under 100 feet of dirt and mud. It would have been hazardous to try to try to dig them out, so no effort was made. There are now memorial markers there for those buried in the disaster.

I suspect something similar may happen now in Washington.

[Clinging Bitterly]

Vegetation is good BUT this had been made into a residential area and the excavation of roads, homesites and etc. effectively cut apart the naturally stabilizing mass of vegetation. Just one small weak spot can let go and there will be a cascading effect, not only from the force of gravity, but the effect of vibration which makes solid earth behave as though it was a liquid. It is a phenomenon which is almost unimaginable, and you aren't going to prevent it with the usual treatment of wire mesh and retaining walls or berms of rip rap laid on the surface, as solid as they may seem (earth just flows under and around them like water).

Without massive support structures built deep into the ground (to, and anchored in solid rock), any hillside is prone to slide if it is disturbed enough and/or it collects enough moisture.

Slide events this big happen daily in the Northwest during the rainy season, just not usually in suburban residential enclaves such as this. But, particularly as the Portland and Seattle areas have expanded in population and the semi-rural hills have become the new suburbia, we will see them more often.

[Clinging Bitterly]

Already happened in 1980 with Mt. St. Helens. A huge swath of landscape from the west slope all the way down through the Lewis and Toutle drainages to the Columbia River was drastically altered. Could have been much worse but still, a lot of places along I-5 where we used to look down, now we look up (and vice-versa).

[21twelve]

Tacoma for sure, as it has in the past. I have heard of contractors having trouble putting in sewer pipes and stuff due to all of the logs in their new development. Logs that are in the old mudflows that are 20 - 30 feet thick. The most recent being about 500 years ago.

Excellent point. Will sadly make this landslide look small. However, they are increasing their monitoring of Mt. Rainier, and do more drills and planning for fast evacuations up to high ground. So hopefully that will work well when it occurs.

[21twelve]

http://seattletimes.com/html/localnews/2023218573_mudslidewarningsxml.html

Here’s a link to a good article on the history of the area. I guess the idea of nobody could imagine a slide this big is wrong. Numerous studies, beginning in 1949, indicate they knew this had the potential for a large event.

[EternalHope]

Very interesting link. Thanks for posting.

The article makes the point that engineers SHOULD have known this was a dangerous area, at least according to some experts. Obviously the experts who warned of the danger were ignored. The people who lived there thought it was safe, as did (apparently) all of the people who have been giving news conferences the last few days.

Interestingly, the escarpment on the slide this week was 600 feet high (!), four times higher than the previous high for this spot. I have to wonder if the efforts to shore up the slope kept it from having a series of smaller slides that would have periodically relieved the stress, with a single, much bigger slide as the end result.

I’m not surprised people wanted to build there. It is an amazingly beautiful area. Plus you can fish from your backyard. Salmon and steelhead. What’s not to like?

We live in a similar place, including fishing from our backyard. We love our location although it is not quite as scenic. Our house is way above the flood plain, and it would take a slide similar to the one at Oso to reach us.

Update on the death toll: They have now found 14 bodies, and the missing person list is up to 176. Hopefully some of the missing people will turn up, but it’s clear a whole lot of people died.

[21twelve]

“I have to wonder if the efforts to shore up the slope kept it from having a series of smaller slides that would have periodically relieved the stress, with a single, much bigger slide as the end result.”

Good point - perhaps. Although I think the slide in 2006(?) released a lot of material that had been helping to hold up the recent slide zone. More than what a “little” wall could make up for. The new wall sounds like it was designed to keep soil material from getting into the river and messing up the fish habitat, rather than trying to contain the major slide.