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"Slip, sliding away..."
03-29-2013, 11:12 AM, (This post was last modified: 03-29-2013, 11:34 AM by Skook.)
"Slip, sliding away..."
On Wednesday, March 27, 2013 at 4:00 am a massive landslide occurred on Whidbey Island in Washington State. If for some unbelievable reason this is news to you, here is a picture of that slide.
[Image: attachment.php?aid=64]

Those were expensive view properties on top of the bluff - one report says Microsoft CEO Steve Ballmer has a property there. Many have lost half or more of their property, and some of the homes will never be lived in again. The road on the left is the only access road for a string of beach front homes below the bluff and seventeen of those homes are now, for the time being, water-access only.

What do you think the value of those homes above and below the bluff is now? Zilch. Can the owners expect to get any insurance money? If they do, they are dreaming because this “event” will be ruled an “Act of God” and AOGs aren’t covered. What about the value of the properties on the other side of the road on the bluff? Will anyone want to buy them in the future? Maybe, but they are a whole lot cheaper now because I don't believe there is anything that can be done to stabilize that bluff.

The next images show what is happening below one of those affected properties. Those red arrows point to three areas of water seepage and it is this that undermined the cliff face and caused the landslide. Can the authorities find the source(s) of this water and divert it? Possibly, but at what expense and if it could be diverted it would only become someone else’s problem somewhere else.
[Image: attachment.php?aid=65]
I was curious to see what the soil looked like under these homes and the pictures below speak volumes. The first picture on the top right is the soil below the house above. You can see a depressed area on the right which to my eye looks like a sink-hole (a warning sign of problems for sure). You can also clearly see distinct layer upon layer of soil deposits.

The two other images are below another property and again there is water seepage and it is clearly occurring across a layer of deposit. The close-up of the shed that went for a ride gives a good idea of the nature of those layers - gravel, sand and clay.
[Image: attachment.php?aid=66]
The major media reports that came out the day of the slide quoted many of the homeowners who talked about how wet the winter was and how much rain had fallen over the past few days. However, it was the next day on the 28th that a small independent newspaper in east Snohomish County, the Sky Valley Chronicle, that printed the real reason for the slide and the title of the piece might have surprised most: “WHIDBEY ISLAND LANDSLIDE CONNECTED BY TIME TO EVENT 15,000 YEARS AGO.”

Here is an excerpt:

Quote:The slide reportedly was not triggered by massive rainfall in the last few days but by the geology of the area itself, according to geologists who understand the region. The soil there is inherently unstable due to the fact it is part of the ancient Vashon Glacier. With water peculating through it over time, steep hillsides become unstable and can give way with no warning.

About 15,000 years ago the Vashon glacier which covered a vast area of Washington State began to melt and recede from land that thousands of years later we would call the Puget Sound region and the Columbia Basin region in Eastern Washington. By 11,000 years ago, the glacier has retreated to the border of present-day Canada. During its advance, meltwater flowing under the ice sheet had carved out Lake Washington, Lake Tapps, Lake Sammamish, Puget Sound, and Hood Canal, according to and a piece written by Jennifer Ott.

After the glacier had retreated it left behind, in places like Whidbey Island, unstable geology due to a sandwich like composition of glacial till on top of the earth that holds everything up, then below that a layer of sand and below that a layer of clay. And over time as water peculates through that sandwich it makes the land unstable and prone to slides.

I have no doubt there were home owners in North and West Vancouver who looked around their properties and felt a little sick. I am also certain there were some on the Sunshine Coast who did the same. In fact, I can think of two areas off hand on the SC that somewhat mirror that Whidbey Island locale. Here’s two Google Earth images showing those areas.
[Image: attachment.php?aid=67]
The top image is Gibsons. The majority of the town is actually built on a plateau as anyone getting off the ferry at Langdale knows because you drive up a steep four lane road from the ferry terminal to connect to Highway 101 via North Road. In the picture, that plateau is a darker shade of green to what lies below long the coastline and there are homes built following that lower strip. After a decade of trying, a big development has finally been given the green light for the Gospel Rock area and I wonder if they have started to cut down the trees.

The second area is Selma Park and this is in the District of Sechelt. Heading north on the highway, you drive at sea level along Davis Bay which is on the right of the picture. You then take a brief steep climb up onto a ledge where older wood frame homes are built along both sides of the highway. However, on the left (west) side some older homes have been torn down and the new owners have opted to rebuild along the water’s edge and put in long, steep driveways. I know someone who purchased one of these rebuilts and I opted to leave my car at the top of the driveway and walk down when I visited - I drive a manual and I didn't have a enough confidence at that time. There are many locales like these two along the coast.

Up north of Pender Harbour, there is a section of the highway at Ruby Lake that follows a sharp “S” curve and there is one spot there that collapses and continuously needs repairing; as does an significant section of Egmont Road.

Those retreating glaciers that shaped Whidbey Island and Puget Sound also shaped the lower mainland, Fraser Valley and the whole coast line of BC. In my next post, I will take a brief look at the economic impact of the glacial silt left behind and what it could mean to some Sunshine Coast property owners.

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Messages In This Thread
"Slip, sliding away..." - by Skook - 03-29-2013, 11:12 AM
RE: "Slip, sliding away..." - by Skook - 03-31-2013, 10:55 AM
RE: "Slip, sliding away..." - by Skook - 04-01-2013, 06:38 AM
RE: "Slip, sliding away..." - by Skook - 04-02-2013, 12:27 PM
More dirt... - by Skook - 04-18-2013, 01:58 PM

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