Okanagan Lake tsunami risk?

Okanagan Lake tsunami risk?

Postby Frisk » Mar 11th, 2015, 7:04 pm

I read an article on lake tsunamis and I was kinda surprised by what I read. Give it a read and let me know what you think. With some of the steep slopes around the lake, could a rock slide potentially cause a tsunami?

http://www.vancouversun.com/news/Lake+tsunamis+pose+threat+waterfront+homes+campgrounds+beaches/10794418/story.html
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Re: Okanagan Lake tsunami risk?

Postby jamapple » Mar 11th, 2015, 7:08 pm

Never thought of that!! I wonder if there is an insurance policy you can get for this? If there is, I would speculate these concerns are real, and being addressed.
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Re: Okanagan Lake tsunami risk?

Postby GordonH » Mar 11th, 2015, 7:21 pm

Here is map showing the fault lines in BC: http://geocommons.com/maps/88369


If a quake was to hit in Kelowna on or near Okanagan Lake, depending on its size those tall buildings that reside on former swamp land. Maybe a bad place to be, just saying. Chances of that happen small to nil.
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Re: Okanagan Lake tsunami risk?

Postby Joe Public » Mar 11th, 2015, 7:25 pm

From Wiki...

The Vajont Dam is a disused dam, completed in 1959 in the valley of the Vajont River under Monte Toc, 100 km north of Venice, Italy. On 9 October 1963, a massive landslide caused a tsunami in the lake, the overtopping of the dam, and around 2,000 deaths. This event occurred when the designers ignored the geological instability of Monte Toc on the southern side of the basin. Warning signs and negative appraisals during the early stages of filling were disregarded, and the attempt to safely control the landslide into the lake created a 250 metre (820 ft)[1] megatsunami (ten times higher than predicted) that brought massive flooding and destruction to the Piave valley below, wiping out several villages completely.
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Re: Okanagan Lake tsunami risk?

Postby I am Canadian » Mar 11th, 2015, 7:26 pm

lol, I'm not concerned at all. Penticton & Vernon are pretty flat so if there's a rockslide it would travel from East to West or West to East (short distance) and we don't really have any hills made out of gravel so..., no.
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Re: Okanagan Lake tsunami risk?

Postby GordonH » Mar 11th, 2015, 7:45 pm

Joe Public wrote:From Wiki...

The Vajont Dam is a disused dam, completed in 1959 in the valley of the Vajont River under Monte Toc, 100 km north of Venice, Italy. On 9 October 1963, a massive landslide caused a tsunami in the lake, the overtopping of the dam, and around 2,000 deaths. This event occurred when the designers ignored the geological instability of Monte Toc on the southern side of the basin. Warning signs and negative appraisals during the early stages of filling were disregarded, and the attempt to safely control the landslide into the lake created a 250 metre (820 ft)[1] megatsunami (ten times higher than predicted) that brought massive flooding and destruction to the Piave valley below, wiping out several villages completely.


Looking at the area above this dam. Very steep slops down to man made lake (because of the Dam). Nothing like that around Okanagan Lake.
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Re: Okanagan Lake tsunami risk?

Postby Zoso » Mar 11th, 2015, 8:01 pm

Seems highly unlikely . Suppose there was a landslide . I cannot think of an area around the lake that would create one . The perimeter is pretty well built on the entire lake shore . The lake has several under water features that would deflect and disapate a tsunami . A dam is usually chosen in a steep valley that has a sharp and deep angle of repose. Not to mention on a dam basically a toilet flush effect is created when a giant wave would reach a focused worlds biggest drop slide that would speed that water to practically terminal velocity , impacting the bottom with a tremendous compounding of static pressure . Obliterating a narrow valley with no escape or allowance for dissipation .
For the Okanagan the effect would be very limited . Imo.
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Re: Okanagan Lake tsunami risk?

Postby GordonH » Mar 11th, 2015, 8:11 pm

Zoso wrote:Seems highly unlikely . Suppose there was a landslide . I cannot think of an area around the lake that would create one . The perimeter is pretty well built on the entire lake shore . The lake has several under water features that would deflect and disapate a tsunami . A dam is usually chosen in a steep valley that has a sharp and deep angle of repose. Not to mention on a dam basically a toilet flush effect is created when a giant wave would reach a focused worlds biggest drop slide that would speed that water to practically terminal velocity , impacting the bottom with a tremendous compounding of static pressure . Obliterating a narrow valley with no escape or allowance for dissipation .
For the Okanagan the effect would be very limited . Imo.


I would agree.
A quake would be a much more dangerous, highly unlikely to create any type of tsunami on Okanagan lake. Different story on sandy to reclaimed swamp land around lake edges & inland (strong enough quake even for a few seconds can cause both sandy & reclaim swamp land into quick sand very fast).

Like I said in earlier post chance are slim to nil of that happening.
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Re: Okanagan Lake tsunami risk?

Postby Swoop » Mar 11th, 2015, 9:49 pm

..I'm by no means trying nor intending to be an alarmist, as i too think the likelihood of the OP questions is fairly minimal - although certainly possible...remember these couple of recent incidents?...this valley is made up of a number of different rock types - some very solid and stable, others quite fractured and fragile...

http://gallery.castanet.net/albums/2008 ... dFracture/

http://www.castanet.net/news/Kelowna/10 ... nagan-Lake

...not exactly cataclysmic disasters that threatened the valley, but large slides are always possibility in any mountainous terrain...

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Re: Okanagan Lake tsunami risk?

Postby Drip_Torch » Mar 11th, 2015, 10:09 pm

Yeah, it's happened before...

July 20, 1951
(Tsunami).
Source: The Penticton Herald, July 26, 1951; Evans 1986 (pp. 164-166); Evans, unpublished data.
Details: On July 20 at 6:45 p.m., a landslide caused a wave in Okanagan Lake near Penticton. The slide in glaciolacustrine silt destroyed a house. An immense wall of water rapidly bore down on the house. The water receded as quickly as it had come. A baby was rescued from the ruins of the house. Fifteen boats were also lost (Evans and Clague 1999). A family of four narrowly escaped the tons of clay that slid into the lake. A woman was wedged beneath a chaise lounge on the veranda, which railing had kept her from being swept away. Water had entirely filled the house, slightly south of the Three-Mile Beach on the east side of Okanagan Lake, when the wave crashed over it. An insurance adjuster found silt imbedded on top of a shelf of a floor to ceiling cupboard. Also dead fish were found on the roof.

One acre (0.4 ha) of orchard with 33 fruit-bearing trees was gouched out of the cliff. With a “terrific rumbling” a solid wall of water hit the cottage. A concrete 9-in. (22.5 cm) wall cracked “as though it had been a piece of 2 x 4.” The thousands of tons of earth engulfed the lakeside home at Three Mile point and created a 12-ft. (3.6 m) wave. The wave devastated the shore for over 0.5 mi. (800 m). A car was hurled 200 ft. (60 m) onto the beach. The 2-ton sailboat Marion was bodily lifted and deposited high and dry 100 ft. (30 m) from where she had been moored. A cabin cruiser, moored short an unable to ride the crest, was submerged. A four-cylinder marine engine was found 50 ft. (15 m) from its stand.


http://www.env.gov.bc.ca/wsd/public_saf ... south2.pdf


Aerial-photo-of-landslide-south-of-Three-Mile-Point,-1953---Penticton-Archives--Photographer-unknown.jpg
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Re: Okanagan Lake tsunami risk?

Postby Zoso » Mar 11th, 2015, 10:25 pm

Some such as that can be created by heavy rain season or farming irrigation . The semi arid valley isn't really at risk except when the weather or man presents and abundance of water . Like the slides at the coast and the big slide North of kazlo . It's kind of like waiting for the big meteor to hit . And it's not really feasable to have the province look for trouble spots throughout .
Great pic though !
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Re: Okanagan Lake tsunami risk?

Postby Catri » Mar 11th, 2015, 10:40 pm

Interesting, you can still see where the hillside deposited itself in the lake on google satellite view:
https://www.google.ca/maps/place/Three+ ... 930c15ccbc

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Re: Okanagan Lake tsunami risk?

Postby Zoso » Mar 12th, 2015, 7:52 am

Actually one place I can think of the bares a resemblance to that is the bluffs across from Stuart park Kelowna . That has yet to let go . I was over there years ago and had an uneasy feeling about it . Let's hope we don't get record breaking rains .
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Re: Okanagan Lake tsunami risk?

Postby mexi cali » Mar 12th, 2015, 8:31 am

Slim maybe but I'm glad I live on a hill.
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Re: Okanagan Lake tsunami risk?

Postby Joe Public » Mar 12th, 2015, 8:46 am

If you recall a few years ago, when they were 4 laning Rte 97 between Summerland and Peachland, the rock above the highway separated and shifted, forcing construction to temporarily shut down, most likely due to the massive amount of blasting involved in highway construction. This is a very large, and very high rock face, and the fact that a lateral seam has been blasted from one end to the other would obviously weaken it.

There is more than ample material available to create a massive lake tsunami, and while I don't think that the highway blasting could have dislodged it, I do believe that the highway blasting may have fractured a good portion of it, and that a medium tremor in the future could be the trigger to send the entire hillside down. No one has to travel far to see the Hope slide, and the magnitude of destruction possible.

More interesting is the fact that the BC Liberals privatized the entire geotechnical section of the Ministry of Transportation, and there is no one currently watching the stability of the area. If everyone will recall, the BC Liberals basically eliminated dam inspectors in BC, with results being the dam break in Oliver and the Mount Polly disaster.

My opinion is that it's not a matter of if, but when.
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