https://www.alaskasnewssource.com/2...-has-potential-to-create-destructive-tsunami/
Ya'll need to stay home..Ill let ya know how the shrimping is this spring
Ya'll need to stay home..Ill let ya know how the shrimping is this spring
Barry Arm
- Thread starter Nunya
- Start date
I've ridden some 7-8' waves in the boat before but my skill levels are not up to a tsunami level yet.
Good thing they started to monitor the initial albeit slow slide. Hopefully they can get us a better hydraulic survey that will tell us what could happen when either of these events happen. Knowing the areas of most concern should help all of us who use the area make informed decisions. Seems like Valdez would have little effect, but I'm not a hydrologist.
iofthetaiga
Well-known member
I doubt the tsunami impact modeling is likely to change significantly from the assessment they did in May. The only real questions are if it kicks off, and when... Last I read the movement had slowed later in the summer, but then it moved another 8" last month, so... Personally, I'm staying out of the western side of PWS; you guys can have it!
Better just stay home potential slides could be anywhere:
https://mustreadalaska.com/massive-...red-as-earthquake-in-juneau-on-christmas-eve/
https://mustreadalaska.com/massive-...red-as-earthquake-in-juneau-on-christmas-eve/
Double down on Barry Arm.
https://www.alaskasnewssource.com/2...-has-potential-to-create-destructive-tsunami/
https://www.alaskasnewssource.com/2...-has-potential-to-create-destructive-tsunami/
It wasn't what was above the water that wiped out Chegna and Valdez. It was the underwater slides that created the tsunamis that did the damage. I don't think they can predict what is going to happen over there with any degree of certainty. It would be nice to see this on camera if it happens.
iofthetaiga
Well-known member
Everything within this obvious scarp in the center of the image is at risk of going. The current focus seems to be on the very large mass occupying the right half of the scarp, from which the toe of the glacier is presently receding. This is the moving mass they have instrumented (and I think they're watching all this now with satellite radar, too). I'm not sure if they also have instruments on the section I have demarcated with the red dashed line, but I've got money says this chunk has potential to make a big splash soon. All we need is the right freeze thaw cycle and/or a good rain event (or a little earthquake) to kick it off. The second one they're talking about in the afore referenced article is a little farther to the right, just out of this screen shot frame.
iofthetaiga
Well-known member
Hmmm.....I wonder is a 30' tsunami into Whittier will be sufficient to squirt water and debris out the west end of the tunnel?:shocked:
I wondered the same thing when this first came up, the tunnel entrance on the Portage side looks to be about 175'-200' above seal level.
I was hoping they would have more information for outside of Wells Passage. If a guy rolls the dice for a few hours transit time that's a better option than spending days and days worrying about a 30' wave at anytime which is what the report you linked to shows in the immediate area.
iofthetaiga
Well-known member
I think it's a little under a hundred feet (my topo map puts it just below the 100' contour line)...but obviously it's not really a critical point. The real point worth noting is that the 1964 quake caused tsunami that hit Whittier was about 25', and the inundation/damage from that event is documented so no need to speculate. They're predicting a wave of up to 30' could roll into Whittier as a result from this slide displacement...
I'm sure you understand it, but I don't think the majority of folks realize the implications. When they hear "30 foot wave" I think maybe they envision 30 foot deep inundation as the result...but when a 30' wave rolls into a narrow fjord like this and piles up against the back end it's a pretty dramatic and violent event.
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iofthetaiga
Well-known member
Obviously, modeling that would be really complex, with lots of variables, including the state of the tide at the moment...I'm sure some nerd is working on it...but the fact that they did predict even Valdez would likely see a surge causing strong currents through the port is telling.
A couple interesting reads:
https://earthquake.alaska.edu/sites/..._PEM_FINAL.pdf
https://dggs.alaska.gov/webpubs/dggs/ri/text/ri2011_007.pdf
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Iof, thanks for those links.
I found a paper with the information I was looking for https://agupubs.onlinelibrary.wiley....9/2020GL089800 hopefully this image shows up. This is for the original landslide & tsunami discussed and not the recently announced landslide & tsunami.
The paper says:
Whittier would be severely impacted by this event, with tsunami wave height in excess of 10 m arriving about 20 minutes after the slide. The tsunami wave height from this landslide scenario is similar to what was observed in Whittier during the 1964 earthquake and tsunami (Kachadoorian, 1965); however, the modeled wave period is much longer, potentially leading to more extensive inundation. Outside of Wells Passage (Figure 5), the tsunami inundation hazard is limited to a few meters above the tide, primarily at the heads of bays—presenting a hazard to campers on beaches. However, strong currents are likely throughout the Sound, and in particular at geographically constricted water channels. For example, currents near Cordova are in excess of 2 m/s, which is above the threshold for damage in marinas and harbors (Lynett et al., 2014). In areas closer to the slide, inside of Wells Passage and including Whittier, the tsunami risk could be so substantial that field monitoring and preparedness actions are necessary in order to mitigate the potentially devastating impacts of a Barry Arm landslide tsunami.
I found a paper with the information I was looking for https://agupubs.onlinelibrary.wiley....9/2020GL089800 hopefully this image shows up. This is for the original landslide & tsunami discussed and not the recently announced landslide & tsunami.
The paper says:
Whittier would be severely impacted by this event, with tsunami wave height in excess of 10 m arriving about 20 minutes after the slide. The tsunami wave height from this landslide scenario is similar to what was observed in Whittier during the 1964 earthquake and tsunami (Kachadoorian, 1965); however, the modeled wave period is much longer, potentially leading to more extensive inundation. Outside of Wells Passage (Figure 5), the tsunami inundation hazard is limited to a few meters above the tide, primarily at the heads of bays—presenting a hazard to campers on beaches. However, strong currents are likely throughout the Sound, and in particular at geographically constricted water channels. For example, currents near Cordova are in excess of 2 m/s, which is above the threshold for damage in marinas and harbors (Lynett et al., 2014). In areas closer to the slide, inside of Wells Passage and including Whittier, the tsunami risk could be so substantial that field monitoring and preparedness actions are necessary in order to mitigate the potentially devastating impacts of a Barry Arm landslide tsunami.
iofthetaiga
Well-known member
Nice!
Looks like Whittier gets hit with about 4 good waves...
Looks like Whittier gets hit with about 4 good waves...
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Michael Strahan
webmaster
I built a page on the site, concerning this issue earlier in the year. Have a look and let me know if anything needs to be adjusted. It's a very serious issue. Here's the link: https://alaskaoutdoorssupersite.com/barry-arm-tsunami-warning
iofthetaiga
Well-known member
Hi Mike. Looks like maybe DGGS has changed the URL you've linked to on that page. They don't seem to work anymore(?). This thing will undoubtedly continue to be something of a moving target (pun) as it evolves.
Some really good info in this thread. I especially appreciate Patsfan54's last two links which really help demonstrate in tangible terms the magnitude of the danger this presents.
Yep and the first one crests at about 30' followed by a trough just under 30'...roughly sixty feet of water moving in and out of Whittier in about 10-15 minutes, then a couple more 15' crests and 15' troughs over the next hour. If this event were to happen as projected here all of Western PWS will be virtually unnavigable by small craft for quite some time.
Bushwhack Jack
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I'm wondering if they should just pull the band-aid so to speak. In other words, if we are only prolonging the inevitable, wouldn't it be advantageous to plan an intentional collapse of the slide area by using dynamite/explosives etc. Before you all scream out that I am stupid, answer me this, wouldn't be better for this to happen knowingly when people could evacuated safely and perhaps the city of Whittier can build sea walls or some other type of mitigation strategy and just get it done and over with. Just food for thought.
