responding to tsunami in a marina

[kapnd]

Originally Posted by ninethlife

Excuse my recalcitrant nature, but during the last tsunami in Brookings, Oregon, the Coast Guard was at the breakwater entrance threatening pleasure boaters and making them return to the dock and run for the hills. At the same time they allowed all commercial vessels to head out to deeper water. Why can a know nothing with an automatic weapon choose who survives and who gets tsd?

That’s really ridiculous!
I would have defied the law in that case, absolutely.

[rgranger]

Sail had this article on the subject

https://www.sailmagazine.com/cruisin...-for-a-tsunami

[Tellie]

If the tide is going out really faster than normal, you're too late. If the tide is coming in really faster than normal it's really too late.

[lenseman]

In 2009, a yacht in Samoa was caught by a large Tsunami whilst berthed alongside.


This is his harrowing story (in three parts), part 1 below, (use Google "Learnativity tsunami", to read parts 2 and part3).


Living & Learning Aboard the Good Ship Learnativity: Doing the Tsunami Tango in American Samoa: Part I

[toddster8]

I just discovered that our state has an official brochure!

https://www.oregongeology.org/pubs/t...reMaritime.pdf
And specific guidance for individual ports, although so far they have done only one.

Re: The 2011 tsunami
Lessons learned in northern California from the March 11, 2011 Japanese tsunami
During the March 11, 2011 event, Crescent City boats headed to sea. Once the tsunami hit and they realized they were unable to return to Crescent City harbor, decisions had to be made as to where to go because of a huge storm approaching the coast. Some vessels had enough fuel to make it to Brookings Harbor in Oregon or to Humboldt Bay, California. Some smaller vessels did not have enough fuel and made the choice to re-enter Crescent City harbor to anchor. Some Crescent City captains had never been to Humboldt Bay and some were running single handed as they did not have enough time to round up crewmen. As with the captains who chose to go to Brookings, all of the captains heading to Humboldt Bay kept in close contact with each other for safety and for moral support. Even though the tsunami initially impacted the west coast on the morning of March 11, 2011, the largest surges in Crescent City did not arrive until later in the evening.

[owly]

The three part story of the Tsunami in Samoa was a phenomenally valuable one.... thanks for that!!


It's clear to me that in a local earthquake situation you likely have no chance at all of saving your boat.... unless you are on it, and fully fueled, and able to stand clear easily and quickly into deep water. And then ONLY if you instinctively sense what is going on and respond without hesitation..... extremely unlikely. Being able to save yourself in that situation is not a high probability.


It's also clear that one should always know where the deep water is in relation to where you are docked, slipped, anchored, or moored, so you can process the options more or less instantly.



A slip in a marina is the worst place to be as far as saving your boat... the best as far as being able to flee to high ground. On a mooring or at anchor is probably the best.


As in a hurricane, other boats and flotsam are the greatest danger to your boat, or your personal survival if the water catches up to you.


The idea of the USCG choosing who can stay and who can leave arbitrarily when a distant tsunami is approaching is appalling. The ship captain bears the ultimate responsibility for the safety of the ship, and always has. This is literally a life and death decision. You abide by their authority and they are responsible for the consequences........ You defy their authority and you at least morally absolve them of any responsibility........ The choice as captain is yours, and the consequences on your shoulders ultimately. They are NOT going to shoot you. There may be consequences later....... be prepared to face them.


A shallow bottle neck bay is the worst place to be... the open ocean the best.


I've been blessed in my life by having the ability to go into an "overdrive" mode in emergency situations, where time seems to almost stand still, and I can weigh options and choose the best course at warp speed.... it's almost like an "out of body" experience. This has saved my life numerous times, but it may not always be there for me....I don't know. It clearly is not for some people....... I've seen this again and again.

Would I know what is happening in an earthquake and comprehend the ramifications soon enough to react? I don't know, but what I DO know is that being mentally prepared does make a difference, and a big one........ at least for me. What I've seen in emergencies is that a few people absolutely freeze, a few come into their own, and can take charge and direct others, and the majority do well once given direction. If you are one of the majority.... acknowledge and follow those who are leaders in these situations...historically, that's your best chance. I do know how (and when) to follow and support positive well directed leadership..... and what the difference is between arbitrary authority and good leadership.



H.W.

[toddster8]

Kind of sobering to look at the chart in the brochure I linked above - for a distant tsunami, when you have hours to react, minimum safe depth is just a few miles out. But for a near-field tsunami, when you have about ten minutes, minimum safe depth is about 30 or 50 miles out. (Most places with a big continental shelf, it would be much worse.) If you are caught out in that band somewhere, they’re saying that there is basically nothing you can do but hang on and enjoy one last big ride.
Although the calculation is based on The Big One Cascadia rupture, which might not be happening.

[Paul L]

Originally Posted by toddster8

Kind of sobering to look at the chart in the brochure I linked above - for a distant tsunami, when you have hours to react, minimum safe depth is just a few miles out. But for a near-field tsunami, when you have about ten minutes, minimum safe depth is about 30 or 50 miles out. (Most places with a big continental shelf, it would be much worse.) If you are caught out in that band somewhere, they’re saying that there is basically nothing you can do but hang on and enjoy one last big ride.
Although the calculation is based on The Big One Cascadia rupture, which might not be happening.

It's too bad the brochure contains no justification for needing to move your vessel to 600ft depth. That just sounds way too conservative. Sure there is some possibility you'll get screwed if you stay in closer, but there's a possibility you'll be fine and get hit by a bus when you leave the marina. If you can get to 60ft or more depth you'll probably be fine in the majority of tsunamis.
Of course there's always the exception

World's Tallest Tsunami
A tsunami with a record run-up height of 1720 feet occurred in Lituya Bay, Alaska
On the night of July 9, 1958, an earthquake along the Fairweather Fault in the Alaska Panhandle loosened about 40 million cubic yards (30.6 million cubic meters) of rock high above the northeastern shore of Lituya Bay. This mass of rock plunged from an altitude of approximately 3000 feet (914 meters) down into the waters of Gilbert Inlet (see map below). The impact generated a local tsunami that crashed against the southwest shoreline of Gilbert Inlet. The wave hit with such power that it swept completely over the spur of land that separates Gilbert Inlet from the main body of Lituya Bay. The wave then continued down the entire length of Lituya Bay, over La Chaussee Spit and into the Gulf of Alaska. The force of the wave removed all trees and vegetation from elevations as high as 1720 feet (524 meters) above sea level. Millions of trees were uprooted and swept away by the wave. This is the highest wave that has ever been known.

https://geology.com/records/biggest-tsunami.shtml

[JohnHutchins]

I don't think any general answer can be given to this question. First the warning period you will have can vary dramatically. You might have several hours warning or, in the case of a lituya bay type of event where a local tsunami is generated by a landslide you may have nearly no warning. The topography of the coast will matter. The way in which the coast shoals of course; as that will control how far out you have to get before you no longer have to worry about steep or breaking waves but also the topography of the shore which is going to have an effect on how easy it is to find high ground. It will also have an effect on how high high ground has to be. If you're in a place that looks like lituya bay then high ground may be several hundred feet. The shape of the coastline will also have an effect on how strong the current will be once the surge begins. Also relevant may be the tide height at the expected time the tsunami arrives.

So sensible for me and sensible for you for me are likely to be very different things unless you' happen to be a few sips over in the harbor from me.

[owly]

I think you hit the nail squarely on the head with the last statement.


Computer modeling of each harbor in a tsunami would be invaluable in deciding what one's options are. The very things that make a harbor desirable, could also make it a trap. Crescent City Ca ironically appears to be one of the best harbors to escape from to deep water quickly. You are not in a deep and confined bay, but one does not read about the Tsunami wreaking havoc in Eureka, Brookings, or Coos Bay. The model for Crescent City would be very different from the model for Eureka.... or Tacoma. When the big one they are all preparing for comes, where do you want to have your boat?.... or your body.

It seems to me that a multihull is best suited to survive, and in many cases being aboard under power and clear of the really shallow water may be safer than trying to reach high ground. Being at anchor near the harbor entrance would give you the best chance..... if you are aboard.... the worst if not. It leaves one with a simple choice.... If you are aboard, cut the ground tackle and go..... If you are ashore, head for high ground. If you are near shore or in a marina, it may not be as clear cut, and waffling may kill you. The optimal decision will have to do with the source distance and warning time. Is there an alert system? How well and quickly does it get the word out? How much detail?


H.W.

Originally Posted by JohnHutchins

I don't think any general answer can be given to this question. First the warning period you will have can vary dramatically. You might have several hours warning or, in the case of a lituya bay type of event where a local tsunami is generated by a landslide you may have nearly no warning. The topography of the coast will matter. The way in which the coast shoals of course; as that will control how far out you have to get before you no longer have to worry about steep or breaking waves but also the topography of the shore which is going to have an effect on how easy it is to find high ground. It will also have an effect on how high high ground has to be. If you're in a place that looks like lituya bay then high ground may be several hundred feet. The shape of the coastline will also have an effect on how strong the current will be once the surge begins. Also relevant may be the tide height at the expected time the tsunami arrives.

So sensible for me and sensible for you for me are likely to be very different things unless you' happen to be a few sips over in the harbor from me.

[Lepke]

Never been in a tsunami, but know several fishermen and CG that were. The key is heeding the warning and getting to sea. Even a 100' depth is better than 30'. In deep water it's passing is not noticed. I was in Kodiak before and after the 1964 tsunami. People that left on the first warning had no problems, others found their boats downtown.

I fished out of Crescent City for awhile. Locals told me only 3 buildings survived the 1964 tsunami. Luckily one was a bar.

[Paul L]

Originally Posted by Lepke

Never been in a tsunami, but know several fishermen and CG that were. The key is heeding the warning and getting to sea. Even a 100' depth is better than 30'. In deep water it's passing is not noticed. I was in Kodiak before and after the 1964 tsunami. People that left on the first warning had no problems, others found their boats downtown.

I fished out of Crescent City for awhile. Locals told me only 3 buildings survived the 1964 tsunami. Luckily one was a bar.

Proving once again that God takes care of babies and drunks.