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 Post subject: Fast Moving Tide
PostPosted: Mon Oct 25, 2010 12:19 pm 
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Location: Seattle, WA and more times than not, Camano Is, WA USA
I sail mainly in Port Susan Bay, North of Seattle, WA. When the tide comes in and out, it moves at a fairly slow pace. Even when razor clamming down further South at Ocean Shores, WA, the tide is not noticably fast moving.
Last month when visiting the Broken Group Islands off of Vancouver Island Canada, we experienced Very fast moving tides. The first time we beached our AIs to check out the camp sites, we pulled them up on the shore about 2'. We were gone for no more than 15 minutes and when we returned, were shocked to see our AIs moving out into the water. :o :oops: (Needless to say, the boats were always beached higher, or tied after that experience). When camping at Turret Is., we watched the tide coming in. It moved in very gentle swells, unnoticeable until they would roll up on the beach. These swells had the same rhythm as a human breathing long and deep. After each swell gently broke, the water line had raised on the shore many inches from where it had been before.
I'm curious as to why the tide moves so much faster up that far North than down in Puget Sound. The turn of the Earth? Does anyone have any ideas?

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 Post subject: Re: Fast Moving Tide
PostPosted: Mon Oct 25, 2010 7:40 pm 
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Joined: Tue Aug 18, 2009 2:07 pm
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Location: Saint Johns, Florida
When I started kayaking many years ago in Seattle on of the first things they taught us was to always tie your boat securely to something on shore that doesn't float. Most people put a small cleat on their boats just in front of the cockpit and used it to tie the end of a painter tied to the bow so you always had a line ready to tie your boat.

One day I beached a canoe far enough away from the water that I didn't bother tieing it. A little while later I had to get someone with a small powerboat help me recover my canoe which floated away. This happened at Fort Flagler.

Moral of the story, always tie your boat if you want to make sure it doesn't leave without you.

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 Post subject: Re: Fast Moving Tide
PostPosted: Mon Oct 25, 2010 9:32 pm 
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Location: Kailua 96734
I'm sure I could Google it, but I did notice on a trip to Alaska that they have some of the biggest/fastest tides on the planet. A coastal river 1/2 mile across would go from mud flat to rapids in a matter of hours. Clamming becomes a life or death experiment at times there.

In Hawai'i (lat 20n) we experience gentle tides, usually 3 ft or less. No deadly surge in most places but the surf and the reef that is exposed at low tide makes a BIG difference. :shock:

On our sand bars and beaches, you still need to keep an eye on your yak. Trust me on this.

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 Post subject: Re: Fast Moving Tide
PostPosted: Tue Oct 26, 2010 10:30 pm 
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Location: SOUTH WALES UK
The Bristol Channel has a tidal range of 15 metres (49 ft), second only to Bay of Fundy in Eastern Canada.
Bad news if the tide is against you. Virtually impossible to sail into wind and tide.


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 Post subject: Re: Fast Moving Tide
PostPosted: Sat Nov 06, 2010 11:36 am 
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I read somewhere about the West Coast and the amount of coastline.

Something like:

CA Bays (SF etc) have 500 miles of coast.
Puget sound has 2500 miles,
inside pasage has 25000 miles.

THe point being, there is so much more water ways to get filled and drained.
In the area you are going, sometimes the tides move so much the large rocks on small islands will rumble!

So to answer your question, it is a matter of ebb and flow and quantities being held back.
Also I know that lattitude and tide movement is trumped by local topography. I.e. Lattitude has an impact but the local topography (hydrology) makes more a difference.


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 Post subject: Re: Fast Moving Tide
PostPosted: Sat Nov 06, 2010 5:31 pm 
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Location: CLEARWATER, MN
The moon generates the largest tides on the oceans. Solar tides are about 46% the range of lunar tides. The moon produces tides on both the moon-side of the Earth and on the opposite side (as does the sun). As you might have noticed the moon changes its position at its highest point in the sky over time, because the moon's orbit is not over the Earth's equator but is tilted. So the tides don't get pulled up and down at the equator as much as above and below the equator.
The Earth is also tilted a little more than 23 degrees on its orbit around the sun so the solar tides are also shifted north and south of the equator.
Putting these orbital factors together...the tides can be expected to be highest at latitudes at little more than 40-45 degrees.
Then there also is the effect (as mentioned in the above threads) of large estuary types of bays which force large quantities of seawater to flow in and out.
In addition, there is a phenomenon known as 'resonance'. If you ever tried to push a friend on a swing, you might have noticed that you weren't able to swing her full high on the first push. But if you timed your pushes correctly, you were slowly able to push her higher and higher without having to give her a single giant push. The tides come in and out nearly as timely as a clock. Each bay and estuary has a 'resonance' time depending on width, length, and depth of water. For example, if the resonance time of your bay is the same length of time as the tide on your coast...the tide wave(s) will build up (similar to the girl on the swing) until it reaches a maximum height. This means much more water will have to surge in and out than if the two times are not similar (try pushing the swing out of timing or randomly and the girl will not move up
very much if at all).
So some bays and estuaries have very high tidal ranges and tidal current because of their latitudinal location, shape and depth which amplify the tides.
Some examples are the Bay of Fundy on the North American eastern coast,
the coast of northwestern Europe and northwestern North America.
It may surprise you to know that the largest of the Great Lakes, Lake Superior has little if any tidal action but the much smaller Lake Erie has a significant tidal range, because the size, shape and depth of Lake Erie, which allows a much greater tidal resonance than the larger but much deeper Lake Superior.


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 Post subject: Re: Fast Moving Tide
PostPosted: Sat Nov 06, 2010 7:46 pm 
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Location: Kailua 96734
Great explanation. And who better to give it? :lol:

And there is the fastest and most dangerous "tidal wave" (not really) the Tsunami.

We had a great chance to view one this year following the Chile earthquake that did so much damage.

It was mostly a made for TV, grab the popcorn moment. Surges of up to 3 feet sucked water in and out of our bays every 10-15 minutes for a couple hours. No damage, but very instructive.

[youtube]http://www.youtube.com/watch?v=lYQjMHSq3rw&NR=1[/youtube]

Specially if you never seen water running UP a mountain stream.

[youtube]http://www.youtube.com/watch?v=_-PwY9elaqg[/youtube]

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 Post subject: Re: Fast Moving Tide
PostPosted: Sat Nov 06, 2010 11:23 pm 
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Joined: Wed Mar 17, 2010 5:00 pm
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Location: Port Macquarie, Australia
Just amazing, that was only a water height diff of one metre!

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 Post subject: Re: Fast Moving Tide
PostPosted: Sun Nov 07, 2010 3:46 am 
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Location: Point Lookout, Maryland
Here's a global tide map that I stumbled across awhile back:

Image

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 Post subject: Re: Fast Moving Tide
PostPosted: Mon Nov 08, 2010 3:40 pm 
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Location: Port Macquarie, Australia
Quote:
Derby has Australia’s highest tides and one of the highest in the world.

The Bay of Fundy, Nova Scotia, Canada, has 15m tides. Other high tides occur at Bristol (UK) 14.6m, Mont Saint Michel (France) 12.3m, Puerto Gallegos (Argentina) 13.2m and Bhaunagan (India) 12.2m.

High tides in Western Australia are Derby 11.8m, Yampi Sound 10.9m, Broome 9.8m and Wyndham 8.4m.

ref: www.derbytourism.com.au
There's some interesting info, pics and map of the Derby tides at ABC : King of all Tides.

Image Image
:oops: The ABC claims in that article that Derby has the second highest tide in the world - which is of course incorrect.


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 Post subject: Re: Fast Moving Tide
PostPosted: Tue Nov 23, 2010 5:58 pm 
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Location: Seattle, WA and more times than not, Camano Is, WA USA
Great information. Ger, I got a bit of a geography lesson from you. Never heard of Bay of Fundy before. There were some interesting reads on the web. Here's one which has a lot of the info Tidlewave posted on why the high tides, and then a bit more:

Eastern Canada's Bay of Fundy is located off the Atlantic coast of North America. The Fundy Bay borders Nova Scotia on one side and New Brunswick and the tip of Maine on the other.
Natural forces have converged to make the Bay of Fundy subject to significant tidal ranges, earning the Bay the designation of being home to the world's highest tides. What contributes to the Fundy phenomenon?
Tidal action is influenced by planetary gravitational pull. The sun and moon engage in a tug of war that causes oceanic waters to move back and forth. What happens when these waters converge with the Fundy tides?
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Fundy's Shape Contributes to High Tides--The Bay of Fundy is a narrow 170-mile long V-shaped channel. This shape causes the waters to double up as they travel up the Bay.
Bay Bottom Influences Fundy Tidal Heights--The Fundy bottom slopes upward like a funnel, from its mouth to its head, which forces incoming water to rise. The tide is 11 feet along Nova Scotia's southwest shore. As it makes its way up the Bay, it increases in height up to 53 feet in the Minas Basin.
Resonance and High Tides--By the time this cycle is completed some thirteen hours later, the moon then exerts its pull, which magnifies the tidal ranges. In a particular coincidence of timing, the Fundy tidal cycle (rhythmic oscillation) coincides with incoming oceanic tidal waters. This induces a second oscillation, thus the Bay is like a tub of water that is rocked back and forth. This resonance, termed a seiche, produces higher tidal ranges.
Read on
Experiencing the Bay of Fundy Tidal Bores
Exploring Historic Parrsboro, Nova Scotia
The Not Since Moses Race at Five Islands, NS
Bay of Fundy Tides: How Mighty?
Twice daily over 100 billion tons of water move in and out of the Bay of Fundy.
Fundy waters are equivalent to or greater than all the world's freshwater rivers.
The sheer weight of the water flowing into the Minas Basin actually causes Nova Scotia to tilt, bending under the immense pressure.
Fundy Tidal Action
Each phase of the tidal cycle takes 6 hours, 13 minutes with an average tidal range of 45.5 feet.
Tide times move ahead about one hour each day.
The highest tidal range was recorded as 54.6 feet.
Fundy Tides and the Phases of the Moon
Spring Tides--occur during new or full moons, when earth, sun and moon are aligned. Spring tides are greater.
Neap Tides--take place twice each month when sun and moon oppose each other and are at right angles to earth. Neap tides are slighter.
Perigean Tides--when the moon is closest to earth, tides are even higher.
It is believed that some 200 factors combine to create the mighty Bay of Fundy tides, earning the Fundy Bay the designation of being one of the natural wonders of the world.

I guess when it comes to having "some 200 factors combined to create the mighty tides of Fundy", which I'm supposing is the same for the other many areas around the globe, which have very high tides, (Great chart Whosyerbob) there isn't a cut and dried answer to the question of what causes the fast moving tides. But knowing all the combinations is quite interesting.
Thanks :P
NOHUHU, were there worries this tidlewave would be higher, or was it local knowledge it would get to be only 3'?

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PostPosted: Tue Nov 23, 2010 8:42 pm 
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Location: CLEARWATER, MN
The word 'Tidalwave' is a misnomer... Early 'oceanographers' (sailors) knew about wind generated waves and lunar-generated waves (tides). But when seemingly random large waves hit a coast they had no real explanation for them. The period of wind waves doesn't extend more than seconds, the period of tides waves lasts on the order of hours...but the 'random' waves have periods of minutes. They also can come from areas where there were no obvious storms and didn't approach from directions expected by the gravity of the moon. They also exhibited shoreline breaking more similar to incoming lunar tidal waves (bores) than wind waves. So they also were called 'tidalwaves'.

Today...to help distinguish what oceanographers are talking about...incoming lunar tidal waves are generally called 'bores' (some oceanographers still prefer to call lunar tidal-waves: tide waves...but not tidalwaves). Fluctations in smaller bodies of water which are sloshed back and forth by wind or tides are usually called 'seiches'. The so-called 'tidalwaves' were finally determined to be caused by ocean-floor earthquakes, underwater landslides, and/or underwater explosions. To correct the mistaken term, these waves were finally called 'tsunamis'.
Japan has experienced many of these tsunamis because there are both active earthquake zones and underwater volcanoes which send large waves unto the Japanese coasts. 'Tsunami' roughly translates into 'large wave in harbor'.
Many oceanographers have tried to get rid of the term 'tsunami' because they feel that a more scientific term should be used, that is not derived from a single language. They have tried to use the term 'seismic sea wave' as a 'better' generic title. But after almost succeeding in getting rid of the term 'tidalwave', the word tsunami seems to have stuck.
After more than 30 years of teaching oceanography, I find that most new science students are using 'tsunami' rather than 'tidalwave'. However I find a lot of television 'reporters' still use the word tidalwave.
You might note my user name 'signature'...I use it in the same manner that Darwin might have nicknamed himself 'a monkey's uncle'. LOL


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 Post subject: Re: Fast Moving Tide
PostPosted: Wed Nov 24, 2010 12:10 am 
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Joined: Tue May 18, 2010 2:31 pm
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Location: Kailua 96734
Lion, our tsunami, generated in Chile was a more predictable event than usual and it served as a great shakedown of the new Pacific wide warning system.

The scientists were able to accurately predict the time of arrival of the waves, but did not know how large they might become, so the entire state was put on notice and the beaches, including Waikiki were closed and evacuated below a few floors.

We all climbed to our lookouts or watched on TV as the whole thing unfolded.

The state was lucky. We dodged a bullet this time, and got to watch it pass in slow motion, w/instant replay. Very cool experience.

And it was a valuable reminder.

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 Post subject: Re: Fast Moving Tide
PostPosted: Wed Nov 24, 2010 4:25 pm 
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Joined: Wed Jul 22, 2009 5:51 am
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Location: Hervey Bay Qld Australia ( formally UK)
Ger wrote:
The Bristol Channel has a tidal range of 15 metres (49 ft), second only to Bay of Fundy in Eastern Canada.
Bad news if the tide is against you. Virtually impossible to sail into wind and tide.



I fish in the North Sea Aldeburgh in-between sand banks, you can sail against the tide with enough wind but not peddle, we have 3m tides, but its the current strength that does you, its like being in a river...........

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