High Tides

[Since1982]

Kirbstone and I were discussing high tides in Ireland and I thought of the place with the highest tides in the world. I thought more than just one member might be interested so here it is:

The Florida Keys are nothing like Kirbstones.. A high rise and fall here in the Florida Keys is 4 feet. The average is more like 3 feet. There are a lot of high rise and fall tides in the North Atlantic on both sides of the pond. There's a town in Massachusetts with a 25 foot rise. They have special rigs for tying boats to the dock so the rope doesn't sink anything and long tall (Sally, Oops) ladders to climb in and out of your boat on high tide. I think the town's name is Darby. Long Tall Sally is a song from the 50's by a black star named "Little Richard"..

The highest tide rise on the Planet is in Canada at the Bay of Fundy with tide rise and fall of over 50 feet.

In Atlantic Canada’s Bay of Fundy you'll be at the home to the highest tides in the world, the Bay of Fundy is a 170 mile long ocean bay that stretches between the provinces of New Brunswick and Nova Scotia on Canada's east coast.

Each day 100 billion tons of seawater flows in and out of the Bay of Fundy during one tide cycle which is more than the combined flow of the world’s freshwater rivers. And THAT is a bunch of water.

[crfriend]

The Florida Keys [tides] are nothing like Kirbstones.. A high rise and fall here in the Florida Keys is 4 feet. The average is more like 3 feet.

It's worth mentioning that tidal rages are highly dependent on the geography around the entrance of the harbour or where the tide is being measured. Now, I'm not familiar with anyplace in Massachusetts with a 25-foot swing, but where I sail out of in the summer (Boston Inner Harbor) the range for astronomical tides is about 13 1/2 feet with a minimum swing (in between astronomical tides) of about 7. Boston's Inner Harbor is, generally speaking, somewhat funnel-shaped with the wide end at the south-east and the narrow bit at the north-west where we moor -- out at Boston Light, which is outside the harbour, the astronomical swing is about 9 1/2 and the intermediary is about 5 3/4 feet. The "funnel shape" of the harbour piles the water up and magnifies the effect.

This is seen spectacularly in the Saint John area in New Brunswick, Canada which lies at the narrow (and, save for a river, closed) end of the Bay of Fundy which, like Boston's little feature is roughly funnel-shaped as well and because of its size really causes the tides to pile up creating the monster swings seen there which, as Since1982 pointed up can top fifty feet (and can reverse the flow of the river that runs through Saint John).

Atmospheric effects also play a role in the height of tides, especially that of wind. Couple an astronomical high tide with a very strong continuous on-shore wind (think cyclonic storms, e.g. hurricanes) and you're set for real trouble down at the waterfront and some some distance inland. In New England, we get what are called "Nor'easters" in winter which are large low-pressure regions that stall (stop moving) just out into the North Atlantic and generate cyclone-like effects that can really batter our shoreline with water and bury the inland in snow. Unlike hurricanes which move through quite rapidly, these things can hang around for days on end. The motion picture (and book) The Perfect Storm recounts an example of an extreme one.

Each day 100 billion tons of seawater flows in and out of the Bay of Fundy during one tide cycle which is more than the combined flow of the world’s freshwater rivers. And THAT is a bunch of water.

An interesting sidelight on this is that for all that water in motion, nobody has come up with a practical means for harnessing all that energy.

[JRMILLER]

Lake Erie is one of the shallowest of the "great lakes". I have personally sailed much of it and have never had a depth reading beyond 60'. The lake runs SW to NE and when the wind blows really hard out of the SW, we experience a "tide", sometimes as much as 12". The reason is that the water piles up on the NE end of the lake and is unable to return quickly enough to keep the level stable. It's called a "seiche".

It can be very revealing, you see things you haven't seen for some time when it happens -- mud flats, old tires, the bones of Jimmy Hoffa, etc.

[Kirbstone]

Fascinating information. I can only qoute tidal ranges on this side of the Pond. Skip confirms that 'his' tides are gentle, like those in the Windward Islands in the Caribbean and on Barbados.
Funnel-shaped coastlines produce very large tidal ranges, e.g. in the Bristol Channel, affecting the Avon river at Bristol (<48 feet), the Wye at Chepstow and famously the Severn at Gloucester, where at springs the famous Severn Bore can be seen as a very steep slope of water charging upriver at running pace up to 8 feet high.
The gulf of St Malo in Brittany, N. France has great ranges, giving the Channel Islands 40 foot tides and making it economical for the French to dam an estuary there, trapping water until they want serious power in Paris, when they allow the water to hit the turbines. This is using the height difference due to the tides. Much more exciting is a new project being built now in the Orkneys, N. of Scotland, where at the famous Scapa Flow they are about to sink a row of turbines into the FLOW there, thus harnessing the speed of the currents for the very first time. This is part of the Scottish Parliament's decision to vastly increase the percentage energy supply from renewables, e.g. wind and tidal flows.

[crfriend]

Funnel-shaped coastlines produce very large tidal ranges, e.g. in the Bristol Channel, affecting the Avon river at Bristol (<48 feet), the Wye at Chepstow and famously the Severn at Gloucester, where at springs the famous Severn Bore can be seen as a very steep slope of water charging upriver at running pace up to 8 feet high.

I wonder if there's a you-tube video of that spot in action. It sounds rather intriguing -- and dangerous if one does not know where the "safe zone" is. (I've seen the reversing river in Saint John.)

The gulf of St Malo in Brittany, N. France has great ranges, giving the Channel Islands 40 foot tides and making it economical for the French to dam an estuary there, trapping water until they want serious power in Paris, when they allow the water to hit the turbines.

I was aware of that particular project, but had been given the impression that it did not live up to expectations and was, financially at least, a bit of a white elephant.

Much more exciting is a new project being built now in the Orkneys, N. of Scotland, where at the famous Scapa Flow they are about to sink a row of turbines into the FLOW there, thus harnessing the speed of the currents for the very first time.

I think I need to look that one up, but it sounds like the turbines in question with either be submersibles and moored with high-tension cabling or rigidly attached to the sea-floor in much the way that wind-turbines (the "fashionable" term for windmills) attached to the ground.

Given the mass of water versus the mass of air, a much smaller driven surface should be workable for submerged "watermills" than their atmospheric counterparts. That's interesting stuff indeed -- thanks for sharing that Kirbstone!

[Big and Bashful]

Kirbstones stolen my thunder, yes the tides around the Channel islands are spectacular. On a Royalist trip, we visited Jersey. When we tied up we had to brace the yards round to stop them hitting the quayside. After an evening sampling the pubs, we were able to just step back onto the ship. Here on the Clyde estuary the tides are not much more than 13 feet or so, depending on time of year and the weather.

I am looking forward to visiting the Corryvreckan, one of the West coast tidal rips. If you get the weather right you can sail through and anchor close to the tidal race. It is apparently a nice bay with a good view of the currents. Get it wrong and you are swept west about 8 miles, or swamped. Quite entertaining!

[Kirbstone]

I was remarking to Skip earlier that on Sat. Feb 12th we had a (neap) tide in Dublin of 1.6 meters, or about 5'3", whereas on Sat. 19th, (Springs) we had 4.6 meters or about 15'3"...an extra ten feet. That affects our outings through the city to the docks and back in our rowing eight.
I wasn't there this time, I was accompanying my Spouse across the Irish Pond to Fishguard in her Campervan, to stay with an old friend overlooking both Severn Bridges. It wasn't worth visiting the Bore Inn, a few miles South of Gloucester City, best vantage point, as it would have been dark.
A few family visits, and a flight back from Exeter this morning. Hectic week end! (The wife is over there for the whole half-term week entertaining grandchildren.)
One fine June late afternoon we sailed into the West Bay of Sark (Channel Is.) at high tide, two yachts together. Anchored near each other and dinghied ashore. We then followed the steep stepped path up 275 feet to the top of the cliff and along to a hotel for a meal, emerging at midnight, when we descended the precipitous path down again to our dinghies, all well illuminated by the lights of St Peterport on Guernsey a few miles only to Westward. The water had dropped a good 40 feet and fortunately we had made provision for this and found both our dinghies way down at the bottom of a vertical ladder, which we had to descend to reach them. Going across the bay to our yachts there were 25 foot high rocks to our left that we had sailed right over the top of to reach our anchorage!!!
I agree, the French threw a lot of silly money at that St.Malo tidal dam project just for the prestige.

While visiting some German Baltic ports (Laboe & Heiligenhafen) I asked those who knew about such things why in the absence of tides there, there were high-ish sea walls protecting te sea fronts of the towns, and exactly the same answer came back as JRM. said about Lake Erie...The severe Easterlies blowing across from Russia in the Winter/early Spring pile the water up against the German Baltic sea walls every year.

[Big and Bashful]

Sark was my first experience of the mammoth channel tides, on Royalist again, the same trip but a day earlier. We moored in a bay on the South side (I think) of Sark. There was a small island to our left. Anyway, the first thing we did was help out a yacht who's crew were ashore, their dinghy was tied to a ladder and was then underwater. that proved amusing.
I was on watch from midnight till four in the morning, on the radar things were growing around us, once the day started getting lighter we could see rocks all around, probably the same rocks you mentioned. We had the pleasure of watching a yacht sail through the gap between the small island and Sark, on an amazing standing wave caused by the tide rushing through the gap.
Once we left there, we sailed in high winds to Jersey, the stopover I mentioned earlier.
Quite an education, that week.

[Kirbstone]

Postscript to Sark: We left our anchorage at 4 am the following morning in order to have the tidal stream going with us as we passed Northwards between Alderney and Cap de la Hargue at the NW end of the Cherbourg peninsula. We also passed through a very narrow defile between Sark and a little neighbouring islet near Hurm Island on the way. It was slack water, so no dramas.
Reaching along at 7Kn. with a further 7Kn of tide under us was a bit like passing the big atomic station chimney on the headland by cross channel ferry ! (groundspeed about 16mph. for landlubbers) Sailing those waters on STS Royalist must have been serious fun.

[Kirbstone]

Returning to the subject of generating power from the sea tides, if one googles 'Marine Current Turbines' all the info that's currently available is there for the viewing.
Starting with the powergen pilot turbine in the Strangford Lough narrows in N.Ireland, the site visits the Isselmere dam in the Netherlands and also has a graphic put out by the Florida clean marine energy project &c.&c.

[crfriend]

Returning to the subject of generating power from the sea tides, if one googles 'Marine Current Turbines' all the info that's currently available is there for the viewing.

Interesting reading, that: thanks! It turns out that they are "watermills" that have the bases rigidly attached to the seabed and dual rotors to harness the flow (and maintain a balance to keep torque forces even).

[Stevie D]

I wonder if there's a you-tube video of that spot in action. It sounds rather intriguing -- and dangerous if one does not know where the "safe zone" is. (I've seen the reversing river in Saint John.)

Yer tiz....
http://www.youtube.com/watch?v=IKA39LQOIck

And another one taken from a paramotor aircraft
http://www.youtube.com/watch?v=rUuUlSKCecY

[Big and Bashful]

Postscript to Sark: We left our anchorage at 4 am the following morning in order to have the tidal stream going with us as we passed Northwards between Alderney and Cap de la Hargue at the NW end of the Cherbourg peninsula. We also passed through a very narrow defile between Sark and a little neighbouring islet near Hurm Island on the way. It was slack water, so no dramas.
Reaching along at 7Kn. with a further 7Kn of tide under us was a bit like passing the big atomic station chimney on the headland by cross channel ferry ! (groundspeed about 16mph. for landlubbers) Sailing those waters on STS Royalist must have been serious fun.

The sail from Sark was memorable, blowing a gale, the ship going flat out on her ear with hardly any sail set. Great sail.

[Jack Williams]

They are just installing the first tidal turbines in New Zealand, north of here at the Kaipara Harbour, which has a narrow mouth and a big inner expanse of water.

[Since1982]

Tidal Turbines just using oceanic waters repeatedly could bypass the needs for various energy sources and put the world in a much less dependent on fossil fuels situation. If ONLY we could bring ourselves to DO it. How do you convince the fossil fuel collectors to stop collecting and start re-using existing fuels like the oceans of the world?? I don't know if you can, the lure of "making oneself into a billionaire "no matter how much the planet is destroyed to bring that to pass is a very hard job to convince the collectors into stopping the collection.