Tidal rise and fall.

[Old Man Dave]

The Channel Islands have some of the greatest rise and fall of tide in the world. Here in Guernsey It goes up or down nearly 10metres/33 feet, vertical rise or fall, in 6 hours. we have just had one of the biggest tides of the year over the last few days. Our neighbouring island Jersey has a near 40 foot tidal range.

Took this picture of the high tide at 8am on my way to work and the picture of the low tide, from the same spot, at 4pm on my way home.

Big tides effect our diving, boating and lots of other aspects of our lives in such a small island. Big rise and fall also produces fierce tidal flows and reefs and rocks appear as if by magic as the water ebbs away to the low tide mark.

I know that in many places especially nearer the equator the rise and fall of tide can be measured in inches but generally I am pretty ignorant of the situation world wide. Anyone care to enlighten me either in general terms or more likely specific to where they live?

Dave.

 

[azapa]

Tsunamis aside, we normally get about 2M swings high to low. I would guess year high swing to be around 3m. Most of our coast shelves deeply though, 20M from out from the rocks we often have 10 to 12M depth. Even from a sandy beach, 50M out it is normal to find 6 to 8M depth.

 

[laminar]

Here in Vancouver we get 5m changes. Lots of fun!

In Nova Scotia, in the Bay of Fundy, you can expect tidal bores and changes of up to 15m. It is very strange to see the ocean actually disappear at low tide. But that's also due to a very slowly sloping bottom and mud flats.

 

[Bill]

Just did a quick check of the tables. Max low to max high (for the year) is less than a meter.

 

[agbiv]

Ours here in Texas are normally less than a meter but in Maine, where I visited last summer, as much as 10 m!

 

[scottie3030]

were the same as you dave in the Bristol channel +/- 10m, viz is always pants but it used to be good cod ground on the rod and line! i fished it for 2 winters around portishead and around the severn bridges had 1 codling for 5lbs

 

[sunfish]

It goes to around 4.5 metres here. That produces some stiff tidal currents in places.
It must really let rip off Guernsey and Jersey.:blackeye

 

[tonyiannu]

In Italy you wont even notice the change that is about 5-6 inches but all I know that it affect the marine life anyway.:friday

 

[Bill McIntyre]

On the Gulf of Mexico side of Florida where I grew up, the change was minimal. Here in Southern California, it is in the neighborhood of 3 meters at the full and new moons.

In Florida, the docks all stood on pilings. Out here, the docks all float so they can rise and fall with the tide.

 

[sunfish]

In Florida, the docks all stood on pilings. Out here, the docks all float so they can rise and fall with the tide.

The docks here are on pilings or cast in concrete. It's not unknown for newbies to tie up their boat at high tide and...... you can guess the rest.
You can buy a boat here and take it out with no training, license or experience. Many people do. I did myself but at least I read about it first.rofl

 

[sross]

Anyone care to enlighten me either in general terms or more likely specific to where they live?

Heh, heh,

Here on Lake Ontario where I live now, the tide is never more than 10 cm, and it's more usually 6 or 7 cm. Not even noticeable since the waves are usually bigger.

The biggest freshwater tides in N. America occur in Lake Superior, about 20 cm.

I have lived at the NE end of the Bay of Fundy between New Brunswick & Nova Scotia, and it has the highest tidal heights, over 16 m. Creates massive currents that make some sea channels and estuaries look like river rapids. Tidal bores go up all the rivers that feed into the bay, and in the Saint John river, there is a real rapids that reverses during rising tides, with sometimes a huge surge at a sill (3 m).

The highest tide ever recorded in the world ( 21.6 metres, in 1869) occured in the Minas Basin at the top of the Bay of Fundy. I've hiked out to a cliff overlooking the channel into the Minas Basin, and even though it's about 6 km wide, it roils up just like a fast river. I've been told that the currents can reach 8 or even 10 knots. Most of the local fishermen would plan their channel passages for slack tides, because you can waste an awful lot of gas fighting a current like that, and running with the currents sometimes sailors have lost control and been driven ashore or onto rocks.

The docks in the area were sometimes made of medium height out over a soft bottom that would allow the boats to settle onto the mud or sand at low tide, but of course, you could only move your boat at high tide. A fellow has made a great video showing this here:

[ame=http://www.youtube.com/watch?v=5W2sM1Ma7YA]YouTube - Fundy Tides - Scotts Bay Timelapse[/ame]

The docks that allowed use at all times were very high, and even then the boats would sometimes get grounded. They had ladders going down between the cleats. When a boat was way down at the bottom of the pilings it was a long climb down & back up. Great exercise.

Some info here: Highest Tides in the World

Hopewell Cape in New Brunswick has soft rock that has been carved into fantastic shapes by the tidal currents ( [ame=http://www.youtube.com/watch?v=yRbvvzK-ll0]YouTube - Hopewell Rocks, New Brunswick, Canada[/ame] )