Tides & Currents Videos

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Tides are generated by the gravitational pull between the sun and the moon on the water. Since the moon revolves around the earth, and in turn both the earth and moon revolve around the sun, the water mass on the earth’s surface changes all the time. We experience this as a vertical rise and fall of the sea levels on a daily basis. 

Rising water is called ‘flooding’ while dropping water, is called ‘ebbing’.

The moon has more influence than the sun on earth’s tides (2/3 compared to 1/3), because even though the moon is much smaller than the sun, it is very much closer to the earth than the sun. 

Spring and Neap tides: 

While the moon orbits around the earth, it has a varying degree of gravitational pull on the water.

Spring tides occur when the sun and the moon are in line with each other (as shown in the diagram). This causes the highest high tide and the lowest low tide at the location. Spring tides occur at both the full and new moons. 

Neap tides occur when the sun and the moon are at right angles to each other. Their opposing gravity acts as a competing force to attract the water on the earth. For this reason, tides do not change dramatically between high and low tide times. Neap tides occur at the halfway point between full and new moons. However, the high tide will be in front of the moon who has more influence than the sun because it is much closer.

We always refer to a current based on the direction it moves to as opposed to the wind, where we refer to the direction it comes from.

Wind comes from…, current goes to…’

A north-west current and a north-west wind actually move in the opposite direction whereas a south-east current and a north-west wind move in the same direction. 

Cross Shore and Rip Currents :

As each wave breaks, it transports water towards the shore. Before the water can flow back, the next wave breaks and transports more water shoreward.

This accumulation of water cannot return seaward due to the incoming waves, so it begins to flow parallel to the coast as a longshore current (or cross shore current) into areas where waves are smaller and the build-up of water is less. 

Eventually the longshore current transports so much water into an area of lower waves or meets with another current, moving the water flow seaward against the incoming waves to form a rip current which flows seaward perpendicularly to the shoreline. Rip currents are usually fairly swift and narrow and oppose the incoming waves. Waves may break farther offshore or refract around the rip current. We can often observe lower crossing waves where rip currents happen. 

Rip currents can be seen as strips of flatter water among the waves. When someone is caught in a rip current, they tend to panic as they see themselves moving away from the shore. To save their life they often tend to swim against the current to go back to the shore. This is the last thing to do because the current is stronger and after a while of fighting without results, the person can easily drown. 

Someone caught in a rip current must do the following to escape it easily:

Try to breathe normally, save your energy and try to let yourself float.

Remember that the rip current will only drag you away a short

distance from the shore, and sometimes, can even bring you back to shore further away without you having to swim.

Try to swim sideways away from the current to get out of the rip (swim towards the waves either side of the rip).

Most of all, do not panic!!!

Are Currents Good for Kiteboarding? On some occasions, yes, but other times, they can spoil a kiteboarding session, even on a good wind day. 

As a rule of thumb, it is important to remember that a current going in the opposite direction of the wind increases the power of a kite, while a current going in the same direction as the wind decreases its power.

Currents are generated and their strength and direction vary depending on the tide phases. 

The tidal range is the difference in height between any given high and low tides.

There exists a ‘Rule of Twelfths’. This gives us a rough estimate of the waters height at each hour. It also gives an indication of the speed of the tide. 

It is important to remember that in the mid- low and high tide there will be 2 hours with stronger current when it may not be as recommended to go kiteboarding. This is followed by 4 hours of stability (right before, during and after high or low tide) when kiteboarding would be better.

High water = 6.5m / Low water = 0.5m

Tidal range = 6m

The tidal range is then divided by twelve, as determined by the ‘rule of twelfths.’ This gives us the

value of 1/12 of the tidal range = 0.5m

The rule of twelfths then estimates the volume of water moving at each hour throughout the six-hour tide phase:

1st hour - 1/12 = 0.5m.

2nd hour - 2/12 = 1.0m.

3rd hour - 3/12 = 1.5m.

4th hour - 3/12 = 1.5m.

5th hour - 2/12 = 1.0m.

6th hour - 1/12 = 0.5m