Tides Help

This site has been developed by digimap with the hope that it will assist with the enjoyment of your boating.

The site has 2 main pages, the prediction of when you can pass in and out of the respective marina and the depth of water over the sill at various times.

Below is some information that may be of assistance to you.

Marina gate prediction times

The system calculates the times you should be able to pass over the sill of the respective marina. It is calculated based on the tidal predictions, but can vary due to barometric pressure, wind direction and strength and many other factors. Additionally, gates may be affected by the speed of the flow of water over the gate.

The QEII marina has been fairly well tested and appears to be accurate but feedback from users based at the other marinas would be welcomed.

If you are not based in a marina, the system can still assist you. Please carry out the following.

• Choose Beaucette Marina as a guide
• Make a note of the time your boat floats, then you should do the following
• Select the day when you noted the tide time
• Adjust the draught required at Beaucette until the time agrees with the time you noted

This effectively establishes a height above the Beaucette sill when your boat will float.
Beaucette was chosen as it has the lowest sill height and this calculation will not work below this height.

The system does take into account the dropping gates at QEII and St Sampsons marinas.

Height above sill

This may be used for a number of purposes.

It could be used for working out the time you can get into other areas around the Channel Islands.

One main use is to know the height at various tides. If you select the "Height above Chart Datum" you get the tide heights every half an hour.

Take this scenario
You moor at the back of Herm at Shell Beach but do not want to dry out.
The "Depth of water above Chart Datum" table show that you are presently 4.5m above chart datum. You draw 1m and Low Tide will be at 2m. So the tide will go down a further 2.5m and you need an extra 1m meter - so as long as you are in 3.5m of water - you should not dry out.
You look at your echo sounder and it says there is 4m of water under the boat - so you are fine.

Another scenario, you moor and there is 4m of water below your boat. High tide is in 5 hours and will be 9.2m. You look at the "Depth of water above Chart Datum" table and it says the height is presently 3.2m. So you need to put out enough chain / rope to cope with a 10m of water.

If you do think of any other uses then please do let me know.

We do hope you enjoy the site and will think of digimap for all your mapping requirements.