It is almost impossible to spend time on the coast of the UK or northern Europe and not be aware of the changing tides. Even inland seas like the Baltic and Mediterranean have some tidal changes. Many of the places that are wild and remote involve beaches, bridges and causeways. Many of these are only accessible at low tide and so being aware of tide times and the changes in the tide is essential to keep you safe. Many of the posts include details of when it is safe to make crossings or the best state of the tide for photography.
So what are tides in the first place? How can I find out when low tide is? How can this help me stay safe? If these are questions that you have then keep reading.
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What Are tides?
Tides are caused by the gravitational pull of the sun and the moon and the earth’s rotation. Imagine a large washing up bowl being moved around. The water moves from side to side with the movement of the bowl. The seas slosh and bulge in a similar way in response to the sun, moon and the earth’s rotation. The moon has a much larger influence on our tides and can be seen in the peak and flow of the tides with the cycles of the moon.
How Many Tides are there in a day?
There are usually two tides in a 24 hour period, two high tides and two low tides. The tides will not be at the same time each day as each high tide is 12 hours and 25 minutes after the previous high tide. This is why the high tide is 50 minutes later each day. If you know the time of high tide it is possible to work out roughly where it will be the following day although using tide tables makes it simple. If high tide is at 13:00 today then it will be at about 13:50 tomorrow and 14:40 the following day.
As an example:
High Tide is at 13:00
Low Tide will be at 7:12 and 30 seconds (6 hours and 12.5 minutes later)
High Tide will be at 01:25 (12 hours and 25 minutes after previous high tide) the following day
Low Tide next at 07:37 and 30 seconds
High Tide after 24hours and 50 minutes will be at 13:50
Tidal Range, High Water, Low Water, Springs and Neaps
As the tide comes in the water levels rise and the tide is said to be ‘flooding’. Eventually High Water (HW) is reached when the water is in as far as it goes. It will then be ‘slack’ for a while. This will vary depending on where you are. Some places have a very short period of slack water, others are longer.
Eventually the tide with start to go out or ‘ebbing’ until Low Water (LW) is reached.
The difference between high water and low water is called the tidal range. If the range is high then flow will be high and vice versa.
What is High tide ANd Low tide
High tide is when the beach or sand is covered in the most water. The waves will be breaking over the rocks and causeways will be totally covered. It is caused when the moon is at the closest or furthest point from the earth and the sloshing bulge of the water is at its greatest.
Low tide is when the sea is at its lowest point. This is when the earth is at right angles to the moon. This will mean that beaches are exposed, rock pools can be explored and tidal islands are accessible.
Spring Tides and Neap Tides
Now that we know the tide goes in and out and is related to the moons position to the earth there is a second factor to complicate things.
Depending on the phase of the moon (full moon, new moon, first and third quarter) the size of the tide will alter. These tidal changes are known as ‘springs’ and ‘neaps’.
Spring tides – These large tides occur when the sun, earth and moon are aligned (new moon and full moon) and the forces are at their greatest. Spring tides will be large with very high high tides and very low low tides.
This is useful to know if you want to visit some of the more secluded beaches where low tide is needed to get around headlands or see exposed features. Spring tides have nothing to do with the season!
Neap tides – These tides mean that water movement isn’t that large. In areas with a small tidal range you may not really notice a difference between high and low tide. They occur when the moon is in the first and third quarter and the forces from the sun and the moon are having a minimal effect.
Bristol Channel Tidal Range
The Bristol Channel has the second highest tidal range in the world of 12 metres to 14 metres. The only place with bigger tides in the Bay of Fundy in Canada. This extreme tide occurs because the channel is shaped like a funnel forcing large amounts of water into a small area. The tide comes in extremely quickly in these areas and you will not be able to out run the incoming tide.
To put this tidal range into context, the south east of England and parts of Scotland only see a small tidal range of 1 to 4 metres.
Where can I find out tide times – Tide Tables
As the tides are very predictable there are a number of places that you can find out the times of the tides for the week ahead.
Magic Seaweed – this has loads of other interesting charts, don’t fall down the rabbit hole!!
If you are visiting a place for a longer period of time or planning beyond a week ahead then it is worth investing in the tide times for the year. They can be purchased from Amazon and come in various formats – click here for options and prices
How to use a tide table
Tide tables will give the times of high water/tide and low water/tide and the tidal range. To figure out when the tide will be in or a crossing is safe you will need to follow these simple steps.
- On your chosen site select the area closest to your location. Not every beach or landmark is covered so select as close as possible to your location.
- Look at the times for high and low water. There will be two for each day. If you are looking to make a crossing then you want to see when the high or low tide is and work backwards or forwards from there.
- If you are looking for specific conditions then the height of the tide will be relevant as well. Check to see how high the tide will be in metres. Even half a metre higher on the low water level can make a crossing dangerous, not expose enough beach for the birds to come and feed or alter the amount of waves breaking over the rocks for a landscape photograph.
- Check the times used. Is the table using UTC (Coordinated Universal Time)? If it is then for the summer you will need to add 1 hour to adjust for British Summer Time.
Other Factors to consider
All through this I have said how predictable the tides can be, but there are a number of factors that can change the appearance of the tides and your safety. These are mainly strong winds and swells.
Effects of winds on the tide
In strong winds while the tide may have receded the wind can whip up large waves meaning that the beach is not safe to walk. If you are venturing out in a kayak or small boat, having ‘wind over tide’ can lead to very choppy and hard conditions. As well as looking at tide times you do need to look at the weather conditions.
Sea Swell and the Tide
After big storms large waves can roll in. This sea swell can push the tide in before you are expecting it, causing crossings to become cut off before the predicted time. If there have been periods of bad weather then it is important to look at the conditions and make an informed decision.
What should I do if I miscalculate the tide times?
Even with the best of planning when you get to your location you may find things are a bit different. A big sea may mean the beach isn’t as exposed as you expected or the causeway just isn’t clearing completely. You may get across to the island but take longer to get back to the crossing than expected.
Whatever happens you need to stay calm. Your number one priority is to stay safe. If you have adequate provisions, shelter and suitable clothing then staying where you are in a safe location is the best option. Once high tide has passed you will be able to make your crossing on the next low tide.
You should never attempt a crossing on an incoming tide. Some, such as the Bristol Channel will over take you faster than you can walk or run. If you are in danger and have no other options then you should seek assistance by calling the coastguard.