To not understand tides?

[hardheadedwoman]

I am visiting a place soon that means you can’t get to it at high tide (Bosham)

I have found a website giving ‘tide predictions’ for this place

www.tidetimes.org.uk/bosham-tide-times-20210608

It seems that there is a high tide twice a day. I have so many questions!

How long does high tide last? If it’s high tide at 11.30am when will it be safe to reach my destination/how long do I have to wait?

Why are the high tide times so variable? There doesn’t seem to be any set pattern ie similar times of day.

Do people that live there have to plan their lives around these tides - what if you can’t get back to your house?

You can get to Bosham at any time. There is a risk that at some tides the road floods. Often cars submerge by drivers that park too close to the foreshore. From some parts of Bosham you can’t even see the sea. Just park up in the car park and you’ll be fine.

Tides vary depending on gravitational pull of moon mainly, but aren’t a set time each day because the position of the earth relative to the sun and moon changes.

Are you going to Thorney Island, it's old Mod land and I don't think anyone currently lives there. There is a bit of a guide to it here

Tides are caused by the moons gravitational pull on the earth, depending on the moons position depends on the tide times I believe.

@LemonRoses thank you that is very reassuring!

You can get to Bosham at any time just don't park on the foreshore by the pub. I've seen a car submerged there.

I understand it's the moon and the gravitational pull.

But, I can't think about it as it creeps me out.

We live near an island with a tidal causeway. As well as the usual tide tables the rnli publish a “safe crossing times” table which tells you how long you have between high tides to return.

High tide lasts minutes as does low tide (it doesn't move much though 30 mins either side). Around the country the variation between high and low varies a lot, where I live it's huge, one of the biggest in the world. The 3 hours either side of low tide is best in your circumstances. It changes by half an hour a day approx

I'm afraid I don't have any direct experience with Bosham, but have worked a lot with tides so can give you a brief overview.

It takes roughly 6 hours for the tide to go from all the way in to all the way out (High to low tide). So therefore takes 12 hours for the tide to go all the way out and then in again.

Where you're going will probably be inaccessible for a certain number of hours either side of high tide each time. It would probably be advisable to plan your trip around the 'low water' times at the area (6 hours after the published high water ones, or available online elsewhere), as you will be most certain of getting through an hour either side of the published low water time (because the water doesn't move very quickly for the first and last hours of the tide, so should basically by at it's lowest by then).

Also, each day the high tide at Bosham is between 30 and 40 minutes later, because rather than the round 12 hours I've talked about, it actually takes around 12 hours and 15 minutes.

Hope this helps, but sorry if I've confused things further!

Why are the high tide times so variable? There doesn’t seem to be any set pattern ie similar times of day

They aren't really. You get two every lunar day, which is just under 25 hours, so easy high tide is about 12 hours 25 minutes after the last one.

I swim on a remote beach a lot and live by the tide timetable as you can only
Climb down to it at certain tide times and levels. If you get caught not having got off the climb up ‘the goat track’ is stressful. Also depending on what winter storms have been doing the level of beaches can vary by easily 30 or 40 feet of sand being either dragged out or swept in by waves. So it’s often unswimmable for that reason too.
Have fun op.

Tides aren't completely random at all - they go forward by about half an hour every day. In fact they're really predictable.

If you ever go to the seaside, you really need to learn about tides. It stops all the pointless call outs to the RNLI when people are cut off by entirely predictable high tides.

You may find this link helpful

rnli.org/safety/know-the-risks/tides

At the bottom is also the link to the MagicSeaweed app.

Wow thanks all - really helpful! I shall be parking in the car park now!

I wish I’d paid more attention in Geography lessons!

You will also notice that 'high tide' isn't the same 'highness' every time. In Spring Tides, (when I think the sun is pulling the same way as the moon) the tide will come further up than at neap tides.

So a parking space that is fine one week, may become definitely not fine a week or so later.

One of my favourite memories from university was on a field trip when we nearly got cut off by the tide because the lecturer misread the tide table and forgot to account for BST. Made it back to the access point literally as the waves were coming in and the last of us got absolutely soaked.

Did I mention this was a Marine Science Course? The lecturer did not live that one down for a very long time

And spring tides are nothing to do with the springtime, but actually because the tide 'springs' from very low to very high and back, rather than dithering about in the middle. Springs versus neaps can make a lot of difference in some areas.

And each place, even each bay, can have its own tidal peculiarities, although as PP said, once you know them, they are very predictable. For example Southampton and surrounding area has a double high tide, where it comes in, is 'high water', recedes slightly, then come back shortly after before it ebbs (recedes) properly.

It's pretty fascinating, if you're a geek like me .

If the tides are caused by the moons gravitational pull on us, how come it works on millions of tonnes of liquid from so far away but it doesn't work on a 12 stone man standing on the moon???

It may be different in different places but on our bit of coast the high and low tides move forward just under an hour each day. You can buy a little booklet locally with all the times for the year, or use a tides app or the BBC website. So they are definitely not unpredictable you just have to check. Also how long the tide lasts depends on the terrain. At one end of our town it's deep enough to swim for at least two hours either side of high tide, but at the other end it only stays high enough to swim for about an hour each side of high tide. It must be to do with how flat or steep the beach/ocean floor is in that place.

As you can see from my specialist knowledge of my own area, people who live in or near Bosham will be able to advise you about when you need to be careful.

@Dyrne

One of my favourite memories from university was on a field trip when we nearly got cut off by the tide because the lecturer misread the tide table and forgot to account for BST. Made it back to the access point literally as the waves were coming in and the last of us got absolutely soaked.

Did I mention this was a Marine Science Course? The lecturer did not live that one down for a very long time

My kids school (in a seaside town with pebble beach) organised a school trip to a nearby sandy beach without investigating the tide situation. At that particular beach the high tide comes right up to the sea wall. They arrived by train with 60 reception kids armed with buckets and spades only to find no beach whatsoever and they weren't going to allow them in the sea for safety reasons. I'm very familiar with that beach and could have told them that (though obviously didn't know the high tide time off the top of my head) but I assumed they had done some research in planning the trip!

‘Heights or moon phases’ that should read.

I have only ever seen Shore Road submerged, and the end of Bosham Lane and the High Street. I have seen submerged cars on Shore Road. If you are in the car park it is fine and you can come and go as you please. Some of the footpaths on the front get covered but it would be fine to walk around, the water just laps in and out, though probably more violent if a storm. It is lovely and probably worth going before global warming gets worse!

If the tides are caused by the moons gravitational pull on us, how come it works on millions of tonnes of liquid from so far away but it doesn't work on a 12 stone man standing on the moon???

What do you mean? The moon's gravity DOES affect a man standing on the moon. That is why the men are able to walk on the moon instead of drifting off into space. There is gravity on the moon, and if you stand on the moon's surface you still weigh something. But you weigh less than you would on earth, because the moon's gravitational force is weaker than the earth's gravitational force.

The water on earth is affected by both gravitational force of the earth and the gravitational force of the moon. The earth "wins", otherwise all water on earth would be end up on the moon. But the moon still has a (relatively tiny due to the distance) effect on earth's water. But it's only noticable on really huge volumes of water (ie the ocean).

...or that's my understanding anyway. I've probably got some of the terminology wrong and I am sure others could explain it better!

Spring tides are like stealthy burglars. A couple of years' ago, completely randomly, we had a spring tide that quietly rose and rose, under all the doors of the pubs and houses near the beach and floated away all the beach huts.

I'd always imagined that sort of thing happened with big dramatic waves but no. The sea is a sly and untrustworthy force. I think that's why I love it so.