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View Full Version : A question about tidal rivers. From a "newbie."


gingernut
21st Jan 2018, 20:30
Trying to get to the bottom of this tidal problem.

As my centre of gravity moves upwards, I've decided to swap my surf board for a kayak. I know very little about the sea, other than I like either being in it or on top of it, and it needs to be respected. I've bought a vhf icom marine radio and qualified as a user yesterday, and met some great people who have spent many years floating around on the stuff :-)

I'm a bit confused about tides. I have some basic understanding of why and when and height and wind, spring tides and all that. Got a little retained knowledge about the effects of drift vs wind from my days at Barton.

My specific query is this:

If I wish to get the tide on "my side" is there a "lag" between the published tide times and estuary/river tides.

So, for example, if I wished to launch from Fowey (50.3350 N, 4.6365 W) to Golant (50.3621 N, 4.6423 W), common sense tells me that, for maximal exploring with minimal effort, (and getting back), I guess I should try and get to Golant for high tide ?

I've tried to get some answers from my nautical Cornish mates, who very helpfully sent some charts, which, to be honest, I don't quite understand !

As you can see from this, I prefer the view over effort.... https://www.youtube.com/watch?v=pkynRPIIi7M&t=6s

Ooooh also, I've downloaded the "decimal" co-ordinates from google, and this is how my phone displays them.

I'm a bit of of a degrees, minutes and seconds man, 'cos it makes sense. Will the Coastguard accept the modern format in the case of a distress or urgency call ?

Gertrude the Wombat
21st Jan 2018, 20:33
If I wish to get the tide on "my side" is there a "lag" between the published tide times and estuary/river tides.
No substitute for local knowledge - ask other local boaties.

Pontius Navigator
21st Jan 2018, 20:35
Don't forget slack water either side of high water.

Effluent Man
21st Jan 2018, 20:36
There has to be a lag. I regularly walk over a bridge that is about a mile from the river mouth. I notice that the flow does not correspond precisely with high and low water.

Bull at a Gate
21st Jan 2018, 21:49
Yes, there is a lag. Here in Oz we use the magic internet to get tidal figures at various locations, including up tidal rivers such as the Hawkesbury River just north of Sydney. We needed to know the precise time of low tide at Brooklyn last week so we could get our boat with its tall mast under the bridges which cross the river.

old,not bold
21st Jan 2018, 22:11
In the River Exe estuary, about 5 miles long before it narrows into the river itself, the difference between tides at Exmouth, at the southern end, and Topsham at the other is about 10 minutes. That's not much, and the reason is that it's East-West difference that counts (the moon's apparent track across the sky is more East-West than North/South) and Topsham is only 1.5 miles West of a line drawn due North from Exmouth.

The coastal tide, ie the tidal movement that flows along the coast reverses 4 hours after HW at Exmouth. So the slack period that occurs as the coastal tide reverses direction is totally different from the HW time experienced at the coast itself.

reefrat
21st Jan 2018, 22:28
:cool:Tide tables and atlas old mate, they list primary ports as well as a list of secondary ports with the time differences tabulated. Look up "The Rule of Twelths" , that will ease the paddle. If in doubt ask the local trawler men, they live and die by the tide, it saves fuel.

ralphos
21st Jan 2018, 23:32
For tide times I use an Android app called "Tide times". It has precise tide times for Fowey. The current direction change is usually delayed by 10-30 minutes. For tidal current directions and speeds you need the Admiralty Tidal Stream Atlas.

Read on tides and general sea kayaking tips on Kayarchy:
Kayarchy - sea & weather (4) the tides (http://www.kayarchy.co.uk/html/03thesea/005tides.htm)

Golf-Sierra
22nd Jan 2018, 11:24
You can find the time of high and low water here:

https://www.foweyharbour.co.uk/weather-tides

It is probably best to ask someone local, e.g. from one of the local sailing clubs what the flow is like -i.e. to work out how many hours prior to HW you need to depart from Fowey to get to Golant. The estuary is quite short so you may find that a couple of hours before and after HW there is actually very little flow if any.

You might also want to consult Reeds Nautical Almanac or a south west England cruising guide - available from chandleries, or perhaps 'look inside' on Amazon books. I used to have an iPad version of RNA, when I get home I'll see if the subscription is still valid.

Golf-Sierra

VP959
22nd Jan 2018, 11:48
TBH, there's no real substitute for local knowledge on tidal rivers, especially when you're more than about half a mile from the reference point in the tables.

I'd ask someone local, as you're likely to get much better info. I row up and down the Hamble a fair bit (as far as the Horse and Jockey for lunch and back), and try to time days to go when I'll have the tide with me on the row up and the tide and stream with me on the way back. It makes a LOT of difference to an old codger like me, who prefers an easy row any day!

Trossie
22nd Jan 2018, 12:07
Tides by mobile app? I can see things going horribly wrong quite soon. A lot of nature's quirks are best treated with respect and the hard-work of built up experience.

But then, there's always the tax-payers or those charitable donors that will cough up to send a Coast Guard helicopter or an RNLI lifeboat out for the rescue.

gingernut
22nd Jan 2018, 13:53
many thanks chaps !

old,not bold
22nd Jan 2018, 14:02
I could have added (above) that the Thames sailing barges that I watched as a boy in Southwold working up and down the coast would often simply anchor as soon as the tide turned against them, especially if they were beating into wind and therefore would make little or no progress. The seas off the East coast are quite shalllow.

It's a trick I've used many times when coastal cruising single-handed. Tuck in behind a headland to get out of the (adverse) wind, drop the hook, make sure it's in, and down below for a bite, a coffee, and a ziz.

As soon as the tide turns, up, up and away. Beating against the tide and wind is soul-destroying; 30-minute tacks and finish up with 200m gained.

RatherBeFlying
22nd Jan 2018, 16:39
In really strong winds in paddle craft, you can get out and push if you don't mind getting wet;)

A pole can come in very handy:E

Canoeing Lake Superior the wind and waves were too strong to get around a headland; so I went back to my last campsite in a inlet behind the headland and portaged;)

Golf-Sierra
22nd Jan 2018, 18:28
I just checked Reeds - the annual subscription still works despite being 5 years old :ok:

They only mention there is a ferry you need to look out for up the river. However, no info on the impact of tide. Ask around or just try starting out at say HW -2hrs. It's only about 2kms so either the tide will help you or at least you won't be fighting against it.

AeroSpark
22nd Jan 2018, 18:58
If you really want to confuse yourself come to the Solent, we get two high tides for the price of one!

yotty
22nd Jan 2018, 19:54
This might be of some use. Tidal Streams, West Country, Falmouth to Teignmouth : by VisitMyHarbour [Tidal Streams] - VisitMyHarbour articles (http://www.visitmyharbour.com/articles/3178/tidal-streams-west-country-falmouth-to-teignmouth)

gingernut
22nd Jan 2018, 20:01
For tide times I use an Android app called "Tide times". It has precise tide times for Fowey. The current direction change is usually delayed by 10-30 minutes. For tidal current directions and speeds you need the Admiralty Tidal Stream Atlas.

Read on tides and general sea kayaking tips on Kayarchy:
Kayarchy - sea & weather (4) the tides

Fab stuff :-) Thank you.

We do respect the blue and white stuff round here ! https://www.youtube.com/watch?v=VLtBwZFtNLI

SARF
23rd Jan 2018, 20:45
Tides can be considerably above and below predictions. And quite a bit earlier or later than forecast as well..
A stiff easterly and the water in the Thames can take an extra hour to start flowing out...
Kayaking you will have to deal with the wind as much as the tide as so little of your craft in under water ..
You can be cruising along with the tide and wind at your back. But as you turn with the tide into the wind it will get a lot choppier ..
Springs, neaps, tidal diamonds , etc etc Blah Blah. It’s endless. Enjoy!!!!