River Thames Flow Speeds

[MidnightStroller]

Morning All,

 

Apologies if this has been discussed before but I couldn’t find it on the search:

 

I have a 60x11 Piper Widebeam with a 60hp Beta in a Marina on the Thames near Bray. I am new to boating having only had 1.5-2 weeks cruising since I purchased the boat this year. 
 

Q. Is there a way of working out the speed of the river? I can’t find any useful websites with the info. I am really only interested in non-tidal Thames, particularly between Henley abs Shepperton.

 

We are on yellow boards (increasing) and have been all week. The river levels themselves are not a problem, I just want to make sure if I go out I can get back up stream. 
 

I have tried measuring the speed of floatsam by walking at pace with it using a gps. It’s around 2.5-2.8 mph (at least on the surface). I have been told she will make 3.8-4.5 mph. In theory it seems fine as I only want to go 1 mile downstream to empty the holding tank before winter and fuel up. 
 

Any advice would be appreciated. I am aware that going out on red boards may invalidate insurance. 
 

Thank you!

[Chewbacka]

Why not go up stream from your mooring and see how fast you can go against the flow.  If you make little progress you can ‘drift’ back to your mooring, if it’s easy should be no problem getting back from the pump-out - unless the river is significantly narrower downstream with a consequently faster flow.

[MidnightStroller]

I had considered that. My concern is that if I can’t get back into the Marina there are scant moorings downstream! Thank you

[john6767]

We were on the Thames during the last set of strong streams in the first half of October.  You can see the state of the river here http://riverconditions.environment-agency.gov.uk. but the EA are a bit tardy at updating it so it may lag by half a day on the actual state.  If the reach you are on is yellow increasing, then I would have thought staying put is the right answer.

 

As to speed of flow, we moved from Abingdon to Oxford on yellow decreasing, on the reach from Abingdon to Sandford we were initially making good progress, around 2.5 mph over the ground, but the last mile below Sandford took us 45 mins, and at one point

I had to increase revs a bit just to keep us moving very slowly forwards.  My point being is the flow speed can vary enormously even on the same reach, so I don’t think there is a simple answer to knowing what it it.

[mrsmelly]

Straight answer to this question is that it appears you are concerned and there is no problem with that its sensible boating attitude. If you are not 100 percent sure of you and your boats ability then do not move. If needed buy a porta potti until safe to move and fuel can be carried in jerry cans.

[Tonka]

So you think you can move and  are now doing so. A plastic bag snarls your prop and your knackered. 

Best not to move

[Murflynn]

.....  and have an anchor ready - not to be used to stop the boat except in dire emergency, but to hold your position if you do get caught out.

Edited November 1, 2020 by Murflynn

[OldGoat]

1 hour ago, MidnightStroller said:

Morning All,

 

Apologies if this has been discussed before but I couldn’t find it on the search:

 

I have a 60x11 Piper Widebeam with a 60hp Beta in a Marina on the Thames near Bray. I am new to boating having only had 1.5-2 weeks cruising since I purchased the boat this year. 
 

Q. Is there a way of working out the speed of the river? I can’t find any useful websites with the info. I am really only interested in non-tidal Thames, particularly between Henley abs Shepperton.

 

We are on yellow boards (increasing) and have been all week. The river levels themselves are not a problem, I just want to make sure if I go out I can get back up stream. 
 

I have tried measuring the speed of floatsam by walking at pace with it using a gps. It’s around 2.5-2.8 mph (at least on the surface). I have been told she will make 3.8-4.5 mph. In theory it seems fine as I only want to go 1 mile downstream to empty the holding tank before winter and fuel up. 
 

Any advice would be appreciated. I am aware that going out on red boards may invalidate insurance. 
 

Thank you!

Ah, yes - the entrance to Bray marina can be a pain....

 

It's good practice - despite what others on here who have scant experience of static waters - to always pick up a mooring, negotiate a narrow entrance, whatever by approaching from downstream. You can use the flow to moderate your speed and take advantage of the current to move your bow over towards the bank / whatever.

In your case move over to the right - as far as the mud will allow and point the bow to the rather narrow and not vert straight entrance and gun it.... For you paint's sake get a couple of proper sea going fenders and fix them forward (tow because you'll probably hit the entrance on the other side as well..

The marina staff are a friendly lot - so ask - If Terry (mechanic) is still there he might be persuaded - for a fee - to act as safety boat / tug to get you started.

It's very scary even in a 7ft wide boat the first few times...

 

Of course, you could always move to another well known marina further upstream where the entrance is much, much wider.....

 

60HP is reasonably adequate for the Thames, but for a newcomer it may be best not to venture out while there are any boards displayed. Once you've a bit of experience under your belt, yellow decreasing is worth a go and mebe move up to yellow increasing after you've had a season's thouough experience.

I have a 50Hp Beta in my NB and am confident to boat on Reds - but only if I get caught out. I do not cruise on my own by choice as you really need someone at the other end of the boat to handle the lines (Thames by laws require you to have a shore line for AND aft in the lock and it's a pain running about inside the boat to achieve that. After all 'we' must show we're better than all those plastic boats how to manage our vessels.

 

After all it's The Thames for heavens sake, there has to be some style to distinguish us....

Edited November 1, 2020 by OldGoat
added a bit more

[MidnightStroller]

55 minutes ago, john6767 said:

We were on the Thames during the last set of strong streams in the first half of October.  You can see the state of the river here http://riverconditions.environment-agency.gov.uk. but the EA are a bit tardy at updating it so it may lag by half a day on the actual state.  If the reach you are on is yellow increasing, then I would have thought staying put is the right answer.

 

As to speed of flow, we moved from Abingdon to Oxford on yellow decreasing, on the reach from Abingdon to Sandford we were initially making good progress, around 2.5 mph over the ground, but the last mile below Sandford took us 45 mins, and at one point

I had to increase revs a bit just to keep us moving very slowly forwards.  My point being is the flow speed can vary enormously even on the same reach, so I don’t think there is a simple answer to knowing what it it.

I’ve noted how slow EA are at updating!

 

thank you for your advice 

26 minutes ago, Murflynn said:

.....  and have an anchor ready - not to be used to stop the boat except in dire emergency, but to hold your position if you do get caught out.

I have w very sizeable anchor, chain and rope always good to go (I may have overestimated the requirement but it will work!)

[MidnightStroller]

13 minutes ago, OldGoat said:

Ah, yes - the entrance to Bray marina can be a pain....

 

It's good practice - despite what others on here who have scant experience of static waters - to always pick up a mooring, negotiate a narrow entrance, whatever by approaching from downstream. You can use the flow to moderate your speed and take advantage of the current to move your bow over towards the bank / whatever.

In your case move over to the right - as far as the mud will allow and point the bow to the rather narrow and not vert straight entrance and gun it.... For you paint's sake get a couple of proper sea going fenders and fix them forward (tow because you'll probably hit the entrance on the other side as well..

The marina staff are a friendly lot - so ask - If Terry (mechanic) is still there he might be persuaded - for a fee - to act as safety boat / tug to get you started.

It's very scary even in a 7ft wide boat the first few times...

 

Of course, you could always move to another well known marina further upstream where the entrance is much, much wider.....

It can be a tricky entrance. I knew that facing upstream you always have more control. Your advice seems to mirror my ‘plan’ I had thought of. Porta-potti en route and I have enough fuel for a few months - always like to keep everything full just in case. 
 

Which marina has the wide entrance out of interest? I’m happy here - it’s close two work when I need to be here and not at home. 
 

thanks for your thoughts. 

[OldGoat]

5 minutes ago, MidnightStroller said:

It can be a tricky entrance. I knew that facing upstream you always have more control. Your advice seems to mirror my ‘plan’ I had thought of. Porta-potti en route and I have enough fuel for a few months - always like to keep everything full just in case. 
 

Which marina has the wide entrance out of interest? I’m happy here - it’s close two work when I need to be here and not at home. 
 

thanks for your thoughts. 

Shh - my secret. Ask at Bray's office as to who it is. It's not at Reading, not owned by MDL and occcasionally has some very grand visiting boats...

[Murflynn]

Harleyford

[OldGoat]

3 minutes ago, Murflynn said:

Harleyford

Sneak!

[Alan de Enfield]

1 hour ago, MidnightStroller said:

I have w very sizeable anchor, chain and rope always good to go (I may have overestimated the requirement but it will work!)

How do you know ?

Its very easy to become complacent "I'll be fine I've got an anchor"

 

You need to practice deploying an anchor, it is not a case of 'throw it over the side'.

Are you deploying from the Bow or Stern ?

How are you going to deploy an anchor which has a weight suitable for a widebeam ?

Is the bitter end attached ?

Is the anchor type and weight suitable for your boat ?

What strong point is it attached too ? (A T-stud will just snap-off under load)

 

Get out on a day with a steady flow and practice, practice, practice.

If you NEED to use the anchor you need it to work first time you will not have chance to pull it back in and try again and again and again.

[Tonka]

What do you mean by this remark.

" good practice - despite what others on here who have scant experience of static waters - to always"

 

I have had a narrowboat moored on the thames for 30 years. Had grp cruiser before. Was employed by Thames Conservancy as a boatman. Moored actually in the flow not in a marina. If I put the rudder over and Eddie's form, I do not move. 

[Onewheeler]

6 hours ago, MidnightStroller said:

Q. Is there a way of working out the speed of the river? I can’t find any useful websites with the info. I am really only interested in non-tidal Thames, particularly between Henley abs Shepperton.

 

I think you'll find that the speed of the water may be less than you think. Last time I went out in a flood (marginal yellow / red boards) I reckon the current below Osney (where it does whizz through) was mostly around 4 - 5 km / h. It was probably faster above Osney, but it's fast there whenever there's fresh. We made progress but slowly. It was going much faster through Folly Bridge. Beware of bridges, they are dangerous in flood conditions. Even in the 2014 floods I doubt if the current was much faster than that.

 

Calibrated pooh sticks are the easiest measuring device.

[Murflynn]

a little used technique that is worth knowing is the ferry glide.

with the boat pointing upstream you can balance the speed as necessary and use the helm to steer slightly one way or the other - the boat will glide across the river under perfect control.

for example you can use it to reach the far bank or allow the boat to slip slowly downstream through a narrow bridge.

[OldGoat]

52 minutes ago, Murflynn said:

a little used technique that is worth knowing is the ferry glide.

with the boat pointing upstream you can balance the speed as necessary and use the helm to steer slightly one way or the other - the boat will glide across the river under perfect control.

for example you can use it to reach the far bank or allow the boat to slip slowly downstream through a narrow bridge.

Ferzackerly - impresses all the other moored boats..

(Don't do it if nobody's watching!)

 

[LadyG]

7 hours ago, Tonka said:

So you think you can move and  are now doing so. A plastic bag snarls your prop and your knackered. 

Best not to move

Ever.

[dmr]

If you are not experience/confident on a river then don't go out when its flowing. Having boat speed enough to make headway against the flow is only a small part of it. If you are heading downstream and need to stop for any reason then can you do this? The boat will have less speed in reverse but you need significantly more boat speed that river speed to stop in a reasonable time, and its a bit like doing a long reverse....are you happy reversing? Anticipating what is going to happen on bends is another factor.

 

...............Dave

[blackrose]

For reference I've gone upstream on that reach on red board on my 57 x 12ft widebeam with a 55hp engine. However, I know that my engine, gearbox and prop are well matched and I've a bit more experience than you. 

 

I very much doubt that your Piper would have any problem on yellows or even reasonable red boards, but personally with your level of experience I wouldn't venture out on yellow or red boards. My advice is only go out on yellows with help from someone with more experience.

Edited November 1, 2020 by blackrose

[blackrose]

8 hours ago, mrsmelly said:

Straight answer to this question is that it appears you are concerned and there is no problem with that its sensible boating attitude. If you are not 100 percent sure of you and your boats ability then do not move. If needed buy a porta potti until safe to move and fuel can be carried in jerry cans.

 

Yes if you did come a cropper, stuck on a weir or across a bridge you'd feel a bit silly having moved in order to empty a shit tank.

[MidnightStroller]

I have a partial solution to my actual question in the OP. Thank you to all who commented. 
 

It appears that neither the EA (nor anyone else) publicly give Thames flow speeds. 
 

I fell back on open water sailing knowledge and bought a speed log (shows speed through the water). I’ve rigged it to a phone bty pack (12v) and can dip in the water from the bank or anywhere in the stream if I deploy the SIB to read the speed of the river (assuming I’m stationary). I can also thus confirm my own boats best speed through the water - this will avoid the guess work. 
 

As mentioned - porta potti arriving tomorrow so I won’t be going out just for a PO. 

[blackrose]

But if your pump out and porta potty are both full you may have to go out for a POO! ?

[Alan de Enfield]

19 minutes ago, MidnightStroller said:

I’ve rigged it to a phone bty pack (12v) and can dip in the water from the bank or anywhere in the stream

As I'm sure you are aware from your sailing days the rate of flow close to shore will be a very small fraction of the flow in the centre of the river due to shallow depth and ground friction.