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The Thames - 'strong stream' red boards


MtB

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Much of the upper Thames is on red boards at the moment.

 

From the EA site:

"Caution strong stream" We advise users of all boats not to navigate because the strong flows make it difficult and dangerous.

 

The first thing I always want to know is what speed the 'strong stream' is running at? What is the actual speed of the current? This is important to me as the owner of a low-powered and slow NB! Unfortunately the EA website never says, and lock keepers never seem to know either. They only seem able to talk in terms of 'levels', and whether the river is 'level' or not, and how drawn their weirs are...

 

Walking along the towpath downstream at Goring yesterday showed the current to be roughly the same as the fastest I can walk, striding along very smartly, as I could just about keep up with bits of debris floating down the river. 4mph perhaps.

 

To me, the volume of water passing over each weir would give a very good indication of the likely speed of the current, . I'm sure the volume passing over each weir must be known, but is it published anywhere? Does anyone know?

 

Thanks.

 

Mike

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We went onto the Thames from Oxford...about 8 weeks ago.

It narrows there..and we were swept along at 6mph according to the satnav.

 

We couldn't stop before the first lock...I couldn't 'beat' the flow to get steerage..and hammered into the pontoon...throwing the engine forward and writing of my waterpump bearing and PTO shaft against the steel bulkhead.

A lot of this was to do with the fact that it was my first 'Thames' after the canal...and I really wasn't ready for it.

Bad 'boatmanship' I know.

 

It wasn't 'red' then...and Goring was flowing at about 2 MPH.

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Wow, and I'm trying to get UP the Thames onto the Oxford! Given up for now and moored the boat to wait for the current to moderate. My upstream progress was about one mile per hour yesterday, slowing to almost zero at full throttle in the occasional narrow or shallow bit.

 

Getting through Wallingford bridge is going to be difficult, having watched a boat that overtook me almost fail to pass through the centre arch. I'll HAVE to wait for the stream to slow a bit, or get a tow through, although the smaller arches look slightly slacker. Trouble is, if I can't get through the bridge, there's nowhere to moor downstream of Wallingford bridge for miles.

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I'm moored between Old Windsor and Bell Weir locks. I'd say it's running at about 3 knots at the most but we're only on yellow board on the EA website.

 

http://riverconditions.environment-agency.gov.uk/

 

I've seen a few boats coming downstream today and they were going quite fast! I wouldn't take my boat out at the moment, but mainly because I'm single-handed and it's a big boat. I've crossed the river twice today in my aluminium dinghy with a 4hp outboard and I've done that on the fastest red board conditions too. I don't think I'd have any problem taking a powerful plastic cruiser out today, but not a heavy, underpowered barge.

 

But since you appreciate that your boat is low-powered Mike, then why not just accept what the EA recommend? Why do you need to know the exact speed of the flow to know that your boat is unsuitable for red board conditions?

Edited by blackrose
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The first thing I always want to know is what speed the 'strong stream' is running at? What is the actual speed of the current?

 

The speed of the current will vary even when the total flow (volume) is a constant; where the river narrows - the bridges being amongst the tighter spots typically areas - the current must run faster to pass the same volume; the river will also tend to flow faster on the outside of a bend than the inside etc. So you shouldn't expect much more than a general answer, at best, which may prove unhelpful when you arrive at that exceptional bridge....

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Much of the upper Thames is on red boards at the moment.

 

From the EA site:

"Caution strong stream" We advise users of all boats not to navigate because the strong flows make it difficult and dangerous.

 

The first thing I always want to know is what speed the 'strong stream' is running at? What is the actual speed of the current? This is important to me as the owner of a low-powered and slow NB! Unfortunately the EA website never says, and lock keepers never seem to know either. They only seem able to talk in terms of 'levels', and whether the river is 'level' or not, and how drawn their weirs are...

 

Walking along the towpath downstream at Goring yesterday showed the current to be roughly the same as the fastest I can walk, striding along very smartly, as I could just about keep up with bits of debris floating down the river. 4mph perhaps.

 

To me, the volume of water passing over each weir would give a very good indication of the likely speed of the current, . I'm sure the volume passing over each weir must be known, but is it published anywhere? Does anyone know?

 

Thanks.

 

Mike

 

 

 

Just found this

 

http://www.mwronline.net/mrc/default.aspx

 

 

The flow rate for today is shown as 100.87 cubic metres per second

 

A month ago it was 24.61 M3/s

 

Keith

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I'm also moored at Goring atm, waiting to get the boat back to it's marina mooring at Abingdon. The local boatyard master informed me that not only is the stream an issue at Wallingford when in flood but the difference in levels either side of the bridge can be 4ft!!! :o

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Excellent stuff Kieth, exactly what I was looking for. Many thanks!

 

 

The flow rate for today is shown as 100.87 cubic metres per second

 

A month ago it was 24.61 M3/s

 

Keith

This is entirely consistent with my experience this weekend. I checked the river at Sonning on Friday and decided it was looking slack and decided to set out on Saturday. On Saturday things had livened up considerably but after finding I had enough power to tow a stricken NB I encountered a mile upstream to safety, I decided to carry on. On Sunday morning the stream had quickened again so I decided to moor up on the next available secure mooring and sit it out.

 

I need to get off the Thames and onto my new mooring on the Oxford before the weather deteriorates further and the red boards come out for winter, and before the stoppage at Slatt Mill lock on the Oxford add further delay.

 

I'm also moored at Goring atm, waiting to get the boat back to it's marina mooring at Abingdon. The local boatyard master informed me that not only is the stream an issue at Wallingford when in flood but the difference in levels either side of the bridge can be 4ft!!! :o

 

I can totally believe this, having watched a faster boat than mine really struggle to get through the bridge late yesterday afternoon.

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The first thing I always want to know is what speed the 'strong stream' is running at? What is the actual speed of the current? This is important to me as the owner of a low-powered and slow NB! Unfortunately the EA website never says, and lock keepers never seem to know either. They only seem able to talk in terms of 'levels', and whether the river is 'level' or not, and how drawn their weirs are...

The main thing is DO NOT attempt a turn just above a weir! Best go upstream quite some way first and turn so the bow ends up on the lock side of the channel - bear in mind a 6mph flow is 160 metres a minute.

 

Following on from that check the maps and see what side of the river the lock is on, you don't want to be heading for the weir instead of the lock. :o

 

Weirs and locks are easier to build where the channel is narrowest, so the stream tends to be fastest. Also the level downstream of a weir can change quite drastically over time, so not the best place to leave a boat tightly roped for more than a short time.

 

The lock keepers have to draw sluices on the weirs to maintain the levels *above* the weir, so the more the weir is drawn the faster the flow will be, and the bigger the rise in level *downstream* of the weir.

 

cheers, Pete.

~smpt~

Edited by smileypete
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I got caught out on upper Thames a month ago. Didn't look fast, although it was increasing flow, due to rain up in the Cotswolds apparently. Going downstream, the back end got caught on a bend very fast and before I new it the front caught as I tried to get round, and suddenly, amid crashing of branches and slamming of tiller, collapse of cycle rack etc, we were stemmed and stuck fast with a powerful flow holding us solid like a dam across the river. Luckily the rudder was not ripped out, but it was alarming. We couldn't pull off with a local 4X4, but luckily we were able to get some help from a Thames launch with a seriously powerful engine and heavy rope, after a few hours. This occurred in the narrows below Newbridge, where the placid wide stretch is constrained in a series of narrow, fast meanders.

A salutary lesson that you need to keep a close eye on why's going on with the water on the river, and any current is potentially a danger if you are not concentrating.

Edited by Tigerr
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This is entirely consistent with my experience this weekend. I checked the river at Sonning on Friday and decided it was looking slack and decided to set out on Saturday. On Saturday things had livened up considerably but after finding I had enough power to tow a stricken NB I encountered a mile upstream to safety, I decided to carry on. On Sunday morning the stream had quickened again so I decided to moor up on the next available secure mooring and sit it out.

 

I need to get off the Thames and onto my new mooring on the Oxford before the weather deteriorates further and the red boards come out for winter, and before the stoppage at Slatt Mill lock on the Oxford add further delay.

 

 

 

Don't forget there are several lock closures on the Thames from Nov 1st.

 

Regarding the bridge question, we went up through Radcot a month or so ago when there were yellow boards showing. The lock keeper described the bridge state as 'a bit sporting' but thought we would be OK. The flow was not all that fast, we got into the bridge hole and over half way through, then came to a stop and started moving backwards! Increasing the power made no difference. We dropped back, had some lunch, realised there had been some weed on the propeller so racked that off. Then had another go, exactly the same sequence but this time with the cleared prop a burst of extra power did push us through. As our boat was fairly wide and deep, filling a good percentage of the bridge hole, the level upstream must have been rising as we blocked the flow & so pushed us back.

 

Tim

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Excellent, thanks for that, Oar. I reckon that's running faster than here at Goring, too fast for Aldebaran to punch through.

 

I'll wait for it to moderate at Goring then press on as far as I can get. I hadn't appreciated there are Thames stoppages from Nov 1st either, so all the more important to take any opportunities to progress upstream as and when they present themselves.

 

The other option I have of course is to turn around and blasting down to Brentford and coming back up via the GU. Somehow this scares me more than dealing with the upper Thames!

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We are moored by the head of the river, below Osney lock. Took this video of the flow under Osney bridge yesterday. Glad its not just me who is chicken :)

 

 

 

Been through there ( downstream aboard Nuneaton ) when it was like that many years ago. Just about the most stupid thing I've ever done.

I tried to get to the moorings on the left but she wouldn't go that way, I managed to get in on the other side, where Morrell's Brewery used to be, and managed to get a line around one of the large bollards there. Even though she was in full reverse, the flow was still pushing her forwards. Eventually, I managed to haul her back and tied up, then I gave myself a slap!

 

Keith

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Think I'll stick to the canals for now

Just not got the experience for a fast river

 

I am a giant noob. It's been OK on yellow, not hit any sailing dinghies or killed anyone in a rowing boat. Mooring up is more difficult and 'hovering' is bloody impossible. Hard to compare with the canal really, water doesn't move for the most part :)

 

There are worse places to be stuck as well.

Edited by oarfish
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We are moored by the head of the river, below Osney lock. Took this video of the flow under Osney bridge yesterday. Glad its not just me who is chicken :)

 

 

I'm actually as concerned about the air draught under Osney Bridge as the flow. Last time I went under I think I had about 8" clearance, in normal summertime water levels.

 

Mike

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I'm actually as concerned about the air draught under Osney Bridge as the flow. Last time I went under I think I had about 8" clearance, in normal summertime water levels.

 

Mike

 

Mike, with that amount of flow you won't get near enough to find out.

The level doesn't vary much, it has to be kept down to avoid flooding the houses along there.

On another occasion that I was there when it looked like this, I asked the lock keeper what the level was like, he replied, same as Summer.

 

 

Keith

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I use this facility the EA has for the Thames and may do for other rivers - This is Osney:

 

http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/136495.aspx?StationId=7057&Sensor=U&RegionId=0&AreaId=0&CatchmentId=0

 

Do a google search for "river levels station data" and the name of the lock near where you are, i find it is helpful if i am away from the boat to see and predict what the river is doing.

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We are on a bit with yellow boards and going up and down on Saturday I used my phone's gps to get an approximate speed.

 

With the engine running at 1400 revs, a speed at which I reckon we do about 5mph going upstream in normal flow, we only managed 3mph upstream and 7.5mph downstream. Where the channel is narrow our speed drops to under 2mph at 1400 revs. On yellow boards the river is moving quite a bit but relatively gentle. We were moored on red boards above Wallingford earlier this year, that was completely different, seriously scary with the river running as fast as I could walk and then accelerating as it went through the bridge. It is a bit of a dilemma - based on my exceedingly limited experience yellow boards don't worry me, but the thought that the river may change to red boards whilst I am moving is a worry.

 

We are currently moored on the upstream moorings of a lock till the weekend, when I approached the lock keeper wallet in hand to pay for my moorings he said that we can have safe haven whilst the river is on yellow / red boards which means no charge. Very decent.

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Thanks Par.

 

Useful, but doesn't address my initial question.

 

How does one assess the strength of the stream from the levels data? I'm particularly interested now as despite an 8" drop in level, the stream has only moderated slightly today at Goring, AND the red boards remain up. In particular, why do the EA chose to use the term "STRONG STREAM" on the red boards when they don't know what the rate stream is flowing at?

 

Rhetorical question really. I don't expect an answer ;)

 

Mike

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