| |
| 20 Apr 2008 04:56:06 |
| liz |
| Dove Pier Incident Report |
A soft copy of the in-depth report ("Lessons for Rowers") on the incident, which happened in October 2006 at Hammersmith, is now available for download from the Thames Regional Rowing Council Website. http://www.thames-rrc.org/safety/lessons-for-rowers/ All Thames region clubs have already been sent hard copies of the report, but it may well be of interest to clubs outside the region - especially those who visit the tideway to train or race. liz |
| 20 Apr 2008 20:08:30 |
| Carl Douglas |
| Re: Dove Pier Incident Report |
liz wrote: > A soft copy of the in-depth report ("Lessons for Rowers") on the > incident, which happened in October 2006 at Hammersmith, is now > available for download from the Thames Regional Rowing Council > Website. > > http://www.thames-rrc.org/safety/lessons-for-rowers/ > > All Thames region clubs have already been sent hard copies of the > report, but it may well be of interest to clubs outside the region - > especially those who visit the tideway to train or race. > > > liz > An excellent report. A first in UK rowing AFAIK I applaud the "no-blame" emphasis. I was particularly struck by the following paragraph: "5.12 The water safety function must be embedded in the highest level of command of any club. Its officers and members must not only know what the committee or other leadership expect of them, but also that the committee will make sure that it knows that they are living up to expectations and will, ultimately, make the chronic, un-educable back-sliders leave." I wonder how that goes down within the ARA, in view of the repeated efforts it has made to misrepresent the causes of 2 fatal accidents, to obstruct moves to enhance equipment safety, to spurn expert advice & to contradict the findings of 2 Coroners? Similarly: "6.10 (B) Tackling misbehaving members who have failed to respond to all attempts at explanation and education no matter how important they are to the club’s racing success; when all else has failed, rejecting members or coaches who put themselves, their colleagues, or other rivers users at risk or whose conduct brings the club or sport into disrepute." Similarly: "D.3.1 In our view, the first duty of a club’s committee (or its equivalent - practices, of course, vary, notably in school, academic or very small clubs) to its members and to the sport as a whole is to give leadership on water safety issues to the captain, coaches, CWSA and members." The vital importance of the classic "Chain of Events" to the creation of an accident is well stated on Page 34: "Had any one of the above circumstances not come into play this accident probably would not have occurred and you would have “got away with it”." That judgement would apply with equal validity to the ultimately fatal chain of events 8 years ago in Amposta. There was no single cause, but had appropriate courses of action been taken previously, when already it was known that they should have been, the chain would have been broken and a life not lost. B5.2 refers incorrectly to Fig B.1A With regard particularly to Section C: While we all understand the ultimate responsibility falling upon the person steering, I wonder how we address the questionable concept of adults imposing upon a minor a task carrying potential criminal liability? I can see this presenting obstacles to the availability of coxes - would parents of 13-year-olds be uniformly content if made aware of this situation? Might not some questions also arise regarding the known if not admitted defects in shell steering equipment? And, lastly, there is the most welcome recognition in D.4.2 that accidents should _never_ be dismissed as "unavoidable 1-off events". The only reason folk find this an easy cop-out is that, hitherto, we have not subjected significant mishaps to the kind of analysis seen for the very first time in this excellent report. Cheers - Carl -- Carl Douglas Racing Shells - Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK Find: http://tinyurl.com/2tqujf Email: carl@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682 URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers) |
| 20 Apr 2008 14:12:16 |
| liz |
| Re: Dove Pier Incident Report |
On Apr 20, 8:08=A0pm, Carl Douglas <c...@carldouglas.co.uk > wrote: > An excellent report. A first in UK rowing AFAIK Carl, thanks for your feedback, I know it will be appreciated. I believe everyone agrees that Neil, Bill and Stuart did a fantasic job on this report, especially given that 2 out of the 3 were doing it as unpaid volunteers. We can only hope it sets the standard for future serious-incident reporting. liz |
| 20 Apr 2008 17:04:00 |
| bookie |
| Re: Dove Pier Incident Report |
I particularly like this paragraph: > > Similarly: > "6.10 (B) Tackling misbehaving members who have failed to respond to all > attempts at explanation and education no matter how important they are > to the club=92s racing success; when all else has failed, rejecting > members or coaches who put themselves, their colleagues, or other rivers > users at risk or whose conduct brings the club or sport into disrepute." there are some people who are either just so stupid and incapable of grasping safety and navigation rules and there are those who are too blase about safety on the water and think everyone shoudl either get out of their way or that the rules do not apply to them at all for some unknown reason, but basically both classes of epople should not be allowed to go on the water for everyone else's safety and for the good of the sport, full stop, no argument, period, end of. even if these people do not injure or involve any other rowers as such in their accidents and general chaos on the water they may sometimes need rescuing and assistance when they get into trouble and wrap themsleves round a bridge or whatever, and as someone pointed out in another post on the tradegy in leipzig, the people who have to go out and rescue them sometimes have to risk their own safety to do so. just utterly utterly selfish of someone to go out on the water when they know they are incapable of steering a boat properly and controlling it (i have suffered from this particular issue, most unpleasant incident indeed) or when they have not bothered to read up on local conditions and navigation rules where they are boating. I mean; how long can it take to just quickly ask someone local "what side of the river shoudl i stay on here?" unless you are on the tideway when you probably need a 2 day seminar and a flip chart to explain all the nuances of that stretch but it is still not beyond most people. in fact ther was something in The Times the other day, thursday or friday (can;t remember which, wasn't saturday cos I failed to get a paper yesterday) about some sailling enthusiast who is known locally as 'Captain Calamity' because everyr time he goes out he capsizes his boat and needs rescuing at some considerable financial copst every time by the local coastguard, not only that but they have to risk their own lives going out to pick him up each time he does it. But he still goes out there regardless. As far as i know the harbour near him where he did sail from has banned him because of his incompetence and the cost of rescue and risks etc, so if they can do it, why can;t the ARA do similar if a club/individual gets themselves a poor track record on safety? discuss.... bookie |
| 21 Apr 2008 11:48:16 |
| Carl Douglas |
| Re: Dove Pier Incident Report |
liz wrote: > On Apr 20, 8:08 pm, Carl Douglas <c...@carldouglas.co.uk> wrote: > >>An excellent report. A first in UK rowing AFAIK > > > Carl, thanks for your feedback, I know it will be appreciated. > > I believe everyone agrees that Neil, Bill and Stuart did a fantasic > job on this report, especially given that 2 out of the 3 were doing it > as unpaid volunteers. > > We can only hope it sets the standard for future serious-incident > reporting. > > liz > Amen to all that. One thing well brought out in the latter sections of the report (but not in the earlier part, surprisingly) was that the tidal flow tends to sweep boats towards the outside of the bend. Water has a Newtonian tendency to keep on going in flow & direction & not to deviate until some time after it encounters any change in the shape or direction of the channel. So whether in ebb or flood, whether rowing or at easy, boats on the Middlesex (outside) station will always carry towards the outside of the bend & that means at that location the go towards the Dove Pier. Then there is the shear in the water between the fastest flow near the mid-stream and the far slower water in contact with the bed & banks. For a boat moving _with_ the stream on the outside of any bend, that means the water is faster, in their direction of rowing, under the blades which are nearer the mid-stream & often a lot slower under those closer to the bank. That imposes more load on one set of blades than on the other, also causing the boat to move towards the bank & thus compounding the centrifugal tendency of the stream itself. Unless coxes fully understand both effects, they remain at risk of treating the surface of the river as if it were a well surfaced road rather than an oily track with a deceptive outwards camber across which everything encourages the boat to slide towards the outer bank. Now to report, belatedly, another oh-so-close to disaster incident at Dove Pier: Some years ago an eight from an upriver club was rowing upriver against the ebb. As rowers will, they chose to stop for a chunter. And the place at which they stopped was some way above Dove Pier. The chuntering continued as the boat lost way & then began to drift back downstream. Stroke, who should have had his eyes about him, & cox (ditto) who had his back to the direction they were now following, were deep in conversation. Very late in the day someone further up the boat looked & realised that they were drifting from their proper station both sideways & downstream into the pier. A few very loud words from him, including the traditional "f***ing" for better effect, alerted all concerned. They put down their knitting &, just in time, got in a couple of none too smart strokes, on the first of which stroke's blade actually made contact with either the pier or, more likely, a boat moored to the pier. And thus they escaped. Of course, that incident should have been reported - under any proper safety regime. But there was no such regime. So no report. And no analysis. So no one familiar or unfamiliar with the dangers of that locality became any the wiser. Vital information, which would have made the river a tad safer, was lost. In a meaningful reporting system rowers should be able to review data for any given stretch of water. For each location there would be information, perhaps graphically represented on a map by an accumulation of spots of different colour (according to gravity of incident) and supported by a database detailing what led to the insertion of each spot. Problem areas would become immediately apparent. And all this could so easily be presented as web pages, where just clicking or mousing over a spot on a map would bring up the bare details of the relevant incident, & clicking on the location would deliver a list of recorded incidents. How difficult is that? How much of the ARA's not inconsiderable budget would that absorb? It's way beyond my competence but, given the undoubted wealth of web competence within this sport, & the general goodwill of rowers except when being told what to do by stuffed shirts in blazers, it should be easy to get a few dedicated souls to get such a system up and running. All they lack, of course, is the data which the ARA has squirrelled away or, dare I say it, dumped into the round file. Carl -- Carl Douglas Racing Shells - Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK Find: http://tinyurl.com/2tqujf Email: carl@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682 URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers) |
| 21 Apr 2008 08:55:55 |
| Re: Dove Pier Incident Report |
On 21 Apr, 11:48, Carl Douglas <c...@carldouglas.co.uk > wrote: > liz wrote: > > On Apr 20, 8:08 pm, Carl Douglas <c...@carldouglas.co.uk> wrote: > > >>An excellent report. A first in UK rowing AFAIK > > > Carl, thanks for your feedback, I know it will be appreciated. > > > I believe everyone agrees that Neil, Bill and Stuart did a fantasic > > job on this report, especially given that 2 out of the 3 were doing it > > as unpaid volunteers. > > > We can only hope it sets the standard for future serious-incident > > reporting. > > > liz > > Amen to all that. > > One thing well brought out in the latter sections of the report (but not > in the earlier part, surprisingly) was that the tidal flow tends to > sweep boats towards the outside of the bend. =A0Water has a Newtonian > tendency to keep on going in flow & direction & not to deviate until > some time after it encounters any change in the shape or direction of > the channel. =A0So whether in ebb or flood, whether rowing or at easy, > boats on the Middlesex (outside) station will always carry towards the > outside of the bend & that means at that location the go towards the > Dove Pier. > > Then there is the shear in the water between the fastest flow near the > mid-stream and the far slower water in contact with the bed & banks. > For a boat moving _with_ the stream on the outside of any bend, that > means the water is faster, in their direction of rowing, under the > blades which are nearer the mid-stream & often a lot slower under those > closer to the bank. =A0That imposes more load on one set of blades than on= > the other, also causing the boat to move towards the bank & thus > compounding the centrifugal tendency of the stream itself. > > Unless coxes fully understand both effects, they remain at risk of > treating the surface of the river as if it were a well surfaced road > rather than an oily track with a deceptive outwards camber across which > everything encourages the boat to slide towards the outer bank. > > Now to report, belatedly, another oh-so-close to disaster incident at > Dove Pier: > Some years ago an eight from an upriver club was rowing upriver against > the ebb. =A0As rowers will, they chose to stop for a chunter. =A0And the > place at which they stopped was some way above Dove Pier. =A0The > chuntering continued as the boat lost way & then began to drift back > downstream. =A0Stroke, who should have had his eyes about him, & cox > (ditto) who had his back to the direction they were now following, were > deep in conversation. =A0Very late in the day someone further up the boat > looked & realised that they were drifting from their proper station both > sideways & downstream into the pier. =A0A few very loud words from him, > including the traditional "f***ing" for better effect, alerted all > concerned. =A0They put down their knitting &, just in time, got in a > couple of none too smart strokes, on the first of which stroke's blade > actually made contact with either the pier or, more likely, a boat > moored to the pier. =A0And thus they escaped. > > Of course, that incident should have been reported - under any proper > safety regime. =A0But there was no such regime. =A0So no report. =A0And no= > analysis. =A0So no one familiar or unfamiliar with the dangers of that > locality became any the wiser. =A0Vital information, which would have made= > the river a tad safer, was lost. > > In a meaningful reporting system rowers should be able to review data > for any given stretch of water. =A0For each location there would be > information, perhaps graphically represented on a map by an accumulation > of spots of different colour (according to gravity of incident) and > supported by a database detailing what led to the insertion of each > spot. =A0Problem areas would become immediately apparent. =A0And all this > could so easily be presented as web pages, where just clicking or > mousing over a spot on a map would bring up the bare details of the > relevant incident, & clicking on the location would deliver a list of > recorded incidents. > > How difficult is that? =A0How much of the ARA's not inconsiderable budget > would that absorb? =A0It's way beyond my competence but, given the > undoubted wealth of web competence within this sport, & the general > goodwill of rowers except when being told what to do by stuffed shirts > in blazers, it should be easy to get a few dedicated souls to get such a > system up and running. =A0All they lack, of course, is the data which the > ARA has squirrelled away or, dare I say it, dumped into the round file. > > Carl > > -- > Carl Douglas Racing Shells =A0 =A0 =A0 =A0- > =A0 =A0 =A0Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories= > Write: =A0 Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK > Find: =A0 =A0http://tinyurl.com/2tqujf > Email: c...@carldouglas.co.uk =A0Tel: +44(0)1932-570946 =A0Fax: -563682 > URLs: =A0www.carldouglas.co.uk(boats) &www.aerowing.co.uk(riggers)- Hide q= uoted text - > > - Show quoted text - I agree with Carl that the report addresses the issues in a very objective and positive manner. Thirty or so years ago I was steering and coaching a crew of 14 year olds at Greenwich, with the tiers of barges moored several abreast on the edge of the fairway, we heard cries from a sculler from another club who had got himself athwart the vertical mooring chain at the downstream end of the tier; the flood- tide was at it's fastest. It was an extremely dangerous situation for the sculler, if he had capsized he would have been sucked under the 'trot of barges' 3 or 4 in number, and would probably been rendered unconscious by striking his head as the tidal flow brought him up under one of the barges. I manoeuvred my coxed four close to the upstream end of the barges and clambered onto it, having instructed my crew of boys to row back (coxless) to my club (approx. 200 metres) to get help; a launch was available and came out immediately. In the meantime I worked my way to the downstream end of the barges and managed to reach down and help to stablise the boat but, more importantly, to re-assure the sculler that help was on the way. He was extremely worried about possible damage to the club's boat, perhaps more so than his own situation. The launch duly arrived and approached from the safe direction, with great difficulty I must add, and he was persuaded to get aboard and the boat then disappeared under the barges. There are two obvious lessons from this account: 1. Never get into a situation where a tidal flow can take you onto a moored craft. 2. If you want to go sculling when there is a fast tide, always make sure that you are accompanied. I am sure the new code addresses the moored craft issue but there are two other points which concern me. Does it cover the situation of crews/scullers going out alone and is it sensible to send an inexperienced crew out on a fast flood-tide away from the clubhouse. At Greenwich the standard practice was to go in the direction which meant you returned with the tide; i.e. as you tired or, perhaps, had equipment failure, you would be 'brought home'. My time spent rowing from Chiswick taught me that this could not always be the right decision on the Tideway but it must be the safer option for inexperienced crews. |
| 22 Apr 2008 00:12:31 |
| Edgar |
| Re: Dove Pier Incident Report |
"Carl Douglas" <carl@carldouglas.co.uk > wrote in message news:fuhrdj$ses$1$8300dec7@news.demon.co.uk... > One thing well brought out in the latter sections of the report (but not > in the earlier part, surprisingly) was that the tidal flow tends to sweep > boats towards the outside of the bend. Water has a Newtonian tendency to > keep on going in flow & direction & not to deviate until some time after > it encounters any change in the shape or direction of the channel. So > whether in ebb or flood, whether rowing or at easy, boats on the Middlesex > (outside) station will always carry towards the outside of the bend & that > means at that location the go towards the Dove Pier. No argument about that, but I have always wondered why the outside of the bend just below Barnes Bridge is so shallow. It would seem that the answer must be that the incoming tide is more powerful than the outgoing and thus prevails and scours out the channel more towards Middlesex. But how can this be when the incoming water has to overcome the downcoming river flow while the ebb tide has the river stream helping it? Are the buttresses of the bridge forcing the outgoing water to alter course towards Middlesex? I seem to recall an eddy over the shallow bit on the ebb tide. |
| 21 Apr 2008 15:50:23 |
| David McC |
| Re: Dove Pier Incident Report |
On 22 Apr, 03:55, pdblas...@btinternet.com wrote: > > It was an extremely dangerous situation for the sculler, if he had > capsized he would have been sucked under the 'trot of barges' 3 or 4 > in number, and would probably been rendered unconscious by striking > his head as the tidal flow brought him up under one of the barges. > Or worse. Some of the kids in my old home town used to dare each other to go under the barges with the current and pop out the downstream end. Worked well until they picked a barge that was sitting on a sandbank. Sorry to be so morbid, but some people will never see danger coming. Taniwha |
| 22 Apr 2008 00:31:52 |
| Carl Douglas |
| Re: Dove Pier Incident Report |
Edgar wrote: > "Carl Douglas" <carl@carldouglas.co.uk> wrote in message > news:fuhrdj$ses$1$8300dec7@news.demon.co.uk... > > >>One thing well brought out in the latter sections of the report (but not >>in the earlier part, surprisingly) was that the tidal flow tends to sweep >>boats towards the outside of the bend. Water has a Newtonian tendency to >>keep on going in flow & direction & not to deviate until some time after >>it encounters any change in the shape or direction of the channel. So >>whether in ebb or flood, whether rowing or at easy, boats on the Middlesex >>(outside) station will always carry towards the outside of the bend & that >>means at that location the go towards the Dove Pier. > > > No argument about that, but I have always wondered why the outside of the > bend just below Barnes Bridge is so shallow. > It would seem that the answer must be that the incoming tide is more > powerful than the outgoing and thus prevails and scours out the channel more > towards Middlesex. > But how can this be when the incoming water has to overcome the downcoming > river flow while the ebb tide has the river stream helping it? > Are the buttresses of the bridge forcing the outgoing water to alter course > towards Middlesex? I seem to recall an eddy over the shallow bit on the > ebb tide. > > Try this for a partial explanation: As the ebb takes the tight bend onto the bridge a secondary, spiralling motion develops about its axis - the fast water near the surface moves towards the outside of the bend, dips down & returns more slowly back across the river at depth. That is a very tight bend & at higher states of the tide the ebb runs fast along the river wall to The Terrace, encouraging this secondary flow pattern. As the ebb rebounds off the tightest part of the bend, by the bridge, the flow moves back to the centre or even across the centreline of the river. So the flow near the wall declines, which reduces scour & encourages sediment to remain, while the spiralling pattern centrifuges sediment out of suspension, helping to build or maintain muddy deposits. The flood tide has a very different flow pattern, running pretty straight almost up to the bridge, so has no tendency to scour the Surrey shallows east of the bridge. Is that an adequate account? Cheers - Carl -- Carl Douglas Racing Shells - Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK Find: http://tinyurl.com/2tqujf Email: carl@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682 URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers) |
| 22 Apr 2008 21:45:31 |
| Edgar |
| Re: Dove Pier Incident Report |
"Carl Douglas" <carl@carldouglas.co.uk > wrote in message news:fuj85a$ltr$1$8300dec7@news.demon.co.uk... > Try this for a partial explanation: > > As the ebb takes the tight bend onto the bridge a secondary, spiralling > motion develops about its axis - the fast water near the surface moves > towards the outside of the bend, dips down & returns more slowly back > across the river at depth. That is a very tight bend & at higher states > of the tide the ebb runs fast along the river wall to The Terrace, > encouraging this secondary flow pattern. As the ebb rebounds off the > tightest part of the bend, by the bridge, the flow moves back to the > centre or even across the centreline of the river. So the flow near the > wall declines, which reduces scour & encourages sediment to remain, while > the spiralling pattern centrifuges sediment out of suspension, helping to > build or maintain muddy deposits. > > The flood tide has a very different flow pattern, running pretty straight > almost up to the bridge, so has no tendency to scour the Surrey shallows > east of the bridge. > > Is that an adequate account? Yes, I certainly think so as regards the difference between ebb and flood. Also, I can see that there must be a flow rate gradient from surface water to bottom water and accept that this can cause a spiralling effect on the ebb as you describe. However, just below the bridge it is clear that this spiral must be clockwise when looking down river on the ebb and accordingly, on the Surrey side the water must be spiralling downward before moving back at bottom level towards the centre of the river. Therefore it seems to me that this should mean that it is scouring the shallow part and carrying the silt etc. back out into the fast stream to be carried away downstream. Yet this does not seem to be happening. |
| 22 Apr 2008 21:21:04 |
| Carl Douglas |
| Re: Dove Pier Incident Report |
Edgar wrote: > "Carl Douglas" <carl@carldouglas.co.uk> wrote in message > news:fuj85a$ltr$1$8300dec7@news.demon.co.uk... > > Try this for a partial explanation: > >>As the ebb takes the tight bend onto the bridge a secondary, spiralling >>motion develops about its axis - the fast water near the surface moves >>towards the outside of the bend, dips down & returns more slowly back >>across the river at depth. That is a very tight bend & at higher states >>of the tide the ebb runs fast along the river wall to The Terrace, >>encouraging this secondary flow pattern. As the ebb rebounds off the >>tightest part of the bend, by the bridge, the flow moves back to the >>centre or even across the centreline of the river. So the flow near the >>wall declines, which reduces scour & encourages sediment to remain, while >>the spiralling pattern centrifuges sediment out of suspension, helping to >>build or maintain muddy deposits. >> >>The flood tide has a very different flow pattern, running pretty straight >>almost up to the bridge, so has no tendency to scour the Surrey shallows >>east of the bridge. >> >>Is that an adequate account? > > > Yes, I certainly think so as regards the difference between ebb and flood. > Also, I can see that there must be a flow rate gradient from surface water > to bottom water and accept that this can cause a spiralling effect on the > ebb as you describe. > However, just below the bridge it is clear that this spiral must be > clockwise when looking down river on the ebb and accordingly, on the Surrey > side the water must be spiralling downward before moving back at bottom > level towards the centre of the river. Therefore it seems to me that this > should mean that it is scouring the shallow part and carrying the silt etc. > back out into the fast stream to be carried away downstream. Yet this does > not seem to be happening. > > Edgar - The difference between the regimes causing scour or sedimentation lies largely in the flow velocity close to the surface & to the degree of turbulence. But turbulence also falls with fall in velocity. Unless the flow velocity just over the river bed is high enough to lift more particles than it drops, you get sedimentation. As the centre of the flow rebounds away from the Surrey bank, the stream velocity near that bank must fall (& you may also get back-eddies - which I think the low-water Google Map image, showing broken up deposits, tends to confirm). It is to that fall that I ascribe the transition from scouring to sedimentation. What say you? Cheers - Carl -- Carl Douglas Racing Shells - Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK Find: http://tinyurl.com/2tqujf Email: carl@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682 URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers) |
| 23 Apr 2008 00:02:45 |
| Edgar |
| Re: Dove Pier Incident Report |
"Carl Douglas" <carl@carldouglas.co.uk > wrote in message news:fulhbk$940$1$8300dec7@news.demon.co.uk... > Edgar wrote: >> "Carl Douglas" <carl@carldouglas.co.uk> wrote in message >> news:fuj85a$ltr$1$8300dec7@news.demon.co.uk... >> > Try this for a partial explanation: >> >>>As the ebb takes the tight bend onto the bridge a secondary, spiralling >>>motion develops about its axis - the fast water near the surface moves >>>towards the outside of the bend, dips down & returns more slowly back >>>across the river at depth. That is a very tight bend & at higher states >>>of the tide the ebb runs fast along the river wall to The Terrace, >>>encouraging this secondary flow pattern. As the ebb rebounds off the >>>tightest part of the bend, by the bridge, the flow moves back to the >>>centre or even across the centreline of the river. So the flow near the >>>wall declines, which reduces scour & encourages sediment to remain, while >>>the spiralling pattern centrifuges sediment out of suspension, helping to >>>build or maintain muddy deposits. >>> >>>The flood tide has a very different flow pattern, running pretty straight >>>almost up to the bridge, so has no tendency to scour the Surrey shallows >>>east of the bridge. >>> >>>Is that an adequate account? >> >> >> Yes, I certainly think so as regards the difference between ebb and >> flood. >> Also, I can see that there must be a flow rate gradient from surface >> water to bottom water and accept that this can cause a spiralling effect >> on the ebb as you describe. >> However, just below the bridge it is clear that this spiral must be >> clockwise when looking down river on the ebb and accordingly, on the >> Surrey side the water must be spiralling downward before moving back at >> bottom level towards the centre of the river. Therefore it seems to me >> that this should mean that it is scouring the shallow part and carrying >> the silt etc. back out into the fast stream to be carried away >> downstream. Yet this does not seem to be happening. > > Edgar - > The difference between the regimes causing scour or sedimentation lies > largely in the flow velocity close to the surface & to the degree of > turbulence. But turbulence also falls with fall in velocity. Unless the > flow velocity just over the river bed is high enough to lift more > particles than it drops, you get sedimentation. > > As the centre of the flow rebounds away from the Surrey bank, the stream > velocity near that bank must fall (& you may also get back-eddies - which > I think the low-water Google Map image, showing broken up deposits, tends > to confirm). It is to that fall that I ascribe the transition from > scouring to sedimentation. > > What say you? Well, I agree that must be the explanation for what is happening there because I cannot think of any other reason why it is so shallow. I can recall seeing back-eddies there at certain states of tide. Been there many times. but not lately as it is 5 years since I set foot in UK. |
| 23 Apr 2008 01:50:07 |
| AnatoleBeams@googlemail.com |
| Re: Dove Pier Incident Report |
Carl makes some interesting points about the dynamics of the tideway. > No argument about that, but I have always wondered why the outside of the > bend just below Barnes Bridge is so shallow. > It would seem that the answer must be that the incoming tide is more > powerful than the outgoing and thus prevails and scours out the channel more > towards Middlesex. > But how can this be when the incoming water has to overcome the downcoming > river flow while the ebb tide has the river stream helping it? > Are the buttresses of the bridge forcing the outgoing water to alter course > towards Middlesex? I seem to recall an eddy over the shallow bit on the > ebb tide. We all have a tendency to think about the water as a flat surface, but frequently it tricks us in the tideway as unseen eddies and whorls rise to twist boats on the surface. We have several 'hotspots' of interest up at Kew. Upstream of the bridge on the Brentford bend the water is canalised on the outside of the bend. As it flows downstream the whole column of water generally rotates, the surface flows strongly towards the Middlesex bank and down the metal wall. So it can make for challenging rowing on an outgoing tide with a strong stream. As you try to pull round the bend, the water pulls you over to the wrong side of the channel. Add to this any hesitation or slowing of boat speed or getting caught by the currents of any of the shallow spits and you can find yourself losing the stern end pretty rapidly. In the bad old days it was not entirely uncommon for boats to get caught up against the metal wall, much to the concern of their crews. As for the shallows at Barnes Bridge, take a look at the satellite shot from Google: http://maps.google.co.uk/maps?hl=en&ie=UTF8&ll=51.471787,-0.255389&spn=0.0083,0.01045&t=h&z=16 There looks to be bars running right across the river both here and also further up that may be stall points for the incoming tide which tends to flow more strongly as a basal flow with stream flow on top (we often have extended periods of rising water with outgoing flow, which can be very confusing for novices). Anatole |
| 23 Apr 2008 02:27:22 |
| TidewayUmpire |
| Re: Dove Pier Incident Report |
On 23 Apr, 09:50, "AnatoleBe...@googlemail.com" <anatolebe...@abdm.co.uk > wrote: > Carl makes some interesting points about the dynamics of the tideway. > > > No argument about that, but I have always wondered why the outside of th= e > > bend just below Barnes Bridge is so shallow. > > It would seem that the answer must be that the incoming tide is more > > powerful than the outgoing and thus prevails and scours out the channel = more > > towards Middlesex. > > But how can this be when the incoming water has to overcome the downcomi= ng > > river flow while the ebb tide has the river stream helping it? > > Are the buttresses of the bridge forcing the outgoing water to alter cou= rse > > towards Middlesex? =EF=BF=BDI seem to recall an eddy =EF=BF=BDover the s= hallow bit on the > > ebb tide. > > We all have a tendency to think about the water as a flat surface, but > frequently it tricks us in the tideway as unseen eddies and whorls > rise to twist boats on the surface. We have several 'hotspots' of > interest up at Kew. Upstream of the bridge on the Brentford bend the > water is canalised on the outside of the bend. As it flows downstream > the whole column of water generally rotates, the surface flows > strongly towards the Middlesex bank and down the metal wall. So it can > make for challenging rowing on an outgoing tide =EF=BF=BDwith a strong str= eam. > As you try to pull round the bend, the water pulls you over to the > wrong side of the channel. Add to this any hesitation or slowing of > boat speed or getting caught by the currents of any of the shallow > spits and you can find yourself losing the stern end pretty rapidly. > > In the bad old days it was not entirely uncommon for boats to get > caught up against the metal wall, much to the concern of their crews. > > As for the shallows at Barnes Bridge, take a look at the satellite > shot from Google:http://maps.google.co.uk/maps?hl=3Den&ie=3DUTF8&ll=3D51.4= 71787,-0.255389&sp... > > There looks to be bars running right across the river both here and > also further up that may be stall points for the incoming tide which > tends to flow more strongly as a basal flow with stream flow on top > (we often have extended periods of rising water with outgoing flow, > which can be very confusing for novices). > > Anatole Reference the 'bars' in the river; at a slightly higher resolution rate the one below BB seems to line up with Barnes High Street and looks like a path or pehaps a ford?? Certainly more 'definite' than the one above the bridge Might be too much Time Team!! [UK TV reference] |
| 23 Apr 2008 04:37:37 |
| Re: Dove Pier Incident Report |
On 23 Apr, 10:27, TidewayUmpire <pen...@aol.com > wrote: > On 23 Apr, 09:50, "AnatoleBe...@googlemail.com" > > > > <anatolebe...@abdm.co.uk> wrote: > > Carl makes some interesting points about the dynamics of the tideway. > > > > No argument about that, but I have always wondered why the outside of = the > > > bend just below Barnes Bridge is so shallow. > > > It would seem that the answer must be that the incoming tide is more > > > powerful than the outgoing and thus prevails and scours out the channe= l more > > > towards Middlesex. > > > But how can this be when the incoming water has to overcome the downco= ming > > > river flow while the ebb tide has the river stream helping it? > > > Are the buttresses of the bridge forcing the outgoing water to alter c= ourse > > > towards Middlesex? =EF=BF=BDI seem to recall an eddy =EF=BF=BDover the= shallow bit on the > > > ebb tide. > > > We all have a tendency to think about the water as a flat surface, but > > frequently it tricks us in the tideway as unseen eddies and whorls > > rise to twist boats on the surface. We have several 'hotspots' of > > interest up at Kew. Upstream of the bridge on the Brentford bend the > > water is canalised on the outside of the bend. As it flows downstream > > the whole column of water generally rotates, the surface flows > > strongly towards the Middlesex bank and down the metal wall. So it can > > make for challenging rowing on an outgoing tide =EF=BF=BDwith a strong s= tream. > > As you try to pull round the bend, the water pulls you over to the > > wrong side of the channel. Add to this any hesitation or slowing of > > boat speed or getting caught by the currents of any of the shallow > > spits and you can find yourself losing the stern end pretty rapidly. > > > In the bad old days it was not entirely uncommon for boats to get > > caught up against the metal wall, much to the concern of their crews. > > > As for the shallows at Barnes Bridge, take a look at the satellite > > shot from Google:http://maps.google.co.uk/maps?hl=3Den&ie=3DUTF8&ll=3D51= .471787,-0.255389&sp... > > > There looks to be bars running right across the river both here and > > also further up that may be stall points for the incoming tide which > > tends to flow more strongly as a basal flow with stream flow on top > > (we often have extended periods of rising water with outgoing flow, > > which can be very confusing for novices). > > > Anatole > > Reference the 'bars' in the river; at a slightly higher resolution > rate the one below BB seems to line up with Barnes High Street and > looks like a path or pehaps a ford?? > Certainly more 'definite' than the one above the bridge > > Might be too much Time Team!! [UK TV reference] In the 80s I rowed briefly for Cygnet (just opposite that bar). I vaguely remember someone saying that the river could be forded there by a tall person at low tide. Looking at that photo, it makes sense. I believe thet same is true at Westminster. Kit |
| 23 Apr 2008 05:00:45 |
| Re: Dove Pier Incident Report |
On Apr 23, 12:37 pm, kdav...@kidare.com wrote: > > In the 80s I rowed briefly for Cygnet (just opposite that bar). I > vaguely remember someone saying that the river could be forded there > by a tall person at low tide. Looking at that photo, it makes sense. I > believe thet same is true at Westminster. > Kit From one Cygnet to another, greetings. The anecdote sounds like Frank/ John Bull, who sadly passed away a couple of years ago aged 94. The second part of the legend is that there's a Hole, popularly credited to Hermann Goering's chaps, into which the unhappy person can fall a long way; can anyone see that on Google? Westminster I think was covered on TV maybe ten years ago; could have been Time Team but I'm not sure. ISTR that this bar - roughly from Florence Nightingale's statue at Tommy's Hospital, straight across to the terrace of the Palace of Westminster, on what used to be Thorney Island - is something the fire boats are familiar with grounding on near low tide. Possible end-point of the [Roman] Old Kent Road from Dover, then the ford, then up to Marble Arch and join the [also Roman] Edgware Road for Holyhead? ..... or perhaps I remember totally wrong Richard |
| 23 Apr 2008 09:39:44 |
| TidewayUmpire |
| Re: Dove Pier Incident Report |
On 23 Apr, 13:00, rdupa...@hotmail.com wrote: > On Apr 23, 12:37 pm, kdav...@kidare.com wrote: > > > > > In the 80s I rowed briefly for Cygnet (just opposite that bar). I > > vaguely remember someone saying that the river could be forded there > > by a tall person at low tide. Looking at that photo, it makes sense. I > > believe thet same is true at Westminster. > > Kit > > From one Cygnet to another, greetings. The anecdote sounds like Frank/ > John Bull, who sadly passed away a couple of years ago aged 94. The > second part of the legend is that there's a Hole, popularly credited > to Hermann Goering's chaps, into which the unhappy person can fall a > long way; can anyone see that on Google? > > Westminster I think was covered on TV maybe ten years ago; could have > been Time Team but I'm not sure. > ISTR that this bar - roughly from Florence Nightingale's statue at > Tommy's Hospital, straight across to the terrace of the Palace of > Westminster, on what used to be Thorney Island =EF=BF=BD- is something the= > fire boats are familiar with grounding on near low tide. > Possible end-point of the [Roman] Old Kent Road from Dover, then the > ford, then up to Marble Arch and join the [also Roman] Edgware Road > for Holyhead? > ..... or perhaps I remember totally wrong > > Richard Richard, You remember correctly, it was Time Team and that was thier conclusion. The Westminster crossing was forded in 'modern' times by Phillip Noel- Baker [then a Labour MP - later Lord PNB] sometime in '50's. Cant remember if anyone has done it since - anyone done the one at Barnes? After a good night at Cygnet perhaps? |
| 23 Apr 2008 14:13:54 |
| Malcolm |
| Re: Dove Pier Incident Report |
On 23 Apr, 17:39, TidewayUmpire <pen...@aol.com > wrote: > > > The Westminster crossing was forded in 'modern' times by Phillip Noel- > Baker [then a Labour MP - later Lord PNB] sometime in =A0'50's. > Cant remember if anyone has done it since - anyone done the one at > Barnes? After a good night at Cygnet perhaps? > The guy who tried to ford the Thames at Westminster was actually Lord Noel-Buxton. Noel-Baker was somebody completely different. The Times reported it as follows on 26 March 1952: "Lord Noel-Buxton attempted to walk across the Thames from St. Thomas=92s steps to the Speaker=92s stairs yesterday to support a theory =96= which he wishes to incorporate in a book he is writing about Westminster =96 that the Romans used to ford the river at that point. Lord Noel-Buxton, who is 6ft 3in, estimated that the maximum depth of water at low tide at 9am would be some 5ft 3in. He entered the river at 9.3am wearing shirt, pullover, flannel trousers and rubber soled shoes, and was able to reach the first pier by wading. He then had to swim for most of the way until he touched bottom some 20 yards from the Speaker=92s stairs. Lord Noel-Buxton said that there was more water than he had expected. =93The ford is undoubtedly there,=94 he said. =93The water was actually deeper than the chart depth, but I do not think that even when I was swimming I was far off the bottom. I feel I have proved my point.=94 " |
| 23 Apr 2008 22:23:04 |
| Christopher Shea |
| Re: Dove Pier Incident Report |
"TidewayUmpire" <penabc@aol.com > wrote in message news:599bd4d6-cb56-474c-8769-fe907360be31@f36g2000hsa.googlegroups.com... On 23 Apr, 13:00, rdupa...@hotmail.com wrote: > On Apr 23, 12:37 pm, kdav...@kidare.com wrote: > > > > > In the 80s I rowed briefly for Cygnet (just opposite that bar). I > > vaguely remember someone saying that the river could be forded there > > by a tall person at low tide. Looking at that photo, it makes sense. I > > believe thet same is true at Westminster. > > Kit > > From one Cygnet to another, greetings. The anecdote sounds like Frank/ > John Bull, who sadly passed away a couple of years ago aged 94. The > second part of the legend is that there's a Hole, popularly credited > to Hermann Goering's chaps, into which the unhappy person can fall a > long way; can anyone see that on Google? > > Westminster I think was covered on TV maybe ten years ago; could have > been Time Team but I'm not sure. > ISTR that this bar - roughly from Florence Nightingale's statue at > Tommy's Hospital, straight across to the terrace of the Palace of > Westminster, on what used to be Thorney Island ?- is something the > fire boats are familiar with grounding on near low tide. > Possible end-point of the [Roman] Old Kent Road from Dover, then the > ford, then up to Marble Arch and join the [also Roman] Edgware Road > for Holyhead? > ..... or perhaps I remember totally wrong > > Richard Richard, You remember correctly, it was Time Team and that was thier conclusion. The Westminster crossing was forded in 'modern' times by Phillip Noel- Baker [then a Labour MP - later Lord PNB] sometime in '50's. Cant remember if anyone has done it since - anyone done the one at Barnes? After a good night at Cygnet perhaps? The problem is no one ever remembers anything much after a good night at Cygnet. Chris |