jonny777 Posted February 12, 2014 Share Posted February 12, 2014 I have heard a lot about the pros and cons of dredging the various rivers, which apparently silt up over a period of time if left to their own devices. However, I have heard nothing about where this 'silt' originates? Obviously, it is from somewhere far upstream, but would it not be possible to try and discover who is losing all this stuff into the rivers in the first place and ask them to to do something about it? (As you can tell, I am not much of an expert on river management.) Link to post Share on other sites More sharing options...
The Lurker Posted February 12, 2014 Share Posted February 12, 2014 most silt will appear in rivers as part of a natural process as rainwater picks up soil particles or erodes rocks. It may get exacerbated in areas of poor farming practice or where soils are not long term suitable for farming but that is not something that is generally relevant to the UK these days AFAIK (that's more your effects of deforestation as per geography O level 1983) Link to post Share on other sites More sharing options...
bike2steam Posted February 12, 2014 Share Posted February 12, 2014 I presume that is river water well outside it normal running area. And to think the 'south' was in dire straits a couple of years ago with reservoir levels well-low due to lack of rainfall. The (usually small) River Tone is about 200 yards to the right of the picture, but a quarter of a mile down the road (facing the direction in the pictures) is Burrow Bridge, where the Tone joins the Parrett which is ( supposed to be) one of the Somerset Levels main drains. And yes, a few years ago reservoirs were in a dangerously low level Link to post Share on other sites More sharing options...
RMweb Gold Captain Kernow Posted February 12, 2014 Author RMweb Gold Share Posted February 12, 2014 And not far from Taunton. Sorry not railway, but gives you a good idea of the problem. Thanks for posting that, Paul. I was wondering what the situation would be like there. We once stopped off there to buy a wicker basket. As it happens, the business moved to Langport (I think) a few months or so ago, so I suspect that the building was empty. Link to post Share on other sites More sharing options...
bike2steam Posted February 12, 2014 Share Posted February 12, 2014 I have heard a lot about the pros and cons of dredging the various rivers, which apparently silt up over a period of time if left to their own devices.(As you can tell, I am not much of an expert on river management.) In modern society, if things go wrong, there has to be a scapegoat. If all the rivers, and drains, on the Somerset Levels had been dredged it still wouldn't have stopped all the flooding given the volume of water, personally I blame him up there- Big G, perhaps he could give Somerset permanent low tide for a few weeks. . Link to post Share on other sites More sharing options...
bike2steam Posted February 12, 2014 Share Posted February 12, 2014 Thanks for posting that, Paul. I was wondering what the situation would be like there. We once stopped off there to buy a wicker basket. As it happens, the business moved to Langport (I think) a few months or so ago, so I suspect that the building was empty. I haven't been there for a while, but I thought there were 2 other smaller businesses on that site. Link to post Share on other sites More sharing options...
jonny777 Posted February 12, 2014 Share Posted February 12, 2014 In modern society, if things go wrong, there has to be a scapegoat. If all the rivers, and drains, on the Somerset Levels had been dredged it still wouldn't have stopped all the flooding given the volume of water, personally I blame him up there- Big G, perhaps he could give Somerset permanent low tide for a few weeks. . Yes, and I agree that would be wonderful. However, I fear that with the spring equinox still to come, they have not had the highest tides yet. Presumably they will come in March? Link to post Share on other sites More sharing options...
Glorious NSE Posted February 12, 2014 Share Posted February 12, 2014 In modern society, if things go wrong, there has to be a scapegoat. If all the rivers, and drains, on the Somerset Levels had been dredged it still wouldn't have stopped all the flooding given the volume of water, I think an interesting question would be whether, if more action had been taken in December when flooding started, would it have been still in a heavily flooded state come February when the current series of storms hit? Link to post Share on other sites More sharing options...
station cat Posted February 12, 2014 Share Posted February 12, 2014 In modern society, if things go wrong, there has to be a scapegoat. If all the rivers, and drains, on the Somerset Levels had been dredged it still wouldn't have stopped all the flooding given the volume of water, personally I blame him up there- Big G, perhaps he could give Somerset permanent low tide for a few weeks. . Against which, had the dredging been carried out it would have taken far longer for the rivers/ditches to overflow and thus there would have been less flooding which would have been easier to manage. Link to post Share on other sites More sharing options...
jonny777 Posted February 12, 2014 Share Posted February 12, 2014 I think an interesting question would be whether, if more action had been taken in December when flooding started, would it have been still in a heavily flooded state come February when the current series of storms hit? Possibly, but from what I have read - the flooding in some areas has been deliberate, in order to protect the much more highly populated areas of Bridgwater and Taunton. Therefore the poor souls in rural areas have not stood a chance. An EA employee told me that for every millibar that the pressure falls below 1000, it adds a centimetre to the tidal water level (assuming the lowest pressure coincides with the high tide). This is before you add on the effects of swell and strong winds trying to force the water up the estuaries (again another coincidence event associated with position and severity of large low pressure areas out to the West). Comparisons have been made with the Fens, but unlike the rivers in the East, the Parrett appears to have no sluice gates/locks at the point near to where it meets the Bristol Channel, and the tide can just race inland for miles up the river. This seems like a recipe for disaster when most of the farmland on the Somerset Levels is below the height of the rivers. Link to post Share on other sites More sharing options...
MarkC Posted February 12, 2014 Share Posted February 12, 2014 Yes, and I agree that would be wonderful. However, I fear that with the spring equinox still to come, they have not had the highest tides yet. Presumably they will come in March? Ah, to clarify, "spring" tides happen every 28 days, as do "neap" tides. It's to do with the gravitational pull of the Moon. Link to post Share on other sites More sharing options...
jonny777 Posted February 12, 2014 Share Posted February 12, 2014 So I gather. But the gravitational pull of the Sun has to be added on, and around the Spring and Autumn equinoxes the Sun's component is at a maximum in this part of the world. Hence the spring tides are higher at those times of year than in mid-Winter or mid_Summer. Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted February 12, 2014 RMweb Gold Share Posted February 12, 2014 Flooding around the Athelney route has been commonplace for years and at times it could hinder road access making the pay round difficult and also make life difficult for the Signalmen getting there to work the 'box (which had to be manned as it also operated the level crossing). Thus there - in most respects - the arrival of resignalling solved our most likely and most common past problem. Like the captain I have never heard of either route being blocked by flooding although I think it might have come close to it on various occasions on the Athelney line. On the other line there really only used to be one regular spot for flooding and that was at Flax Bourton, much farther north of course and largely caused by water coming off adjacent fields and overpowering the track drainage. Flooding there was reportedly dealt with some years ago and the regular problem seems to have gone away. South of Bridgwater - as far as I know there has never been a flooding problem - what is happening there this year seems to be as much a consequence of the abrogation of managing what is basically a managed drainage area as it is a result of exceptional rainfall. The Levels are an area which over the centuries has been recovered from marshland and made productive with the use of managed water removal schemes involving sluices, drainage channels, pumping, and dredging and if taht long established process is not carried out the usual seasonal flooding will become far worse and potentially unmanageable. Add this year's exceptional rainfall to around a decade of non-management and you get what has now happened - with an important rail link to the West of England potentially closed for several months and traffic diverted onto a section, via Athelney, with long signal sections and thus limited capacity. As far as 'modern' signalling is concerned there is little that can be laid at its door in my view. Currently there is flooding in cutting between Maidenhead and Twyford massively reducing line capacity because track circuits have been knocked out and the signalling power supply is under threat (if not actually damaged by now). the water has come either from surface run off or possibly from a rising ground water (reports are unclear) but whichever it has crippled the signalling sysytem - for the first time in over 50 years since it was first installed, not a bad record. And of course if the signalling had been upgraded to the latest standards it might still be operation if the location cupboards and any cable joints were clear of the water. The biggest problem with really large control areas, coupled with other continuing manning economies of recent years, is the lack of people to put in 'stick & string' signalling to cover failures. Maidenhead Twyford is reportedly limited to 4 trains per hour at present and while there are obviously other factors such as flooded track and being able to put men on the ground in positions of safety the capacity which could be achieved in the manpower were available wouldn't be that much less than was possible in the distant past - but that means 4 men round the clock 7 days a week which creates a need for well over a dozen men doing little else until the floods subside. And it was bad enough finding that many men back in the '70s when the cabling was knocked out by a derailment. Link to post Share on other sites More sharing options...
Talltim Posted February 12, 2014 Share Posted February 12, 2014 I am reminded of Spirited Away Link to post Share on other sites More sharing options...
Rivercider Posted February 12, 2014 Share Posted February 12, 2014 Yes, and I agree that would be wonderful. However, I fear that with the spring equinox still to come, they have not had the highest tides yet. Presumably they will come in March? There were high tides in the Bristol Channel around the 2nd of february of about 13m, as MarkC says there is a 28 day cycle. The high tide levels forecast drop slightly to the 9th of feb, then rise to a middle peak around the 16th before dropping until the 23rd, they then rise again to the next high tides around 13m (edit - nearly 14m), on 2nd March. The River Tone is normally tidal to the New Bridge on Curry Moor, quite close to Cogload Junction, The River Parrett is normally tidal for about 2 miles south of Burrowbridge, where it joins the Tone, to Oath Lock, which is quite close to the B&H route to Castle Cary cheers Link to post Share on other sites More sharing options...
GordonC Posted February 12, 2014 Share Posted February 12, 2014 I have heard a lot about the pros and cons of dredging the various rivers, which apparently silt up over a period of time if left to their own devices. However, I have heard nothing about where this 'silt' originates? Obviously, it is from somewhere far upstream, but would it not be possible to try and discover who is losing all this stuff into the rivers in the first place and ask them to to do something about it? (As you can tell, I am not much of an expert on river management.) I think thats like telling farmers to stop their cows farting and contributing to global warming ... its a natural process as the river flows rather than someone dumping sand or soil into the rivers Link to post Share on other sites More sharing options...
eastwestdivide Posted February 12, 2014 Share Posted February 12, 2014 The normal upper reaches of tidal effects are marked on the OS maps - tidal parts of rivers are edged in black, the rest edged in blue. Link to Bing maps OS version showing Oath Lock, a heady 6 metres above sea level, and something like 10 miles inland. Link to post Share on other sites More sharing options...
Fat Controller Posted February 12, 2014 Share Posted February 12, 2014 I think thats like telling farmers to stop their cows farting and contributing to global warming ... its a natural process as the river flows rather than someone dumping sand or soil into the rivers The Nailbourne , the little stream that starts its route to the sea in our village, is normally a clear- running rivulet, normally perhaps six inches deep. Today, and for the last week or two, it has been in full spate, about 2' deep,, and is a dark brown colour. The colour comes from the tiny particles of soil eroded by the rain from the adjacent land; these will remain in suspension whilst the water is fairly fast-moving. Once the water slows down, however, these particles come out of suspension and precipitate as silt on the river bed. In slow-moving rivers, such as those of the Levels, much of this silt will end up on the river bed, further slowing down the flow, increasing the precipitation and so on. Eventually, the river becomes so silted that it becomes a viable habitat for water-tolerant plants, causing the reduction of flow to become even more marked. The silt is actually quite a useful resource, being full of nutrients, and can just be spread over the nearby fields after dredging. Link to post Share on other sites More sharing options...
RMweb Gold Captain Kernow Posted February 12, 2014 Author RMweb Gold Share Posted February 12, 2014 Like the captain I have never heard of either route being blocked by flooding although I think it might have come close to it on various occasions on the Athelney line. the water has come either from surface run off or possibly from a rising ground water (reports are unclear) In fact, the Athelney line has been closed due to flooding several times in recent winters. Sadly, I'm now just hearing that the water has risen there again, and it's been closed again. The problem at Maidenhead is understood to be rising ground water, rather than run-off. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted February 12, 2014 RMweb Gold Share Posted February 12, 2014 Ark Building for Dummies by Shawn Magill, on Flickr Andi Link to post Share on other sites More sharing options...
Fat Controller Posted February 12, 2014 Share Posted February 12, 2014 My maternal grandfather's ancestors were from Huish Episcopi, outside Langport; they moved to Wales for the weather... Link to post Share on other sites More sharing options...
Southernman46 Posted February 12, 2014 Share Posted February 12, 2014 Well, we're getting flooding (albeit no where near as severe but still getting into the properties) in the villages up on Salisbury Plain - Shrewton, Tilshead etc............and that's on a large high dome of porous chalk, the water courses just can't cope and the volume of water actually in the ground (Tilshead is the site of a monitored borehole) is showing that even up here the ground is now completely saturated - it's going to take weeks for it for drain away even after it stops raining. Link to post Share on other sites More sharing options...
RMweb Gold Oldddudders Posted February 12, 2014 RMweb Gold Share Posted February 12, 2014 they have not had the highest tides yet. Presumably they will come in March? "Beware the tides of March!" I'm sure someone famous said something like that..... Link to post Share on other sites More sharing options...
Coombe Barton Posted February 12, 2014 Share Posted February 12, 2014 Well, we're getting flooding (albeit no where near as severe but still getting into the properties) in the villages up on Salisbury Plain - Shrewton, Tilshead etc............and that's on a large high dome of porous chalk, the water courses just can't cope and the volume of water actually in the ground (Tilshead is the site of a monitored borehole) is showing that even up here the ground is now completely saturated - it's going to take weeks for it for drain away even after it stops raining. Borehole/Water Table data on this page - bottom map http://www.bbc.co.uk/news/uk-26127121 Link to post Share on other sites More sharing options...
Mod6 Posted February 12, 2014 Share Posted February 12, 2014 Like the Dawlish topic, let's try and keep vaguely on topic please. A bit of flippancy is one thing, but let's not let it take over and distract from the valuable information that Captain Kernow is kindly providing when he already has enough on his plate. I've deleted a few posts. Link to post Share on other sites More sharing options...
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