Another series of lows and Storm Dennis

[tree monkey]

Just now, magpie patrick said:

Trees on the catchment is one thing

 

Trees in the river is quite another

Does it not depend on the waterway, a river with natural meanders is different from a river adapted for drainage

[magpie patrick]

1 minute ago, tree monkey said:

Does it not depend on the waterway, a river with natural meanders is different from a river adapted for drainage

Well clearly there are nuances, it's just there is a danger of the argument on trees going the way of the argument on dredging - a tit for tat between they're good and they're not

 

If you allow a grassy (or even concreted) catchment to become wooded, it will hold back run off which is good

 

If you allow trees to grow and flourish on the margins (or even in) a river you rely on for conveyance they will inhibit that conveyance, which if you're immediately upstream is not so good

 

A lot of it is about accepting that these environments have been modified by human activity, not just changing the plan. I have been and am still involved on occasion involved in river management and flood risk alleviation - it's a bit of a dark art and it needs skilled planning and a lot of resource to get it right, or rather, to get it as right as one can. 

[Mike Todd]

7 hours ago, Athy said:

It would surely make a difference to navigation, on which PB was commenting.

Post 151 seems to suggest that PeterBoat believes that dredging will help combat flooding - despite all the experts saying otherwise.

 

I suspect that there is a dependency on the ration between the capacity of the river and the amount of flood water. At one extreme, no depth at all will mean that almost any flood water will spread out from the 'banks' whilst at the other end, dredging will clearly not help if the amount of flood water simply overwhelms the river valley or if the river downstream does not have additional capacity. Real knowledge, as distinct from anecdote and guesswork, will be needed to determine which is the case in specific places. I suspect that some of the flood schemes are political decisions rather than well-considered technical solutions. It cannot help that there are so many drainage bodies.

 

 

Edited February 24, 2020 by Mike Todd

[matty40s]

4 hours ago, Markinaboat said:

Be careful you don't trip down those steps at your time of life Matty! ?

...another good thing about Barcelona is that it seems to have escalators up all the steps and cable cars down.

Slumming it this afternoon, cant get away from the sodding widebeams though.

[Richard T]

On 22/02/2020 at 11:59, Richard T said:

Boat beached at Trent Lock. I could see that this was going to happen from the train the other day. It will be difficult to refloat as crane access is very limited and on saturated fields

This boat is now back in the water thanks to the river levels rising again!! The owner needs to be thankful for that. It now has at least one pole to stop it going back from whence it came.

[Athy]

4 minutes ago, Mike Todd said:

Post 151 seems to suggest that PeterBoat believes that dredging will help combat flooding - despite all the experts saying otherwise.

 

 

Quite possibly, but that was not the post to which I was referring.

[Mike Todd]

4 minutes ago, matty40s said:

...another good thing about Barcelona is that it seems to have escalators up all the steps and cable cars down.

Slumming it this afternoon, cant get away from the sodding widebeams though.

Now that's a real wide beam!

[tree monkey]

2 minutes ago, magpie patrick said:

Well clearly there are nuances, it's just there is a danger of the argument on trees going the way of the argument on dredging - a tit for tat between they're good and they're not

 

If you allow a grassy (or even concreted) catchment to become wooded, it will hold back run off which is good

 

If you allow trees to grow and flourish on the margins (or even in) a river you rely on for conveyance they will inhibit that conveyance, which if you're immediately upstream is not so good

 

A lot of it is about accepting that these environments have been modified by human activity, not just changing the plan. I have been and am still involved on occasion involved in river management and flood risk alleviation - it's a bit of a dark art and it needs skilled planning and a lot of resource to get it right, or rather, to get it as right as one can. 

Interesting thank you, it always worries me when people look for a single answer to complex questions, the understandable cry for dredging could easily become dredging good trees bad.

 

It's a difficult balance to achieve and as you say, so much or even all of our environment has been modified to some degree by human activity, its knowing and understanding when to continue the management or stop that management 

 

It's a complex subject and I don't envy the various bodies responsible 

[Mike Todd]

6 minutes ago, tree monkey said:

Interesting thank you, it always worries me when people look for a single answer to complex questions, the understandable cry for dredging could easily become dredging good trees bad.

 

It's a difficult balance to achieve and as you say, so much or even all of our environment has been modified to some degree by human activity, its knowing and understanding when to continue the management or stop that management 

 

It's a complex subject and I don't envy the various bodies responsible 

But on another thread, trees = good (carbon capture) whilst dredging = bad (release of noxious stuff from the river/canal bed) . . . 

[Graham Davis]

33 minutes ago, magpie patrick said:

Well clearly there are nuances, it's just there is a danger of the argument on trees going the way of the argument on dredging - a tit for tat between they're good and they're not

 

If you allow a grassy (or even concreted) catchment to become wooded, it will hold back run off which is good

 

If you allow trees to grow and flourish on the margins (or even in) a river you rely on for conveyance they will inhibit that conveyance, which if you're immediately upstream is not so good

 

A lot of it is about accepting that these environments have been modified by human activity, not just changing the plan. I have been and am still involved on occasion involved in river management and flood risk alleviation - it's a bit of a dark art and it needs skilled planning and a lot of resource to get it right, or rather, to get it as right as one can. 

Peterboat needs to read all the words above, especially the last part and stop trying to be an armchair expert.

[tree monkey]

25 minutes ago, Mike Todd said:

But on another thread, trees = good (carbon capture) whilst dredging = bad (release of noxious stuff from the river/canal bed) . . . 

Which is the point I suppose, there is rarely 1 blanket answer, its complex.

 

A very very simple example is the recent news story of Nestle planting trees (yay) on a species rich wildflower meadow (boo), complex problems require very complex answers

[mrsmelly]

The Aire and Ouse have flooded big time at the back of my sisters house not far from Selby. A19 and lots of local roads closed with her house perilously close to the river bank that is in danger of collapsing. Took me an hour to get there from the other house instead of twenty minutes today. She wasnt too impressed when I told her how stupid houses were as they are attached to the ground and my boat simply rises with the levels.

[WotEver]

On the ITV news tonight they claimed that 500 tonnes of water a minute was flowing through Shrewsbury town centre. And a further 500mm rise expected overnight. I don’t think dredging would have much impact on that. 

9 minutes ago, mrsmelly said:

She wasnt too impressed when I told her how stupid houses were as they are attached to the ground and my boat simply rises with the levels.

You could always try unattaching it and seeing if it wants to float...

[Graham Davis]

The situation in Shrewsbury is frightening.
 

[Naughty Cal]

1 hour ago, WotEver said:

On the ITV news tonight they claimed that 500 tonnes of water a minute was flowing through Shrewsbury town centre. And a further 500mm rise expected overnight. I don’t think dredging would have much impact on that. 

You could always try unattaching it and seeing if it wants to float...

No amount of dredging and cutting down trees would have stopped the level and extent of flooding experienced this winter.

 

It has been an exceptionally wet winter with back to back heavy rainfall events. 

 

You can't dredge river channels to cope with this amount of water.

[Mike Todd]

2 hours ago, mrsmelly said:

The Aire and Ouse have flooded big time at the back of my sisters house not far from Selby. A19 and lots of local roads closed with her house perilously close to the river bank that is in danger of collapsing. Took me an hour to get there from the other house instead of twenty minutes today. She wasnt too impressed when I told her how stupid houses were as they are attached to the ground and my boat simply rises with the levels.

On the radio earlier an architect was talking about a novel house design which also rises with the water level and which is being offered as one option to allow the government to change building regs for properties in flood risk ares.

[Tonka]

9 minutes ago, Mike Todd said:

On the radio earlier an architect was talking about a novel house design which also rises with the water level and which is being offered as one option to allow the government to change building regs for properties in flood risk ares.

it is called a houseboat

[ditchcrawler]

26 minutes ago, Mike Todd said:

On the radio earlier an architect was talking about a novel house design which also rises with the water level and which is being offered as one option to allow the government to change building regs for properties in flood risk ares.

There is on on the Thames    

 

Edited February 24, 2020 by ditchcrawler

[TheBiscuits]

1 hour ago, Mike Todd said:

On the radio earlier an architect was talking about a novel house design which also rises with the water level and which is being offered as one option to allow the government to change building regs for properties in flood risk ares.

It would be far simpler to require the housebuilders to underwrite flood insurance for all their new builds ... and backdate it 10 years or so!

 

 

[Mike Todd]

11 hours ago, ditchcrawler said:

There is on on the Thames    

 

That's the one being discussed, I believe. Claimed to be a success over the past flood period.

[magpie patrick]

15 hours ago, Naughty Cal said:

No amount of dredging and cutting down trees would have stopped the level and extent of flooding experienced this winter.

 

It has been an exceptionally wet winter with back to back heavy rainfall events. 

 

You can't dredge river channels to cope with this amount of water.

That used to be thought to be the case in Bath, but an extensive flood risk alleviation programme implemented in the 1970's has meant the city centre has been free of floods for nearly fifty years, and in the recent heavy rains whilst moorings and walkways have gone under water nothing of significant has flooded. However one needs to understand just how extensive and comprehensive those works are. They consist of

 

• Excavating the river through the city to a 20m wide by 4m deep channel in a rectangular section i.e. its over 12 feet deep at the sides and never less than sixty feet wide (far deeper than historic dredging)
• Automatic sluice gates at Pulteney Weir (head of navigation) and Twerton Weir (Weston Lock)
• Ensuring nothing is built on the water meadows/flood plain above and below the city 

 

I've seen record floods at Dundas (green fields - no harm done) and Claverton Pump House go under water and yet the city centre hasn't flooded - this winter the local paper carried headlines along the lines of "the meadows that saved the city" with pictures of the meadows in Bathampton under water. 

 

If they ever stop maintaining this system then the centre of Bath may well go under water again, or at least the Avon Street area (known as "The Hate" in the arly 19th century - it was always a bit damp) and Lower Bristol Road will. A few years ago the EA said the Pulteney Gate wasn't necessary (not renewing it would save a couple of million pounds) - it's been fully open at least four times this winter

 

So you can engineer your way out of floods, but it's expensive, and to work one must maintain the works and and must not built on your flood storage: if Bathampton Meadows were developed and then needed flood defences it would screw the system. 

 

If you're going to tackle flooding you can't rely on simplistic solutions - and you need to listen to the history of the area and build on it

Edited February 25, 2020 by magpie patrick

[Tonka]

They have stopped flooding the posh houses on the Thames by engineering and built the jubilee river. Only problem the poor people of Datchet and Chertsey get flooded now because the water gets there faster

[Nightwatch]

From my simple mind.

Are we having more rain than in the past or are we just not coping as well with it. It has been well understood that we have been building on ‘natural’ flood plains for years. If we are to do this should we have not created alternative routes for rain water to disperse?

 

If you have a half inflated balloon and you squeeze the air out of one bit, the air comes out at another point. Is this not the same principle? Same amount of water will find its way somewhere else. 

 

(To use up all this excess water maybe we ought to brew more beer. Then all the fluids will go down the loo and find it’s own way of dispersal. Nor would we worry so much about flooding having drunk all the water in another form. )
 

  

Edited February 25, 2020 by Nightwatch

[Graham Davis]

For the first time in living memory they have had to close all the rail lines into Shrewsbury station, which is partly built on a viaduct over the Severn, due to the height of the flooding. So that's trains to South Wales, Aberystwyth, Chester, Crewe and Birmingham. 

Severn at Iron Bridge is now expected to overtop the flood defences.

Worcester City Centre being closed down with numerous roads closed, and the full effects are not expected to reach there until tomorrow.

And now it is snowing up here, and the mountain road to Machynlleth has been closed. 
 

Edited February 25, 2020 by Graham Davis

[peterboat]

1 hour ago, Graham Davis said:

For the first time in living memory they have had to close all the rail lines into Shrewsbury station, which is partly built on a viaduct over the Severn, due to the height of the flooding. So that's trains to South Wales, Aberystwyth, Chester, Crewe and Birmingham. 

Severn at Iron Bridge is now expected to overtop the flood defences.

Worcester City Centre being closed down with numerous roads closed, and the full effects are not expected to reach there until tomorrow.

And now it is snowing up here, and the mountain road to Machynlleth has been closed. 
 

Non of this is good news the rivers here are still up but whats happening there is an ongoing disaster! I am sure I read somewhere that the river seven had been narrowed at a point for some reason, is this along with the continuous rain maybe an issue? will google it as I am curious if I am remembering wrong