Rivers overflowing

Would it help if rivers were dredged? They nust silt up over the years and then when there is a high rainfall they don't have the capacity. The solution always seems to be based around raising the banks.

John

Reply to
john
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It seems a silly idea to build houses near to where rivers flow/ed.

Reply to
Frank Erskine

Dredging estuaries is easy, they just take the silt out to the sea and dump it on an outgoing tide. Upstream it is difficult. And where is the silt going to go around Northampton? Dredging has to be done regularly, but walls only once and some maintenance after.

Reply to
Doctor Drivel

Neither is a good solution. Both hurry the water downstream and that makes flooding worse. The best idea is to trap the water as far upstream as possible and let it trickle out slowly. River dredging, bank heightening, bank strengthening, and river straightening are all counter-productive as they all require future intervention. Of course trapping the water up stream also requires constant intervention but that can be done free of charge as long as you get the right workforce* on the job.

Of course it also means that you cannot build on the floodplain unless you're building higher than likely future floods.

*Castor fiber - go on look it up! ;-)
Reply to
John Cartmell

Dredging tends to move the flood problem to a point further downstream where they haven't dredged because they never needed to previously. The best flood defence is to build 1,000's of new homes on the flood plain as these are the most effective way to break the force of the water and slow it down.

bland

Reply to
bland

The only real solution is to avoid building on flood plains, or get used to houses on stilts and occasionally commuting by boat.

Reply to
Rob Morley

I used to go to a bungalow in low lying land where the occupant had inventively built a 2 foot berm all around the dwelling. It was strange to drive over the hump into the garden but it kept him dry when things flooded all around him. for about two weeks. (With a bit of pumping as required from a deliberate low sump point within the defended area)

Reply to
John

| I used to go to a bungalow in low lying land where the occupant had | inventively built a 2 foot berm all around the dwelling. It was strange to | drive over the hump into the garden but it kept him dry when things flooded | all around him. for about two weeks. (With a bit of pumping as required from | a deliberate low sump point within the defended area)

The Germans have done that massively on the banks of the Rhine. I stayed on a camp site on the river side of the 8ft high embankment. The Electrical equipment was 20 ft above the ground.

Reply to
Dave Fawthrop

They get over that now by building "town houses"

:¬)

funilly enough, on the same subject, the latest development round Portishead (on the marsh/swamp land) have a new take on Town houses. To keep houses right up close to the foot path, they build a garage with no back on it so your drive is now in the back garden !

Reply to
PeTe33

At low river levels you can see all sorts of obstuctions - particularly near to bridges. When there are floods it is often such stuff - along with trees that ends up blocking bridges.

Reply to
john

They used to do just that round our way 20 or so years ago.

Now, they don't seem to bother.

sponix

Reply to
sPoNiX

In message , John Cartmell writes

There has been some *learning* within drainage authorities over the past

60 years. Simply moving the water on by canalising merely hastens the downstream problem. In our case (upper Lea) there are blockable road bridges which would encourage the flooding of water meadows if development didn't force clearance at the first hint of a spate. Rubbish is returned to the river and blocks the next bridge in the sequence.....

Dredging firms up and raises the banks due to the disposal of gravels and silt. The riparian owner is reluctant to have such material spread evenly over his field.

What seems to have been learned is that slowing water flow by deepening leads to silting and a re-cycling of the problem. Pressure from fishing interests to deepen the water has had to be balanced by artificial chicanes to keep the silt moving.

Hmm.. The TV presentation of the current release of European Beavers implied that they are not destructive and do not build dams but I may have misheard:-)

I have never understood why planners are so reluctant to permit development on valley slopes. I can see that the best land and availability of water power would make valley bottoms attractive to the first arrivals which means that development envelopes enclose the area most likely to flood. Surely development can be made visually attractive and we can move on from the *green and pleasant land* pretence; until you drive over the next hill. Hill top developments here tend to be unattractive cramped social housing because these are the only schemes able to get planning consent under the exception rules.

regards

Reply to
Tim Lamb

That reminds me when I was in Worth-am-Mein near Frankfurt a few years ago. The old town hall has permanent records on its side wall of how high the floods got, going back centuries. The highest was about 12 feet up, and given the ground was 12 feet up from the normal river, that is a 24 foot flood. Didn't seem to bother them too much.

bland

Reply to
bland

They are not destructive but they do build dams. Their usefulness is in the dams that hold the water giving it time to soak into the ground and re-appear on the surface lower down the valley after (or long after) the first rush of a storm. Rather than destroying great swathes of woodland Castor fiber manage it to the benefit of both the vegetation and other animals. There really isn't a downside and their absence has caused many problems for us over the years.

Re-introductions of C. fiber to western Europe have taken place over the years (from memory since the 50s?) with little or no problem.

My daughter studied the proposals for re-introduction for her MSc and was

*very* sceptical from the start. She is particularly scathing about the mess made in introduction of European animals in Australia but ended up supporting the proposed C. fiber project considering it only too little, too late, and why only Scotland?
Reply to
John Cartmell

No, you might go too deep and pull the plug out *

[*] it actually happened on the Chesterfield canal a few years ago
Reply to
Matt

Its more cost effective to dredge the rivers.

-- Sir Benjamin Middlethwaite

Reply to
The3rd Earl Of Derby

.........and on the Gloucester-Sharpness canal.

Reply to
Tony Williams

Some people are putting polystyrene rafts under their holiday caravans, so they float in the event of flodding.

Owain

Reply to
Owain

I hope they've anchors on, as well.

Reply to
Set Square

I hadn't thought of them like that before, but you're right.

They're getting closer to the stilts model. :-)

Reply to
Rob Morley

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