The environment Agency claims that dredging rivers does not help to avoid floods.
I really don't understand - Water does not pile up - unless there are restrictions to the flow. How often do we see bridges - perhaps with 3 arches - but the two outer ones are slted up or full of debris. This cannot be acceptable.
If you dredge the water comes quicker from upstream, so builds up quicker at accumulation points because it arrives at a faster rate.
Dredging a section might well speed up flow through that part of the river. But that means the next section gets the water more quickly and it might not be able to cope.
The flooding of 2014, if I remember correctly, was at least moved by changes ot the Thames.
As others have said, speeding the flow to areas that can?t cope with it is one problem. The other is that dredged material is rarely taken away, it?s dumped on the river banks. If this is done repeatedly you end up with a river running in an elevated ?canal? completely above the surrounding land level.
A breech of the bank can lead to catastrophic local flooding.
Tim
They are of course lying. To cover their arses. Cummings should sack them.
The only thing you need to understand is that incompetent people lie to preserve their egos, their status and their jobs.
Poor old Pancho. That's why you START by dredging at the bottom - the estuary.
I cant believe you actually believe that.
But only if the level of water in the 'canal' gets above that of the surrounding countryside, which, if it does, would have been flooded anyway regardless of whether the banks had been artificially raised. In fact raising the banks will offer some degree of protection for the surrounding countryside, which it wouldn't have if they weren't there. It doesn't make things worse.
Of course. I used to live 6foot below the normal river level on the fens.
Never got flooded because they (a) dredged all the canals in east Anglia (b) have vast polders that they can release flood-water into to relieve the pressure on the rivers.
The ONLY real unplanned flooding happened in Cambridge and upstream outside the fen management area.
Water management is a very old and well understood set of techniques, that have been totally ignored by 'environmentalists' because they thought they knew better.
So, the NIMBY approach would be to want everything downstream of me thoroughly dredged, but nothing upstream of me?
I'd love to see some calculations that prove that dredging would have allowed those rivers to carry all the recent rain away safely.
And if you really did make them that deep, not much use for those who moor a boat at the bottom of their garden? Or commercial operators on the river? Others who use them for pleasure, etc?
Ah - your life story again.
In general the upstream part of a river is vulnerable to tree removal. Three lined valleys retain water better and release its slower. The middle sections are vulnerable and need flood plains to be available
- more than ever if they are down from valleys that have been logged. Further towards the estuaries the problem is capacity and dredging improves that massively. In general a river twice as deep can carry twice as much water.
Trees and flooding flood plains buffers: dredging improves flow.
It really is that simple.
Building banks higher also helps specific locations. And use of locks and flood barriers can control rates to below the maximum available on the dredged channel, but not above it.
No one actually bothers to study and understand this however. DEFRA is full of left wing politicians, not hydrologists
Anyway, whatever the cause the Aire has burst in bank at Snaith and there's a classic car garage flooded out.
Bill
Odd your pals the Tories allowed this after 10 years in power?
But perhaps only those committed to the environment can afford to work there after the severe budget cuts during austerity?
The actual claim is that it does not help prevent flooding *under extreme conditions*. This article, which addresses the same question after an earlier period of flooding explains the problem in detail:
It's embarrassing that the Romans probably had a better grasp of hydrology than our modern "experts". Or indeed our medieval forebears - in particular the monastic orders which were able to create and maintain complex fish lakes and water control for mills and industry. Something which is painfully obvious when you realise which bit of Tewkesbury never floods ...
And ironically managing vegetation with fire to prevent wildfires was also well understood by the indigenous people of Australia. Until we stopped them ...
One issue is that they attempt to keep water from going down too fast in case it floods areas that have high priced properties which might be vulnerable, but if they had not allowed building on flood plains in the first place they would not be in this mess. Brian
What's this 'we' business, white man? It's the Greens you're thinking of.
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