Dredging

[Anderoo]

In the aftermath of these recent floods there's a lot of talk about dredging rivers - mostly angry demands from people affected by the floods, claiming that if the EA dredge the rivers the floods would either not have happened or would not have been so bad.

 

The EA are on radio 4 at the moment discussing this (in reference to the Somerset levels) saying that dredging could be part of a package of solutions to be implemented.

 

I'm sure we've all seen the aftermath of badly executed dredging in the past. Should we be worried about this? Are rivers now just thought of as drainage ditches rather than natural habitats?

Edited January 28, 2014 by Anderoo

[chesters1]

Its not the depth of the rivers that make a difference i expect.

We flood here several times a year and i have noticed if the river floods at elstead downstream it starts to flood here ,the problem appears to be bridges ,we have many here most built by monks so they are pretty small arched jobbies and when the water rises beyond a certain point it gets slower going through the bridge (the gap in the arch is smaller at the top)

The river then slows right down and floods all the way up the valley on the floodplains slowing the river so eventually our bridge becomes the choke point and then it floods upstream.

The EA's solution was to raise the bank at elstead stopping the road flooding but it doesnt work the river just gets higher and goes round it even slower making it worse.

So i think dredging isnt the solution ,obstructions are the problem

 

We (man) tend to do things we think benefit us ,in the past the upper wey has had water shortages so several sluices exist on it ,this artificially slows water

I noticed the one at waverly abbey in the summer when the levels drop has only a foot of water but a 8ft thick bed of silt ,had the sluice not existed the bed of the river would scour itself out and become deeper ,all the mills on the wey also now do not work so the rivers man made bypasses around the sluices are long silted up ,trouble is compared to the past we know nothing about water management

Its pointless making water go faster downstream through dredging unless the bankd are higher than upstream ,it just makes flooding faster at the first place the water can escape the river ,thats why flood plains exist ,if you respected them the water is happy to sit on them waiting to go downstream at its leisure

The Somerset levels were for thousands of years marshes ,they wernt marshes just to be annoying they are artificially drained and nature tends to reclaim things naturally

One day nature will get its revenge on holland and man will suffer untold amounts when it does ,time will tell

Edited January 28, 2014 by chesters1

[Dales]

I doubt there is enough money for dredging but if enough pressure is applied in some area they may well get their local river dredged to show the EA is actually doing something. I guess it is a lottery as to wins and who loses if it happens in your area. I just don't see enough cash in the system for any major increase in works to river management.

[RUDD]

Cant see dredging making much difference the whole of the Somerset levels is a natural floodplain surronded by hills.

Simple solution as has been said time and time again, plant more trees!

 

Its an interesting place:

 

http://en.wikipedia.org/wiki/Somerset_Levels

[gozzer]

No, dredging isn't the whole solution. I've seen the chaos caused back in the 60s and 70s on the Yorks Wharfe. Dredged, straightened, and 45 degree banks, made it no good for fish, wildlife, or drainage, it just pushed the water through faster, and moved the flooding downstream until it backed up, and flooded the place they were trying to protect in the first place. This dredging coincided with peat digging higher up the river, and ensured that water came of the moors faster to add to the problem. There's another thread about this in the conservation section, ( http://www.anglersnet.co.uk/forums/index.php?/topic/5479499-we-want-it-dredged/ ), and Steve posted a very good report on there, I recommend people read it. It shows that the 'problem' is more complex than many realise. It's not just a case of trying to contain the water, there are a whole gamut of things to take into consideration, especially where peat marshes are concerned.

Making a river a few feet deeper is not going to accommodate much extra water, widening the river will regulate the flow much better. Ah, but doesn't nature already have that in hand? Something called a floodplain.

 

John.

Edited January 28, 2014 by gozzer

[Anderoo]

http://www.theguardian.com/environment/2014/jan/28/dredging-rivers-flooding-environment-agency-somerset

 

Some good comments here, and in the article above. Luckily it seems that most people now realise dredging rivers is not the answer.

[BoldBear]

I do feel sorry for the people that have had their property and livelihood flooded but on the other hand surely they must realise that it is a risk that they themselves took in the first place by choosing to live in the middle of a flood plain; and turning our rivers into drains is just not and never has been the answer.

 

I would like to see the smaller fields; that we used to have; come back with rows of trees and hedgerows surrounding them, and if people must live on a flood plain then they should build their property on higher ground or on stilts and learn to expect the occasional flood and hopefully be a little better prepared.

 

Keith (BoldBear)

Edited January 28, 2014 by BoldBear

[Rice Crackers]

I've worked on the design of a development next to the River Lea and the EA guidance was clear: The ground floor level must be above the 100 year floor level plus an extra percentage to allow for climate change. It is not acceptable put up a huge flood defence wall. Water must be allowed to enter the flood plain. Flood walls simply exacerbate the flooding in other areas. Houses that are placed in flood plains must have a design that allows their lower level 'i.e. the void beneath ground floor' to flood too. Any new development that reduces the capacity of the flood plain to store water will be rejected.

 

The EA realise we can't keep building on flood plains, the problem is that too many developments are already there. In such a densely-populated country and with such unscrupulous developers and easily-influenced councillors (believe me I know) there has been huge pressure to build on the plains and up until relatively recently it wasn't properly resisted. That, not dredging rivers, is the problem.

 

Like all major political decisions made in this country, those who made them (i.e local councillors, their advisors and the developers that probably paid them all off) are never held accountable and we now have an impossible problem whereby many developments of hundreds of houses are uninsurable and prone to being wrecked every few years. The simple answer - huge flood walls - isn't acceptable. Dredging is also a nonsense answer. The rivers have worked just fine for thousands of years without dredging because they had flood plains to take up their extra capacity when needed so why should we now dredge rivers to spare houses that have no business being on flood plains in the first place. I can understand someone whose been ankle-deep in water for the past two weeks thinking it's the answer but in the cold light of day it isn't.

 

The moral of this story is don't mess with nature

[Steve Walker]

The moral of this story is don't mess with nature

"Damn nature, you scary"

 

 

[grayson]

The problem we have is a hysteria by the uninformed public that dredging is the answer and a rural myth that way back when all rivers were dredged. No they weren't- in the area I live (Yorkshire ) only the navigable rivers , a tiny proportion of the whole system was ever dredged and that was of dubious effect. I remember one huge flood in the 60s when a coal barge ended up in a field 400 yards away from the river Aire . I have seen at first hand the appalling vandalism carried out by Internal Drainage Boards on local streams - which are still regularly 'maintained ' and it would make any fisherman weep. Disgusting grubbing out of bed, ripping out of trees(meaning bank collapsed and more work doing to shore it up) and if it achieved anything all it did was speed the passage of flood water to the nearest pinch point - the local town. And the same bastards who run the IDBs (farmers) then whinge about needing to abstract more in times of low flow . I had a letter published in Trout and Salmon to this effect and Charles Rangeley Wilson has recently had one in the Time to similar effect. Some farmers are great when it comes to managing agriculture with the environment - sadly they are in a minority. I heard one NFU bigwig demanding that the Ure, Swale, Ouse and Derwent be dredged from source to the sea and I felt like thumping him ....Guardians of our environment - my arse they are.