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Dredging will save more than it costs

Ian Liddell-Grainger

Get yourself a bottle of cola, pour the contents into a jug, re-fill the bottle half way with sand and - surprise surprise - when you try and put the cola back in there is no longer enough room. It overflows!

This is exactly what has happened to the two main rivers in my constituency. It happened last year, and the year before too. It has far less to do with climate change than negligent river management. It will happen again and again and again unless we learn the lessons.

The Parrett and Tone rivers flow into the Bristol Channel. They have not been properly dredged for 20 years - ever since the useless Environment Agency was created. As a result they cannot cope with persistent rain, and the whole area of Sedgemoor floods.

Right now thousands of acres are waterlogged, hundreds of people have abandoned their homes, roads are shut and the army is preparing to move in. The Environment Agency’s inadequate pumps are failing to shift enough water and people like me are desperately seeking real help from real experts.

I have been in Strasbourg this week discussing precisely what is needed with my counterparts from Holland. They use far bigger pumps, versatile dredgers, and imaginative engineering. No doubt we Brits are just as capable of making such things, but there isn’t a market for sensible solutions with the Environment Agency in charge.

Why won’t they dredge? Because they don’t like scooping out the silt and building up the banks of the river. They say it costs too much. They would rather see Mother Nature do her worst. The Dutch use dredged silt to build up their own river banks. The Environment Agency believes that silt is a pollutant and heaven forfend that any should be used in this way.

Even in the midst of the current crisis, with the prime minister promising that dredging will soon be undertaken, I am told that the Environment Agency is still bleating to the government that it does not want to use dredgers because it might upset the elver population. Somerset may drown to protect little eels!

Much of Holland is below sea level all the time, but ever since a disastrous flood in 1953 they’ve invested in the very best prevention methods.

Left to the Environment Agency the Netherlands would become the Neverlands. This British quango has lost the confidence of my constituents by losing the plot

The cost of the Somerset clean-up will greatly exceed the price of dredging.

It is about time we learned from the Dutch. Prevention is better than cure.

  • Ian Liddell-Grainger is the MP for Bridgwater

Readers' comments (8)

  • NCE what are we doing letting MP's have a say in this way? We all know they have alternative motives and will say whatever they think is most popular.
    I work for a nationwide contractor and we have to move heaven and earth to deal with environmental issues most of which I agree with. We spend so much money during projects to look after and improve our environment. This MP wants to undo all of that because he is getting some pressure from locals residents who live on a flood plain and are surprised, when we have the wettest winter on record, that they get flooded. This is stupidity at its utmost and a typical knee-jerk reaction from an MP. Mark Hansord sums it up beautifully in this week’s opening comment.

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  • Very disappointed that the NCE dedicated a whole page of opinion to an MP. This is meant to be a page of expert opinion on a topic not a non-expert's rant. As Mark Hansford said "Engineering judgement please, not political hysteria" why give so much space to political hysteria??

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  • I cannot agree more with the first two comments. What is such an ill-informed political rant doing on the pages of a respectable professional journal?

    And as for the ridiculous analogy: get yourself a bottle of cola, pour the contents into a jug, refill the bottle half way with sand and - surprise surprise - when you try and pour twenty bottles worth of cola into the bottle it overflows!

    How about this one: increase the depth of a 10m wide river by 2m (by dredging) over a length of 10km (for example). The increase in storage volume is 200,000 cubic metres. Spread that over 65 square kilometres and you get a reduction in flood level of 3mm (the whole picture is of course a little bit more complicated than that, but then analogies often are).

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  • I strongly support the views of the MP for Bridgewater, and disagree equally strongly with several aspects of the above 3 comments. To call Mr Graingers article a 'rant' and 'stupidity at its utmost' is hardly a example of 'expert opinion'. An MP coming out in favour of his constituents when they are in dire trouble is labelled as 'a knee jerk reaction'.
    CB thinks the people who live on the levels are 'stupid' because apparently, according to him, they are surprised when they are flooded. They have lived for more than 100 years with flooding from time to time and are used to coping, but this is different. The length of time which the water has been on the land is now 5 weeks and counting. The original drains before they were allowed to silt up cleared the grassland of water in 5 days. This is crucial if long term damage to the Environment is to be avoided. CB please note, more damage done to Environment if drainage not maintained. Also, no Badgers now on the Levels, all drowned!
    MW please note, I have yet to see any Engineering judgement, especially from Mark Hansford who is a journalist, apart from the ex President of the Institution of Civil Engineers who of course favours dredging. As for the comment of RH! This displays a truly abject ignorance of hydraulic engineering. How about this one RH: you don't seem to be able to distinguish between a flood storage facility and a river whose whole function is to convey water. If you dredge the river it increase its CARRYING CAPACITY. As a good rough guide if you double the CSA you will double its ability to get rid of flood water and halve the time that the water lies on the land. Crucially,you must be able to take advantage of the Tidal cycle and the carrying capacity is absolutely vital if you are to get rid of more water than is reaching the Levels each cycle. This used to be the case before the Agency got rid of its plant for its scrap value in the 1990s.

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  • This debate has become largely pointless. The only valuable opinions about the merits of dredging are those of experts in the subject. Even so they must be experts without any motivation except to tell the truth. This obviously excludes politicians, contractors and consultants in this field etc. Opinions of residents of flooded areas who are also experts would be very interesting.
    I live a long way off, am retired and support Mark Hansford's opinion.

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  • I am always genuinely surprised that so many of these discussions end up with people insulting contributors, just because they disagree with them. MS: you appear to have made a judgement about me on the basis of a fairly brief contribution, without actually knowing anything about me.
    I made it quite clear that the real picture is more complicated than what can be covered by analogies. The fact is that Mr Liddell-Grainger’s analogy deals with volume of water, so I chose one that also deals in volumes of water, but (in my opinion) provides a more scientific assessment of the impact of dredging on the water level. The irony is that if you think my analogy proves my truly abject ignorance of hydraulic engineering then the same must go for the analogy suggested by Mr Liddell-Grainger, so you’re just proving my point really.
    You are absolutely right that dredging will result in an increase in carrying capacity, but just like me, for the sake of brevity, you have left out some pretty important details. For example, an increased carrying capacity will only be achieved in the dredged area. Further downstream the effect could quite possibly be flooding of areas that are currently unaffected, including Bridgewater itself. Or are you suggesting that the river be dredged all the way to sea? The fact is that this has been tried, and it does not work (not with an acceptable benefit cost ration anyway). That is why they stopped doing it.
    Perhaps you could provide some additional information on your proposal:
    Over what length would you dredge?
    To what depth would you dredge?
    How would you deal with pinch points, which result in a reduction of the cross sectional area of the channel, and therefore have the potential to cause flooding in those areas?
    How often will you have to dredge?
    How much will it cost?
    What is the benefit cost ratio?
    What is the priority score?
    As for calling Mr Liddell-Grainger’s contribution a rant, I would have had no objection if he had stuck to the facts, or had been more diplomatic in stating his opinion. But making insulting comments is not appropriate, and I am surprised that a Member of Parliament would express himself in such a way.
    The Environment Agency (and NCE) has plenty of experts that it can consult with, and those experts appear to agree that dredging is not the answer. Mr Liddell-Grainger may have other ideas, but that is no reason for him (or you) to insult others.

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  • Last fortnight Bernard Ingham let loose on climate change and sustainable energy policy, and this week Ian Liddell-Grainger follows suit on the EA and flooding. At the same time NCE Editor Mark Hansford calls for "engineering judgement, not political hysteria" and Ben Mitchell points out that civil engineers must express "passionate views" and "stand up for their beliefs". Cue shock from subscribing civil engineers who do not expect to see politicians openly attacking, with sometimes questionable rhetoric, key civils industry sectors in their own magazine. Perhaps the NCE editorship is trying to subtly point out, via juxtaposition, the gulf between the actual decision makers and the engineers who should be informing them? If this is the case, then fine, but I would rather see NCE making a rather less tacitly critical position. I would expect some active critique of political arguments apparently based in generalities and name-calling. Equally, NCE needs to ask why the civil engeering profession itself has failed, for decades it seems, to position itself as a "voice of reason" at the heart of these issues, rather than waiting on the outside of the debate, looking in and muttering about what a hash economists, politicians and others make of engineering issues, and how little the engineers are paid in comparison, dispite the critical importance of their role to the safe and efficiently delivery of infrastructure projects and to the wider economy.

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  • I have just been hearing Mr Camerons latest sound bite on the subject of flooding (visiting Dorset on Monday 10th February). In summary he says he has done EVERYTHING possible to alleviate the flooding; provided pumps, mobilised the army, declared an emergency!
    Well Mr Cameron, I am truly impressed. What more could we expect you to do?
    The fact that none of these things are as effective as properly planned and funded flood prevention measures, such as the Boston tidal barrier, seems to have been missed by most people.
    Meanwhile I am heartened to see the professionals debate the issue with expert insight and technical knowledge.
    When are we going to face what we already know about politicians like Mr Cameron and Mr Liddell-Grainger; they just do and say what is popular at any given moment in time.
    Our job is to make the right decisions popular. We will not do that by debating the technical details in the pages of our own journal. We will achieve it by joining the debate in the wider press and keeping it simple.
    DREDGING DOESN'T WORK Mr Liddel Grainger!

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