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Dredging will save more than it costs


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.

Posted date

8 February, 2014

Posted time

9:23 pm