In an article entitled "Dredging rivers won't stop floods. It will make them worse", George is surprised to find the Environment agency agreeing with him. They have released a paper on dredging. In it they cleverly state that dredging is carried out "to improve navigation, by increasing depths and straightening channels or "to improve land drainage, particularly by creating artificial channels". So despite the fact that they state that "Dredging is the process of removing silt from the bottom and sides of the river channel", clearing silt from riverbeds and returning them to their original depth, the activity in which they have a twenty year backlog is obviously not dredging.
So, cheered by this unexpected help in his campaign that started with trying to get rid of sheep and seemingly unaware that the whole paper appears to be designed simply to justify the EA's inactivity in dredging over the last twenty years, George launches forth,
"A river's capacity is tiny by comparison to the catchment from which it draws its water. You can increase the flow of a river by dredging, but that is likely to cause faster and more dangerous floods downstream when the water hits the nearest urban bridge (something the residents of towns like Taunton and Bridgwater should be worried about). If you cut it off from its floodplain by turning it into a deep trench, you might raise its capacity from, say, 2% of the water moving through the catchment to 4%. You will have solved nothing while creating a host of new problems."
George, please look at a map of Somerset. Taunton is upstream of the floods. No-one is talking about dredging the Tone upstream of Taunton. The Parrett at Bridgwater is tidal, so at low tide, there is always going to be huge spare capacity in its channel. The burghers of Taunton and Bridgwater can sleep safe in their beds.
Next he posts a litany of excuses by the EA to do nothing:
"1. Massive expense. Once you have started dredging, "it must be repeated after every extreme flood, as the river silts up again".
2. More dangerous rivers: "Removing river bank vegetation such as trees and shrubs decreases bank stability and increases erosion and siltation."
3. The destabilisation of bridges, weirs, culverts and river walls, whose foundations are undermined by deepening the channel: "If the river channels are dredged and structures are not realigned, 'Pinch Points' at structures would occur. This would increase the risk of flooding at the structure." That means more expense and more danger.
4. Destruction of the natural world: "Removing gravel from river beds by dredging leads to the loss of spawning grounds for fish, and can cause loss of some species. Removing river bank soils disturbs the habitat of river bank fauna such as otters and water voles."
1. Dredging started in the C18th. The EA isn't being asked to start dredging, it's being asked to continue dredging. All the rivers draining the Somerset Levels run in man-made channels. No-one is talking about widening them or deepening them. All the residents of the levels want is for the twenty year accumulation of silt to be removed from them.
2. How did the (man-made) banks cope before there were trees growing on them?
3. See point 1.
4. No-one is talking about removing gravel from river beds.
George then goes on to both hit and miss the point in one sentence:
"More trees and bogs in the uplands – reconnecting rivers with their floodplains in places where it is safe to flood (and paying farmers to store water on their fields while the danger passes)"
The first is a good idea, the second is how the Somerset Levels already work, and have worked for centuries. The problem is not that the Levels have flooded: they do that most years and it's how the problem of having more water entering the levels than can drain out is solved. George and the Environment Agency are pointing out that you can't stop the flooding in Somerset by dredging the rivers. This is true, but no-one is asking to stop the flooding, what they want is for the flooding to be less extreme and not to last so long. They want the water to be able to flow more quickly to the sea, like it did in the past, when the man-made rivers and drains of the Levels were properly maintained.
Wednesday, 5 February 2014
My latest blogpost: George Monbiot shoots from the hip againTweet this! Posted by Bayard at 21:50