hvered wrote:Wouldn't dredging increase the rate at which river water flows and result in even more flooding?
On the Somerset Levels, a lot of ground is below sea-level, and the main rivers are built-up with embankments. So that water falling on higher ground can usually flow through the Somerset Levels, and out to sea, without flooding the plains.
Like the Mississipi Levees or the Dutch Dykes.
Megalithic connection alert!
The Roman chronicler Tacitus mentions that the rebellious Batavi pierced dikes to flood their land and to protect their retreat http://en.wikipedia.org/wiki/LeveeBut due to neglect by the UK's Environment Agency, which has reduced the amount of dredging it does, the capacity of the rivers has been critically reduced.
For an analogy, think of the gutters on the roof of your house, collecting the rain that's falling on the roof and carrying it away. If (say) you had a gutter six inches wide (therefore three inches deep with a cross section of (Pi * 3 * 3) / 2) it can carry a goodly amount of water. But if you fill most of the gutter with moss and debris from the roof, it will only be able to carry a small fraction of that water before it starts spilling over the edges.
If you routinely clear out the gutters, with a bit of preventative maintenance, all is fine. On the Somerset Levels, if routine maintenance had been used, the dredged material would have been usefully used to build up the height of the banks or farm land. But with the floods we've got now, the flooding has flooded septic tanks and sewage works, and the crops under water are dying, so the flooded areas are polluted. So when they start dredging the rivers again, they will have a more difficult job finding somewhere to put the dredged material.