Re: Dredging the Ancholme

2011 mar 22

Email: 2011mar21 from Chris Newmarch

Re: Dredging underway

Hi Brigg Life

Having driven over the Bridge and seen the barge I looked on the internet to see what was happening.

I found a bit on the river about dredging to remove 3,500 tonnes of silt, this must only equate to an olympic size pool of soil, to be honest what good is that given the total volume of water .

It also says the removal of silt will speed up the flow , this is not true as with a constant flow the speed will be reduced over the greater cross sectional area , the reduced speed will drop deposits and refill the areas dredged.

Surely £60,000 could have been better spent ??

Ed replies

I see what you are getting at. The pool of silt removed does indeed look tiny in comparison to the size of the river. The mud pool only appears to be just a little larger than half the width of the river Ancholme and it can't be that deep, so you wouldn't think that the amount removed will make much odds.

Each year when I clear out the garden pond, I take about 5-10cm of mud off the bottom - which amounts to a huge number of bucketfuls of mud! If the same amount were taken out of the Ancholme each year, I would have thought that it would be much more than would fit in the bund on Island Carr.

From what I can remember of my school physics, a wider, deeper river should flow more slowly. I guess that's why river deltas form from the silt which drops out when the water slows down. Having said that, if you try to push more water down a restricted channel, there is only one place for the water to go: up and out of the channel.

It's good though, however, to see the river authorities doing something at last ...