Wednesday 12 February 2014

More on flooding

The Telegraph publishes a piece from the horse's mouth.

Meanwhile others think it's all a deep laid plot by the EU. Pity Ishtar Dingir doesn't know that the Somerset Levels are meant to flood. Perhaps he should talk to Julian Temperley.

Anecdotally, my brother, also a farmer in Somerset, reports that the EA have been doing some river clearance, but along the Parrett upstream of the levels. As a result, when his bit of the river floods, the floods disappear in hours, where it used to take days. He also reports seeing water cascading over the tops of the banks of the Parrett, draining back onto the levels the water that the EA is spending so much of our money pumping into it.

15 comments:

Mark Wadsworth said...

B, roughly where is your brother's farm? How high up or down stream?

From the article:

"This reluctance to dredge is about as ridiculous as me telling MPs in London to take down the Thames Barrier, pull down the Embankment, and let the Thames flood Soho as it pleases.

The Somerset Levels, just like London, are a man-made environment; the River Parrett was not put where it is by God but by man."


Top stuff.

Bayard said...

About eleven miles up stream from Thorney, NW of Haselbury Plucknett.

DBC Reed said...

Where was the Parrett originally then?

Bayard said...

Dunno, we weren't very good at maps in them days.

DBC Reed said...

I expect it flowed through the bridges such as at Bridgwater as it does now.

Bayard said...

Yes, I expect Langport and Bridgwater were fixed points, but the course in between was modified.

DBC Reed said...

@MW In reply to your question : Haselbury Plucknett is about 5 miles from the source of the Parrett in Dorset .Not exactly on the Levels.
@B
Langport is about 10 miles from Bridgwater ,which is not far to the sea down a very twisted channel but the stretch in between the towns does look suspiciously straight(ened).I suppose the very early steam pump at Westonzoyland was installed by
enclosing/draining nasties who however were stymied because the water level kept dropping leaving the pump high and dry.As in all such cases: they were pumping water UP from the rhyne into the Parrett.The enclosers/drainers could not comprehend that ,after drainage, the peat they were after for rich soil,shrank.See Holme Post near Peterborough.

Bayard said...

DBCR, that's my point, the flooding upstream of the Levels now goes down faster because the fallen trees etc have been cleared from the rivers, so the flooding on the levels rises faster and goes down slower. We can both remember much worse flooding than he has at the moment, after a lot less rain. My brother has written to the EA suggesting that they simply block up the rivers upstream of the levels and allow them to flood, thus holding back the water. A few "big bales" should do the trick.

Downstream of Bridgwater is tidal, so nothing needed to be done to it.

"The enclosers/drainers could not comprehend that ,after drainage, the peat they were after for rich soil, shrank."

I'm surprised. I thought they employed Dutch engineers. The same thing happened in the Netherlands when they drained their marshes. Perhaps they'd forgotten.

DBC Reed said...

@B
I'm all at sea with your explanation. You seem to be saying that the Levels are being flooded by water from the Parrett tippling over onto the levels and that a few big bales placed five or so miles from the river's source will do the trick.
NB The Parrett is tidal up to, I believe, Aller which is upstream from Westonzoyland.The river only falls a foot in the ten miles between Langport and Bridgwater so a high tide causes water to back up: not flow at all.
The problems and the solution ,if there is one, would appear to lie on the Levels not in the rivers which do not, by gravity, drain them but flow above them and past them.
People keep saying Dutch engineers worked on the Levels but apart from "Calamity" Cornelius Vermuyden buying some land, there does not appear to be much evidence of their involvement.Our blokes could make just as much a mess of it without them.

Bayard said...

Firstly, "a few big bales placed five or so miles from the river's source" will do bugger all. My brother's point was that if all the tributaries to the Parrett, the Tone and all the other rivers that flow into or across the levels were blocked up to replicate the situation a few years back before these streams were cleared, then a) more water would soak into the ground and b) the flow onto the levels would be reduced.

Secondly, the levels work like this: there are a series of drains and embanked rivers which cross the Levels. At low tide, the water at the mouths of these rivers and drains is well below the level of the water at the point where they enter the levels. The rivers thus empty into the sea at low tide. When the level in the rivers and drains falls below the level of the water in the rhynes, these empty into the rivers. When the tide comes in, sluices stop the water flowing back into the rhynes and the rivers fill up both from upstream and from water pumped into them. The drains thus act as both a water conduit and a reservoir. It must be obvious even to the most ardent partisan of the EA that if you stop dredging these rivers, their capacity both as reservoirs and as conduits in much reduced, thus causing overflowing at high tide and reduced draining at low tide, in conditions where high rainfall increases the amount of water flowing into them from upstream. It must also be obvious that, if you reduce the flow rate from upstream, the amount of overflowing is lessened and or the amount of water that can be pumped in after the sluices have shut is increased.

DBC Reed said...

@B You seem to be saying that all the clearing of the Tone,Yeo etc has made things worse but that the EA has also made things worse by not clearing/ dredging the rivers.You cannot have it both ways.
You also talk about "drains" all the time as things that empty by gravity into the rivers (above them).The only drains as far as I know are the rhynes which if you read the Wikipedia for the Westonzoyland steam pump only entered the river by pumping upwards.
You appear to believe that all the floodwater is rainfall coming down the Parrett.It is, on the contrary, rainfall falling on the Levels ,filling up the rhynes and spreading out.
Your talk of reservoirs is more to the point: the Huntspill River used to act as a long thin reservoir and feed 4.5 million gallons of water per day into the Royal Ordnance Factory Bridgwater actually at Puriton I believe ; likewise a reservoir was built by the Mayor at Durleigh outside Bridgwater in the 30's to feed 1.5 million gallons per day into the new British Cellophane plant . I know this because the enterprising Conservative Mayor of Bridgwater (who was actually alleviating unemployment) was my grandfather,FJ Reed.

Bayard said...

DBCR are you being deliberately obtuse in order to troll me? Surely you cannot be so slow-witted as not to be able to distinguish between clearing the rivers that feed the Levels, upstream of the Levels and clearing the rivers that drain the levels where they cross the levels.
Ditto as not to see that rivers act as drains for an area as well as channels to carry water from above the area cross that area to the sea, that rivers that drain an area can be referred to as "drains" without having to explain this usage more than once, that if a channel (drain or river) has to contains a certain amount of water which has to flow out of it in a limited time, then it really doesn't help if there is more water coming in at one end and that the more water that comes in at one end, the less effect the water flowing out at the other will have on the level in that channel. If you find this hard to visualise, just think how long it takes a bath to empty and then how long it would take to empty if the taps were left on.

DBC Reed said...

You are still banging on about rivers: the rainfall is not coming down to the levels by river.You are so slow-witted that you cannot work out that the rain is falling on the levels and not enough of it is being pumped into the rivers( which are not "drains" in any meaningful sense,since liquids drain out of the bottom of things.) Is this clear? All this bollox about the EA not clearing the "drains" is just bollox .Clear the drains/ rivers and the floodwater would still just lie there,at first in the rhines and then in lakes when the rhines fill up.If you pump rhyne water (rather good I thought) into the Parrett,then its not going to go far because it only falls a foot in ten miles, do with the river bed what you will.

Bayard said...

DBCR why do argue with me when you know nothing about what you are talking about, nor read what I write? The water level in the sea at low tide is below the water level of the rivers, the levels, the rhynes, the drains and everything else. When the tide is out the water drains from the rivers, levels, rhynes, drains etc. into the sea. No pumping is required. Pumps are for emergencies, like times of high rainfall when the amount of water flowing out at low tide is less that the amount coming in either from rainfall onto the levels or from upstream.

"because it only falls a foot in ten miles, do with the river bed what you will"

Please don't emphasise your ignorance of hydraulics. If you have a channel 20ft deep full of water, then the head (pressure) of water at the bottom of the channel at one end is 20ft, regardless of the slope of the bottom of the channel. Even if the water is 21ft deep at the one end, the head at the other is still 20ft. So, if the Parrett at Langport is 20ft deep and the tide goes out so that it is only 5ft deep at Bridgwater, then the effective head at Bridgwater is 16ft. (15ft of water and 1ft of fall on the bottom). Going by your logic, if you had a swimming pool full of water with a level bottom and you made a hole at the bottom at one end, then no water would come out, because there was no "fall".

DBC Reed said...

If the swimming pool is 37 miles long like the Parrett, I don't suppose it would empty very fast, from one end. Making it deeper by dredging is not going to make much difference if the gradient is infinitesimal.
If you want reservoirs why not argue for them? A few long deep reservoirs might make a big difference. I believe the Norfolk Broads started off as flooded peat workings.