Too much water?

[cee-dee]

I've been thinking.... (OK, so thinking's a bad idea?) about all this water we've had and the poor unfortunates that have been flooded.

Now, if you've got a pipe and it's full of water, it's full and if you try to put more water in to it, where you're trying to put more in, it will just not go.

Streams and rivers are not constricted like a pipe, I suppose they're more like half a pipe? So when they're full and more water is put in to them, the water spills over the sides. There's absolutely no way you can constrict it. OK, so you build the banks up and what happens? The extra water backs up all the storm pipes leading in to that water course?

Someone could say "Ah-ha, we can deepen that water course" but what'll happen then? I suppose some group or other will counter that by saying "Oh no ya don't, there's all the wriggly things that live there, oh no way can you do that"!!!!!!!!!!!!

What do we do? Put all the properties on stilts? Knock 'em all down and move the communities? Where to?

So, what's the answer then? What bright ideas can anyone come up with?

[upthecreekyetagain]

Three bedroom detached houses £425k up to £750k for 5 bedroom.

This article is worth a read - https://www.theguardian.com/commentisfree/2014/jan/30/dredging-rivers-floods-somerset-levels-david-c...

and this one - https://www.bbc.co.uk/news/uk-25929644

[cee-dee]

Those houses were not what's called "affordable homes" by any stretch of the imagination?

[upthecreekyetagain]

Not sure of the relevancy but you are correct - not many "affordable" houses in Surrey!

The average price for property in Surrey stood at £607,693 in February 2020. This is a rise of 1.59% in the last three months (since November 2019) and rise of 2.95% since 12 months ago. In terms of property types, flats in Surrey sold for an average of £322,379 and terraced houses for £448,025. This is according to the current Zoopla estimates.

[bankhaunter]

Deepening rivers, drainage channels etc and getting the water out to sea as quickly as possible, simply means two weeks of dry weather and bingo, there's a water shortage.

[cee-dee]

You can't have it all ways can you?

After deepening (and widening) rivers and drainage channels moveable weirs could be constructed?

Also, as mentioned earlier, reservoirs (ooops, I said a naughty word?) are needed?

[bankhaunter]

Apart from the destruction of the environment by altering the characteristics of the river, holding the water back with a weir in the summer could simply encourage the depositing of silt.

Plus of course the water that would feed the river in the summer, has been lost out to sea, the important thing is to keep that water as much as possible in the higher reaches.  That would be completely negated by deepening and widening.

You cannot just mess about with the natural flow of a river without suffering some possibly unwanted consequences.

I fish the Upper Severn which twists its way across its flood plain, this is the sort of water level changes that can be expected.

https://rloi.naturalresources.wales/ViewDetails?station=2034.

It is already very wide for its normal flow, to the degree that much is too shallow to hold fish.  Trying to deepen it would be a joke, a pool several feet deep can be filled in overnight with stones brought down by a sharp rise in level.

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[upthecreekyetagain]

What is often forgotten is just how many rivers there are in the UK and that most cities, towns and villages are situated on rivers.

The idea of dredging all the rivers, even if this was desirable, is simply not practical.  

This website is a bit of an eye opener regarding the number of waterways there are.

https://www.wwf.org.uk/uk-rivers-map

[cee-dee]

Oh dear, "you cannot mess about with the natural flow of a river...."

The "natural flow" has already been "messed about with"! Umpteen bridges have arches or other foundation in the river bed and many hold debris during times of heavy flow contributing to flooding upstream of the obstructions. Weirs exist in many places and have done for a very long time. However, they're fixed, ie they're always there and remain the same height.

What do you propose to do to "retain the natural characteristics of a river"? Demolish all the bridges and weirs? With the weirs gone you'd soon see how low a river would get during Summer"

During Summer or times when rainfall is low, any fine silt travelling downstream and possibly retained by a weir would surely be washed away during times of heavy rainfall when moveable weirs were lowered?

I suppose those who oppose deepening a river and improving the flow during times of heavy rainfall are also those in favour of "messing about" with the flow of tributaries by re-introducing Beavers?

As to the lower reaches of the Severn, wasn't that "messed about with" by deepening to allow boats better access up the river?

There comes a time when people just have to make their minds up, do they want to retain the "natural flow of a river" and put up with associated flooding or try to do something about it.

[upthecreekyetagain]

Good luck with dredging 200,000km of rivers!

[**bustysbargains**]

More thorough clearing of the towns and cities drainage systems wouldn't go amis either. Every where I walk the street drains are all block up and water flows into the dips into streets etc. Flooding isn't just a problem along river ways and surrounding areas. In my opinion it is a clear mismanagement of water as a whole.

[suzieseaside]

There is plenty of evidence that dredging and deepening of rivers does not solve the problem.
Neither can you dismiss damage to the ecology of river systems as just a loss of wiggly things in the bed!!

[bankhaunter]

I can show you fields which have stone cage embankents that were keeping a river on a certain course.

The only snag is the river is no longer anywhere near them.

It is interfering with the natural flow of a river which causes much flooding, floods in the lower Severn come from water in the upper river.

Mess about with the upper Severn and it will make matters worse, hold back that water with flood plains etc, and flooding will be reduced.

Plus as I said, getting rid of the water as quickly as possible leads to summer droughts.

[upthecreekyetagain]

In any case, I'm not convinced that flooding really is as big a problem as many make out - it's only a minuscule percentage of the 25+ million homes that have been affected - awful if you are one of those of course but in the grand scheme of things not that big a problem.

[cee-dee]

I suppose the attitude is that flood plains are fine so long as they're on someone else's land?

In times past, a short flood was welcomed because of the fine silt left behind however, since then, so many houses have been built (in the wrong places?) and so much more land has been metalled one way or another that there's far more surface water being quickly directed in to water courses.

Sooooo, you've a few choices. 1/ put up with the flooding, 2/ deepen the water courses where the flooding's causing trouble or 3/ make some new watercourses.

3/ is not possible? Of course it is, look at the new London Tideway.

I'm familiar with gabions and thinking about where some were used on the Clywedog, if they're not properly used, yes, what you mentioned will happen. In the case I'm thinking of, the river simply undermined them (they weren't taken deep enough in to the ground) and eventually the river changed course. The Clywedog isn't a big river, in times when the river's low, in places you could carefully walk over it in shoes BUT..... don't go anywhere near it in flood!

[bankhaunter]

I don't think it should be unexpected that if you own land on a flood plain, sometimes it will be flooded.

It is known that dredging is not the magical solution, in many cases it is utterly pointless, what are they going to do, spend millions of pounds dredging every two or three years.

More trees in the uplands and farming methods that don't impact the soil would help, there should not be water lying in fields for days after heavy rain.

[cee-dee]

Yes, if you own land on a flood plain you should expect (even welcome?) short period flooding BUT... you shouldn't expect to have the land flooded for extended periods.

As to dredging being needed every few years, that's ridiculous because by that token the rivers would be completely choked by now.

If the bed of a river was, for instance 15 feet below the level of the land at the banks, deepening that river so that the bed is 20 feet below the level of the land at the bank would reduce the time any flooding occurred on the flood plain.

[upthecreekyetagain]

Dredging would only work if, in your example, the bed of the river was lowered by 5 feet all the way to the sea - have you thought about the cost compared to the actual damage caused by flooding.

Estimates are that flooding causes just over £2 billion of damage each year - currently around £800 million is spent each year on flood defences - this is mainly spent on densely populated areas making the spend cost-effective.

Just like coastal erosion, judgements have to be made on whether or not spending public money is worthwhile.  For example tens of millions have been spent on coastal defences around Brighton whereas just a few miles up the coast houses have been allowed to fall into the sea.

[cee-dee]

So, have you a reliable price comparison between flooding and dredging?

[upthecreekyetagain]

Not at all - but thinking of the river I am familiar with, the River Mole, that forms the boundary of our land, dredging would be prohibitively expensive as well as totally pointless!

during the summer the depth to the river surface is over 20 foot, in the winter it regularly breaks it banks - dredging during the winter wouldn't be practical due to depth of water, speed of flow and width of river, at about 25 foot with tight bends.  In any case where would the silt be deposited?  No access by road and the river isn't navigable by anything bigger than a rowing boat.

What would be the point of removing water from the natural flood plain?  If people buy houses at risk of flooding then why should the tax payer pay to protect them?

[fallen-archie]

Just out of interest I wonder if anyone has considered the value to our planet of exporting some of this water? It may sound crazy but with so much water here and so little in North Africa surely we could find the means to stop it all going into the sea and instead to use it for cultivation in places where it needed?