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]

Sure - but that's probably the case for the majority of homes in the UK.

About the only "no flood risk" place to build would be on the peak of a mountain.

[cee-dee]

Not a bit of it. You don't need to be on a maountain at all. If a river has an exceptional flood 25 feet above "normal", anything above that will be OK.

Anyway, rivers are usually enclosed within "banks" and the "normal" level can be anything from 10 feet or more below the banks so if the river was deepened, much more of the building level would be above the exceptional flood level.

[upthecreekyetagain]

Anywhere that is downhill from somewhere can suffer from flash flooding 

[upthecreekyetagain]

Deepening rivers - isn't that just taking steps to mitigate the risk of flooding?

[cee-dee]

If they actually did some deepening, that really would mitigate some risk of flooding.

[suzieseaside]

Hmmm, and what about the negative effects ? - destruction of bank vegetation and decreased stability, hence more erosion and then sedimentation downstream, loss of refuges and loss of habitat diversity, increase in invasive plants like Himalayan Balsam that take advantage of the disturbance of native vegetation cover, damage to aquatic fauna much of it food for fish and other wildlife, and so on ......
But then so many people don't think a bit of habitat damage here and there, or a loss of ecosystem function here and there matters. It does, and it all adds up.

[cee-dee]

More work for the eco people to fathom out how to balance reduction in flooding coupled with habitat re-instatement?

[bankhaunter]

I notice the Severn at Caersws rose nearly 2 metres about 30 hours ago.

As for how quickly a river can silt up, there was a length of the river where a few yards from the bank I would be wading about hip deep to fish, within  two years it shallowed to no more than halfway to my knees.

At the junction of the Trannon there used to be a large deep pool, the run in widened one winter and the pool filled up over the next three years.  The same with the pool where the Carno entered the main river.

It's what happens when the flow slows down.

[cee-dee]

Ah well, out with the dredger.

[cee-dee]

My turn to ressurect an old thread!

We've just seen the devastating floods in Germany? Now leaving those aside and concentrating on drainage here, isn't it high time the rivers were cleared and deepened? It's OK going on about creating more wetlands to hold water back but when the wetlands are already saturated, they provide no benefit whatsoever?

Lots of land has been built on and other areas covered in concrete and tarmac so what rain that used to soak in there is now run-off and it has to go somewhere by some means? The drainage system taking the run-off to rivers can't cope with it and the increase in water in the rivers is causing more flooding anyway because they're at capacity (or more?) in times of exceptional rainfall.

If areas of housing get flooded and the drainage system is improved (bigger pipes?) it'll move the flooding to the riversides?

There's no doubt we're heading for a "warm period" so that means more evaporation of sea water. When the clouds are "full", that means a lot more rain. There's nothing we can do about the warming or evaporation but we can ensure the rainwater makes its way back to the sea more easily so it's about time that was done?