What (new) building/local regulations would YOU enforce in 'flood plain ' builds?

[The Natural Philosopher]

Oh dear. You had better tell the people that make motorways that their embankments are all in danger of sliding into the cuttings, including the custom service station (complete with petrol/Diesel tanks)..;-)

I can assure you that by the time a few 50 ton tracked vehicles have spread and smoothed the soil around, its stable. Its also free of tree roots, unexpected voids, and underground streams.

Agreed that ORGANIC waste will decompose, which is why there IS normally a 20 year 'no build' clause and trial diggings before people CAN build on it.

But that wasn't the proposition. The proposition was to strip the topsoil, excavate the subsoil to form a lake, build a mound, and stuff the topsoil back on it.. You could even connect the lake via a canal to the river system, forming a nice flood water reservoir.

The advantages are two fold. You have created a larger reservoir for flood water, reducing downstream flow rates, and you have created an effective flood island, on which to put your houses. The houses need be nothing special whatsoever.

And it is really cheap.

I estimate that at 7 houses to the acre, a 70 house estate on 10 acres of mound with 10 acres of lake - about 200 meters square, and a 3 meter uplift, represents about 120,000 cu meters of soil to be shifted..lets say 200,000 tons. A big digger can fill a 30 ton dump truck in about 5 scoops..so you probably need about 4-5 of those and one digger and one to two bulldozers to spread it about..say 10 people. If that digger is pulling a load every ten seconds or so..

Thats about 30 tons a minute, so 6,000 minutes or 100 hours. Do it in three weeks ..Very roughly. Order of magnitude stuff. 1000 man hours at

10 quid an hour, say 10,000 quid? Spread over 70 houses? Less than £200 a house. Leaving some slack for machine hire etc.

Compare and contrast with the cost of flood damage.

And look what you get..houses with a view overlooking a tranquil lake, all hung about with willows, suitable for summer bathing, fishing and boating. Or even winter skating... MMM. THOSE houses will be SNAPPED up.

AND your flood plain capacity is pretty much what it was..especially if you pump the lake (or let it evaporate) BELOW river level in dry periods.

[The Natural Philosopher]

Until regulations insist that they DO care about where the water goes.

[The Natural Philosopher]

Not necessary. Building earth banks is well understood technology. Since the days of the steam train..

[dennis]

Where do you live? I estimate 20 homes to an acre at least. Seven to an acre is real high end stuff around here.

[Anthony Frost]

I do think that 90%+ of them use solar power and batteries because that is how they work. They have "booster rockets" as you call them to make sure they re-enter in a destructive manner over a nice wide bit of sea rather than take a chance of bits landing relatively intact over hostile territory.

The very few that rely on any form of nuclear power, which is what I'm guessing you think is involved, are carrying high power radar and have enough trouble with drag from the large antenna panels without adding huge solar panels. They are also almost exclusively Russian, the US has never orbited a working reactor so far and tries to avoid RTGs for political reasons, and they've managed to drop one on Canada and one on South America by accident when end of life orbit changes have taken place in the wrong direction.

Anthony, MBIS

[dennis]

Its how to build on landfill after a year or two for people to forget it was a tip.

[The Natural Philosopher]

Really? Ive got an acre of back garden here, and I would not think that you could fit, with access roads, more than abut 7 'townhouses' on it.

Its 120 meters by 30 meters roughly.. If each house is 20 meters wide, and twenty meters deep with a 10 meter back garden, that means 6 houses would fill it without the access roads at all.

I cant imagine what sort of rabbit hutches go at 20 to the acre..

one acre is 4,000 square meters..if you are going 20 to the acre, that is 200 square meters per house.. 2000 sq ft including parking and access and garden..a mere 10x10 meter house, with 5 meters of frontage and 5 meters of back..yeah I suppose you can get a small 3/4 bed house on that..with a postage stamp garden.

I must say I'd be inclined to do the outlined development as 3 storey houses with NO garden.just large balconies...since you have to leave a substantial area of land free for water management, that gets to be a communal space as it were. I was really thinking of very upmarket and exclusive stuff..

[The Natural Philosopher]

Eh? In a vaccuum?

[The Natural Philosopher]

I am not talking landfill.

Landfill is a completely different kettle of fish,

It takes considerable time to settle, and it may outgass, and give of hazardous chemistry for may years, as ell as subside inhomogeneously.

Nuclear waste is of course far more suitable ;-)

[Jules]

Even on soils such as heavy clay? I'm just thinking of how many houses I've come across with cracks in the walls because the underlying soil's shrunk over the years and so everything's shifted slightly...

(Hmm, how much does a typical two-storey brick house actually weigh anyway?)

I notice the new Great Barford bypass has had several patches applied to it in recent weeks to get rid of lumps and troughs where the underlying ground's shifted - good job that wasn't a housing estate instead :-)

Or even summer skating if some of the doomsayers are right ;)

[Clive George]

Define a vacuum. At what height do you think there is one?

cheers, clive

[The Natural Philosopher]

Thats a lot more stable than sand.

Trees mainly. Modern building control knows how to cope with that..the foundations simply go down a meter plus thats all. The stuff that cracks is mainly laid either over something really bad, or has 6 inch deep strip foundations. If you add some steel to strip foundations you end up with a reinforced concrete beam that may go up and down, but won't crack on you.

Add a raised block and beam concrete floor, and there's even room for the flood to go underneath :-) It will take any amount of heave without floor buckling too.

The only subsidence that occurred with MY earthnmoving games, was when I buried large amounts of BIG rubble from the old house..gradually the soil slipped in between the lumps of brick and stuff, and the ground sank.

The dais I built from subsoil pulled out of the pond - good wet blue clay - has been rock solid. You need to be careful of certain types of material

- organics will shrink on decomposition, so strip your topsoil first, and save it for gardens afterwards, plus no rubbish please.

- material with voids in it will be subject to subsidence. You may THINK a base of crushed limestone is great, but you had better crush it properly, otherwise soil seeps into the cracks in time.

- anything that goes limp in water is an issue - sand is very unstable.

- slip angles must be carefully assessed if you don't want an Aberfan on your hands before vegetation stabilizes the slopes.

But this is known stuff.

another thing that you can take advantage of, is that you could - since you are building soil up anyway - simply pile it up somewhere, so all the cable and pipe laying is done at surface level, and build your foundations straight on top of the flood plain, and then fill it all up with topsoil AFTERWARDS. Its a relatively quick job to fill a hole with a digger.

Massive. Hundreds of tons

You don't have 30 ton trucks bouncing on it. And if its sagged its been badly engineered in the first place. Road building starts with soil, and then there is a layer of crushed limestone applied as a load spreader..then the top surfaces are pushed over that. If you skimp on the limestone..it WILL collapse due to soil spreading.

Yup./

>

[The Natural Philosopher]

Effectively at about 60 miles up..

[The Natural Philosopher]

'Kinaida.

No wonder they take drugs..

[Roland Perry]

In message , at 13:07:19 on Fri,

27 Jul 2007, The Natural Philosopher remarked:

I think the current "standard" for inner cities is 24-40 per hectare, which is 10-16 per acre. Classic 5-bed detached executive homes used to be more like 4 per acre.

[Clive George]

There's a difference between "effectively" and "none". There's still drag on low earth orbit stuff.

[Tony Bryer]

Traditional 1930s semis are 8 to the acre. I would have thought that the average town house had a frontage of 7.5m or so. Say 5m in front of the house (parking), 9m house depth, 10m garden, 4.5m half width of road and that's 19 to the acre.

[Anthony Frost]

Indeed. The camera and radar sats keep as low as they can, their lifetime is governed in a large part by the amount of fuel they can carry for reboosts. One of the reasons the ISS has furled one of its solar arrays is to cut down the drag until the extra power is needed for the European and Japanese labs, and that's orbiting a good bit higher.

Anthony

[tony sayer]

In article , Clive George writes

Cam.misc on a Friday afternoon eh?, never happens anywhere else for most all people 60 miles up is a "sufficient" vacuum;)...

[Clive George]

I'm getting this via uk.d-i-y, where it appears a dyson isn't a sufficient vacuum :-)

cheers, clive