Malcolm Stewart wrote:

A few days ago we had what I guess was a cloudburst, and I'd estimate that
the rainfall rate maximum was of the order of 6in/hour. (This is based on
the observation that a wheelbarrow in the garden which was 1/2 full before
the storm was full to the top and overflowing after around 10-15 minutes of
torrential downpour, and I've tried to take the shape into account. (At
the same time my gutters were discharging huge quantities of water where
their walls were slightly lower than elsewhere. Very dramatic, caught it
all on video.)

You aught to post this bit on UK.sci.weather to get some expert help to
interpret that fal rate as it is an astonishingly high number but then
there was a flood in Wiltshire at about that date.

The video would help.

So, seeing all this water go to waste via my garden and presumably, the
local River Great Ouse, I started thinking about how we could improve the
storage of water in these downpours and flash floods. In domestic gardens,
we could increase the number of water-butts dramatically and arrange that
when one is full, others are then filled. In Milton Keynes we have a number
of balancing lakes designed not to store water for local usage (other than
as nature reserves, boating lakes), but primarily to reduce flooding down
stream of Milton Keynes.

I think the point I'm trying to make is that simply letting summer flood
water flow un-impeded into the river system is wasting a huge resource, but
apart from lots of water butts, I can't think of any better way of storing
it. Is there more that could be done by increasing the number of
underground resevoirs?

Whatever the situation, the collection was for a very small area.
Spread out over your location it wouldn't be very much -in 10 square
miles,say if the cloudburst was over a 1/2 mile section of it.

Rooftops and concreted paths, roads and pavements catch a great deal of
water that goes straight back into the rivers with no time to drain
into the ground.

Farmers went mad after WW II cutting down trees ripping out hedges,
filling in ditches and planting drain pipes. There was once a great
deal of uncultivated marshland and cultivated water meadow in Britain.
All put to the pough these days; so the pressure is increased on the
land to dry it out either in use, in the drains or both.

Large spread-out connurbations that Britain favours these days rather
than cramming everyone into towers, increases the flow rate. Think what
1/2 an inch of water on your roof measures. There are tables online to
work it out.

Look at the ratio of hard standing vss greenery in your area and
multiply it by the number of towns in a road atlas or something and you
get the picture.

If every home built had a cistern dug that would allow the collection
of all water that fell on it to sink into the land instead of forcing
it through to rivers, the problems would change from floodings to
landslips.

The problem began in Victorian times when rivers and streams were
annexed for sewers. Exacerbated in WW I with the deadly need for
change in farming that brought. Then as the indusrtialisation took
over, urban sprawl started to fill the valleys up from historic ancient
towns that could not cope with the influx of effluent caused.

So now they have to divert rivers and enchain them and build flood
barriers and the like. And all the while underground resevoirs are
emptying. What you are enthusing about is an hi-tech answer and that
means yet more money.

The alternative is buld more resevoirs. But the water companies are in
the hands of asset strippers so you can't see them investing in
resevoirs any time soon can you.

What you can do is: move, build to cope or grin and bear it. In
biblical times householders -if rich enough, did build cisterns and
lined them to store water through their summers. (Apparently such
artifacts still exist in the Sahel where they were used to water stock
and are still usable if repaired.) But life was simpler then and a
public bath was a dip in a local river like everyone else.

We live in an hi-tech democracy, so whater the majority wants -no
matter how unreasonable, the majority might get. So beware what you
wish for. Some damned fool will press for it hard enough to get a vote
for it.

But you know yourself from the history of the area what hi-tech has
done over a number of centuries:
www.geog.cam.ac.uk/.../flobar1/studysites.html