On 27 Apr, 23:55, Robin Nicholson
wrote:
On Mon, 27 Apr 2009 12:00:31 -0700 (PDT), Graham Easterling

wrote:

. Unlike St Ives - victim of the EA's

latest flood relief scheme!

I would be interested to see what the scheme consisted of - is there
anything on line?
R

I haven't see any details, but the flooding in St Ives, both in 2002 &
Saturday, was due to the amount of water in the stream that runs down
the Stennack and comes out next to the lifeboat house, combined with
surface water on the road which runs down the same valley. Essentially
the scheme involved increasing the capacity of the pipes carrying the
stream, large grills at regular intervals across the road to take the
water into the underground drainage system, together with some form of
pumping system.

It appears that the water was flowing across the grills. They weren't
blocked (hence the EAs claim of success!) butr they weren't taking the
water either. There is a rumour that a pump was not turned on,
resulting in far too little water being taken out of the system.

Whatever the reason, the flooding was similar to 2002, but with less
mud & silt. The centre of this storm appears slightly more intense
than that in 2002, but the amount falling in the St. Ives catchment
area was similar, as the storm was slihgtly further west on this
occasion.

2002 - 80mm over St Ives, approx 120 over the higher catchment, which
was the centre of the storm.
2009 - 60mm over St Ives (52mm being the lowest recorded, on the
Island - a very windy exposed spot) probably 130-140mm at the top of
the catchment, with highest figures (150-170?) further west, draining
towards Zennor & the north coast.

So, as far as St Ives was concerned the events were very similar, a
perfect test for the scheme, which was supposed to stop a repeat.

Graham
Penzance