On 06/08/2019 12:03, Roland Perry wrote:
In message , at
11:31:36 on Tue, 6 Aug 2019, Robin remarked:
On 06/08/2019 11:09, NY wrote:
"charles" wrote in message
...
I don't see how you can possibly infer that. It's *possible* but given
the speed with which fast moving water can erode riverbanks etc, it
seems
equally likely that this was an "acute. event.

If the water had been going over the slipway, then I'd agree with your
suggestion.Â* But it wasn't.
Â*I thought on the day that the news first broke about Whaley Bridge
thereÂ* was a video which showed a lot of water cascading over the
full width ofÂ* the spillway. I got the impression that this was a
recent video datingÂ* from a day or so earlier, with the implication
that it was after thisÂ* that they slabs were found to be cracking.
Â* Interesting that
https://www.bbc.co.uk/news/uk-englan...shire-49247226 shows them
taking the outlet of the pumps over the lower part of the spillway on
the opposite side to the collapse. I'd have thought they'd want to
avoidÂ* any more water flowing over the spillway in case of
undermining of theÂ* earth fill beneath the concrete.

Indeed.Â* The spillway was being asked to do its job. But ISTM as yet
unclear if the problem was lack of maintenance, poor design, or more
water than it was designed to handle.

Some rather more than averagely informed comments are at
https://www.sciencemediacentre.org/e...s-that-the-wha
ley-bridge-dam-has-been-damaged/

"Within the last few years new valves have been placed in the dam to
expedite rapid drawdown in emergencies: presumably, this is happening now."

Although the question being asked in this thread is "if that's the case,
why also use lots of pumps".

well I don't claim to have any engineering qualifications but it seems
to me a plausible answer is in the public statements:

- the spillway was damaged leading to a risk of catastrophic failure,

- there was a lot of water in the reservoir

- water was still coming in at a high rate (and with the risk of more
rain to come)

so it seemed like a good idea to lower the level faster than would be
possible without the pumps (with the added benefit of being able to send
water to different places and so avoid downstream flooding).

To the best of my recollection and belief, all the above is on the
public record.

But then some prefer speculation.


--
Robin
reply-to address is (intended to be) valid