Wet in Wales? Crickhowell under water

alastairgott

Well-known member
Just spotted this showing how much water is flowing through crickhowell.  :eek:


https://www.bbc.co.uk/news/av/uk-wales-51525876/crickhowell-left-under-water-as-storm-dennis-strikes?intlink_from_url=https%3A%2F%2Fwww.bbc.co.uk%2Fnews%2Fuk&link_location=live-reporting-map
 

mikem

Well-known member
& elsewhere (Crickhowell bridge may be closed for a while):
https://www.bbc.co.uk/news/uk-wales-51517529
 

Huge

Active member
It's been extremely wet. Very bad flooding also on the Taff, from Pontypridd down to north Cardiff and in the Vale of Neath. More minor flooding has been very widespread and there have been a number of landslides. Houses in my village have flooded.

In the caves, a group on their way out of Draenen had to swim parts of White Arch Passage (always a small steam here in the boulders but it's usually possible to get all the way along without getting the soles of your boots wet!), on Saturday and found a waterfall coming down the rope climb at the start of the Pitch Bypass! They exited the cave with no problems though. I've been in the cave countless times but never seen this occur, despite going in/out during named storms in the past. I know that one person in Saturday's group has experienced similar conditions in Draenen before.

I've heard that the Hardrock Cafe camp in Daren was starting to flood yesterday while a camping party were there/leaving. I've heard of the old diver's camp further down the passage flooding and the bottom end of Bonsai backing up but never Hardrock being affected!
 

Maj

Active member
Huge said:
It's been extremely wet. 

I've heard that the Hardrock Cafe camp in Daren was starting to flood yesterday while a camping party were there/leaving. I've heard of the old diver's camp further down the passage flooding and the bottom end of Bonsai backing up but never Hardrock being affected!

Re Daren. I was planning on being on the camp over the weekend, but didn't go in the end. Part of me wished I had gone to see the once in a lifetime event, but part of also said I'm glad I wasn't there.

All those on the camp, which included two Uni groups and some usual Daren Diggers, are all out safe.

I'm hoping those that were there will write an article for Descent about it all. I don't know whether anyone had a camera or took any photos.

Apparently in the early hours of Sunday morning the water level rose and flooded Hardrock Cafe to a level above the cooking area  :eek: . Lots of boulders and mud shifted, lots of work will be needed to repair/reinstate the camp. Some kit lost or damaged. No bog rolls  :eek: !

If any one was thinking about a trip in the near future I would recommend you be self sufficient and please take a camera to at least record how it is now. 

Maj.
 

Graigwen

Active member
Huge said:
In the caves, a group on their way out of Draenen had to swim parts of White Arch Passage (always a small steam here in the boulders but it's usually possible to get all the way along without getting the soles of your boots wet!), on Saturday and found a waterfall coming down the rope climb at the start of the Pitch Bypass! They exited the cave with no problems though. I've been in the cave countless times but never seen this occur, despite going in/out during named storms in the past. I know that one person in Saturday's group has experienced similar conditions in Draenen before.


Some of this water was of course what was spouting out of the ground in the Bouncing Field.


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Graigwen

Active member
Now that the weather has calmed down a bit and river levels have fallen, we can consider whether anything of speleological value can be learned from the recent floods.

In the Eastern Valley, resurgences on the east bank from the Castell Coch Limestone continued to show the somewhat anomalous behaviour noticed during very heavy rain last autumn. Whatever reputation this limestone has as an aquifer, it cannot be regarded as a single interconnected system.

The Bouncing Field flooded again on the evening of the 28th February. It is not possible to draw precise conclusions from the relationship between such events and the level of the Afon Llwyd as there are too many uncontrolled variables, including different catchment areas, different flow rates and poorly understood upstream interactions between the surface and underground systems (for instance water passes continually from the beds of the surface river and streams into the underground system at three points at least south of Blaenavon). However the flooding on the 28th was interesting because it took place when the surface river was at a level that has not coincided with flooding of the Bouncing Field in recent years, and a very big extended surge coming down the underground system from north of Blaenavon was not expected (although there had been locally intense rain.). It is clear there is a major constriction in the current main conduit to Pontnewynydd Rising that causes water to back up in the underground system at least as far north as Abersychan. The Bouncing Field does not flood until the water level in the underground system is at least 25m above the level in normal flow conditions. A tentative explanation for the unexpected flooding on the 28th is that the heavy rain from the 8th February onwards had left the storage capacity of the underground system still largely water filled, waiting to get past the constriction north of Pontnewynydd. In other words, in normal conditions there is not just the conduit carrying the "Beyond a Choke" water from Abersychan to Pontnewynydd but also a lot of air filled cave awaiting exploration.


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Pitlamp

Well-known member
I don't often get chance to go caving in Wales but your post above (Graigwen) is really interesting.

Could you tell us what's the significance of the name "Bouncing Field"?
 

Graigwen

Active member
Pitlamp said:
I don't often get chance to go caving in Wales but your post above (Graigwen) is really interesting.

Could you tell us what's the significance of the name "Bouncing Field"?


It is called the Bouncing Field because it is a field and it sometime bounces, like a giant trampoline.

Water coming up under the turf from the underground system through narrow channels lifts the turf away from the bedrock so you can bounce on the turf. The limestone under the field is very thin, the river a short distance to the east runs on mudstone and the water is thought to come from the west of the field. The most spectacular feature is an estavelle in the middle of the field which accounts on some occasions  for the rapid flooding and subsequent draining of the field. (There is also a flood overflow channel leading back into the surface river to the south.)

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Huge

Active member
That's very interesting Graigwen. Are you planning to publish your work on the area? Maybe in a club journal or even Caves & Cave Science?

BTW, how did you arrive at the figure of a 25m rise in water levels to cause flooding at the Bouncing Field?
 

Graigwen

Active member
Huge said:
That's very interesting Graigwen. Are you planning to publish your work on the area? Maybe in a club journal or even Caves & Cave Science?

BTW, how did you arrive at the figure of a 25m rise in water levels to cause flooding at the Bouncing Field?


I am not a member of any club.

It might be worth publishing when we have 8km of river passage to go with it.

Altitude of the Bouncing Field less the normal altitude of water in the underground system at Snatchwood plus 1m.  (This figure could be wrong if there are surface:underground system interactions which we have failed to find between SO 2706 0367 and  SO 2697 0275.)

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Pitlamp

Well-known member
Thanks for taking the time to explain that above Graigwen.

Huge does make a good point though, publishing at least something about this relatively unusual karst system in BCRA Cave & Karst Science would be of value.
 

Andy Farrant

Active member
The hydrogeology of the Draenen system, of which the bouncing field is part, has been published in Cave and Karst Science, as part of a special issue on Draenen. See http://bcra.org.uk/pub/candks/index.html?j=112

Well worth a read if you want to understand the groundwater regime in this area, and the prospects of new cave, which are considerable... 

If anyone would like to contribute papers for C&KS, then John Gunn and Dave Lowe would be happy to hear from you.
 

Huge

Active member
Andy, the Draenen special issue of Cave and Karst Science, which of course you contributed two papers to, along with Mike Simms, is excellent! I had to read it through several times to get my head around everything though!  :)

Would you be willing to answer a few questions I have regarding what you say in those papers, if I emailed them to you Andy? I realise you are no longer the Geological Recorder for the PDCMG.
 
Huge said:
That's very interesting Graigwen. Are you planning to publish your work on the area? Maybe in a club journal or even Caves & Cave Science?

The Cambrian Cave Registry is another place that benefits from active feedback by cavers and explorers in Wales and the Marches (although not the Forest of Dean,  for which try http://www.fodccag.org.uk/registry/index.php ). This can be kept confidential, although early release of information obviously limits the possibility of disappointment on finding that your discovery has already been explored, and perhaps named, by someone else (an example of just such an instance was recounted in the latest edition of Wales Underground [ http://www.cambriancavingcouncil.org.uk/pdf/newsletters/2019/December2019.pdf ]). All who have a special familiarity with particular caves or areas are welcome to review the relevant entries and get them updated or corrected. I am sure any contributions to registrar@cambriancavingcouncil.org.uk will be gratefully received, and an increase in the small number of regular correspondents would be very welcome.
 
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