Sleets Gill

JasonC

JasonC

Well-known member
Sleets Gill was on our club meets list for this weekend, which we've obviously had to cancel due to the amount of rain we have had/will have.

Now I know it needs 'a period of settled weather' before safely attempting it - but it made me wonder just how much? Three dry days? A whole week?
(Let's say I wanted to get to the Ramp without drowning in Hydrophobia).
Has anyone any experience of this trip, either when it's been surprisingly wet (ie too wet, even after some dry days), or surprisingly dry (doable, even though it's been wet) ?
(And yes, I know it has 'unpredictable hydrology' so there's likely no hard-and-fast answer).
Thanks!
 
H

harrylong

Member
Hi Jason,
One of the major problems with Sleets Gill is not knowing how much water is already percolating down through the overlying limestone in quite a large catchment area. Because of this, a relatively small amount of rain can provide enough extra percolation water to produce flooding in the cave. Equally, a larger amount of rain when the amount percolating already is virtually nil may have no adverse effect in the cave. - hence the unpredictability as there is a big unknown element here.

When Roy Deane and Les Hewitt were trapped at the inner end of The Main Gallery in March 1992 they were obviously there on a day when the odds were in their favour and there was not enough flow to fill The Main Gallery completely. Based on the water level I found at the bottom of the entrance slope and using Dave Brook's highly accurate survey (got from him at a time when he was asleep at home in Leeds!) I came to the conclusion that it was worth getting divers in to see what they could find.

The first 2 divers were Geoff Crossley and Johnny Shaw and although they expected to find bodies they agreed to dive. The rest is history and over a period of time numerous other divers all played a part in equipping and assisting in diving Roy and Les out of the cave.

When I made a visit to the entrance 24 hours later to look for lost gear I found a very large torrent resurging from the entrance and where Roy and Les had sat things out would have been totally submerged.

For a fuller version of events the chapter in the UWFRA book,"Anytime...Anywhere" (If you can find one) gives an insight into various peoples' memories.

So Jason, as you can see there is no ready guide to when it is safe to enter Sleets Gill Cave. My usual method was to see what the state of flow in other adjacent.white water risings was and the volume flowing in Moss Beck and at Kilnsey Crag and then flip a mental coin. Perhaps this hasn't been much help to you but it may make you err even more on the side of caution than you may have done previously.

Best wishes, Harry Long
 
Pitlamp

Pitlamp

Well-known member
Speaking of erring on the side of caution, I was one of the other divers to whom Harry refers. I remember being stationed in an airspace section of passage between two flooded sections, with nothing to do for some time. I became fascinated by watching the water level, which was gently going up and down, accompanied by spooky gurglings and banging noises. At one point the water suddenly shifted upwards quite quickly. You'll never see anyone kit up so fast for diving as I did that day.

I'd also add that we've just had a very long and wet winter. Percolation stores within the limestone are well topped up, such that (as Harry says) even a small amount of extra rain (perhaps falling a day or two before a planned trip) could bring it up quickly whilst you're there. Once you're beyond the base of the entrance ramp, where it sumps first, the trap is sprung.

Don't take any chances with the water in Sleets Gill Cave; it does strange things.
 
JasonC

JasonC

Well-known member
langcliffe said:
Personally, I would await for a longish dry spell in the summer - at least a couple of weeks without significant rain.
Click to expand...
Yes, but how many of those do we get ?
My reason for asking was to see if there were conditions outside of a prolonged drought where it would be safe, but I appreciate the cautionary advice above (y) - thanks to Harry in particular.
 
langcliffe

langcliffe

Well-known member
JasonC said:
Yes, but how many of those do we get ?
My reason for asking was to see if there were conditions outside of a prolonged drought where it would be safe, but I appreciate the cautionary advice above (y) - thanks to Harry in particular.
Click to expand...

I am sure that there are. The problem is that because Sleets Gill is primarily fed by autogenic recharge, it can take a few days to react to heavy rain, so one has to be confident about what has been happening within the watershed in recent days. It wouldn't have to be a major event for Hydrophobia to become closed off.
 
wellyjen

wellyjen

Well-known member
harrylong said:
Hi Jason,
One of the major problems with Sleets Gill is not knowing how much water is already percolating down through the overlying limestone in quite a large catchment area. Because of this, a relatively small amount of rain can provide enough extra percolation water to produce flooding in the cave. Equally, a larger amount of rain when the amount percolating already is virtually nil may have no adverse effect in the cave. - hence the unpredictability as there is a big unknown element here.

When Roy Deane and Les Hewitt were trapped at the inner end of The Main Gallery in March 1992 they were obviously there on a day when the odds were in their favour and there was not enough flow to fill The Main Gallery completely. Based on the water level I found at the bottom of the entrance slope and using Dave Brook's highly accurate survey (got from him at a time when he was asleep at home in Leeds!) I came to the conclusion that it was worth getting divers in to see what they could find.

The first 2 divers were Geoff Crossley and Johnny Shaw and although they expected to find bodies they agreed to dive. The rest is history and over a period of time numerous other divers all played a part in equipping and assisting in diving Roy and Les out of the cave.

When I made a visit to the entrance 24 hours later to look for lost gear I found a very large torrent resurging from the entrance and where Roy and Les had sat things out would have been totally submerged.

For a fuller version of events the chapter in the UWFRA book,"Anytime...Anywhere" (If you can find one) gives an insight into various peoples' memories.

So Jason, as you can see there is no ready guide to when it is safe to enter Sleets Gill Cave. My usual method was to see what the state of flow in other adjacent.white water risings was and the volume flowing in Moss Beck and at Kilnsey Crag and then flip a mental coin. Perhaps this hasn't been much help to you but it may make you err even more on the side of caution than you may have done previously.

Best wishes, Harry Long
Click to expand...

Sid Perou's film about this rescue here:
https://caving-library.org.uk/collections/sid-perou-film-40.php
 
Pitlamp

Pitlamp

Well-known member
thehungrytroglobite said:
Haha same, it's been a complete wash out all winter! I keep telling myself that it's got to stop raining at some point, but... when?
Click to expand...
Just in time for your club's GG meet in a few weeks. ;)

But in an attempt to stay on topic, I agree with Langcliffe's point above. Having seen Sleets Gill from the inside when in angry mood, I wouldn't personally think of going in there at the moment.
 
Fatman

Fatman

Member
Pitlamp said:
Speaking of erring on the side of caution, I was one of the other divers to whom Harry refers. I remember being stationed in an airspace section of passage between two flooded sections, with nothing to do for some time. I became fascinated by watching the water level, which was gently going up and down, accompanied by spooky gurglings and banging noises. At one point the water suddenly shifted upwards quite quickly. You'll never see anyone kit up so fast for diving as I did that day.

I'd also add that we've just had a very long and wet winter. Percolation stores within the limestone are well topped up, such that (as Harry says) even a small amount of extra rain (perhaps falling a day or two before a planned trip) could bring it up quickly whilst you're there. Once you're beyond the base of the entrance ramp, where it sumps first, the trap is sprung.

Don't take any chances with the water in Sleets Gill Cave; it does strange things.
Click to expand...
Total respect for you guys on that rescue. Saw the Sid film on Youtube. Put me off ever going down there.
 
I

IanWalker

Active member
@JasonC

Perhaps this website would be of interest for tracking river levels and comparing to historical norms
eip.ceh.ac.uk

UK Water Resources Portal

A web tool for displaying water resources and drought information from the UK Centre for Ecology & Hydrology.
eip.ceh.ac.uk eip.ceh.ac.uk

1711567498524.png
 
H

huwg

Member
I optimistically stuck my head in on the 6th of feb, we got about 2 thirds of the way down the entrance slope to meet a crystal clear static pool. Sobering to see!
There's been a lot of water in wharfedale pretty constantly so far this year, so I personally wouldn't head down for a while. As many wiser than me have said above, it's not just how much rain in the last few days, but how generally soggy the area is too. There were some sensors in sleets gill at one point but not sure if anything came of it?

I've not been up either of the hydro passages yet, but managed a few trips in to the friendly bit last year and know people went through the wharfedale sump with plenty of air space.

One useful rule of thumb I heard is that if there is water flowing out of the wharfedale sump, turn around and get out sharpish!

Didn't answer your question but hopefully something useful in there for you.
 
aricooperdavis

aricooperdavis

Moderator
Brendan Hall has some water level data from Sleets Gill that I tried to use to model the response of the cave water depth to rainfall. There wasn't quite enough data to draw any useful conclusions, but based on that small sample I was able to predict with a high precision whether the cave will be in flood for the next 7 hours based on the last 10 days of rainfall data. So langcliffe's instinct of waiting for a 2 week dry spell is probably spot on.
 
I

IanWalker

Active member
langcliffe said:
Personally, I would await for a longish dry spell in the summer - at least a couple of weeks without significant rain.
Click to expand...
JasonC said:
Yes, but how many of those do we get ?
My reason for asking was to see if there were conditions outside of a prolonged drought where it would be safe
Click to expand...
I was intrigued by this so downloaded the rainfall data for Malham Tarn, which is nearby, approximately the right location and elevation for the Sleets Gill catchment. There is a daily rainfall records for 1983 onwards.

Hydrology Data Explorer

environment.data.gov.uk environment.data.gov.uk

I summed it up in two week intervals (i.e. for every day that you could go caving, what is total rainfall in past 14 days). The number jumps around a lot (presumably because it rains on many days), from around 0mm/14days to ~300mm/14days

1711594188835.png


I then sorted these numbers in ascending order (to group the low values together for counting). I did a plot of that too. About 1800 days had 10mm or less over preceeding 14day period. Out of 14470 data points thats 12% of the time. Which surprised me a bit. I guess it shows how variable the rainfall is (i.e. its not 'always' raining).

1711594332054.png


I then wondered if all of these 'dry' days were next to each other, or appearing regularly and independently. I also wanted to isolate the last 5 years (say) to discount older rainfall trends that might no longer be relevant. The graph below shows that "two weeks with 10mm or less rain" occurs 18 times in the last 5 years (average once every 3 months), but you might wait a year for the next one.

1711594927072.png


My conclusion is it varies a lot and keeping an eye on the weather and river levels is a good idea. But I'm not a scientist / geographer / analyst / mathematician so if anyone else has insight I would be glad to hear it. I cave in Wharfedale so this has a practical use.
 
langcliffe

langcliffe

Well-known member
IanWalker said:
I was intrigued by this so downloaded the rainfall data for Malham Tarn, which is nearby, approximately the right location and elevation for the Sleets Gill catchment. There is a daily rainfall records for 1983 onwards.

Hydrology Data Explorer

environment.data.gov.uk environment.data.gov.uk

I summed it up in two week intervals (i.e. for every day that you could go caving, what is total rainfall in past 14 days). The number jumps around a lot (presumably because it rains on many days), from around 0mm/14days to ~300mm/14days

View attachment 18896

I then sorted these numbers in ascending order (to group the low values together for counting). I did a plot of that too. About 1800 days had 10mm or less over preceeding 14day period. Out of 14470 data points thats 12% of the time. Which surprised me a bit. I guess it shows how variable the rainfall is (i.e. its not 'always' raining).

View attachment 18897

I then wondered if all of these 'dry' days were next to each other, or appearing regularly and independently. I also wanted to isolate the last 5 years (say) to discount older rainfall trends that might no longer be relevant. The graph below shows that "two weeks with 10mm or less rain" occurs 18 times in the last 5 years (average once every 3 months), but you might wait a year for the next one.

View attachment 18900

My conclusion is it varies a lot and keeping an eye on the weather and river levels is a good idea. But I'm not a scientist / geographer / analyst / mathematician so if anyone else has insight I would be glad to hear it. I cave in Wharfedale so this has a practical use.
Click to expand...

I think that is a worthwhile analysis, although I think you can double the amount of rain permitted during the months with higher evapotranspiration.
 
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