Lancaster Hole and Fall pot flooding, beware!!

[Pitlamp]

Fulk raises a very good point about understanding the physics of floatation / swimming. I reckon it all boils down to whether you - and each item of your gear - is negatively buoyant or positively buoyant. Whether you actually sink or float is the overall effect of the the bouyancies of everything combined.

Two main forces act on a floating object; weight (a downwards force) and upthrust (an upwards force). If the upthrust is greater than the weight, you float. If the reverse is the case, you sink. Anything negatively buoyant attached to you contributes to weight in the water and everything positively buoyant in the water contributes to the upthrust stopping you sinking.

It follows that blaming a single item (e.g. wellies) is unhelpful - a better approach is to try to minimise the number of negatively buoyant items and increase the number of positively buoyant items, such that the overall effect is that upthrust beats weight. If the nature of the trip dictates that items of gear attached whilst you're swimming results in weight being greater than upthrust then you have two choices:

1. Don't do the swim.

2. Wear a buoyancy aid to uncrease the upthrust, thus counteracting the weight.

It's worth aiming for overkill on upthrust because it's not just a case of sink or float - it's a case of how far your mouth and nose are out of the water (the greater the buoyancy the higher you'll float in the water). So my advice would be - unless you've previously tested a particular combination of kit in safe water - WEAR A FLOATATION DEVICE.

You can, of course, contribute to upthrust by making swimming movements - but this is tiring and if you become very fatigued (which can happen alarmingly fast in the wrong circumstances) then the default is that you sink, sooner or later - which is never a good outcome.

Just to answer a point Dunc raised above in a bit more detail - If you go to Leck Beck Head you'll find a large depression in the valley just behind the flood risings. This is probably a large truncated entrance, now filled with vast volumes of boulder clay, from when the Ease Gill river resurged at a higher level (probably before the last glaciation). This drops straight into the present day active flow. I used the term "drops in" deliberately because the resulting hanging choke regularly collapses in massively, hence the arrival of many new boulders all of a sudden. It was this enormous hanging choke which defeated us in the underwater section of Leck Beck Head and I reckon this could, at least in part, explain why the water level rose so alarmingly fast in Lancaster at the weekend.

Just as a matter of interest, exactly the same situation exists at Brants Gill Head on Penyghent, where a similarly large shakehole connects via a choke with the submerged passage not far in from the dive base. So take care in wet weather if you're ever in the lower parts of Penyghent Pot!

 

[Fulk]

quote from Bottlebank:

A pound of lead and a pound of wet fleece are exactly the same weight.

Of course this is obviously true, but it's not quite as simple as that. As Pitlamp points out, whether you sink or float depends on the difference between weigh acting down and upthrust of water displaced.The density of lead is ~11 g /cc in round figures, so 1 cc of lead in air weighs ~11 g. If you suspend it in water, then it displaces 1 cc of water, which weighs 1 g . . . hence the 'weight' of 1 cc of lead in water is ~10 g. So it goes straight down. If you have a wet furry, then probably most of the weight is in the water it holds, so if you then submerge that, you have water displacing water. So it gets a bit complicated . . . the bottom line, I'm sure, though, is that we're all agreed that swimming in standard caving kit without some kind of buoyancy aid is not a good idea.

How about wearing a wetsuit, with its inbuilt buoyancy? I suppose it depends on how thick it is, and how much 'upthrust' it has when in water?

 

[adep]

adep:

Crossing from Montagu East to West, the water level was about 15ft below the lowest point of the crossing

I'm not sure I understand this; as far as I am aware, Montagu East is the big passage that leads to Easegill while Montagu West is the somewhat smaller continuation that goes to Waterfall Passage . . . which doesn't fit with your description of crossing from E to W . . . do you mean, perhaps, crossing the Main Stream at Stake Pot? Or have I got it all wrong?

Am reffering to the passage that crosses at Stake pot which is as far as I know Montagu east and west??

 

[adep]

P.S. many thanks to the O.P. for providing the information, it's important that we're all made aware of such things.

Thanks for your very interesting input re the boulder chokes, and yes I agree its all about learning and taking heed hence my reason for placing the post on here, as far as I can gather the speed of this flood seems to be far faster than people would have expected

 

[adep]

That was my point to our guy, think your SRT kit weighs in the region of 12kg in total

My SRT kit, including bag & harness, weighs under 3 kg. What are you putting in yours?

I suspect the main problem is the general difficulties of swimming in caving kit, especially in challenging circumstances. Nevertheless a few extra kilos makes it worse, and entanglement in your SRT kit could be a hazard too.

I havent actually weighed it for myself, but that's what I understand it to weigh including oversuit, furry suit helmet SRT bits and bobs, you put it all in a bag and weigh it, I bet its not far off 10~12 kg

 

[adep]

After seeing the video confirms my thoughts that if we hadn't talked my mate out of swimming across then we would have been dealing with a dead un, it was only by telling him that we would not be able to do anything to help him and would not come in for him if he got into trouble that stopped him from attempting it!!

 

[Pitlamp]

P.S. many thanks to the O.P. for providing the information, it's important that we're all made aware of such things.

Thanks for your very interesting input re the boulder chokes, and yes I agree its all about learning and taking heed hence my reason for placing the post on here, as far as I can gather the speed of this flood seems to be far faster than people would have expected

It does indeed sound that way. Glad you came out of it OK mate!

 

[Fulk]

Hi adep, by querying your remarks about the location, I wasn?t trying to be a smart-ass ? just trying to pin down where you were. I?ve just checked with NC-3, and it talks about ?The way on from Bill Taylor?s Passage  . . . leading to the vastness of Montagu East where it encounters Fall Pot. A careful traverse round to the left . . . leads to the start of Montagu West.?.

 

[adep]

Hi adep, by querying your remarks about the location, I wasn?t trying to be a smart-ass ? just trying to pin down where you were. I?ve just checked with NC-3, and it talks about ?The way on from Bill Taylor?s Passage  . . . leading to the vastness of Montagu East where it encounters Fall Pot. A careful traverse round to the left . . . leads to the start of Montagu West.?.

Wasn't taken that way so no worries, I might be wrong on the naming but there is no mistaking the large high level passage out of Fall pot, which I took as being Montagu west??, not had chance to check the survey

 

[kay]

That video is fascinating . . . and sobering . . . and a bit scary.

One thing I have a problem with is the physics behind some of this stuff. For example, it's often said that wellies full of water will drag you down; but why? The water in your wellies is displacing . . . err . . . water, which has the same density as does that outside your wellies. So why does it drag you down?

I can see that they would drag you back. Instead sliding smoothly through the water, you have the tops of the wellies biting into the water acting like a drag anchor used on boats when there isn't a suitable bottom to put a conventional anchor into. So I wonder if the drag would be any less if you have your oversuit over your wellies?

I think it's more that as the weight of them is at the end of your leg, dragging them through the water is quite hard so might be better to take them off and carry them, I wonder if they how long they would stay a float if you put them in upside down?

Personal survival swimming classes that a lot of us did at school taught how to trap air in clothing to make a rudimentary float. Presumably wellies held upside down to stop the air escaping would act as a float, but they'd be a bit unmanageable!

Human buoyancy is iffy at the best of times. If you float on your back, the waterline is somewhere between your ears and the corners of your eyes, and it takes effort to stay flat and not sag in the middle. So it doesn't take much to tip you into sinking. Vertically in the water, you won't float (unless you actively "tread water"). As Pitlamp indicates, generally the more horizontal you are, the more buoyancy you have, and the more of your effort goes into getting across the water rather than keeping at the surface of it. So buoyancy aids are a good idea.

 

[adep]

That video is fascinating . . . and sobering . . . and a bit scary.

One thing I have a problem with is the physics behind some of this stuff. For example, it's often said that wellies full of water will drag you down; but why? The water in your wellies is displacing . . . err . . . water, which has the same density as does that outside your wellies. So why does it drag you down?

I can see that they would drag you back. Instead sliding smoothly through the water, you have the tops of the wellies biting into the water acting like a drag anchor used on boats when there isn't a suitable bottom to put a conventional anchor into. So I wonder if the drag would be any less if you have your oversuit over your wellies?

I think it's more that as the weight of them is at the end of your leg, dragging them through the water is quite hard so might be better to take them off and carry them, I wonder if they how long they would stay a float if you put them in upside down?

Personal survival swimming classes that a lot of us did at school taught how to trap air in clothing to make a rudimentary float. Presumably wellies held upside down to stop the air escaping would act as a float, but they'd be a bit unmanageable!

Human buoyancy is iffy at the best of times. If you float on your back, the waterline is somewhere between your ears and the corners of your eyes, and it takes effort to stay flat and not sag in the middle. So it doesn't take much to tip you into sinking. Vertically in the water, you won't float (unless you actively "tread water"). As Pitlamp indicates, generally the more horizontal you are, the more buoyancy you have, and the more of your effort goes into getting across the water rather than keeping at the surface of it. So buoyancy aids are a good idea.

Maybe if you were desperate enough and had to swim you could take off your caving suit knot the arms and legs and try and inflate them and knot them again to trap the air, this of course assumes that you don't have any holes in your suit (not likely) and you could knot them/seal them, again not very likely, if you have a survival bag which we all should have, you could inflate that, reckon that would be your best bet.

I think the biggest hazard of trying to swim with wellies on is that they would act as a scoop and have a counter effect on your forward motion, definitely reckon putting your oversuit over the wellies would help reduce this but at the end of the day, caving suits are by design baggy so would cause drag especially in currents

 

[Alex]

Yep, a boyancy aid made the 300m of swimming in Spain a far easier and safer prospect, though my mates managed without, though one did use daren drum in a tackle bag as an alternative. If you don't have a boyancy aid try to keep your individual swims below 10ft using the walls as much possible, so you can use momentum to get yourself accross the water, only porblem is a suitable hand hold or shallow enough water, is not always available.

I don't find that I can swim any better in a wetsuit under an oversuit then a furry under an oversuit, seems about the same. I guess there would be a difference if you take the oversuit off, the wet suit would of course perform better, not least because its more sleek and won't have the drag.

Like other posters I find it almost impossible to raise my legs with wellies on and kick out and tend to rely on my arms, unless my boyancy is high enough i.e. rubber ring and life jacket in DYO green canal, in that situation I found I could use my legs and get some speed on, I guess the boyancy around my waste was enough to counter the drag of the wellies.

I would think another option  if your lacking a boyancy aid is to stuff your wellies in a tackle sack and carry it on your back, yes this would not remove negative boyancy but you do remove the drag and put the weight in a central location, like on a ship most of the weight is in the middle. If your wearing an wet suit take the oversuit off too and stick that in the bag too, though this is theroey I have not tried this.

 

[Pete Brookdale]

Hi adep, by querying your remarks about the location, I wasn?t trying to be a smart-ass ? just trying to pin down where you were. I?ve just checked with NC-3, and it talks about ?The way on from Bill Taylor?s Passage  . . . leading to the vastness of Montagu East where it encounters Fall Pot. A careful traverse round to the left . . . leads to the start of Montagu West.?.

Wasn't taken that way so no worries, I might be wrong on the naming but there is no mistaking the large high level passage out of Fall pot, which I took as being Montagu west??, not had chance to check the survey

Montague West is left when you duck under the boulder, Fall pot Area straight on, with Monatgue East down and up the other side where you were trapped. Montague South is off Skittle alley in the Graveyard Area

 

[kay]

Personal survival swimming classes that a lot of us did at school taught how to trap air in clothing to make a rudimentary float. Presumably wellies held upside down to stop the air escaping would act as a float, but they'd be a bit unmanageable!

Maybe if you were desperate enough and had to swim you could take off your caving suit knot the arms and legs and try and inflate them and knot them again to trap the air, this of course assumes that you don't have any holes in your suit (not likely) and you could knot them/seal them, again not very likely, if you have a survival bag which we all should have, you could inflate that, reckon that would be your best bet.

Oh, I wasn't suggesting that one could take off bits of caving kit and tie knots in the arms and legs! I suppose, by buoyancy aid, I was thinking of something like an inflatable plastic dolphin. (While I'm not suggesting it's part of most caver's normal kit, I have known of one being taken into Smeltmill Beck)

 

[GT]

We did a bit of swimming around in the kit (which isn't in the video). It was a lot easier swimming in the Cordura over-suit than the Vinyl, not that either were that easy! An air bubble built up on the back of the over-suit behind the shoulders as we swam providing a bit of buoyancy, although this reduced as time went on. It completely disappeared as we rolled over onto our front (with an amusing trail of bubbles) shortly followed by sinking like a lead ballon!

 

[topcat]

I appreciate that it is not quite the same but when coasteering I cross zawns using my Watershed dry bag as a PFD.  The Watershed bags are very tough and 100% waterproof / air tight, assuming you fasten them correctly.  I use the same sack for my safety sack when caving, but still wouldn't be keen on using it wearing SRT kit.
I wear it on my front or back, and swim the same way [ie, worn on back, swim on back], but there is a serious risk of being turned over which can be troublesome!
I also employ the same idea when climing on sea cliffs, ie carry a bouyant sack. And I rack my kit on a quick-ditch bandolier which I hate for climbing with, but the tought of falling off a ledge or being swept off by a wave with a full rack individually clipped to my harness doesn't bear thinking about.  Well, actually it does bear thinking about....that's why I don't do it!

 

[adep]

I appreciate that it is not quite the same but when coasteering I cross zawns using my Watershed dry bag as a PFD.  The Watershed bags are very tough and 100% waterproof / air tight, assuming you fasten them correctly.  I use the same sack for my safety sack when caving, but still wouldn't be keen on using it wearing SRT kit.
I wear it on my front or back, and swim the same way [ie, worn on back, swim on back], but there is a serious risk of being turned over which can be troublesome!
I also employ the same idea when climing on sea cliffs, ie carry a bouyant sack. And I rack my kit on a quick-ditch bandolier which I hate for climbing with, but the tought of falling off a ledge or being swept off by a wave with a full rack individually clipped to my harness doesn't bear thinking about.  Well, actually it does bear thinking about....that's why I don't do it!

Very worthwhile suggestions, and I do exactly the same whilst climbing on anything above water