Risk posed by autoblock in wet canyons

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T2
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Risk posed by autoblock in wet canyons

Post by T2 » 15 Dec 2020, 13:15

I bumped into a young couple at the end of Empress Canyon recently and watched them descend while sending my group down the other anchor. One thing in particular made me quite nervous, and I thought it might be a good learning experience for others.
One of them was clearly more experienced, while the other was a beginner. The beginner got quite cold at the top of the abseil while it was being rigged (wearing a wetsuit, which in a windy spot like that actually makes you colder). By the time they got on rope, they were cold and feeling quite nervous. They ended up coming back from the edge as a result. The more experienced person then rigged an autoblock from the beginners leg loop before sending them down (they were using the abseil anchor that takes you directly through the water flow).
I understand wanting to provide an extra sense of security for a cold, nervous beginner, but this is simply the wrong tool in that setting. A nervous beginner with an autoblock in flowing water is a recipe for getting stuck. At best, they'd be very cold while the experienced person found a way to get to them to help. At worst, getting stuck in flowing water could quickly lead to drowning. Autoblocks in flowing water are extremely dangerous, even for experienced canyoners. For a beginner, it's even worse.
They had two 30m ropes, so a better solution would have just been to use the pull side as a top belay. The nervous, cold beginner would have extra security, but the chance of them getting stuck in the waterfall would be removed. If they really freaked out, they could simply be lowered.
I just thought I would share this experience to hopefully get others to think more about how they manage risks and modify their rigging to deal with different experience levels or other issues in canyons.

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T2
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Re: Risk posed by autoblock in wet canyons

Post by T2 » 15 Dec 2020, 13:26

Further to this, I understand that the use of an autoblock (or "third hand") is common in rock climbing. Climbers often think abseiling is the same, regardless of where you do it. Unfortunately, canyons have unique risk factors, making some techniques from climbing inefficient, and others downright dangerous.
The idea behind an autoblock is to reduce the risk posed if someone let go of the rope while descending. In a climbing setting, the worst case scenario is your autoblock is hard to release, but at least you won't fall. In a canyon, particularly one with flowing water, the risk of drowning significantly shifts the pros and cons of this approach.
It's also worth noting that there are many examples from around the world of autoblocks failing. This is usually because when someone loses control or freaks out, they grab the rope, which prevents the autoblock from gripping. So in many cases all it achieves is a false sense of security, while doing nothing to reduce risk.
Using an appropriate, canyon specific descender with variable friction is a great way of reducing risk because it makes it harder to lose control, and reduces how fast you can go even if you do. A top or bottom belay can provide additional security for less experienced people.
It is really important to build up your knowledge of the unique risks posed by canyons, and built up an extensive toolbox of techniques so you can choose the most appropriate rigging solution to address the specific situation, experience levels of the group, etc.

P.S. I didn't have this conversation in the canyon because I'd already mentioned something else to this group. I was nervous about being one of those old white guys who's always trying to tell people how they should be doing things. It's a challenge to decide when to intervene.
Myself and another experienced person deliberately hung back to last so we could assist if they got into trouble. We could have helped if they got stuck, so it wasn't going to be catastrophic this time.
If the canyoners in question see this, feel free to get in touch. I'm happy to discuss further in private.

Jakub
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Re: Risk posed by autoblock in wet canyons

Post by Jakub » 03 Jan 2021, 09:15

Great post!
It can definitely be difficult approaching people when you don't see best practice going on, especially more then once.
Myself and a few canyoning/climbing buddies have done some training scenarios with autoblocks in different configurations and different diameters with the idea to see how easily they jam ect and it really doesn't take much in the right circumstance.
Although solving this problem is easy enough, for a newbie or even someone experienced under pressure it would absolutely be a nightmare.

A rigging technique we have started to use, especially when there is someone new/less confident (and feel free to discus the pros/cons about this) is setting up a munter hitch with a mule over hand where feasible. We have used this on waterfall repels (no autoblock used, but just incase something was to jam into the device for any reason ie hair) and also on dry repels, where an autoblock is used but the person doesnt have the ability to self rescue.

It does take a bit more time for rigging and then re rigging for last person down but its a tiny time investment for safety.

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Re: Risk posed by autoblock in wet canyons

Post by Skinner » 03 Jan 2021, 09:43

Totally agree T2. (Been a while since I have checked in with this forum)
I think an auto bloc should only ever be used by an experienced person on a dry abseil. They are fiddly and you need experience with them. I would never use any sort of Prussik block on a wet abseil. Anyone who has been stuck on a rope under a waterfall doesn’t want to repeat that experience. I would have used one of the lines as a top belay if there was only 2 of us and one was inexperienced.

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