Waterfall of Moss chockstone

Sharing details when things go wrong to make canyoning safer.
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Ganguddy Goodoo
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Full name: Steven Halpin
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Waterfall of Moss chockstone

Post by Ganguddy Goodoo » 11 Nov 2019, 11:49

This probably doesn't count as a near miss but maybe worth raising.

A mate and I did Waterfall of Moss yesterday after attending the festival. My friend rigged the second last abseil with the rope going over the big chockstone. When he climbed over the top to start the rap the thing moved. The climber in me wanted to pull the ropes up and trundle the thing but I didn't want risk making a potential time bomb any worse. I'd appreciate people's views on the following;

1) What is the normal way to rig this abseil ... over the chockstone or do people squeeze through the hole behind it (looked tight for a fat bloke like me but much kinder on your rope).

2) Has this chockstone always moved or is this a recent thing. I swear the thing was moving further down and out and not just rocking a bit, although that could have been an optical illusion.

What do you reckon?



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T2
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Re: Waterfall of Moss chockstone

Post by T2 » 11 Nov 2019, 12:52

Steven,

Thanks for sharing that experience. I've not been through Waterfall of Moss, so can't comment on the specific chockstone, but I will provide some general thoughts.

It popular canyons, with lots of traffic, there usually aren't a lot of loose rocks and logs (because all the usage causes them to roll or move into more secure positions). The more remote, less visited an area, the more likely you will face these challenges. On really remote, exploratory stuff, it's a very common issue. I have come to drops where loose rocks, logs, and other debris actually make up a metre or more of ground before the drop (all hollow underneath and a massive danger). Some kicking and pushing usually identified how much of this is dangerous and needs to be cleared. It's obviously important to do this before rigging ropes and while no one is down below. Going over the edge can often result in lots of awkward and unusually forces being placed on objects, both from the abseiler standing / pushing on them, and the force of ropes running across them. Less experienced abseilers with poorer techniques will often put more pressure on these objects. So clearing objects that are likely to break free or fall is very sensible and advisable.

On the other side, just because something moves, doesn't mean it is actually at risk of breaking free and falling. It's usually possible to rock an object back and forward and see if there's something in the geometry of where it is lodged that will prevent it from fully rolling, and therefore dislodging and falling. It can be quite disconcerting when a chockstone shifts a little, but if it is in a position where it can't actually break free, it isn't a significant danger. Sometimes in these situations you can simply wedge one or more smaller rocks in specific places to stop the chockstone from moving. I've been known to do this on occasion.

But I don't know this chockstone, and don't know if erosion or other changes have let to it becoming dangerous. So like any drop, my advice would be to always assess potential dangers at every drop and consider appropriate steps to mitigate them.

Ganguddy Goodoo
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Full name: Steven Halpin
City: Canberra
State: Australian Capital Territory

Re: Waterfall of Moss chockstone

Post by Ganguddy Goodoo » 11 Nov 2019, 18:31

Hi T2 I did try and post a reply but it didn't seem to come through. My apologies if a similar message comes through twice.

Anyway some good advice there. The chockstone in question is a big unit (think tonnes). If you are interested you could google the canyon and it would be easy to find a photo of it in the various trip reports floating around. Look for one of the 6th or 7th abseil with obvious rope grooves in the top of the chockstone. The chockstone looks bomber from above but is less inspiring when examined from the side and below as it sits above a bomb bay flare. In this case traffic may actually be wiggling the thing loose. Its probably ok but it would be good to hear other people's opinions.

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JulieB
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Re: Waterfall of Moss chockstone

Post by JulieB » 20 Nov 2019, 11:21

I did WOM back in January. We went over the chockstone, but none of us noticed any movement in it then.
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Flynny
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Re: Waterfall of Moss chockstone

Post by Flynny » 04 Dec 2019, 15:18

I’ve had another report that the big chock Stone at the top of the second last abseil in Waterfall of Moss is loose. Party on the weekend did their best to dislodge it but it dropped 50mm and wedged again. still able to be seesawed but could not shift it further.

If the park ever reopens use extreme caution if doing this canyon. Rock would weigh in the region of 2t. There is a bit of a ledge you can traverse on the right. Might need to look at alternate anchor options.

Definitely would not be bottom belaying from anywhere near the bottom of it.

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