Author Topic: Makita Drill - Trip Report: Unexpected Floods  (Read 1062 times)

Offline Bratchley

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Makita Drill - Trip Report: Unexpected Floods
« on: May 11, 2016, 06:47:23 pm »
More of a dive/cave diving trip report and so it's written in that fashion (3rd person):

14th November 2015
Site: "The Sump" (Rising Sump), OFD 1
Diver: myself

So I'd done multiple recce dives to this area as it was hoped that the sump might lead to dry passage in blank space on the southern side of the OFD streamway, it was still shallow (around 10m) and although the source of the water emerging from it was known (Downstream Dip sump) there was a lot of space between. This dive was to see what conditions were like in slightly higher than "low" flow, as being able to work in slightly higher water would mean more time for exploration and less wasted days waiting for water levels to drop to absolute minimums as the sump was assumed to be too tiring in all but the lowest flow.

Myself and one other (Ellen, kindly carrying a bag of neoprene and regulators) made our way to OFD1. The weather had been damp overnight, there had been rain the day previously but only light, although continuous. The streamway, even with it still drizzling, should have been dropping and there was no forecast change for at least a day.

We headed in and gradually worked our way upstream towards the sump. Two stops were made on the way to check water levels, as well as upon first entering the stream at the step. All indications were as expected, a lowering water level, lovely!

Upon reaching the sump we dropped the bags and cylinders (2 x 3L) and re-checked levels. There was a reasonable flow emerging from the sump but nothing crazy. Due to the weather and my general cautionary ways I persuaded Ellen to wait for me at the top of Low's chain, above the flood bypass, as she'd only have been waiting at the sump pool anyway so it made little difference except for in the off chance the forecast was wrong.

I kitted up at the sump after helping Ellen up the climb and then entered the water. The flow was strong, as expected, requiring reasonable effort. After making it about 20m into the sump, my thoughts were that these conditions, if a bit lower, would be doable and perhaps by the middle of the day it could be workable.

During this decision making process a significant, rapid increase in the current was noticed. The visibility went from 2-3m to very little in extremely tannic water in very little time. Concerned, I began a hasty exit, bracing to slow the ascent into the shallows and by the time I neared the surface my exit speed from the sump pool was hard to control. I ended up in the side of the streamway - and it was much higher than when I went in only ten minutes before.

A hasty, tiring retreat to Low's Chain was made in full kit against a very strong, still increasing flow. No time was available to de-kit in the flood bypass and so I climbed up Low's chain and dekitted at the top, whilst watching the streamway become a raging torrent within a few minutes of me climbing up.

The round trip had to be completed with all the dive gear in order to exit from the cave dry, a rather fun route. By the time we got back to seeing the streamway and after checking out Gothic passage on nearing the exit, the water levels had decreased considerably and had left lots of foam around the place.

I had suspected a bog burst upon seeing the sudden rise and after discussion with SWCC members after the trip they agreed it must have been. Looking at the data on the water gauge in the streamway showed an extremely rapid rise and lowering straight after.

Others had also been in the streamway but had either left it by the time the water started to rise or were near a streamway exit. A couple of parties attempting the round trip in reverse had to turn back. No-one injured and overall a very interesting day.
I like caves.

Offline ah147

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Re: Makita Drill - Trip Report: Unexpected Floods
« Reply #1 on: May 11, 2016, 07:05:27 pm »
Boo! Stories aren't a story without an injury


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Offline caving_fox

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Re: Makita Drill - Trip Report: Unexpected Floods
« Reply #2 on: May 12, 2016, 09:15:04 am »
What's a "bog burst"? how does it happen? when?
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Offline AR

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Re: Makita Drill - Trip Report: Unexpected Floods
« Reply #3 on: May 12, 2016, 09:40:12 am »
It's where water builds up in peat on a hilltop or hillside during or just after heavy rain, and it can't drain through its usual outlets fast enough; eventually a weak spot in the peat bed, generally on a slope, gives way and the backed-up water comes out in a rush.
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Offline Roger W

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Re: Makita Drill - Trip Report: Unexpected Floods
« Reply #4 on: May 12, 2016, 11:53:23 am »
Years ago now, a chap I knew was driving somewhere near Glossop when he was caught by a bog bursting.  He said the dry stone wall beside the road suddenly gave way and the road - and his car - was flooded by a couple of feet or so of very muddy water.  He managed to wade to safety, but his car never recovered...    :(
"That, of course, is the dangerous part about caves:  you don't know how far they go back, sometimes... or what is waiting for you inside."   JRR Tolkein: "The Hobbit"