Sion, as Minion says this has nothing to do with the water going down the slot. The engineering bricks are a work-in-progress towards supporting the huge boulder that forms the roof at that point. The stream is washing away the shale wall on stream left, additional support for the increasingly undercut boulder was considered prudent. Further walling to be added, if you would like to try your hand at neat tidy underground brick laying please feel free to join us on Thursday evening
. If you dont fancy that the next time you are coming up the wet slot, facing the stream flowing towards you, look up and to your right and wonder what is holding up the roof you are about to crawl under.