Sorry to be a pedant, but it's not a sinkhole. The canal embankment has failed, leaving that section of canal to drain into the field below it. It happens once or twice each year apparently.
I'm surprised it doesn't happen more often, the level of maintenance done is very inadequate. There is a section of canal near me that has a 200m of towpath that is about 1m lower than the surrounding towpath (and indeed lower than the water level in the canal), there is constant water leakage and failure is only a matter of time. CRT came and surveyed it about two years ago. I chatted briefly to the surveyor, who agreed that it looked "a bit dodgy". Needless to say nothing has been done. It is just a matter of time before it fails. That section of canal is 4.45km long, lock to lock. A quick "back of a fag packet" calculation suggests that when it goes, it will be over 30,000 tonnes of water dumped into the valley below. There is a liveaboard family on a permanent mooring opposite, and dozens of other liveaboards in that section of canal, on either permanent moorings, or on a transient basis. There are houses and business in the valley who will be impacted. The West Coast Mainline is just metres away, on an embankment above the canal. It is not inconceivable that the removal of the water pressure could cause the railway embankment to move, though not likely.
The canal were built almost three hundred years ago, by itinerant navvies with shovels, as directed by (generally) good engineers, but they were in a hurry, and the funding was often lacking. It's amazing they are still in as good a condition as they are. I'm sure if you had asked anyone involved at the time they would have said the lifespan would be 50 odd years. The whole network is crying out for proper maintenance.
But no, sorry, not a sinkhole.
www.bbc.co.uk
