I'm currently working on an EA job on the River Yarrow in Croston near Chorley, and which runs into the Ribble a few miles further downstream so it's affected by tides, and we've got conveyors on scaffolding 2.5m above the river - we had to strip them all out yesterday morning 'just in case', and it peaked at 2m exactly last night - so it wasn't strictly necessary, but they were on hire, so it was.