Harbour scouring to remove silt

Several times in the month when the tides are on springs the Cumberland Basin (bigger than a football pitch) is totally emptied into the river Avon at low tide. Then the outer lock gates are closed and the Junction Lock (inner gates of the Basin) have their sluices opened and this is the result. The roaring sound is amazing and I never cease to enjoy watching and marveling at the engineering that enabled this harbour to be built.