A curious occurrence associated with the lower reaches of the Severn is the tidal phenomenon known as the bore. The river’s estuary, part of the Bristol Channel, has the second largest tidal range in the world – about 15 metres, exceeded only by the Bay of Fundy in Canada – and at certain combinations of the tides, the rising water is funneled up the estuary into a wave that travels rapidly upstream against the river current; enthusiasts even attempt to surf along on the wave.
Surfing The Bore (Note that the Gloucester Harbour Trustees, as competent harbour authority for this part of the river, explicitly advise against this pastime.) The Severn Bore is a natural example of a self-reinforcing solitary wave or solition. The bore forms somewhat upstream of the Port of Sharpness, which is also the Southern terminus of the Gloucester and Sharpness Canal.