Biggest bores

It's a little like the breezy way people say'Hoover” when they mean “vacuum cleaner”. Most people who think about tidal bores in rivers think about the Severn Bore. It is seen at its highest, with a good one being over 2m high, in Gloucestershire. But there are plenty of others. On the I rent in England there is one called the Aegir, named after a Norse water god.

The world's highest bore is called the Hangzhou and occurs on the Qiantang River in China, where surfers enjoy trying to stay on a wave that is anything from 7m to 9m high. The Mascaret on the Seine is much smaller, perhaps 2m. But it was as much as 6m high, second only to the Hangzhou, until river engineering works were carried out to modify it and reduce the damage it was doing. Also in France, the Garonne and Dordogne have notable bores. Perhaps the most persistent bore is that found on the Pungue River in Mozambique, which has been observed 80km inland.

Probably the most water is carried on the comparatively modest 2m high Pororoca – because it is a bore on the Amazon, the world's greatest river. Of other super-rivers, the Ganges also carries a bore, described by George Darwin, the British physicist and son of Charles.