A vocabulary of landscape — a landscape of words
1367 entries
tidal bore
A tidal bore is a wave that travels up a river against the current on a rising tide. It forms where a large tidal range meets a funnel-shaped estuary with a shallow shelving bed, so the flood tide is compressed until the front of it steepens into a breaking wall. Some are a few inches high and some are several feet, and they can run many miles inland at walking or running speed.
Etymology
The word came into English from Norse, where it meant a wave or a swell. It is unrelated to the bore that means to drill and to the one that means a tedious person. Bores have their own names on their own rivers: the Severn has the Severn Bore, the Amazon has the pororoca, from a Tupi word, and the Qiantang in China has the largest in the world.
Notes
Around eighty rivers worldwide produce them and the conditions are exacting enough that dredging or barrage construction has destroyed several. The Severn Bore has been surfed since 1955 and rides of several miles have been recorded. The Qiantang bore can reach thirty feet and draws crowds who have watched it from the same viewing points for over a thousand years.