A tidal wave is a wave that is caused by the tide and moves upstream from an estuary . It is found on the lower reaches of practically all rivers that flow into seas with a clear tidal range. Particularly noticeable are extreme forms called strikers or bores (from English bore , "boring, drilling"). Tidal waves shouldn't be confused with tsunamis . (These are triggered by other phenomena and are not tied to estuaries.)
At high tide , water is pushed into a river and a wave or several waves are created which run against the direction of flow of the river and whose water level deflections are above the calm water level.
The extreme form, the flood surf or Bore, is only observed in a few places worldwide. It is restricted to areas where the tidal range is particularly large. Certain tides and mouth shapes can promote their formation. Boren can either appear as a single breaking wave or be followed by several smaller waves. Larger specimens can be dangerous for shipping , but also pose a challenge for surfers .
Rivers on which tidal waves occur
Boren is known to occur in 67 places worldwide.
- Brahmaputra , Bangladesh
- Kampar , Sumatra , Indonesia
- Indus , Pakistan
- Qiantang , China , where the world's largest tidal wave, the so-called “Silver Dragon”, occurs at 8 to 9 meters. In late August or early September, the Bore flows into Hangzhou Bay and rolls up the Qiantang River towards Haining at a speed of 25–40 kilometers per hour.
- Amazonas , with low water flow in February / March at spring tide, can grow up to 5 meters high and up to 65 kilometers per hour. The wave, called Pororoca (great noise) by the Indians because of its loud rumbling , rolls up to 800 km (town of Óbidos ) upstream. It has been surfed on since 1996.
- Petitcodiac in the Bay of Fundy , New Brunswick , Canada , formerly the largest tidal wave in North America, up to 7.5 meters high. However, after the construction of a road embankment in 1968 and the silting up of the river as a result, it is now much smaller.
- Shubenacadie River , also in the Bay of Fundy, Nova Scotia
- The Turnagain Arm of Cook Inlet , Alaska , up to two meters high and speeds up to twenty kilometers an hour
- Dee , Wales / England
- River Mersey , England
- Severn , Wales / England; up to 2 meters high
- River Trent , and other tributaries of the Humber in England
- River Parrett , England
- River Kent , England
- Great Ouse , England
- Eden , England
- River Esk , Scotland
- Gironde and Garonne and Dordogne , France
- Baie du Mont Saint Michel in Normandy, France, where the Sélune, Sées and Couesnon flow together into the bay
On the Seine (France) there was a significant tidal wave (“le mascaret”) until the 1960s, but it was practically destroyed by dredging. Weaker tidal currents on the Weser ( visible as far as Bremen- Vegesack ) and the Elbe as well as on the Ems after almost every low water . On the Ems it was referred to as the Bare in the 19th century .
- Video of a tidal wave in Sumatra (accessed April 27, 2011)
- Brockhaus: What is not in the lexicon 2008
- 9 meter mega-wave pulls people into the river , wetter.at, from August 18, 2014 (video)
- Surfing the pororoca. ( Memento of the original from April 17, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. amazingstuff.co.uk, July 26, 2011.