Bore hitting the riverbank in 1994

The Severn bore is a tidal bore seen on the tidal reaches of the River Severn in England.^[1] It forms somewhat upstream of Sharpness, and can be seen as far upstream as Maisemore.

[edit] Formation

The Severn Estuary, which empties into the Bristol Channel, has the second largest tidal range in the world — about 49 feet (15 m),^[2][3] exceeded only by the Bay of Fundy ; and during the highest tides, the rising water is funnelled up the estuary into a wave that travels rapidly upstream against the river current. The largest bores occur in spring, but smaller ones can be seen throughout the year. The Environment Agency publishes timetable and prediction of bore heights on its website.^[4]. Being the onset of the flood tide it is accompanied by a rapid rise in water level which continues for about one and a half hours after the bore has passed. The Severn Bore is not a self-reinforcing solitary wave or soliton, but rather a shock wave which is formed because the wave is travelling faster than the wave speed in water above the bore (see tidal bore for more details).

The largest recorded bore was on 15 October 1966, when it reached a height of 9.2 feet (2.8 m).^[5]

[edit] Viewpoints

The bore is best seen at Stonebench, near Elmore, on the east bank, or at Minsterworth on the west bank. It can also be seen at Over Bridge. As a natural spectacle, in some respects, the Bore is best viewed (and heard) at night when there is less chance of powerboats etc on it, and/or just in front of it. The engine noise masks the sound of the wave and their wake(s) diminish the spectacle of a single wave rapidly advancing up a smooth river. To a certain extent it can still be seen in the dark and many spectators have powerful torches anyway.

[edit] Surfing

River surfing enthusiasts attempt to surf along on the wave, which can be 2 metres (7 ft). In March 2006, an unofficial record surf was achieved, for the longest-ever 'surf', by Steve King, a railway engineer from Gloucestershire, England. Despite the media acceptance of the record the exact distance of the ride was never verified and the record was later rejected by both the British Surfing Association and Guinness World Records.^[6] The Gloucester Harbour Trustees, as competent harbour authority for this part of the river, explicitly advise against this pastime.

In September 2005, several hundred surfers gathered in Newnham on Severn to celebrate 50 years since the first recorded attempt at surfing the Severn Bore^[1] and to view the première of Longwave by Donny Wright,^[7] a historical film documenting the evolution of the sport since its inception in 1955.

[edit] References

[edit] External links

• The Severn Bore Page
• "Severn Bore" (pdf). Gloucester Harbour Trustees. http://www.gloucesterharbourtrustees.org.uk/boresurfing.pdf. 
• "Severn Bore and Trent Aegir". Environment Agency. http://www.environment-agency.gov.uk/homeandleisure/recreation/31439.aspx. 
• "The Severn Bore". Stroud District Council. http://www.stroud.gov.uk/docs/community/severn_bore.asp.