general information

True Oddity of the world tjhat is the Surfing Atlas. The Severn Bore is a phenomena caused by the extreme tidal range experienced on the coast of 8 to 9.5 metres. The peak of the incoming tide (twice per day) is sufficient to force a rideable wave through the river system. Typically the wave peaks as a rideable crest in certain locations along the bore, namely between Minsterworth and Gloucester.

The Severn Bore is a natural example of a self-reinforcing solitary wave or soliton. As the tidal energy enters an increasingly smaller river width from the estauary the river depth falls sharply which effectively funnels the energy into the 'bore'. The wave is at its best during periods of extreme tidal range which occur at both the Vernal Equinox: February-March-April and the Autumnal Equinox: August-September-October.  Within these periods, maximum bore height occurs three days after full or new moons.

The Bore works in a nine year cycle of moon transit. The highest tides following the cosmic ballet listed below: 

Bring something very buoyant for your adventure. 10 foot plus is a good place to start. The takeoff can be a mess, 20 guys paddling furiously on each take off point. Do your homework to work out where you are likely to pick up the wave. Whatever you do, dont blow the takeoff, its a long wait for the next wave.

SEVERN BORE FACTS:

BORES PER ANNUM

Approximately 260, i.e., 2 per day on about 130 days. Large bores on about 25 days, morning and evening.

TIDES

All tides of 8 metres or over on the Sharpness gauge have bores when river conditions are normal. Large bores occur with tides over 9.5 metres at Sharpness.

BORE HEIGHT

Can be 3 metres in mid-stream, but 1 metre is the norm. Height at banks much greater than in mid-stream and further accentuated on outer banks of bends.

WIDTH OF BORE

In sandy estuary width is unconfined and variable up to 250 metres. Minsterworth to Gloucester, bank to bank, 80 to 95 metres.

SPEED OF BORE

In sandy estuary 8 to 13 kilometres per hour according to location. Minsterworth to Gloucester 16 to 21 kilometres per hour.

SPEED OF WATER

Near Sharpness maximum flood and ebb 9.5 kilometres per hour. Minsterworth to Gloucester flood ebb 8 kilometres per hour; both considerably affected by freshwater flows.

BORE SEASONS

Bores occur all the year round with spring tides, but are biggest near an equinox.

Vernal Equinox: February-March-April
Autumnal Equinox: August-September-October

BORE DATES

Maximum bores occur one to three days after new and full moons; smaller ones on days immediately preceding and following maxima.

BORE TIMES

Between 7 a.m. and noon; 7 p.m. and mid night. Largest between 9 o'clock and 11 o'clock morning and evening (GMT). Individual times determined from tide tables.

LENGTH OF TRAVEL

Awre to Gloucester-33.8 kilometres.

TIME OF TRAVEL

2 hrs. 10 mins. to 2 hrs. 35 mins. according to conditions.

LARGEST EVER

The largest recorded bore was on 15 Oct 1966 downstream of Stonebench and attained a height of 9¼ ft (2.8 m).

Source: Wikipedia 

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otway1949
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