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The
arrival of spring is the cue for interest to rise in that great
natural phenomena, the Severn Bore, a truly tidal wave which can
reach a height of three metres in mid-stream.
Bores
occur on about 260 days a year but most of these are very small.
Large bores form on about 25 days, morning and evening.
In 2004, based on tidal predictions, there are expected to be
NO five star bores. Nevertheless if weather conditions
are favourable the actual bore can be far higher than predicted.
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| Richard
Angwin |
Predictions
for 2004 have just been published and it appears that March, April
and September will be the best months for viewing the bore.
The
first big bore is predicted on Thursday March 20.
Predictions
are usually graded from 1 star up to five star. Bores in 2003 are
only expected to reach the level of four star. This does not necessarily
mean that we will not see a spectacular sight as there are more
factors involved than simply the height of the tide.
The
Severn Estuary
The
Severn Estuary has the second largest tidal range in the world (exceeded
only by Canada's Bay of Fundy). As tidal waters enter the Bristol
Channel they may have risen more than 15 metres by the time they
reach the Severn Estuary.
At
this point the Severn begins to narrow very rapidly. The reduced
carrying capacity causes the water to 'pile up' forming a wave which,
on the largest bores, can exceed three metres in height.
In
theory, any tide higher than around 9 metres at Sharpness will produce
a bore. But the biggest bores usually occur with tides of 10 metres
or more.
The best place to see the bore is at Minsterworth, four miles
from Gloucester on the A48. Over Bridge on the A40, one mile
out of Gloucester affords a good, but slightly restricted view.
Viewing at Stonebench is possible but this area does get very
congested. |
| Richard
Angwin |
In
2004, based on tidal predictions, there are expected to be NO
five star bores. Nevertheless if weather conditions are favourable
the actual bore can be far higher than predicted.
For
the weather to significantly enhance the bore requires some, or
all, of the following features. A strong southwesterly wind will
force the water up the Estuary at an even greater rate, as will
low pressure centred over region. The amount of freshwater in the
river is also significant.
A typical
bore will travels at speeds of between 16 and 21 kilometres per
hour between Minsterworth and Gloucester (that's close to 15 MPH).
Viewing
The
best place to see the bore is at Minsterworth, four miles from Gloucester
on the A48. Over Bridge on the A40, one mile out of Gloucester affords
a good, but slightly restricted view. Viewing at Stonebench is possible
but this area does get very congested.
Viewing
times at these locations are as follows: Minsterworth 9:19 AM; Stonebench
9:34 AM; Over Bridge 9:54 AM. Bear in mind that these times are
approximate and that it is advisable to take up your position a
good 20 minutes before the predicted time.
The
Severn Bore is not unique. There are bores on many other rivers,
both in the UK and throughout the world. But it is one of the biggest
and most spectacular and a sight not to be missed.
»Severn
Bore timetable 2004
by
Richard Angwin
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