INUMBER OF BORES PER ANNUM
Approximately 260, i.e., 2 per day on about 130 days. Large bores on about 25 days, morning and evening.
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.
HEIGHT OF BORE
Can be 3 metres in mid-stream, but 1 metre is good. 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.
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
Maximum bores occur one to three days after new and full moons; smaller ones on days immediately preceding and following maxima.
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.
The largest recorded bore was on 15 Oct 1966 downstream of Stonebench and attained a height of 9¼ ft (2.8 m).