The Sevrn bore is a huge wave which sweeps upstream when tides are high.
The tidal range of up to 15m (50ft) in the Severn estuary is the second largest in the world. The waters
of the rising tide are forced rapidly from a wide estuary into the narrow
river channel below Gloucester. This funneling effect causes a spectacular
metre-high wave, known as the 'Severn bore', to travel upstream at
speeds of up to 32 km/hour (20 miles/hour).
The Severn bore can reach heights of 10ft in midstream and up to 820ft wide in sandy estuary channels.
At its fastest the bore can move at 13mph.
The bore travels 21 miles from Awre to Maisemore Weir.
There are about 260 bores on the Severn each year, usually two a day on about 130 days a year, around the vernal and autumnal equinoxes (February to April and August to October).
A timetable can be found at www.severn-bore.co.uk.
Many people watch the bore at Overton near Fretherne and Maisemore near Gloucester.
Favourite places for the locals are Stonebench on the east side of the river and Minsterworth on the west bank