The Severn bore is a large surge wave which is seen in the estuary of the River Severn and is considered as one of Britain’s truly natural phenomena.
This is all due to the shape of the Severn estuary, which means that the water funnels into an ever decreasing narrow channel.
The estuary narrows from being 5 miles wide in Avonmouth to just 1 mile wide in nearby Lydney and by the time the estuary reaches the Gloucestershire village of Minsterworth on the north bank of the River Severn, it is less 100 yards wide!
The depth of the river changes quickly and when the incoming tide travels up the estuary, it is routed into an ever decreasing channel.
Consequently the surge wave or a “Severn Bore” as it is known, is created and large waves going upstream are caused.
There are about 60 bores that occur throughout the world and the Severn Bore is one of the largest in the world.
Around eight occur in the UK but bores are also knwon to happen on the Rivers Seine and Gironde in France and on the Amazon in Brazil.
The biggest bore in the world is on the Hang-chou-fe in China. When Spring tides occur the wave can reach up to heights of over 25 ft (7.5 metres) reaching speeds of between 13-15 knots, which lasting for up to 14 miles!
Image Credit: The Telegraph