The attraction of the Severn Bore is the huge tidal range that it brings. Although it is very large—ranking as the second highest in the world—it still fails to take the number one spot, which is the Chientangkian, located in China. Britain’s Severn Bore has a tidal range that can be as much as 50 feet.
The phenomenon is mostly due to circumstantial locations of rivers and tides. Bores stem from the layout of the river and landscape and allow the tide to form a massive wave that flows down the river and enters the estuary, creating a rapid rise in water. There are over 60 known bores throughout the world.
The Severn River is extremely large in some areas, while narrow in others. The river flows past Avonmouth—where it is five miles wide—as well as through Aust, Chepstow, Lyndey and Sharpness, where it narrows to one mile wide. The river then further shrinks to only several hundred yards wide, reaching all the way to the city of Gloucester. The river forms a funnel shape as it flows towards the estuary, helping to contribute to the surge wave.
The Severn Bore provides several shows throughout the year. The occurrence of bores happens close to 260 times per year. Normally, it occurs at a rate of two per day for around 130 days of the year. Large bores that sometimes have swells of up to 50 feet only occur on around 25 days throughout the year.
Bores can pick up incredible speeds as they are flowing down the river and into the estuary. The Severn Bore can reach speeds of around 8 to 13 kilometers per hour within the sandy estuary section of the river, while topping out at speeds of 16 to 21 kilometers per hour where the river narrows close to Gloucester.
