Severn Bridge

Mathematical Gazetteer of the British Isles

The Severn Bridge is usually thought to join England and Wales, but the main part crosses the Severn from South Gloucestershire to Gloucestershire, then the smaller second part crosses the Wye into Monmouthshire, Wales. Opened on 8 September 1966, it was designed as an airfoil to reduce wind resistance and weight. It was the first box-girder suspension bridge in the world - this technique leads to a significantly thinner and lighter deck and has been widely used since, particularly on the Humber Bridge, which was the longest suspension bridge in the world, 1410m, for some time. The new second Severn bridge uses the older truss structure and looks much less interesting.

The River Severn is at the head of the triangular Bristol Channel and narrows rapidly as you go up the river. When the tide comes in, it is greatly compressed and produces the Severn Bore, a tidal wave up to 6ft (2m) high which rushes about 20 miles (32km) up the river to Gloucester at a speed of up to 10 mph (16 km/hr). It is best at the spring tides, i.e. at full and new moons, and is now popular with surfers and canoeists.

The Mathematical Gazetteer of the British Isles was created by David Singmaster.
The original site is at THIS LINK.