The Severn is the largest river in western Britain. Its source is the Plynlimon mountain of Mid-Wales, where it is also called Afon Hafren.
It is 300 km long, flowing first north to Shrewsbury, then south to the Severn Estuary near Bristol. It drains an area of 11,000 square kilometres. However, it has never been important for navigation as much as the Thames.
In the past flooding was a regular problem, but dams on the upper Severn now control the river.
