 The Severn is the longest river in the United Kingdom, at about  and, with an average discharge of at Apperley, Gloucestershire, it is the greatest river in terms of water flow in England and Wales.At the site of the Purton Hulks there is less than of land between the river and the Gloucester and Sharpness Canal (or Gloucester and Berkeley Canal).The canal was dug between Gloucester and Sharpness; for much of its length it runs close to the tidal River Severn, but cuts off a significant loop in the river, at a once-dangerous bend near Arlingham.