page_title: River Severn
section_title: Severn bore
hierarchical_section_title: River Severn / Severn bore
caption_attribution_description: English: Severn Bore hitting a bank
context_page_description: The River Severn, at 220 miles long, is the longest river in Great Britain. It is also the river with the most voluminous flow of water by far in all of England and Wales, discharging an average of 107 m³/s into the Bristol Channel at Apperley, Gloucestershire. It rises in the Cambrian Mountains in mid Wales, at an altitude of 2,001 feet, on the Plynlimon massif, which lies close to the Ceredigion/Powys border near Llanidloes. The river then flows through Shropshire, Worcestershire and Gloucestershire. The three county towns of Shrewsbury, Worcester and Gloucester lie on its course.
  The Severn's major tributaries are the Vyrnwy, the Tern, the Teme, the Warwickshire Avon, and the Worcestershire Stour.
  By convention, the River Severn is usually considered to end, and the Severn Estuary to begin, after the Second Severn Crossing, between Severn Beach in South Gloucestershire and Sudbrook, Monmouthshire. The total area of the Estuary’s drainage basin is 4,409 square miles. That figure excludes the area of the River Wye and the Bristol Avon, both of which flow into the Severn Estuary.
context_section_description: A phenomenon associated with the lower reaches of the Severn is the tidal bore, which forms upstream of the port of Sharpness.
  It is frequently asserted that the river's estuary, which empties into the Bristol Channel, has the second largest tidal range in the world—48 feet (15 m), exceeded only by the Bay of Fundy. However a tidal range greater than that of the Severn is recorded from the lesser known Ungava Bay in Canada. During the highest tides, the rising water is funnelled up the Severn estuary into a wave that travels rapidly upstream against the river current. The largest bores occur in spring, but smaller ones can be seen throughout the year. The bore is accompanied by a rapid rise in water level which continues for about one and a half hours after the bore has passed.
caption: Bore hitting the riverbank in 1994
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