Severn Estuary

The Severn estuary at Beachley, Gloucestershire, showing the strong tidal currents.

The Severn Estuary (Welsh: Môr Hafren) is the estuary of the River Severn, the longest river in Great Britain. Its high tidal range means it has been at the centre of discussions in the UK regarding renewable energy.

Geography

In navigational and cartographical terms, the river becomes the Severn Estuary after the Second Severn Crossing near Severn Beach, South Gloucestershire and stretches to a line from Lavernock Point (south of Cardiff) to Sand Point near Weston-super-Mare. The estuary is about 2 miles (3.2 km) wide at Aust, and about 9 miles (14 km) wide between Cardiff and Weston-super-Mare.

The estuary forms the boundary between Wales and England in this stretch. On the northern side of the estuary are the Caldicot and Wentloog Levels, on either side of the city of Newport; and, to the west, the city of Cardiff together with the resort of Penarth. On the southern, English, side, are Avonmouth, Portishead, Clevedon, and Weston-super-Mare. Denny Island is a small rocky island of 0.24 hectares (0.6 acres), with scrub vegetation, approximately three miles north of Portishead. Its rocky southern foreshore marks the boundary between England and Wales, but the island itself is reckoned administratively to Monmouthshire, Wales.

The estuary has one of the highest tidal ranges in the world — about 15 metres (49 ft).^[1][2] During the highest tides, the rising water is funnelled up the estuary into the Severn bore, a self-reinforcing solitary wave that travels rapidly upstream against the river current.^[3]. The estuary's funnel shape, its tidal range, and the underlying geology of rock, gravel and sand, produce strong tidal streams and high turbidity, giving the water a notably brown coloration.

The tidal range also results in the estuary having one of the most extensive intertidal wildlife habitats in the UK, comprising mudflats, sandflats, rocky platforms and islands. These form a basis for plant and animal communities typical of extreme physical conditions of liquid mud and tide-swept sand and rock. The estuary is recognised as a wetland area of international importance and is designated as a Ramsar site.^[4]

West of the line between Lavernock Point and Sand Point is the Bristol Channel, which in turn discharges into the Celtic Sea and the wider Atlantic Ocean. The islands of Steep Holm and Flat Holm are located close to that line, in the middle of the estuary.

Sometimes the term Severn Estuary is used to refer to a geographically wider area stretching from Gloucester to west Wales and Devon, although the upstream stretch between Gloucester and Aust is more correctly called the River Severn, and the maritime stretch between Wales and the coast of Somerset and Devon is more correctly called the Bristol Channel.

Renewable energy

The Severn Estuary has the potential to generate more renewable electricity than all other UK estuaries. If harnessed, it could create up to 5% of the UK’s electricity, contributing significantly to UK climate change goals as well as European Union renewable energy targets.^[5] The Severn Tidal Power Feasibility Study was launched in 2008 by the UK Government to assess all tidal range technologies (including barrages, lagoons and others). The study will look at the costs, benefits and impacts of a Severn tidal power scheme and will help Government decide whether it could or could not support such a scheme.

Severn Estuary Partnership

The Severn Estuary Partnership (SEP) was set up in 1995 as an independent initiative to focus the activities of local government, statutory authorities and interested parties such as farmers and fisherman. Its stated aim is To bring together all those involved in the development, management and use of the Estuary within a framework which encourages the integration of their interests and responsibilities to achieve common objectives.^[6] In 2001 SEP published the Strategy for the Severn Estuary, which sets out a plan for the management of the estuary.^[6]

SEP uses a geographically extended definition of the Severn Estuary, beginning at the tidal limit of the River Severn in Gloucester and ending at a line drawn between Hurlestone Point near Minehead and Nash Point in the Vale of Glamorgan.

See also

• Severnside
• Severn Barrage
• Severn Tidal Power Feasibility Study

References

External links

• The Severn Estuary Partnership

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