Северн атырабы және ғылыми маңызы бар аймақ

Estuary and Site of Special Scientific Interest in Great Britain

The Severn Estuary (Aber Hafren) is the estuary of the River Severn, flowing into the Bristol Channel between South West England (from North Somerset, Bristol and South Gloucestershire) and South Wales (from Cardiff, Newport to Monmouthshire). Its very high tidal range, approximately 50 feet (15 m), creates valuable intertidal habitats and has led to the area being at the centre of discussions in the UK regarding renewable tidal energy.

Definitions of the limits of the Severn Estuary vary. In pre modern times the area was commonly referred to as the River Severn, or the Severn Sea. Today, at the upstream boundary, the tidal limit of the river is at Gloucester Docks. Downstream, the International Hydrographic Organization places the boundary between the estuary and the open sea of the Bristol Channel at a line between Sand Point, North Somerset (north of Weston super Mare) and Lavernock Point (south of Penarth in south Wales). This definition is used by the Severn Estuary Partnership and Visit England. A narrower definition adopted for navigation purposes by some charts includes only the area downstream of the Second Severn Crossing near Severn Beach, South Gloucestershire. The definition used on Admiralty Chart SC1179 and the Bristol Channel and Severn Cruising Guide is that the estuary extends upstream to Aust, the site of the Severn Bridge. On the north west (Welsh) side, the rivers Wye and Usk flow into the estuary, and on the south east (English) side, the River Avon joins at Avonmouth. West of the Wye, the estuary forms the boundary between Wales and England. On the northern side of the estuary are the Caldicot and Wentloog Levels which are 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 , 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 is about 2 mile (3 km) wide at Aust, and about 9 mile (14 km) wide between Cardiff and Weston super Mare. It has one of the highest tidal ranges in the world — about 50 feet (15 m). This funnel shape, large 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. During the highest tides, rising water is funnelled up the estuary into the Severn bore, a self reinforcing solitary wave that travels rapidly upstream against the river current. 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. The Ordnance Survey refers on its published mapping to a section of the estuary seaward of the two estuarine motorway crossings as the Mouth of the Severn.

A huge tidal range and high level of surrounding industry and population have long made the Severn Estuary and Bristol Channel a focus for tidal energy schemes and ideas. Plans for a Severn Barrage — running across the Bristol Channel from Lavernock Point near to and south west of Cardiff to Brean Down near and just south west of Weston super Mare in Somerset — would generate a massive 8640 MW when the tide flows, and have been discussed for several decades now. The power generated would come from a lake of 185 square miles (479 km2) with a potential energy depth of Tidal power only runs for around ten hours a day, but by using the enclosed lake as a reservoir of potential energy more hours of operation could be achieved. Other energy sources, such as wind and solar power, also create electricity at times that do not always match when it is needed. Excess power could be stored by pumping water uphill, as is already done at a variety of other installations in the UK. The UK Government shelved the plans in the late 1980s due largely to cost issues and local environmental concerns. However, this was before recent huge rises in the price of energy, and before global warming had started to be taken seriously. In April 2006 the Welsh Assembly approved the idea of utilising the tidal power, but the RSPB has raised serious concerns about the effect on the mud flats, that have European Environmental protection status, and the UK government Energy Review published later in the year did not endorse the scheme. Opinion is still divided on the benefits of a proposed barrage. John Hutton, Secretary of State for Business, Enterprise and Regulatory Reform, announced a further feasibility study on 25 September 2007. The Severn Tidal Power Feasibility Study was launched in January 2008 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. 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. The proposal for a hydro electric barrier to generate 8.6 GW and meet five percent of Britain's power needs, is being opposed by some environmental groups.

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. In 2001 SEP published the Strategy for the Severn Estuary, which sets out a plan for the management of the estuary. An archaeological aerial survey report of the archaeology on the English side is available to view and download from the reference link.