The
Severn Estuary is the
estuaryAn estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries are thus subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of...
of the
River SevernThe River Severn is the longest river in Great Britain, at . It rises at an altitude of on Plynlimon near Llanidloes, Powys, in the Cambrian Mountains of mid Wales. It then flows through Shropshire, Worcestershire and Gloucestershire, with the county towns of Shrewsbury, Worcester, and Gloucester...
, the longest
riverA river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water...
in
Great BritainGreat Britain is an island lying to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island. With a population of about 59.6 million people, it is the third most populated island on Earth. Great Britain is surrounded by over 1000 smaller...
. Its high
tidal rangeThe tidal range is the vertical difference between the highest high tide and the lowest low tide. In other words, it is the difference in height between high and low tides. The most extreme tidal range will occur around the time of the full or new moons, when gravity of both the Sun and Moon are...
means it has been at the centre of discussions in the UK regarding renewable energy.
Geography
Definitions of the limits of the Severn Estuary vary. A narrower definition adopted by some maps is that the river becomes the Severn Estuary after the
Second Severn CrossingThe Second Severn Crossing is a bridge which carries the M4 motorway over the River Severn between England and Wales, inaugurated on 5 June 1996 by Charles, Prince of Wales to augment the traffic capacity of the original Severn Bridge built in 1966...
near
Severn BeachSevern Beach is a village on the mouth of the river Severn in South Gloucestershire, England. A riverside footpath leads beneath the Second Severn Crossing bridge which is part of the Severn Way...
,
South GloucestershireSouth Gloucestershire is a unitary district in the ceremonial county of Gloucestershire in South West England.-History:The district was created in 1996, when the county of Avon was abolished, by the merger of former area of the districts of Kingswood and Northavon...
and stretches to a line from Lavernock Point (south of
CardiffCardiff is the capital, largest city and most populous county of Wales. The city is Wales' chief commercial centre, the base for many national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for Wales. According to recent estimates, the...
) to
Sand PointSand Point in Somerset is the peninsula stretching out from Middle Hope, which lies to the north of the village of Kewstoke, and the stretch of coastline called Sand Bay. It is owned by the National Trust and is a popular place for walking...
near
Weston-super-MareWeston-super-Mare is a seaside resort town and civil parish in North Somerset, part of the ceremonial county of Somerset, England. It is located on the Bristol Channel coast, south west of Bristol, spanning the coast between the bounding high ground of Worlebury Hill and Bleadon Hill. It includes...
. A wider definition is that the estuary extends upstream to
AustAust is a small village in South Gloucestershire, England. It is near the eastern end of the Severn Bridge, which was built in 1966 to carry the M4 motorway over the route of the old Aust Ferry. It lies at ....
, the site of the
Severn BridgeThe Severn Bridge is a suspension bridge spanning the River Severn between South Gloucestershire, just north of Bristol, England, and Monmouthshire in South Wales, via Beachley, a peninsula between the River Severn and River Wye estuary. It is the original Severn road crossing between England and...
. The estuary is about wide at Aust, and about wide between Cardiff and Weston-super-Mare.
The estuary forms the boundary between Wales and
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
in this stretch. On the northern side of the estuary are the
Caldicot and Wentloog LevelsThe Caldicot and Wentloog Levels comprise two areas of low-lying estuarine alluvial wetland and intertidal mudflats adjoining the north bank of the Severn estuary, either side of the River Usk estuary near Newport in south east Wales...
, on either side of the city of
NewportNewport is a city and unitary authority area in Wales. Standing on the banks of the River Usk, it is located about east of Cardiff, and is the largest urban area within the historic county boundaries of Monmouthshire and the preserved county of Gwent...
; and, to the west, the city of Cardiff together with the resort of
PenarthPenarth is a town and seaside resort in the Vale of Glamorgan , Wales 5.2 miles south west from the Welsh capital city of Cardiff and lying on the north shore of the Severn Estuary at the southern end of Cardiff Bay...
. On the southern, English, side, are
AvonmouthAvonmouth is a port and suburb on the Severn Estuary, at the mouth of the River Avon. The place is within the city of Bristol, England.The port also gives its name to a Bristol council ward, which also includes Shirehampton and the western end of Lawrence Weston.- Suburb of Avonmouth :Avonmouth is...
,
PortisheadPortishead is a coastal town in North Somerset, England, with a population of 21,000 an increase of nearly 4,000 since 2001.Portishead’s history dates back to Roman times...
,
ClevedonClevedon is a town in North Somerset, England.The name derives from the Saxon, 'Cleve' meaning Cleave or Cleft and 'don' meaning hill, the town being situated amongst a group of small hills alongside the River Severn estuary...
, and Weston-super-Mare.
Denny IslandDenny Island is a small rocky island of , with scrub vegetation, in the mouth of the River Severn. Its rocky southern foreshore marks the boundary between England and Wales. Above high water mark, the island is reckoned administratively to Monmouthshire, South Wales...
is a small rocky island of , with scrub vegetation, approximately three miles north of Portishead. Its rocky southern foreshore marks the boundary between
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
and
WalesWales is a country that is part of the United Kingdom, bordered by England to its east, and the Atlantic Ocean and Irish Sea to its west. It is also an elective region of the European Union...
, but the island itself is reckoned administratively to
MonmouthshireMonmouthshire is a county in south east Wales. The name derives from the historic county of Monmouthshire which covered a larger area.-Historic county:...
, Wales.
The estuary has one of the highest tidal ranges in the world — about .
The estuary's funnel shape, its tidal range, and the underlying geology of rock, gravel and sand, produce strong tidal streams and high
turbidityTurbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
, giving the water a notably brown coloration.
West of the line between Lavernock Point and Sand Point is the
Bristol ChannelThe Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England, and extending from the lower estuary of the River Severn to the North Atlantic Ocean...
, which in turn discharges into the
Celtic SeaThe Celtic Sea is the area of the Atlantic Ocean off the south coast of Ireland. It is bounded to the east by Saint George's Channel, the Bristol Channel and the English Channel, as well as adjacent portions of Wales, Cornwall, Devon, and Brittany...
and the wider
Atlantic OceanThe Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about 106.4 million square kilometres , it covers approximately one-fifth of the Earth's surface and about one-quarter of its water surface area. The first part of its name refers to the Atlas of Greek...
. The islands of
Steep HolmSteep Holm is an English island lying in the Bristol Channel. The island covers 48.87 acre at high tide, expanding to 63.26 acres at mean low water. At its highest point it is 78 metres above mean sea level. It lies within the historic boundaries of Somerset and administratively, it...
and
Flat HolmFlat Holm is a limestone island lying in the Bristol Channel approximately from Lavernock Point in the Vale of Glamorgan, but in the City and County of Cardiff. It includes the most southerly point of Wales....
are located close to that line, in the middle of the estuary.
Sometimes the term Severn Estuary is used to include the tidal upstream stretch between Gloucester and Aust. During the highest tides on the upper reaches of this stretch, the rising water is funnelled up the estuary into the
Severn boreThe Severn bore is a tidal bore seen on the tidal reaches of the River Severn in England. It forms somewhat upstream of Sharpness, and can be seen as far upstream as Maisemore.- Formation :...
, a self-reinforcing solitary wave that travels rapidly upstream against the river current..
Conservation
The tidal range 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.
Parts of the estuary have also been designated a
Site of Special Scientific InterestA Site of Special Scientific Interest or SSSI is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based...
. The SSSI includes most of the foreshore upstream from Cardiff and
Brean DownBrean Down is a promontory off the coast of Somerset standing high and extending into the Bristol Channel at the eastern end of Bridgwater Bay between Weston-super-Mare and Burnham on Sea....
and most of the upper estuary as far as
SharpnessSharpness is an English port in Gloucestershire, one of the most inland in Britain, and eighth largest in the South West. It is on the River Severn at , at a point where the tidal range, though less than at Avonmouth downstream , is still large .The village of Sharpness is pronounced with the...
. The Upper Severn Estuary SSSI covers the tidal river between
PurtonPurton is a village on the east bank of the River Severn, 3 miles north of Berkeley, in Gloucestershire, England. The village is in the civil parish of Hinton. It lies opposite the hamlet of Purton on the west bank of the river....
and Frampton on Severn.
Tidal power
thumb
A huge tidal range and high level of surrounding industry and population have long made the Severn Estuary and
Bristol ChannelThe Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England, and extending from the lower estuary of the River Severn to the North Atlantic Ocean...
a focus for
tidal energyTidal power, sometimes called tidal energy, is a form of hydropower that converts the energy of tides into electricity or other useful forms of power....
schemes and ideas. Plans for a
Severn BarrageThe Severn Barrage is any of a number of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. Ideas for damming or barraging the Severn estuary have existed since the 19th century...
— running 16 km (10 miles) across the Bristol Channel from Lavernock Point near to and south west of
CardiffCardiff is the capital, largest city and most populous county of Wales. The city is Wales' chief commercial centre, the base for many national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for Wales. According to recent estimates, the...
to
Brean DownBrean Down is a promontory off the coast of Somerset standing high and extending into the Bristol Channel at the eastern end of Bridgwater Bay between Weston-super-Mare and Burnham on Sea....
near and just south west of
Weston-super-MareWeston-super-Mare is a seaside resort town and civil parish in North Somerset, part of the ceremonial county of Somerset, England. It is located on the Bristol Channel coast, south west of Bristol, spanning the coast between the bounding high ground of Worlebury Hill and Bleadon Hill. It includes...
in
SomersetSomerset is a county in South West England. The county town is Taunton, which is in the south of the county. The ceremonial county of Somerset borders the counties of Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west...
— 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 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 uphillPumped storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps. During...
, 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 WarmingGlobal warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C during the last century...
had started to be taken seriously. In April 2006 the Welsh Assembly approved the idea of utilising the tidal power, but the
RSPBThe Royal Society for the Protection of Birds is a British charitable organisation which works to promote conservation and protection of birds and the wider environment through public awareness campaigns, petitions and through the operation of nature reserves throughout the United Kingdom...
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 HuttonJohn Matthew Patrick Hutton is a British Labour politician, who has been the Member of Parliament for Barrow and Furness in Cumbria since 1992, and has served in a number of Cabinet offices, including Defence Secretary and Business Secretary....
, Secretary of State for Business, Enterprise and Regulatory Reform, announced a further feasibility study on 25 September 2007. The
Severn Tidal Power Feasibility StudySevern Tidal Power Feasibility Study is the name of a UK Government feasibility study into a tidal power project looking at the possibility of using the huge tidal range in the Severn Estuary and Bristol Channel to generate electricity....
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 as well as European Union renewable energy targets.The proposal for a
hydro-electricHydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
barrier to generate 8.6 GW and meet five percent of Britain's power needs, is being opposed by environmental groups.
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.
In 2001 SEP published the
Strategy for the Severn Estuary, which sets out a plan for the management of the estuary.
SEP uses a geographically extended definition of the Severn Estuary, beginning at the tidal limit of the River Severn in
GloucesterGloucester is a city, district and county town of Gloucestershire in the South West region of England. Gloucester lies close to the Welsh border, and on the River Severn, approximately north-east of Bristol, and south-southwest of Birmingham....
and ending at a line drawn between Hurlestone Point near
MineheadMinehead is a coastal town and civil parish in the north-west of the the English county of Somerset. It lies north-west of Taunton, very close to the county of Devon and the area of Exmoor National Park. Minehead has a population of approximately 10,000 making it the largest town in the West...
and
Nash PointNash Point is a headland and beach in the Vale of Glamorgan in south Wales. It is a popular location for ramblers and hiking along the cliffs....
in the
Vale of GlamorganThe Vale of Glamorgan is a county borough in Wales; an exceptionally rich agricultural area, it lies in in the southern part of Glamorgan, south Wales...
.
Archaeology
The archaeology of the Severn Estuary is richly varied and of considerable importance, reflecting both the varied nature of the topography and the importance of the river for both fishing and as a maritime waterway. The archaeological resource within the estuary is under threat from natural processes such as coastal erosion, exacerbated by the high tidal range and strong tidal currents, and from threats such as ongoing development pressure along the shoreline, marine aggregates extraction and new coastal defensive and realignment measures as well as proposed major infrastructure projects. An archaeological aerial survey report of the aerchaeology on the English side is available to view and download from the the reference link.