Severn Barrage
Encyclopedia
The Severn Barrage refers to a range of ideas for building a barrage
from the English
coast
to the Welsh
coast over the Severn tidal estuary
. Ideas for dam
ming or barraging the Severn estuary
(and Bristol Channel
) have existed since the 19th century. The building of such a barrage would be a huge engineering feat, comparable with some of the world's biggest construction projects. The purposes of such a project has typically been one, or several of: transport links, flood
protection, harbour creation, or tidal power
generation. In recent decades it is the latter that has grown to be the primary focus for barrage ideas, and the others are now seen as useful side-effects. Following the Severn Tidal Power Feasibility Study
(2008-10), the British government concluded that there was no strategic case for building a barrage but to continue to investigate emerging technologies.
proposed a barrage from Beachley
to Aust
(now the site of the first Severn Bridge
), a span of just over 1 miles (1.6 km). Since this was before commercial electricity production, the first proposals were based on the desire for a large shipping harbour in the Severn Estuary, and also road and railway transport and flood protection.
No action was taken on Fulljames's proposals and three quarters of a century later, in 1925, an official study group was commissioned. An awareness of the large tidal range
of 14 metres (46 ft), second only to Bay of Fundy
in Eastern Canada
, led to a proposal to generate 800 Megawatt (MW) of electricity at English Stones
and although considered technically possible, it was prevented on economic grounds (then costing £25 million). The viability was tested a few years later in 1931 when Paul Shishkoff, a Russian
immigrant, demonstrated a 300 hp prototype tidal generator at Avonmouth
. It included a novel mechanism for spreading the power output over 24 hours. The full barrage was estimated at £5 million at the time.
In 1933 the Severn Barrage Committee Report (HMSO) from a committee chaired by Lord Brabazon
recommended that a 800 MW barrage across the English Stones area would be the best option. The work was interrupted by World War II
and then revived in 1945 when engineers predicted an output of 2.2 terawatt hours (TWh
) per year. A further government study looked at barrage options in 1948 and estimated the construction costs at £60 million. By the time of the next study in 1953 the estimated cost had risen to £200 million.
In 1971 a report by Dr Tom Shaw, a tidal Power expert and advocate proposed a barrage from Brean Down
to Lavernock Point. The scheme was estimated to cost £500 million. In 1975 the Central Electricity Generating Board (CEGB
), published a study with evidence from Bristol and Salford universities for the Secretary of State’s Advisory Council on Research and Development for Fuel and Power. As this was the era of cheap oil, the council established that a barrage could not be economically viable unless the energy situation deteriorated significantly.
and 1979 energy crisis
) the plans were reinvestigated by the Severn Barrage Committee in 1981. This committee was known as the "Bondi Committee" (after Professor Sir Hermann Bondi
). The committee investigated 6 possible barrage locations, from English Stones at the top of the estuary, down to a location largely at sea in the Bristol Channel between Lynmouth
in North Devon and Porthcawl
in South Wales. It produced a major energy paper, which recommended a 10 miles (16 km) long barrage of concrete powerhouse between Brean Down and Lavernock Point, sluice and plain caissons together with sand and rock-fill embankments. It would have generated 7,200 MW on the flow of the tides (the largest barrage considered could have produced double that power output). This set of plans was strongly built on a few years later by the Severn Tidal Power Group.
In 1984 Wimpey Atkins proposed a smaller barrage at English Stones, in the hope of creating a smaller more economically viable project that would avoid the environmental impact of a large barrage.
prepared a revised barrage proposed at English Stones to better tackle this issue.
Parsons Brinckerhoff further updated their earlier proposal in 2006 and current estimates for this barrage (now known as the "Shoots Barrage") would cost £1.4 to £1.8 billion to build, and generate 2.75 TWh of power per year. At the highest tidal range, it would develop a peak output of 1,050 MW, and 313 MW output on average throughout the year.
The barrage would be located just below the Second Severn Crossing
– i.e. above Cardiff
and Bristol
on the estuary – and so much smaller locks would be needed for upstream access to Sharpness
and Gloucester
docks as the large ports of Portbury
and Avonmouth
would be unaffected.
Like the STPG proposal, Hooker generates only on the ebb tide. Construction time would be four years. It would be built of rock fill embankment at the coastal sides (more like the proposals for "Tidal Lagoons"), but like the STPG would be sluice caissons and turbines with powerhouse in the middle section.
In April 2009 the Liberal Democrats
produced a report called "A Tidal Solution -
The Way Forward" that backed the Shoots Barrage along with a number of additional measures for power generation in the Severn Estuary. In September 2009 the report was adopted by the Lib Dem party conference as official party policy.
The barrage would use existing technology as used in the Rance tidal barrage
in France, the Annapolis Royal Generating Station
in Canada and the Netherlands sea barrages. Power would be most efficiently generated only in the flow direction, and this effect on tidal range would mean that the tidal extent would be halved by losing the low tide rather than the high tide. That is, that the tide would only go out as far as the current tidal mid-point, but high tides would be unaffected (unless the barrage was deliberately closed to prevent flooding).
The barrage would contain 216 turbines each generating 40 MW for the 8,640 MW total. Arrays of sluices would let the tide
in and then close to force it out through the turbines after the tide has gone out some distance outside the barrage. This deliberate building of a head on the water builds pressure that makes the turbines more efficient.
The barrage would contain a set of shipping locks, designed to handle the largest container vessels. Construction would take about eight years and would require 35,000 employees at peak build time. The minimum lifespan of the barrage would be 120 years (about three times that of a nuclear reactor), but could easily be 200 years if decent maintenance was performed.
The STPG appraisal concluded that the electricity
generated from the barrage would make the scheme economically viable if given certain "green
" advantages, and that the environmental
impact was acceptable. Margaret Thatcher
's government did not accept this, and shelved the plans. However, since then global warming
has radically altered the public perception of environmental damage
; and soaring oil
, gas
and energy costs have made the economics
of the barrage much more favourable.
The advent of renewable energy discounts favours electricity generated from "green" sources; and in addition, much lower interest rates make the cost of loans
much lower, and long-term financing of such massive projects is now more viable. Consequently, there have been renewed calls for these plans to be re-appraised.
) be significantly greater than for the Cardiff-Weston Barrage, and is in part a result of siting the structure at the "outer" Minehead to Aberthaw line, which roughly doubles the volume of tidal water available.
(SDC) published a report looking at the potential of tidal power
in the UK, including proposals for a Severn barrage. The report draws on a series of five evidence-based reports, one of which summarises all the available evidence from previous studies on a number of Severn barrage options, but focusing on the Cardiff-Weston and the Shoots schemes. The SDC also commissioned a programme of public and stakeholder engagement, which included a national opinion poll and a series of local and regional workshops.
The SDC gave its support to the building of a Severn barrage, providing a number of strict conditions were met. These include:
The SDC also raised the challenge of viewing the requirement for compensatory habitat as an "environmental opportunity", through the potential to combine a climate change mitigation project with the adaptation that will be required to respond to the effects of climate change. A publicly led project would enable the use of a low discount rate
(2%), which would result in a competitive cost of electricity, and would limit the economic impact of even a very large-scale compensatory habitats package. Electricity production costs are not competitive if a commercial discount rate is applied.
The study, previously led by John Hutton
, Secretary of State for Business, Enterprise and Regulatory Reform, was led until the 2010 General Election by Ed Miliband
, Secretary of State for Energy and Climate Change
.
The study aims to gather and assess evidence to enable the Government to decide whether it could support a tidal power scheme in the Severn Estuary and if so on what basis.
Key work areas involved are:
The feasibility study concluded its first phase when a public consultation was launched on 26 January 2009. The consultation covered a proposed short-list of potential tidal power project options from an initial list of 10 schemes, processes that were undertaken during shortlisting and the proposed scope of the Strategic Environmental Assessment (SEA). The SEA is a formal environmental assessment of plans or programmes which are likely to have significant effects on the environment. A consortium
led by Parsons Brinckerhoff
(PB) has been appointed to manage this part of the project. The process is guided by a stakeholder steering group. The study will culminate in a full public consultation in 2010.
In July 2009 the Government response to consultation confirmed detailed study would be carried out in the second phase on the five schemes that were proposed for short-listing in January. It also announced work to bring forward 3 further schemes that are in the very early stages of development. In September 2010, The Observer
reported that the government intended to rule out the possibility of public funding for a complete barrage, while recommending that further feasibility studies be carried out on smaller projects. On 18 October the government announced that the project was being abandoned.
s. A consequence of this plan is that the carbon payback time—the time it takes for saved carbon emissions (those produced by generating the same amount of power in other ways) to outstrip those produced during construction— could be as little as four-and-a-half months, although likely to be around six.
It could continue to operate for around 120 years, compared with 30–40 years for nuclear power plants. An additional benefit would be to improve energy security
.
However, although power supply is predictable, peaks in generation from the barrage do not necessarily coincide with peaks in demand. There are two major tidal cycles affecting power output:
Just under eight hours per day of generation time is expected.
and their banks. Schemes of the scale of Cardiff-Weston are likely to require significant Government
involvement. If the bank
s feel that a smaller project is viable and decide to lend the money at an acceptable cost of finance then the projects will go ahead (subject to planning and other approvals). None of this cost would directly fall on the tax
-payer but any support mechanism for the tidal power would be likely to fall on consumer
s. There would though be secondary knock-on costs from the tidal power project that might be met by the tax-payer, such as modifying existing port
s, provision of compensatory habitat and dealing with environmental change. However, these would be offset by the positive knock-on effects, such as flood
protection - which would have otherwise also cost tax-payer money. Whether the parties actually decided to exchange money for these knock-on effects would be a matter for Government negotiation.
protection would be provided by the barrage, covering the vulnerable Severn estuary from storm surges from the sea. New road and/or rail transport
links could be built across a barrage if demand rises in the future, as outlined below. Any barrage could provide a boost to the local economy
— construction industry in the short term, tourism and infrastructure in the long term.
However, shipping
would have to navigate locks, and existing estuary industries, including fisheries, would be damaged and jobs lost. All industrial discharges into the River Severn (e.g. from Avonmouth
) would have to be reassessed.
due to the European importance of its ecology. The inter-tidal area provides food for over 85,000 migratory and wintering water birds, and represents 7% of the UK's total estuaries. There are nature reserve
s and Site of Special Scientific Interest
(SSSI) on the islands of Flat Holm
and Steep Holm
.
The Barrage was not supported in the 2003 Energy Review due to "strong environmental concerns" (The same paper also described nuclear power as "an unattractive option").
The RSPB opposes any Severn Barrage because of the effect it will have the feeding grounds 85,000 birds depend on, stating "The impact a barrage would have is huge. This is one of the most important sites in the UK for wild birds and the chances of them surviving if it went ahead are fairly slim. There wouldn't be enough room left for all the birds and there wouldn't be enough food for those that remained. The estuary is one of the UK's most important sites for water birds and its wildlife value must be taken fully into account."
The present strong tidal currents in the estuary serve to lift up silt
sediment
and so keep the water thick with fine particles. This blocks light-penetration and means that the Severn Estuary marine
environment is actually a relative desert
, in terms of both plant and fish
life.
The barrage will not create a "lagoon
" - as both opponents and supporters have sometimes claimed. Tidal power stations by definition require that the tide flows through the barrage, but the tidal range in the Severn would be halved. There are claims that the migration of fish would be hampered, but these are contested. The Severn bore
would also be eliminated. Any barrage would be likely to stimulate coastal erosion
in some areas, and create a negative visual impact upon the landscape (subjective, similar to wind turbines). There would also be negative consequences of the huge amount of concrete (and other materials) needed, with the quarrying of stone likely to impact on other areas.
DEFRA claims that the environmental effects
of the barrage still need more analysis before final conclusions can be drawn. The Sustainable Development Commission
is investigating UK tidal resources, including tidal power in the Severn Estuary and its environmental impact, and should report mid-2007.
support the idea of tidal power, but oppose barrages because of the environmental impact. They have proposed their own plans based on the concept of tidal lagoons,
whereby man-made lagoons in the estuary would fill and drain through turbines. Their proposals would include lagoons covering up to 60% of the area covered by the barrage, which in some smaller configurations would not impound water in the ecologically sensitive inter-tidal areas of the estuary. The lagoons could be sub-divided so power would be generated at more states of the tide than a barrage, with lower peak output, giving economic advantages to set against the higher construction cost of longer barriers. This idea is based on a prototype now being designed at Swansea
bay. However leading figures in the construction industry are sceptical that the lagoons can be economic.
A set of Tidal lagoons known as the "Russell Lagoon concept" were studied and dismissed by the 1981 Bondi Committee report, rejected on the grounds of both economics and environmental damage. Studies suggested that tidal currents around and between the lagoons would become extremely fierce and damaging.
s. This has been put forward by the Severn Tidal Fence Consortium, a group led by IT Power and including a number of industry and academic groups.
This would attempt to maximise the potential power generated whilst allowing for shipping to reach Cardiff and Bristol without hindrance (through gaps at least 650m wide) and wildlife to maintain their existing habitats. The group has now been contracted by the UK government to investigate the idea under the Severn Embryonic Technology Scheme (SETS).
The group estimates that it would cost £3.5bn to construct an outer fence from Aberthaw
to Minehead
which would generate 1.3GW or 3.5TWh/year. It is also investigating an inner fence from Lavernock Point to Brean Down including Flat Holm
and Steep Holm
islands. Both fences could possibly be built.
The fence would permit the migration of salmon and would only slightly affect the mudflats used by migrating birds. In addition it could significantly reduce the flood risk in the Severn estuary.
A second approach to a tidal fence being explored by VerdErg uses a different way of generating electricity called the Spectral Machine Energy Converter (SMEC).
This uses the flow past Venturi tube sections as a pump without moving parts to create a large secondary flow which drives turbines on the sea bed.
Verderg estimate that they could produce output of 13.7TWh/yr at a cost of £9.9bn using the Lavernock Point/Brean Down connection.
Some simulations have also been done on the partial barriers envisaged by Dynamic tidal power
which have similar advantages.
it could have by way of its renewable power generation.
The largest barrages (sited beyond Hinkley Point
and towards Minehead
on the English side and Aberthaw
on the Welsh side) would significantly affect the entire Severn Estuary and much of the Bristol Channel, but could generate 15 GW peak power and protect the whole of the Somerset levels against flooding and sea-level rise caused by Global Warming. The smallest barrages (sited at Aust
/Chepstow
) would affect only the river and estuary in Gloucestershire, but would also only generate perhaps 0.75 GW peak power.
and Cardiff
. Various proposals include a dual carriageway
road giving a further crossing in addition to the Second Severn Crossing
and the Severn Bridge
. The road would have to be taken over the sea locks on a bridge at a height of the Bridge of the Americas
(i.e. with a clearance of 61.3m) if the locks are Panamax
-sized.
Some proposals also include a double track railway line across the barrage. A railway would have a longer approach up to a fixed bridge over the locks. The approach would be greatest for non-electrified heavy railway capable of taking freight, slightly less for non-electrified passenger line, and less still for electrified passenger line. There is no electrification presently in the Bristol or Cardiff areas, but this would change with the electrification of the Great Western Main Line
. An alternative to a fixed bridge would be a swing bridge
, though there is concern expressed at this reducing capacity through the locks and on the railway. However, two swing bridges, one at either end of the lock would mean that one bridge could be kept open to railway traffic at all times. The double track could be reduced to single track at this point without creating too much of a bottleneck, or if double track is required this could be worked around by grade separating the two lines and having double-decked bridges. The line could then be used to partially relieve the Severn Tunnel
.
The option for a new fixed rail link has implications for several wider transport proposals. One of the proposed routes for an Irish Sea Tunnel
is from Fishguard, which would generate large amounts of extra freight traffic which the current Severn tunnel - already operating at capacity - could not handle. Additionally, a new high speed rail route has been suggested between London, Bristol, and Cardiff, which faces similar capacity constraints.
Tidal barrage
A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces....
from the English
England
England 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, with the North Sea to the east and the English Channel to the south separating it from continental...
coast
Coast
A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...
to the Welsh
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
coast over the Severn tidal estuary
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
. Ideas for dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
ming or barraging the Severn estuary
Severn Estuary
The Severn Estuary 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:...
(and Bristol Channel
Bristol Channel
The Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Severn to the North Atlantic Ocean...
) have existed since the 19th century. The building of such a barrage would be a huge engineering feat, comparable with some of the world's biggest construction projects. The purposes of such a project has typically been one, or several of: transport links, flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
protection, harbour creation, or tidal power
Tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
generation. In recent decades it is the latter that has grown to be the primary focus for barrage ideas, and the others are now seen as useful side-effects. Following the Severn Tidal Power Feasibility Study
Severn Tidal Power Feasibility Study
Severn 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....
(2008-10), the British government concluded that there was no strategic case for building a barrage but to continue to investigate emerging technologies.
History
There have been numerous proposed projects over the years, initially to provide a safe harbour and more recently to generate electricity.Early projects
In 1849 Thomas Fulljames, a civil engineer and the county surveyor for GloucestershireGloucestershire
Gloucestershire is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn, and the entire Forest of Dean....
proposed a barrage from Beachley
Beachley
Beachley is a village in Gloucestershire, England, near the border with Wales. It is located on a peninsula at the junction between the Rivers Wye and Severn, where the Severn Bridge ends and the smaller secondary bridge for the River Wye begins. The tidal drop here is one of the highest in the UK...
to Aust
Aust
Aust is a small village in South Gloucestershire, England, the historical site of the eastern terminal of the Aust Ferry crossing route over the River Severn between England and Wales, believed to have been used in Roman times as a continuation of Icknield Street which led from Eastern England...
(now the site of the first Severn Bridge
Severn Bridge
The 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...
), a span of just over 1 miles (1.6 km). Since this was before commercial electricity production, the first proposals were based on the desire for a large shipping harbour in the Severn Estuary, and also road and railway transport and flood protection.
Tidal range
The tidal range is the vertical difference between the high tide and the succeeding low tide. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth...
of 14 metres (46 ft), second only to Bay of Fundy
Bay of Fundy
The Bay of Fundy is a bay on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine...
in Eastern Canada
Eastern Canada
Eastern Canada is generally considered to be the region of Canada east of Manitoba, consisting of the following provinces:* New Brunswick* Newfoundland and Labrador* Nova Scotia* Ontario* Prince Edward Island* Quebec...
, led to a proposal to generate 800 Megawatt (MW) of electricity at English Stones
English Stones
English Stones is a rocky outcrop in the Severn Estuary between Caldicot, Monmouthshire and Severn Beach. It is exposed at low tide, and because of this and the fact it is a rare spot of solid land in the highly tidal estuary, it has long been considered at a location to build barrages, dams or...
and although considered technically possible, it was prevented on economic grounds (then costing £25 million). The viability was tested a few years later in 1931 when Paul Shishkoff, a Russian
Russians
The Russian people are an East Slavic ethnic group native to Russia, speaking the Russian language and primarily living in Russia and neighboring countries....
immigrant, demonstrated a 300 hp prototype tidal generator at Avonmouth
Avonmouth
Avonmouth is a port and suburb of Bristol, England, located on the Severn Estuary, at the mouth of the River Avon.The council ward of Avonmouth also includes Shirehampton and the western end of Lawrence Weston.- Geography :...
. It included a novel mechanism for spreading the power output over 24 hours. The full barrage was estimated at £5 million at the time.
In 1933 the Severn Barrage Committee Report (HMSO) from a committee chaired by Lord Brabazon
Baron Brabazon of Tara
Baron Brabazon of Tara, of Sandwich in the County of Kent, is a title in the Peerage of the United Kingdom. It was created in 1942 for the aviation pioneer and Conservative politician John Moore-Brabazon. Moore-Brabazon was a descendant through a female line of Edward Brabazon, 7th Earl of Meath...
recommended that a 800 MW barrage across the English Stones area would be the best option. The work was interrupted by World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
and then revived in 1945 when engineers predicted an output of 2.2 terawatt hours (TWh
TWH
TWH or twh could refer to:*Tennessee Walking Horse, a breed of horse* Toronto Western Hospital, a hospital in Toronto, Canada* TWH Bus & Coach, a bus company in Romford, England* Terrawatt-hour, measure of electrical energy, 1012 watt-hours...
) per year. A further government study looked at barrage options in 1948 and estimated the construction costs at £60 million. By the time of the next study in 1953 the estimated cost had risen to £200 million.
In 1971 a report by Dr Tom Shaw, a tidal Power expert and advocate proposed a barrage from Brean Down
Brean Down
Brean 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....
to Lavernock Point. The scheme was estimated to cost £500 million. In 1975 the Central Electricity Generating Board (CEGB
CEGB
The Central Electricity Generating Board was the cornerstone of the British electricity industry for almost 40 years; from 1957, to privatisation in the 1990s....
), published a study with evidence from Bristol and Salford universities for the Secretary of State’s Advisory Council on Research and Development for Fuel and Power. As this was the era of cheap oil, the council established that a barrage could not be economically viable unless the energy situation deteriorated significantly.
Bondi Committee – 1981
After just such a deterioration (due to the Iranian RevolutionHistory of Iran
The history of Iran has been intertwined with the history of a larger historical region, comprising the area from the Danube River in the west to the Indus River and Jaxartes in the east and from the Caucasus, Caspian Sea, and Aral Sea in the north to the Persian Gulf and the Gulf of Oman and Egypt...
and 1979 energy crisis
1979 energy crisis
The 1979 oil crisis in the United States occurred in the wake of the Iranian Revolution. Amid massive protests, the Shah of Iran, Mohammad Reza Pahlavi, fled his country in early 1979 and the Ayatollah Khomeini soon became the new leader of Iran. Protests severely disrupted the Iranian oil...
) the plans were reinvestigated by the Severn Barrage Committee in 1981. This committee was known as the "Bondi Committee" (after Professor Sir Hermann Bondi
Hermann Bondi
Sir Hermann Bondi, KCB, FRS was an Anglo-Austrian mathematician and cosmologist. He is best known for developing the steady-state theory of the universe with Fred Hoyle and Thomas Gold as an alternative to the Big Bang theory, but his most lasting legacy will probably be his important...
). The committee investigated 6 possible barrage locations, from English Stones at the top of the estuary, down to a location largely at sea in the Bristol Channel between Lynmouth
Lynmouth
Lynmouth is a village in Devon, England, on the north edge of Exmoor.The village straddles the confluence of the West Lyn and East Lyn rivers, in a gorge below Lynton, to which it is connected by the Lynton and Lynmouth Cliff Railway....
in North Devon and Porthcawl
Porthcawl
Porthcawl is a town on the south coast of Wales in the county borough of Bridgend, 25 miles west of the capital city, Cardiff and 19 miles southeast of Swansea...
in South Wales. It produced a major energy paper, which recommended a 10 miles (16 km) long barrage of concrete powerhouse between Brean Down and Lavernock Point, sluice and plain caissons together with sand and rock-fill embankments. It would have generated 7,200 MW on the flow of the tides (the largest barrage considered could have produced double that power output). This set of plans was strongly built on a few years later by the Severn Tidal Power Group.
In 1984 Wimpey Atkins proposed a smaller barrage at English Stones, in the hope of creating a smaller more economically viable project that would avoid the environmental impact of a large barrage.
Hooker or Shoots Barrage – 1987
This Wimpey Atkins 1984 study was criticised because it did not tackle the issue of silting and in 1987 Arthur Hooker OBE (a former partner of WS Atkins) in conjunction with Parsons BrinckerhoffParsons Brinckerhoff
Parsons Brinckerhoff is a professional services firm with 14,000 employees in 150 offices providing construction and operation management, planning, design, engineering, program management, strategic consulting, environmental and sustainability services for clients and communities in the Americas,...
prepared a revised barrage proposed at English Stones to better tackle this issue.
Parsons Brinckerhoff further updated their earlier proposal in 2006 and current estimates for this barrage (now known as the "Shoots Barrage") would cost £1.4 to £1.8 billion to build, and generate 2.75 TWh of power per year. At the highest tidal range, it would develop a peak output of 1,050 MW, and 313 MW output on average throughout the year.
The barrage would be located just below the Second Severn Crossing
Second Severn Crossing
The 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 HRH The Prince of Wales to augment the traffic capacity of the original Severn Bridge built in 1966...
– i.e. above Cardiff
Cardiff
Cardiff is the capital, largest city and most populous county of Wales and the 10th largest city in the United Kingdom. The city is Wales' chief commercial centre, the base for most national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for...
and Bristol
Bristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
on the estuary – and so much smaller locks would be needed for upstream access to Sharpness
Sharpness
Sharpness 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...
and Gloucester
Gloucester
Gloucester 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....
docks as the large ports of Portbury
Portbury
Portbury is a village and civil parish in Somerset, England within the Unitary Authority of North Somerset.The parish includes the hamlet of Sheepway which is situated on the moorland at the northern edge of the Gordano valley, between the Gordano services on the M5 motorway and Portishead, near...
and Avonmouth
Avonmouth
Avonmouth is a port and suburb of Bristol, England, located on the Severn Estuary, at the mouth of the River Avon.The council ward of Avonmouth also includes Shirehampton and the western end of Lawrence Weston.- Geography :...
would be unaffected.
Like the STPG proposal, Hooker generates only on the ebb tide. Construction time would be four years. It would be built of rock fill embankment at the coastal sides (more like the proposals for "Tidal Lagoons"), but like the STPG would be sluice caissons and turbines with powerhouse in the middle section.
In April 2009 the Liberal Democrats
Liberal Democrats
The Liberal Democrats are a social liberal political party in the United Kingdom which supports constitutional and electoral reform, progressive taxation, wealth taxation, human rights laws, cultural liberalism, banking reform and civil liberties .The party was formed in 1988 by a merger of the...
produced a report called "A Tidal Solution -
The Way Forward" that backed the Shoots Barrage along with a number of additional measures for power generation in the Severn Estuary. In September 2009 the report was adopted by the Lib Dem party conference as official party policy.
Severn Tidal Power Group – 1989
The £4.2 million study by Severn Tidal Power Group (STPG) built on the work of the Severn Barrage Committee, but also examined other possible barrages, and produced another major energy paper. They concluded that the 1981 plans were the best location for a barrage, but calculated that the power output could be larger, at 8,640 MW during flow, or 2,000 MW average power. This would provide 17 TWh of power per year (about 6% of UK consumption), equivalent to about 18 million tons of coal or 3 nuclear reactors. The cost in 1989 was calculated to be about £8 billion (£12 billion in 2006 money – about the same as six nuclear reactors, but different lifespan), and running costs would be £70 million per year (about the same as 1.5 nuclear reactors).The barrage would use existing technology as used in the Rance tidal barrage
Rance tidal power plant
The Rance Tidal Power Station is the world's first tidal power station and also the world's second biggest tidal power station. The facility is located on the estuary of the Rance River, in Brittany, France. Opened on the 26th November 1966, it is currently operated by Électricité de France, and is...
in France, the Annapolis Royal Generating Station
Annapolis Royal Generating Station
The Annapolis Royal Generating Station is a 20 MW tidal power station located on the Annapolis River immediately upstream from the town of Annapolis Royal, Nova Scotia, Canada. It is the only tidal generating station in North America. The generating station harnesses the tidal difference...
in Canada and the Netherlands sea barrages. Power would be most efficiently generated only in the flow direction, and this effect on tidal range would mean that the tidal extent would be halved by losing the low tide rather than the high tide. That is, that the tide would only go out as far as the current tidal mid-point, but high tides would be unaffected (unless the barrage was deliberately closed to prevent flooding).
The barrage would contain 216 turbines each generating 40 MW for the 8,640 MW total. Arrays of sluices would let the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
in and then close to force it out through the turbines after the tide has gone out some distance outside the barrage. This deliberate building of a head on the water builds pressure that makes the turbines more efficient.
The barrage would contain a set of shipping locks, designed to handle the largest container vessels. Construction would take about eight years and would require 35,000 employees at peak build time. The minimum lifespan of the barrage would be 120 years (about three times that of a nuclear reactor), but could easily be 200 years if decent maintenance was performed.
The STPG appraisal concluded that the electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
generated from the barrage would make the scheme economically viable if given certain "green
Ecology movement
The global ecology movement is based upon environmental protection, and is one of several new social movements that emerged at the end of the 1960s. As a values-driven social movement, it should be distinguished from the pre-existing science of ecology....
" advantages, and that the environmental
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
impact was acceptable. Margaret Thatcher
Margaret Thatcher
Margaret Hilda Thatcher, Baroness Thatcher, was Prime Minister of the United Kingdom from 1979 to 1990...
's government did not accept this, and shelved the plans. However, since then global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
has radically altered the public perception of environmental damage
Environmentalism
Environmentalism is a broad philosophy, ideology and social movement regarding concerns for environmental conservation and improvement of the health of the environment, particularly as the measure for this health seeks to incorporate the concerns of non-human elements...
; and soaring oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
, gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
and energy costs have made the economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...
of the barrage much more favourable.
The advent of renewable energy discounts favours electricity generated from "green" sources; and in addition, much lower interest rates make the cost of loans
Debt
A debt is an obligation owed by one party to a second party, the creditor; usually this refers to assets granted by the creditor to the debtor, but the term can also be used metaphorically to cover moral obligations and other interactions not based on economic value.A debt is created when a...
much lower, and long-term financing of such massive projects is now more viable. Consequently, there have been renewed calls for these plans to be re-appraised.
Severn Tidal Reef – 2007
Evans Engineering (Joseph Evans & Sons Limited) have released plans for what they call a Severn Tidal "Reef". This is a novel structure which aims to overcome the environmental side-effects of a barrage, and can be conceptualised as being half-way between a barrage and a tidal "fence" (a linked string of tidal-stream turbines). The designer, Rupert Evans, had previously worked on a tidal fence proposal, but since dismissed it as unworkable. The reef reduces environmental impact by working with a much smaller "head" of water—just 2 metres (6.6 ft)—thereby reducing the impact of the structure on the estuary water and flow. The smaller head means that the water velocity is much lower and more lower power turbines are required. The load factor will be higher, partly because of the generation being both ebb and flow and the total energy output should (according to a recent report by W.S.Atkins commissioned by the RSPBRoyal Society for the Protection of Birds
Bird Notes and News was first published in April 1903.The title changed to 'Bird Notes' in 1947. In the 1950s, there were four copies per year . Each volume covered two years, spread over three calendar years...
) be significantly greater than for the Cardiff-Weston Barrage, and is in part a result of siting the structure at the "outer" Minehead to Aberthaw line, which roughly doubles the volume of tidal water available.
Sustainable Development Commission – 2007
On 1 October 2007, the UK's Sustainable Development CommissionSustainable Development Commission
The Sustainable Development Commission was a non-departmental public body responsible for advising the UK Government, Scottish Government, Welsh Assembly Government, and Northern Ireland Executive on sustainable development....
(SDC) published a report looking at the potential of tidal power
Tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
in the UK, including proposals for a Severn barrage. The report draws on a series of five evidence-based reports, one of which summarises all the available evidence from previous studies on a number of Severn barrage options, but focusing on the Cardiff-Weston and the Shoots schemes. The SDC also commissioned a programme of public and stakeholder engagement, which included a national opinion poll and a series of local and regional workshops.
The SDC gave its support to the building of a Severn barrage, providing a number of strict conditions were met. These include:
- A Severn barrage should be publicly led as a project and publicly owned as an asset to avoid short-term decisions and ensure the long-term public interest
- Full compliance with the EU Habitats and Birds DirectiveBirds DirectiveThe Birds Directive is a European Union directive adopted in 2009. It replaces Council Directive 79/409/EEC of 2 April 1979 on the conservation of wild birds which was modified several times and had become very unclear...
s is vital, as is a long-term commitment to creating compensatory habitats on an unprecedented scale - Development of a Severn barrage must not divert Government attention away from much wider action on climate change
The SDC also raised the challenge of viewing the requirement for compensatory habitat as an "environmental opportunity", through the potential to combine a climate change mitigation project with the adaptation that will be required to respond to the effects of climate change. A publicly led project would enable the use of a low discount rate
Discount rate
The discount rate can mean*an interest rate a central bank charges depository institutions that borrow reserves from it, for example for the use of the Federal Reserve's discount window....
(2%), which would result in a competitive cost of electricity, and would limit the economic impact of even a very large-scale compensatory habitats package. Electricity production costs are not competitive if a commercial discount rate is applied.
UK Government study announced – 2007
A two year feasibility study was announced in late 2007, and the terms of reference were announced on 22 January 2008, following the publication of the Turning the Tide report from the Sustainable Development Commission. This study builds upon past studies and focuses on a variety of tidal range technologies including barrages and lagoons, and innovative designs such as a tidal fence and a tidal reef in the Severn estuary.The study, previously led by John Hutton
John Hutton (Labour MP)
John Matthew Patrick Hutton, Baron Hutton of Furness is a British Labour Party politician who was the Member of Parliament for Barrow and Furness in Cumbria from 1992 to 2010, and has served in a number of Cabinet offices, including Defence Secretary and Business Secretary...
, Secretary of State for Business, Enterprise and Regulatory Reform, was led until the 2010 General Election by Ed Miliband
Ed Miliband
Edward Samuel Miliband is a British Labour Party politician, currently the Leader of the Labour Party and Leader of the Opposition...
, Secretary of State for Energy and Climate Change
Secretary of State for Energy and Climate Change
The Secretary of State for Energy and Climate Change is a British government cabinet position currently held by Chris Huhne. The government department was created on 3 October 2008 when former Prime Minister Gordon Brown reshuffled his cabinet....
.
The study aims to gather and assess evidence to enable the Government to decide whether it could support a tidal power scheme in the Severn Estuary and if so on what basis.
Key work areas involved are:
- The environmental impacts on biodiversity and wildlife; flood management; geomorphologyGeomorphologyGeomorphology is the scientific study of landforms and the processes that shape them...
; water quality; landscape and compensatory habitat; - Engineering and technical areas such as options appraisal; costs; energy yield, design and construction, links to the National Grid and supply chain;
- Economic considerations – financing; ownership and energy market impacts;
- The regional social, economic and business impacts;
- Planning and consents – regulatory compliance; and
- Stakeholder engagement and communication.
The feasibility study concluded its first phase when a public consultation was launched on 26 January 2009. The consultation covered a proposed short-list of potential tidal power project options from an initial list of 10 schemes, processes that were undertaken during shortlisting and the proposed scope of the Strategic Environmental Assessment (SEA). The SEA is a formal environmental assessment of plans or programmes which are likely to have significant effects on the environment. A consortium
Consortium
A consortium is an association of two or more individuals, companies, organizations or governments with the objective of participating in a common activity or pooling their resources for achieving a common goal....
led by Parsons Brinckerhoff
Parsons Brinckerhoff
Parsons Brinckerhoff is a professional services firm with 14,000 employees in 150 offices providing construction and operation management, planning, design, engineering, program management, strategic consulting, environmental and sustainability services for clients and communities in the Americas,...
(PB) has been appointed to manage this part of the project. The process is guided by a stakeholder steering group. The study will culminate in a full public consultation in 2010.
In July 2009 the Government response to consultation confirmed detailed study would be carried out in the second phase on the five schemes that were proposed for short-listing in January. It also announced work to bring forward 3 further schemes that are in the very early stages of development. In September 2010, The Observer
The Observer
The Observer is a British newspaper, published on Sundays. In the same place on the political spectrum as its daily sister paper The Guardian, which acquired it in 1993, it takes a liberal or social democratic line on most issues. It is the world's oldest Sunday newspaper.-Origins:The first issue,...
reported that the government intended to rule out the possibility of public funding for a complete barrage, while recommending that further feasibility studies be carried out on smaller projects. On 18 October the government announced that the project was being abandoned.
Power generation potential
The Severn Barrage plans would provide a predictable source of sustainable energy during lifetime of the scheme, 5% of the UK's output from the 10-mile version. This could reduce the cost of meeting UK’s renewable energy targets, and help the UK to meet such targets, including those to tackle climate change. This is because of the few carbon emissions associated with the plan, because unlike conventional power generation, the Severn Barrage plans do not involve the combustion of fossil fuelFossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...
s. A consequence of this plan is that the carbon payback time—the time it takes for saved carbon emissions (those produced by generating the same amount of power in other ways) to outstrip those produced during construction— could be as little as four-and-a-half months, although likely to be around six.
It could continue to operate for around 120 years, compared with 30–40 years for nuclear power plants. An additional benefit would be to improve energy security
Energy security
Energy security is a term for an association between national security and the availability of natural resources for energy consumption. Access to cheap energy has become essential to the functioning of modern economies. However, the uneven distribution of energy supplies among countries has led...
.
However, although power supply is predictable, peaks in generation from the barrage do not necessarily coincide with peaks in demand. There are two major tidal cycles affecting power output:
- semi-diurnal cycle: the familiar daily rise and fall of the sea with a full cycle every 24 hours and 50 minutes, with two high and low tides, giving maximum power generation opportunities a few hours after each of the two high tides;
- spring-neap cycle: a 29.5 day tidal range cycle with the lowest power days producing about 25% of the power of the highest power days.
Just under eight hours per day of generation time is expected.
Construction costs
Estimated costs for existing plans could be as low as £10bn and as high as £34bn. Recent studies have suggested that the smaller short-listed options could be privately financed, and so in effect the matter of cost and risk becomes a private one between the building consortiumConsortium
A consortium is an association of two or more individuals, companies, organizations or governments with the objective of participating in a common activity or pooling their resources for achieving a common goal....
and their banks. Schemes of the scale of Cardiff-Weston are likely to require significant Government
Government
Government refers to the legislators, administrators, and arbitrators in the administrative bureaucracy who control a state at a given time, and to the system of government by which they are organized...
involvement. If the bank
Bank
A bank is a financial institution that serves as a financial intermediary. The term "bank" may refer to one of several related types of entities:...
s feel that a smaller project is viable and decide to lend the money at an acceptable cost of finance then the projects will go ahead (subject to planning and other approvals). None of this cost would directly fall on the tax
Tax
To tax is to impose a financial charge or other levy upon a taxpayer by a state or the functional equivalent of a state such that failure to pay is punishable by law. Taxes are also imposed by many subnational entities...
-payer but any support mechanism for the tidal power would be likely to fall on consumer
Consumer
Consumer is a broad label for any individuals or households that use goods generated within the economy. The concept of a consumer occurs in different contexts, so that the usage and significance of the term may vary.-Economics and marketing:...
s. There would though be secondary knock-on costs from the tidal power project that might be met by the tax-payer, such as modifying existing port
Port
A port is a location on a coast or shore containing one or more harbors where ships can dock and transfer people or cargo to or from land....
s, provision of compensatory habitat and dealing with environmental change. However, these would be offset by the positive knock-on effects, such as flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
protection - which would have otherwise also cost tax-payer money. Whether the parties actually decided to exchange money for these knock-on effects would be a matter for Government negotiation.
Local impact
Any large-scale barrage would create leisure-friendly water conditions behind it. FloodFlood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
protection would be provided by the barrage, covering the vulnerable Severn estuary from storm surges from the sea. New road and/or rail transport
Transport
Transport or transportation is the movement of people, cattle, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations...
links could be built across a barrage if demand rises in the future, as outlined below. Any barrage could provide a boost to the local economy
Economy
An economy consists of the economic system of a country or other area; the labor, capital and land resources; and the manufacturing, trade, distribution, and consumption of goods and services of that area...
— construction industry in the short term, tourism and infrastructure in the long term.
However, shipping
Shipping
Shipping has multiple meanings. It can be a physical process of transporting commodities and merchandise goods and cargo, by land, air, and sea. It also can describe the movement of objects by ship.Land or "ground" shipping can be by train or by truck...
would have to navigate locks, and existing estuary industries, including fisheries, would be damaged and jobs lost. All industrial discharges into the River Severn (e.g. from Avonmouth
Avonmouth
Avonmouth is a port and suburb of Bristol, England, located on the Severn Estuary, at the mouth of the River Avon.The council ward of Avonmouth also includes Shirehampton and the western end of Lawrence Weston.- Geography :...
) would have to be reassessed.
Environmental impact
The Severn Estuary is a Special Area of ConservationSpecial Area of Conservation
A Special Area of Conservation is defined in the European Union's Habitats Directive , also known as the Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora...
due to the European importance of its ecology. The inter-tidal area provides food for over 85,000 migratory and wintering water birds, and represents 7% of the UK's total estuaries. There are nature reserve
Nature reserve
A nature reserve is a protected area of importance for wildlife, flora, fauna or features of geological or other special interest, which is reserved and managed for conservation and to provide special opportunities for study or research...
s and Site of Special Scientific Interest
Site of Special Scientific Interest
A Site of Special Scientific Interest 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 upon...
(SSSI) on the islands of Flat Holm
Flat Holm
Flat 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....
and Steep Holm
Steep Holm
Steep Holm is an English island lying in the Bristol Channel. The island covers at high tide, expanding to at mean low water. At its highest point it is above mean sea level. It lies within the historic boundaries of Somerset and administratively, it forms part of North Somerset...
.
The Barrage was not supported in the 2003 Energy Review due to "strong environmental concerns" (The same paper also described nuclear power as "an unattractive option").
The RSPB opposes any Severn Barrage because of the effect it will have the feeding grounds 85,000 birds depend on, stating "The impact a barrage would have is huge. This is one of the most important sites in the UK for wild birds and the chances of them surviving if it went ahead are fairly slim. There wouldn't be enough room left for all the birds and there wouldn't be enough food for those that remained. The estuary is one of the UK's most important sites for water birds and its wildlife value must be taken fully into account."
The present strong tidal currents in the estuary serve to lift up silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
and so keep the water thick with fine particles. This blocks light-penetration and means that the Severn Estuary marine
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
environment is actually a relative desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
, in terms of both plant and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
life.
The barrage will not create a "lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
" - as both opponents and supporters have sometimes claimed. Tidal power stations by definition require that the tide flows through the barrage, but the tidal range in the Severn would be halved. There are claims that the migration of fish would be hampered, but these are contested. The Severn bore
Severn bore
The 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 :...
would also be eliminated. Any barrage would be likely to stimulate coastal erosion
Coastal erosion
Coastal erosion is the wearing away of land and the removal of beach or dune sediments by wave action, tidal currents, wave currents, or drainage...
in some areas, and create a negative visual impact upon the landscape (subjective, similar to wind turbines). There would also be negative consequences of the huge amount of concrete (and other materials) needed, with the quarrying of stone likely to impact on other areas.
DEFRA claims that the environmental effects
Environmental science
Environmental science is an interdisciplinary academic field that integrates physical and biological sciences, to the study of the environment, and the solution of environmental problems...
of the barrage still need more analysis before final conclusions can be drawn. The Sustainable Development Commission
Sustainable Development Commission
The Sustainable Development Commission was a non-departmental public body responsible for advising the UK Government, Scottish Government, Welsh Assembly Government, and Northern Ireland Executive on sustainable development....
is investigating UK tidal resources, including tidal power in the Severn Estuary and its environmental impact, and should report mid-2007.
Tidal lagoon alternative
Friends of the EarthFriends of the Earth
Friends of the Earth International is an international network of environmental organizations in 76 countries.FOEI is assisted by a small secretariat which provides support for the network and its agreed major campaigns...
support the idea of tidal power, but oppose barrages because of the environmental impact. They have proposed their own plans based on the concept of tidal lagoons,
whereby man-made lagoons in the estuary would fill and drain through turbines. Their proposals would include lagoons covering up to 60% of the area covered by the barrage, which in some smaller configurations would not impound water in the ecologically sensitive inter-tidal areas of the estuary. The lagoons could be sub-divided so power would be generated at more states of the tide than a barrage, with lower peak output, giving economic advantages to set against the higher construction cost of longer barriers. This idea is based on a prototype now being designed at Swansea
Swansea
Swansea is a coastal city and county in Wales. Swansea is in the historic county boundaries of Glamorgan. Situated on the sandy South West Wales coast, the county area includes the Gower Peninsula and the Lliw uplands...
bay. However leading figures in the construction industry are sceptical that the lagoons can be economic.
A set of Tidal lagoons known as the "Russell Lagoon concept" were studied and dismissed by the 1981 Bondi Committee report, rejected on the grounds of both economics and environmental damage. Studies suggested that tidal currents around and between the lagoons would become extremely fierce and damaging.
Tidal Fence
Another possibility is to construct one or more tidal fences across the Severn estuary which would generate power using tidal stream generatorTidal stream generator
A tidal stream generator, often referred to as a tidal energy converter is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites...
s. This has been put forward by the Severn Tidal Fence Consortium, a group led by IT Power and including a number of industry and academic groups.
This would attempt to maximise the potential power generated whilst allowing for shipping to reach Cardiff and Bristol without hindrance (through gaps at least 650m wide) and wildlife to maintain their existing habitats. The group has now been contracted by the UK government to investigate the idea under the Severn Embryonic Technology Scheme (SETS).
The group estimates that it would cost £3.5bn to construct an outer fence from Aberthaw
Aberthaw
Aberthaw is a village of the Vale of Glamorgan west of Barry on the coast of South Wales.The village is split into two halves - East Aberthaw and West Aberthaw, separated by the River Thaw. It is home to Aberthaw Cement Works and Aberthaw Power Station a coal power station plant that was linked to...
to Minehead
Minehead
Minehead is a coastal town and civil parish in Somerset, England. It lies on the south bank of the Bristol Channel, north-west of the county town of Taunton, from the border with the county of Devon and in proximity of the Exmoor National Park...
which would generate 1.3GW or 3.5TWh/year. It is also investigating an inner fence from Lavernock Point to Brean Down including Flat Holm
Flat Holm
Flat 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....
and Steep Holm
Steep Holm
Steep Holm is an English island lying in the Bristol Channel. The island covers at high tide, expanding to at mean low water. At its highest point it is above mean sea level. It lies within the historic boundaries of Somerset and administratively, it forms part of North Somerset...
islands. Both fences could possibly be built.
The fence would permit the migration of salmon and would only slightly affect the mudflats used by migrating birds. In addition it could significantly reduce the flood risk in the Severn estuary.
A second approach to a tidal fence being explored by VerdErg uses a different way of generating electricity called the Spectral Machine Energy Converter (SMEC).
This uses the flow past Venturi tube sections as a pump without moving parts to create a large secondary flow which drives turbines on the sea bed.
Verderg estimate that they could produce output of 13.7TWh/yr at a cost of £9.9bn using the Lavernock Point/Brean Down connection.
Some simulations have also been done on the partial barriers envisaged by Dynamic tidal power
Dynamic tidal power
Dynamic tidal power or DTP is a new and untested method of tidal power generation. It would involve creating large dam-like structure extending from the coast straight to the ocean, with a perpendicular barrier at the far end, forming a large 'T' shape....
which have similar advantages.
Effects of different site locations
One of the complicating factors in assessing the impacts of a barrage is the large number of possible locations and sizes for the barrage. Generally, the larger the barrage the bigger its environmental impact, and the greater the amount of energy it could transfer - and therefore the bigger carbon offsetCarbon offset
A carbon offset is a reduction in emissions of carbon dioxide or greenhouse gases made in order to compensate for or to offset an emission made elsewhere....
it could have by way of its renewable power generation.
The largest barrages (sited beyond Hinkley Point
Hinkley Point
Hinkley Point is a headland on the Bristol Channel coast of Somerset, England, five miles north of Bridgwater and five miles west of Burnham-on-Sea, close to the mouth of the River Parrett....
and towards Minehead
Minehead
Minehead is a coastal town and civil parish in Somerset, England. It lies on the south bank of the Bristol Channel, north-west of the county town of Taunton, from the border with the county of Devon and in proximity of the Exmoor National Park...
on the English side and Aberthaw
Aberthaw
Aberthaw is a village of the Vale of Glamorgan west of Barry on the coast of South Wales.The village is split into two halves - East Aberthaw and West Aberthaw, separated by the River Thaw. It is home to Aberthaw Cement Works and Aberthaw Power Station a coal power station plant that was linked to...
on the Welsh side) would significantly affect the entire Severn Estuary and much of the Bristol Channel, but could generate 15 GW peak power and protect the whole of the Somerset levels against flooding and sea-level rise caused by Global Warming. The smallest barrages (sited at Aust
Aust
Aust is a small village in South Gloucestershire, England, the historical site of the eastern terminal of the Aust Ferry crossing route over the River Severn between England and Wales, believed to have been used in Roman times as a continuation of Icknield Street which led from Eastern England...
/Chepstow
Chepstow
Chepstow is a town in Monmouthshire, Wales, adjoining the border with Gloucestershire, England. It is located on the River Wye, close to its confluence with the River Severn, and close to the western end of the Severn Bridge on the M48 motorway...
) would affect only the river and estuary in Gloucestershire, but would also only generate perhaps 0.75 GW peak power.
Trans-barrage transport links
It is possible that some types of barrage could be used for transport links between southern England and southern Wales, and more specifically the areas around BristolBristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
and Cardiff
Cardiff
Cardiff is the capital, largest city and most populous county of Wales and the 10th largest city in the United Kingdom. The city is Wales' chief commercial centre, the base for most national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for...
. Various proposals include a dual carriageway
Dual carriageway
A dual carriageway is a class of highway with two carriageways for traffic travelling in opposite directions separated by a central reservation...
road giving a further crossing in addition to the Second Severn Crossing
Second Severn Crossing
The 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 HRH The Prince of Wales to augment the traffic capacity of the original Severn Bridge built in 1966...
and the Severn Bridge
Severn Bridge
The 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 road would have to be taken over the sea locks on a bridge at a height of the Bridge of the Americas
Bridge of the Americas
The Bridge of the Americas is a road bridge in Panama, which spans the Pacific entrance to the Panama Canal. Completed in 1962, at a cost of US$20 million, it was the only non-swinging bridge connecting the north and south American land masses until the opening of the Centennial Bridge in 2004...
(i.e. with a clearance of 61.3m) if the locks are Panamax
Panamax
Panamax and New Panamax are popular terms for the size limits for ships traveling through the Panama Canal. Formally, the limits and requirements are published by the Panama Canal Authority titled "Vessel Requirements"...
-sized.
Some proposals also include a double track railway line across the barrage. A railway would have a longer approach up to a fixed bridge over the locks. The approach would be greatest for non-electrified heavy railway capable of taking freight, slightly less for non-electrified passenger line, and less still for electrified passenger line. There is no electrification presently in the Bristol or Cardiff areas, but this would change with the electrification of the Great Western Main Line
Great Western Main Line
The Great Western Main Line is a main line railway in Great Britain that runs westwards from London Paddington station to the west of England and South Wales. The core Great Western Main Line runs from London Paddington to Temple Meads railway station in Bristol. A major branch of the Great...
. An alternative to a fixed bridge would be a swing bridge
Swing bridge
A swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its centre of gravity, about which the turning span can then pivot horizontally as shown in the animated illustration to the right...
, though there is concern expressed at this reducing capacity through the locks and on the railway. However, two swing bridges, one at either end of the lock would mean that one bridge could be kept open to railway traffic at all times. The double track could be reduced to single track at this point without creating too much of a bottleneck, or if double track is required this could be worked around by grade separating the two lines and having double-decked bridges. The line could then be used to partially relieve the Severn Tunnel
Severn Tunnel
The Severn Tunnel is a railway tunnel in the United Kingdom, linking South Gloucestershire in the west of England to Monmouthshire in south Wales under the estuary of the River Severn....
.
The option for a new fixed rail link has implications for several wider transport proposals. One of the proposed routes for an Irish Sea Tunnel
Irish Sea Tunnel
An Irish Sea Tunnel is a proposed tunnel that would link the island of Ireland to Great Britain beneath the Irish Sea. It has been suggested in the past largely for political reasons. It would be a railway tunnel, similar to the Channel Tunnel beneath the English Channel...
is from Fishguard, which would generate large amounts of extra freight traffic which the current Severn tunnel - already operating at capacity - could not handle. Additionally, a new high speed rail route has been suggested between London, Bristol, and Cardiff, which faces similar capacity constraints.
Backers
- The former Prime Minister of the United KingdomPrime Minister of the United KingdomThe Prime Minister of the United Kingdom of Great Britain and Northern Ireland is the Head of Her Majesty's Government in the United Kingdom. The Prime Minister and Cabinet are collectively accountable for their policies and actions to the Sovereign, to Parliament, to their political party and...
, Tony BlairTony BlairAnthony Charles Lynton Blair is a former British Labour Party politician who served as the Prime Minister of the United Kingdom from 2 May 1997 to 27 June 2007. He was the Member of Parliament for Sedgefield from 1983 to 2007 and Leader of the Labour Party from 1994 to 2007...
(who backed it in the last weeks of his tenure) - Secretary of State for WalesSecretary of State for WalesThe Secretary of State for Wales is the head of the Wales Office within the British cabinet. He or she is responsible for ensuring Welsh interests are taken into account by the government, representing the government within Wales and overseeing the passing of legislation which is only for Wales...
, Peter HainPeter HainPeter Gerald Hain is a British Labour Party politician, who has been the Member of Parliament for the Welsh constituency of Neath since 1991, and has served in the Cabinets of both Tony Blair and Gordon Brown, firstly as Leader of the House of Commons under Blair and both Secretary of State for... - The Welsh AssemblyNational Assembly for WalesThe National Assembly for Wales is a devolved assembly with power to make legislation in Wales. The Assembly comprises 60 members, who are known as Assembly Members, or AMs...
- The CommonsBritish House of CommonsThe House of Commons is the lower house of the Parliament of the United Kingdom, which also comprises the Sovereign and the House of Lords . Both Commons and Lords meet in the Palace of Westminster. The Commons is a democratically elected body, consisting of 650 members , who are known as Members...
Welsh Affairs Select CommitteeWelsh Affairs Select CommitteeThe Welsh Affairs Select Committee is a select committee of the House of Commons in the Parliament of the United Kingdom... - Welsh First Minister, Rhodri MorganRhodri MorganHywel Rhodri Morgan is a Welsh Labour politician who, as First Secretary for Wales, and subsequently First Minister, was leader of the Welsh Assembly Government from 2000 to 2009. A former leader of Welsh Labour, he was the Assembly Member for Cardiff West from 1999 to 2011...
- The South West Regional AssemblyRegional Assemblies in EnglandThe Regional Assemblies of England were a group of indirectly elected regional bodies established originally under the name Regional Chambers by the Regional Development Agencies Act 1998. They were abolished on 31 March 2010 and replaced by Local Authority Leaders’ Boards...
- Weston Super Mare MP, John Penrose
- Cardiff Central MP, Jenny WillottJenny WillottJennifer Nancy Willott is a British politician and the Liberal Democrat Member of Parliament for Cardiff Central since the 2005 general election. She is the first woman and the first Liberal Democrat to represent her seat....
- Northavon MP, Steve WebbSteve WebbSteven John Webb, better known as Steve Webb , is an English Liberal Democrat politician. He is the Member of Parliament for Thornbury & Yate and the Minister of State for Pensions.-Background:...
- Ogmore MP and Parliamentary Under Secretary of State for Wales, Huw Irranca-DaviesHuw Irranca-DaviesIfor Huw Irranca-Davies , born Ifor Huw Davies, is a British Labour Party politician, who has been the Member of Parliament for Ogmore since 2002...
- Kingswood MP, Roger BerryRoger BerryDr Roger Leslie Berry is a British Labour Party politician, who was the Member of Parliament for Kingswood from 1992 to 2010.-Early life:...
- BristolBristolBristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
City Council has passed a motion calling for an urgent reappraisal - Bristol West MP, Stephen WilliamsStephen Williams (politician)Stephen Roy Williams is a British Liberal Democrat politician who was first elected as the Member of Parliament for Bristol West in the 2005 general election, being re-elected with an increased majority in May 2010...
has also said that the project must be urgently investigated, and has proposed an EDM on the subject - North SomersetNorth SomersetNorth Somerset is a unitary authority in England. Its area covers part of the ceremonial county of Somerset but it is administered independently of the non-metropolitan county. Its administrative headquarters is in the town hall in Weston-super-Mare....
Council has also called for a new appraisal - Scientist and "GaiaGaia hypothesisThe Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet.The scientific investigation of the...
" theorist, Dr James LovelockJames LovelockJames Lovelock, CH, CBE, FRS is an independent scientist, environmentalist and futurologist who lives in Devon, England. He is best known for proposing the Gaia hypothesis, which postulates that the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling...
CBE - The Minister for Local Environment, Marine and Animal Welfare at Defra, Ben BradshawBen BradshawBenjamin Peter James Bradshaw is a British Labour politician who has been the Member of Parliament for Exeter since 1997, and served in the Cabinet as Secretary of State for Culture, Media and Sport....
- The then Secretary of State for Environment, Food and Rural AffairsSecretary of State for Environment, Food and Rural AffairsThe Secretary of State for Environment, Food and Rural Affairs is a UK cabinet-level position in charge of the Department for Environment, Food and Rural Affairs, and the successor to the positions of Minister of Agriculture, Fisheries and Food and Secretary of State for the Environment, Transport...
, David MilibandDavid MilibandDavid Wright Miliband is a British Labour Party politician who has been the Member of Parliament for South Shields since 2001, and was the Secretary of State for Foreign and Commonwealth Affairs from 2007 to 2010. He is the elder son of the late Marxist theorist Ralph Miliband...
, has said that the project "Has to be worthy of very serious consideration" - The former Secretary of State for Trade and IndustrySecretary of State for Trade and IndustryThe Secretary of State for Business, Innovation and Skills is a cabinet position in the United Kingdom government. Its secondary title is the President of the Board of Trade...
, Alistair DarlingAlistair DarlingAlistair Maclean Darling is a Scottish Labour Party politician who has been a Member of Parliament since 1987, currently for Edinburgh South West. He served as the Chancellor of the Exchequer from 2007 to 2010...
Opponents
- Save Our Severn
- Former UK Science Minister, Lord SainsburyDavid Sainsbury, Baron Sainsbury of TurvilleDavid John Sainsbury, Baron Sainsbury of Turville, FRS , is a British businessman and politician. From 1992 to 1997, he served as the Chairman of Sainsbury's . He was made a life peer in 1997, and currently sits in the House of Lords as a member of the Labour Party...
- Woodspring MP, Liam FoxLiam FoxLiam Fox MP is a British Conservative politician, Member of Parliament for North Somerset, and former Secretary of State for Defence....
- Bristol Green PartyGreen Party (UK)The Green Party was a Green political party in the United Kingdom. It has been succeeded by three political parties:* the Green Party of England and Wales* the Green Party in Northern Ireland* the Scottish Green Party- PEOPLE, 1973–1975 :...
- Gloucestershire Green Party
- South West Green Party
- RSPB Wales
- Friends of the EarthFriends of the EarthFriends of the Earth International is an international network of environmental organizations in 76 countries.FOEI is assisted by a small secretariat which provides support for the network and its agreed major campaigns...
Wales - World Wildlife Fund Wales
- Gwent Wildlife TrustGwent Wildlife TrustGwent Wildlife Trust is a wildlife trust covering the area between the lower Wye and Rhymney rivers which forms the vice county of Monmouthshire in south-east Wales. It is a registered charity and a member of the Wildlife Trusts Partnership.-History:...
- Avon Wildlife TrustAvon Wildlife TrustThe Avon Wildlife Trust aims to protect and promote wildlife in the area of the former county of Avon — now Bath and North East Somerset, Bristol, North Somerset and South Gloucestershire, in England...
- Political commentator, George MonbiotGeorge MonbiotGeorge Joshua Richard Monbiot is an English writer, known for his environmental and political activism. He lives in Machynlleth, Wales, writes a weekly column for The Guardian, and is the author of a number of books, including Captive State: The Corporate Takeover of Britain and Bring on the...
See also
- Energy policy of the United KingdomEnergy policy of the United KingdomThe current energy policy of the United Kingdom is set out in the Energy White Paper of May 2007 and Low Carbon Transition Plan of July 2009, building on previous work including the 2003 Energy White Paper and the Energy Review Report in 2006...
- Energy use and conservation in the United KingdomEnergy use and conservation in the United KingdomEnergy use in the United Kingdom stood at 3,894.6 kilogrammes of oil equivalent per capita in 2005 compared to a world average of 1,778.0. In 2008, total energy consumed was 9.85 exajoules - around 2% of the estimated 474 EJ worldwide total...
- Tidal powerTidal powerTidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
- List of tidal power stations
- Saint Petersburg DamSaint Petersburg DamThe Saint Petersburg Flood Prevention Facility Complex , unofficially the Saint Petersburg Dam, is a complex of dams for flood control near Saint Petersburg, Russia...
External links
- Department of Energy and Climate Change
- Welsh Assembly Government
- Severn Estuary Partnership: Tidal Power Resource Page"
- SDC paper "Tidal Power in the UK: Research Report 3 - Severn barrage proposals"
- Friends of the Earth "Tidal Lagoons" Plans
- BBC Gloucestershire background videos and information
- Severn Lake Official Website
- World Wildlife Fund "Turning the Tide"
- Severn Tidal Power Group report for UK Government DTI
- Institute of Civil Engineers Severn Barrage environmental reappraisal
- Estuary energy plan makes waves The Guardian 26 April 2006
- Institute of Electronic Engineers Severn Barrage Tidal power appraisal
- Memorandum by the Severn Tidal Power Group to Parliamentary Committee
- Standing Conference on Severnside Local Authorities (SCOSLA)
- Westminster Hall Debate on the Severn Barrage
- Sustainable Development Commission project looking at 'Tidal Power in the UK'