The Severn Barrage has been mooted for a number of years; since Thomas Fulljames proposed such a structure between Beachley and Aust (the route of the century’s old ferry and first road bridge built in the 1960s) in 1849. His plan was envisaged as a means of flood alleviation and the location for both a port and a crossing place that would service the needs of both South Wales and the West of England. The scheme never achieved any momentum but in 1925 the government commissioned a study into the potential uses of the tidal range of the river which is the second largest in the world, second only to the Bay of Fundy in Canada.
The River Severn’s tidal range is in excess of 14 metres (46 feet).
This commission put forward a proposal to use this large tidal differential for the generation of 800 megawatts of electricity. The project was considered technically feasible but was not taken forward due to the £25 million estimated cost. In 1931 a Russian émigré, Paul Shishkoff, demonstrated a 220 kilowatt tidal generator at Avonmouth, the estimate for its placement across the Severn Estuary was far less costly at £5 million. Lord Brabazon, chairman of the Severn Barrage Committee set up in 1933 recommended an 800 megawatt producing barrage and plans were agreed with the government, but World War II forced the scheme’s abandonment.
After the war the scheme was resurrected in various guises; 1948, 1953, 1971, 1975 and 1981. This later plan spurred on by the oil crisis of the time was promulgated by the government committee chaired by Sir Hermann Bondi. The committee’s research considered 6 options for the barrage location from English Stones to Lynmouth and finally recommending Brean Down to Lavernock Point. This scheme location was again favoured in 1989 by the Severn Tidal Power Group.
Meanwhile in 1983 WS Atkins and Wimpey put forward schemes for a smaller generation operation and shorter span located at English Stones, which had added advantages of requiring smaller locks as shipping upstream of the docks at Avonmouth was carried out by much smaller vessels heading in and out of the ports of Lydney and Gloucester.
In 1989 the Severn Tidal Power Group which included several major construction and technology companies including McAlpine, Balfour Beatty, Woodrow and Alstom who after consideration of tidal power schemes in France (Rance), Canada (Annapolis) and the sea barrages in the Netherlands that the Severn could generate an average output 2,000 MW with peaks above 8,500MW. The scheme would have put in place 216 turbines, each producing 40MW at maximum production. The prospective lifespan of the barrage was expected to be over 200 years. The environmental impact was seen by the Group as acceptable but the project was shelved by the Tory government of the day as being too sensitive an environmental issue.
Some Barrage locations.
In 2007 with renewable energy as a desirable option as a result of the UK government’s acceptance of global warming and the realisation that imported fuel was now outside the control of Her Majesty’s Government again the Severn offered up two new scheme; one a tidal reef, designed by Rupert Evans, which would only interfere with the ebb and flow of the estuary in a much more minor manner stretching from Minehead to Aberthaw. The other, far larger, stretching a shorter distance across the estuary from Weston to Cardiff. This latter proposal was put together by the government sponsored Sustainable Development Commission. This latter scheme getting the government’s full attention, with the Department for Energy and Climate Change in 2011 developing a relationship with Corlan Hafron a private sector consortium to develop a funding package.
The acceptance by the government that the barrage could produce around 5% of the nation’s energy needs and go some way to ensuring a sustainable basic supply of carbon negative energy over a long time period of at least 120 years, treble the lifespan of the proposed new nuclear power station at Hinckley Point. It would also assure energy security in the face of the UK having to chase EU carbon reduction targets.
The present Hinckley Point Power Station.
In 2012 it was first brought to the attention of ministers of HMG that though tidal power was totally reliable and would generate the maximum and minimum loads on time, that time would vary. That tides were on a semi-diurnal cycle: the daily rise and fall of the sea running a full cycle every 24 hours and 50 minutes. This being two high and low tides which would allow peak generation a few hours after each of the two high water events. Alongside this the tides also have a spring-neap cycle that over a 29.5 day period the lowest power capability would be approximately 25% of that at the highest tide period of the month.
The Severn Bore would be disappear.
This realisation has coursed the British Government to stall again with a predisposition to walk away from the project in as much as public finance might be involved and has left the environment lobby at a loss. That is in as much as the lobby, particularly Friends of the Earth are predisposed to tidal power generation. FoE have gone as far as putting forward a scheme involving tidal lagoons within the estuary that could be used to generate power at more desirable times during the tidal cycles; at the same time protecting much of the internationally important tidal mudflats that are crucial to the welfare of many wintering populations of wading birds. With regard to some of the new proposals for the barrage; not just that favoured by FoE the RSPB had seen a possibility to increase wader feed populations in the muds of the estuary caused by the lessening of the river’s turbidity and the increase of light levels able to filter through to the muds.
The other and possible more fundamental reasons for the apparent governmental volte-face has been triggered by the reported volume of shale gas that is now believed to be exploitable within the strata of the UK and the significant agreement with France and China to build the first new generation nuclear power plant at Hinckley Point overlooking the Severn Estuary in Somerset. In previous times North Sea oil and gas were seen as the reason for not going down the barrage route in a similar way as it appears to be that security of energy is in measure being thought of as solvable by using the less polluting fossil fuels such as shale and tight gas, rather than going further with major investment in new technologies of tidal power capture in one of its growing number of forms.
The Severn Barrage is not dead with the government still supportive of the many benefits to the communities that lives along the banks of the river upstream of the structure; particularly when looking to future effects of global warming and climate chaos. The most significant being a control on flooding of urban areas and farmland. Alongside these considerations the possibility of developing a greater area of ecological benefit to overwinter migratory waders would be considered beneficial as would the employment potential brought about by the creation of the vast managed water body on the inland side of the structure as a recreational and tourist resource.
The private sector infrastructure element is developing a partner base under the partnership heading Corlan Hafren to bring about the definitive design, specifications, costings and funds to build the barrage.
There have in the last year been a plethora of proposed locations from the vast; Devon to Wales, structure estimated by Atkins to be capable of producing up to 15% of UK power needs at peek production and Chepstow to Aust which today would make little sense with regard to power generation at less than 0.25% of UK need at best.
The First Seven Bridge on the site of the Old Ferry Route between Beachley and Aust. Aust Cliffs can be seen clearly.
The ecological backlash would be mixed, depending on the final proposed methodology, the final location decided on and the compensatory habitats that would be put in place to negate the inevitable changes to the natural tidal mud banks and estuarine marshes. This though is now far smaller in scale than was initially anticipated due to the ability for greater mud and sand bank fauna populations to increase markedly due the reduction in water turbidity even into the Bristol Channel and beyond under the influence of the barrage.
There is much to recommend the development of such a scheme but equally much that can detract from it. To date it has produced many millions of words in reports and papers and has like the tide the barrage wants to harness gone back and forth for nearly two hundred years; the prospect is still unclear with the arguments continue to be muddied by the undiminishing number of options being dreamt up annually by various of the interested parties. Time might tell.
The Estuary at English Stones.