A Barrage Too Far? Green energy will cost too much

Hulks on the SevernOn 27th January 2009, the Government announced a shortlist of 5 schemes, from an original list of 10 options, to construct a tidal barrage across the river Severn between south Wales and England. The most ambitious is a 10 mile concrete and rock wall extending from Brean Down in Somerset to Cardiff. This would cost around £15 billion, is estimated produce around 8 gigawatts of electricity – around 5% of the current national consumption. The other alternatives include 2 much smaller barrages close to the line of the Severn Bridges, and two tidal lagoons on the Welsh and English sides. Clearly this is very green energy, but we as archaeologists should be concerned because these schemes will do irreparable to the historic environment.

The Severn Estuary is one of the richest, still largely unstudied archaeological resources in the United Kingdom. The extraordinary tidal range of nearly 50 feet, is the second highest in the world, and means that there is an extensive and ever-changing inter-tidal zone. The massive currents create scouring and erosion, continuously revealing new and unknown archaeological sites and features. The Severn Estuary and Levels Research Committee have studied several over the years, and the discoveries of Martin Bell and John Allen of Reading University are particularly well known. Over the last 20 years the estuary has revealed evidence for Mesolithic footprints, prehistoric settlements, prehistoric, Roman and medieval ships, Roman ironworking sites and settlements, as well as more recent activities such as quays, fish traps and hulks. Sites such as Wentloodge levels and Magor are well known for providing a completely new insight into the prehistoric coastal economies of southwest Britain.

The English side of the estuary is much less well studied than the Welsh, but an indication of the scale of the threat is shown by a recent, survey of the Gloucestershire and Somerset side of the estuary funded by English Heritage based largely on air photography, identified over 348 prehistoric, 186 Roman, 631 medieval and 1798 post medieval sites (see http://www.gloucestershire.gov.uk/index.cfm?articleid=12558). The survey identified 9 areas where the deposits were of national or greater significance; of these 8 will be directly affected by one or other of the barrage schemes. In reality the archaeological resource is many times larger than these figures suggest – we need to think of the Estuary as some 150 miles of continuous archaeological landscape. The proposed barrages will have a catastrophic impact on this archaeology.

The 10-mile scheme threatens the English site at Brean Down: one of the classic archaeological sites of Britain currently managed by the National Trust. The site comprises sensitive archaeological remains from the Bronze Age to the Napoleonic era. Construction work at Brean Down is likely to have a huge impact on these remains, while its scenic quality jutting out into the Estuary will be lost forever.

Equally worrying but much more difficult to assess is the impact of the change of sea level within the barrage. While there will still be a ‘tide’, its range will be very much smaller, like a neap tide, rather than the huge range of spring tides. In consequence the land now covered by spring tides will dry out and turn from salt marsh to pasture. This ‘drying out’ will mean a huge swathe of organically preserved material and deposits will be lost; probably the largest acreage of loss of an archaeological resource ever to have taken place in this country.

The story at low tide is equally grim. Because the tide will not achieve the current low levels, where most of the archaeological material is currently exposed, it will never again be available for archaeological study. A small consolation is that it will probably survive, until the barrage is abandoned in 100’s of year’s time!

There is however a much bigger story as to why we need to oppose the barrage proposals. The Severn Estuary is an extraordinary natural phenomena; it has an amazing tidal range with an ever-changing landscape, as the tide comes in and goes out, sometimes with currents of over 15 miles an hour. The light shimmering on the sand-flats, and the extraordinary sunsets across this huge expanse of water will be changed forever. The huge and rich wildlife that uses the salt marshes will be radically affected and of course the Severn bore will disappear.

There are alternatives. A range of new technologies are being developed, to harness the tide using underwater reefs, turbines and tide generators. These could be used, but the government is much less keen to explore these alternatives and none of them made it to their final shortlist. Clearly the big barrage is a highly attractive project to help to solve our renewable energy target by 2020, but the cost to the wider environment, both natural and historic, will be devastating.

Mark Horton, Dept of Archaeology and Anthropology
University of Bristol

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