The Ebb and Flow of Energy An Environmental History of Tidal Power in the Severn Estuary, Southwest Britain

The macrotidal Severn Estuary (>4m tidal range) represents the point at which the longest river in Britain (220 miles) meets the Bristol Channel and, in turn, the Atlantic. Since the mid-19th

century the estuary has been the subject of debate over harnessing its tides to generate electricity. By constructing a barrage (a type of dam), proponents argue that - in the 21st century at least -up to 5% of UK energy demand could be met. As a renewable source, the tides could also ensure a sustainable power supply for up to 120 years. Uses of the Severn’s tides are, however, nothing new. Inhabitants of the lands bordering this liminal environment – a region that can shift from a river to an extension of the sea in minutes (the surfable “Severn Bore” - above) – have interacted with the tidal cycle for millennia; from medieval fish traps, to the Severn Trow (a type of flat-bottomed trading vessel unique to the estuary) and tide mills. And yet, even with such a heritage of human-tidal relations, barrage proposals have stimulated resistance and polarised views on how the estuary should be used and managed. My research seeks to understand how, even with so many proposals, a Severn Barrage has remained elusive, and why, despite such a lack of success, interest in employing the tides shows little sign of abating. This has been achieved through application of analytical tools developed in environmental history – e.g. the notion of envirotechnical systems and Richard White’s “organic machine” - in addition to scalar approaches more commonly employed by geographers. Insights have also been derived from archaeology, while spatial history and GIS have assisted in organising research and visualising proposed pasts and potential futures.

Before the BarrageEfforts to harness the tides as a source of energy have been a feature of the Severn since at least the 1st millennium AD. The remains of intertidal fish weirs have been 14C-dated to that time, and documentary sources attest to the ownership of fishing structures (“fixed engines”) by monasteries and secular lords in the medieval period. Trading vessels navigating between ports and landing places in the Bristol Channel would also have relied on the tidal rise and fall to convey their cargoes up the many creeks (“pills”) to settlements further inland. The majority of these watercourses are now blocked by sluices and tidal flaps, rendering formerly coastal settlements effectively land-locked. Additionally, tide mills are likely to have been present in the region from the mid-14th century, if not earlier. These can all be interpreted as small-scale envirotechnical systems: examples of human-built technological features that were successfully constructed and put into operation – a marked contrast to the more ambitious but still unrealised barrage.

“Blessings of Light, Purity and Power:” Severn Barrage proposals from 1849 to the presentAlthough interest in damming the Severn may have emerged in the 18th century, the earliest known depiction of a barrage dates to 1849. This is a painting of a crenelated dam to impound water upstream for improved navigation, and for railway communication between England and Wales, but not to generate electricity. It wasn’t until 1904 that hydroelectric schemes were first considered, but in so doing they would initiate a process, and a debate, that would persist unbroken down to the present. Throughout this period proposals have been made by independent engineers, private construction firms and university academics, with occasional feasibility studies by government departments. Plans and technical diagrams demonstrate an increase over time in the size and complexity of proposed structures and provide some explanation for the varied opposition that has emerged, including conservation groups, tidal bore surfers, port authorities and coal mining unions. For many of these stakeholders, the scale of the proposals - in terms of area of water impounded, predicted loss of intertidal habitat for migrating waterbirds, length of time taken to build and high capital cost - have all been too great.

Beyond the Barrage?Despite proposals never progressing beyond the design and feasibility stage, the Severn remains central to research into tidal energy technologies. New designs for barrages, and the less obtrusive tidal reef, have been put forward recently. However, it is the devices that encompass smaller scales – temporal (the time they would take to build), spatial (the area they would occupy), and financially (they’re cheaper) – that seem to be achieving greater success. This might be seen as a return to the more modest envirotechnical systems of the deeper past: the tide mills of the 21st century.

This research is part of the AHRC (Arts and Humanities Research Council) project “The Power and the Water: Connecting Pasts and Futures,” involving the Universities of Bristol, Nottingham and Cambridge. Other components include an environmental history of the River Tyne in NE England, the development of the British National Grid system, the past and future of lead mining soughs in the Peak District, and recreational uses of water. www.powerwaterproject.net.

A wooden vessel, possibly a Severn Trow, hulked on the foreshore. This forms part of a “ships graveyard” created to reinforce the riverbank and provide protection to

the Gloucester and Sharpness canal: an alternative route that enabled watercraft to bypass the treacherous upper estuary.

Photo: Alexander Portch

Intertidal fishing has taken place around the Severn Estuary for millennia. Here a row of baskets known as “putts” is arranged as a “fixed engine” extending towards

the centre of the channel. Their ability to catch fish relied on the motive force provided by the tidal cycle – a small, local-scale envirotechnical system combining

human labour with “natural” materials and processes. Source: Gloucestershire Archives D4764/4/31

Two plans for a Severn Barrage overlain on modern Ordnance Survey maps. To the SW is the design put forward by the government-sponsored Severn Barrage Committee in 1933. To the NE is

a smaller proposal by independent engineers in 1918. Map: Alexander Portch.

Sources: Gloucestershire Archives K1444; The National Archives POWE 2/21/2.

Selected References

Primary Sources: -Economic Advisory Council, Severn Barrage Committee: Report (London, 1933).Gloucestershire Archives D4764/4/31: ‘River Severn: Whale beached at Littleton-on-Severn, 1885; trow [early 20th Cent.]; salmon fishing [early – mid 20th Cent.]; Beachley ferry and Lloyd Lighthouse [1920s – 40s]; Severn railway and vehicle bridges [early 20th Cent. And 1970s].’Gloucestershire Archives K1444: ‘Six drawings published by HMSO to accompany the report of the Severn Barrage Committee.’The National Archives POWE 2/21/2: Ministry of Power: ‘Minutes of Evidence by C.S. Meik, J.W. Twinberrow and G.L. Addenbrooke (1918).’

Secondary Literature: -Chadwick, A.M. and Catchpole, T., ‘Casting the net wide: mapping and dating fish traps through the Severn Estuary rapid coastal zone assessment survey,’ Archaeology in the Severn Estuary, 21 (2010), 47 – 80.Green, C., Severn Traders: The West Country Trows and Trowmen (Witney, 1998).Pritchard, S., Confluence: The Nature of Technology and the Remaking of the Rhone (Cambridge, MA, 2011).White, R., The Organic Machine: The Remaking of the Columbia River (New York, 1995).

Alexander PortchDepartment of History, University of Bristol, UK

ap13925@bristol.ac.uk