Tag Archives: estuary

Environmental History of Tidal Power in the Severn Estuary

Plan for Severn Barrage

Thomas Fulljames’ watercolour of his plan for the Severn Barrage, 1849.
Source: Wikimedia Commons

In recent decades the interest in renewable energy from sources such as wind, solar and tidal power has steadily increased. However, this interest in harnessing “mother nature’s” energy is not new. Over the past 160 years the Severn estuary has been the focus of numerous proposals to provide a transport route over the estuary, improve navigation and to exploit its large tidal range to generate electricity. As a potential source of predictable, renewable and carbon-free power with the potential to supply up to 5 per cent of current UK electricity needs, such interest is understandable. Despite its potential, the latest proposals, like all its predecessors in the past century and a half, have failed to secure government and public support to build a barrage in the Severn estuary.

How is it that a barrage still has not gone beyond the drawing board? And why are companies, scientists and politicians still willing to invest time, effort and money in further proposals?  Alexander Portch, a PhD candidate in the Department of History at Bristol University, investigates these two questions. Although the past 150 years is the main focus, Alexander also investigates earlier efforts to harness tidal power of the Severn and how the activities of people whose lives were bound up with the estuary’s daily tides have shaped the estuary and lands bordering it. This episode of the podcast features an interview with Alexander Portch and his work on the history of the Severn Estuary.


Further reading and resources

Blog posts by Alexander Portch on the Power and the Water website.

Severn Barrage Tidal Power”, The Renewable Energy Website

The Severn Bore website

Charlier, R.H., Menanteau, L., ‘The Saga of Tide Mills,’ Renewable and Sustainable Energy Reviews, 1:3 (1997), 171 – 207.

Godbold, S., Turner, R.C., Hillam, J., Johnson, S., O’Sullivan, A., ‘Medieval Fishtraps in the Severn Estuary,’ Medieval Archaeology, 38:1 (1994), 19 – 54.

Video showing example of tidal mill: Craftsmen: The Tide Miller, 1951 Woodbridge, Suffolk.


Music Credits

Stockholm” by timberman, available from ccMixter

Begin (small theme)” by _ghost, available from ccMixter

Easy Killer (DGDGBD)” by Aussens@iter, available from ccMixter

Exploring environmental History podcast


This podcast was simultaneously published on the Environmental History Resources website as part of the Exploring Environmental History podcast series.

Plastic Oceans: Connectivities of waste

By Marianna Dudley

Bristol-based Power & Water researchers have been exploring the inter-tidal river banks at Sea Mills, a suburb of Bristol where the River Trym meets the Avon and flows to the Severn estuary. PDRA Jill Payne lives locally, and has observed the extent of plastic waste on the riverbanks, deposited daily by the tides and quickly subsumed into the riverine landscape thanks to fast-growing grasses that cover the waste. The plastic detritus is not biodegradable, however.[1] When we walk on the riverbank, plastics, polystyrene and glass crunch underfoot. The riverbank is impregnated with rubbish.

plastic rubbish

A small selection of some of the plastic debris picked up by project members during a riverbank forage at Sea Mills, Bristol (Photo: Marianna Dudley)

Marine waste is a truly global issue, due to the processes of production, consumption and distribution that connect people, places and plastics. I was vividly reminded of this recently, when, days after exploring Sea Mills (where marine litter such as deep-sea fishing crates is brought in on ocean currents and tides to land alongside more local detritus – drinks cans, shopping trolleys, etc) with Jill, I found myself contemplating marine litter on a beach in Bali (another feat of global connectivity). I’ve been there before, and recalled the beautiful beaches, lush vegetation and warm waters that contribute to the ‘island paradise’ reputation. What I’d forgotten (or blocked from my mind) is that the paradise is marred by plastic waste, on the streets, on the beaches, and in the seas. Where traditional waste management methods of burning rubbish coped with localized, largely vegetal trash, in a swiftly developing economy and society such practices are inadequate. Increasingly, plastic waste that doesn’t burn easily gets dumped, and washed into watercourses. The situation on Bali has been greatly amplified by the waste generated by its tourism industry. Tourists are advised not to consume tap-water, and in the tropical heat, guzzle bottles of water instead to stay hydrated. But with no island-wide waste collection or recycling scheme, the bottles pile up, or end up in the ocean, along with plastic bags and other non-biodegradable items. Here they meet plastics that have washed up from Java, and further afield. When surfing or snorkeling in Balinese waters, these plastic presences are visible and unavoidable. To give a sense of the scale of the issue facing the island, Bali expects to receive 4 million foreign visitors in 2015[2]. That’s an awful lot of plastic bottles yet to be consumed and discarded.

My experiences in Bali connected with my involvement in project activities at home, particularly working with Jill to develop ideas for public engagement that address the issue of marine litter, as it figures in the lives and landscapes of Bristolians.   My previous mental blocking out of the plastic problem on Bali’s beaches encouraged me to reflect, this time round, on expectations of landscape and beauty, vs. realities of responding to environmental problems.

In Bali, I found innovative and committed activism bringing communities of locals, expats and tourists together. I visited the Green School in Ubud, where green values are at the heart of a holistic approach to education that has been commended by UN Secretary General Ban Ki Moon (who visited in 2014). Two Green School students, Isabel, 12, and Melati, 13, have led a Bye Bye Plastic Bags campaign that has accrued over 60,000 signatures to date, and have succeeded in persuading the Governor of Bali, Bapak Made Mangku Pastika, to sign a Memorandum of Understanding to take measures to minimize plastic bag use on the island by 1 January 2016. Their dream is for Ngurah Rai International Airport to greet tourists with the words: ‘Welcome to Bali, do you have any plastic bags to declare?’[3] In Bali, student-led activism is making a difference, though it may take time for change to become tangible.

Tourists are also being made aware of their plastic footprint thanks to cafes, restaurants, hotels and guesthouses engaging with anti-plastics campaigning. Guests are encouraged to refill old water bottles (at a cheaper rate than buying a new bottle) or invest in a resusable (non-plastic) container and say no to the always-offered plastic carrier bag when possible. Though the visibility of the plastic problem is evident in Bali, so too are the responses to it.

Visibility is a useful tool in encouraging people to think about waste, environment, and the possibilities of local activism as part of a global issue. One of the challenges of the Sea Mills site is that the rampant grass effectively conceals the litter beneath. From a distance, or at a glance, this is a verdant liminal landscape. Closer inspection reveals the strata of objects beneath. So one idea that Jill and I have developed for the Power and the Water presence in Bristol’s Festival of Nature (FoN) is to retrieve some of the plastics from the Sea Mills riverbank, and make them visible to Bristolians. We will forage for these non-comestible, non-biodegradable objects, and present them to the public as artefacts of contemporary life, in which ocean currents and local actions both place plastics in the landscape. On our Harbourside stand (12-14 June), people will be able to handle the found items and reflect on what they might tell us about our relationship with land, water, and energy production and consumption. We have also been inspired by project PhD student Alex Portch’s interest in ‘future archaeology’.[4] These objects, already embedded in the riverbank, will form a historical record by which we may be judged in future. What will they say about us, our present time, past actions, and future hopes? Using the found plastics, members of the public may create narratives that express contemporary concerns, or simply tell a story about who we are and what we use in daily life.

Plastic art Longbardi

Pam Longobardi and her art on cover Sierra Magazine. Image: Pam Longobardi, with permission.

The visual remains an effective tool to communicate environmental change, and we are also engaging with artists, notably Eloise Govier to reinterpret found plastics and polystyrenes in creative ways. Eloise’s work will feature on our FoN stand. In this respect, we are connecting with a visual trope in the arts whereby found plastics are reappropriated as art objects and curated in order to stimulate reflection on personal and societal responsibilities, local and global environmental challenges, and natural and unnatural materials. Pam Longobardi’s recovered flotsam artwork Plastic Looks Back graced the cover of Sierra magazine in 2014.


SAS maritime tattoos to highlight the marine litter problem. Image courtesy of Surfers Against Sewage.

She believes that ‘a persuasive piece of eco-art can be an effective tool in the arsenal of social change’.[5] Alejandro Duran’s series of installations, ‘Washed Up: Transforming a Trashed Landscape’ addresses the presence of plastics in Sian Ka’an, Mexico’s largest federally protected reserve and UNESCO world heritage site and actively seeks to change our relationship with consumption and waste; while UK-based Surfers Against Sewage deployed the highly stylized imagery of maritime tattoos in their latest campaign to highlight the scale of the marine litter problem. As tattoos, they hope, the images convey a ‘sense of permanence, something that the marine litter crisis is threatening if action is not taken soon’.

Visual and material evidence are powerful communicators, and we are looking forward to observing how the different elements of our FoN presence – water samples, historical documents, works of art, and found objects – not only communicate project research to the public but also start conversations and build relationships which will shape our work – both how we research, and how we communicate it – in the months to come. We will also be developing ideas for community-based responses to marine (and other) waste, and welcome interest from groups or individuals who might want to collaborate with us. From Balinese beaches to British riverbanks, rubbish represents cycles of human production and consumption, borne on natural forces of currents, winds, gyres, and tides, and deposited at our feet. Do we walk on, or do we stop and pick up the trash?



[1] I use the term non-biodegradable cautiously, as recent research suggests that some plastics (polyethylene) may be broken down by gut bacteria in plastic-eating waxworms. Though this offers hope for future solutions for eradicating persistent plastic waste, at the present time plastic remains stubbornly present in our ecosystems, long after its production and use. See Yang et al, ‘Evidence of Polyethylene Biodegradation by Bacterial Strains from the Guts of Plastic-Eating Waxworms’, Environment Science Technology 48:23 (2014), 13776 – 13784

[2] ‘Bali eyes 4m foreign tourists’, Jakarta Post 15 Jan 2015

[3] Green School Bamboo News, ‘Governor of Bali signs MoU with BBPB Team’, 1 Dec 2014 <https://www.google.co.uk/search?client=safari&rls=en&q=green+school+plastics+campaign+bali&ie=UTF-8&oe=UTF-8&gfe_rd=cr&ei=gxdaVZj0L-3H8gfc_ICwDQ>

[4] see Laura Watts, ‘Future Archaeologies: Method and Story’ keynote given at Society of Museum Archaeologists Conference, Winchester 2009; and ‘OrkneyLab: An Archipelago Experiment in Futures’, in Ingold and Janowski (eds.), Imagining Landscapes (Ashgate 2012)

[5] Steve Hawk, ‘Spout: the Finer Side of Flotsam’, Sierra online, September 2014 < http://www.sierraclub.org/sierra/2014-5-september-october/spout/finer-side-flotsam>

Saints, Sailors and Seabirds in the Bristol Channel: The Past, Present and Potential Future of Flat Holm Island

By Alexander Portch

“This year came a great naval armament over hither south from the Lidwiccians… They went then west about, till they entered the mouth of the Severn; and plundered in North-Wales everywhere by the sea, where it then suited them… but the men of Hertford met them; and of Glocester, and of the nighest towns; and fought with them, and put them to flight… And they drove them into a park; and beset them there without, until they gave them hostages, that they would depart from the realm of King Edward. And the King had contrived that a guard should be set against them on the south side of Severnmouth… Nevertheless, they eluded them at night, by stealing up twice; at one time to the east of Watchet, and at another time at Porlock. There was great slaughter each time; so that few of them came away, except those only who swam out to the ships. Then sat they outward on an island, called the Flat-Holms…”

Extract from the The Anglo-Saxon Chronicle for the year AD 918 (source:britannia.com)


And so, like the Viking raiders of more than a millennium before, three Bristol-based members of The Power and the Water Project Team set forth from the English mainland, and thence across the expanse of the Bristol Channel in search of the sanctuary and isolation of the island of Flat Holm. Situated approximately five miles out to sea from Cardiff and Barry on the south-eastern coast of Wales, Flat Holm is one of two small islands located along a line between the pronounced headland of Brean Down, near Weston-super-Mare, and Lavernock Point, a short distance along the coast from Cardiff. With the discovery in 1988 of a Bronze Age Axe, dating to c. 900 – 700 BC, indicating the presence of humans on the island more than 2000 years ago; records of regular visits during the late 6th century by the Welsh saint Cadoc; and physical and documentary evidence for continuous occupation throughout the past 800 years; this small (approx.. 500m across) expanse of land in the midst of the Severn Sea is of great historic interest. Combined with its important geological features and rich natural heritage, recognised through its status as a SSSI, Local Nature Reserve, and Geological Conservation Review Site (GCR), the island is more than worthy of a visit by anyone with even a passing interest in the Severn Estuary, wildlife, history or archaeology.

Approach of Flat Holm

The islands of Flat Holm (in the foreground) and Steep Holm (beyond) line up as the cross-estuary ferry “Westward Ho” passes by to the north. Photo: Alexander Portch.

The fact, however, that it also lies along the line of the frequently postulated Cardiff-Weston route for a Severn Barrage, makes it especially significant for this writer. When viewed from afar Flat Holm, with its renowned population of Lesser Black-backed Gulls (Larus fuscus) (approx.. 4000 pairs), a stronghold of the Wild Leek, and historic value as the place where, in May 1897, Guglielmo Marconi first successfully transmitted a message across the open water using his wireless telegraphy system, would appear to be particularly vulnerable to the potential negative impacts associated with the erection nearby of a vast wall of rock, steel and concrete, complete with shipping locks and potentially even a road, railway and series of wind turbines. Despite the obvious presence of humans throughout much of the past 2500 years, demonstrated most tangibly by the remains of defensive fortifications dating to the mid-19th century, further military structures from the Second World war, the ruins of a farmhouse, and a lighthouse; the island still seems, even upon close inspection, like a wild and windswept place, where humans are an invasive species – disturbers of the peace enjoyed by the gulls, rabbits, lizards and sheep. From such a perspective, opposition to a barrage could be seen as wholly understandable and indeed a worthy cause.

Light house

Flat Holm lighthouse, located at the southern end of the island. The light is now fully automated and has been powered by solar panels since 1997. Photo: Alexander Portch.

It was, perhaps, with such views in mind that on Wednesday April 16th 2014 project members Peter Coates, Jill Payne Payne and I arrived on “Coal Beach,” at the north-eastern end of the island having traversed the full width of the Channel between Weston-Super-Mare and Cardiff aboard the bow-loading, Island Class Passenger Vessel “Westward Ho”; a rather small yet accommodating ferry which operates between Cardiff, Weston and Flat Holm throughout much of the Spring and Summer months (http://mwmarine.org/index.php/notable-vessels). This included a brief stop-over in Cardiff Bay; an area of water impounded behind a fixed barrier which, since its construction in 1999, has completely transformed the industrial maritime landscape of disused dockside facilities and intertidal mudflats into the social, cultural and recreational hub of modern Cardiff, replete with an opera house, shopping centre and the iconic copper-plated structure of the Senedd, which houses the National Assembly of Wales (see http://cardiffbay.co.uk/index.php/history). When first postulated the Cardiff Bay Barrage, much like its bigger estuarine cousin, met with fierce objection, including from those who feared the loss of important wetland habitats for birds, flora and other coastal wildlife. In many respects their concerns were well-founded, as such resources have indeed been lost; however, it is difficult to overlook the vibrant atmosphere of the area today, nor the smart-looking yachts and well-tended blocks of flats; their balconies overlooking the comings and goings of vessels navigating their way through the three locks which connect the Bay with the wider tidal estuary. For me at least, the experience of being conveyed through a large shipping lock was a first, and one which proved to be an unexpected, yet most welcome, highlight of the expedition. Whilst the locks that would be incorporated into a Cardiff-Weston barrage would be significantly larger, it was still possible to gain a sense of what entering the Severn Estuary Lake from the tidal Bristol Channel might be like for incoming container ships if a Severn Barrage were ever to be built.

Bristol Locks

Peter Coates watches with interest as one of the three locks connecting the freshwater lagoon of Cardiff Bay with the tidal waters of the Bristol Channel begins to fill with water. Photo: Alexander Portch.

Much as the tide is the key factor motivating the proposals for building a barrage, it is also a conspicuous force influencing the ways in which people, both now and in the past, interact with the island of Flat Holm. Arrival and departure times are wholly subject to the operation of the tides, with boats arriving on the pebble-strewn beaches at high tide, disembarking their cargoes of goods and passengers, then either leaving straight away on the falling tide or, as in the case of our own mode of transport, being left high and dry for up to six hours until the water level once again reaches a height sufficient to float the vessel free. It was perhaps such a characteristic of the two “holms” (a Scandinavian term for a river island) that attracted religious communities during the middle centuries of the 1st millennium AD. On the nearby Steep Holm the ruins of a medieval chapel attest to their presence, whilst on Flat Holm little physical evidence remains for the existence of such a community, with the exception of a cross-inscribed slab found incorporated into the base of the garden wall of the island’s farmhouse. Medieval burials and a curving enclosure ditch, excavated in 1979, may also hint at the whereabouts of some of the island’s earliest structures. With access to the island being governed by the movement of the Channel’s waters and facilitating landings only with great skill and much danger, particularly during inclement weather, the early Christian inhabitants must have found it the ideal place to pray, meditate and practice their distinctive eremitic lifestyle. The workings of the tide may also have played a key role in the island’s infamous history as a haunt for smugglers throughout much of the 17th and 18th centuries. In full view of the local authorities in Cardiff, smugglers were known to convey goods to caves in the cliffs on the eastern side of the island in broad daylight, with little apparent concern about the risk of being caught. Such activity was greatly aided by the fact that the authorities lacked a suitable vessel with which to pursue the smugglers; however, even if such a craft had been within their means, their passage out from the mainland would still have been dependent on the timing of the flood and subsequent ebb tides, with any delay providing the perfect opportunity for those engaged in illicit activities to slip away to safety.

Beached Ferry on Flat Holm

The bow-loading Island Class Passenger Vessel “Westward Ho” sitting high and dry as it awaits the incoming tide to free it from its berth on the pebbly shores of Flat Holm Island. From this point it took little more than 15 – 20 minutes before it was ready to depart – a clear demonstration of the speed with which the tide ebbs and flows around the coastline of the Bristol Channel and Severn Estuary. Photo: Alexander Portch.

It is apparent, therefore, that for as long as humans have interacted with the islands of the Bristol Channel they have, in so doing, interacted with non-human nature. Through knowledge of the tidal cycle people have gained access to Flat Holm, and through exploitation of its mineral resources and agricultural potential they have derived wealth and sustenance. In many respects Flat Holm is an excellent example of how closely human activity can be integrated with the functioning of the “natural” world, as the characteristics that presently justify the island’s status as a SSSI, almost without exception, are the product of anthropogenic influence. The Wild Leeks, for example, are believed to have originally been brought over by the monks who cultivated them on neighbouring Steep Holm, whilst the rabbits were intentionally introduced in the 12th Century. The present plant communities that dominate much of the island’s open landscape, including various grasses, nettles and ground ivy are most likely the result of the rich soils that have built up in response to years of pastoral activity, including manuring by cows, sheep and goats. The Wild Peony was also introduced from Steep Holm, although at a later date, during the Second World War; whilst the thousands of Lesser Black-backed Gulls that call the island their home, and in turn create such a feeling of wildness despite the obvious human presence, only arrived during the 1950s as a result of the abandonment of the military facilities by the 350 soldiers who had been stationed there.

This close ties between human and natural history of the island was further propounded, much to the shock of the project team members, upon conversing with the knowledgeable and welcoming wardens and volunteers of the Flat Holm Project, who have managed and operated the island since 1982 (http://www.flatholmisland.com/). It was initially felt that somehow the gulls of Flat Holm gave the appearance of being somewhat healthier and more “natural” in such a wild and rural setting than their comparatively unkempt urban relatives in towns and cities like Bristol. To be informed, therefore, that the principal food supply for the Flat Holm population comprises the nearby Cardiff City landfill came as quite a surprise. It was also explained that the numerous small bones found scattered across the island were not in fact the remains of predated rabbits, but were predominantly chicken bones; the leftovers from the seagull equivalent of a trip to the local Chinese takeaway. Similarly, pieces of plastic, fragments of children’s toys and plastic balls were also found to represent the colourful trinkets picked up by the birds in their enthusiasm as they scour the dump in search of a chicken drumstick or juicy spare rib. As such, the great majority of litter scattered about the island isn’t the direct result of human carelessness, but is the work of supposedly wild creatures exploiting the products of our own throwaway culture. The fault could thus still be perceived as ours; if perhaps an unexpected and unintentional consequence of our actions. It is also clear, however, that the remarkable number of Black-backed Gulls on Flat Holm are almost wholly reliant on the waste products of human society for their survival and it is believed that their initial arrival and subsequent explosion in numbers could be directly attributable to such a rich and easy source of sustenance. The current population is in fact almost half that which existed earlier in the 20th century, a product of a careful programme of management intended to conserve a maritime grassland habitat across the northern end of the island: yet another example of human involvement in the development and proliferation of nature on this small outcrop of limestone cast adrift in the middle of the Severn Sea.

Lesser Black-backed Gulls

Lesser Black-backed Gulls (Larus fuscus) perched on the cliffs at the southern end of Flat Holm. With approximately 4000 pairs, it is very much their island! Photo: Alexander Portch.

If humans have been so pivotal in the development of wildness on Flat Holm, therefore, could it not be argued that further human involvement in the region, even in the form of a barrage, is a continuation of that activity? A central concept in the discipline of environmental history is the idea that throughout much of their existence humans have exerted a profound influence upon non-human nature and, in turn, non-human nature has been a key factor in shaping human history. Indeed for many scholars, humans and nature are indivisible: humans are a part of nature and thus their activities are wholly natural. It is almost certain that a barrage would lead to significant change on Flat Holm, and could result in the loss of many of the species and habitats for which it is presently renowned. But filling the void left by their demise would be a host of new plants and animals that would greatly benefit from the altered tidal regime, the modified air currents (particularly if wind turbines were also constructed) and the varying levels of pollution, both during and after construction Nonetheless, even if the natural world is seen to benefit, there is no escaping the fact that the visual aesthetics of the estuarine landscape, and the feeling of remoteness which so vividly evokes the isolation that must have been appreciated by the early Christian inhabitants, will be irrevocably transformed and perhaps even lost entirely.

Farewell to Flat Holm

Farewell to Flat Holm. Silhouetted against the clear blue sky can be seen a wind turbine, and the foghorn which remained in operation until 1988. In addition to wind power, the island benefits from solar panel arrays and a biomass boiler. Alongside a large Victorian aquifer for storing collected rainwater, it can boast a remarkably high level of self-sufficiency. Photo: Alexander Portch.

Nonetheless, as the ferry departed Flat Holm, Ynys Echni in Welsh, leaving behind the ghosts of Bronze Age explorers, early Medieval monks, Viking raiders and the scores of mariners shipwrecked around its treacherous shores, it wasn’t the inter-connectedness of humans and their environment, or the comparative benefits of barrages and tidal stream turbines that were foremost in my thoughts. Instead, as the first time I had viewed what had always seemed a familiar land/seascape from such a different perspective, I could do little but gaze upon the holms in wonderment at their beauty as they faded in the half light of the setting sun.