A medieval weir. Part 2

November 19, 2011 Leave a comment

Part 1 of this article described an ‘underwater cropmark’ – a band of riverbed vegetation 3m wide and 40m long crossing the River Great Ouse in Bedford in a diagonal direction relative to the current, visible on aerial photos. This was identified as indicating the former position of a medieval weir. But could the construction of the weir actually date to the late Anglo-Saxon period?

Weirs as defensive features
The word “weir” has its roots in the Old English werian, meaning to defend (as in “beware” or “to be wary”). As well as providing the head of water to drive mills, weirs could be used to obstruct and help control traffic along rivers. For this reason towns on rivers may once have incorporated weirs into their systems of defence: after all, it makes little sense to surround a town with earthen ramparts and deep ditches if river approaches were left open.

An associated role of weirs may have been to create the head of water to direct flow through defensive earthworks. This is an important but neglected area of study. Urban defences are usually discussed in terms of their solid materials – the walls or earthen ramparts which presented physical barriers to attack. Water flowing through ditches outside of those ramparts receives little attention. In the rest of this article, I will argue that a large linear earthwork in southern Bedford, commonly supposed to be of late Anglo-Saxon construction, could only have functioned if there was an associated weir across the river.

The King’s Ditch
When Edward the Elder fortified the southern part of Bedford in AD914, effectively turning the town into a “double-burh”, the terrain was so flat on that side that the river was the obvious source of water to use. The Anglo-Saxon Chronicle records that King Edward’s army stayed in the town for four weeks in order to build the defensive earthworks. A kilometre-long semicircular earthwork known as King’s Ditch was constructed. This survives today in places as a broad ditch alongside a sizeable inner bank, covered in dense undergrowth. Other stretches have been levelled and built over, so that it runs through culverts beneath roads, offices and schools.

A former system of flow, with Reynolds map of 1849 used as base plan (Bedfordshire and Luton Archives and Records Service). Click on picture to enlarge

The most interesting feature about the King’s Ditch is that it flows. This is no stagnant ditch. Nor does it have a languid current like the Great Ouse from which its water is derived. Its flow is fairly fast and strong. And this is not just a modern phenomenon, brought about through recent re-engineering of the watercourse. Evidence that there was always a good flow of water in the King’s Ditch throughout medieval and post-medieval times is provided by the existence of fishponds just inside the ditch on its south-eastern side. These fishponds originally belonged to St John’s Hospital, a medieval religious institution. Maps show that there were channels bringing water in and out of the fishponds, which presupposes a strong flow in the ditch itself. Although later in date than the King’s Ditch itself, the fishponds tapped into and made use of an already existing flow of water.

Detail showing flow through medieval fishponds connected to the King’s Ditch

By rights the water should be stagnant, or should back up into the river the way it came, given the flat terrain of southern Bedford. The fact that it flows suggests that this was an important element of the initial design. The monument was built with a constant gradient and a contrived fall of water of about 2m between inlet and outlet – much greater than the natural fall of the river between those two points, with gravity enlisted as the principal force impelling water to flow through the ditch.

The significance of flow
Why would the builders of the earthwork go to the trouble of making it flow? Consider for a moment why a town boundary ditch full of stagnant water would not work. Imagine how quickly such a ditch would start to silt up, fill with rubbish, get polluted and clog with vegetation. Carrying out periodic maintenance would be difficult. Thick slimy mud thrown up from the ditch would slip down into the water again, and the earthwork bank alongside would soon fall into disrepair. Above all, the water – since it has no momentum or energy – cannot be exploited for industrial purposes. Without flow, it cannot be moved around or managed in any way at all.

The King’s Ditch and rampart as it was 100 years ago, and a similar stretch today. Despite recent silting up and vegetation growth, the ditch still has a flow of water running through it

Now consider the many benefits of a flowing ditch. The water itself does some of the work of maintenance, carrying away smaller particles of silt and leaving the gravel behind, making the ditch easier to clean out. It is self-scouring. The ditch takes away rubbish and pollutants, acts as a sewer and a drain, while replenishing itself with fresh water. It also serves as a flood defence. Unclogged by vegetation and mud, the stream can be used for bathing and washing of clothes, or for transport of goods by boat, with direct access to and from the river. Flowing water is a vibrant material which can be controlled and moved around as required. It can be diverted through sluices into side channels – to fill further water features or flush them out, to cool forges, to serve potteries and perform innumerable other industrial functions. And that is not to mention the symbolic significance of encircling towns with flowing water.

Liquid flow – a force driven by gravity yet intensively modified, shaped and utilised. This picture was taken at the existing 19th century weir on the river between inlet and outlet of the King’s Ditch. Although the position of the weir has been changed, the King’s Ditch still relies on a river weir to provide the necessary fall of water to ensure flow.

How, then, was the artificially contrived fall and the flow of water through the ditch accomplished? There was one obvious way to do it, and that was to construct a substantial weir across the river somewhere between inlet and outlet of the King’s Ditch. Its purpose was to create the necessary artificial step in water levels. Such a weir on the river is actually a logical necessity for the King’s Ditch to function as a flowing earthwork, and its former existence might be deduced even if there were no material trace surviving of the structure itself. The technology of stepping the river through the building of weirs, in order to create a head of water to drive mills, was already well established. It made sense to apply the same principals to ditches of defensive earthworks too, especially if a large workforce was available to carry out the work.

Thus the weir across the river revealed by the ‘underwater cropmark’ could have been built as an integral and functioning part of the King’s Ditch, even though it appears to be physically separate from it. Flow as a material force is normally largely absent from archaeological explanations, leading to a somewhat static and fragmented view of landscapes and townscapes. Only when we take relationships of flow into account can the dynamic interconnections between otherwise disparate sites and monuments be perceived.

A modified version of this article was published as ‘The weir and flowing earthworks of Bedford’ in British Archaeology, Nov-Dec 2011, 22-7, and featured on Radio 4’s ‘Making History’ programme on 25/10/2011.


Language flows

November 13, 2011 Leave a comment

Rivers are good to think with. They are useful not only as metaphors, but also as exemplars of flow. Theories about a wide variety of past phenomena can to some extent be modelled on the physical characteristics of river forms and flowing materials.

Actually, we already use rivers in our thinking, perhaps more than we realise. Take historical linguistics as an example. A central assumption of the discipline has long been the idea that groups of languages have ‘sources’ – or ancestral languages from which more recent and contemporary languages are descended . As Renfrew explains, it is argued that

“there were a number of related languages (Greek, Latin, Sanskrit) and sub-families (Celtic, Germanic) which must be ‘sprung from some common source’, thereby implying both the notion of an earlier proto-language (such as Proto-Indo-European) and an original homeland. Such concepts are now basic to the discipline of historical linguistics” (Renfrew 2000, 10).

The point is that if you map the relationships between developing languages according to such ideas, the result is something very much like part of a river system. Diverging paths of flow are envisaged to run in a branching pattern that resembles configurations of river channels on deltas and alluvial fans, sometimes called distributary networks.

On this model, similarities between disparate languages can be explained in terms of deriving from a hypothetical proto-language, in the same way as different branches of a river (especially in its lower reaches) may have diverged from a single course further upstream. It is tempting to link such divergences of language flows with movements of peoples and the cultural diffusion of ideas and techniques, such as the spread of farming across Neolithic Europe from the Fertile Crescent area – and the reader is referred to Colin Renfrew’s critical discussions on these matters (Renfrew 1987, 2000).

But as Renfrew points out, such diverging models do not seem nearly so applicable to deeper prehistory. Before the advent of farming and village settlement, groups of hunter-gatherers were small and geographically remote from each other. It is hard to imagine such scattered groups speaking a common language: on the contrary, on the model of divergence outlined above it seems likely that there was a multiplicity of different languages. Only with the coalescence of people into larger communities during the Neolithic would these languages have come together. Not so much a divergence, then, but rather a convergence of disparate languages. Instead of an ever increasing number of languages, the number of different languages would decrease as they merged into ever larger flows. This idea can be expressed very simply by comparing it to those parts of river systems where smaller streams or tributaries feed into larger ones in converging branching structures called tributary networks.

At first sight the diverging and converging models might seem to be diametrically opposed to each other, and indeed the two forms of explanation have clashed in the context of historical linguistics debate. Speaking of recent developments in the discipline, Renfrew notes the increasing prominence given to convergence models and the tension between these and more established divergence models (Renfrew 2000, 13).

Rivers are useful here in showing us how apparently contradictory models of divergence and convergence can be integrated together. River systems display the characteristics of both distributary and tributary branching networks. The type of network which prevails on any given stretch of river depends on local geomorphological conditions and the ‘stage’ of the river on its journey to the sea. Thus many rivers configure themselves in a primarily tributary pattern in their upper and middle reaches. This changes to a distributary pattern in lower reaches where rivers drop much of their sediment load, and break up into numerous channels to flow around it into the sea.

It could be argued that language flow works something like this too, adopting the overall form of a tributary network or distributary network at different times according to circumstance. As in the case of rivers, both forms of network may co-exist, with neither being mutually exclusive of the other. But so far we have been thinking of distributary (diverging) and tributary (converging) networks manifesting at different times in the flow of a language through time. Now I want to turn to another sense in which diverging and converging branching networks can manifest simultaneously. Rivers can show us how.

We tend to understand rivers mainly in terms of natural processes. But as I argue in my new book, Fluid Pasts (Edgeworth 2011) they are actually complex entanglements of natural and cultural forces, and need to be re-mapped accordingly. In their middle reaches there is not just the classic tributary pattern of river channels to take into account. There is also the host of partly artificial distributary channels designed to take flow from the river to serve a whole variety of functions – head-races of mills, town boundary ditches, inlets to industrial cooling plants, irrigation ditches, drainage cuts, navigation channels etc – many of which split up into smaller channels before being returned to the river further downstream, often in the form of drains. The crucial point here is that these distributary channels are important parts of river systems, fully integrated into the tributary network, even if usually left out of maps of rivers. Any meaningful discussion about flow regime has to take these into account.

The sketch shows the middle reaches of a typical tributary river network with distributary network added. Actually, the two networks are really just a single network, in the context of which most stretches of river are at once tributary and distributary streams. Most rivers in their middle reaches actually look much more like this than they do the classic tributary pattern so often illustrated in geography textbooks.

Rivers thus provide us with useful working models for understanding how diverging and converging flows can operate simultaneously in the same places and the same times and as part of the same processes. Can this help our understanding of the development of language through time? I believe it can. Thinking of language flow along the lines suggested by rivers, it is not contradictory to hold that languages converge and diverge at the same time. Models that emphasise divergence of related languages from a common source or proto-language can be quite compatible with models that emphasise convergence.

Not just a metaphor

Comparing language and rivers may seem counter-intuitive at first, but actually it makes a lot of sense. It is not just a metaphor. Rivers and languages are very similar (in the sense of being forms of flow) and more closely entwined in a material sense than is usually acknowledged. Because rivers afforded both avenues of movement and obstacles to movement for people, many languages effectively travelled along, were grouped around or divided by rivers. Evolving river systems over the last few thousand years have been inextricably entangled with evolving languages. Take a look at this map of the Amazon and Orinoco river basins showing principal indigenous language families of the region. Although the map gives a greatly simplified picture, one can see how the branching network of languages comes to take on roughly the same shape as the actual river basin, with language flows and river flows woven together, unfolding on shared tangled trajectories. But that’s another story…


Edgeworth, M. 2011. Fluid pasts: archaeology of flow. London, Bloomsbury Academic.

Renfrew, C. 1987. Archaeology and language: the puzzle of Indo-European origins. London, Pimlico.

Renfrew, C, 2000. ‘At the edge of knowability: towards a prehistory of languages’ Cambridge Archaeological Journal 10 (1), 7-34.

A medieval weir. Part 1

November 11, 2011 2 comments

river scene

When people in medieval times looked at urban rivers, like the River Great Ouse in Bedford, they saw something quite different from what we see today. Not so much a picturesque scene with pleasant walks along embankment promenades, past riverside gardens and ornamental bridges. That was a creation of the Victorian and Edwardian eras. No, what they perceived was more basic, more elemental. The river was seen and experienced, amongst other things, as a great flow of energy moving slowly and inexorably through the town.

It was a flow of energy, moreover, that could be harnessed and put to use. From middle-late Saxon times on, in many river towns throughout Britain, mills were built next to the river – larger than those on small streams out in the country. Artificial watercourses were cut to serve as headraces and tailraces, taking the flow of water from the river and back into it again. In some cases, massive stone weirs were placed across the river to create the head of water to power the mills. These were such important features – so vital to the urban economy – that towns like Warwick, Ware and Wareham were actually named after their weirs.

Surprisingly few people today know in which direction their local river flows. Which way is upstream and which downstream? This knowledge, once so crucial, no longer has much significance for town inhabitants. Other flows – such as those of electricity, gas and oil – now provide most of the energy that the town needs. But that does not mean that we should forget how important the flow of water was to people in the past. The river environment is full of clues as to how people once interacted with the energy of flowing water – how they channelled, shaped and diverted it for their own purposes and projects.

Computer screenshot of aerial photo taken when the river was low and clear in July 2006 (©Google 2010, ©Tel Atlas 2011 and ©Getmapping plc 2011) with detail of the relevant part of the image. Direction of flow is from left to right. Ignore the modern path that coincidentally almost aligns with the feature: this was built a few years ago and is unrelated

Take Bedford for example. A huge archaeological feature has come to light. The feature takes the form of a linear band of riverbed vegetation crossing the River Great Ouse diagonally from the north bank to a small island on the south side. The ‘underwater cropmark’ is 40m long and 3m wide, visible on Google Earth (on a 2006 aerial photo accessible through the ‘historical imagery’ function) from 1km up.
Normally the feature is not visible from the ground, with the water being too high and too murky. But this year the exceptionally dry Spring lowered the river, and short rainbursts in June significantly improved visibility. For a period of about a month, and for the first time in my lifetime, the feature was clearly visible from the river bank.

View from the north bank, looking south-east, June 2011. The feature appears as a broad band of underwater plants running across the middle of the picture

View looking straight down from a boat immediately above the underwater feature. The river weeds in question are known by anglers as cabbage lilies or lily pads – more formally as the submerged leaves of Nuphar lutea (Yellow Water-lily).

This is not the first time that the feature has been noted, however. It was described and mapped by local historians in the early 20th and late 19th century, and variously identified as a former causeway, barrage, weir or dam. In 1926 Farrar stated that “when the water is clear it is possible to trace a broad band of weeds at the bottom of the river, marking the course of the barrage which crossed the river obliquely in a south-westerly direction to the small island…”

Map of the underwater feature drawn in 1906, when it was visible as a broad band of weeds (Goddard 1906).

An earlier map by Hurst in 1859 shows it as the foundation of a submerged stone wall (Hurst 1859). Direction of flow is from left to right.

The earliest reference to the feature is by a former mayor of Bedford called George Hurst (see map above). He wrote in 1859 that part of the foundation of a stone wall, ten feet wide, could be seen crossing the river at low water. He mapped its position for us, and said the wall was the remains of a stone barrage in existence up to 1774, when it was demolished and the stone re-used for building works. The submerged wall or barrage had previously been utilised for mooring barges, though its original purpose was probably forgotten even at that time.

It seems, then, that the broad band of weeds visible today marks the course of a former large stone feature which crossed the river to the small island, already submerged when it was removed in the late 18th century as part of river navigation works. Quite why lily-pads should find such favourable rooting conditions along the line of the former stone feature is not fully understood. But it is well known that growth of vegetation on dry land can be influenced by archaeological features: the same must surely be true underwater. The question remains as to what the original function of the river wall was. The idea that it was once a weir (submerged by later embanking and deepening of the river) is supported by its diagonal orientation relative to the current, reminiscent of many other weirs both ancient and modern.

Part Two of this post will investigate the relationship between the weir and a kilometre-long late Saxon boundary ditch around the southern part of Bedford. Although the two features are not contiguous, the relation between them can be explored, it will be argued, through patterns of flow…..

Mark Twain: insights on changing river morphology

November 4, 2011 Leave a comment

St Louis
Steamboats on the Mississippi. Janicke & Co. "Our City, (St. Louis, Mo.)." 1859. Prints and Photographs Division, Library of Congress


Mark Twain (1835-1910) can tell us more than almost anyone else about the Mississippi. He not only wrote about life on the river, in his novels Huckleberry Finn and Tom Sawyer; his own life and identity were river-immersed and river-entangled. As a young man in the 1850s he worked on the Mississippi steamboats and became a master river boat pilot. Even his pen name derived from the call of the leadsman at the front of the boat, who tested the changing depth of the river with a knotted or marked line, providing the pilot with a stream of information on which to base decisions from moment to moment. ‘Mark Twain!’ refers to the two-fathom mark on the line, indicating that the depth had reached 12 feet, usually a sign that it was safe for the shallow draft steamboat to proceed.

Twain’s testimony – Samuel Clemens was his real name – is relevant here because he gained first-hand experience of engaging with the dynamic Mississippi River at a crucial time in its history. His descriptions in Life on the Mississippi illuminate key themes of this book, including the entanglement of nature and culture in practice. Although the specific geomorphological conditions of the Mississippi at that time are different from those of any other river (even from the same river today), his observations can shed light on the interpretation of archaeological sites elsewhere, on which the material traces of dynamic inter-relationships between people and rivers are encountered.

Up to the nineteenth century, the strong current of the Mississippi prevented most boats from going upstream. Traffic was largely one-way, with barges or rafts coming downstream with the flow from the upper river to New Orleans. Twain himself describes watching, as a young boy sitting on the levees, rafts the size of football fields stacked with acacia boards, with encampments of makeshift huts on them, being manoeuvred down the river by crews of twenty men or more (the deforestation that was taking place upstream would itself have changed the flow of the river, and the load of sediment it carried, through the soil erosion and increased run-off it caused). Barges had to be laboriously poled by hand all the way back upriver around each and every one of the meandering bends. That all changed with the invention of the steamboat, which had enough power to go against the flow. The whole economy of the river changed as a result.

To Twain the river was the most ‘eluding and ungraspable object’. He describes just how difficult it was, while learning to be a steamboat pilot, to memorise the shape of the river:

 I would fasten my eyes upon a sharp, wooded point that projected far into the river some miles ahead of me, and go to laboriously photographing its shape upon my brain; and just as I was beginning to succeed to my satisfaction, we would draw up toward it and the exasperating thing would begin to melt away and fold back into the bank! Nothing ever had the same shape when I was coming downstream that it had borne when I went up (Twain 1883: ch. 8).

Twain was far from being a mere spectator here. As riverboat pilot he was actively engaged in navigating round snags and treacherous eddies, seeking deep water and fast currents, looking out always for sandbars and other shallows that could beach the boat. His standpoint was a mobile one. Not only was Twain’s point of view always on the move, but so too was the topography of the river,

whose alluvial banks cave and change constantly, whose snags are always hunting up new quarters, whose sand-bars are never at rest, whose channels are forever dodging and shirking (Twain 1883: ch. 10).

One aspect of these river shifts, he noted, was the way the loops of the river meanders got progressively larger, so that:

 in some places if you were to get ashore at one extremity of the horseshoe and walk across the neck, half or three quarters of a mile, you could sit down and rest a couple of hours while your steamer was coming around the long elbow, at a speed of ten miles an hour, to take you aboard again (Twain, 1883: ch. 17).

He further noted how the river would make cut-off channels or chutes across the neck, diverting flow away from the horseshoe bend. Significantly, the process could be speeded up:

When the river is rising fast, some scoundrel … has only to watch his chance, cut a little gutter across the narrow neck of land some dark night, and turn the water into it, and in a wonderfully short time a miracle has happened: to wit, the whole Mississippi has taken possession of that little ditch (Twain 1883: ch. 17).

This placed the plantation of the ‘scoundrel’, whose land was formerly situated in the back of beyond, onto the new river bank – multiplying its value. The old watercourse rapidly shoaled up, becoming impassable to steamboats. Formerly valuable plantations, once but no longer on the economic lifeline of the river, now dramatically lost their value. For this reason,

Watches are kept on those narrow necks, at needful times, and if a man happens to be caught cutting a ditch across them, the chances are all against his ever having another opportunity to cut a ditch (Twain 1883: ch. 17).

In other words, material investment in land along the present course of the river meant that, though some tried to change its course for profit, there were others who would go to considerable lengths to keep it where it was. There was a lot at stake in these battles to retain or change the course, not least for the riverboats, whose journey times could be greatly shortened. An important consideration here too is that the river served as state boundary as well as navigation channel. The cutting-off of a river meander could result in a town in the State of Mississippi suddenly finding itself in the State of Louisiana, or vice versa. Other strange inversions of landscape topology could occur:

The town of Delta used to be three miles below Vicksburg: a recent cut-off has radically changed the position, and Delta is now two miles above Vicksburg (Twain 1883: ch. 1, his italics).

Thus Twain hints at political and economic dimensions to changing river morphology, and human complicity in it, while at the same giving a wonderful phenomenological account of the dynamic state of the river as it was then. He was there. He was caught up in it all. He was in direct contact with the river (through the steamboat and the leadsman’s line). At the same time he portrays the Mississippi as more than just a river – as a dynamic assemblage of forces and flows and materials and artefacts all interacting with each other. One of the flows is the traffic in both directions of steamboats themselves, together with the passengers and the cargo they carry. Cut-offs or chutes can be the work of rivers, or people, or an entangled mixture of both. Not only are nature and culture intertwined, but so too are materials and ideas. Economic motives of greed and profit work both with and against the flow of the river.

The Civil War brought an end to the steamboat era. Years later Twain returned to see a very different Mississippi, its flow more controlled, its length shortened, its meanders curtailed, its levees further extended and built up on either side. Yet  he retained something of the former wildness of the river in his character (for rivers shape people as well as the other way round). To him, a river pilot in the heyday of steamboats was ‘the only unfettered and entirely independent human being that lived in the earth’ (ch. 14). Later in his career, something of that came through in his writing.


Twain, M. (1883) Life on the Mississippi (Boston: James R. Osgood).


The text above is an extract from the new book Fluid Pasts: Archaeology of Flow by Matt Edgeworth , published by Bristol Classical Press, part of Bloomsbury Academic (September 2011) and available from Amazon.com and Amazon.co.uk.

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