How Bristol's rivers shaped the city + vice versa: a brief summary of the last half a million years


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It’s not an especially insightful thought to point out that the vast majority of major cities lie on some body of water - the sea, perhaps a major lake, or river. So many cities are defined by their river - visually, geographically, culturally. Cities are born and grow where rivers are bridged. Their bridges become metonymic icons of their cities. Neighbourhoods and people get judged as being from the right or wrong side of the river.

Bristol, at first glance, seems to fit the same pattern easily enough. If you’ve seen one stock image of Bristol in your life, it’s probably been a lot like this one. There’s your iconic bridge. And there’s your river. It’s the River Avon.

As any amateur etymologist can tell you, “Avon” is a cognate of the Welsh word afon "river", both being derived from the Common Brittonic for river. Therefore, River Avon means River River, which also explains why there are at least 10 Avons in Britain. When disambiguation is necessary, this one gets called the Bristol Avon.

So you might think there’s no story here. Bristol sits on a river, like so many other cities. It was born from a bridge, like so many other cities - its very name derives from Brycg stowe, the place at the bridge. The river variously served both as a defensive barrier, and an avenue for transport and trade. Like every other river city. Boring.

Except…. Firstly, look at a modern map of central Bristol and you don’t see it bisected by a river, you see it sliced up by two rivers. Do a little research and you’ll encounter many more. Yet, perversely, as someone living here, I don’t really feel like Bristol has a river at all.

Don’t worry, I’m not denying the self-evident cartographical or hydrological reality. Clearly, Bristol has at least one channel by which water travels downhill towards the sea. However, in my mind, rivers are supposed to flow, and this stretch of ‘river’ does not. Rivers this close to the sea are supposed to be tidal, and sure enough, the Avon has a huge range - except, half a mile east of here, in the city centre, this water level never changes. There is a reason locals talk about going for a walk along the harbour, not along the river. It may be long and thin and river-shaped on a map, but it simply doesn’t act or feel like a river.

On the other hand, the southern watercourse on our map ticks off both visible current and tidal variation criteria. Yet it too fails to feel like a river, because it runs unnaturally straight, and has clearly engineered banks, and ten seconds of wikipedia research will confirm it is man-made - making it quite plainly a canal, in my eyes.

So, it feels to me that the Avon flows into eastern suburban Bristol as a river, and flows out to the west as a river, but within the city centre, exists not as a river but as a harbour and a canal.

In my previous video I briefly summarised the early 19th century creation of the floating harbour and associated canals, and implied I would do a future video on the topic. This is not that video. Because before I could even start making that video, I had one seemingly simple request: a map of how the river looked before the Floating Harbour was built, which I could directly compare to today’s map, flipping back and forth.

This simple task turned out to be basically impossible, because the oldest Ordnance Survey maps I could find were all post-Floating Harbour, and the maps older than that all tended to look like this: north isn’t up, the scale isn’t certain, the perspective isn’t top down, far too small an area is depicted, and the whole thing is basically an artist’s impression rather than a surveyed representation.

Flipping back and forth between these two is pretty useless, and the problem would only get worse if I tried to find maps for every intermediate stage of development. It soon became clear I would simply have to draw my own maps, which is a small problem as I am neither a cartographer nor graphic designer, equally lacking in GIS tools and artistic flair.

Nevertheless, I’ve managed to cobble together a series of maps which served my purpose. Since I hate videos that make you sit through endless waffle before getting to the point, let’s go right ahead and show that A-B comparison. Bristol now. Bristol before people starting messing with the rivers. Now. Before.

So, if that’s sufficient to sate your curiosity, feel free to stop watching. As for me, I went far enough down this rabbit hole in researching my maps to realise that before telling the 19th century history of the Floating Harbour, I needed a “part zero” chronicling the overall story of how the rivers shaped the city of Bristol, before the City of Bristol began shaping its rivers in turn.

Interested? Let us begin by casually rewinding about 450,000 years.

Given that this is well before anatomically modern humans appeared anywhere on earth, let alone in the Bristol area, you might think this is overshooting a bit. However, our iconic Clifton Suspension Bridge shot earlier requires a bit of explanation. See, 90m deep gorges make for very nice photographs, but it’s hard to understand why the river would have bothered to form it in the first place. Standing here today we can see the river, having approached from the east, turn roughly 90 degrees north before carving this dramatic gorge through this limestone ridge of higher ground.

But if we simply pan to the south west, we can see that ridge fall away, and lower ground here. Why doesn’t the river take this seemingly much easier path to the sea? Being so long ago, we don’t really know, but the leading theory seems to be that during the Anglian ice age, this route was blocked by glacial ice. Forcing the river to take the northerly turn and carve the gorge we see today.

The influence on today’s Bristol is fairly obvious - this is where Bristol stops.

The gorge presented a hurdle that Bristol never leapt, but had the river not swung this way, nothing would have stopped Bristolian suburbs like Clifton spreading west over what is now Leigh Woods and rural Somerset. That is, of course, assuming Bristol even came to exist in the same location at all - in a parallel universe where the river headed on south-west, perhaps a totally different location would have been more attractive.

Indeed, if we fast forward to the human era, we find the Avon gorge decidedly influential in dictating the choice of settlement location. In the Iron Age, somewhere around the 3rd or 2nd centuries BC, we see three hill forts developed on highly defensible positions around the Avon gorge. Clifton Down Camp, Stokeleigh Camp and Burgh Walls Camp. Stokeleigh Camp survives in reasonably visible form today, and I’ll probably do another video on it at some point.

For now though, let’s move on to the Roman period. The biggest Roman city in this part of the country was Bath, lying about 11 miles upstream on the Avon. In the specific area shown on this map, their main settlement was Portus Abona, the name being a Latinised Avon, acting as a satellite port for Bath. This was at the mouth of one of the Avon’s tributaries, the River Trym, in a suburb today known as Sea Mills.

There is also archaeological evidence of Romano-British villas and so forth in the Bedminster and Bedminster Down areas, which are situated on another tributary called the River Malago. Needless to say, the choice of location by this river was no coincidence. It was used to power tide mills, creating a mill pond roughly at the location of today’s Bathurst basin, and this pond was reportedly used for baptisms; the Brittonic ‘beydd’ for baptism perhaps being the basis for the name ‘Bedminster’.

Interestingly, though, there’s no evidence of Iron Age or Roman occupation on the site of modern day Bristol, although whether that is because they didn’t settle there, or simply that the evidence of it has been destroyed by thousands of years of subsequent building and rebuilding, I cannot say.

Either way, to find any real evidence of Bristol proper, we need to continue onto the post-Roman period, and even then, it is surprisingly scanty. While Bedminster is detailed in the Domesday book as having 25 villagers. 22 smallholders. 3 slaves. 1 priest, Bristol doesn’t get a proper entry in the 1086 survey at all. We know it existed by this point, because a coin was issued there by Aethelred in 1010, and coins were only issued in market towns. But we’re not really sure how far back the Saxon market town began.

St Peter’s church today stands in ruins, bombed during WW2 and preserved in that state as a memorial to the Bristol civilians killed in the war. The oldest parts of this building are from the 12th century, but the Domesday book implies St Peter’s church already held three hides of land by 1086, larger than a typical parish church, and perhaps indicating it was a minster. Some sources suggest it could have been founded as early as the 8th century.

Similarly, while the Saxon origin of the name “Bristol” tells us the Saxons built a bridge here, we simply cannot put an exact date on it. The first stone bridge was built in the 13th century but timber ones would have predated that by centuries, the earliest perhaps being pontoon bridges. Many sources seem to assume all bridges were at the site of the current Bristol bridge, but a few suggest the earliest ones may have been slightly upstream.

Naturally, the Avon influenced the choice of this location. It was far enough upstream for the river to be spanned with the engineering of the time, but also far enough downstream to be navigable by sea-worthy ships, at least at high tide. I mentioned Bristol’s role in the Atlantic slave trade in my last video, which is by now rather well known, but I was more surprised to discover that international slave-trading was one of the port’s main activities even back in Saxon times, exporting mostly English slaves to Ireland.

However, the real key to the siting of Bristol is arguably not the Avon, but another of its tributaries, the 'Froom', spelt Frome.

The Frome that I overlay on this map should be taken with an extreme pinch of salt. In the upper reaches, I have simply traced today’s river, even though it has surely changed by both natural and man-made means in the last 1000 years. In the lower reaches, there is a certain degree of guesswork. However, we know the Frome came down from the north east, ran very close to the Avon with a short ridge of higher ground separating the two where St Peters is located, then looped around emptied into the Avon just downstream of Bristol Bridge.

This created an extremely defensible area surrounded by rivers on three sides, with only the eastern edge of the Saxon town undefended. So when the Normans turned up in 1066, conquered the country and set about building castles everywhere to cement their grasp, no prizes for guessing the location they chose in Bristol. A castle of some sort seems to have gone up very quickly after 1066, with a more substantial stone affair following in the 12th century. By digging out a moat on the eastern side of the castle between the Avon and Frome, they completed the ‘missing link’ and created an area completely surrounded by water that neatly contained everything a town needed: a commercial area, a religious centre and a military base.

Comparing this to a present day map, it is rather satisfying to see ‘Old City’ appear exactly where we placed the oldest part of the city, and it’s also interesting to see the street name ‘Broad Weir’ appear at the north east of this area - this being exactly where the weir between castle moat and Frome was, and indeed still is - underground. More of that in due course, though.

In terms of the river’s influence on modern Bristol, I will also say this: after tracing this route of the Frome, for the first time in my life I was prepared to grudgingly concede that the street layout of the old city makes any amount of sense whatsoever.

If that sounds suspiciously bitter, well, embarrassing story time. Not long after I moved to Bristol, I had been shopping in the Broadmead area, started walking home, wishing to go south over Prince St bridge, and after dozily following a path of least resistance, found myself at Bristol Bridge pointing in completely the wrong direction. I now finally understand that this path of least resistance was the Frome’s natural path of least resistance.

One thing that’s conspicuous by its absence on the modern map is the castle itself. Small fragments technically survive, but for any tourist expecting an epic historical sight… well… at least the public toilets are crenelated, thanks to the brilliantly ‘contextual’ work of some recent-ish architect.

Anyway, back to our story of Anglo-Norman consolidation. In the twelfth century, city walls were added, and at some point the moat extended to completely encircle the castle. More houses and churches sprung up outside the walls as well as inside, and a stone bridge was constructed across the Frome. Development also occurred in Redcliffe, the other side of Bristol Bridge - not just riverside wharves but houses, churches, taverns. A further defensive wall was added here to protect the port, imaginatively named Portwall. This survives today, linguistically, in Portwall Lane. Of course, the name Redcliffe itself is another one obviously influenced by the river - named after these red cliffs carved by the Avon.

This tinkering with the rivers to create a moat was absolute small fry compared to what medieval Bristolians would pull off in the following century. The port was sufficiently successful to be running out of space, and sufficiently rich to be able to authorise an engineering and labour-based solution that was incredibly ambitious for the year 1240. This was definitely the point where the city began to shape the rivers more than the inverse.

The merchants and port authorities negotiated with the abbot of St Augustine’s Abbey, now Bristol Cathedral, for permission to cut a large trench through an area of marshland to the south of the City which belonged to the Abbey. The portion of the marsh east of this channel was given to the city, which will become relevant later. The abbot held onto the western part, which is why even today the area goes by the name Canon’s Marsh.

The trench extended all the way north to intercept the Frome at the Stone Bridge, and this stretch of water was christened St Augustine’s Reach. This cost thousands of pounds at a time when that probably equated to millions of pounds, but it enormously expanded the available berthing space for ships, and thus established the foundations for Bristol to thrive as the country’s largest and most prosperous port outside London for the following 4 or 5 hundred years, so it’s probably fair to say it was money well spent.

Indeed, medieval accounts suggest this reach soon became regarded as the ‘main’ part of the port, eclipsing the original wharves along the Avon proper.

The building of the first stone Bristol Bridge in the mid 13th century saw the river diverted along a cut beside the Redcliffe portwall, allowing the creation of solid foundations. Maps from 4 or 5 centuries later still seem to show a narrow channel of water here suggesting this ditch was maintained on a smaller scale as a sort of moat.

The Avon had, in Anglo-Saxon times, been the border between the kingdoms of Mercia and Wessex, and although England was now unified, it remained a border between the counties of Gloucestershire, to the north, and Somerset, to the south.

This was a bit of a problem because by now, as we have seen, there was significant residential population and commercial activity in places like Redcliffe, south of the river but functionally speaking, very much part of Bristol. The administrative divide had annoying practical consequences. Legal disputes in Bristol were settled at Gloucestershire’s county courts in Gloucester, 30 miles away, while those to the south were to be settled in the Somerset county court at Ilminster, 40 miles away. Even in a world with cars and planes that would be a drag, let alone the days when horses were the fastest option.

Given how many cross-river urban areas limp on as administratively separate cities for centuries, arguably to their detriment, it’s probably a reflection of Bristol’s great wealth and status in this era that the solution came along as swiftly as it did, from the highest authority. 1373 saw King Edward the third declare "that the town of Bristol with its suburbs and precincts shall henceforth be separate from the counties of Gloucester and Somerset and be in all things exempt both by land by sea, and that it should be a county by itself, to be called the county of Bristol in perpetuity."

In modern terms, that means almost everything on this map is Bristol, except for this tiny slice on the left, which is still Somerset. The boundaries of the 1373 county were much smaller - Bedminster was still in Somerset until the 1830s, for example - but I shall not attempt to map them, as Edward III did not attach a coordinates file to his proclamation.

By the way, it is no sloppiness or mistake which sees me colour only a sliver of land as Somerset, and not half of the river, too. Because the county border doesn’t run along the middle of the river, as you might imagine. The Avon belongs entirely to Bristol, not just here, but all the way to the Severn estuary, and true to Edward’s insistence of it being “exempt both by land and sea”, the City’s boundaries even extend far into the Bristol Channel. Of all the rivers’ influences on the shape of Bristol, in a strictly literal sense, this one might just be the strangest.

The next few hundred years were frankly rather uneventful, for the purposes of this particular story. This supposedly 16th century map shows the river system of Bristol essentially unchanged. One change worth noting is the disappearance of the castle, demolished by this point. The western part of the moat is invisible on this map, suggesting it had already been covered and built over. Most of the eastern moat has had the same treatment, although a spur off the Avon survives above ground. Slightly more truncated, it continues to do so today, vanishing into this tunnel here, but unlike the dried up western arm, this side is still navigable by small boats for the determined urban explorer, up to the weir with the Frome.

If we stretch the definition of river somewhat, while we’re listing Bristol locations with names based on its natural hydrological features, we can sneak in a quick mention for the warm springs at the bottom of the cliff near Clifton. Known since at least the fifteenth century, in the 17th century they were briefly fashionable for their supposed medicinal value, and gave us the district name ‘Hotwells’.

The chunk of marsh to the east of the Frome, given to the city, became known as Town Marsh and by the early 18th century it had been drained. Needing money, the city council took advantage of this large, centrally-located piece of undeveloped land they happened to own, and embarked on arguably their first real piece of town planning with the development of Queen Square. The following decades saw similar grand planned squares pop up in St Pauls and Clifton as Georgian Bristol expanded, but it was not until the turn of the next century that the authorities embarked on the next ‘Grand Plan’ for Bristol’s rivers.

For such a Grand Plan to actually happen required the complex confluence of political will, economic conditions and civil engineering abilities - and I shall explore all these factors in precisely zero detail in this video, lest it become even longer than it already is. That depth can wait for another day, as can coverage of the many and varied schemes which were touted but never built. Here, I will merely narrate the basic facts of the physical changes to Bristol’s river system, occurring between 1804 and 1809.

The main aim was to hold the water level within Bristol at high-tide levels. To that end, the river was dammed, down near Hotwells. A series of locks to and from a large entrance basin, known as the Cumberland basin, was created. The basin allowed many ships to leave or enter at the same time more efficiently than passing through locks one by one.

The main tidal flow of the river was diverted near Totterdown, down a new cut which became known simply as the New Cut, and today is known as the New Cut.

The western portion of the harbour was still being fed by the Frome, but to maintain current and water levels throughout, an additional feeder canal was constructed from Netham weir to just near Temple Meads station. This feeder canal became known simply as the Feeder Canal, and today is known as the Feeder Canal.

The New Cut intercepted the Malago, severing it from its original mouth onto the Avon. The Treen Mills pond was recycled into another transfer basin, with locks to and from both Harbour and New Cut, allowing an alternative entrance for smaller craft. This transfer basin became known simply as the… no, I jest; here, the Victorians displayed a little more inventiveness in naming, christening it the Bathurst basin after a local MP. Given that this MP was a fervent supporter of the slave trade, this is perhaps unfortunate, and I wonder how long before a movement arises to rename it Treen Mills basin or Malago basin.

The effect of all this hydro-engineering on Bristol as a city was obviously fairly extensive. Firstly, as I described in the intro, it meant the Avon in central Bristol no longer feels like a proper river. Secondly, it dragged the city westwards once again. Before researching this video, I had assumed that wharves and warehouses extended far down the Avon long before the Floating Harbour was built. In fact this was not the case; both the port facilities and the city were still fairly tightly clustered around the Frome. Even decades after the harbour was built, in the 1820s and 30s much of Spike Island was still open farmland, but eventually the presence of reliable water levels ensured development and urbanisation spread right down to the western end of the docks.

Speaking of Spike Island, turning this strip of land into an island was another way in which this project had a long-term impact on the urbanity of Bristol. Islands have a tendency to develop down their own, well, insular path, and even in this example, where its island status may seem to be something of a technicality, the relative lack of integration was and is enough to result in the area having a unique vibe. Actually a slightly weird one, in my opinion, but yet again I will have to defer any elaboration on the subject to a future video.

With authorities fearing that a single bomb on the Bathurst basin’s locks could result in the entire Harbour being drained, they were permanently blocked up in WW2, making Spike Island not technically an island any more. The lock and basin at Totterdown was also blocked at this time.

The creation of the feeder canal had made the St Philips marsh area island-like too, and I should also note that railways came sweeping through this area in the 19th century to similar effect. The canal (and railways) made it a nice place to locate an industrial operation, but perhaps rather less attractive for residential development. Today, some 200 years later it’s still largely industrial or post-industrial in character; we are still at the “masterplanning” and “public consultation” stages of large-scale redevelopment.

The great works of 1804 to 1809 were not the end of things. In fact, they directly precipitated the next big intervention. As was common for urban rivers at this time, the Frome was in general use as an open sewer, which was fine(ish) when the sewage was reliably swept out to sea by the tide, but rather less fine when it flowed into an essentially stagnant, dammed up harbour pool.

By the 1820s, the smell was unbearable, and in 1825 the Frome was intercepted at Stone Bridge, diverted into an underground pipe called Mylne’s Culvert which travels underneath the Floating Harbour and empties into the New Cut near the Bathurst basin.

I’m not quite sure what I found more mind-blowing: that almost 200 years ago, people diverted one of Bristol’s rivers beneath another, or that such an engineering feat was so well-hidden and seemingly uninteresting to everybody else, that I’d lived here for years without even realising.

Impressive as this was, though, it seemed to set a trend for burying rivers which with hindsight is arguably unfortunate.

The Frome was covered from Wade Street, near today’s Cabot Circus shopping centre, to the Stone bridge in 1858, then from the Stone bridge to the drawbridge in 1893, then in 1938 from the drawbridge down to where St Augustine’s reach ends today. This grille, I had always imagined, was the mouth of the Frome, and I suppose technically it sort of still is: it is still connected, and serves as an overflow outlet when levels are particularly high, but the main bulk of the Frome vanishes down Mylne’s culvert.

Funnily enough, just as the digging of this stretch of Frome had dragged the port’s centre of gravity westwards in the 1240s, covering it up again dragged the city’s centre of gravity westwards once more. The wide open space thus created was an ideal place to create a tram interchange, as this area became known as the Tramways Centre. After the trams disappeared, this was shortened to simply ‘The Centre’. It’s debatable whether Bristolians would call this the city centre - I think a majority probably wouldn’t, but it is certainly a centre.

The Malago met the same fate as the Frome. As Bedminster urbanised in the 19th century the river was progressively culverted underground, so that today almost no trace of its lower reaches is visible above ground. It empties into the New Cut from these outlets.

So what of the future?

The obvious question is surely whether any of these rivers can be ‘daylighted’, to use the urban planning jargon: brought back to the open. In fact, this was one of the options considered in the late 90s for the lower section of the Frome, but in the end this never happened.

In Bedminster in 2021, happily there are some brighter prospects. The council are proposing to restore a natural, above ground channel of the Malago through this part of Bedminster green, a proposal which 89% of consultation respondents supported. So there’s a good chance that a future version of this video would need to incorporate at least one more change on the map, and hopefully many more as other culverted stretches are restored to something resembling their natural state, enhancing neighbourhoods for humans and more importantly supporting a greater range of wildlife.

It seems impossible at present to imagine this logic being extended to the Avon itself. I can only assume the Floating Harbour will long outlast me. But perhaps the next century can see Bristol’s urban development around its tributaries centred around a sustainable, ecology-first philosophy. We can but hope.

That’s all for this video. As most of the maps were drawn by painting on top of open street map, I guess that makes them derivative works, and I am obliged to licence my changes back to them. For the record, I’m totally happy to do so, however I’m also aware that they would have no use for fixed resolution raster graphics embedded in a video, even if they wanted to map things from thousands of years ago, which they don’t. So I can’t really give this work back, but nevertheless, big thanks to this amazing project, and thanks also to all the other photographers, writers and so on that I’ve drawn upon for this video.

If you enjoyed please subscribe in case I ever get around to making one or more videos on the history of the Floating Harbour, or any of the other topics rattling around my brain. Cheers!