Popular Mechanics (South Africa)
River lock navigation: We try out an age-old invention on a river in France.
Waterways the world over became more navigable with the advent of locks, and to this day these mechanical components still play a vital role in inland water-travel networks. Mark Samuel experienced some first-hand on a trip to France.
OUR BRIEFING on how to operate the locks had felt, well, brief. Now it was game time. We’d travelled only a short distance upstream from the boat base in Douelle and soon encountered the first lock on our seven-day Le Boat cruise up (and back down) the Lot River in south-western France. As luck would have it, there were no other boaters around to watch and mimic, so the only option was to tackle it ourselves.
If you’re a South African, for argument’s sake, who’s had few to zero run-ins with locks in your life, these large stone- and steel structures can at first appear quite intimidating. We were on a wide natural river after all, and not a constructed canal, and adjacent to this lock (and almost every other one we navigated through) was a fastflowing weir that added to the tension and high levels of anxiety.
We’d been told about the correct order in which the sluice gates and then the main gates need to be opened or closed, how to temporarily moor the boat and control it while the water gushes all around, and how to navigate in and then out the other side, paying close attention to the coloured buoy system which is there to prevent you running aground on the shallower sections. But now it was about putting all of that knowledge into practice, having never actually done it ourselves…
DAYS OF OLD
The use of locks on waterways dates back to ancient times. River transport for trade was commonplace and important, but shallow
river bottoms initially meant only small boats could be used. This led to the building of weirs to dam up sections (known as pounds) of rivers, making them deeper and therefore navigable with larger boats. But moving the boats up and down the weirs (essentially steps) presented a problem, which at first was resolved by using a rudimentary system of flash locks, a dangerous method consisting of a small opening in the dam (or weir), which could be quickly opened or closed. Once opened, a boat travelling downstream would be carried by the flow into the lower dammed portion of the river, while a boat headed upstream would need to be hauled or winched, using brute force against the flow, into the higher dammed-off section. The turbulent torrent of water associated with this method meant that boats often capsized, resulting in loss of life and property.
Next came the staunch-gate system, but it was, perhaps predictably, the Chinese who, during medieval times (the Song dynasty) expanded on this design and devised a more sophisticated solution known as pound locks, where a pair of sluice gates was constructed around 70 metres apart. By lowering heavy timber beams on the downstream side, and raising them upstream, the flow of the river filled the gated-in stretch, allowing boats to navigate much more safely between pounds.
There are now several lock types used around the world, but no matter the design, the general principle remains the same – managing the water level of a temporarily sealed-off section of a navigable waterway, through which craft can be manoeuvred, either upstream or downstream.
UNCHARTED TERRITORY
Step one when approaching a lock, from either side, is to drop off your companion (‘Megan’, in this instance) – you simply cannot navigate through locks alone. There needs to be at least two of you – one to manoeuvre the boat and the other to operate the gates of the lock. It’s even better if there are more people to operate the lock, as the process goes a lot faster.
We were the bare minimum – two – which meant I stayed put at the helm, while Megan scurried off to operate the lock’s manual sluiceand large-gate levers. In hindsight, I realised I’d picked the much more laid-back task, but boat operator is still important (I insisted), because running the boat aground or slamming into the stone walls of the lock is ill-advised.
If you’re travelling upstream and the lock’s lower doors are still closed as you approach, that means the lock is still full from the last boat that was travelling upstream ahead of you. In this scenario, the top gates first need to be closed, then their smaller sluice gates closed too, cutting off the upstream in-flow of water. To do this on the Lot’s locks, you wind the large lever that manipulates the big steel doors – first on the one side, then (if you’re on your own) you walk all the way around and across the already-closed downstream gates, and then you close the other side. (Nowadays, many locks are automated, and you operate them using buttons instead of levers.) Once that’s done, using another set of winding levers, you close off the sluice gates that are mounted at the bottom of each of the big gates.
Next came the emptying of the lock to equalise its water level with the downstream section of river (where I’d done my best to keep the boat in a holding pattern, waiting to cruise into the lock). This entailed the lock operator walking to the downstream gates, and first opening each of their sluice gates using the rotating winding levers. This is where the fun really began for me as the helmsman…
The sudden release of water from the lock caused a turbulent and rapid flow downstream, just where I was idling mid-channel. The rough water threatened to push our large 11.5 metrelong vessel towards the shallower section nearer to the weir, and it took some prompt forwardand reverse throttle use and bow- and stern side thrusts to keep the boat relatively in place. We soon learned that the taller or longer a particular lock, the greater its volume of water, and the higher the likelihood of more turbulence occurring when its water is released downstream.
The mini adventure within the adventure wasn’t over yet. Once the water inside the lock had been released and was at the same level as my section of river, the main lower gates were opened. Slowly I edged the boat forwards, again manipulating the throttle and side-thrusters to get the alignment right. Into the deep, stone
walled lock I inched the boat, until positioned nearer to the downstream side with enough room for Megan to close the doors behind me. I tossed up lines off the bow and stern, which Megan looped around steel bollards on the top of the lock wall and then threw back down to me. Stationed at the helm on the upper deck (there were two steering-wheel locations on our boat, with one inside the cabin), I held the ropes firmly, one in each hand, ready to keep the boat stable during the filling of the lock.
With the rear sluice- and main-gates closed behind the boat, Megan began the energysapping process of opening the upper sluice gates, releasing the upstream water into the lock, thereby commencing the filling process. The locks on the Lot can accommodate two boats in tandem. If you’re unlucky enough to be the boat in front (headed upstream), the filling process when the upper sluices are opened can mean you’re in for quite a roller-coaster ride. Fortunately, for our first lock experience at least, it was just our boat in the lock, so I positioned her near the downstream side. Even still, I needed to use some effort to keep the boat stable as the water level rose to match the upper section of river.
Once the water level had equalised with the higher pound, Megan opened the large gates, and I manoeuvred gently back upriver, picking her up on the way past the adjacent jetty.
During our river-cruise adventure on the Lot with Le Boat, we navigated through 26 locks in total (13 in each direction), and by the end of it felt ready to take up careers as merchant sailors of old. There’s definitely no better way to explore the countryside of southern France than on a river holiday, especially when your boat’s equipped with bicycles for heading off from your mooring spots, scouting the ancient villages, and seeking out croissants and baguettes in the boulangeries.
The locks of this region are a remarkable piece of engineering infrastructure that was instrumental in the area’s development. Nowadays, they simply form part of a tourist route, but it’s extraordinary to get to use and experience these timeless tools yourself, knowing that it’s essentially the same concept that was employed to navigate these waterways more than a thousand years ago.