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Transport / Mass transit

So how does a canal boat travel uphill?

Sea-faring boats face many challenges, but uphills are not one of them. They have to deal with up-waves, of course, but that’s mostly easy because they just have to float and not flip over, which is a pretty low bar to set for a boat. Unique to canal boats is the need to drastically change elevation.

Coal-carrying boats, the original users of many of the UK’s canals, had to travel from the high coal-rich hinterlands down to the city and back again to keep the city dwellers warm and the factory fires burning. The altitude difference involved in doing so is pretty huge across the UK with the highest canal, Huddersfield Narrow at 654ft contiguously connected to waterways below sea level.

A canal is essentially a very long, very thin lake, meaning any incline will cause water to do its thing: flow downhill and flood the lower reaches. So, instead, different kinds of locks are used to lift boats from one level to the next.

While this works well when dealing with small inclines, locks can’t be too deep because each use would waste too much water. The alternative is what’s called a ‘lock flight’, which is essentially a staircase of locks that can be insanely time consuming to traverse. The Tardebigge Flight in Worcestershire, the longest in the UK, raises the waterway by 220 feet over the course of 30 locks. It takes an experienced crew a whopping four hours to navigate.

So boat lifts are the final piece in this weird puzzle. These are just what you imagine: a way of taking a boat, and the section of canal it’s on, from one level to the next. Lifts have the advantage of being far faster to use than lock flights, while also wasting much less water. Funnily enough the precursors to these feats of modern engineering far predate the relatively simple locks – the ancient Egyptians used crude lifts to get boats round waterfalls on the Nile.

 

The Falkirk Wheel connects the Forth and Clyde Canal with the Union Canal. Credit: Wikipedia/creative commons.

As is the case for most triumphs of engineering, Victorian Britain led the way. The Anderton Boat Lift in Cheshire has been taking water traffic the 50ft between the River Weaver and the Trent and Mersey Canal since its construction in 1875. Far grander boat lifts have since been built in other parts of the world, but little-Englander-waterway-enthusiast types can hang onto the fact the UK got there first. The most impressive modern example is the lift that gets ships over China’s Three Gorge Dam, which is simultaneously the highest and most powerful in world. Not nearly the same size but at least closer to home, the Falkirk Wheel in Scotland is incredible for looking like something out of Star Trek whilst still being a fully functional lift.

So that’s the briefest of outlines for all your boat-raising queries. If want to get more technical, try to wrap your head around the hydraulic systems beneath boat lifts such as Canada’s Peterborough Lift Lock. But if you really want a challenge try to square in your head how it can be that each lift weighs the same whether a boat is in it or not. It times like this I wish I had a bath; not for cleanliness’ sake but to conduct experiments with my rubber ducks. 


 
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