Canal Engineering and Architecture

Canal tunnels, bridges, aqueducts and locks

Yorkshire's Bingley Five Rise Staircase

The engineers who built the canals, men such as Telford, Brindley and Rennie were essentially the first civil engineers, changing the landscape in a way that few had done before them.

Building the canals over a short fifty year period was a stupendous undertaking, transforming the countryside and man's place in it using private capital and the enthusiastic support of parliament.

At a time when roads were poor and disjointed, a national system capable of moving large tonnages of bulk goods from North to South, East to West, coast to coast, was developed through personal initiatives, enthusiasm and human labour.

Civil engineering began here. An army of navvies (navigators) was mobilised which moved from canal project to project, doing all the hard labour by hand, and often terrorising the neighbourhood in the process! Almost uniquely the results of their labours, locks, bridges, buildings, are still in daily use, fulfilling their original purpose because of a design integrity and honesty that has lasted hundreds of years.

Puddle clay - Montgomery Canal restoration 

Critical to the success of these shallow man-made waterways was the technique, pioneered by Brindley, of employing puddling clay to produce a watertight clay-based lining material in the canal floor and sides. Puddle clay was used extensively in UK canal construction and later used more widely as the core within earth-fill dams.

The photo on the right shows a new puddle lining to the sides of a restored section of the Montgomery Canal. A huge plug of puddle clay temporarily blocks the end of the canal.

Pontcysyllte Aqueduct

Aqueducts were not much liked by the early canal builders because the weight of the water and the clay needed to keep the canal trough watertight required a very substantial structure to support it.

Masonry aqueducts were quickly superseded with cast iron trough supported on tall slim masonry pillars.

The Pontcysyllte Aqueduct (above) on the Llangollen Canal is the most visited and photographed in the system.

Swing Bridge

 The second most popular item of engineering (after locks) that narrowboat enthusiasts look forward to experiencing are the movable bridges.

They were cheaper to build than fixed bridges because they didn't require the same heavy foundations and structure and are particularly suited in situations where the canal divides a farm or a lane that has very little traffic.

Lift Bridge

Canals which were short of construction money often used lift bridges, as on the Oxford Canal and on the Llangollen Canal.

Lift bridges are counter-weighted and usually operated manually or by using a windlass. Swing bridges are also common. They are usually build with a pivot point on one bank and one span crosses a narrow section of canal (known as a bridge hole).

Building tunnels was probably the most difficult engineering task facing the early canal builders. They were avoided wherever possible, taking winding routes around hills, as on the Oxford Canal, or climbing up and over the hills via flights of locks, as on the Rochdale Canal. However both increased journey times, and the extra locks often led to water shortages at the higher levels.

Wast Hill Tunnel north entrance (2493 m long)

Tunnels were usually built by laying out the straight route across the hilltop and then sinking a number of shafts. The shafts were aligned on the surface using a telescope. Digging began in both directions from the bottom of all the shafts, and from the tunnel entrances. Surveying techniques were basic at first, using plumb-lines. The early tunnelers were miners who were not used to taking accurate headings, so the horizontal shafts sometimes didn't meet up correctly, The very early Saltersford tunnel has an obvious sharp kink in it.

Newbold Tunnel on the Oxford Canal

Few early tunnels had towpaths, so the horse would walk over the top and the crew, possibly with some local helpers, would "leg" the boat through, pushing with their feet against the tunnel sides or roof. This was a slow and arduous job, often taking two or three hours and causing considerable bottlenecks, especially if the tunnel was too narrow for boats to pass.

Shrewly Tunnel

Some tunnels had ropes or chains connected to the walls to pull boats through on. Later steam or electric tugs were used before powered narrowboats became common.

Latter tunnels were built with an included (occasionally two) towpath. Occasionally a separate towpath tunnel was constructed. The photo on the left is of Shrewly Tunnel passing under the village of Shrewly showing the separate towpath tunnel on the top right.

As you can tell, we're expecting that our trip will be a wonderfully absorbing engineering experience. We're looking forward to becoming totally immersed in both the engineering and the associated industrial revolution history and sharing that enjoyment with you and our friends and family who will be joining us for parts of the adventure.

More soon,
The Skipper.