Man-made canals have only existed for a couple of hundred years, but the challenge of crossing rivers has been around for much longer.
The building of canals involved the severance of land, as well as of existing roads and footpaths, so new bridges were required to solve the problem. Original canal bridges came in many forms. Often these were hump-backed, in brick or stone, with an arch accommodating the canal and towpath beneath. More elaborate structures were sometimes erected when the canals cut through affluent country estates, like those at Cassiobury Park or Chillington.
While some of these original bridges have survived, many that carry road crossings have been modernised, so we have a range of canal bridges today.
Wooden bridges were common during the hey day of the canals because they were cheap to build, especially compared with brick or masonry bridges. Wooden bridge walkways could be constructed using just a single timber beam.
Cast iron bridges were also popular on certain canals. These elegant structures – built to a common design - can be seen today around Birmingham and the Black Country Canals. They can also be spotted on the northern section of the Oxford Canal.
Some of our earlier canals featured opening bridges. These opening bridges were relatively cheap to build and they could also allow large craft to pass through them. Opening bridges could be accommodation bridges (linking land), road bridges and in some cases even railway bridges.
Opening bridges could hold up traffic on waterways, roads or railways considerably, and some would later be replaced by overbridges.
Opening bridges could be swivel or bascule. Bascule bridges or drawbridges lift up from one side of the canal - perhaps the most attractive examples are those on the Llangollen Canal. Turnbridges or swivel bridges are simpler, turning round a single point. Early examples were built in timber, with some later ones in steel.
As narrowboats were originally towed by horses, special bridges were required. Sometimes the towpath has to move from one side of the canal to the other. At these points, there was a danger of the horse’s towline getting tangled as the horse completed the manoeuvre across the canal. Early canal engineers soon came up with the solution of turnover, or snake, bridges. The smooth lines of these bridges make them among the most attractive waterway structures.
At the tail of many locks, small bridges were provided to avoid the need to cross the lock over the bottom gates. These ranged from brick bridges to 1960s flat decks built in concrete. Those on the Stratford Canal and elsewhere were known as “split bridges”, built in two halves to allow a towrope through the centre of the arch.
This article has been edited with the kind assistance of Joseph Boughey
Last date edited: 21 December 2017