At places along the canal where it gets very narrow, you might notice vertical grooves cut into the masonry on each side. These are for holding stop planks. You probably won’t see the planks in place, but they might be nearby, stored in a shelter by the towpath.
Stop planks are important tools for maintenance of the canal. Simple planks of wood with metal brackets on the sides for handles, they are easily overlooked. But they can save a canal from collapsing or running dry.
If a length of canal begins to leak, or needs to be drained for repairs, the stop planks are lowered into the grooves at each end of the section. The planks stack up to form dams. The water between two dams can be pumped out, exposing the canal bed for repairs. On either side of the dams the water level stays high and the canal can still be used.
Stop planks are a very simple but effective engineering solution. They were first used over 200 years ago and really haven’t changed since then, because they still do the job perfectly.
Geoff Pursglove talks about rescuing the Ashby Canal breach
Geoff Pursglove is the Canal Project Officer for Ashby Canal in Leicestershire. In this film he talks about how a farmer, local rugby players and other volunteers put stop planks in place when the canal breached in December 2020. Click here to see the video.
More Information About Stop Planks
At Horseshoe Falls, there is a large store for stop planks. The small stone building beside it is a late nineteenth century workers’ mess, where canal maintenance workers could stop for a tea break and warm themselves by a small fire.
This stop plank shelter is in the garden of Llanddyn Cottage. The house was originally built for a canal lengthsman. It was his job to patrol a length of the canal and report or repair any damage. Stop planks were an important tool for their work.
Stop plank grooves are easily overlooked but they are quite common. Look out for them wherever the canal narrows, especially near bridges. They always occur in pairs, one opposite the other on each side. These are next to Chirk Bank Bridge.
Stop planks are traditionally made of heavy, dense timber such as oak. When in place, any gaps and leaks are plugged with a mixture of clay and ashes. These planks on the Caldon Canal used ash from the nearby Etruria Potteries Industrial Museum.
The brackets on each side of a stop plank are called staples. Here you can see how ropes are attached to lower the heavy planks into the grooves. These volunteers rushed to help during a breach on the Ashby Canal in Leicestershire.
When the canal breaches and bursts its banks, the loss of water is often very fast. Stop planks either side of a breach can help to keep the water levels high until the breach is repaired. A breach at Bryn Howel in 1960 left boats stranded in the empty canal.
The scale of damage caused by a breach can be seen on the Llangollen Canal at Middlewich in 2018. This took many months to repair and cost the Canal and River Trust over £3 million.
Stop planks are also used for routine repairs to the canal. These are in place on the Chirk Aqueduct, so that the trough can be emptied for cleaning. The pump on the left drained the water on one side, leaving the basin at Chirk Tunnel ‘in water’.
Because the Llangollen Canal provides the public water supply for south Cheshire, water flow along it cannot be interrupted for long periods. For the routine periods when Pontcysyllte Aqueduct is drained for maintenance, a pumping station has been built to bring water from the River Dee up to the canal at Froncysyllte.