Engineers investigating last year’s dramatic breach of the Llangollen Canal near Whitchurch have concluded that a long‑term, undetected leak beneath the canal bed was the most likely cause of the collapse.
THE Canal & River Trust published the findings of its interim investigation into the incident last December which saw thousands of tonnes of water escape from the canal, flooding nearby land. According to the report, the failure was probably caused by a combination of factors unique to the site, including a deep-seated leak that had gone unnoticed under the trust’s existing inspection regime. Investigators believe the slow leakage eroded material beneath the canal bed over time, creating a void that eventually led to a sudden collapse of the embankment.
John Ellis, national fisheries and angling manager at the CRT, with MEM Fisheries during the rescue. CRT
The embankment itself is steep-sided and largely constructed of sand, a material particularly vulnerable once undermined by water movement; engineers said the combination of hidden erosion and the embankment’s composition proved critical.
Crucially, the investigation has ruled out a number of commonly suspected causes. There was no evidence that heavy rainfall, overtopping of the canal, fallen trees or animal burrowing played any role in the breach.
While the findings are described as interim, the trust says no additional factors have been identified so far. Further inspections are still to take place, including checks on two nearby culverts, although these are not currently believed to have contributed to the failure.
Trust chief executive Campbell Robb said the breach was “distressing and frightening” for those affected and reiterated the organisation’s commitment to restoring navigation safely.
He also confirmed that the investigation is already prompting changes to how historic waterways are monitored. While the trust’s inspection regime is comparable to those used by similar organisations, it is now being strengthened with the possible introduction of new geophysical surveying methods to detect issues beneath canal beds that are not visible from the surface.
The interim findings come as repair work moves forward. Although the full restoration is expected to take much of the year, preparatory works are already underway, including construction of a 100-metre access track across farmland from the A41. The route will be used to deliver about 20,000 tonnes of aggregate needed to rebuild the damaged embankment. Construction is expected to begin once detailed ground investigations are complete and the final design for the rebuilt embankment is confirmed.
The trust says the ultimate aim of the investigation is not only to explain what went wrong, but also to improve the resilience of historic canal infrastructure nationwide by identifying how similar failures can be prevented in future. The full report is expected to be published in the coming months.
Meanwhile, shortly after April’s issue of Towpath Talk went to press, the Canal & River Trust announced that about 1000 fish washed into a neighbouring farmer’s field during the breach were safely returned to the canal. The pool of water in the field, which was up to six feet deep in places, was gradually drained to around knee height to allow specialist rescue team from MEM Fisheries to catch the fish.
John Ellis, national fisheries and angling manager at the trust, said: “The fish appear to be in good health, having temporarily been rehomed in a field of water for two months. The breach has had a real impact on people living and working on the canal and nearby, and this rescue is one small but important step in putting things back together.”
