Blackweir dock-feeder weir, Cardiff
The weir you see here diverts some of the river Taff’s water into the dock feeder canal, built in the 1830s to replenish the new Bute West Dock. The water continues to top up the former Bute East Dock and the working Roath Dock.
The weir is in the top left corner in the 1948 aerial photo, courtesy of the Welsh Government. The feeder canal leads to the bottom right corner.
Earlier weirs, a little further upstream, diverted water to mill streams in medieval times. One is mentioned in a 1315 document. A new weir and mill channel were created in 1751.
Construction of the dock feeder canal began in 1834, three years before construction of the new dock. The venture was promoted by the Marquess of Bute, who owned much of the land in Cardiff, including what’s now Bute Park.
In October 1834 prospective builders of the feeder were invited to view the plans and specifications at the Bute Ship Canal office (the dock was identified as a “ship canal” in the project’s early stages). An important function of the feeder canal was to supply a reservoir near the dock which would flush the dock entrance and low tide, keeping it free of siltation.
In 1835 the Glamorganshire Canal was temporarily closed to traffic while a tunnel for the feeder canal was excavated below it (near the north eastern corner of the castle).
From the weir, the canal crosses fields that once belonged to Blackweir Farm, which the Marquess bought in 1836. The upper section of the feeder canal made use of an earlier mill stream.
The Marquess specified construction of a footpath alongside the feeder from the river to the castle. You can follow the path – now lined by deciduous trees - from the weir to the south eastern end of Bute Park. See our page about Fisher’s Bridge for details of wildlife along the feeder. The water later flows underground through the city centre, but work began in 2022 on uncovering it at Churchill Way.
In the autumn sea trout and salmon leap over the weir to reach spawning grounds upriver. The footbridge over the Taff here was built in the 1980s by Cardiff University in tandem with development of nearby student accommodation. Engineering students were involved in the bridge project.