Since the creation of the Floating Harbour in 1809, Underfall Yard has been crucial to its operation and maintenance. Before this time, much of the site was under water: the original course of the River Avon ran through Underfall Yard.

Overfall…

In 1809, as part of the creation of the Floating Harbour system, William Jessop developed the Overfall dam across the River Avon allowing surplus water from the harbour to flow into the New Cut. The water of the River Avon carries lots of silt (mud). The water enters the Floating Harbour, slows down and isn’t able to carry the silt any longer. The silt settles in the harbour, which eventually builds up and reduces the depth making it difficult for ships to navigate. The Overfall Dam had sluices next to it, which could be used to remove silt. However, the main method was to empty the harbour and dig it out.

…to Underfall

Digging the mud out was hugely disruptive to shipping and trade. In the 1830s, Isambard Kingdom Brunel was asked to propose a solution. He suggested further developing the original sluices and recommended the use of dredgers, a type of boat, to remove the silt. The sluices have been changed and renewed several times since and today’s system was installed in the 1880s.