Underfall Yard
The construction of Cumberland Basin and the New Cut meant that an island was formed between where the river was diverted and Bathurst Basin at Redcliffe. This island became known as Spike Island.
Jessop’s plan included an ‘Overfall’ Dam to allow excess water in the Floating Harbour to flow over into the New Cut, but by the 1830s the harbour was becoming badly silted up.
Although Jessop had included sluices with his Overfall Dam, the main method of clearing the silt out was to drain the harbour and remove it by hand, which was less than ideal to say the least.
Isambard Kingdom Brunel was brought in to make improvements to both Cumberland Basin and the Overfall Dam, and for the Overfall Dam he recommended developing Jessop’s sluices further and using dredger boats to remove the silt.
He devised an Underfall system where three shallow sluices could be used in a way that would control the harbour water level according to the tide and weather conditions, and a fourth ‘deep scouring’ sluice which could be opened at low tide when a powerful undertow (undercurrent) would suck the silt into the New Cut to be carried away by the next tide.
This Underfall system is still in use today, although a more modern system of dredging is used.
Originally posted 2019-01-19 16:32:05.