Over a thousand years ago Bristol's harbour developed around the lowest bridging point of the River Avon. The exceptional tidal range of the Severn Estuary and Avon carried laden ships into the city and scoured the river of silt.
Local trade flourished between Bristol, South Wales, the Severn ports and Ireland. During the Middle ages the port grew in prestige, trading with the Atlantic seaboard, Iceland and the Mediterranean. The American colonies brought more opportunities for Bristol merchants including the notorious slave trade to the West Indies.
As ships became larger and trade increased the quay space became overcrowded and when the water drained away at low tide the ships lay grounded in the mud. Finally the Bristol Docks Company adopted the proposals of engineer William Jessop to create a non-tidal harbour.
The ‘Floating Harbour’, constructed between 1804 and 1809, trapped the water behind lock gates allowing ships to remain floating at all times.
An earth dam was built at Underfall Yard and the Cumberland Basin lock system constructed. The New Cut was excavated to bypass the Floating Harbour and carry the tidal waters to rejoin the River Avon near Temple Meads Station. The digging of the Feeder Canal to join the river at Netham Lock completed the system. The canal both fed the new harbour with water to maintain the dock level and provided a connection for barges to the river Avon, to Bath and the Kennet and Avon Canal. This huge engineering project formed Bristol Docks much as they exist today.
Eventually, the growth in the size of ships and the narrowness of the river
through the Avon Gorge meant the end for Bristol as an international trading
port.
Ocean going traffic began to use the Avonmouth Docks, developed during the
1880's and 90's. Bristol remained viable for smaller vessels and commercial
use continued until 1974.
Underfall Yard
The damming of the river to make the harbour had created new land where the docks maintenance facility was established and remains today.
William Jessop had created a weir in the dam at Underfall to allow surplus water to flow back into the New Cut, this was known as the 'Overfall'.
By the 1830's the Floating Harbour was suffering from severe silting and Isambard Kingdom Brunel devised a solution. In place of the Overfall he constructed three shallow sluices and one deep scouring sluice between the harbour and the New Cut, together with a dredging vessel. This drag boat would scrape the silt away from the quay walls. When the deep sluice opened at low tide, a powerful undertow sucked the silt into the river to be carried away on the next tide. The shallow sluices enabled adjustment of the dock water level according to weather conditions.
This 'Underfall ' system was re-built in the 1880's with longer sluices and the yard above enlarged. Brunel's method of silt disposal is still in operation today, but the silt is carried in mud barges or pumped to the sluices through a quayside pipe system from the more efficient modern 'Cutter-Suction' dredgers. These pipes are visible on the quay to the east of you.
Docks 'Municipalisation'
The Bristol Docks Company never achieved commercial success and was taken over by Bristol City Council in 1848. In 1880 the Council bought the Slipway and Nova Scotia Yard, now known as Cambria Yard, to enlarge the docks maintenance facilities.
Most of the buildings and engineering installations you see were constructed between 1880 and 1890 under the direction of Docks Engineer John Ward Girdlestone. The quay walls were rebuilt to enlarge the yards, the docks hydraulic power system was extended, and the steam powered hydraulic pump house was built on Nova Scotia Yard. The 'Patent Slipway' for lifting vessels was built in 1890 on the site of a previous slipway.
The yards have been little altered recently except for the replacement of the three storey 'A' block over the sluice paddle room after bomb damage in the 2nd. World War. Constructed to the high standards typical of the period, these Victorian work yards are now scheduled as an Ancient Monument.
Docks Maintenance Workshops
The original blacksmiths and engineering workshops remain in use while the shipwrights' shop is now used as a carpentry workshop.
The machinery was originally powered by steam and the boiler, the engine and drive shafts remain in place though no longer functioning. In the blacksmith's shop there are still four forges. The large building with its roof extending to the quayside was the original carpenters shop and equipped with a hand operated gantry crane, since dismantled.
During the 20th.Century the western parts of the yard were leased to P & A Campbell Ltd., operators of the White Funnel Line of paddle steamers as a maintenance base. When this activity ceased the buildings fell into disuse until, in 1997, the Underfall Trust began the restoration of the buildings and patent slipway and now manages the slipway, boatbuilding and repair workshops in this area.
The Sluices
These are under 'A' block on the Cumberland Road boundary and are still operated almost daily to adjust the dock water level after rainfall.
Although now automated, this process still requires vigilance from the Docks Engineer and his staff. The original cast iron sluice paddles have recently been renewed and one of the old paddles is displayed outside 'A' block.
The Slipway
The Patent Slipway was restored by the Underfall Trust in 1998-9. The restoration was based on the slipway built under the direction of John Ward Girdlestone in 1890. This slipway had replaced a predecessor built in the 1850's by boatbuilders Ross & Sage.
The Patent Slipway or 'Heave-up Slip' was patented in 1819 by shipbuilder Thomas Morton of Leith in Scotland. Morton invented the notion of constructing a fixed runway into the water with a timber cradle on it. The ship is floated onto the cradle and secured. The cradle is then drawn out of the water. The device was a low cost alternative to dry docks for maintenance and repair work.
The Ross & Sage slipway appears to have been powered by a hand capstan, which was later replaced by a steam engine. The 1890 replacement was originally driven by an hydraulic engine powered by the dock's system. In 1924, an electric motor was installed which still operates today. The winding gear and motor are housed in the shed at the top of the slipway.
The Bristol slipway is relatively small with a cradle of 100 feet (29.5m) and a runway of 265 feet (80.7m) and could lift vessels up to 250 tons (246 tonnes). Cardiff had two slipways with cradles of 350 feet (107m) and runways of 900 feet (275m). In 1920 there were some 200 of these slipways operating in the United Kingdom. The Bristol patent slipway must be one of very few of its era still functioning. It is in regular use and can lift most of the larger boats now in Bristol docks.
The recent restoration required the complete renewal of the underwater runway with steel piling to replace the previous timber, iron and masonry supports. The above water track was re-laid, reusing the original cast iron centre rails with their integral ratchets. The cradle was completely rebuilt on the original pattern.
