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Aberdeen Harbour North Pier
Pocra Quay, Aberdeen, Scotland, UK
Aberdeen Harbour North Pier
associated engineer
John Smeaton
Thomas Telford
William Dyce Cay
date  January 1775 - 19th October 1780, 1810 - 1815, 1874 - 1877
UK era  Georgian  |  category  Pier, harbour  |  reference  NJ960058
ICE reference number  HEW 1377
photo  © Oliver Dixon and licensed for reuse under this Creative Commons Licence
Aberdeen Harbour is now a world-class port but until the 18th century it was just a channel of the River Dee, with town quays alongside. John Smeaton was called in to alleviate the problem of access past a bar of sand and gravel obstructing the harbour entrance. He suggested a granite pier on the north side of the river mouth. This pier was extended twice in the 19th century and is still in use, though public access is restricted.
In 1136, King David I of Scotland allowed the bishops of Aberdeen to collect a tithe (levy of one-tenth) from all ships trading at the port ó making Aberdeen Harbour Board the oldest existing company in Britain.
By the 16th century, Aberdeen was a hub for fishery, shipbuilding and export trade. Links with Scandinavian and Baltic ports led to improved facilities, including a blockhouse fort on the north side of the harbour entrance (1532), a cargo-handling crane (1582) and a bulwark at Torry on the south river bank (1596-1607) to help deepen the harbour entrance by tidal flushing.
The 1707 Act of Union, uniting the parliaments of Scotland and England, resulted in record levels of trade. However, harbour expansion was limited by the bar of sand, gravel and shingle forming continually at its mouth, caused by longshore drift moving south east down the coast and the flow of sediments deposited by the River Dee, and made worse by onshore winds and tides driving material into harbour.
In 1768, John Smeaton (1724-1792) was asked to advise on improving the harbour. His report of 19th February 1770, suggested constructing a pier on the north side of the river. By constricting the river channel, the structure would aid the scouring action of the river in flood, helping to reduce the bar, and by shielding the harbour mouth would "in a great measure, prevent sand and gravel from being driven in".
However, he noted that the pier "would not, indeed, stop the continual driving of the matter coastwise from the north", though "after the back or outside of the pier is filled up with sand" sufficient material would bypass the pier head, resulting in no obstruction to navigation. Periodic dredging beyond the pier head would also be required.
As completed in 1780, the North Pier curved slightly, convexly to the south, and was some 366m long. Its construction is typical of Smeatonís work, having a trapezoidal cross section comprising external walls of horizontal courses of small squared blocks and a stone core. Founded on the seabed, it contains some 45,700 tonnes of granite, sourced from quarries at Greyhope and Nigg.
The pier was designed to be 1.8m above high water spring tides, and has a 2.4m high parapet wall. The pierís dimensions increase seawards in three stages, giving a height of 4.9-9.1m above the sea floor, a top width of 3.6-7.3m and a base width of 6-11m. The structure terminated in a round pier head (NJ960058), 18.3m in diameter.
Smeatonís original construction estimate was £10,000, though the final cost of the works was £16,000, which included a gratuity of £75 to resident engineer John Gwyn (c.1733-89) in recognition of his efforts.
A survey of 1787 showed that the depth of water over the bar at high tide had increased by 1.1m but wave action upstream had also increased, owing to easterly swells moving along the now deeper harbour channel. In 1788-90, a 'catch pier' (NJ958057) was constructed, projecting into the channel 100m seaward of the landward end of the North Pier. It too was designed by Smeaton.
Between 1790 and 1797, the North Pier suffered considerable storm damage, necessitating repairs. The increased flow in the river resulting from Smeatonís works had scoured the bed of the channel, undermining the pierís foundations by up to 610mm.
In 1797,John Rennie (senior, 1761-1821) reported on the harbour and advised that the foundations of the pier should be protected by two rows of piles and dressed stonework. No action was taken.
In 1802, Thomas Telford (1757-1834) was consulted about improvements to the harbour. In April 1810, he submitted a wide-ranging scheme that included extending the North Pier by some 91m and constructing a South Breakwater almost 244m long, three graving (dry) docks and two wet docks.
In fact, between 1811 and 1813, the pier was extended in stages by another 264m, resulting in a total length of some 630m. The substantial construction has external granite block faces above low water level, with the blocks laid diagonally on the slope from a hand-powered winch, to provide greater resistance to wave forces. The blocks are of around 1 tonne each and enclose a core of broken masonry and random stone, which continues to the seabed at a flatter slope without facing walls below low water level. Its seaward end had a circular head of dovetail masonry.
In 1813 and 1815, the pier head suffered storm damage and was rebuilt both times, firstly with a better foundation and secondly with a longer random stone slope at the seaward end than at the sides. The cost of the works and repairs totalled £66,024, all carried out under the superintendence of the harbour boardís resident engineer John Gibb (1776-1850).
The extension of the North Pier again resulted in the deepening of the channel by increasing scour. From 1867, the height of the bar at the harbour mouth was also reduced by dredging.
Between 1869 and 1879, Aberdeen Harbourís entrance was much altered and extended seawards, supervised by William Dyce Cay (1838-1925), then the board's resident engineer. The work included the building of a new South Breakwater to the east of the existing one, which was shortened, and further lengthening of the North Pier.
During the years 1874 to 1877, the north pier was extended by 152m, to 782m, including work at the connection between the new structure and Telfordís pier head. The base of the extension was constructed by sinking concrete-filled bags, and the top section by in situ casting. The method is a refinement of that used to construct the new South Breakwater in 1869-73.
The seabed under the extension consisted of a layer of mobile sand up to 1.5m thick overlying boulder clay. The sand was removed by a bucket dredger and the concrete foundation of the breakwater constructed as soon as possible afterwards, before the sand built up again. Divers cleared the seabed of debris immediately before the bags were placed.
A 17m long iron hopper barge was designed specially for depositing the bags on the seabed. While it was was moored ashore, a jute lining was put into its box (7.3m x 1.8m wide x 1.7m deep) and filled with wet concrete. The bag's 'lid' was sewn up as the barge was towed into position, then the hopper was opened and the bag dropped into place. The whole operation took about two hours, and was repeated six to nine times a day.
The bags each contained 50.8 tonnes of concrete consisting of 1 part Portland cement, 3 parts sand and 4 parts shingle. Batches were made in eight steam-powered mixers on shore.
The two foundation course are 36.6m wide, forming an apron around the pier intended to prevent wave action from undermining the structure. The bags were laid longitudinally, with overlapping joints. Upper courses were laid transversely over the foundations, with a top course 12.2m wide at 760mm above low water spring tides. Above the bags, mass concrete was cast in blocks of 710 tonnes. Altogether 23,482 cu m of concrete was used. The cost was around £46,000.
In 1880, Dyce Cay resigned and William Smith was appointed resident harbour engineer, remaining in post until 1895. During his tenure, further improvements were carried out at the mouth of the harbour including work on the pier head and the foundations of Telford's section.
In 1907, a provisional Aberdeen Harbour Order authorised new works including securing the foundations of the North Pier. In 1979, major repairs were carried out on the Telford structure of the North Pier.
Resident engineer (1775-80): John Gwyn
Resident engineer (1810-5): John Gibb
Resident engineer (1874-7): William Dyce Cay
Contractor: direct labour
Research: ECPK
"Harbours and Docks" by Leveson Francis Vernon-Harcourt, 1885, reprinted by Cambridge University Press, 2014
"Reports of the late John Smeaton, F.R.S.", Vol.2, M. Taylor, London, 1837
"House of Commons Papers", Vol.29, H.M. Stationery Office, London, 1835
reference sources   CEH SHIJSBDCE1

Aberdeen Harbour North Pier