Captain Bligh and Bull Island

It is widely believed that Captain William Bligh of the Royal Navy designed the North Bull Wall of the Liffey channel, causing the development of the North Bull Island. But do the facts support this?

 

By Rob Goodbody and Richard Nairn

 

The biggest problem to face the port of Dublin over the centuries was the sandbank, or sand bar, that ran north–south across the middle of the bay, creating a shallow area at the entrance to the Liffey channel. At best this was an inconvenience, as it meant that ships had to wait for high water before they could enter or leave the port. At worst it was a positive danger. Ships could easily run aground on the bar, though the risk was reduced significantly by using pilots who knew the channels well and would guide ships in and out of the port. Worse than the danger of running aground was the danger of a ship being caught in the bay by a storm and being unable to run for shelter because the bar prevented access to safer waters. Over the centuries many ships were wrecked after being caught in such an exposed position; the worst storms were the easterlies and north-easterlies, which blew straight into the bay. In such a storm it would be difficult for a ship to sail out of the bay, even if there had been a safe shelter nearby—which there wasn’t.

Silting problem

This problem of silting in Dublin Bay increased over time as ships evolved, becoming larger, heavier and requiring deeper draught. The caravel was the ocean-going ship developed in Portugal in the fifteenth century and used by explorers such as Magellan, Dias and da Gama. These ships had a displacement ranging from around 50 tonnes to 150 tonnes. In the sixteenth century the galleon was developed and remained the dominant large ship until the late eighteenth century; most were below 500 tons, though they could be larger. Later in the eighteenth century the brig became the dominant large transport ship, though some larger vessels also traded through Dublin. Even in 1804 the Ballast Board suggested that the port could operate effectively with ships of just 200–300 tons.

The North Bull was the original name given to the shallow sandbanks north of the Liffey mouth, between Clontarf and Sutton. Following the building of the great South Wall in the eighteenth century there were noticeable changes in the sandbanks to the north of the river. In 1801 Richard Broughton, secretary to the Ballast Board, in a letter addressed to the Directors General of Inland Navigation in Ireland, commented that ‘the north bull … has increased very much, both in extent and height, during the progress of the works on the south side, and more especially since their completion’. This was partly due to the scouring of sand from the mouth of the Liffey since the building of the great South Wall. This sand was swept north by the circulation in the bay.

Bligh’s survey of Dublin Bay

William Bligh was born in 1754 in England and as a young man became an officer in the Royal Navy. He is best known for his exploits in the Pacific Ocean, where he was a victim of the famous mutiny under his command of the HMS Bounty in 1789. He was set adrift in a small boat and undertook one of the classic sea voyages with a group of loyal men until he reached Timor, a journey of 3,618 nautical miles (6,701km).

In January 1800 Captain Bligh was invited to survey Dublin Bay and make recommendations for its improvement for shipping. Bligh was reputed to have been involved in the construction of the South Wall of the Liffey, but he did not visit Dublin until after the wall was completed. It was, however, Bligh who suggested that the seaward section of the wall be raised in height, as it is clear from examining the wall that the topmost section was added later. Bligh’s most important contribution was his well-known chart that accurately surveyed the port and Dublin Bay with its channels. His map, presented to the Directors General in 1801, also showed the dry part of the North Bull marked as a very small patch. In their own submission to Lord Lieutenant Cornwallis in 1804, the Directors General supported the proposal of the Ballast Board and referred to ‘the degree of accumulation which had already appeared on the north bull since the building of the south pier, so great that a considerable stripe of it remains dry at high water and has on it a growth of marine plants’. This was the small oval patch that Bligh had mapped three years earlier; it had by now become ‘a considerable stripe’. Bligh’s major proposal was for a wall on the north side of the channel—but not in the form that the North Bull Wall takes today.

Bligh pointed out that the depth of water over the bar was greater than the depth at the quay walls, and hence a greater priority was to improve that situation. His proposal was to extend the existing North Wall eastwards into the bay to cut off drifting sands from the river channel, much as the South Wall had done. If the river was confined within walls, the current would also scour the channel and keep it clear. Finally, he suggested an intensive programme of dredging, employing 350 men for the purpose. Bligh’s proposal, however, did not satisfy the administrators in Dublin. The alternative suggestion that a wall should be built from Clontarf, rather than as an extension of the North Wall Quay, was put forward by two members of the Ballast Board, Leland Crosthwaite and George Macquay. This idea had, in fact, been put forward in 1786 by William Chapman, the engineer who had proposed in the previous year that the Grand Canal should be run around the southern margin of the city to join the Liffey at Ringsend.

John Rennie’s proposals

The year after Bligh’s printed report and chart of the bay were published, the eminent Scottish engineer John Rennie was engaged to carry out a report on the harbour and Dublin Bay to investigate, among other things, the proposal for a pier from Clontarf. This was Rennie’s first engagement in the Dublin area, though he went on to have a distinguished record, taking over as engineer on the Royal Canal in 1803, for Howth Harbour in 1809 and Dunleary Harbour in 1815, as well as working on the docks near the Custom House. Rennie’s recommendation to the Inland Navigation Commissioners was threefold. First, he supported the suggestion that a wall be constructed from Clontarf towards Poolbeg, his proposal being to leave a gap of 165m at the Clontarf end. His second proposal was to create a tidal reservoir on the South Bull with an opening into the channel at Ringsend; and his third was to provide jetties at Clontarf. He suggested that it might be necessary to extend the ends of the proposed northern wall and the South Wall eastwards.

The thinking behind Rennie’s first two proposals was to provide two very large bodies of water that would be tidal and that would fill and empty with the tides running through a narrow entrance at Poolbeg. The result would be a strong current at the bar that would scour it away. A further report was submitted by Captain Daniel Corneille, an engineer, who proposed a different alignment of the wall from Clontarf; it would run over a longer distance and would have a curve.

In 1818 the Ballast Board engaged an engineer, Francis Giles, to prepare a plan for a wall to extend from the Clontarf shore to the north spit of the Pool Beg. The map that Giles prepared showed that the island had grown into a spear-shaped spit of land about 5km long. This feature was marked on his map as the ‘Sand Island’, but Giles later referred to it as ‘the Green or Bull Island’. So in a remarkably short time—about eighteen years—a substantial new sand-dune system had started to develop from sand that was washed ashore on what is now Dollymount Strand.

With the building of the North Bull Wall, the bar across the Liffey mouth, then only 2m deep at low tide, began to decrease in size, assisted by a device that raked the surface of the bar on the ebbing tide to loosen its surface. By 1822 the channel had deepened to 2.6m at the lowest tides and by 1856 it was 4m. The sand naturally moved northwards with the clockwise tidal circulation in Dublin Bay. This coincided with the increase in width, length and height of the sand-dunes at the Bull Island.

It is interesting to speculate whether the onshore movement of sand to the North Bull could have been assisted by some exceptional storms in the early years of the nineteenth century. A meteorologist, Richard Kirwan, published a series of papers on the state of the weather in Dublin in the Transactions of the Royal Irish Academy about this time. He recorded, for example, that there were thirteen storms in 1802, seventeen in 1803 and 23 in 1804. By 1805 Kirwan was recording the wind speed, and he gives a breakdown of the number of extreme events recorded in that year as storm, great storm or tempest. This suggests that a period of extremely high winds around this time may have helped move the sand from the beach to begin building the sand-dunes of the Bull Island.

The end for Bligh

In 1806 Bligh was appointed governor of New South Wales in Australia, with orders to clean up the corrupt trade in rum. The unlucky Bligh, however, ran into another rebellion there. He was placed under arrest in 1808 by the New South Wales Corps and removed from his command, an act which the British Foreign Office later declared to be illegal. He died in London in 1817—before the final plan for the Bull Wall had been prepared.

The Bull Wall was subsequently connected to the shoreline by a bridge, and the walk across the wooden bridge became a popular amenity. By 1873 the original wooden structure was beginning to decay, but its proposed demolition was greeted with outrage by the public; the board was persuaded to repair and rebuild the bridge instead. In 1921 the North Bull Island became the first official bird sanctuary in Ireland, and by the 1970s it had been designated a nature reserve in the ownership of Dublin Corporation. It is now recognised as a site of European importance by the EU, and since the 1980s it has also been designated as a UNESCO biosphere reserve. Although Captain Bligh played his part in the history of Dublin Bay, there were many other colourful characters in the story of the Bull Island.

 

Rob Goodbody and Richard Nairn are the authors (along with David Jeffrey) of Dublin Bay: nature and history (Collins Press, 2017).