The recent damage of the sea wall at St Clair Esplanade is a pertinent reminder of the power and ferocity of the ocean and the continuation of an issue that has been prominent in Dunedin since the beginnings of colonial settlement. The extension of physical occupation of coastal areas by people and the development of infrastructure around that occupation has been fraught with problems. Worse still has been the undermining of the important protection afforded to the city by the St Clair and St Kilda beach areas.
The first sea wall built at St Clair was in the early 1870’s and appears to have been privately built, eventually being transferred to the ownership of the Caversham Borough Council. In 1885 the wall was badly damaged during a period of high seas and the Caversham Borough Council began rebuilding the wall in 1888. As with today there was considerable debate over the merits of the construction by amateur and professional engineers alike. So problematic was the rebuilding of the wall that the Minister of Public Works inspected the works himself. The Caversham Mayor Mr Bragg appears to have had a hand in the design and construction supervision himself which was described as “a sloping bank, terminating in a wall six feet wide at the base, which is sunk in the hard sand to the depth of five feet, being quite four feet lower than the foundation of the old wall. This wall has a facing of very large and weighty stones on both sides. The centre built up of smaller ones tightly wedged and closed in with rubble. At the foot of the embankment this solid wall is backed up with rotten reef, which gives the whole structure great solidity.”
However that solidity did not last and by 1890 it was reported that the 630 feet wall built for £800 ” has all but been demolished by the sea, with the exception of 80 feet at its west, and even this portion is considerably disturbed and undermined.”Several design flaws were reported by marine engineer CY O’Connor , notably that it had been placed too far out to sea and that its foundations were “too low.” Worse was to come, when in 1891 a significant storm did considerable damage to the whole Ocean Beach area. Further storms occurred in May 1898 when the dunes themselves were breached and there was 3 feet of water in Larkworthy Street. By May 11th 1898 much of St Kilda between Ocean Beach and Cargill’s Road were inundated and houses could only be accessed by wading through water. In July 1898 the sea breached the dunes again and St Kilda was saturated with the Pacific Ocean.
Public acrimony and outrage was vitriolic and both the Otago Daily Times and Otago Witness were inundated with letters between 1890-1900 regarding the erosion and management of the Esplanade and Ocean Beach Domain. One of the central problems lay in determining the responsibility for management of the issues between the various local councils and central government. A deputation by Mayor and Councillors of Caversham Borough Council to the Minister of Public Works in 1890 requesting government assistance was made. Caversham was particularly concerned at the level of borrowing it had been forced to undertake in dealing with the Esplanade issues. In 1891 Richard Seddon also visited the area and if the Caversham Borough Councillors were hoping for government assistance they were to be sadly disappointed. Seddon told the deputation “If you think for a moment that this Government are going in for extravagant expenditure, all I can say is that you will be disappointed. We are going to govern this country on commercial lines, and be very careful of the people’s cash.”
The passing of the Ocean Beach Public Domain Act in 1892 provided for the protection and conservation of the area known as the “sand hills”. However, this was a period of deep public acrimony and recrimination and coupled with a lack of funding was largely ineffectual. In 1894 the Board were allowed to raise funding through levying rates of a halfpenny in the pound for rateable properties in all of the city’s boroughs. However, there was catch, and the rates could only be levied by a public referendum. The Ocean Beach Domain Board largely took extensive steps to re-vegetate the sand dunes and construct sand trap fences to repair the dune barrier and protect the city. However, the problematic issue of the St Kilda Esplanade remained.
By 1910-1911 both the Domain Board and the City Council had received advice on options for the reconstruction of the esplanade. The Domain Board had not been able to reconstruct the esplanade because of a shortage of funds and had been too afraid to levy higher rates on ratepayers in fear of the reception they would have received, However, the Dunedin city Council received £1000 from the government to proceed with reconstruction and utilised a further £1000 from the Tramways Department and £1000 from the municipal account. The rebuilt esplanade was officially opened in 1913 and the construction was described as having “333 reinforced’ concrete piles 2ft wide, 44 piles 1 ft wide, and 36 anchor piles—a total of 413 piles, and if these were placed end to end they would stretch one mile and a-half. After being sunk and. driven into the solid they were driven further by an electric pile-driver. The length of the piles was from 18ft to 24ft, and they were driven to a depth of from 9ft to 19ft. The wall was anchored every 10ft with 1 inch rods 35ft long, cased in mortar to prevent rusting. Safety was assured first by the position of the work being beyond mean high-water mark, and any waves that reached it would be broken and rendered harmless by means of an apron of loose rock, more of which had yet to be placed in position. The length of the esplanade was 10 chains (200 metres) and its width 50ft, with footpaths on the land and sea sides.”
In 1914 almost all of the sand immediately in front of the wall at St Clair beach disappeared and this was repeated to a greater extent in 1919, 1935, 1939 into the high erosional period of the 1990’s. Erosion of the beach and the dunes has become a regular historical and present day feature of both the beach and dunes immediately east of the wall. This has largely been due to the “end wall effects” where once waves reach the wall it “bounces” off them with more energy than a wave washing back off a normal sand beach. More sand is carried off shore, promoting beach loss. Seawalls, harden the coast and reduce its ability to adjust naturally exacerbating erosional problems by reflecting and concentrating wave energy and erosion.
Dunedin’s various local authorities have struggled for the last 140 years to manage the coastal issues at St Clair and St Kilda. Sadly, it is a historical record of failure to understand the natural processes of the dune and coastal environment that affects the coastline that we perilously live beside. Perhaps this latest failure is an opportunity to rectify that understanding and restore the coastal environment to ensure its long term functionality as an ecological asset that provides both protection and pleasure for our city. The problems with the wall and the wider erosion issues of Ocean Beach Domain cannot be dealt with in isolation, but must be integrated into a programme that deals with the coastal environment as a living entity rather than as an engineered solution. That may also mean making changes to our thinking and use of this area in the long term. History has shown our failures let’s hope that we don’t continue that trend.