![Abbotsfield landslip](https://upload.wikimedia.org/wikipedia/commons/7/78/Abbotsfield_landslip.jpg)
On 8 August 1979, a major
landslip
Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, ...
occurred in the
Dunedin
Dunedin ( ; mi, Ōtepoti) is the second-largest city in the South Island of New Zealand (after Christchurch), and the principal city of the Otago region. Its name comes from , the Scottish Gaelic name for Edinburgh, the capital of Scotland. Th ...
, New Zealand suburb of
Abbotsford. It was the largest landslide in a built-up area in New Zealand's history, resulting in the destruction of 69 houses – around one sixth of the suburb – but no fatalities.
["New Zealand disasters"](_blank)
Christchurch City Libraries website. Retrieved 1 October 2009.
Geography
The suburb of Abbotsford sits on the slopes of a hill in the southwest of Dunedin, separated from the main urban area by open semi-rural land. The larger suburb of
Green Island sits on gentler slopes immediately to the south. Between the two lies the valley of the
Kaikorai Stream
The Kaikorai Stream is a short river which runs through the city of Dunedin, in New Zealand's South Island.
Course
The stream drains the south eastern and eastern slopes of Flagstaff, Kaikorai Hill and the Balmacewen area, flows through Kai ...
and its tributary, Miller Stream. At the time of the slippage, Abbotsford was within Green Island Borough.
Much of the northeastern end of Abbotsford's residential area was built on unstable ground.
Schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes o ...
bedrock is covered with a thick layer of
mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...
, with a top coating of sand and clay-rich
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
alluvial soil. This type of surface becomes slick during even moderate rainfall.
["Abbotsford Landslide"](_blank)
Retrieved 1 October 2009. Landslides of this type of material have been relatively widespread within the Greater Dunedin area throughout both recent prehistory and historical times.
[Bishop, D.G., and Turnbull, I.M. (compilers) (1996). ''Geology of the Dunedin Area''. Lower Hutt, NZ: Institute of Geological & Nuclear Sciences. . p. 33.]
The land was also sloping, and quarrying and the construction of the nearby
Dunedin Southern Motorway
The Dunedin Southern Motorway is the main arterial route south from the South Island city of Dunedin, part of New Zealand's State Highway 1. Despite its name, only a portion of the route is officially classified as motorway. The route is the so ...
during the 1960s and early 1970s may have further affected the land's stability. The event was non-seismic, the increased rainfall over the previous decade was the trigger and the slope gave way due to the clay seams that formed parallel to bedding. The clay seams formed due to flexural slip.
Background
There have been numerous smaller historical slips at Abbotsford, notably during the construction of the Dunedin-
Mosgiel
Mosgiel (Māori: ''Te Konika o te Matamata'') is an urban satellite of Dunedin in Otago, New Zealand, fifteen kilometres west of the city's centre. Since the re-organisation of New Zealand local government in 1989 it has been inside the Dunedin ...
rail line in 1914. Despite this and a 1951
University of Otago
, image_name = University of Otago Registry Building2.jpg
, image_size =
, caption = University clock tower
, motto = la, Sapere aude
, mottoeng = Dare to be wise
, established = 1869; 152 years ago
, type = Public research collegiate u ...
report which stated that the land was unsuitable for building , the area was chosen as viable for residential
subdivision
Subdivision may refer to:
Arts and entertainment
* Subdivision (metre), in music
* ''Subdivision'' (film), 2009
* "Subdivision", an episode of ''Prison Break'' (season 2)
* ''Subdivisions'' (EP), by Sinch, 2005
* "Subdivisions" (song), by Rus ...
. During subdivision, extra watercourses were built to handle excess rain runoff, but these proved insufficient to handle heavy downfalls.
Christie Street, which runs up Abbotsford hill in the east of the suburb had existed before World War II, but the subdivision of land around it began in earnest only from 1953.
[Stuart, I. A. (1979) ''Landslide! The Abbotsford disaster.'' Dunedin: Allied Press.]
Several houses needed to be demolished because of slippage caused during the construction of the
Dunedin Southern Motorway
The Dunedin Southern Motorway is the main arterial route south from the South Island city of Dunedin, part of New Zealand's State Highway 1. Despite its name, only a portion of the route is officially classified as motorway. The route is the so ...
in 1966 and 1968.
From 1968, cracks started appearing in houses in Christie Street, with evidence of subsidence and earth movement becoming more common in the following years. In November 1978, water mains ruptured in Christie Street, and in May 1979 the
Green Island Borough Council had to replace drains which had separated by as much as . This was followed by further breaks in both water and sewerage pipes during June.
Between 1 July and 16 July, four houses were evacuated; six more were to become empty before the end of the month. During July,
Cabinet
Cabinet or The Cabinet may refer to:
Furniture
* Cabinetry, a box-shaped piece of furniture with doors and/or drawers
* Display cabinet, a piece of furniture with one or more transparent glass sheets or transparent polycarbonate sheets
* Filing ...
ministers
Bill Young
Charles William Young (December 16, 1930 – October 18, 2013) was an American politician who served in the United States House of Representatives from 1971 until his death in 2013. A Republican from Florida, Young served as chairman of the H ...
and
Derek Quigley
Derek Francis Quigley (born 31 January 1932) is a New Zealand former politician. He was a prominent member of the National Party during the late 1970s and early 1980s, and was known for his support of free market economics and trade liberalisa ...
visited the area, but Prime Minister
Robert Muldoon
Sir Robert David Muldoon (; 25 September 19215 August 1992) was a New Zealand politician who served as the 31st Prime Minister of New Zealand, from 1975 to 1984, while leader of the National Party.
Serving as a corporal and sergeant in th ...
refused to call a state of
civil emergency
Civil may refer to:
* Civic virtue, or civility
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*Civil engineering
* Civil (journalism), a platform for independent journalism
*Civilian, someone not a m ...
or allow the
Earthquake and War Damage Commission to pay full compensation on damaged or destroyed houses.
By mid-July, the land was moving at close to per day. The chance of a major slip was discussed, but it was felt that there would be considerable warning before this happened, and as such residents were not officially evacuated (although several left their homes of their own volition). Heavy rain during late July led to an increase in the rate of slippage, and non-residents were barred from visiting the area. By early August the rate of slippage had increased to over per day. More houses were evacuated during this time. At the instigation of
Green Island mayor
Vic Crimp, a state of civil emergency was finally declared starting at 8 am on 6 August
and the area was partially evacuated. Plans were drawn up on 7 August for the complete evacuation of the area, though this had not been completed by the time the slip occurred.
The hill gives way
At around 9.07 pm on 8 August, Abbotsford hill gave way. In all, some of land – nearly half of it residential – moved a distance of down the hill in a mere 15 minutes. This land included most of the eastern side of Christie Street, most parts of Mitchell and Edward Streets east of Christie Street, the short Gordon Street, and the
cul-de-sac
A dead end, also known as a cul-de-sac (, from French for 'bag-bottom'), no through road or no exit road, is a street with only one inlet or outlet.
The term "dead end" is understood in all varieties of English, but the official terminology ...
, Charles Street. A large area of open land belonging to the Orchard Sun Club was also part of the slip. Sixty-nine houses were destroyed, either directly in the slip or later for safety reasons. At the foot of the hill, much of Miller Park sports ground and neighbouring Armstrong Lane were inundated.
The slip involved some of sand and
colluvium
Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combinatio ...
up to in thickness. A wide rift up to in depth was left at the head of the slip.
[Civil Defence report](_blank)
/ref>
Hundreds of people were left homeless, though – largely through good luck – there were no deaths and the worst injuries were very minor.[Healey, Kathleen. (1990) ''The Green and the Gold, Vol. II: The story of greater Green Island, 1970–1989.'' Dunedin: Green Island Borough Council. pp. 25–32. .] Some residents only had seconds to leave their homes, and a group of seventeen residents had to be rescued from a small moving island of solid land.
Aftermath
The state of civil emergency continued until 18 August. Total damage was estimated at $NZ 10–13 million,. Some houses survived the slide relatively intact and were moved to new locations. A Commission of Inquiry into the reasons for the slip sat for 58 days and produced its report in November 1980. The Commission concluded that the area had a geological predisposition to slippage, with potentially unstable weak clay layers, rich in montmorillonite
Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite gro ...
clay. The situation was aggravated by the removal of sand from the toe of the hill at a quarry (Harrison's Pit) and during construction of both the residential area and motorway. Though not directly referred to in the Commission's findings, it is possible that a minor earthquake in the area in 1974 also contributed to the slide.
The landslip led to changes in building and subdivision practices in New Zealand, with geological assessment of the land now common prior to the approval of any land development.Proceedings Sixth International Congress, International Association of Engineering Geology, 6–10 August 1990, Amsterdam, Netherlands
, (Google Books – retrieved 1 October 2009) Land cover and landslip insurance regulations were also substantially rewritten in 1984 as a direct result of the Abbotsford landslip.
Much of the land which suffered slippage has since been landscaped into parkland, with stands of trees added to help stabilise the earth. The slip site now hosts rugby grounds and a
paintball
Paintball is a competitive team shooting sport in which players eliminate opponents from play by hitting them with spherical dye-filled gelatin capsules called paintballs that break upon impact. Paintballs are usually shot using low-energy ai ...
venue.
References
;Notes
"30 years ago::Abbotsford landslip(photo gallery), ''Otago Daily Times'', 8 August 2009. Retrieved 1 October 2009.
"Abbotsford landslide" photograph of the affected area. Te Ara Encyclopedia of New Zealand, retrieved 1 October 2009.
{{DEFAULTSORT:Abbotsford Landslip
History of Dunedin
Abbotsford landslip
On 8 August 1979, a major landslip occurred in the Dunedin, New Zealand suburb of Abbotsford. It was the largest landslide in a built-up area in New Zealand's history, resulting in the destruction of 69 houses – around one sixth of the suburb ...
Abbotsford landslip
On 8 August 1979, a major landslip occurred in the Dunedin, New Zealand suburb of Abbotsford. It was the largest landslide in a built-up area in New Zealand's history, resulting in the destruction of 69 houses – around one sixth of the suburb ...
1970s in Dunedin
1979 disasters in New Zealand