1. Three Recent GNS Science Landslide Responses
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Three Recent GNS Science Landslide Responses
Mauri MCSAVENEY
GNS Science (Lower Hutt, New Zealand)

2. We attend all major landslide incidents
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We attend all major landslide incidents
Most relate to the occurrence of very heavy rain
Some relate to large earthquakes
The three that I will discuss had no discernable triggers
Some landslides need no trigger
All the preconditions were met a while ago
They just needed time to occur
They are the least predictable type

3. Landslide risk management
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Landslide risk management
These examples are everyday applications of landslide risk management

4. Some recent GeoNet Landslide responses
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Some recent GeoNet Landslide responses
Totara Reserve
Vampire Peak

5. The Young River landslide
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The Young River landslide
The Geonet Young River Landslide Response Team:
Mauri McSaveney, Chris Massey, Neville Palmer, Vern Manville, Tim Davies & Oliver Korup

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What we know about it
In Mount Aspiring National Park, a headwater tributary of Makarora River and Lake Wanaka
Fell at 4:40 am, 29th August 2007 after 10 days with no rain
Lake took a month to fill with 23 million m3 of water (about 630 mm of runoff)
Began to overflow at about 8 pm on 5 October
We do not know how long the lake will last – the risk of a catastrophic breakout flood has to be managed by the authorities responsible for the area and the rivers

7. North Branch of Young River
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North Branch of Young River

8. This is what fell ICL Landslide Teaching Tools
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This is what fell

9. Very fractured Biotite Schist
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Very fractured Biotite Schist

10. ICL Landslide Teaching Tools　
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To make this

11. ICL Landslide Teaching Tools　
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It fell at this moment, lasting at least a minute, and travelling about a kilometre (60 km/hr)
16:40 25”,
28 August,
2007 (UT)

12. The weather in the area around this time was inferred from rainfall:
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The weather in the area around this time was inferred from rainfall:
Overflow
Damming
Data from Otago Regional Council

13. Risk management Young River access track closed since October 2007
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Risk management
Young River access track closed since October 2007
Helicopter access to south branch of Young River
Foot access reopened in November 2008
What was the quantitative risk of loss of life?
It probably had reduced to below the background risk of loss of life on the Dept of Conservation estate by December 2007.

14. The Vampire Peak landslides
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The Vampire Peak landslides
Simon Cox1 and Simon Allen2
1 GNS Science, Dunedin
2 Geography Dept, Canterbury University

15. Two landslides fell in January 2008 onto one which fell in 2003
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Two landslides fell in January 2008 onto one which fell in 2003

16. Looks to be defect-controlled, but it isn’t
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Looks to be defect-controlled, but it isn’t

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18. The January 2008 ones were recorded on the seismic network
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The January 2008 ones were recorded on the seismic network

19. ICL Landslide Teaching Tools　
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The Immediate Report is at The paper is published in “Landslides” see Cox and Allen (2009)

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21. 2006 Totara Reserve rock fall, Pahongana River
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2006 Totara Reserve rock fall, Pahongana River
The Geonet Response Team:
Mauri McSaveney, Mike Page

22. A familiar scene in New Zealand
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A familiar scene in New Zealand
River scours at foot of cliff at outside of bend
Scours a deep hole that is maintained
Hole is beside a designated and developed camping area
Site is sheltered, sunny in early evening, and one bank is tree-lined
Site is popular for picnics and swimming
Collapse of the cliff is recognised but rare
Eventually, collapse and swimmers will coincide
A recipe for disaster that is unavoidable

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Three children killed when a cliff collapsed into the Pahongina River while they were swimming
Thin 500 m3 slab peeled off

24. ICL Landslide Teaching Tools　
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Slab of about 20 m x 20 m peeled off without warning. There was no time to react.
One survivor
He heard “noises”
He didn’t know what they meant!
Minor leg injury

25. More than enough to kill many people
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More than enough to kill many people
It just fell
4 people were in close proximity
3 were killed
The three were in the water
24-hrs earlier 70 people were here

26. ICL Landslide Teaching Tools　
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The cliff had fallen before – but not often. Only once when there were people to see it!
There are many sites like this
No event trigger
No external sign of impending failure

27. Children were not killed by the rockfall
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Children were not killed by the rockfall
The three dead had almost identical fatal injuries
They all died instantly with no chance of resuscitation
They were all hit by a high-velocity wave of water
The children’s bodies were accelerated very rapidly
Their relatively large heads had too much inertia
An adult would have been killed by the rocks

28. Verdict and risk management
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Verdict and risk management
An unfortunate, but unavoidable accident
It was not the fault of any persons or organisation
Rockfall is known hazard of such sites
People need to be aware that there is risk in swimming in rivers
This is one such risk
It is not the only hazard people face enjoying life