Three Recent GNS Science Landslide Responses ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (1) Three Recent GNS Science Landslide Responses Mauri MCSAVENEY GNS Science (Lower Hutt, New Zealand) e-mail: m.mcsaveney@gns.cri.nz

We attend all major landslide incidents ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (2) 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

Landslide risk management ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (3) Landslide risk management These examples are everyday applications of landslide risk management

Some recent GeoNet Landslide responses ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (4) Some recent GeoNet Landslide responses Totara Reserve Vampire Peak

The Young River landslide ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (5) The Young River landslide The Geonet Young River Landslide Response Team: Mauri McSaveney, Chris Massey, Neville Palmer, Vern Manville, Tim Davies & Oliver Korup

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (6) 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

North Branch of Young River ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (7) North Branch of Young River

This is what fell ICL Landslide Teaching Tools PPT-tool 4.064-1.4 (b) (8) This is what fell

Very fractured Biotite Schist ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (9) Very fractured Biotite Schist

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (10) To make this

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (11) 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)

The weather in the area around this time was inferred from rainfall: ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (12) The weather in the area around this time was inferred from rainfall: Overflow Damming Data from Otago Regional Council

Risk management Young River access track closed since October 2007 ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (13) 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.

The Vampire Peak landslides ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (14) The Vampire Peak landslides Simon Cox1 and Simon Allen2 1 GNS Science, Dunedin 2 Geography Dept, Canterbury University

Two landslides fell in January 2008 onto one which fell in 2003 ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (15) Two landslides fell in January 2008 onto one which fell in 2003

Looks to be defect-controlled, but it isn’t ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (16) Looks to be defect-controlled, but it isn’t

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (17)

The January 2008 ones were recorded on the seismic network ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (18) The January 2008 ones were recorded on the seismic network

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (19) The Immediate Report is at www.geonet.co.nz The paper is published in “Landslides” see Cox and Allen (2009)

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (20)

2006 Totara Reserve rock fall, Pahongana River ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (21) 2006 Totara Reserve rock fall, Pahongana River The Geonet Response Team: Mauri McSaveney, Mike Page

A familiar scene in New Zealand ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (22) 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

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (23) Three children killed when a cliff collapsed into the Pahongina River while they were swimming Thin 500 m3 slab peeled off

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (24) 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

More than enough to kill many people ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (25) 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

ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (26) 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

Children were not killed by the rockfall ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (27) 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

Verdict and risk management ICL Landslide Teaching Tools　 PPT-tool 4.064-1.4 (b) (28) 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