QUESTIONS ARE EMERGING about a report into last month’s Tumbi landslide that has been released by Papua New Guinea’s National Disaster Centre.

Although disaster officials say the report is only an initial assessment, it identifies heavy rainfall as the trigger for the landslide which reports say killed at least 25 people.

“The National Disaster Centre report only briefly mentions the Tumbi quarry, part of which was lost in the landslide that submerged the village directly below,” says Johnny Blades of Radio New Zealand International.

“The limestone quarry had been used by Exxon Mobil for its Liquefied Natural Gas project.

“Dave Petley, a professor of GeoHazard and Risk at Durham University, says the report lacks analysis of the quarry’s role in the landslide.

“He queries the report’s assessment of currently high groundwater levels and liquefaction as factors, saying limestone is not a material that undergoes liquefaction, and that seepage and pools are to be expected in the aftermath of a landslide.

“Meanwhile, the watchdog, LNG Watch, has questioned the collaboration of Exxon representatives and Australian officials in the NDC report.”

Meanwhile Dr-Dave Petley has compared initial landslide reports from the Tumbi Quarry disaster and a landslide in Kaikora, New Zealand in an article written for the American Geophysical Union.

Several people have asked what I mean by a proper landslide investigation with respect to the report on the Tumbi Quarry landslide.  To illustrate, one might compare these two reports:

1. The Tumbi Quarry landslide report, prepared by the National Disaster Center.

2. Report on the landslide that blocked SH 1 and the railway line near Rosy Morn Stream south of Kaikoura on 10 September 2010, prepared by GNS Science as part of the Geonet programme.

The GNS report is not long, and nor is it highly detailed.  However, it is throrough, it investiogates and describes the landslide properly, and it allows evidence-based conclusions to be drawn about he landslide and its triggers and causes.

This should be the minimum level of report for a major landslide event. Of course, in New Zealand (or indeed the UK) a landslide that killed 25 or more people would probably be investigated

Dr Dave Petley is the Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom.