A geohazards specialist says the mass landslides caused by Monday's 7.5 earthquake in Papua New Guinea pose a risk of destructive floods.
PNG communities at risk of flooding following damning rivers by landslides triggered by 7.5 magnitude earthquake. Photo: Barbara Lokes/OilSearchLtd
Reports of casualties and damage filtering through from the remote affected Highlands region said many of the deaths were caused by landslides.
Due to disrupted telecommunication and transport links, information about the number of deaths remains patchy.
But as many as fifty deaths have been reported across parts of Hela, Southern Highlands and Western provinces.
Aerial footage showed the quake triggered many big landslides which have blocked whole valleys and deformed substantial tracts of hillsides.
Dave Petley, the Pro-Vice-Chancellor (Research and Innovation) at the UK's University of Sheffield, said the risk was that significant volumes of water build up behind dams created by landslides and then spill over.
Video from @planetlabs on Papua New Guinea flooding and serious landslides. pic.twitter.com/vGkSZwv5Y0
— RNZ Pacific (@RNZPacific) March 2, 2018
"Generally speaking the landslide blockage is loose and broken up material. So as the water starts to flow over the top it erodes the landslide away," said Mr Petley.
"The water gets released very very quickly, and it picks up all the debris from landslides, generating what is essentially a huge debris flow that then travels all the way down the river channel and that's really destructive, because the volumes of water can be quite large."
Dave Petley said the challenge for PNG was to urgently establish how many landslide cases posed a potential risk of water overflow, the time scale involved, and who was downstream.
"This is a problem that needs attention. It might well be that although there is the potential to generate significant floods here, in fact the number of people who would be affected is relatively low," he said.
"But it feels to me that that sort of assessment needs to be done fairly urgently."
