18 January 2009

Landslide in Lombok, Indonesia

Posted by Dave Petley

The Jakarta Globe is today reporting a quite large landslide at Buwun Mas village in West Nusa Tenggara Province. This slide is reported to have killed at least four people, with a further 11 potential victims believed to be buried in the debris. The report is quite interesting as it says that:

The area, [Rustam Pakaya, the head of the Ministry of Health’s Crisis Center] said, is used for illegal gold mining. “We are still searching for the missing people,” Rustam said. “We don’t have any information yet on who these victims are. We don’t know if they are miners or not.”

It should be said that other, unfortunately non-local, reports are rather more certain about the mining issue:

A landslide at a gold mine killed four workers and left 11 missing on the Indonesian island of Lombok, a Health Ministry official said Sunday.”

Fortunately, this is an area with excellent Google Earth imagery, so a quick look at the site of the landslide shows the following (click on the image for a better view in a new window):

The area around the village appears to be quote densely forested, but note that the Google Earth data covers the junction between two epochs (periods) of imagery, which you can see from the colour change across the image above. I have shown this below:

Note how to the west of the line (north is approximately at the top of the image) the forest cover is quite intact, but to east it is mainly denuded. The junction is along the line that I have marked above. This presumably means that the imagery to the west is older and was taken when the forest was mostly intact, whilst to the east the images are more recent. In the meantime there has been extensive deforestation. Unfortunately, the consequences are all to clear to see – to the east of the line the ground is visibly eroded. Just a couple of kilometres from the village there is an area of extensive recent shallow landslides:

A perspective view shows that these are breaking out all over the deforested landscape:

Given that this is an area of illegal mining and extensive deforestation, the occurrence of destructive landslides should not be a surprise. The level of vulnerability here is indicated by the fact that the Tropical Rainfall Measuring Mission have not detected unusually high levels of rainfall in this area over the last few days.

The combination of deforestation and mining in tropical environments is really bad news from a landslide perspective.