6 July 2020

Ashikita: a large landslide in the Kumamoto region of Japan

Posted by Dave Petley

Ashikita: a large landslide in the Kumamoto region of Japan

Japan has once again suffered from exceptional rainfall in recent days, with the Kumamoto region of the island of Kyushu bearing the brunt.  Landslides and flooding have occurred across a wide area.  Further rainfall was forecast for Sunday evening.  There is a good Wikipedia providing some details about this rainfall event. It reports peak rainfall intensities of about 100 mm per hour.

At Ashikita in Kumamoto Prefecture a large landslide occurred on a steep, forested mountain slope. Teller report has a good overview image of the landslide:-

Ashikita landslide

The landslide at Ashikita in Kumamoto, Japan. Image from Teller Report, taken from a video filmed by the NHK helicopter.

.

Whilst there is a good drone video of the landslide on Youtube, posted by Ruptly:

.

This landslide reportedly occurred at 11:40 on 4 July 2020.  When large landslides occur there is often a default view that human modification of the landscape, especially the removal of trees, is the cause (and often this is the case).  This landslide appears to demonstrate that, as all landslide researchers know, failures are a natural process that can occur on undisturbed forested slopes.

.

Quickslide 1: An update on the Myanmar jade mine landslide

Loss of life from the landslide at a jade mine in Kachin State has reached 174 people, with a further 54 people reported to have been injured.  An investigation of the landslide is apparently underway.  Interestingly, the State Counsellor (equivalent to Prime Minister) Aung San Suu Kyi has blamed the disaster on joblessness, which forces people to scavenge for jade on the soil tips.

.

Quickslide 2: a dramatic rockslide in Idaho

A large and dramatic rockslide occurred on 3 July on US route 95 at Sheep Creek near to Riggins in Idaho. Yahoo News has a video of the incident. The road remains closed, and there is concern about further potential instability on the rockslope as a large crack has developed.