29 March 2020

Kanagawa prefecture: the tragic landslide experiment in 1971 that resulted in 15 deaths

Posted by Dave Petley

Kanagawa prefecture: the tragic landslide experiment in 1971 that resulted in 15 deaths

In 1971, The Science and Technology Agency of Japan undertook an experiment to explore the mechanisms of landslides, which of course are a very significant hazard in that country. The experiment consisted of the irrigation of a 20 metre long slope in order to trigger failure, located near to the city of Kawasaki.  The aim was to capture the failure event, providing insight into processes and mechanisms of failure.

To witness this high-profile experiment, a news crew joined officials and scientists to watch the failure at the toe of the slope.  Sadly, the failure that was triggered was both larger and more mobile than had been anticipated.  The landslide mass overwhelmed the observers, burying them in the debris.  There is a New York Times article about the landslide – it reports that 15 people were killed and another nine were seriously injured.

Loyal reader Alasdair pointed out to me that there is a remarkable video of the 1971 Kanagawa Prefecture event on the British Pathe News website.   Astonishingly, the video captures the debris rushing down the slope towards the observers:-

The 1971 Kanagawa prefecture landslide disaster

British Pathe image of The 1971 Kanagawa prefecture landslide disaster. Still from the video by British Pathe.


Shortly after the video was captured the cameraman and the camera were buried by the landslide debris.  Fortunately he survived and the film was recovered.

This was a true tragedy, showing how poorly understood landslides were at the time.  Since then, there have been many landslide experiments using flumes, artificial slopes and, for example at Selborne and Ruedlingen, the induced failure of slopes in natural materials.  Exquisite care is now taken to ensure that people are not located at the toe of the slope, or close to it, when the failure is initiated. A great deal has been learnt from these experiments.