21 August 2014

Hiroshima: disastrous landslides with further rainfall warnings in effect

Posted by Dave Petley

Hiroshima landslides

On Wednesday, a suburb of Hiroshima in Japan was struck by a series of catastrophic rainfall-induced landslides, which resulted from a period of prolonged and exceptionally heavy rainfall.  These landslides are reported to have killed 39 people, with as many as a further 43 people reported to be missing.  Sadly, some of the deaths appear to be rescue staff who were overcome by subsequent slides.

From a technical perspective, the best images I have found of these landslides are on the IBT website, which includes this overview of the site:


Reuters via IBT


These landslides appear to be channelised debris/mud flows.  It appears that they have started as small failures along watercourses that have entrained large volumes of material to become highly destructive flows.  It appears that they have mostly consisted of very fine-grained materials, which is consistent with the bedrock geology, which is reportedly weathered granite.

Unfortunately, there is further heavy rainfall forecast for this area, and at the time of writing Robert Speta tweeted the following:

The image shows a line of storms approaching the area:


Whilst it seems unlikely that this rain will cause as much damage in Hiroshima itself, landslide and flood warnings are in force across the region and there have been many evacuations.