3 September 2009

The Hsiaolin landslide slope before failure

Posted by Dave Petley

In an earlier post I highlighted a satellite image of the Hsiaolin landslide site. I have trimmed this a little below:

This image is rather helpful as it starts to allow the site of the landslide before failure to be examined using Google Earth, which has good quality imagery of this area. This is, as close as I can get it, the same slope prior to failure:

Click on the image for a better view in a new window.

There are a couple of things to note here. First, the slide ran out straight across the village, removing all trace as the earlier photographs showed. Second, the rivers clearly underwent huge amounts of flooding.

A perspective view of the site is a little more helpful:

I have annotated the image below to locate the approximate boundaries of the landslide, using the satellite image above plus the photographs of the site that are now available (see this post)

You may need to click on the image to be able to see the boundaries properly. These boundaries are at the moment very much indicative, but they give the general idea. The landslide is intriguing because the slope was not showing obvious signs of instability as far as I can see, bar a depression in the head scarp area the could be a tension crack? The river has clearly undercut the toe of the slope, which could have been a factor? It would be interesting to know more about the underlying bedrock, and in particular the dip direction. Can anyone provide any more information?

Comments welcome.