15 November 2011

Interesting coastal landslide in San Pedro, California

Posted by Dave Petley

News today of an ongoing landslide affecting San Pedro in California.  This slide, which has developed over the last few weeks, has closed the coast road.  Real concern about the site emerged a couple of weeks ago; since then the problem has become far worse.  At the moment I can’t find a decent still image of the site, but this still from this news report gives an idea of the magnitude of the problem (NB this is definitely not a sinkhole – it is a landslide):

Fortunately, it is only the road and utility lines that are threatened.

The site is well-covered by Google Earth imagery.  This is the most recent perspective view from March this year:

Compare that with an image from two years ago:

There has been a very noticeable loss of material on the right side(from this view) of the landslide, which shows the development of a progressive failure.  I would anticipate that the loss of this buttress has destabilised the remainder of the slope.  Thus, at least on first inspection, this just looks to be a natural failure caused by erosion by the sea.  Where the road is so close to the cliff edge, and materials are weak, this is to be expected.

Repair of such a section would be very expensive and environmentally damaging as a large toe support will be needed, with a large volume of fill behind.  Relocating the road inland looks to be the sensible option, if that is possible.

Any comments from those nearer the scene?  Any better news reports?