15 February 2019

Sausalito: a mudslide damages houses in California

Posted by Dave Petley

Sausalito: a mudslide damages houses in California

Heavy rain in California, brought by an atmospheric river event, triggered a significant mudslide in Sausalito yesterday.  ABC7 News has a report on the incident:-

“At least 50 homes remain evacuated after a massive mudslide struck a neighborhood in Sausalito on Crescent Avenue and Sausalito Boulevard.  One of the homes on Crescent Avenue slid into a home on Sausalito Boulevard. A woman was inside the home that slid. She was taken to the hospital and has been released. The other home was not occupied at the time.  When firefighters first arrived they evacuated the 50 homes over concerns that the hill could continue to give. Officials were also concerned that a gas line had ruptured and power lines were down.”

The image below shows the aftermath of the landslide.  In Hong Kong the initial event would be classed as an open hillslope failure, with the debris transitioning into a channelised flow.  There are reports that this slope has suffered failures previously:-


The aftermath of the mudslide in Sausalito on 14th February 2019. Image from ABC7 News.


ABC7 News also has a drone video of the aftermath of the landslide. The site of the mudslide in Sausalito is shown in the Google Earth image below:-

Sausalito mudslide

Google Earth imagery of the site of the mudslide in Sausalito on 14th February 2019


Note the smaller landslide scar above the road; this was not the site of the failure on this occasion.

The steeper slopes of California have a long track record of landslides, resulting from the combination of the topography built from active tectonic processes, the geological materials and the occurrence of both heavy rainfall events and earthquakes. It remains a surprise to see the number of houses that are built in geomorphologically-active areas, such as channels. It is unsurprising that there is frequent landslide damage in these areas during heavy rainfall.