The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

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As the heavy rainfall associated with Storm Hilary starts to dissipate, the analysis of the resultant damage across part of the United States has started. One important aspect will be debris flows and mudflows triggered by the rainfall, a well known process, especially when intense precipitation falls in arid areas and/or those that have been affected by wildfires.

Whilst the true picture is not yet clear, there have been a variety of posts to social media with videos of debris flows and mudflows. I thought it would be useful to draw together a compilation.

First up is an impressive debris flow, incorrectly termed a rockslide in the tweet, from Forest Falls in  in San Bernardino County, California, which is to the east of Los Angeles:-

This is debris flow has a very boulder-rich frontal portion, explaining the description as a rockslide. SFGate has an article about this landslide, which has blocked roads.

Meanwhile, in Wrightwood, also in California, there was a rather more fluid debris flow:-

Also in Wrightwood, there was a mudflow in Sheep Creek. It is unclear as to whether this event is related to the one above. Note that the sediments in the channel before the flow hits might suggest that it was not the first event in this catchment:-

In Palm Springs, there was a further interesting debris flow, with a frontal portion that was carrying a very large volume of timber:-

Other reported landslides include:

It is likely that there have been other landslides as well, so please post links to any videos or reports in the comments, if you can. Many US news reports are not available to me in the United Kingdom. It will be interesting to see the true cost of these events in the coming days and beyond.

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