And another photo, slightly different angle, with houses in the foreground.
http://www.nytimes.com/2014/03/24/us/washington-mudslide.html
In addition to the people who were in harm’s way, there were cattle in this area, and of course all the wildlife.
One man was driving behind another vehicle that was driving (annoyingly) slow. The man said if not for that slow driver, he would have been swept away, because it happened right in front of both of their vehicles.
Sometimes it’s a blessing to be delayed by a slow driver.