4/7/15: LANDSLIDES IN CA

Landslides impact California’s terrain often. These are generally related to precipitation patterns, in particular if there has been previous months of drought conditions. In 1982, a series of landslides near San Francisco killed 33 people and closed the Golden Gate Bridge. A total of 18,000 different landslides took place in the San Francisco Bay Area following a very heavy rain storm (data collected by aerial surveillance in the days following the event). Two fast-moving fronts carrying extremely heavy rain passed through in a 36-hour period, during which the area received an amount of rain equal to half its average annual precipitation. 

Another famous unstable area is La Conchita. A mudslide of 400,000 tons of mud in 2005 killed 10 people. This should not be surprising as the exact same place suffered another hill collapse in 1995, destroying 9 homes. See topographic map on the right that shows both sites. Note where we build our houses..

The obvious approach is study well the soil in where we put homes and also learn from previous occurrences, understanding that areas that are unstable will continue being so  (La Conchita is not alone; Oso area had been unstable before the 2014 event).  Detailed geologic reports have been made in the past of these places, but the personnel that has the power to act have not followed up/ignored them or have not read them.

Gravity always wins. We know better?

After the 2005 disaster, there was an attempt of a $50-million grading project. There were also calls for the county to buy up all the homes through eminent domain and never allow anyone to live there again. It was an idea that came and went, as was the grading project.

Here is the USGS page with information on how to identify landslides and what to do if one happens.

[http://www.history.com/this-day-in-history/landslides-kill-33-in-california; http://www.usgs.gov/blogs/features/usgs_top_story/rain-and-landslides-in-california/; http://www.latimes.com/local/california/la-me-la-conchita-20150104-story.html#page=1; http://pubs.usgs.gov/of/2005/1067/508of05-1067.html]