19 December 2016
Big French Creek: a high quality new landslide video
Posted by Dave Petley
Big French Creek: a high quality new landslide video
KRCRTV featured last week a very nice new landslide video of a collapse that occurred on Highway 299W at Big French Creek in California. The landslide happened last Monday (12th December 2017) at about 1 pm. As you will see from the video the road was closed. The video was captured by Kevin Erwin. It is a great catch in that it records the minute or so leading up to the failure, as well as the movement of the large boulder that is located within the weather rock mass. Kevin loaded the video onto Youtube, so it can be sen below:
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The same event was also captured by J2R2J:
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Jack Irving kindly highlighted this video to me. He has identified the location as 40.779, -123.311, which looks like this on Google Maps:
The landslide at Big French Creek via Google Maps
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The presence of work crews suggests that the highway agency were aware that the slope was problematic, and it is clear that the road had been closed prior to the collapse. Latest news from Caltrans is that the road is still closed:
SR 299
[IN THE NORTHERN CALIFORNIA AREA]
IS CLOSED 4.5 MI WEST OF BIG BAR /AT BIG FRENCH CREEK/ (TRINITY CO) 24 HRS
A DAY 7 DAYS A WEEK THRU THE WEEK OF 01/08/17 - MOTORISTS ARE ADVISED TO USE AN
ALTERNATE ROUTE
Renewed problems at Pacifica
Meanwhile Pasi Jokela has kindly highlighted a renewed problem at Pacifica to the south of San Francisco, where coastal erosion is causing increasing problems for a coastal community. Liveleak has a nice drone video of a “sinkhole” that has appeared on the cliff. This is a fill slope located behind a sea wall – it seems on first inspection that the fill has washed out:
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The video also highlights a number of other properties that are at a high level of risk from erosion. NBC Bay Area has a decent report about the problem. I have previously featured the ongoing problems at Pacifica, including another very nice drone video of the site.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
The latest estimates on the Big French Creek slide indicate that 100k+ CY of material has fallen on the roadway since January, and there’s 200k+ CY of unstable material still left on the slope. Removing or mitigating that much material will be difficult, but the contractors and geologist/geotechs out there are probably going to try and get as much of it stabilized while its closed. It won’t be open until january as mentioned, but even then it will be through a detour/bypass constructed away from the catchment area near the river and probably one lane. A permanent solution will be interesting.