27 March 2023
Novato: an interesting landslide triggered by heavy rainfall in California
Posted by Dave Petley
Novato: an interesting landslide triggered by heavy rainfall in California
Last week, the latest in a long series of large storms struck California, triggering another round of flooding and landslides. One particularly interesting slope failure occurred at Novato in Marin County. The San Francisco Chronicle has a nice image of the aftermath:-
The aftermath of the landslide in Novato, California. Image from the San Francisco Chronicle.
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A Tweet by Sarah Klieves, a senior producer for NBC Bay Area, provides the best perspective though:-
Our @nbcbayarea SkyRanger flew over a landslide that crumpled a section of Redwood Blvd near Olompali State Historic Park. This is the only public road into the park, so rangers say it will be closed for awhile. pic.twitter.com/saQqDMff9d
— Sarah Klieves (@sarah_klieves) March 24, 2023
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This is a view from that video, showing the landslide:-
The landslide at Novato, California. Image from a Tweet by Sarah Klieves of NBC Bay Area.
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The location of the landslide appears to be [38.1444, -122.5652]:-
Google Earth image of the site of the landslide at Novato, California.
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Interestingly, Redwood Boulevard, which is the road damaged by the landslide, was constructed in 2015. A Google Earth image from March that year shows that the slope at the site of the landslide was cut and reprofiled, and that drains were installed:-
Google Earth image of the site of the landslide at Novato, California in March 2015, showing engineering works underway at the site.
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It is interesting that at this site the slope is a little steeper than in the adjacent areas, which presumably is the reason for the additional works, including the drains. That failure is a classic slump. Fortunately the toe has not extended to the main highway, and the limited mobility of the debris has meant that this road is unaffected. However, the landslide has caused disruption to a watermain and to a gas pipeline.
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.
Repairs of this magnitude and cost should contain a commensurate monitoring component and budget allotment. Noting repairs as at-risk sites for future displacement should be well noted. Particularly in CA.
In the video and the still it looks as if there is a pipe that runs along the upper part of the headscarp. If it is indeed a pipe is it part of the drainage system you mentioned?
Do you think this slump is more translational, along a bedding plane, or rotational, cutting across softer material?
DRS Engineering Inc based in Southern California specializes in the design of landslide remediation systems.
We are always available to add our expertise to assist in dealing with these increasingly frequent issues.
This is on the eastern portion of Burdell Mtn, part of Franciscan Complex and prone to sliding. Although not in this location, there were other slides to the south that impacted a nearby residential development. The Buck Center took a hard look at the siting of their facility as their were mine workings further up the slope. A few of my geologist colleagues at Harding Lawson Associates in the 1980s (when their headquarters was at San Marin and Redwood Blvd) did some mapping and slope evaluations of Burdell Mtn. Also worked a reroute of MMWD 36-in pipeline reroute south of this landside. Not sure what the pipeline along the scarp is but I agree classic slump movement
Looking at the photo of the head scarp and Google Earth time-series aerial photos, I’m thinking there is a pipeline exposed in the head scarp. How about white PVC, about a foot in diameter, a water pipe? In the 4 and 6/2013 GE photos the squiggly road was made by pipeline installation? The squiggly road is seen, parallel to US-101, for few miles north and south of the landslide. The pipeline trench coincidentally controls the head scarp? The pipeline trench would not cause the landslide, unless the pipe leaked, but if it is a water pipe and breaks at the scarp, would exacerbate the landslide.
Here is the National Weather Service climate plot for Santa Rosa, California, 20 miles north of the Novato landslide site. Cumulative precipitation for water year October 2022 – September 2023:
https://www.weather.gov/images/mtr/cliplot/KSTS2022b10plot.png
Prior years and more stations here: https://www.weather.gov/mtr/cliplot
Repairs of this magnitude and cost should contain a commensurate monitoring component and budget allotment. Noting repairs as at-risk sites for future displacement should be well noted. Particularly in CA.
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