It’s a rockier road than usual in the Santa Clarita valley

Vasquez Canyon Road in Santa Clarita, California has undergone a dramatic change in just a few hours. The 3-km stretch between Lost Creek Road and Vasquez Way, Santa Clarita Valley’s few east-west connectors, is closed until further notice. But it is providing a learning experience for geology students.

There was no earthquake, rain or other weather event that appeared to trigger this sudden destruction of the roadway. Engineers are investigating the cause which is suspected to be related to a slow mass movement of soil under the road (called mass wasting in geologic terminology), which can be thought of as a progressive landslide. The Landslide Blog by Dave Petley at the University of East Anglia, U.K. provides us some expert commentary on the roadway. Using past imagery from Google Earth, Dr. Petley noted signs of instability of the roadway appeared several months ago:

There are clearly some signs of instability in this image, and note the other landslides in the image. The section of road that has failed is in a box cut, so it would appear that unloading of the slope may be a key factor in the landslide. And interestingly, this imagery from two years ago (May 2013) suggests significant movement at that time as well.

Cracks in the roadway were noticed in 2011. Dr. Petley concludes that this event has been going on, albeit slowly, for a while, perhaps since the road was first built.

Google street view from 2011.

Google street view from 2011.

The dramatic destruction did appear rather quickly on November 19. Here is a tweet from Los Angeles Public Works Department:

The movement continued into the night. Local geological experts say the subsurface material here is permeable so water could have been a factor. But I checked weather records for November in Santa Clarita. There was only slight precipitation on November 2 (0.05 in) and November 15 (0.02 in).

Drone footage shows the extent of the damage and the

This portion of the road was created by cutting into the slope and depositing that material on the downslope. It’s a common method but it can be problematic if done on a slope that is inherently unstable. Officials have characterized it as “essentially a catastrophic failure”. The road will have to be completely rebuilt in this stretch. Let’s hope they take into account the potential instability THIS time. Such events highlight the importance of complete geologic assessment of an area prior to disturbance. But, it’s not always clear what will happen when the landscape is re-sculpted by humans. Nature sometimes reclaims itself.

From KTLA 5 News.

From KTLA 5 News.

Yes, the references to Tremors (giant worms and Kevin Bacon) are following fast and furious from the news.

Even though the road is fenced off, the curious sightseers are visiting and skateboarders have accepted the challenge.

  5 comments for “It’s a rockier road than usual in the Santa Clarita valley

  1. Hiram
    November 28, 2015 at 2:08 AM

    I must say, I had taken for granted the idea that complete geological assessments are made before construction of roads in geologically sensitive areas like these. This is the umpteenth time I am admonishing myself for having made such a mistake. At least, periodic surveys should be made to keep an account of road health in areas where mass movement of material underlying the road is quite probable. But this how you learn, I guess. At least the skateboarders seem to love the learning curve.

  2. November 28, 2015 at 2:05 PM

    Yes. Don’t assume. I will add one observation that may or may not apply to this situation but I, as a geologist who has worked with highway engineers before, conclude engineers and geologists think COMPLETELY differently. While a geologist will note “this could be a serious problem”, engineers will respond, “She just said ‘could be’ so we can engineer our way around that problem” instead of thinking about what happens long-term.

  3. Blargh
    November 28, 2015 at 9:30 PM

    But this is a hazard that is considered before starting construction?

    Being totally outside that field, I have no idea what is actually assessed before building a road. Are geologists always consulted? What kind of hazards do you have to consider?

    (All I know is that locally, the city engineers have yet to acknowledge that winter is a thing that happens every year, and so every re-asphalting lasts approximately 4 months…)

  4. Bonnie
    November 29, 2015 at 3:29 PM

    The problem may be when politicians outnumber the engineers. Some years back the county I used to live in wanted to place a landfill in a hilly area. Many old-timers pointed out there was a history of landslides, but the politicians kept saying “no problem – don’t worry about it.” Voters insisted that a proper study needed to be done. Lo & behold – there was a history of landslides and the possibility of more! So the politicians didn’t get their landfill. A relief to me as I lived within hearing/smelling distance.

  5. One Eyed Jack
    November 29, 2015 at 7:12 PM

    I’m sure the proposed landfill site was nowhere near any of the politicians’ houses, and that was their primary criteria.

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