An article by the NZ Herald reports that recommendations for slope monitoring and early warning made by a geotechnical consulting firm in a report 2 years before the initial failure were not adopted by Auckland Transport. The Birkenhead landslide initially took out 25 parking spaces in a retail area in October of 2017, and a larger landslide in November of the same year took out a micropile or other drill rig working to stabilize the site. Local officials defended the decision, indicating that they instead opted for regular site visits and visual observation of cracks noted in the report. The initial recommendations by GHD Engineers included the monitoring as a minimum, and also recommended several stabilization options in the range of $500k. The current estimates to repair the landslide are $14M to $24M.
The USGS has a documentary on landslide video on landslide danger in the San Francisco Bay area entitled “Riding the Storm”. I think the target audience is more general than geologist or engineer, but it is still interesting. The bullet points from the USGS site:
- A catastrophic 1982 rainstorm triggered 18,000 landslides in the Bay Area, claiming 25 lives and causing $66 million in property damage
- The combination of steep slopes, weak rocks, and intense winter storms make Bay Area uplands an ideal setting for landslides
- Landslides include both swift, potentially deadly debris flows and slower, but destructive deepseated slides
- Learn what USGS scientists have discovered about landslide dynamics and which slopes are most susceptible to sliding
- Hear the devastating stories of Bay Area residents affected by landslides and learn to recognize the danger signs
Click through to view the trailer and for links to download the full video. (Image credit: USGS)