This example, that we presented at the WLF2 Conference in Rome, constitutes a complete and fully developed which included the following phases: probabilistic behaviour forecast, behaviour monitoring (which luckily allowed to actually “see happen” what we had predicted a few years earlier), Risk Based Decision Making (RBDM), and finally implementation of mitigative and crisis management plan. Interestingly, in a curious turn of events, while doing some reconnaissance work on the landslide, two of us almost lost our lives in a helicopter crash. Risk managers are unfortunately not immune to risks...and somehow it was a good lesson for us to be in the “victim role” that day.

1. Second World Landslide Forum Ð 3-7 October
2011, Rome
The Cassas Landslide and its impacts on an international
& Olympic transportation corridor: studies, monitoring,
solution and crisis plans
Franco Oboni, Claudio Angelino, Bartolomeo Visconti

2. Cassas Landslide, Italy
- Volume 20 - 30 million m3
- Lenght appx. 1.8 Km
- Average slope 50 to 55 %
- Slide depth appx. 60 m

7. Meanwhile the monitoring continued...and in Fall
2000 we witnessed what we had calculated!

10. Cassas Landslide
Rainfall 1998-2002

14. The selected drainage tunnel proved to be a difficult engineering
task due to mountain environment and geotechnical challenges.
The finished tunnel has performed satisfactorily for 5 years now,
draining more than 1300 m 3/mo of water from the slide body with
positive effects in terms of overall stability.

17. • Probabilistic geotechnical analyses have been successfully coupled with
monitoring data.
• Following calibration and observation good understanding of the parameters
influencing and dictating the behavior of the slope was achieved.
• The study also aimed at finding a correlation between antecedent rain, net of
evapo-transpiration, and the slope response, in terms of movements.
• Rains over a period of 300 days were found to display the strongest correlation
with inclinometers data.
• The strong correlation made it possible to propose a relationship between net
antecedent rain and the velocity in a given point.
• As a result of the quantitative risk assessment (QRA), a drainage tunnel was
designed and constructed to mitigate potential reactivations due to water table
heave in case of long rainy seasons.
• The finished tunnel has drained more than 1300m 3 per month of water during 5
years from the slide body with positive effects in terms of overall stability.