Landslides risk assessment and monitoring

Landslides risk assessment and monitoring

Mar 8th, 2023

During the first couple decades of our professional life we worked extensively with Landslides risk assessment and monitoring in the European Alps. Most sites were in Switzerland and Italy.

At the beginning “risk” was not yet the buzz-word it became later. Clients and governments were seeing hazards impinging on population and infrastructure like transportation, hydropower and bulk-storage facilities. Engineering “repairs” were the most obvious path.

Landslides risk assessment and monitoring

Nevertheless, back in 1997 Riskope’s founder Franco Oboni participated in a IUGS workshop in Honolulu. The event’s goal was to define a Glossary of risk-related technical terms specific to Slopes and Landslides.  In short, the IUGS Working Group on Landslides, Committee on Risk Assessment, produced a glossary for Quantitative Risk Assessment for Slopes and Landslides.  Actually, that Glossary of risk-related technical terms has kept evolving. It is now applicable to other fields of business and industries and its latest version is freely available in our website.

Discussing Landslides risk assessment and monitoring

Today we return to our “first love” to discuss a few points related to landslides risk assessment and monitoring.

One of our latest books is:

  • Di Capua, G., Bobrowsky, P.T., Kieffer, S.W. and Palinkas, C., 2021, Geoethics: Status and Future Perspectives. Geological Society, London, Special Publications508(1), pp.NP-NP.8,

And our chapter in that book is “Holistic geoethical slope portfolio risk assessment”. We endeavour to show how sustainability and ethics can be fostered by using rational, repeatable, transparent quantitative risk assessment applicable at the local scale as well as on a large scale. Among the case histories we present, one deals with the Cassass landslide in North Western Italy.

A few references on the Cassass landslide

Way before the book cited above, we published various papers on the Cassass Landslide and the studies we performed. We show the references below in chronological order.

 Space observation new tools

At Riskope we have used space observation results such as:

  • Interferometric Synthetic Aperture Rada (InSAR),
  • Normalized Difference Vegetation Index (NDVI);
  • Normalized Difference Water Index (NDWI);
  • Normalized Difference Moisture Index (NDMI) and finally
  • Short wave infrared composite (SWIR)

for a number of cases in the mining industry and landslides and/or man-made slopes. Here are a couple references.

In those papers we already cautioned users on a few issues we have encountered. Happily, we were working with experienced and friendly suppliers that not only helped us solve the issues, but also pointed out possible “traps”, potentially leading to hazardous misinterpretations.

So, we approached with keen interest the newly published and publicly available European Ground Motion (EGM portal https://land.copernicus.eu/pan-european/european-ground-motion-service manual: https://land.copernicus.eu/user-corner/technical-library/egms-end-user-interface-manual ).

We looked at the Cassass Landslide (Loc 45.06567, 6.90520) between beginning of November 2016 and November 2020.

The image below shows an example of the results the platform delivered.

Landslides risk assessment and monitoring

Comments on the results.

If on one hand we would like to congratulate ourselves for having mitigated the sliding activity to such an extent, on the other we have to admit we do not really believe these results. Too little yearly average movement, not enough “red dots” on the slope! Indeed, the original slope had spikes at more than 10cm/yr and was moving “en masse”, of course with significant variabilities across and along its surface.

So we asked the publisher of the EGM a couple questions which unfortunately remain to this date unanswered. We hope 2023 will bring some replies on this subject.

We then asked our friend Paolo Mazzanti who is a specialist of technologies such as SAR Interferometry and PhotoMonitoring. His reply confirmed our views. We summarize it as follows:

  • InSAR data are extremely valuable assets, especially when considering the backward looking analyses of a “unexplored site”.
  • That asset however requires intense scrutiny and interpretation, especially when dealing with mountainous terrain, high vegetation and other peculiarities such as steep slopes.
  • Large scale imagery (such as the one provided by the EGM public platform) is not sufficient in most cases.
  • Oftentimes the use of well selected satellites and applying data fusion techniques may significantly enhance the results.

Closing remarks on Landslides risk assessment and monitoring

At the end of the day a large scale publicly available platform like EGM should be used with care and its limits should be recognized to avoid blunders.

It is possible to seamlessly link advanced land-based monitoring devices, space observation tools and other imagery results with quantitative risk analysis of slopes.

In order to avoid the surprise effects of extreme events and climate change the quantitative risk assessments should include projections based on the best available data and predictions.

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