Landslides consequences of accidents are multidimensional

Recent research results confirm a point we have pushed forward for many years. Landslides consequences of accidents are multidimensional and risk assessments should consider all the pertinent dimensions, such as for example:

• loss of life,
• financial losses, and finally,
• environmental and other impacts.

Indeed, Strouth and McDougall recent Historical Landslide Fatalities in British Columbia, Canada: Trends and Implications for Risk Management, precisely proves the point plus a number of other interesting considerations.

A review of British Columbia landslide fatalities

The population in BC increased approximatively five folds between 1950 and 2020, based on 10 years averages. Meanwhile the number of landslides fatalities reduced five folds. We think it would be interesting to compare this trend with other G20 countries in the future to gain an international understanding of the evolution.

What those BC numbers tell for the period from 1960 to 2019 is that the fatality rate has dropped from 0.3 to 0.02 deaths per 100,000 people per year.

The paper features a comparison between landslides and other accidents. It would have been nice to see an explicit distinction between voluntary and involuntary endeavours. Indeed, this would have added clarity to the overall image delivered by the comparison. Anyways, the result of the comparison is that, relative to other causes of death, the landslide death toll in BC is low.

Main conclusions of the paper

The paper shows through various graphs how landslides in BC, despite being the most common disaster, are not significant in terms of casualties. The comparison with other causes of mortality is quite clear. The F-N curve presented would have benefited from a comparison with other disasters. Among these we can cite, for example avalanches, airplanes and/or meteorological events. However, then the paper states that landslides remain an important hazard if a regional risk management plan is undertaken.

So are landslide an important risk or not? What is the root cause of the apparent disconnect?

We believe the answer has two parts:

• the first part is the risk metric. Indeed, the paper identifies the metric as an issue. As a result, the number of casualties needs to be part of a much broader risk function. The consequences should encompass all type of quality-of-life disruption and losses. Among these we can cite property destruction, economic losses, and finally infrastructure or transportation service disruption. Only then proper prioritization will become possible.
• The second part has to do with societal risk tolerance. Unless one develops a tolerance threshold encompassing the selected risk metric, it is virtually impossible to carry out proper risk prioritization due to a number of reasons. For instance, it is possible that hazard fatigue emerges. That occurs when small, but frequent events stir “fix them all” orders, even if the mitigation return on investment is very low. We add that only a proper risk analysis would deliver a rational answer.

Closing remarks

The main conclusion from the paper we reviewed reads as follows. “This suggestion supports arguments in Strouth and McDougall (2020) that advocate for risk evaluation tools that consider economic impacts and cost effectiveness of landslide risk management measures in addition to life-loss risk tolerance thresholds”.

We fully support this conclusion. In addition we would state that risk assessments should include the full scope of the dimensions of the considered failures and use ad hoc tolerance thresholds.

Tagged with: F-N curve, Landslides consequences, landslides fatalities, loss of life, risk assessments, Risk Management, risk metric, Root cause

Category: Consequences, Probabilities, Risk analysis, Risk management