The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
New Zealand is a country with a severe level of landslide hazard, resulting from a combination of the tectonic setting, the geology, the climate and the impact of human activities. It is estimated that landslides cost the country NZ$250 million per annum, and there has been a host of high profile landslide incidents in recent years, including severe damage to major roads and the main railway line from the 2016 Kaikoura Earthquake and huge numbers of landslides triggered by Cyclone Gabrielle in February 2023.
To manage the risk, GNS Science has released a new version of its Landslide Planning Guidance, which is available online. GNS Science has also released a very good video to introduce the guidelines:-
There is also an online webinar that provides further detail about the Landslide Planning Guidance:-
Whilst the guidance is clearly specific to New Zealand, there is much here that is of use more widely. I would particularly recommend Chapter 4, which covers landslide susceptibility, hazard and risk analysis. Much of this work was developed in the aftermath of the Christchurch Earthquakes, and has been refined subsequently. It is the most brilliant exposition of practical landslide risk analysis that I have seen.
In addition, the planning tools section (chapter 6) is a really useful guide to management of the hazard, and thus reduction of risk. It has applicability much more widely, and this is supplemented in Chapter 7 with a set of examples.
In the week in which the Oso landslide in Washington State, USA is much in the news (tomorrow it will be a decade since that accident, which killed 43 people), this sort of document is immensely useful. It is worth remembering that a 1997 report for the US Army Corps of Engineers warned of “the potential for a large catastrophic failure”. Despite this, new houses were constructed below the landslide that were subsequently destroyed, with significant loss of life.
Landslide Planning Guidance of the type produced by GNS Science can be a significant step towards reducing such incidents.