How can we beat landslides?
Q: Is it normal to have this many landslides after an earthquake and how can we safeguard our roads in future?
A: Dr Tom Wilson and Professor Tim Davies from the University of Canterbury’s geological sciences department say:
When earthquakes occur in steep mountainous landscapes it is common to experience lots of landslides.
A similar number of landslides have been observed after other large earthquakes in New Zealand and overseas, such as the recent earthquake in Nepal in 2015.
The earthquake in China in 2008 caused an estimated 80,000 landslides while the Nepal earthquake caused an estimated 22,000 landslide throughout the Himalayas.
Geological evidence indicates that large earthquakes and associated extensive landsliding has occurred throughout the South Island previously.
We can now use models to estimate where landslides might occur as a result of big earthquakes.
The problem is that we can’t reliably predict where or when big earthquakes might occur.
Generally speaking, there are three main ways to make our infrastructure more resilient to natural hazards like earthquakes and landslides.
First, site our infrastructure so it is in as safe a location as possible, using natural hazards scientists and engineers to robustly identify hazards and mitigate the risks.
Second, design and build infrastructure to resist or avoid being damaged by natural hazards, such as engineered bridges, using rock shelters and tunnels, and engineered foundations wherever possible.
Third, add redundancy to our networks where there are highfunctioning alternative routes which perform if another route or line is taken out.
All these options cost money, sometimes a lot of it, so as a society we need to judge what sort of safety and performance we want from our vital infrastructure systems during disasters.
Making changes is sometimes easiest after a disaster.
But a critical issue is that many of our other existing infrastructure networks are highly vulnerable to natural hazards and this need to be addressed now.
While this is fresh in our minds, this is the time to discuss this and take action.