This blog is written by Anika Braun, a lecturer in engineering geology at Technische Universität Berlin, Germany. Anika studied Georesources Management and gained a PhD at RWTH Aachen University, Germany, after which she took up an exciting job studying landslides in China. She also plays the violin. You can read about her adventures in the wild south of China and other places on Twitter @FrlBraun and in her guest blogs on paleoseismicity.org.
What is a landslide and why do we care?
Simply put, a landslide is the movement of rock, debris, or earth down a slope. Landslides are natural events that shape landscapes on Earth, and even on other planets like Mars. But when they occur in populated areas, human lives and infrastructure are at risk. From 2004 to 2016, 4862 recorded landslides killed more than fifty thousand people. The Freetown mudslides in Sierra Leone in 2017 killed more than one thousand people.
How can we reduce landslide risk?
In landslide science, “risk” is a combination of the chance of a landslide happening, the elements at risk (such as people, houses, and roads) and their vulnerability. By addressing one or more parts of this equation, landslide risk can potentially be reduced.
To reduce risk, we need to understand why, where, when, and how landslides occur. The good news is that this is actually doable. Unlike some other geological hazards, like earthquakes or hurricanes, landslides tend to affect small areas and their movement is usually relatively slow. Also, they only occur in hilly or mountainous environments (if you live in a flat area you can relax!)
In order to create “Resilient Cities” (as proposed in the UN Sendai Framework for Disaster Risk Reduction 2015-2030), it is important to include landslide experts in urban planning. Experts such as engineering geologists can carry out fieldwork and look at satellite data to find old and active landslides. They can use this information to point out areas that are not safe to build on, and to plan technical solutions to stop landslides.
Who are engineering geologists anyway?
Engineering geologists study the problems that result from interactions between geology and humans. The goal, of course, is to find solutions. This is why I find engineering geology so exciting – I get to work at the boundary between geology and human activities, making our geologically active planet safer to live on.
Why do landslides occur?
Whether a mountain slope is going to fail and form a landslide depends upon a combination of different ‘preparing’ and ‘triggering’ factors.
Preparing factors are what makes a slope sensitive, or susceptible, to landsliding. Things like the shape and steepness of the slope, or the types of rock or soil forming the slope.
Triggering factors are what causes the landslide to happen, such as heavy rainfall or earthquakes. I said earlier that landslides are natural events. That is not the complete truth. Human activities can cause landslides too. The creation of artificial slopes, the cutting down of trees, leaky drainage pipes…all can lead to landsliding.
Here’s the thing. In our concept of landslide risk (the combination of landslide likelihood and elements at risk), urbanisation does not just increase the number of elements at risk; it also increases the likelihood of a landslide.
Will climate change affect landslides?
The climate crisis is likely to make the landslide risk equation explode. Phenomena like extreme rainfall events and changing rainfall patterns, droughts, changes in groundwater levels, wildfires, and melting of glaciers and permafrost will cause more landslide activity.
At the same time, sea-level rise and droughts are driving more people to live in cities. Cities are growing fast, which is increasing pressure on the environment.
Although the exact impacts of the climate crisis are still uncertain, one thing is for sure. There are big challenges ahead in landslide risk reduction. It is really important that landslide experts are involved in urban development in mountainous areas.
The world needs engineering geologists!
Engineering geologists will be busy dealing with landslides for decades to come, and are also needed to work on many other challenges faced by society as we move towards a low-carbon future. Geothermal energy, hydroelectric dams, windfarm construction, underground storage of carbon dioxide, and remediation of coal mines are just some examples of issues that need engineering geologists.
If you’d like to learn more about landslides, check out Dave Petley’s “The Landslide Blog”. Dave is a landslide science superstar, and covers many of the scientific and social aspects of landslides in his blogs.