A new study shows that landslide activity in Vejle, Denmark, may increase due to climate change. For the first time, researchers have used publicly available data to assess how climate change can affect the movement in Danish landslides. The study shows that the landslides are sensitive to climate variations, and that we can expect increased landslide activity in the future.
For a long time, there has been a clear expectation among researchers that climate change, and especially a wetter climate, has an accelerating effect on landslides. This means that the landslides will move more – and more often. But this has not previously been scientifically proven in Denmark. Now the first study on the effect of climate change on landslides in Denmark has been published, and the conclusion is clear:
“It is clear that there is very little or no movement in the landslides in relatively dry winters, when the groundwater is low. Wet winters, when the groundwater is high, on the other hand, cause more activity in the landslides,” says Kristian Svennevig, Senior Researcher at GEUS and first author of the article published in the journal Natural Hazards and Earth System Sciences.
Public data show development in landslides
In the research article ‘Assessing the impact of climate change on landslides near Vejle, Denmark, using public data', four researchers from GEUS present a workflow that uses publicly available data in an assessment of how variations in rainfall and the groundwater level affect the dynamics of a landslide.
The researchers have selected three large slow landslides east of Vejle and analysed them by using freely available data.
“The study is an example of the fact that freely available high-quality data hold great potential. The study would not have been possible without free elevation, climate and groundwater models as well as satellite data, all of the highest quality. We can only make statements with as much certainty as we do in the study, because the data quality is top notch,” says Kristian Svennevig, Senior Researcher at GEUS.
Among other things, the authors have looked at the groundwater level based on the DK-HIP model (Danish Hydrology Information and Prognosis system), which has been used to simulate the depth of the water table back in time as well as into the future.
The data for the studied period, 2015-2019, show that the landslides move up to 8 cm per year in wet winters, when the groundwater level is approximately half a metre higher than usual. In dry winters, when the groundwater level is not that high, there is no or very little landslide movement.
The wetter climate of the future will lead to more landslide activity
House owners, city planners and decision-makers may like to know whether they can expect increased groundwater levels and thus increased landslide activity in an area with active landslides, such as the areas near Vejle.
This insight can be obtained by looking at the projections of future climate change, which the UN’s Climate Panel (IPCC) prepares. The researchers behind the study have looked at the scenario known as RCP8.5 (Representative Concentration Pathway) amongst others. According to that, there will be an increase in the groundwater level for the area near Vejle in winter of up to 0.7 metres before the year 2100. This will lead to more movement in the landslides.
But even in more positive scenarios for the development of the climate, for example the so-called RCP4.5, increased landslide activity is to be expected.
“Based on the data, we estimate that we can expect even more movement in the landslides in the future, as threshold values in the groundwater may be exceeded more often. As the climate becomes wetter, landslides move more. Before we started the study, we had a feeling that this was the case, but now we can say it with great certainty,” says Kristian Svennevig, Senior Researcher at GEUS.