Better basis for assessing landslide risk in a changing climate

For more than a decade, SGI has studied erosion along the Göta River, Nors River, Säve River and Ångerman River. The aim was to assess future erosion and how it may affect landslide probability. The results are presented in the journal Environmental Earth Sciences.

“We wanted to investigate how a future climate associated with increased erosion could affect landslide risk. Greater knowledge makes it easier to design appropriate landslide risk-reduction measures. We found that recurrent surveys of riverbed geometry are among the most important sources of information for understanding erosion processes and detecting changes over time,” says Karin Odén, geotechnical engineer at SGI and one of the authors of the paper.

Even limited erosion can matter

The results show that the significance of erosion for landslide risk depends on how susceptible an area already is to landslides. In areas where landslide risk is already high, even limited erosion can substantially increase the risk. In areas with low landslide risk, more extensive erosion is required before the risk increases.

The results also show that, in heavily regulated rivers, climate projections alone are not sufficient for assessing future erosion. How river discharge is regulated may have a greater influence on erosion, sediment transport and channel morphology than climate-related changes. The authors therefore recommend that different approaches to flow regulation be included as separate scenarios in future projections.

The role of erosion is less well studied

Previous research on climate change and landslides has largely focused on landslides triggered by precipitation. The influence of river erosion on landslide probability has received less attention.

The new study synthesises lessons learned from assessments conducted by SGI
between 2009 and 2022. The work included bathymetric surveys, sediment analyses, and hydrodynamic and morphological modelling to assess how erosion may develop under a future climate.

SGI considers the workflow used in these assessments to be transferable to other countries, provided that the models are adapted to local conditions. At the same time, there is a need for further research to better integrate discharge, sediment transport, erosion and slope stability.

“We want to share the knowledge we have gained over the course of more than a decade. We hope that others can build on this work and further develop methods for long-term assessments of erosion,” says Karin Odén.