Preprints
https://doi.org/10.5194/nhess-2021-336
https://doi.org/10.5194/nhess-2021-336

  17 Nov 2021

17 Nov 2021

Review status: this preprint is currently under review for the journal NHESS.

Natural and human-induced landslides in a tropical mountainous region: the Rift flank west of Lake Kivu (DR Congo)

Jean-Claude Maki Mateso1,2, Charles Bielders2, Elise Monsieurs3,4,5, Arthur Depicker6, Benoît Smets3,7, Théophile Tambala1, Luc Bagalwa Mateso1, and Olivier Dewitte3 Jean-Claude Maki Mateso et al.
  • 1Centre de Recherche en Sciences Naturelles, Department of Geophysics, Lwiro, DR Congo
  • 2Université catholique de Louvain, Earth and Life Institute – Environmental Sciences, Louvain-La-Neuve, Belgium
  • 3Royal Museum for Central Africa, Department of Earth Sciences, Tervuren, Belgium
  • 4University of Liège, Department of Geography, Liège, Belgium
  • 5F.R.S.-FNRS, Brussels, Belgium
  • 6KU Leuven, Department of Earth and Environmental Sciences, Belgium
  • 7Vrije Universiteit Brussel, Department of Geography, Brussels, Belgium

Abstract. Tropical mountainous regions are often identified as landslide hotspots with particularly vulnerable populations. Anthropogenic factors are assumed to play a role in the occurrence of landslides in these populated regions, yet the relative importance of these human-induced factors remains poorly documented. In this work, we aim to explore the impact of forest cover dynamics, roads and mining activities on the occurrence of landslides in the Rift flank west of Lake Kivu in the DR Congo. To do so, we compile an inventory of 2730 landslides using © Google Earth imagery, high resolution topographic data, historical aerial photographs from the 1950’s and extensive field surveys. We identify old and recent (post 1950’s) landslides, making a distinction between deep-seated and shallow landslides, road landslides and mining landslides. We find that susceptibility patterns and area distributions are different between old and recent deep-seated landslides, which shows that natural factors contributing to their occurrence were either different or changed over time. Observed shallow landslides are recent processes that all occurred in the past two decades. The analysis of their susceptibility indicates that forest dynamics and the presence of roads play a key role in their regional distribution pattern. Under similar topographic conditions, shallow landslides are more frequent, but of smaller size, in areas where deforestation has occurred since the 1950’s as compared to shallow landslides in forest areas, i.e. in natural environments. We attribute this size reduction to the decrease of regolith cohesion due to forest loss, which allows for a smaller minimum critical area for landsliding. In areas that were already deforested in 1950’s, shallow landslides are less frequent, larger, and occur on less steep slopes. This suggests a combined role between regolith availability and soil management practices that influence erosion and water infiltration. Mining activities increase the odds of landsliding. Mining and road landslides are larger than shallow landslides but smaller than the recent deep-seated instabilities. The susceptibility models calibrated for shallow and deep-seated landslides do not predict them well, highlighting that they are controlled by environmental factors that are not present under natural conditions. Our analysis demonstrates the role of human activities on the occurrence of landslides in the Lake Kivu region. Overall, it highlights the need to consider this context when studying hillslope instability characteristics and distribution patterns in regions under anthropogenic pressure. Our work also highlights the importance of considering the timing of landslides over a multi-decadal period of observation.

Jean-Claude Maki Mateso et al.

Status: open (until 29 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-336', Anonymous Referee #1, 03 Dec 2021 reply
  • RC2: 'Comment on nhess-2021-336', Anonymous Referee #2, 03 Dec 2021 reply

Jean-Claude Maki Mateso et al.

Jean-Claude Maki Mateso et al.

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Short summary
To summarize, this research highlights the importance of human activities on the occurrence of landslides and the need to consider this context when studying hillslope instability patterns in regions under anthropogenic pressure. Also, this study highlights the importance of considering the timing of landslides and hence the added value of using historical information for compiling an inventory.
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