EGU2020-17805
https://doi.org/10.5194/egusphere-egu2020-17805
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Urban growth changes the pulse of a large deep-seated landslide

Antoine Dille1,2, Olivier Dewitte1, Alexander Handwerger3,4, Dominique Derauw5,6,7, Nicolas d'Oreye7,8, Elise Monsieurs1,9,10, Sergey Samsonov11, Benoît Smets1, Matthieu Kervyn2, and François Kervyn1
Antoine Dille et al.
  • 1Royal Museum For Central Africa, Earth Sciences, Tervuren, Belgium (antoine.dille@africamuseum.be)
  • 2Department of Geography, Earth System Science, Vrije Universiteit Brussel, Brussels, Belgium
  • 3Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, CA, USA
  • 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 5Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Rio Negro - CONICET, Río Negro, Argentina
  • 6Centre Spatial de Liège, Université de Liège, Angleur, Belgium
  • 7European Centre for Geodynamics and Seismology, Walferdange, Luxembourg
  • 8National Museum of Natural History, Luxembourg, Luxembourg
  • 9Department of Geography, University of Liège, Liège, Belgium
  • 10F. R. S.—FNRS, Brussels, Belgium
  • 11Canada Centre for Mapping and Earth Observation, Natural Resources Canada, Ottawa, Canada

While the behaviour of slow-moving landslides – response to seasonal precipitation, seismic shaking, etc. – is well described in natural mountainous environments, little is known on the influence of urbanisation on their dynamics. Yet, gradual urbanisation of hillslopes is commonplace in the outskirts of many cities of the tropics. Typically anarchic, construction on previously undisturbed slopes often initiates or enhances landslide activity, rapidly increasing the number of people exposed to landslide hazard. Aiming at studying how landslides respond to their progressive urbanisation, we here present a detailed analysis of the dynamics of a large, thousand-year-old slow-moving landslide located in the rapidly expanding city of Bukavu (eastern DR Congo). This slope failure developed in highly weathered lava layers hosts today more than 80 000 inhabitants; for many affected by incessant destruction of infrastructures and housing.

We used 4 years of temporally dense 3D kinematic data from satellite interferometry (MSBAS 3D), pixel tracking on satellite and Unmanned Aerial System (UAS) orthomosaics and aerial photograph analysis to examine the relationships between urbanisation, landslide activity and rainfall and seismic patterns. We found a closely tied relationship between subsurface pore-water pressure changes and surface velocities. Seasonal rainfalls are driving the kinematics of the landslide at the weekly timescale, despite the large (~30-100 m) depth of the landslide. Analysing landslide dynamics over the last 60 years, we observed an increased activity over a zone of the landslide that will rapidly become the fastest landslide unit. This destabilisation occurred in the ‘90s, alongside an intensification of the (informal) urbanisation of the hillslope, at a time when region’s violent conflicts and insecurity drove important rural-urban migration. Still the most active today, this landslide unit moves at paces of 0.5-3 meters per year, causing significant and persistent damages to infrastructures. We here argue that changes in water runoff, concentration and infiltration due to the anarchic and poorly maintained urban extension is modifying the long-term behaviour of the landside, rather than overloading due to buildings (often light and wooden structures) and infrastructures. The very quick response to pore pressure changes could also be associated to the dense urban fabric, even though the tropical characteristics of this environment (wet-dry seasons, high rainfall, very high weathering) should not be ignored. Our analysis help improve the evaluation of landslide hazard and mitigation in the area, but also across the other many cities of the tropics where similar environmental and societal conditions are met. These findings also have implications for our understanding of landslide dynamics and how humans are interfering with landscape evolution.

How to cite: Dille, A., Dewitte, O., Handwerger, A., Derauw, D., d'Oreye, N., Monsieurs, E., Samsonov, S., Smets, B., Kervyn, M., and Kervyn, F.: Urban growth changes the pulse of a large deep-seated landslide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17805, https://doi.org/10.5194/egusphere-egu2020-17805, 2020

How to cite: Dille, A., Dewitte, O., Handwerger, A., Derauw, D., d'Oreye, N., Monsieurs, E., Samsonov, S., Smets, B., Kervyn, M., and Kervyn, F.: Urban growth changes the pulse of a large deep-seated landslide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17805, https://doi.org/10.5194/egusphere-egu2020-17805, 2020

Display materials

Display file

Comments on the display material

AC: Author Comment | CC: Community Comment | Report abuse

Display material version 2 – uploaded on 08 May 2020, no comments
Minor updates
Display material version 1 – uploaded on 05 May 2020, no comments