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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 7 | Copyright
Nat. Hazards Earth Syst. Sci., 18, 1867-1890, 2018
https://doi.org/10.5194/nhess-18-1867-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 06 Jul 2018

Research article | 06 Jul 2018

Formation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi

Léonidas Nibigira1, Hans-Balder Havenith1, Pierre Archambeau2, and Benjamin Dewals2 Léonidas Nibigira et al.
  • 1Geohazards and Environment, Department of Geology, University of Liege, 4000 Liege, Belgium
  • 2Hydraulics in Environmental and Civil Engineering (HECE), Research unit Urban & Environmental Engineering, University of Liege, 4000 Liege, Belgium

Abstract. This paper investigates the possible formation of a landslide dam on the Kanyosha River near Bujumbura, the capital of Burundi, as well as the interplay between the breaching of this landslide dam and the flooding along the river. We present an end-to-end analysis, ranging from the origin of the landslide up to the computation of flood waves induced by the dam breaching. The study includes three main steps. First, the mass movement site was investigated with various geophysical methods that allowed us to build a general 3-D model and detailed 2-D sections of the landslide. Second, this model was used for dynamic landslide process modelling with the Universal Distinct Element Code. The results showed that a 15m high landslide dam may form on the river. Finally, a 2-D hydraulic model was set up to find out the consequences of the breaching of the landslide dam on flooding along the river, especially in an urban area located downstream. Based on 2-D maps of maximum water depth, flow velocity and wave propagation time, the results highlight that neglecting the influence of such landslide dams leads to substantial underestimation of flood intensity in the downstream area.

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Flood prediction methods are often based solely on climatic parameters and sometimes on the failure of existing dams. This paper shows the importance of multi-hazard studies, including potential natural dam formation to avoid risk underestimation. We present an end-to-end analysis, ranging from the origin of the landslide up to the computation of flood waves induced by the dam breaching. The paper is based on a case study of Bujumbura in the East African Rift Valley, a multi-hazard environment.
Flood prediction methods are often based solely on climatic parameters and sometimes on the ...
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