Landslides' mechanism and evolution in the western Rwanda

Landslides' mechanism and evolution in the western Rwanda

Salah DRAIDIA1,*, Meriam EL OUAHABI1, Olivier DEWITTE2, Nathalie Fagel1, Hans Balder HAVENITH1

1 Institution 1 University of Liège
Department of Geology
Street, n°
4000 Liège Belgium

2 Institution 2 Royal Museum of Central Africa
Department of Geomogy
Tervuren Belgium

*Corresponding author:
sdraidia@gmail.com,
Département de Géologie, Quartier Agora, Allée du six Août, 14, B- 4000 LIEGE (Sart Tilman)
Tel +32 0497351617

Keywords: mass movement, landslides, landscape evolution, geohazard,.

Abstract
The mass movement, and especially the instability of the soil and rocks, play a significant role in the changing aspect and the evolution of the landscape worldwide and particularly in tropical region. In Central Africa the landslides and others kind of instabilities are very frequent, important and represent a real threat for both population and economy. The case of Rwanda is remarkable, this country which is known as the country of thousand hills, is rich of various and very complex morphology caracterized by very steep slopes crossed by a dense network of watercourse, powered by a considerable amount of precipitation distributed in two wet seasons. The growing economy of the country brings a lot of project of infrastructures and mines and quarries exploitation (embankments and cuttings) which have a strong impact on the triggering of huge instabilities and so the modification of landscape. These instabilities and the intense activity of the rivers and streams could be considered as the engine who control the shaping and the remodeling of the landform. To understand the evolution process of these instabilities, and then the landscape change we started by the mapping of the instabilities using satellite images and then we went on the field to validate the inventory to identify the morphological aspect of the terrain, to refine our knowledge of the geological nature of the materials by sedimentological analyses on selected samples, and of course to try to better know the impact of the rock's weathering process leading to the constant modification of the landform. The computer-based quantitative analyses using GIS's data processing, were carried out to help to understand the distribution of the instabilities and the geomorphological phenomena observed to better connect and explain the whole information collected. The aim of the study is to bring in more than the mapping of instabilities a response about the process and the evolution of the instabilities and the factors impacting the phenomenon.