Landslides susceptibility assessment using AHP method in Kanyosha watershed (Bujumbura-Burundi): Urbanisation and management impacts

Abstract

The Kanyosha watershed is unstable due to the presence of several landslides, which occupy about 3% of the study area. They are causing major damage which costs expensive to the Government of Burundi as well as to the population residing there and their properties. Roads, schools, irrigation canals, houses, crop fields, etc., are in danger of collapse. These landslides are mostly naturally occurring but can sometimes be reactivated by heavy rains or human activities during the excavation of building materials from the river bed.In order to carry out this study, we used the multivariate statistical classification with weighting of the responsible parameters of landslides risk to reach the susceptibility map of mass movements in the Kanyosha watershed. Remote sensing, geology, morphometry and bibliography were the data sources for the different parameters. Google Earth images, ortho-photos and field prospecting helped us to identify the landslides needed to validate the susceptibility map.During the fieldwork, we observed 34 landslides of different types, which were superimposed on the mass movements susceptibility map obtained using the Analytic Hierarchy Process (AHP) and compared to previous studies in which the matrix indexing method was used. We found approximately similar results with the consideration of different scales of work. These reasons confirm the validity of the susceptibility map at the level of the Kanyosha watershed, a map which is an essential document for urban planning and land management.

GIS-Based Weights-of-Evidence Model for Landslide Susceptibility Mapping and Assessment in the Hillslopes of Bujumbura, Burundi

“…The geology is among the main controlling factor of landslides in the study area and in the region (Jacobs et al 2017;Kubwimana et al 2018). The spatial landslides distribution showed that most of the landslides occurred in outcrops within gneissic or granite units (Kubwimana et al 2018). To extract the lithological units, we digitalized the geological map of Burundi, Bujumbura sheet at 1/50000 (Laghmouch et al 2018).…”

“…The slope angle controls landslides in the study area. Kubwimana et al (2018) showed that the slope angle controlled landforms in a central zone of the study area, the watershed of Kanyosha. In this study, we computed slope angle 10m DEM-based under ArcGIS 3D analysis tools.…”

“…Only 89 landslides have already been inventoried (Nibigira et al 2015;Shirambere et al 2018). Susceptibility analysis at regional scale has shown that the region is predisposed to various landslides processes (Jacobs et al 2018; Kubwimana et al 2018;Monsieurs et al 2018;Shirambere et al 2018;Depicker et al 2020b; Nsengiyumva et al 2019). Therefore landslides damaged from simple destruction to the loss of several human lives (e.g., Reliefweb 2014).…”

“…Nevertheless, accurate landslide susceptibility analysis is too limited at the North Tanganyika-Kivu Rift (Monsieurs et al 2018;Depicker et al 2020b). At Bujumbura hillislopes scale, Nibigira et al (2015) and Kubwimana et al (2018) attempted to assess the susceptibility using a multi-criteria approach where slope, lithology and fault density were found to be the main geoenvironmental drivers of landslides. Looking at landslides and their characteristics used for model validation, we argue that these two studies are too weak for landslide susceptibility assessment of the hillslopes of Bujumbura.…”

“…The study focuses on assessing the rugged hillslopes of Bujumbura, where many landslides impacts are concentrated in Burundi (Moeyersons and Trefois 2012;Reliefweb 2014). Our approach assumes that the current landslide susceptibility available is biased due to the underestimation of landslides used during its development (e.g., Nibigira et al 2015;Kubwimana et al 2018). The new susceptibility map will be, therefore, an effective tool for the civil protection authorities in charge of the early warning system another to reduce the landslides damages.…”