Publications

Nobile, A.,  Dewitte, O.,  Dille, A.,  Monsieurs, E.,  d'Oreye , N.,  De Rauw, D.,  Samsonov, S. & Kervyn, F. 2017. ‘InSAR time series to characterize landslide ground deformations in a tropical urban environment: focus on Bukavu, East African Rift System (DR Congo)’. Fringe. Book of abstracts.

Résumé de colloque

The western branch of the East African Rift System, in Central Africa, is a region naturally prone to landslides due to the geomorphology of the area and to the occurrence of earthquakes and heavy rainfall events. The city of Bukavu (DR Congo) is located within the Rift, on the southern shore of Lake Kivu, in a tropical environment. Little is yet known about the current kinematics and the processes that drive large slow-moving landslides that continuously affect highly populated slopes of the city. Here we use InSAR time series to monitor ground deformations associated to these slope instabilities. Using 100 Cosmo SkyMed SAR images acquired between March 2015 and June 2016 with a mean revisiting time of 8 days in both ascending and descending orbits, we produced and compared displacement rate maps and ground deformation time series derived from two techniques: the classical Small Baseline Subset (SBAS) and the Multidimensional Small Baseline Subsets (MSBAS). With the MSBAS technique, the ground deformations observed by the two satellite orbits are jointly inverted, increasing the sampling frequency and allowing to measure higher ground deformation rates. The study focuses on the largest landslide in Bukavu (1.5 km²) that mostly moves in the E-W and vertical directions. InSAR results show that the landslide is divided into blocks that move with different velocities (up to 25 cm/yr), which is consistent with field observations and DGPS measurements taken at several benchmarks in the area during the same period. The combination of this data with rainfalls, seismicity and field observations should help us to better understand the mechanisms (of natural and/or anthropogenic origins) that control the evolution of this landslide.