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1 Musée Royal de l'Afrique Centrale, Leuvensesteenweg 13, B-3080 Tervuren, Belgium (e-mail: philippe.trefois{at}africamuseum.be)
2 Centre Universitaire de Bukavu, B.P. 570, Bukavu, Democratic Republic of Congo
3 Université du Burundi, B.P. 2700, Bujumbura, Burundi
The city of Bukavu, on the south coast of Lake Kivu in the Democratic Republic of Congo, suffers from frequent landsliding, which leads to continual damage and destruction of buildings, roads, waterworks and sewerage infrastructure. Thirty-one landslides identified on aerial photographs of 1954 and 1973 are located outside the Bukavu micro-rift and are related to actively incising rivers. Their origin is thought to be due to increases in hydrostatic pressure. Six landslides occur within the Bukavu micro-rift, four of which are much larger and wider than other slope failures in the study region. These large landslides are adjacent to, or crossed by, active faults. They fall far below the topographic threshold envelope, a relationship of slopes at the head of the slide and the surface area drained into it, indicating seismic or anthropomorphic triggering. The Bukavu landslides still reactivate occasionally. Deforestation, followed by a large increase in the population, have been indirect causes of the reactivated mass wasting processes. On the steep slopes in the south of the city the high density of newly built houses has led to reduced water infiltration and enhanced runoff, causing landslides and mudflows. Very high spatial resolution IKONOS satellite images have recently been used as base maps for geohazard assessments of Bukavu. A geographical information system (GIS) has been developed for Bukavu's planners: this shows the locations of buildings, roads and tracks, the river network, the water distribution system and the sewerage infrastructure, as well as areas of slope instability.
