The environmental impact of landslides on the population living on the eastern footslopes of the Aberdare ranges in Kenya: a case study of Maringa Village landslide

Landslides are a recognized but poorly studied phenomena in the eastern footslopes of the Aberdare ranges in central Kenya. The Aberdare ranges traverse the Murang'a, Kiambu, Nyeri and Nyandarua districts of Kenya where fatal landslides have occurred in the past. A detailed study of a major landslide which occurred at Maringa village in Murang'a district on 30 April 1997, has been undertaken. The landslide buried three houses at the toe of a slope and killed all the 11 occupants in their sleep. It is shown that the geology and climate of the study area contribute to the prevalence of landslides not only in Murang'a but in all the andosol-covered areas throughout the eastern footslopes of Aberdare ranges. Rapid weathering of pyroclastic rocks in a warm and wet climate create a regolith which is generally weaker than the underlying better-cemented basalt and basaltic agglomerates. The landsliding occurred when the weathered pyroclastic regolith become saturated after a heavy rainstorm on high mechanically unstable slope which slid over the more stable basalts. Over-saturation of clay soils (andosol) which were also derived from weathering of pyroclastic rocks contributed to the slope failure. The results of the study show that besides fatalities and injuries, the landslide destroyed homes, plantations and roads.