Land use changes on the slopes of Mount Elgon and the implications for the occurrence of landslides

A reconstruction of land use changes and the implications thereof for landslide occurrence on critical slopes of Mount Elgon in Eastern Uganda were undertaken. Aerial photographs taken in 1960 formed the benchmark for the analysis of respective land use changes between 1995 and 2006, using 30 m Landsat TM and 20 m SPOT MS images. Landslide sites were mapped using a MobileMapper, and terrain parameters were derived using a 15 m Digital Elevation Model. A supervised classification approach was employed to generate land-cover maps, from which the areas of three land-cover classes (agricultural fields, woodlands and forests) were calculated. A post-classification comparison change-detection technique revealed different trends in land-cover change between the periods 1960-1995 and 1995-2006. Whereas there were minimal land use changes between 1960 and 1995, the period 1995-2006 marked a considerable loss of woodlands and forest cover, particularly on steep concave slopes (36 degrees-58 degrees) of the National Park. The encroachment onto the critical slopes was noted to have induced a series of shallow and deep landslides in the area. All the mapped landslides were noted to lie on steep concave slopes of a northerly orientation, which had been opened up for cultivation. Deforestation and cultivation alter the soil hydrological conditions on steep concave slopes, rendering them susceptible to saturation. This may trigger debris flows during rainfall events. There is a need to restore forest cover on the fragile steep slopes and restrain local communities from opening up new areas for cultivation on critical slopes, particularly within the protected area. (C) 2011 Elsevier B.V. All rights reserved.