Abstract

This study assessed the landslides hazard potential of the hill slopes of Ntcheu District Assembly. Landslides are known to cause lose of life and property, especially in settlements located in hilly areas. Since the Ntcheu District Assembly population is increasing at an annual growth rate of 3.1%, it became necessary that a study be conducted to aid the development of a sound physical plan for the Assembly. The slope stability factors studied included geology, soil, topography, precipitation and land use. Geology, topography and land-use were studied using aerial photographs (1:50 000); topographical maps (1:50 000) and through field traverses. Soil samples were also collected for the analysis of Liquid and Plastic Limits; Plasticity and Liquidity Indices and Bulk Density. Approximately 87% of the landslides identified occurred on the east facing slopes which had a gradient of 15° to 85°. This distribution was influenced by the bedding planes of the perthositic gneisses which dipped from 69° to 82°, sub-parallel to the general slope of the terrain. Soils are principally made up of sand particles, with very fine sand registering the highest figures of at least 65%. The Liquid and Plastic Limits ranged between 22.1-43% and 16.7-28.8%, respectively. The Liquidity and Plasticity Indices were generally low, an indication that these soils were sensitive to small water changes. These slopes have experienced high levels of deforestation between 1957 and 1991. This, together with a high rainfall of 636mm, contributed towards general slope instability. It was concluded that landslides in Ntcheu District Assembly were caused by a combination of factors. Geology was identified as a major factor of slope instability, especially where the gneissic foliations were sub-parallel to the slope of the terrain. The east facing slopes were found to be more susceptible to landslides than the west facing ones. It was then recommended that town planning for dwelling quarters in Ntcheu District Assembly should avoid high risk areas in order to safeguard lives and property. A reforestation program for these hill slopes was also recommended in order to stabilize the area.

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School	: School of Law, Economics and Government
Issued Date	: 2007

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