Soils on Steep Slopes

Abstract

Soils on steep slopes tend to be unstable due to natural and anthropogenic causes. The natural features of steep slopes that make them susceptible to failures and mass movement are gradient and shape of slope, geology, soil, vegetation and climate. Soils are more prone to mass movement in shallow and loose soils on impervious substratum, on steeper slopes, and under high intensity storms. The human actions that make soils on steep slopes unstable include development, settlement, shifting cultivation, deforestation, forest fires, soil mining, and other slope disturbances. Mass movement or landslides, which occur due to gravity, water saturation and water movement, have several forms: falls, creeps, slumps and earthflows, debris avalanches and debris flows, debris torrents and bedrock failures. These movements have on-site and off-site effects on properties, installations, house-holds, communications, crops, human lives and environmental health. Soils on steep slopes can be stabilized; or in other words, soil erosion in steeply sloping lands can be reduced by several mechanical, agronomic and agroforestry measures. Mechanical measures include drainage, contour bunds, silt fences, surface mats, grading and terracing, retention walls, slope reshaping, etc. Agronomic practices include contour cropping, contour strip cropping; and agroforestry methods are contour hedgerows, alley cropping and sloping agricultural land technology.