Erosion hazard within the river Nyando catchment, lake victoria basin, Kenya.
2005
Waruru, B.K.(KARI-Headquarters, Nairobi, Kenya) | Wanjogu, S.N.(KARI-Headquarters, Nairobi, Kenya) | Njoroge, C.R.K.(KARI-Headquarters, Nairobi, Kenya) | Wagate, P.N.(KARI-Headquarters, Nairobi, Kenya)
The River Nyando catchment together with . River Nzoia catchment contribute more than t 50% of the Kenyan waters into Lake I Victoria. Environmental degradation within I the catchment has been a major contributor : to ecological degradation, low crop I productivity, poor water quality and . eutrophication of the lake. The physiography t of the catchment comprises highlands and lowlands areas where land use varies with topography, soil type, and agroclimatic conditions. The objective of the study was to establish the erosion hazard within the different soil mapping units and categorise the area into hotspot, blackspot, yellowspot, greenspot and whitespot as areas under very severe, severe, high, moderate and, low erosion hazard respectively. Erosion hazard classification was based on rating steepness of slope, relevant soil physical and chemical properties, surface cover and landuse. Hotspot areas occur on mountainous and hilly areas and cover about 5%, black spot occur on the hills, footridges and footslopes and cover 17%, yellowspot occur on lower parts of the foot slopes, upland and upper " piedmont plains and cover 51 %, greenspot occur on the plains covering 24% and white spot are the depression areas and swamps and cover 4% of the study area. Human activities including permanent settlements into the forest reserves, introduction of annual crops in the steep forest or tea areas, overstocking in the lowland areas has enhanced erosion hazard. In view of the importance of the catchments to the viability and sustain ability of the wetlands and the lake ecosystem, urgent area specific measures of catchments protection and conservation through sustainable land use management are necessary.
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