Soil erosion risk assessment of the Keiskamma catchment,South Africa using GIS and remote sensing |
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| Authors: | Paidamwoyo Mhangara Vincent Kakembo Kyoung Jae Lim |
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| Institution: | (1) Department of Geosciences, Nelson Mandela Metropolitan University, Port Elizabeth, PO Box 77000, South Africa;(2) Department of Regional Infrastructure Engineering, Kangwon National University, Kangwon, Chuncheon, Korea |
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| Abstract: | This paper examines the soil loss spatial patterns in the Keiskamma catchment using the GIS-based Sediment Assessment Tool
for Effective Erosion Control (SATEEC) to assess the soil erosion risk of the catchment. SATEEC estimates soil loss and sediment
yield within river catchments using the Revised Universal Soil Loss Equation (RUSLE) and a spatially distributed sediment
delivery ratio. Vegetation cover in protected areas has a significant effect in curtailing soil loss. The effect of rainfall
was noted as two pronged, higher rainfall amounts received in the escarpment promote vegetation growth and vigour in the Amatole
mountain range which in turn positively provides a protective cover to shield the soil from soil loss. The negative aspect
of high rainfall is that it increases the rainfall erosivity. The Keiskamma catchment is predisposed to excessive rates of
soil loss due to high soil erodibility, steep slopes, poor conservation practices and low vegetation cover. This soil erosion
risk assessment shows that 35% of the catchment is prone to high to extremely high soil losses higher than 25 ton ha−1 year−1 whilst 65% still experience very low to moderate levels of soil loss of less than 25 ton ha−1 year−1. Object based classification highlighted the occurrence of enriched valley infill which flourishes in sediment laden ephemeral
stream channels. This occurrence increases gully erosion due to overgrazing within ephemeral stream channels. Measures to
curb further degradation in the catchment should thrive to strengthen the role of local institutions in controlling conservation
practice. |
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