Using 137Cs measurements to quantify soil erosion and redistribution rates for areas under different land use in the Upper Kaleya River basin, southern Zambia

Although soil erosion is a serious environmental problem in many African countries, its assessment using traditional techniques is hampered by a range of problems. Reliable information on soil erosion rates is, nevertheless, an essential prerequisite for the design of targeted erosion and sediment control strategies. This contribution reports the use of 137Cs measurements to quantify medium-term (∼40 years) soil erosion and redistribution rates in both cultivated and uncultivated areas within the Upper Kaleya River basin in southern Zambia. Typical net soil erosion rates are estimated to be 4.3 t ha−1 year−1 for areas under commercial cultivation, 2.9 t ha−1 year−1 for bush grazing areas and 2.5 t ha−1 year−1 for areas under communal cultivation. Although these erosion rates reflect land use in these broad areas over the past 40 years, rather than present land use, they are nevertheless thought to also be representative of current conditions. The findings indicate that any attempt to develop effective erosion and sediment control strategies in the study area should involve all land use types and should aim to reduce both on-site erosion and sediment delivery from the slopes to the stream channel.