Soil erosion rates in tropical villages: A case study from Lake Victoria Basin, Uganda

In an effort to pinpoint the sources of sediment pollution in Lake Victoria, the contribution of sediment from compounds, landing sites, unpaved roads and footpaths is determined in the catchment of Nabera Bay and Kafunda Bay at the northern shore of Lake Victoria in southern Uganda. The volume of soil loss is determined in 36 compounds, 1 school and 1 landing site by comparing the original and current soil surface. The original soil surface is reconstructed using botanical and man-made datable objects. The soil loss rates are calculated by dividing the eroded soil volume by the age of the oldest datable object. Considering all compounds and landing sites in the study area, the average soil loss rate in compounds amounts to 107 Mg ha− 1 year− 1 (per unit compound) and to 207 Mg ha− 1 year− 1 per unit landing site. The soil loss from footpaths and unpaved roads is calculated by multiplying the total length of footpaths and unpaved roads with the average width and soil loss depth. The mean soil loss rate on footpaths is 34 Mg ha− 1 year− 1 and on unpaved roads equals 35 Mg ha− 1 year− 1. Compounds, landing sites, footpaths and unpaved roads occupy a small fraction of the study area (2.2%), but contribute disproportionately to the total soil loss (i.e. 85%) in the study area. It is concluded that compounds, landing sites, footpaths and unpaved roads are very significant sources of sediment pollution to Lake Victoria. This needs to be considered when designing strategies to reduce sediment production in the area.

Research Highlights
► Reconstruction of the original and current soil surface estimates the soil loss rate.
► Soil loss rate in compounds increases with the slope and decreases with the age of the compound.
► Compounds, footpaths and unpaved roads are mayor sediment sources in tropical environments.