Surface Runoff Generation and Soil Loss Under Different Soil and Rainfall Properties in The Uluguru Mountains, Tanzania

Abstract

AbstractWater erosion is one of the main concerns driving land degradation in mountainous areas throughout the world, and its characteristics change widely with soil and climate conditions in different locations. To investigate the effects of soil and rainfall properties on surface runoff and soil loss, we installed runoff plots (width 0·8 m × slope length 2·4 m) enclosed by corrugated iron sheets, and evaluated water budgets for rainfall, surface runoff and soil moisture for every rainfall event over a rainy season at four sites (designated NY, TA, SO and MA) in the Uluguru Mountains of Tanzania. Two of the sites, NY and TA, were located in mountainous areas and had steep slopes and higher rainfall amounts, while the two foothill sites, SO and MA, were flatter and with coarser textures. Runoff amount was related to rainfall amount, but also to infiltration capacity. Runoff amounts in mountainous areas were higher than in foothill sites while runoff ratio was low at sites with high permeability in the surface layer, TA and MA. Sediment concentrations and soil loss were basically enhanced by high rainfall amount and intensity at mountainous sites. Soil texture also controlled the erodibility of soils; MA had twice the soil loss of SO owing to sandy soil despite similar rainfall amounts at MA and SO. Our results show that the high rainfall amounts in the mountainous areas and high susceptibility of sandy soils to erosion enhanced soil loss by water erosion in this study. Copyright © 2016 John Wiley & Sons, Ltd.