Human activity and related land use change are the primary cause of accelerated soil erosion, which has substantial implications for nutrient and carbon cycling, land productivity and in turn, worldwide socio-economic conditions. Here we present an unprecedentedly high resolution (250 × 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modelling and census data. We challenge the previous annual soil erosion reference values as our estimate, of 35.9 Pg yr⁻¹of soil eroded in 2012, is at least two times lower. Moreover, we estimate the spatial and temporal effects of land use change between 2001 and 2012 and the potential offset of the global application of conservation practices. Our findings indicate a potential overall increase in global soil erosion driven by cropland expansion. The greatest increases are predicted to occur in Sub-Saharan Africa, South America and Southeast Asia. The least developed economies have been found to experience the highest estimates of soil erosion rates.

Since eroded sediments are produced from different sources distributed throughout a basin, sediment delivery processes at basin scale have to be modelled by a spatially distributed approach. In this paper a new theoretically based relationship is proposed for evaluating the sediment delivery ratio, SDR_i, of each morphological unit, i, into which a basin is divided. Then, using the sediment balance equation written for the basin outlet, a relationship between the basin sediment delivery ratio, SDR_W and the SDR_i is deduced. This relationship is shown to be independent of the soil erosion model used. Finally, a morphological criterion for estimating a coefficient, β, is proposed.

Understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over flexible bottom vegetation is experimentally studied. A two-dimensional-acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations, discharges, and flume slopes. The influence of vegetation concentration and the depth/vegetation height ratio on the measured velocity profiles is analyzed. All measured velocity distributions are S-shaped and exhibit a three-zone profile. The relationship between the velocity distribution and the turbulence intensity distribution is also analyzed. The characteristics (inflection point, maximum value, asymptotes) of the measured velocity distributions and the results of the previous investigators are used to select an analytical expression for the shape of the velocity profile. A theoretical velocity profile is deduced using the classical Prandtl’s mixing length approach wit...

Because eroded sediments are produced from different sources throughout a basin, it is often advantageous to model sediment delivery processes at basin scale using a spatially distributed approach. In this paper, a sediment delivery distributed (SEDD) model applicable at morphological unit scale, into which a basin is divided, is initially proposed. The model is based on the Universal Soil Loss Equation (USLE), in which different expressions of the erosivity and topographic factors are considered, coupled with a relationship for evaluating the sediment delivery ratio of each morphological unit. Then the SEDD model is calibrated by sediment yield and rainfall and runoff measurements carried out, at annual and event scales, in three small Calabrian experimental basis. At event scale, the analysis showed that a good agreement between measured and calculated basin sediment yields can be obtained using the simple rainfall erosivity factor; the agreement is independent of the selected equations for estimating the topographic factors. The analysis developed at annual scale showed that the model reliability increases from the event scale to the annual scale. Finally, a Monte Carlo technique was used for evaluating the effects of the uncertainty of the model parameters on calculated sediment yield.