Calibrating and validating the LISEM model for two data sets from the Netherlands and South Africa

11 tablesInternational audienc

Modelling soil erosion by water at the catchment scale

International audienc

Current Status on Flood Forecasting and Early Warning in Africa

An overview of the current state of flood forecasting and early warning in Africa is provided in order to identify future user needs and research. Information was collected by reviewing previously published research in the scientific literature and from institutional websites. This information was supplemented by data collected from a questionnaire sent to hydrological and meteorological institutions that were identified as potentially dealing with flood management issues in Africa. Results show that there are a significant number of institutional flood forecasting initiatives ongoing in Africa, but information regarding many of these initiatives is not easily accessible. Second, there is a clear need for improved flood forecasting and early warning in Africa. Third, the dissemination of existing flood forecasts and warnings to end-users and the public could be improved. It should be noted, however, that due to the difficulty in obtaining information regarding flood forecasting in Africa, the overview presented by the authors might be an underestimation of the current situation. Finally, the authors demonstrate the importance of developing a complementary flood forecasting and early warning system

Effects of crust and cracks on simulated catchment discharge and soil loss

Sealing, crusting and cracking of crusts of the soil surface has been observed in many parts of the world in areas with sandy, silty and loamy soils. Sealing and crust formation occurs under the influence of rain storm and drying weather. With prolonged drying, surface crusts might crack, leading to complex situations with respect to infiltration and runoff generation. Cracking of crusted loamy soils appears to be a general process. This study aims to measure the hydraulic properties of fully crusted and cracked-crusted areas and to evaluate the effects of these measurements on catchment discharge and soil loss in a loess region of the Netherlands, using the LISEM soil erosion model. Samples with minimum infiltration rates (fully crusted) and with maximum infiltration rates (cracked-crusted surfaces) were taken from fields with bare soil or winter wheat and their soil hydraulic functions were measured. The results of these measurements were used as input in the LISEM soil erosion model. Simulations of discharge and soil loss were done for each of these two land-uses and for two rain events. Additionally, simulated discharge and soil loss under actual recorded land-use were calculated. In all cases, soils with no surface cracks produced higher figures for discharge and soil loss than those where 10% of the surface crust was cracked. For a good interpretation of the results for soil loss, the spatial distribution of cracked-crusted areas and fully crusted areas has to be investigated in detail. To deal with cracked-crusted and fully crusted areas in simulation modelling, care has to be taken to accurately measure the soil physical functions representing the maximum and minimum infiltration rates. An assignment of these functions to calculation grids has to be made. As the LISEM model is capable of assigning different soil physical functions to each calculation grid, an improved prediction of the soil physical behaviour of the catchment can be simulated