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In the Sahel field observations of wind-blown mass transport often show considerable spatial variation related to the spatial variation of the wind erosion controlling parameters, e.g. soil crust and vegetation cover. A model, used to predict spatial variation in wind erosion and deposition is a useful tool in the implementation of wind erosion control measures in the Sahel. The aim of this paper was to test two existing wind erosion models on spatial predictions of aeolian mass transport for Sahelian conditions. Field data from Burkina Faso were used to test an empirical (RWEQ) and a deterministic (WEPS) model.The revised wind erosion equation (RWEQ) poorly predicted maximum mass transport and so spatial predictions of mass transport were underestimated. Major constraints of RWEQ for application in the Sahel were the required non-eroding boundary and the fact that RWEQ assumes a more or less homogeneous field. It was concluded that RWEQ in its current state was not suitable for application in a Sahelian environment.With the correct roughness length (Z0), wind erosion prediction system (WEPS) correctly predicted friction velocity and initiation and cessation of mass transport. Furthermore, the model gave a reasonable prediction of the spatial distribution of mass transport at the research sites. It was concluded that WEPS in PCRaster is suitable for prediction of wind erosion in a Sahelian environment. A constraint of WEPS in PCRaster is that WEPS'' predictions of spatial variation in sediment transport are closely linked to the spatial variation in the input parameters. A good estimation of the spatial variation of the input parameters was required. Obtaining these might be an expensive exercise and could make its use in the Sahel difficult. [Copyright &y& Elsevier]

Abstract: Urban flood incidents induced by heavy rainfall in many cases entail flooding of combined sewer systems. These flood waters are likely to be contaminated and may pose potential health risks to citizens exposed to pathogens in these waters. The purpose of this study was to evaluate the microbial risk associated with sewer flooding incidents. Concentrations of Escherichia coli, intestinal enterococci and Campylobacter were measured in samples from 3 sewer flooding incidents. The results indicate faecal contamination: faecal indicator organism concentrations were similar to those found in crude sewage under high-flow conditions and Campylobacter was detected in all samples. Due to infrequent occurrence of such incidents only a small number of samples could be collected; additional data were collected from controlled flooding experiments and analyses of samples from combined sewers. The results were used for a screening-level quantitative microbial risk assessment (QMRA). Calculated annual risks values vary from 5×10−6 for Cryptosporidium assuming a low exposure scenario to 0.03 for Giardia assuming a high exposure scenario. The results of this screening-level risk assessment justify further research and data collection to allow more reliable quantitative assessment of health risks related to contaminated urban flood waters. [Copyright &y& Elsevier]

The co-ordinated European research project Wind Erosion and Loss of SOil Nutrients in semiarid Spain (WELSONS) was carried out from 1996 to 1999 to understand and predict the potential impacts of land-use change and management on soil degradation by wind erosion on agricultural land in Central Aragon, a semiarid desertification-threatened region in NE Spain. This paper gives a description of the project''s experimental approach and an overview of the main results regarding the effects of agricultural practices (i.e. conventional, CT, versus reduced tillage, RT) on surface conditions affecting wind erosion, the mobilisation of soil particles in the saltation layer and the atmospheric emission of fine dust into the suspension layer. The characterisation of the soil surface showed that soil erodibility by wind under RT was lower than that under CT. Though strong Cierzo wind events occurred during the experimental period, only a limited amount of material was available for wind erosion mainly due to soil crusting, a common feature in the area. In spite of this, saltation transport flux was measured at CT plots for different erosion episodes. Also, significant vertical emission of dust was observed only in the CT plot. Finally, the sandblasting efficiency calculated in the present experiment could be interpreted as the result of a higher binding energy for the particles of the silt loam experimental soil compared to soils with a lighter texture. [Copyright &y& Elsevier]