Wind erosion rate for vegetated soil cover: A prediction model based on surface shear strength

Abstract Vegetation is regarded as the most effective measure for soil erosion control and sand control projects, which plays an important role in controlling soil wind erosion and sand disasters in arid and semiarid regions. Most of the existing models for soil wind erosion rate prediction are based on empirical results that consider factors such as vegetation coverage and wind speed but have rarely investigated the wind erosion rate from the shear strength perspective, which is also an important reason why it is difficult for existing wind erosion models to be popularized. In fact, the presence of vegetation alters the distribution of the near-surface airflow field and thus profoundly changes the magnitude and spatial distribution of shear stress generated by airflow on soil particles. According to existing theories, it is very difficult to describe these processes. Although the shear stress on a vegetation-covered soil surface may be measured using existing observation techniques, difficulties in technology make it impractical for conducting at a large scale. Consequently, research that combines soil wind erosion and the shear strength of vegetation-covered soil surfaces has rarely been reported. Therefore, the prediction of discrete wind erosion rates considering the uneven spatial distribution of the airflow field has gradually become a new trend in the study of the wind erosion of vegetation-covered soil surfaces. In this study, the model for the airflow field of a single plant and the conversion model for the airflow field from a single plant to multiple plants were examined, based on which parameters, such as vegetation characteristics and plant density in wind tunnel tests, were combined to simulate the spatial distribution of the airflow field over vegetation cover surface under four different vegetation coverages. A method for calculating the effective shear strength of the vegetation-covered soil surface was proposed, and the effective shear strength of the surface with different vegetation covers was determined. The effective shear strength of the vegetation-covered soil surface was found to increase with increasing wind speed, decrease with increasing vegetation coverage, and decrease with increasing particle size. On this basis, the relationship between the wind erosion rate q and the effective shear strength τ eff ¯ of the vegetation-covered soil surface was quantitatively established as q = k d / g · τ eff ¯ , where k = 114.02. Findings of this study help to explain the wind erosion dynamics of a vegetation-covered soil surface and can also provide a solid foundation for constructing a wind erosion prediction model based on the theory of dynamics.