Effects Of Gravel Cover On The Near-Surface Airflow Field And Soil Wind Erosion

Gravel cover is a traditional farming practice to improve soil properties and advance soil productivity. In arid areas, gravel cover can directly affect the near-surface airflow field to inhibit the soil wind erosion rate (q). The effectiveness of gravel cover in wind erosion control has been recognized in practice, but there are few reports about experimental data. This study aimed to identify the mechanism under which gravel changes the nearsurface airflow field and q. The wind profiles at different positions around gravel roughness elements and q were measured under five inlet friction wind velocities (u*infinity), five gravel sizes (D) and five gravel coverages (GC) in a large wind tunnel, and an equation of q was established. The results showed significant differences among the wind profiles due to the effects of u*infinity, D and GC. Although the wind profile at any position did not represent the average state of the rough surface, the average wind profile of the different positions did. When the density of gravel roughness elements increased, the near-surface airflow changed from isolated-roughness flow to wake interference flow and skimming flow, which directly affected the spatial pattern and the rate of wind erosion. The equation of q established in this study not only integrated the effects of variables on the q, including D, GC, the average friction wind velocity (u*) and threshold friction wind velocity (u*t), but also represented the behavior of wind erosion being aggravated by gravel cover when GC <= 10 % and D >= 3.15 cm. This study can contribute to an understanding of the structural change to the near-surface airflow field and to the prediction of q on gravelcovered surfaces, which provides guidance information for rational utilization of gravel-covered fields in arid areas.