Characterizing sand transport with various micro-ridge spacings and heights

In arid regions, the use of ridge cover as a traditional agricultural strategy has been effective in mitigating soil wind erosion. However, few studies have focused on the sand transport characteristics of different micro-ridge spacings and heights. This study aimed to identify the mechanism by which ridges change the near-surface sand transport. In a controlled wind tunnel environment, the aeolian sand flux structure and sand transport flux (qz) at heights from 0 to 0.7 m were measured. The results showed that, compared with no ridges, ridge covering could significantly modify the structure of aeolian sand flux near the surface, yielding a substantial reduction in the proportion of sand transport to the total sand transport in the 0- to 0.1-m height layer. In the absence of ridges, blown sand was mainly concentrated in the 0- to 0.1-m height layer, and qz decreased exponentially as the height increased. With various micro-ridge spacings and heights, when H was less than 0.1 m and L was more than 15H, the blown sand also remained concentrated in the 0- to 0.1-m height layer, and qz decreased exponentially as the height increased. When H increased to 0.15 m from 0.1 m and L decreased from 15H to 5H, the height of the blown sand was concentrated in the 0.3- to 0.4-m layer. The blown sand layer of most ridge structures was concentrated at a height of 0.1-0.4 m, and the structure of the aeolian sand flux resembled an 'elephant nose effect'. The total sand transport rate of all ridge structures was significantly lower than that with no ridges, indicating that a reasonable ridge structure can effectively prevent wind erosion. The results confirmed that the variation of sand transport flux with height could be divided into two cases: one shows that sand transport flux decreases exponentially with increase of height; whereas, the other shows that sand transport flux increases with increase of height below critical height and decreases exponentially with the increasing of height above critical height, known as 'elephant nose effect'. These results help to further recognizing the process and mechanism of wind erosion in ridge farmland. image