The Effect of Different Soil Erosion Stages on Surface Roughness under Simulated Rainfall

Soil erosion is a complex and dynamic process. Correspondingly, as one of the main factors of soil erosion, Soil surface roughness (SSR) is also complex and dynamic in the process of soil erosion. Soil erosion process was divided into four stages: before the rain (S₀), splash erosion stage (S₁), sheet erosion stage (S₂), rill-gully erosion stage (S₃). The objective of this research is to make it clear how soil erosion affects SSR in detail through evaluating the changes of SSR in different soil erosion stages. Soil beds were operated by four different tillage systems to shape four different surface conditions: artificial shallow ploughing (ASP), artificial deep ploughing (ADP), contour ploughing (CT), and no tillage treatment as (CK). Thirty six experiments were conducted under simulated rainfall. Several indices including the standard deviation (S_d) of soil surface elevation, SSR, and the chain method index C_r' were measured before and after each rainstorm. The result shows that: For ASP, ADP, and CP tillage systems, in splash erosion stage, all the, S_d SSR, and Cr' decrease significantly; in sheet erosion stage, S_d, SSR, and C_r' continue to decrease but the quantity of change is small; in rill-gully erosion stage, S_d, SSR and C_r' increase obviously. For CK, all the S_d, SSR, and C_r' increase all the time. This means splash erosion and sheet erosion can decrease SSR, but the degree is different. Rill-gully erosion can increase SSR, make soil surface rougher than before.