Effects of Rainfall-Runoff on Soil Surface Roughness and Erosion Processes

Soil erosion of hills affects the productivity of agriculture lands and threatens our earth environment. There are several factors that trigger and sustain soil erosion. Some of the key mechanisms are believed to be: (i) climate; (ii) soil type; (iiii) soil surface roughness; (iv) cropping; and (v) land management practices. This study examines the role of the rainfall-runoff on soil surface roughness and the transport/deposition of the eroded soil. Surface roughness is related to management practices and has been one of the factors that have not received considerable attention. One hindrance of previous studies was the lack of a system and robust methodology for performing adequate acquisition of the soil surface micro-topography. The required resolution in order to adequately describe the soil surface micro-topography is on the scale of a millimeter. Most of the traditional measurement techniques (e.g., roller chain, erosion pins), though, can not provide such a high spatial resolution. Thus, a state-of-the-art laser scanner technique was utilized, providing a resolution of 0.5 mm. Laser scanners use triangulation to measure surface elevation. A laser beam is projected vertically onto the surface and a line camera detects the light spot reflected from the surface. Because of the fixed camera-laser geometry, the surface height is estimated using a simple calibration procedure. The surface heights for the entire soil surface were then imported into the ArcGIS 9.2 software in order to obtain the Digital Elevation Model (DEM), while the built-in Arc Hydro tools were used next to attain the drainage networks, flow direction, flow accumulation, stream definition, and stream segmentation.