Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 2011
Publication Date: September 14, 2011
Citation: Eitel, J.U., Williams, C.J., Vierling, L.A., Al-Hamdan, O.Z., Pierson Jr, F.B. 2011. Suitability of terrestrial laser scanning for studying surface roughness effects on concentrated flow erosion processes in rangelands. Catena. 87(2):398-407. Interpretive Summary: Surface roughness is thought to affect rill erosion - a major mechanism of soil loss on rangelands. However, quantifying surface roughness in the field at appropriately fine spatial scales has been elusive. Rapid, objective, and repeatable methods are therefore needed to accurately measure surface roughness across a range of spatial scales to advance our understanding and modeling of rill erosion processes. This study evaluated the suitability of terrestrial laser scanning (TLS) technology to measure surface roughness and its relationship with rangeland erosion from rill processes. TLS derived surface measurements were well correlated with measured rill erosion, but the relationship was dependent on the spatial scale of the roughness measurements. The study demonstrates that TLS technology may represent a useful tool for scientists and land managers assessing surface roughness related to rangeland overland flow and erosion processes.
Technical Abstract: Surface roughness is thought to affect concentrated flow erosion - a major mechanism of soil loss on disturbed rangelands. However, quantifying surface roughness in the field at appropriately fine spatial scales is laborious and the scale at which to conduct meaningful roughness measurements is difficult to discern. Rapid, objective, and repeatable field methods are therefore needed to accurately measure surface roughness across a range of spatial scales to advance our understanding and modeling of concentrated flow erosion processes. Surface roughness can be derived from surface topography mapped at the sub-cm level using a field-portable terrestrial laser scanner (TLS). To test the suitability of terrestrial laser scanning for studying surface roughness effects on erosion processes in rangelands, we used concentrated flow simulation techniques at 8.5 m2 plots that were randomly placed at rangeland sites in southeastern Oregon and southwestern Idaho, USA. Local surface roughness (locRMSH) was calculated as the standard deviation of TLS mapped surface heights within moving windows varying in size from 30x30 to 90x90 mm. The mean locRMSH of the eroded area and entire plot were negatively correlated (r2> 0.71, RMSE < 95.97 g min-1, and r2 > 0.74, RMSE < 90.07 g min-1, respectively) with concentrated flow erosion. The strength of the locRMSH - erosion relationship and regression model parameters were affected by the moving window size, emphasizing the scale dependence of the locRMSH - erosion relationship. Adjusting locRMSH for slope effects decreased the strength of the locRMSH - erosion relationship from r2 < 0.83 to < 0.26. Our results indicate that TLS is a useful tool to enhance our current understanding of the effect of surface roughness on overland flow erosion processes and advance hydrologic and erosion model parameter development. Further research is needed to evaluate the locRMSH - concentrated flow erosion relationship over a wider range of soil properties, surface conditions, and spatial extents.