Evaluation of traditional rain-fed agricultural terraces for soil erosion control through UAV observation in the middle mountain of Nepal

Abstract

The livelihood of most people in the mountainous region of Nepal depends on traditional farming practices. Farmers modify their lands by constructing narrow outward sloping terraces to control soil erosion in the mountain and hill of Nepal. However, preliminary observation reveals that farmers adopt different strategies to manage outward sloping terraces according to the amount of rainfall so as to avoid the impact from soil erosion due to excessive rainfall. Thus, this study aims to evaluate the effectiveness of the traditional practice of topographic management of outward sloping rain-fed terraces to control soil erosion. The study makes a comparative analysis of topographic values of terraces and the estimated rates of soil erosion in different rainfall regions. Topographic values were derived from high spatial resolution (20 cm) Digital Elevation Model (DEM) data acquired by Unmanned Aerial Vehicle (UAV). Revised Universal Soil Loss Equation (RUSLE) was used to estimate the rate of soil erosion based on this high-resolution DEM together with other required variables. The research revealed that the traditional practice of topographic modification is highly effective to control soil erosion, as no significant differences in the rates of soil erosion were found even though the amount of rainfall considerably varies at different sites.