Capabilities of using UAVs and terrestrial photogrammetry to determine short-term soil losses in forest road cut slopes in semi-arid mountainous areas

The soil losses that are caused should be examined by monitoring the forest roads in the periods after they are built. In traditional soil loss determination studies that require intensive labour, due to difficulties in parcel setup, leaks from the connection points of the system, overflow of the material in the storage units and regular follow-up of the precipitation, etc., the system has its disadvantages. In this study, studies were carried out to evaluate the possibilities of using UAV and terrestrial photogrammetric methods, which are remote sensing techniques, and to determine the soil losses in forest road cut slopes in semi-arid mountainous areas. In addition, the advantages and disadvantages of the methods are discussed. A 100-meter section of the secondary forest road was chosen as the study area. Data acquisition was carried out by UAV and terrestrial photogrammetric methods in the period of May 2020-November 2020. In the results of the study, the volumetric deformation per unit area results, a -0.0060 m 3 m − 2 erosion amount and a 0.0046 m 3 m − 2 accumulation amount were determined by UAV. In addition, in the photogrammetric method, a -0.0050 m 3 m − 2 erosion amount and a 0.0031 m 3 m − 2 accumulation amount were found. When both methods were compared temporally, the processes took approximately 2 times longer in the terrestrial photogrammetry method. In addition, while the ground sampling distance of DEMs and orthophotos produced with the UAV was 2 cm, it was obtained as 1 cm in the terrestrial photogrammetry method, and terrestrial receptions were found to be 2 times higher resolution. According to the results obtained, the terrestrial photogrammetric method gives results that are more accurate in such studies.