Assessing the potential of unmanned aerial vehicles (UAVs) for terrace measurement in regeneration sites

Forestlands in Turkey are generally located on sloping terrain. Terrace construction is therefore required in afforestation and artificial regeneration sites. Terraces reduce soil and water loss by slowing surface runoff and support plant growth. The survival rate and growth performance of seedlings growing on terraced sites are generally higher than those on non-terraced sites. However, to achieve full success in afforestation and regeneration activities, site preparation and terrace construction must be carried out accurately and in accordance with technical standards. Traditional terrace measurement methods may result in time and labor losses, as well as measurement errors, especially on large and steep slopes. This has increased the need for faster, more accurate, and more cost-effective data collection methods in terracing projects. In recent years, unmanned aerial vehicle (UAV) technology has become an important tool in various forestry applications due to its advantages, including high-resolution spatial data production, low cost, and practical mapping capabilities. In this thesis, the potential of UAV technology for effective use in terrace measurements and terrace map production was investigated. To this end, UAV flights were conducted over terraced sites located in compartments 135 and 159 of the Şenyuva Forest Planning Unit (FPU), and orthophoto maps were produced. Based on these maps, several terrace parameters were measured using manual (on-screen digitizing) and automated (supervised classification) methods, and vector-based terrace maps were generated in Geographic Information System (GIS) environment. According to the results, the area coverage, total terrace length, average horizontal spacing between rows, and terrace density for the first and second projects in compartments 159 and 135 were 44,51 ha, 21,40 km, 7 m, 0,48 km/ha; and 22,83 ha, 12,19 km, 7 m, 0,53 km/ha, respectively. According to the 2026 unit price schedule, the time–cost analysis indicated that the measurement of the terraces in question could be completed in one day using the UAV mapping method, at a total cost of 38.919,39 TRY. The same task, when carried out using the traditional method, requires four workers working for three days and costs 46.500,00 TRY. However, these costs may vary depending on the project area, the total terrace length, and the geographical region. The findings demonstrated that the UAV mapping method is more economical for terrace projects larger than 50 ha. For projects smaller than 50 ha, the tradional method (ground-based measurement by field workers) may be preferred, provided that there is no urgency to complete the work and no significant occupational safety risk. This study also demonstrated that terrace lengths can be determined automatically through a supervised image classification method in GIS, rather than by manual on-screen digitization. This capability will further increase the speed of the UAV mapping method and should be preferred, especially in very large project areas covering hundreds of hectares. At the end of the study, it is concluded that terrace measurements and terrace map production can be effectively performed using UAV technology, and that terrace projects for afforestation and artificial regeneration activities can be completed in practical and efficient manners.