Low-cost techniques for soil erosion monitoring on mountain trails

Abstract. This study presents low-cost techniques for monitoring soil erosion on mountain trails within the context of the HUMANITA project, which focuses on mitigating the environmental impacts from recreational activities in protected areas. Monitoring erosion in mountain environments poses several challenges that must be considered to select optimal techniques, such as limited accessibility, instrument portability, achievable level of detail, absence of data connectivity and Ground Control Point establishment. In addition, soil erosion is a widespread issue that requires surveys over large areas and must be repeated periodically to ensure accurate assessment and track changes over time. Consequently, the cost and ease of use of surveying equipment are critical.
Six protected areas in Italy and Central Europe were selected as pilot sites. Three scenarios were explored, each characterized by different spatial extents and level of details required for erosion assessment: detailed analysis of small areas (scenario 1), narrow forest trails (scenario 2), and broad open areas (scenario 3). Scenario 1 employed high-precision techniques such as Terrestrial Laser Scanning and close-range photogrammetry to capture micro-scale changes. Scenario 2 utilized spherical photogrammetry and UAVs to survey narrow, vegetated trails with high resolution and accuracy. Scenario 3 focused on UAV photogrammetry for monitoring large areas. Key challenges included multi-epoch data co-registration, establishing stable ground control points, and ensuring and assessing surveys repeatability. The results highlight the capabilities, limitations, and cost-effectiveness of these geomatics techniques, providing practical guidelines for sustainable trail management and erosion monitoring in protected mountain areas.