Trail erosion assessment and monitoring in natural areas: a comparison of traditional and high-resolution topographic surveying methods.

Recreational trails in natural areas are subject to erosion, particularly when poorly planned and under visitation pressure. Accurate erosion monitoring is essential for sustainable trail management, especially in quantitative analysis requiring objective parameters of accuracy and precision. This study compares the feasibility of five erosion measurement methods applied to forest trails. The methodological approach included two traditional techniques: (i) cross-sectional area (CSA) and (ii) maximum depth (MaxD); and three high-resolution topographic (HRT) techniques: (iii) terrestrial laser scanning (TLS), (iv) structure from motion photogrammetry using an action camera (SfM-AC), and (v) an unmanned aerial system (SfM-UAS). Repeated field surveys enabled estimation of short-term erosion, in addition to historical erosion, which was assessed by comparing reconstructed pre-trail topography with current conditions. Notably, to our knowledge, this is the first study in trail management to apply check points (CPs) to quantify vertical uncertainty and integrate it into a DoD-based analysis, thereby improving the detection and interpretation of erosion processes. Results show that while CSA is practical and low cost, it may introduce undetected errors, as it does not allow for quantifying measurement uncertainty. In contrast, HRT methods produced georeferenced and accurate outputs to support spatial and temporal analyses and yielded consistent estimates of surface change. The methods differed in terms of time, financial costs, logistics, and required level of expertise. Among HRT approaches, SfM-AC emerged as the most feasible, balancing affordability, operational simplicity, and technical performance. These findings underscore the need to match erosion measurement methods to trail conditions and project objectives, and highlight the potential of photogrammetry for monitoring trail erosion in diverse environments.