Transformation of slope microrelief across an unused mountain forest road – Analysis over an 8-year period (Tatra Mts, Poland)

The main aim of the paper was to determine the rate of morphogenetic processes on a road that had been abandoned and the directions of road development. The research was conducted in the Lejowa Valley in the Tatra Mountains in southern Poland. To determine the rate of changes, we used data from Terrestrial Laser Scanning (TLS) (2019–2020) and unmanned aerial vehicle (UAV)-derived photogrammetric data (2022–2023). The research showed that, between the two study periods (2019–2020 and 2022–2023) the difference in erosion rate was not statistically significant within the roadbed but was significant for the roadbanks. The net change in roadbed erosion rate was from −432 m³ ha⁻¹ yr⁻¹ (2019–2020) to −308 m³ ha⁻¹ yr⁻¹ (2022–2023). The net change for roadbanks in each period was erosion and equalled −247 m³ ha⁻¹ yr⁻¹ (2019–2020) and −146 m³ ha⁻¹ yr⁻¹ (2022–2023). Changes across the alluvial fan at the end of the road in 2022–2023 were an accumulation of +260 m³ ha⁻¹ yr⁻¹. The development of microrelief within the road strictly depends on the course of deep and lateral erosions, which is modified by the road intercepting of additional runoff from the denudation valley and springs, by flow being redirected by debris such as uprooted trees, or by exposed bedrock.