The aim of the research is to study erosion processes on the trails in mountain forest to determine allowable values of recreational loads. The study was carried out at the territory of Sochi National Park in 1998–2012. Soil erosion was investigated by simulating rainstorm events on runoff sites. Such indices as soil moisture, plasticity, texture, specific gravity and density, shear strength were determined in laboratory according to the established methodology. The study found that as recreational pressure increased the soil surface of trails was compacted to 1.27–1.68 g/cm³, and forest litter degraded gradually. The remains of forest litter on a trail facilitate to decreasing of soil density to the values of 0.88–1.15 g/cm³. At the same time soil erosion activates in the zone of tourist tracks along the both sides of a trail when recreational attendance is increasing. It wasn’t revealed the impact of water-physical properties of the surface soil layer on the characteristic of runoff and erosion (coefficient of determination between run-off coefficient and porosity was 0.005, and between erosion and porosity – 0.124). The close link between cohesion (varied in experiments from 0.032 to 0.072 MPa) and density of soil layer 0–20 cm was detected, coefficient of determination was 0.577. Allowable recreational attendance of a one hectare of a trail (site of 1 km long with a width of 10 m track zone) in recreational forests is established assuming allowable recreational density (depends on the forest type and slope steepness), number of days in tourist (recreational) season, duration of day load for one-kilometer section of a trail and the time for passing this site.
Keywords: soil erosion, mountain forest, trail, tourism, surface runoff, recreational load.
