The purpose of this research is to define the role of secondary forests of Northwestern Caucasus in soil erosion protection. These forests were grown after the logging in primary forests. Secondary forests in the watersheds of mountain rivers are deprived of protective properties of primary forests. This fact increases the risk of floods during heavy rainfall of high intensity. The study enables to establish the pattern of the influence of air dry mass of litter and grass cover on surface runoff and soil erosion. It is revealed that there is no surface runoff during intensive rainfall if the air dry mass of litter and grass cover exceeds 10 t/ha; and there is no soil erosion if the air dry mass of litter and grass cover exceeds 3.25 t/ha. Besides, the absence of soil erosion is characterized by the following indices: the content of organic matter in upper soil layer (7.6 %), coefficient of porosity (1.33), limit of flow-ability (53 %), and angle of interior friction between soil particles (22°). Breaking of these critical indices results in surface runoff and soil erosion during heavy rainfall. The results of this research allow forecasting storm runoff that will bring to floods in mountain rivers.
Key words: mountain river, secondary forest, surface runoff, soil erosion, litter.
