The riparian forests develop in river valleys. Because of their soils fertility about 90% of the area occupied by forests of this type in the past has been transformed into farmlands. We studied hydrological characteristics conducive for development of riparian forests vegetation in small lowland river valley. Our study revealed limited role of the flooding phenomena in formation of these forests: average duration time of flooding amounted to 10 days per year. Frequent and long−lasting floods inhibit regeneration of the riparian forests on ex−meadows and prolong dominance of non−forest vegetation in the area adjacent to river channel.