Hydrological Hazards in the Lower Basin of Aries River. The first part of this work presents the freezing and thaw phenomena, their frequency and their effects on the studied area. These phenomena are presented in sections indicating their economical and social effects on the major economical institutions (industry, water supply plants). The second part of the work includes a short analysis of the changes that appear in the riverbeds after the floods in the studied period. At the end there are some charts that present the transverse profile drawn before and after the floods. The closure refers to the solid run-off from the slopes and to the degree of vulnerability of the studied area to the hydrological risk phenomena.