Alteration of a natural ecosystem can physically, chemically and biologically affect a determined area. Therefore, this study aimed to evaluate the relation between the hydrology, soils and vegetation existing in an area changed by the implantation of a Hydroeletric Power Plant (HPP) in the municipality of Roque Gonzales, Rio Grande do Sul state. The study area was composed of three samples located downstream of the dam. This analysis was performed by the points method to verify the existence of similarity patterns between the vegetation, inundation levels and edaphic soil characteristics of each sample. As a result, greater floristic similarity was observed between the species as a relation of the spatial location with inundation levels. Thus, we can conclude that the vegetal establishment in the study area is under the direct influence of waterflow variation levels from the HPP, which contributes to defining species adaptability to these specific conditions, among others.