The aim of this study is to show the land-cover changes after the construction of a hydroelectric dam in the central south state of Mato Grosso (Brazil) and the impact of this from an environmental point of view. With the use of satellite imagery it is possible to show which areas of vegetation flood and those which are always clear of the water: for example: cerrado, pasture land, forest, culture. The multi temporal study permits us to evaluate and quantify the change in land cover in the flood plain after the creation of the dam. This study presents the evolution of the land use in the flood plain during the 17 years, before and after the construction of the dam (between 1992 and 2009).To allow comparisons and interpretations of data, the images used were provided by the sensor Landsat-TM with atmospheric and geometric corrections. The useful agricultural land on the floodplain increased more than 100%, in 17 years. The areas of cerrado or forest which became arable or pasture formed 22.5 % of the total territory. The implantation of the dam and the land-use changes which resulted have had and will continue to have major repercussions on the environmental and territorial organisation.