In the present research project, the hydrological response of green roofs was analyzed in terms of the reduction of the peak flow due to changes in the bottom slope, for this a model of a green roof and a lysimeter with their respective waterproofing layers were designed. geotextile, drainage, substrate and vegetation. Thanks to this, it was possible, through the lysimeter, to know the evapotranspiration of the vegetation and reach the conclusion that the reductions provided by this process are considered negligible. Through the green roof, different reductions with different slopes were obtained, in order to verify the hypothesis that was mainly held, which mentioned that the lower the slope, the greater the reduction in flow and vice versa