The HEC-RAS hydraulic modeling software is described as a tool to determine flood zones in populated centers near natural channels and the case of the population of Tobia-Cundinamarca is presented where data concerning information related to the measurement of flow rates of IDEAM station 23067060 rivers located in Tobia between the period of (1975 and 2015), which feeds the model of the HecRAS tool, this information added to archives of geographic information of the area processed with the Ras- MAPPER allows a hydraulic simulation to determine the flood areas of the sector.