With a focus on water sustainability, Fluminense Federal University developed the Macacu Project, which included the integrated management of water resources in the basin of the Guapi-Açu River. One component of the project was the simulation of the rivers’ flow patterns, supported by topographic and bathymetric surveys conducted in 2008. New surveying services were provided in 2012. From the data generated, new simulations with HEC-RAS (1D) and IBER (2D) models were performed by combining the use GIS. Hydrographs with return periods of 2, 10, 20 and 50 years were simulated and the results showed that areas potentially most affected by flooding are pasture and forest, but flooded spots were observed also in some constructed areas. The 2D model produced results more compatible with what would occur naturally in floodplains, but it requires a large amount of data and lengthy processing time.