This paper presents the results generated by a hydrodynamic model applied to the Capote Channel in the urban area of Macaé / RJ. It also evaluates the flooding resulting from rainfall peaks in the micro-basin and spring tides in its estuary. The software used in the investigation includes a four-point implicit algorithm to complete resolution of Saint-Venant equations by finite difference method, with approximations to both derivations: time and space, originated from continuity and momentum. The solution to the flow rate and increase of the liquid surface was obtained for times and incremental distances along the channel. From the top-bathymetric information available, a digital terrain model was built and calibrated by measuring the limnimetric variations of the channel and flows, as well as by comparing the observed and simulated data for the conditions of peaks and troughs. The models simulated different scenarios, with special emphasis on those generated under high flow regime as they represent the most critical situation from an environmental approach and aim of this work. Results showed that, for these conditions, important areas close to that channel will be flooded.