A bridge located in Pto. Lavalle, Chaco province at the Bermejo river, Argentina has produced morphological variations on the river evolution both upstream and downstream of the structure. It is observed that the bridge controls the stream evolution locally. Two characteristic lengths are found; upstream of the bridge, the length is denominated Λu, which represents the region where the presence of the bridge disrupts and constrains the freely meandering migration pattern of the stream producing changes on curvature and orientation of the bends. In the other hand, downstream of the bridge, Λd is the distance where the lateral migration of pre-existent bends have been diminished or almost eliminated. Herein, the model RVR Meander (Abad & Garcia, 2006) was used to characterize and analyze the migration of the Bermejo river and the influence of the bridge on the morphological processes. The model allows estimating the lateral and longitudinal migration rate of the stream among other parameters. The model also predicts the migration in time of the stream by coupling a hydrodynamic and bank erosion model. In this study, the validation of the model for the Bermejo river is shown together with the estimation and characterization of the lengths Λu and Λd. This study sets the basis for future plans on applying more sophisticated models in a region near the bridge.