The objective of this study was to map the erosions that are occurring on the banks of Ribeirão São João in Porto Nacional - TO, these erosive processes come from the detachment and transportation of the soil particles, which can be deposited in the watercourse of the stream, causing the increase of the load in the streambed. Two erosions were the biggest. Soil characterization tests were done in each erosion. Monitoring its progress was made by pins erosion method, which was installed on the banks of those erosions. The accomplishment of monitoring made it possible to create graphs comparing precipitation and erosion. With this study it was achievable to check that the precipitation acts directly on the surface, increasing the erosive process, verifying that the soil type exerts a big influence on the process.