The Saco da Fazenda (SF) is a semi-enclosed coastal water body artificially made and inserted in the urban scenario of Itajaí city. The SF was created from the enterprise of retification of the access channel to the Port of Itajaí. The last curvature of the lower estuary was isolated from the main channel, and then creating the SF. Nowadays it is a depositional basin for the sediments from the Itajaí-Açu River and from small streams which drains the Itajaí City downtown. These small streams flow to the SF with no treatment at all, and, consequently, the water quality is low. Applying basic morphological data and hydrographic data from the SF and the lower Itajaí-Açu estuary, it was estimated the flushing time of the SF and the exchange level between the SF and the lower estuary. The flushing time is basically function of the tidal prism exchange, and the half-live was estimated as of the order of ‘few days’, or specifically 0,8 to 2,6 days varying the tidal height of neap and spring tide, respectivelly. The salinity of the SF the same of the upper layer of the lower estuary, and varies inversely and non-linearly related to the Itajaí-Açu river discharge, indicating higher level of eschange between them.