Itapocú Inlet, Brazil. A study of the hydrodynamics and morphology

Despite the abundant appearance of coastal inlets in Brazil, there are not many studies carried out involving them. UNIVALI (Universidade do Vale do Itajai) has set up an investigation program to gain more insight into the hydrodynamic and morphologic behaviour of inlets along the Brazilian coast. The main goal of this study is to investigate the hydrodynamic behaviour and morpho- logy for ItapocAo inlet, situated in the south of Brazil. As a sub-objective this study aims to give answer to the question what happens with the hydrodynamic and morphologic processes in case the inlet throat is stabilized with breakwaters. The hydrodynamic behaviour of ItapocAo inlet is difficult to characterise. For that reason the changing inlet characteristics were obtained from a Delft3D model. The influence of the ocean is large during spring tide and periods of minor river discharge. However when the river discharge is large, or during neap tide, the basin is mainly regulated by the river. The reason for this continuing changing characteristic is that tidal prism and river discharge (during half a tidal cycle) have the same order of magnitude. The changing equilibrium between these two most important processes drives the morphology and hydrodynamic of the whole basin. The mouth of ItapocAo inlet is very unstable. In the last 10 years, strong wave induced, northern directed, longshore sediment transport has shifted the entrance about 100 m per year to the north.