The stability of the Camacho inlet, Santa Catarina, Brazil

In the south of the State of Santa Catarina lies the Camacho Lagoon (28 degrees 36'S and 048 degrees 54'W), which is connected to the Atlantic Ocean by a single channel known as the Camacho Inlet. The inlet is not permanently open, which impedes fishing activity inside the lagoon. The State Government therefore decided to build two groins at the mouth of the inlet, with the aim of stabilizing it. However, even with the groins in place, the lagoon still shows an inconsistent profile. This research seeks to analyze the stability of the inlet, the factors at work, and the efficiency of the groins. This study of the stability of Camacho Inlet involved empirical criteria based on (1) the relationship between tidal prism and Cross-section area; (2) the relationship between maximum velocity and cross-section area and (3) the relationship between response ability and cross-section area. Taking into account the environmental aspects of the area and its fluctuations, it is clear that the efforts to keep the Camacho Inlet open were in vain. The Camacho Inlet presents a strong profile of instability, with cross-section area and flow velocity values below those necessary to generate stable conditions in the system. The channel is only open during periods of intense river discharge and/or meteorological tides; once the inlet is open, the flow is maintained by the semidiurnal tide, which is not strong enough to remove the sediment deposited in the channel. This condition, associated with the high rate of sediment transport in the region, causes the channel to close completely.