Camacho inlet southern Brazil – Instability causes and user conflicts
Abstract Inlet stabilization is a common practice in Brazil, as it is worldwide. In this paper we present results of the analysis of the stabilization practices of the Camacho Inlet, located in Santa Catarina State, southern Brazil. This inlet is maintained intermittently, in accordance with a regime designed to benefit both local fishermen and rice farmers. Fishermen require this inlet to be open as a navigation channel during the fishing season; rice farmers needs it closed during the irrigation period to allow the pumping of fresh water from the Congonhas River which drains into the Camacho’s backbarrier lagoon. An additional complication arises from the tendency of this inlet to close naturally due to infilling by dune migration. Aerial images spanning a 65 year time period (1938–2003) were analyzed, demonstrating the variability in the inlet’s width between 0 (closed) and 360 m. The analysis of inlet stability and user needs indicate that an appropriate solution is the implementation of an annual inlet dredging program in the austral autumn. This would allow for the inlet to remain open from May to September and then close naturally for the rest of the year, providing for a backbarrier fresh water reservoir during the irrigation period.
Santa Catarina Beach Systems
The Santa Catarina coast is located in southern Brazil between 26° and 29.3°S. The coast trends south then southwest for about 430 km, and contains 922 km of open coast and bay shoreline, with 246 sandy beaches occupying 60 % of the shore. Based on geology and orientation the coast is divided into five coastal provinces, each of which contains a different suite of beach systems. The provinces and their beaches range for the highly embayed Penha to Baia Norte province which is dominated by short low energy reflective beaches, to the exposed high energy Cabo Santa Marta to Torres province which has long near continuous multi-barred dissipative beaches. This chapter reviews the provinces and their beach systems including spatial and temporal controls, as well as beach erosion, hazards and safety.
HYDRAULICS AND SEDIMENTARY STABILITY OF COASTAL INLETS
A method is presented for investigating the stability of coastal inlets against closure due to transport and deposition of sand in the inlet cross-section. The method utilizes earlier contributions by: (1) Keulegan representing the hydraulics of inlets, (2) O'Brien which describes an equilibrium relationship between the cross-sectional area of an inlet and the bay tidal prism, and (3) Escoffier which relates to the stability of an inlet under changes in conditions which tend to close or enlarge an inlet. A "stability index" is defined which incorporates the buffer storage area available in the inlet cross-section, prior to the onset of closure and also includes the capability of the inlet to transport excess sand from its cross-section. In order to apply the method, geometric and hydraulic data representing the inlet are necessary; the minimum data required include a survey of the inlet throat cross-section and the lag between high (or low) water in the ocean and the following slack water in the inlet. In addition, it is necessary to conduct measurements or make assumptions concerning the minor and gradual hydraulic loss coefficients. Based on assumed depositional patterns in the inlet, the method is applied to five real inlets and the stability indices are presented.