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.
Quantification of inlet-related hazards in barrier island systems. An example from the Ria Formosa (Portugal)
Abstract Determination of inlet hazard areas (IHAs) is important for the management of barrier island systems such as the Ria Formosa. An IHA is an area of natural importance that can be easily destroyed by inlet-related processes and covers the land adjacent to inlets [CAMA, 2004. Handbook for Development in Coastal North Carolina. Division of Coastal Management from the North Carolina State Department of Environmental and Natural Resources. http://www.nccoastalmanagement.net/Handbook/contents.htm , (accessed 07.04)]. One parameter is defined in order to quantify the extension of the inlet-associated hazards within a barrier island system. This parameter, the minimum inlet hazard area (IHA min ), represents the extent of the minimum area that should be taken into account when analysing inlet-associated hazards and is determined using the following criteria: (a) inlet maximum width; (b) inlet migration path and (c) existence of frequently overwashed areas that can be related to present or historic inlets. The calculation of the IHA min was applied to the Ria Formosa barrier island system (southern Portugal) for a time scale of decades. For the Ria Formosa the IHA min represents approximately 45% of the total length of the system. Most of the occupied areas within the barrier chain are located inside the IHA min . Changes in the configuration and number of inlets of the system would modify the total IHA min calculated for the entire area. However, assuming that the typical migration patterns identified for the system do not change, the herein proposed methodology can still be applicable to calculate the new associated IHA min . This study showed that other studies should be considered in future work including: (i) quantifying buffer distances on both sides of the IHA min and (ii) analyses of the inland extent of the hazardous areas. The IHA min is an easy-to-use parameter that could be quantified for other inlets located in other parts of the world.
Lessons from inlet relocation: examples from Southern Portugal
Abstract Inlet relocation is a coastal management tool that, when applied to a migrating inlet, involves the artificial opening of a new tidal inlet along the historic migration path of the inlet. The old inlet is then artificially closed, or it is left open and will eventually close if the new inlet captures the entire tidal prism. Two inlets were relocated in such a manner in Southern Portugal and then were the subject of a monitoring program that included the acquisition of quantitative (topo-bathymetric surveys) data. Data was acquired for 4 years after the relocation at one of the inlets (Ancao Inlet) and for 2 years at the other (Fuzeta Inlet). The data obtained from the monitoring program were analysed together with the wave climate and then compared with historical information on the natural inlets, in order to assess the degree of success of the relocation actions. One of the relocations studied, Ancao Inlet, was considered to be successful even though an initial unexpected behaviour produced some material damage to property. On the contrary, the relocation of Fuzeta Inlet did not have the expected results, and the new inlet was affected by the same problems as the old one. It was found that the most important factor for a relocation action to succeed is the correct choice of the opening location. A theoretical procedure to enhance the possibilities of relocation success is suggested. (1) Hydrodynamic studies are needed in order to determine if the present conditions are similar to the historical ones. (2) The position for the inlet opening is chosen according to the hydrodynamic conditions, but there are other factors to be taken into account, i.e., the historical migration paths and typical inlet width of the natural inlet; the hydrodynamics of the backbarrier; the morphology of the backbarrier and, for multi-inlet barrier island systems, the proximity to adjacent inlets. (3) Once the position is chosen, environmental impact studies should be made in order to assess the risk of the relocation for the ecosystems of the area. Only if the environmental impact studies are favourable should a relocation action be performed.