RESUMOO Mar de Ararapira é um estuário separado do mar por um estreito esporão, denominado Restinga do Ararapira, e possui uma barra que migra para sudoeste. Em trabalhos anteriores foi sugerido que o processo de migração pode mudar subitamente com a abertura de uma nova barra. O objetivo deste trabalho é caracterizar a evolução do esporão, estimar as taxas de migração da Barra do Ararapira e a data de abertura da nova barra, prever as mudanças morfológicas no estuário e nas costas próximas à barra decorrentes desse evento, e avaliar as consequências sociais e políticas dessas mudanças. Para atingir tais objetivos foram interpretadas fotografias aéreas de diversas datas e levantados perfis topográficos na parte mais estreita do esporão. Concluiu-se que uma nova barra deverá se formar a aproximadamente 6 km a noroeste da atual, entre 2012 e 2016. Esse evento causará o assoreamento da barra atual, forte erosão na costa oceânica próxima à mesma e progradação equivalente à erosão nas costas oceânicas próximas à nova barra. Essas mudanças deverão afetar as vilas próximas da Barra do Ararapira, Pontal do Leste e Enseada da Baleia, os parques Nacional do Superagui e Estadual da Ilha do Cardoso e os estados do Paraná e São Paulo. A previsão dos prováveis efeitos das mudanças decorrentes da abertura da nova barra sobre as comunidades locais e os limites dos estados e das unidades de conservação possibilita tomar decisões e executar medidas preventivas para minimizar ou evitar os efeitos adversos dessas mudanças. O acompanhamento das mudanças após a abertura possibilitará verificar a pertinência das previsões e auxiliará na compreensão de eventos futuros. Palavras-chave:Mudanças costeiras; Impactos ambientais; Evolução de esporão; Erosão costeira; Problemas de limites. ABSTRACTMar do Ararapira is an estuary isolated from the sea by a narrow spit and with an inlet that migrate to the Southwest. There are previsions that the migration could change suddenly by a new inlet opening. This work aims to determine the spit morphological evolution, estimate the inlet migration rate and the new inlet opening date, anticipate the morphological estuarine and coastal changes after the new inlet opening and evaluate the social and political implications of those changes. To achieve these objectives different data aerial photographs were interpreted and topographic profiles at the narrower spit place were performed. One can conclude that a new inlet located 6 km farther northeast will open at 2012 to 2016. The opening will cause the present inlet silting, strong erosion at the coasts near to the present inlet and strong accretion at the coast near to the new one. These changes will affect the three villages around, environmental protected areas administration and states government. The anticipation of the new inlet opening consequences on the local communities and state and environmental protected areas borders will provide preventive actions to minimize the adverse effects of the coastal changes. Monitoring the coastal changes after the...

Mar do Ararapira is an unusual estuary located at the border of Paraná and São Paulo states, in a relevant area of ecological interest and where an opening of a new inlet occurred in August 2018. Differing from classical estuarine models Mar do Ararapira has three inlets, one with open sea and two with the estuarine systems of Baía de Trapandé and Baía dos Pinheiros, the latter through an artificial channel named Canal do Varadouro. Mar do Ararapira also has multiple riverine inputs and the estuary head is not well defined. This paper presents: (a) Mar do Ararapira watershed characteristics, (b) an update of coastline shift close to the inlet and (c) a characterization of the estuarine bathymetry, bottom sediments and bedforms in 2009 and 2011. Comparison of parameters before and after an opening of a new inlet will help both the management of the estuary`s natural resources and the lives of the people inhabiting the surroundings. It is concluded that Mar do Ararapira corresponds to the lower part of an estuary. Its watershed extends 221.6 km 2 and is composed by three different morphologic sectors, which drains mountains and coastal plains. It presents a significant fresh-water input, estimated to range from 6.6 to 9.1 m 3 /s, and weak connectivity with its neighbor estuarine complexes. It is a shallow water body, with a mean depth of 4 m, where a deep main channel suggests intense bottom erosion by tidal currents. The ocean inlet migrates southwestward, mainly under the influence of high energy events. Prevailing bottom sediments are sand and muddysand. Subaqueous-sand-dunes and plane-beds are the most common bedforms at Mar do Ararapira. Three estuarine dynamically different sectors were recognized: (a) an inner sector with low tidal-current velocities and finer sediments; (b) a middle sector similar to a fluvial meander in dynamics, with higher tidal-current velocities and sandy sediments, where concave coasts are continuously eroded and convex coasts are silted; and (c) an outer sector, in which tidal-currents are segregated.