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MORAIS, J. O. DE; DIAS, C. B.; PINHEIRO, L. DE S. Depuration capacity of the Timonha – Ubatuba estuarine system, in Ceará State, Brazil. Arquivos de Ciências do Mar, Fortaleza, v. 47, n. 1, p. 30-37, jul. 2014. The capacity of purification of the Timonha-Ubatuba estuarine system was evaluated through the application of semi-empirical numeric models. Those models were based on hydrological and morphological characteristics of the estuary basin, culminated with the estimative of the time of discharge for the system different points. This area is located on the semiarid coast of the Brazilian northeastern region, where the rivers are intermittent and they flow only during the rainy season. The monitoring was accomplished during 2004 during both rain and dry periods, in a complete spring tide. At the dry period, practically there was no fluvial discharge, which gives rise to the dilution processes to be just controlled by the oscillation of the tide (tidal prism). On the other hand, during the rainy period the fluvial speed and discharges were capable to renew the waters of the system. During this period, the water’s residence was only in the first day. In general the Timonha-Ubatuba estuarine system presented a good capacity of renewal of its waters. A capacidade de purificação do sistema estuarino Timonha-Ubatuba foi avaliada através da aplicação de modelos numéricos semi-empíricos e dados coletados em campo. Os modelos baseados em características hidrológicas e morfológicas deste estuario resultaram nas estimativas do tempo de descarga ao londo do canal estuarino. O sistema estuarino está localizado no litoral Semi-Árido do Nordeste brasileiro, onde os rios são intermitentes, com fluxo restrito ao período chuvoso. O monitoramento foi realizado em 2004, durante os períodos de chuva e estiagem em um ciclo completo de mare de sizígia. Durante o período de estiagem, praticamente não houve fluxo fluvial, ocasião em que os processos de diluição foram controlado pela oscilação da maré (prisma de maré). Por outro lado durante o período chuvoso as descargas fluviais foram capazes de renovar as águas do sistema com mais rapidez, com tempo de residência de apenas 1 dia. Em geral, o sistema estuarino Timonha-Ubatuba apresentou uma boa capacidade de renovação das suas águas.

This study analyses the space-time evolution along the Fortaleza coast over the past 31 years (1972-2003) with a special emphasis on the Mucuripe port area (Fortaleza, Ceará, Brazil) examining changes in the coastal dynamics produced by the building of the city’s port. The construction of the port’s jetty interrupted the natural feeding process of the beaches with sediment moving east to west. Sediment was blocked east of this structure leading to an erosion process to the west. This multi-temporal study is based on the analysis of aerial photographs and images from the Quickbird satellite. The objective is to determine the recent evolution of this coastline through calculation of the variation in retrograding and prograding areas. The variation of the city of Fortaleza's dunebeach interface shoreline, which concerns an extension of approximately 30 km of shoreline, revealed a prograding rate of 0.8284 km2 /31 years (1972/2003) and a retrograding rate of 0.0701 km2 /31 years (1972/2003). Analysis of images of Mansa Beach, located in the Mucuripe port basin, showed that in 1972 Mansa Beach had an area of 0.13843 km2, in 1998 it increased to 0.15307 km2 and in 2003 it reached 0.15455 km2. The analysis revealed that the changes in the shoreline are more subject to shoreline accretion. The analysed period shows a 92% a ccretion rate and an 8% erosion rate. The results contribute to the improved management of the Fortaleza coast.