Estimativa da taxa de assoreamento baseada em perfis transversais em um sistema estuarino lagunar Mundaú: Integração Ecobatímetro e RTK

Abstract

It is of great relevance to understand how the contribution of the complex sedimentary dynamics in coastal regions in the periods of great pressures for the (modal) waterway transport expansions in Brazil. It is estimated that more than 80% of international trade is transported by waterways and in Brazil it is no different. Despite the rare approach, knowledge about submerged relief, sedimentation rate in estuarine systems, observational field or the validation of empirical methods by theoretical methods that can provide a good diagnosis. This study is based on field activities in a Lagunar Estuarine System in northeastern Brazil. The production of sediments from the drainage areas of the mundaú river basin were evaluated using empirical techniques and compared to the quantifications using topobatimetric surveys (SONAR), showing a production of 1287 - 1461 kilos per year and a deposition layer of 9, 7 cm (2012) and 14 cm (2018). The ratio between topobymetric transects measured in 2012 and 2018 resulted in a sediment yield of 1821 kg per year and a deposition layer of 8 cm. The morphology of the coastal region of the bed and surrounding area of the estuarine system is constantly being altered, mainly in the left margin by the advance of the degradation that comes from the sedimentary contribution, interaction between the hydrodynamic forcing variations, as well as the possibility of associated geological processes with land movements in the districts of the city of Maceió, may be correlated with recent changes in bathymetry in the Mundaú lagoon. Despite the safety that cartography brings to navigation, developing hydrographic surveys (LH) has always been a challenge, due to the very specialized type of workforce, consequently, due to the difficulty in performing the service, the high cost of execution, and constant changes in the sedimentary dynamics and the climatic conditions that could interfere in this execution. With the advancement of science and technology, new equipment and methods have been developed, making it possible to improve the accuracy of these positions. The present work shows the use of GPS, its connection with the ecobatimetric or sonar system and the care to be taken. In this work, the methodology adopted covers all the steps for the realization of a topobatimétrico survey with scanning sonar, totally automated: data collection, applying the technique RTK (Real Time Kinematic), processing, analysis and generation of data of the Model (MDP) of the estuary bed. As main results, progressive morphological changes were observed along the canal, in the years of 2012 and 2018.