Sedimentation processes in the navigation channel of Patos Lagoon Estuary, southern Brazil

Abstract

The morphology of estuarine navigation channels varies in time and space. Siltation occurs in areas where flow conditions enable sediment trapping and it limits navigability in most cases, requiring periodic dredging. Identifying sedimentation patterns is fundamental to designing ports to reduce siltation. The Port of Rio Grande, located in the Patos Lagoon estuary, holds strategic significance and it is a key example for understanding the evolution of large estuarine access channels. We used 19 bathymetric surveys from April 2001 to February 2018 to generate Digital Elevation Models and evaluate the evolution in time of bed morphology in the Porto Novo basin and its access channel (located in Port of Rio Grande). Also, we considered hydrological data available from September 2005 to December 2011. Major siltation rates were observed in the northwestern portion of the basin and the convex margin of the access channel, whereas other locations exhibited stable conditions. Channel configuration and position were determinants to define spatial variations of sedimentation processes. Hydrological conditions, mainly when discharge exceeds 4,000 m3/s over long periods, strongly controlled siltation magnitude in the Porto Novo basin and its access channel.