Sedimentation analysis of the maritime stretch after dredging activities for widening and deepening Santos’ Port Channel

Abstract

Occupying a prominent position in the world ranking for container handling, the Port of Santos stands out as one of the largest and busiest port complexes globally. It holds the title of the largest port in the Southern Hemisphere and ranks second in Latin America, second only to the Port of Colón in Panama. In 2010, the port started an expansion process in its navigation channel, reaching a minimum width of 220 m and an average design depth of 15 m, allowing safe passage of ships with drafts up to 13.50 m with an additional increase in this measure up to 1 m at high tide. The adjustments made to the sedimentary dynamics of the estuarine channel had a twofold impact: an increase in the amount of maintenance dredging required to keep the channel navigable, and morphological changes in the Ponta da Praia region. Thus, this study seeks to evaluate the management of maintenance dredging in Santos’ Porto by examining the alterations in sediment dynamics in a section on the Porto Channel. For that, we calculated the rate of sedimentation in the channel after its expansion to a depth of −15.0 m, considering the space and temporal variability of these rates. To determine the sediment contribution, we compared of seabed elevation data from consecutive campaigns performed between 2014 and 2019 in the maritime area of the Porto Channel, considering dredged volumes in the sedimentary balance analysis. In addition, we divided the Channel access into 11 control areas to assess sedimentation rates during non-dredging periods. Therefore, over long periods and considering the entire area, the average sedimentation rate was 4.2 × 10⁶ m³/year, with a standard deviation of 1.7 × 10⁶ m³/year. We noted in short periods between surveys with higher rates, up to 1.57 × 10⁶ m³/month, with no correlation to extreme storm events. In addition, we observed a greater sedimentation rate in the curve stretch (areas 5 to 9) than in other control areas. Here, SPA-hired dredges cannot maintain the required depth with this sedimentation rate. The port authority must provide alternative solutions as the access channel deepens. It must intensify the frequency of dredging in the critical sedimentation areas (to the curved stretch of the channel and the entrance to the estuary) to maintain the target depth. When sedimentation rates are high, the efficiency of dredging operations decreases, rendering navigation with loaded vessels unfeasible.