Spatiotemporal Variability of Longshore Sediment Transport on the Brazilian Coast

Abstract The lack of planning and management regarding the transport of sediments along the coast can alter the existing equilibrium in coastal regions, causing or accelerating erosive processes and resulting in economic and environmental damage. Thus, it is important that the characteristics of the coastal drift be investigated, serving as source of information for future projects involving the coastal environment management. Within this context, the present work aims to identify the annual sediment transport averages along the Brazilian coast, the dominant direction of the coastal drift and its spatial variability. For this, a wind-generated wave modeling was considered, with 37 years of data (1979 to 2015), as well as four sediment transport formulations. For the spatiotemporal variability, the analysis of wavelets was applied, relating the effect of cycles of variability over the behavior of longshore sediment transport. The results showed that the largest annual volumes of sediment transport occurred in the northeastern Region of Brazil, reaching approximately 850000 m3/year-1. On the other hand, the smallest transport averages occurred in the southern region, in the state of Santa Catarina, reaching the value of 13497 m3/year-1. In the northeast region, annual and interannual cycles were more frequent and more energetic than in the southern Region, where short cycles presented similar importance to longer cycles, during 37 years of the study. However, in the overall context of the analysis, the long period cycles are more significant for longshore sediment transport, since this is a long term process. In this way, the present article contributes with information on longshore sediment transport, highlighting the annual means and the dominant drift, and deals with important questions about the influence of cycles of variability in the study region, emphasizing the importance of longer period events for the control of sedimentary transport in the Brazilian coast.