The Paraiba do Sul River delta, a South America east coast system, presents deposits recording complex sedimentary dynamics in the deltaic plain during the Little Ice Age (LIA). The use of optically stimulated luminescence (OSL) dating, sediment grain-size characterization, and morpho-chronological analysis showed that from ∼450 to 100years (LIA period), both in lower to upper deltaic plain, remodeling occurred in conjunction with the coastline regression. The freshwater and sediment influx increases due to the moisture enhancements during the LIA resulted in the intensification of the fluvial dynamic, channel downcutting on the marine terrace, and sedimentary environments remodeling. Further, the base-level changes occasioned by the coastline regression strengthen the geomorphological dynamics associated with the recent changes in the Paraiba do Sul delta. Currently, the coastal erosion problem found in the area seems to reflect the coupling between climate dynamic (rainfall rates decrease) and multiple-scale anthropic intervention. Results show a high sensitivity of humid tropical deltaic systems to short-time climate events, further contribute to broadening discussions on the complexity of this delta system’s morphosedimentary evolution during the Late Holocene.

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Dentro da perspectiva dos estudos da dinâmica costeira, este trabalho visa contribuir para o conhecimento relacionado aos impactos oriundos da construção do Porto do Açu, localizado em São João da Barra/RJ. O objetivo é identificar e quantificar as alterações ocorridas na linha de costa do litoral que abrange a área de influência indireta do Porto, com ênfase na área de influência dos ambientes marinhos. A justificativa para a realização deste trabalho são as crescentes intervenções que vêm sendo feitas na área de estudo. A metodologia para alcançar os resultados foi análise de imagens de satélite, vetorização e a sobreposição da linha de costa para identificar alteração, além de calcular a área alterada com suporte de SIG. Dados de batimetria da plataforma continental interna adjacente à área de estudo foram extraídos através das cartas náuticas, a fim de realizar as simulações do comportamento das ondas para a área de estudo para dois cenários: sem e com as estruturas do Porto. Os resultados puderam revelar que na porção ao sul do empreendimento, ao longo de 7,5 km, houve uma progradação média da linha de costa de 14,13 metros entre os anos de 2010 e 2016, enquanto no intervalo de 2003 a 2010 a média de progradação foi de 33,21 metros. Já as simulações de ondas permitiram concluir que elas chegam à costa da localidade do Porto do Açu com características distintas quando comparadas com e sem as estruturas, características estas que se mantêm fora do desvio padrão quando comparadas ao comportamento das ondas em outros pontos de monitoramento analisados.

Coastal erosion affects several beaches worldwide in association with natural and human pressures. In recent decades, the coastland located on the Paraíba do Sul River mouth has been recognized as one of the main areas that suffer from this geomorphological dynamic. Furthermore, the scientific literature, even if scarce, has pointed out that these dynamics are causing negative socio-environmental responses and making the area less resilient. In the last few decades, hundreds of homes and other urban structures have become debris due to erosion caused by sea ingression, triggered by the coupling of environmental processes and dynamics occurring at different spatial and temporal scales. Thus, the present research aimed to analyze how the anthropic changes carried out in the Paraíba do Sul hydrographic basin are related to the intense coastal erosion at the mouth. Variations in fluvial–marine hydrosedimentary dynamics triggered this due to the construction of dams to supply large cities and for agricultural purposes. Water and sediment samples were collected and analyzed in different sectors of the main channel and on the adjacent coast, mapping land use in the basin area and surveying socioeconomic data. The results suggest that human pressures on the hydrographic basin during the last century are directly associated with the imbalance of the environmental system and, consequently, the progression of coastal erosion on the Paraíba do Sul delta shoreline.