Anthropogenic Pressure on Hydrographic Basin and Coastal Erosion in the Delta of Paraíba do Sul River, Southeast Brazil

Abstract

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.

Reply to the comments on Souza et al. (2022) “Recent geomorphological changes in the Paraiba do Sul delta, South America East Coast”

“…Main littoral drift along the Paraíba do Sul River Delta due to longshore currents from S to N (red open arrow), according to Cassar and Neves (1993), Bastos and Silva (2000), Lämmle and Bulhões (2019), Lämmle et al (2022a), and literature therein. This triggered the erosion of Atafona sandy beach to the south and developed the S-N-oriented sandy littoral spits (red open circles) and the barrier island of Gargaú Lagoon to the north due to sand drift and deposition (from Google Earth Pro mod.…”

“…This also explains the shoreline progradation or stability of Gargaú beach to the north of PSRD and partially the NE-orientation and angle of the river mouth related to load, the difference in waters salinity, change of wind direction and intensity, decrease in calm winds, tides, and sea-wave climate (jet effect sensu Masselink and Hughes, 2003; Donadio et al, 2018). The divergent and local sediment transport from the mouth is likely due to reduced river sediment supply and clockwise and counterclockwise secondary circulation cells.

Figure 1.Main littoral drift along the Paraíba do Sul River Delta due to longshore currents from S to N (red open arrow), according to Cassar and Neves (1993), Bastos and Silva (2000), Lämmle and Bulhões (2019), Lämmle et al (2022a), and literature therein. This triggered the erosion of Atafona sandy beach to the south and developed the S-N-oriented sandy littoral spits (red open circles) and the barrier island of Gargaú Lagoon to the north due to sand drift and deposition (from Google Earth Pro mod.

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“…The original article "Recent geomorphological changes in the Paraiba do Sul delta, South America East Coast" (Souza et al, 2022) refers to investigations that have been conducted since 2016. To this, two other works (Lämmle et al, 2022a(Lämmle et al, , 2022b are part of efforts to understand how short-term climate and environmental events in the Holocene change the Paraíba do Sul River delta (PSRD). Consequently, data have not been published only in Portuguese for the Brazilian scientific community, but in English for the international ones reached through articles in journals with reliable and high-impact double-blind peer-review processes such as the PPG.…”

“…Considering the recent shoreline evolution, this is not the specific topic of our article. Our consideration about the concauses of littoral retreat to the south and progradation to the north of the PSRD, also related to river damming through four barrages gradually operating since the 60s and consequent sediment load reduction with a deficit in coastal balance, is shown in a successive article we suggest to read: Lämmle et al (2022a). For the first time, this article relates the variation in hydrological data of the fluvial discharge in the 1950–2020 period with erosion processes registered especially between 1985 and 2022 along the beach to the south of PSRD considering the main littoral drift from south to north due to longshore currents, in accordance with Cassar and Neves (1993) and Bastos and Silva (2000).…”

Análise Das Mudanças Da Linha De Preamar Máxima Em Um Trecho Da Praia Do Cumbuco (Caucaia-Ce) Com Aplicação Da Ferramenta Digital Shoreline Analysis System (Dsas)

“…A zona costeira abriga 53% da população mundial (Barragan; De Andrés, 2015; Toure et al, 2019;Dewi;Bijker, 2020) e 15 das 20 megacidades (>10 milhões da população) do mundo estão situadas neste ambiente (Luijendijk et al, 2018). Portanto, estressores humanos têm causado impactos negativos nos ambientes costeiros e fluviais, provocando um desequilíbrio no abastecimento sedimentar das praias, com consequente efeito sobre as mudanças no posicionamento da linha de costa (De Andrés et al, 2018;Martinez et al, 2019;Awad, 2021;Lämmle et al, 2022).…”