Na próxima sexta-feira (28 de maio de 2021) o prof. José Maria Landim Dominguez, coordenador do GT1.1 do inctAmbTropic (Deltas e erosão da linha de costa) proferirá uma palestra no webinário "2021 World River and Delta Systems - Source-to-Sink Webinar Series" organizado pelo professor Paul Liu, da Universidade Estadual da Carolina do Norte, Estado Unidos.
A palestra apresentará uma síntese dos principais resultados alcançados para o delta do São Francisco, no âmbito do inctAmbTropic.
A palestra poderá ser acompanhada no canal do YouTube: tinyurl.com/s2stalks , com inicio previsto para as 10:00hrs (horário de Brasília), dia 28/05/2021.
Um trabalho recentemente publicado na revista Marine Geology (IF: 3.04) pelo GT1.1 (Deltas e Erosão da Linha de Costa) intitulado "Effects of Holocene climate changes and anthropogenic river regulation in the development of a wave-dominated delta: The São Francisco River (eastern Brazil)" de autoria de José Maria Landim Dominguez e Junia Kacenelenbogen Guimarães, discute os efeitos das mudanças climáticas durante o Holoceno e da regulação antropogênica do rio São Francisco no desenvolvimento do seu delta e conclui que a construção do delta ocorreu em pulsos associados a períodos mais úmidos na bacia hidrográfica. O artigo também discute as causas da erosão severa que afeta a desembocadura fluvial nas última décadas.
Modelo evolutivo do delta do São Francisco, durante o Holoceno
Erosão da linha de costa durante o periodo 1960-2020 no delta do São Francisco ABSTRACT
The São Francisco River is the fourth longest river in South America and one of the most regulated. Severe coastalerosion has affected the delta shoreline since 1985, leading to the complete destruction of Cabeço village be- tween 1997 and 1999. In this study, we mapped and radiocarbon dated the beach ridge sets occurring on the delta plain and performed a detailed analysis of the delta shoreline changes since 1960. During the Holocene, the delta plain construction was punctuated and took place during episodes of higher river discharges coincident with Bond events 4, 2 and 1 and periods of higher precipitation in the river basin, as reconstructed by δ18O measurements in cave speleothems. The last major episode of delta construction apparently ended at approxi- mately 1.0 ka cal. BP. Since that time, riverine sediment input has been just sufficient to maintain the shoreline. A comparison of historical maps and aerial photographs showed that from 1853 to 1960, the shoreline at the river mouth remained in approximately the same position. A decrease in rainfall in combination with river regulation, particularly after 1985, triggered extensive erosion at the delta shoreline. This erosion was not caused by sediment retention behind the major dams but instead resulted from changes in the backwater/drawdown effects deriving from river regulation. Shoreline erosion mostly affected the river mouth. The mobilized sediments caused progradation of the downdrift shoreline. Updrift of the river mouth, the shoreline remained stable, as it had already reached an equilibrium orientation in which the net longshore transport was zero
O trabalho completo pode ser acessado em: https://doi.org/10.1016/j.margeo.2021.106456
Atualizado: Abr 27
Saiu publicado no periódico Ocean and Costal Management (IF=2.482) um novo trabalho no âmbito do inctAmbTropic Fase II intitulado "Evaluation of decadal shoreline changes along the Parnaíba Delta (NE Brazil) using satellite images and statistical methods" de autoria de Thiago Augusto Bezerra Ferreira , André Giskard Aquino da Silva, Yoe Alain Reyes Perez, Karl Stattegger e Helenice Vital, que investiga o comportamento da linha de costa do delta do Parnaíba no período 1984-2017. O trabalho concluiu que a redução na descarga fluvial do rio Parnaíba entre 1995-1999 e 2009-2012 foi a causa principal do recuo erosivo experimentado pelo delta.
Comportamento da linha de costa do delta do Parnaíba entre 1984-2017. Vermelho: erosão. Verde: progradação.
This study investigated changes of the shoreline position in the Parnaíba River Delta (PRD), which is in an underdeveloped and sparsely populated area. The general behavior of the shoreline between 1984 and 2017 was analyzed using 12 Landsat satellite images and the Digital Shoreline Analysis System (DSAS) software. DSAS applied statistical methods, such as Weighted Linear Regression (WLR) and End Point Rate (EPR), to define whether the shoreline was retreating or accreting. Data analysis revealed that, on a decadal time scale (33 years), 52% of the PRD shoreline retreated under erosional conditions, while 48% accreted. Accretion mainly occurred at the vicinities of the river mouth, especially eastward where the highest progradation rate was observed (maximum of 29 m/year). Shoreline retreat, up to 9 m/year, occurred predominantly in the western part of the PRD and away from the river mouth. However, changes of the general behavior of the shoreline (retreat/accretion) were observed at an inter- decadal time scale, which were positively related to variations in river discharge. Variations of river discharge are directly dependent on the rainfall amount along the drainage basin that, in this region, is controlled by climatic conditions such as El Niño and La Niña. Therefore, the reduced river discharge observed between 1995- 1999 and 2009–2012 (El Niño periods), was the major cause the triggered the observed coastal retreat (>6 m/ year) on PRD shoreline during these periods. Consequently, the variability of natural factors, such as river discharge and rainfall, are the main drivers of shoreline changes on PRD, since anthropogenic impacts have hitherto only marginal effects on the delta region and on the drainage basin of the Parnaíba river.
O trabalho completo pode ser acessado em: https://doi.org/10.1016/j.ocecoaman.2020.105513