Shoreline changes in northeast Brazilian delta’s
Deltas; Coastal Dynamics; São Francisco Delta Parnaíba Delta; Coastal erosion
Deltas are transitional environments between the continent and the ocean, being extremely important to humanity due to the range of natural resources used in the energy, food, industrial and transport industries. However, due to a greater demand for these resources, both in the coastal zone and in its drainage basin, the main deltas in the world are subject to processes of coastal erosion and subsidence. In this sense, monitoring this environment, through new technologies, is essential for determining erosional hotspots, thus facilitating decision-making and mitigating and adapting measures. The main objective of this thesis is the study of coastal dynamics in Brazilian deltas. Multispectral images, in different temporal scales (intermediate and short), associated with hydroclimatic data (flow of the main river courses and rainfall) were used to quantify the variation of the coastline of the Parnaíba, São Francisco and Jequitinhonha deltas, determining the most areas criticisms of erosion and its correlation both with human activities, in the coastal zone and in the drainage basin, and through natural processes (waves, currents, geology in the drainage basin). The results obtained for the São Francisco Delta indicate that on an intermediate time scale (between 1984 and 2019), 66% of the coastline eroded, while 34% prograded. The highest erosive and progradational rates occurred southwest of the mouth, with rates above 12 m/year and 8/year, respectively. In the shorter analyzes (decades), the highest erosive rates occurred between 1984 and 1991, the period in which the Xingó dam began, the dam closest to the coastal zone. In turn, these analyzes also indicate that erosion, at the mouth of the São Francisco delta, has been slowly decreasing over the decades, even with the constant decrease in the river's flow.