Coastal Hazards in Brazil

Sea Levels

The sea levels along the Brazilian coast is expected to continue to rise in the decades ahead. This is a major issue because many of their most important and largest cities are located near the coastline. Which mean that a good portion of Brazils citizens are vulnerability to sea level rise and the other effects of climate change, including the increased frequency and intensity of rainfall.

According to a report titled “Vulnerability and adaptation of Brazilian coastal cities to climate change impacts” published by the Brazilian Panel on Climate Change (PBMC) on June 5, 2017, "the global average sea level rose by 19 cm between 1901 and 2010, varying in the range of 17-21 cm." Between the years 1993 and 2010 the annual average level increased by over 3.2 mm. In São Paulo and Rio de Janeiro, average sea level has increased 1.8-4.2 mm since 1950. According to the same report, climate change and accelerating sea level has a major impact on the coastal areas in Brazil. 

Climate Change Worldwide

Scientific results indicate that sea levels worldwide have been rising at a rate of 0.14 inches (3.5 millimeters) per year since the early 1990s. This puts thousands of coastal cities, and even whole islands at risk of being claimed by the ocean. The image below is a prediction of what South America would look like if all the ice were to melt. If we continue adding carbon to the atmosphere, we will most likely be looking at an ice-free planet in the next 5,000 years, with an average temperature of around 80 degrees Fahrenheit rather then the current 58 degrees Fahrenheit.  

Coastal Erosion

The consequences of rising sea levels includes increased coastal erosion; increases in the frequency, intensity and magnitude of floods; the increased vulnerability of people and property; and decreased habitable space. Coastal erosion today is a serious problem because of the substantial property damage it causes, especially along the northeast coast of Brazil. A report in 2018 commissioned by Ministry of Environment estimated that 60% of Brazilian seasides is effected by erosion. The causes of coastal erosion in Brazil are due to human activity and low slopes that make it easy fro the shoreline to advance. The elevation of sea level does not appear to have the same impact along the Brazilian coast as in the Northern Hemisphere, to the extant that the Brazilian coast has been rising throughout the last 5,000 years.

Modifications in the past and present

The coastal population has been continuously growing since 1990. Although erosion is widely accepted along the beaches of Conceicao and Hermenegildo, the amount of erosion along the coast of the Rio Grande do Sul is still an issue. There have been several studies addressing coastal erosion in Rio Grande do Sul and recent DGPS monitoring indicates that about 80% of the Rio Grande do Sul shoreline is eroding.

Managing coastal erosion and the retreating of shorelines falls within the reach of coastal engineers. Many different approaches have been attempted. The traditional approach has been to construct coastal defense structures such as breakwaters, seawalls, and revetments. They often times end up destroyed and require a lot of maintenance. 

Copacabana Beach 1921 erosion 

In more recent years another approach, has been tried: artificial beach nourishment. This approach is not new, and has been tried on beach near Santa Barbara, California shortly after the end of World War I. Artificial beach rebuilding has even extended to beach creation. This specific solution has been attempted in Rio de Janeiro on the Copacabana Beach which has experienced erosion for some time. 

Copacabana beach during the nourishment carried out between 1970 and 1972.

They had decided on a mixed approach where they dumped sand offshore coastal defense and some was deposited on Copacabana Beach itself over a distance of 4.2 km. This ultimately allowed the beach to widen from its remaining 55m to about 140m. 

Copacabana beach before (left) and after (right) artificial nourishment.

Sources: 

https://www.tandfonline.com/doi/abs/10.1080/00206819709465300

https://journals.openedition.org/confins/18175

http://agencia.fapesp.br/sea-levels-along-the-brazilian-coast-are-expected-to-rise-in-coming-decades/25560/

https://strangesounds.org/2013/11/if-all-the-ice-melted-scary-maps-show-effects-of-rising-water-level-around-the-world.html

https://revistapesquisa.fapesp.br/en/2019/06/24/the-progressive-destruction-of-brazilian-beaches/

https://www.youtube.com/watch?v=TFYbPhuVgoQ#action=share