The Amazon River is the second longest river in the world and one of the most important waterways on the planet. It contains more fresh water by volume than any other river, is home to the largest species of river dolphins in the world and hosts 100 species of electric fish and up to 60 species of piranhas.
And yet, despite its many and varied qualities, there is something that cannot be found on the Amazon River: bridges.
Given that the Amazon flows through three countries (Peru, Colombia and Brazil) and more than 30 million people live in the river basin, according to the World Wildlife Fund (opens in a new section), it seems unlikely that there will be no bridges across the river. Why is that? Are there fundamental difficulties in building such structures in tropical forests containing swaps, extensive wetlands, and deep, dense undergrowth? Are there any financial barriers? Or is it just not worth the effort?
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The Amazon Anomaly
Compared to some of the other most recognizable rivers in the world, the lack of bridges in the Amazon is strange. In Cairo alone there are about nine bridges spanning the Nile; more than 100 (opens in a new section) bridges have been completed over the past 30 years across the Yangtze, Asia’s leading river; while the European Danube, which is only a third of the length of the Amazon, has 133 bridge crossings (opens in a new section).
So what’s the deal with Amazon?
“There is no urgent need for a bridge across the Amazon,” said Walter Kaufmann, chairman of Structural. Engineering (Concrete structures and bridge design) at the Swiss Federal Institute of Technology (ETH) Zurich, Live Science reported in an email.
The Amazon, for much of its 4,300 miles (6,920 kilometers), meanders through sparsely populated areas, meaning there are very few major roads to connect to each bridge. And in cities bordering the river, boats and ferries are a well-established means of moving goods and people from coast to coast, which means there is no real need to build bridges except to make travel a little faster.
“Of course, there are technical and logistical difficulties,” Kaufman said.
According to Kaufman, the Amazon is far from the ideal place for bridge builders, as there are many natural stumbling blocks that need to be conquered by engineers and construction workers.
For example, its vast swamps and soft soils would require “very long access viaducts [a multi-span bridge crossing extended lower areas] and very deep foundations “, and this will require serious financial investments, said Kaufman. In addition, the changing positions of the river in seasons, with “pronounced differences” in water depth, would make construction “extremely demanding”. This is partly due to the rising and falling water levels in the river throughout the year and the erosion and seasonal displacement of soft sediments along river banks, according to Amazon Waters initiative (opens in a new section).
Kaufman noted that while these specific problems are not unique to Amazon, “they are particularly severe” there.
“The environment in the Amazon is certainly one of the most difficult [in the world]”Kaufman said.” Strait bridges are also a challenge if the water depth is deep, but at least you know it’s possible to build with pontoons, for example. “
Pontoons or floating structures are not a solution that would work in most parts of the Amazon, Kaufman said, as the river is heavily affected by seasonal fluctuations, which adds an extra layer of complexity. For example, in the dry season – between June and November – the Amazon has an average width of between 2 and 6 miles (3.2 and 9.7 km), while in the wet season – December to April – the river can be up to 30 miles wide (48 km) and the water level may be 50 feet (15 meters) higher than during the dry season, according to Britannica (opens in a new section).
“This challenge would be unique,” Kaufman said.
So, apart from the immediate need for a bridge across the Amazon, the processes involved in building one would be significant.
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Bridge too far?
It is worth noting that although there are no bridges crossing the Amazon, there is one that crosses the Negro River, its main tributary. Named the Ponte Rio Negro, the bridge, completed in 2011, connects Manaus and Iranduba and is to date the only major bridge to cross the tributary of the Amazon.
But while there are no specific plans for a bridge over the Amazon, “that doesn’t mean it won’t happen,” said Philip Furnside, an American biologist, scientist and conservationist who has spent much of his career in Brazil.
In 2019, Jair Bolsonaro, President of Brazil, said he wanted a bridge (opens in a new section) through the Amazon to be built as part of his Rio Branco Project, but no progress has been made yet. “That would be very costly compared to the economic benefits it will bring,” Fernside said.
Following the completion of the Ponte Rio Negro, temporary plans have been drawn up for a bridge over the upper Amazon – known as the Solimões River – in the municipality of Manakapuru, which will connect BR-319 with Manaus and eliminate the need for ferry crossings.
“BR-319 is a high political priority, but there is no economic justification,” Fernside said. “It is cheaper to transport products from factories in the Manaus free trade area to Sao Paulo by water.”
In addition, as stated in a commentary from 2020, wrote Furnside for the site for environmental news mongabay (opens in a new section) with regard to the proposed development of BR-319, the creation of such a bridge would “give deforestation access to about half of what’s left of the Amazon forest in the country, and that’s perhaps the most important issue for Brazil’s conservation today, “Fernside said.
So, is there a chance that a bridge across the Amazon will be built in the near future?
“I think a bridge will only be built if need outweighs difficulties and costs,” Kaufman said. “Personally, I doubt that this will happen soon, unless there are unforeseen economic developments in the region.”
Originally published in Live Science.