The Amazon River is the second longest river in the world and one of the most important waterways on the planet. It contains more freshwater by volume than any other river, is home to the largest species of river dolphin in the world, and is home to 100 species of electric fish and up to 60 species of piranha.
Yet despite its many and varied qualities, there is something not found on the the amazon river: bridges.
Since the Amazon crosses three countries (Peru, Colombia and Brazil) and more than 30 million people live in the river basin, according to the World Wide Fund for Nature (opens in a new tab), it seems somewhat unlikely that no bridge spans the river. So why is this the case? Are there any fundamental difficulties in building such structures in a rainforest containing barters, vast wetlands, and thick, deep undergrowth? Are there financial barriers? Or is it just not worth it?
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The Amazon Anomaly
Compared to some of the world’s other most recognizable rivers, the Amazon’s lack of bridges is an oddity. There are around nine bridges spanning the Nile in Cairo alone; over 100 (opens in a new tab) bridges have been completed over the past 30 years over the Yangtze, Asia’s first river; while the European Danube, which is only one-third the length of the Amazon, has 133 bridge crossings (opens in a new tab).
So what’s wrong with Amazon?
“There is not a pressing enough need for a bridge over the Amazon,” said Walter Kaufmann, president of Structural Engineering (Concrete Structures and Bridge Design) at the Swiss Federal Institute of Technology (ETH) in Zurich, Live Science said in an email.
The Amazon, for much of its 4,300 mile (6,920 kilometer) length, meanders through sparsely populated areas, meaning there are very few major roads that a bridge can connect to. And in the towns and villages that line the river, boats and ferries are an established way of moving goods and people from one bank to the other, meaning there’s not really a need for build bridges, if not to make trips a little faster.
“Of course, there are also technical and logistical difficulties,” Kaufmann noted.
According to Kaufmann, the Amazon is far from an ideal location for bridge builders, as it has an array of natural stumbling blocks that should 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 that would require a significant financial investment, Kaufmann said. In addition, the changing positions of the course of the river through the seasons, with “pronounced differences” in water depth, would make construction “extremely demanding”. This is due, in part, to the water level of the river which rises and falls throughout the year and to the soft sediments of the banks which erode and move seasonally, depending on the Amazon Waters Initiative (opens in a new tab).
Kaufmann noted that while these particular problems are not unique to the Amazon, “they are particularly severe there.”
“The environment of the Amazon is certainly among the most difficult [in the world]”, said Kaufmann. “Bridges across straits are also difficult if the water depth is deep, but at least you know that construction is possible using pontoons, for example.
Pontoons, or floating structures, aren’t a solution that would work in most parts of the Amazon, Kaufmann said, because the river is heavily affected by seasonal variations, which adds an extra layer of complexity. For example, during 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 during the rainy season – from December to April – the river can be as wide as 30 miles (48 km), and the water level can be 50 feet (15 meters) higher than it is during the dry season, according to Britannica (opens in a new tab).
“This challenge would be unique,” Kaufmann said.
So, in addition to the lack of immediate need for a bridge over the Amazon, the processes involved in building a bridge would be considerable.
Related: What is the largest freshwater fish in the world?
A bridge too far?
It should be noted that, although no bridge crosses the Amazon, there is one that crosses the Negro River, its main tributary. Called the Ponte Rio Negro, the bridge, completed in 2011, connects Manaus and Iranduba, and is to date the only major bridge that crosses a tributary of the Amazon.
But, while there are no concrete plans in place for a bridge across the Amazon, “that doesn’t mean it won’t happen,” Philip Fearnside, biologist, scientist and conservationist American who has spent much of his career in Brazil, says Live Science.
In 2019, Jair Bolsonaro, President of Brazil, said he wanted a bridge (opens in a new tab) across the Amazon to be built as part of its “Rio Branco Project”, but there has been no progress yet. “It would be very costly compared to the economic benefits it would bring,” Fearnside noted.
Upon completion of the Ponte Rio Negro, tentative plans were drawn up for a bridge over the Upper Amazon – known as the Solimões River – in the municipality of Manacapuru, which would connect the BR-319 highway to Manaus and remove the need a ferry. crossing.
“The BR-319 is a high political priority, but it has no economic justification,” Fearnside said. “It is cheaper to transport products from factories in the free zone of Manaus to São Paulo by water.”
Additionally, as noted in a 2020 comment, Fearnside wrote for the environmental news site mongabay (opens in a new tab) regarding the proposed development of the BR-319, the creation of such a bridge “would give deforesters access to about half of what’s left of the country’s Amazon rainforest, and so that’s perhaps the most important conservation issue for Brazil today,” Fearnside said.
So, is there any chance that a bridge could be built over the Amazon in the near future?
“I think a bridge would only be built if the need outweighed the difficulty and the cost,” Kaufmann said. “Personally, I doubt that will happen soon unless there are unforeseen economic developments in the region.”
Originally posted on Live Science.