Why The Amazon River Has No Bridges

Let's find out the fascinating reason the Amazon river has no bridges!

July 4, 2023・

19 min read

Arguably the most famous waterway on the planet, the Amazon River is over 4,000 miles long and spans over 6 countries. This watery wonder is believed by many to be the longest river in the world, closely followed by the Nile. Although these two rivers may share a similar size, there’s one thing that they don’t have in common: bridges.

In total, the Nile has 9 crossings over Cairo alone, while shorter rivers like the Yangtze and Danube both have over 100. Meanwhile, Amazon has zero bridges. So, what’s the reason behind this? Tsunami-like waves? Or maybe even a super-sized serpent lurking in its dark depths? Let's uncover the mystery of why the Amazon River has no bridges whatsoever.

Amazon River Length And Width

The first thing you’ll notice about the Amazon River is its sheer size. Stretching some 4,345 miles long, it’s fair to say that this river is lengthy. Being such a big river, it’s unsurprising that the Amazon releases a lot of water into the Atlantic.

The river distributes around 44,000 gallons of freshwater into the ocean every second. That means that in 24 hours, the Amazon spills some 3.8 billion gallons of freshwater into the Atlantic. Together, this freshwater flow accounts for nearly 20% of all river water that enters the sea!

So the Amazon River may be long and chock full of water, but that doesn’t mean you can’t build a bridge across it, especially if it’s narrow. And, during the dry season, the river isn’t impossibly wide, averaging a width of 2 to 6 miles. That might sound huge, but considering that the Golden Gate Bridge in San Francisco is 1.7 miles long, building a crossing over the Amazon River seems feasible at least.

That’s until the wet season hits. From mid-December to mid-May, the heavens open over the Amazon. So much so that the water levels can rise to almost 50 feet, the same height as a 5-story building! During these months, the width of the river not only deepens, but it also swells.

In some parts, it can reach between 24 and 30 miles wide! That means, during the wet season, if you built a bridge over the Amazon River at its widest point, it would need to be a colossal 17 times longer than the Golden Gate Bridge!

Amazonian Floating Islands: Matupás

But the effects of the wet season don’t stop at wider rivers! Aquatic grasses, known as matupás, can cluster together on the river’s surface. When the flood season hits, these floating blocks of vegetation become filled with water, before sinking to the riverbed and dying. But, during the dry season, the flora formations rise again, literally!

Floating on the water’s surface, the vegetation patch provides a substrate of partially decomposed organic matter, on which plant species can start growing. The cycle of submerging and floating the grass blocks repeats itself over the course of successive wet and dry seasons.

Over time, matupás can reach up to around 40 feet tall and grow as large as 10 acres! To put that into context, the size of your average American football field is just over 1 acre. While that may provide a welcome resting place for some Amazon wildlife, it’s far from ideal to have a floating island bobbing along the river if you’re trying to construct a bridge!

Pororoca Tidal Bore

And yet, it’s not just the wet season that can be blamed for the Amazon River infiltrating engineer’s nightmares. Twice a year, during the biennial equinox, the Sun and Moon exert a stronger pull on the Earth than the rest of the year. And it’s this pull that brings the tides to their highest peaks.

In the case of the Amazon, these huge waves, come crashing in from the Atlantic Ocean, where they overpower the current at the mouth of the river, reversing its flow in the process. This phenomenon, known as a tidal bore or a Pororoca, wreaks havoc upon the Amazon.

These weighty waves can advance as far as 500 miles upstream, clocking soaring speeds of 15 miles per hour. That coupled with 13 feet high waves makes for a devastating mix. This mega-wave will swallow pretty much anything in its wake.

That’s not even to mention the horrors that these waves can bring with them. Whether it’s uprooted trees, massive matupás, or even predators, like piranhas and caimans, let’s just say you wouldn’t want to get in the way of a pororoca. Obviously, this river’s insane width, floating matupás, and tidal bores make it incredibly tricky to bridge over.

Tricky, but technically not impossible. After all, you could build a bridge far enough upstream to prevent tidal bores from splitting the crossing in two. Matupás, annoying as they may be, aren’t prominent throughout the river’s course. And regarding the width, why not just choose one of the narrower sections of the Amazon?

Amazon Infrastructure

There’s another factor that really ramps up the difficulty of bridge-building over this watercourse. Thanks to its dense rainforest, the Amazon has very few roads dissecting through it. And without roads, which are needed to transport essential construction materials, you can’t have bridges!

Take Macapá, on the northern shore of the Amazon delta, for example. It’s a city of more than half a million people. And yet, there’s not a single road connecting it to the rest of Brazil! The only way to reach Santarem, the next big city to the west of Macapá, is via plane or ferry.

For much of its 4,345-mile length, the Amazon River meanders through many areas that are sparsely populated, meaning that very few major roads are needed. And, even when roads are built there, it doesn’t always go to plan.

In 1973, the BR-319 was opened. This mega-road runs 540 miles long, from Porto Velho to Manaus, a city located right in the heart of the Amazon. But, as you know, nothing in this place comes easily.

Thanks to that trusty wet season, which regularly dumps more than 8 inches of rain per month from December to May across the region, a 250-mile ‘Middle Stretch’ has since been transformed into a muddy swampland. Don’t matter how big your 4x4 is, there’s no way you’re making it down 250 miles of this!

However, since 2015, a maintenance program has made it marginally passable during the dry season. And in July 2022, former Brazilian President, Jair Bolsonaro went a step further, vowing his support for the complete re-construction of an unpaved ‘Middle Stretch’ of BR-319. Sounds promising, but then there’s the delicate subject of the bill.

Estimated costs total a dizzying $265 million. But with most construction projects, it’s far more likely that the end result will far exceed this fat figure. While that may seem expensive, we’re only getting started! Remember, that’s the cost of the road alone, we’ve not even got to the main course yet, the bridge!

Back in 2010, Brazil built a bridge over the Rio Negro, the Amazon’s largest tributary. This 2.2-mile chunk of engineering excellence connects the cities of Manaus and Iranduba, limiting the busy ferry traffic across the tributary in the process.

Impressive as it sounds, the Rio Negro Bridge still cost an eye-watering $570 million to build. Presuming that an Amazonian bridge would cost a similar amount, the total damage for repairing the BR-319 and bridging over the Amazon is likely to set Brazil back over $835 million!

With such a perilous price tag, there needs to be high demand to justify building such a bridge. And, as the Amazon tends to meander through sparsely populated areas, there just isn’t enough of a reason to splash out on a near-billion-dollar bridge! Instead, most people have become accustomed to crossing the river by boat or ferry.

Meeting Of Waters

But Rio Negro, isn’t just known for having a fancy bridge. The Encontro das Aguas, otherwise known as the ‘Meeting of Waters’ is the place where the Rio Negro and the Amazon River meet. But the rivers don’t technically meet. Instead, there’s a clear divide between the color of the two waters that’s so distinct, it can even be seen from space!

While that looks like the work of some wicked demon, lurking deep within the Amazon River, the ‘Meeting of Waters’ is simply down to the difference in temperature, speed, and murkiness between the two bodies of water.

So the ‘Meetings of the Waters’ may not pose any threat to someone crossing this river, but there are a few darker, more disturbing theories, as to why no single bridge crosses the Amazon. To explain, let’s turn the clocks back 60 million years.

Titanoboa

During the Paleocene epoch, a deadly creature lurked in the swamps of Colombia, a country that the Amazon River passes through. Anyone with a fear of snakes, brace yourselves for this. This prehistoric predator, known as the Titanoboa, stretched out to around 50 feet long and weighed in at a stocky 2,500 pounds.

For some perspective, green anacondas take the prize for the chunkiest snake today, but at their biggest, they’re only around 1/5th of the weight of the terrifying Titanoboa. Before you freak out, you’ll be glad to know that the Titanoboa is extinct and has been for nearly 58 million years. So, you might not need to worry about any super-sized snakes slithering through the waters of the Amazon.

Colonel Percy Fawcett

However, despite their supposed extinction, there have been multiple sightings of giant snakes swimming in the murky Amazonian waters! The first widely known account of an apparent Titanoboa sighting was by Percy Fawcett, a British geographer, and explorer of South America in the early 20th century, who wrote about the experience in his diary:

“We stepped ashore and approached the reptile with caution… As far as it was possible to measure, a length of 45 feet lay out of the water, and 17 feet in it, making a total length of 62 feet.”

But Fawcett’s claim wasn’t taken for anything more than a good story. It wasn’t helped by the explorer claiming to have seen a dog with two noses, as well as a giant spider the size of a dinner plate, that left its victims blackened from its poison. Sounds like Fawcett may have licked one too many Amazonian toads.

It turns out that the spider the explorer was describing may have been the Goliath birdeater! It’s the world’s largest spider, capable of growing to around the size of a puppy, just not quite as cute.

And as for the creepy canine, no other mention of this unusual double-nosed dog occurred, that was until fellow explorer, John Blashford-Snell encountered a pupper with a double-barrel snoot! Turns out that a rare breed of dog, known as the double-nosed Andean tiger hound, inhabits the shadowy depths of Bolivia, another region that the Amazon spreads through.

So, if the double-nosed dog and giant spider turned out to be sightings based on animals that actually exist, perhaps Fawcett’s sighting of the Titanoboa was real after all? It may sound crazy, but Fawcett isn’t the only one to have spotted a scarily sized serpent in the Amazon.

Yacumama Snake Legend

Yacumama, meaning ‘mother of water’, is the name given to a 200-foot-long serpent, believed to dwell in the Amazon River. According to a legend from indigenous Amazonian tribes, this beast would suck up any living thing that passed within 100 steps of it.

Getting vacuumed up by a bus-sized snake would be reason enough for me to never even think about crossing a bridge over the Amazon! But, Yacumama’s reign of terror doesn’t stop at hoovering up humans.

The Shanay-Timpishka is a tributary of the Amazon River, found in Peru. Although it may look idyllic, this stretch of water is straight from the pits of hell; at least it feels like it. Shanay-Timpishka is known for its boiling water, ranging from 113 to 212°F. And local shamans believe that the steamy stream was birthed by Yacumama.

Hardcore as that sounds, the more likely explanation is that the tributary is located above deep-rooted faults, allowing the water to travel deep down into the Earth’s crust. Here, it gets heated up by rocks in close proximity to the superhot Mantle. The fiery water is then fed back to the Earth’s surface through hot springs that heat up the spicy river.

Regardless of how Shanay-Timpishka originally formed, one thing’s for sure, any bridge built over this place needs to come with extra-high safety barriers, being boiled alive doesn’t sound like the best way to go.

Recent tales of the Titanoboa and Yacumama definitely make you second guess whether building a bridge over such a wicked waterway is worth it. But scary as these stories sound, they’re more likely down to inaccurate measurements or mysterious, legendary indigenous tales that aren’t necessarily based on anything real. However, that doesn’t mean that the Amazon River is a peaceful paradise!

Amazon River Creatures

While the Titanoboa and Yacumama may not exist, plenty of nightmare-inducing critters lurk beneath the water’s surface. Take the green anaconda, for example. These bulky boys may not be as big as a Titanoboa, but they can still reach over 30 feet long. Luckily these snakes aren’t venomous, but that certainly doesn’t mean that they’re not a danger.

The scary serpents use their strong jaws to capture their prey, before using their thick, muscular bodies to wrap around their kill to suffocate it. Green anacondas can even detach their jaw to swallow larger prey, like caimans and tapir! Fortunately, there’s not much evidence of these serpents dining on humans for dinner!

However, not all critters found within the Amazon River are capable of suffocating you to death, but that doesn’t make them any less menacing. The Amazon’s full of a variety of freshwater stingray species that may look cute, but be warned, these guys pack a punch.

Although stingray attacks on humans aren’t too common, they’ve been known to whip their tails at anyone that gets too close. When a stingray whips its tail against a victim, the spines within the tail pierce the skin. The pain the barbed stinger causes is intense, but compared to the venom some freshwater species inject, it’s nothing.

Initial symptoms include red, swelling skin before the body tissue around the affected area begins to die. If that wasn’t bad enough, stings can also lead to vomiting, sweating, respiratory depression, muscle twitching, and seizures.

In a study from 2020, 27% of people who were stung by stingrays reported further complications in the months after the accident, ranging from numbness, tremors, and even amputations to affected limbs. In Colombia alone, more than 2,000 stingray-related injuries are reported every year.

Venomous stingrays, giant suffocating anacondas, and maybe even a truck-sized serpent or two. We get the picture; the Amazon River is not to be messed with. But the horrors don’t end there. Many of you may think catfish are pretty harmless, so meet the piraiba, the largest catfish in the Amazon.

This frightening fish measures over 10 feet long and weighs around 330 pounds, that’s almost double the size and weight of a typical adult man! But size isn’t the only freaky feature of the piraiba. They’re generally considered pretty harmless, feasting primarily on a diet of other fish. However, their stomach contents have been said to include parts of monkeys.

There’s even been talk that these catfish have an appetite for human flesh! Back in 1981, the Sobral Santos II, a ferry that operated on the Amazon, capsized and sank in the river. Around 500 people were on board, yet only 178 survived. So, what happened to the hundreds of other passengers?

It’s believed that hordes of piraiba were responsible for pulling struggling victims down under the water! When the ship was retrieved from the riverbed a shocking discovery was made: Bodies were found, but they had huge chunks of flesh missing. Piraiba don’t mess around! All of a sudden crossing the Amazon sounds like a death wish.

Today ferries and boats are at hand if we need to cross the Amazon River, not that that’s always saved humans! But back in the day, there wouldn’t have been such luxuries to help people travel the river. After all, indigenous groups have lived throughout the Amazon for at least 11,200 years, long before advanced technology created motorized water transport.

Ancient Amazonian Settlements

Researchers have long assumed that the land surrounding the Amazon River didn’t become densely populated until after the arrival of Spanish colonizers in the late 15th century. The belief was that before the arrival of these foreign explorers, the Amazon was home to small nomadic tribes who left the rainforest in pristine condition.

However, recent technological developments have discovered evidence that blows this assumption out of the water. Lidar, in particular, has been incredibly useful; utilizing a remote sensor, it uses laser beams to pass between the leaves and branches of the trees, bouncing back to provide a 3D image of the ground below the thick canopy.

It revealed that ancient Amazonians built and lived in densely populated centers. These communities featured monumental mounds, 65 feet-high pyramids, raised fields for agriculture, and almost 600 miles of canals and causeways, which were used to connect forest islands.

The researchers also theorized that population densities were much larger than they first thought. Previously, it was believed that about 2 million people lived in the entire Amazon basin. However, it’s now believed that between 500,000 and 1 million people once lived in just 7% of the area! Clearly, the Amazon was much more advanced than anyone could’ve imagined.

And, considering that indigenous tribes were capable of building causeways and canals, who’s to say that there weren’t once ancient bridges crossing the Amazon River, that’ve since been lost to the Amazon jungle? After all, bridges wouldn’t be the first thing to be swallowed up by the great green giant that is the Amazon.

Kuhikugu And The Lost City Of Z

You may know it better from the film, but the ‘Lost City of Z’ is believed to have been a real city that existed in the Mato Grosso region of Brazil. Remember Percy Fawcett? When he wasn’t out spotting hell snakes, he was obsessed with finding this mysterious civilization.

During his trips to South America, Fawcett became infatuated with stories of a city that lay deep within the Amazon. He’d heard tales from the native tribespeople, and later read similar accounts by European colonizers who mentioned that they saw “ruins of size and grandeur which must have been there, and how populous and opulent it had been in the age when it flourished”.

So, in April 1925 he set off with his son Jack and Jack’s best friend, Raleigh Rimmel. But Fawcett wasn’t able to find the Lost City. Ironically, he's never been found either. His last known letter was written on 29th May 1925 at a location called Dead Horse Camp, which stated the group’s plan to head into unexplored territory.

Sadly, Fawcett and his crew were never heard or seen again. No one knows for sure what caused the demise of the group. Some have speculated that local indigenous people were to blame. Others believe that they were struck down by fever, or perhaps they became lost and succumbed to starvation. While it’s unlikely that Fawcett ever discovered the Lost City of Z, his expedition certainly ramped up interest in the curious civilization.

Recently an anthropologist called Michael Heckenberger, with the help of the local Kuikuro people of Mato Grosso, uncovered an ancient civilization called Kuhikugu. Considering it was located 140 miles from the last place Fawcett was known to be alive, Dead Horse Camp, it’s certainly possible that Kuhikugu was the ‘Lost City of Z’ that Fawcett was looking for.

It’s believed to have been inhabited from the year 500 until as recently as 1615 and included 20 towns in an area that spread around 7,700 square miles. Close to 50,000 people may have once lived here! For some context, that was around the same population of London in 1500!

But size isn’t the only impressive thing about Kuhikugu. According to Heckenberger, the engineering of this civilization was advanced enough to build moats, along with bridges that crossed large sections of the river. So, the Amazon River, in history at least, might once have had a bridge! But nothing with this place comes easy.

The site of Kuhikugu is located in Mato Grasso, which is south of the Amazon River. The closest water source to this civilization would’ve instead been the Xingu River, a southerly tributary of the Amazon. But, even if the people of Kuhikugu never built a bridge to cross the Amazon, all hope is not lost.

Thanks to the introduction of lidar technology, as well as the regrettable deforestation of the rainforest, researchers are constantly getting a clearer picture of the ruins left behind by ancient Amazonian civilizations. Who knows, it may just be a matter of time before an ancient bridge-building civilization, like the one at Kuhikugu, is found on the banks of the Amazon River!

Unearthing The Ancient Amazonian Landscape

There is one teeny tiny problem, however. If the Amazon was home to such advanced societies, what could’ve possibly happened to all of the civilizations and the structures that they once built? They couldn’t have just vanished! Maybe Yacumama swallowed them up? Luckily that wasn’t the case, but the true story isn’t much more cheerful.

In 1541, Francisco de Orellana sailed the length of the Amazon River, becoming the first European to do so. That led the way for many more explorers to delve into the mysterious marvel in the coming years. But Europeans weren’t the only thing to arrive on the shores of the Amazon. With them, they brought diseases like smallpox and measles.

Because the untouched tribes of the Amazon had never come into contact with these illnesses, they had no immunity to them. As a result of exposure to foreign diseases, and the notoriously brutal treatment from colonizers, the Amazonian population was reduced by 90% within just 100 years of the arrival of Europeans.

But even if the people were virtually wiped out, that still doesn’t explain why advanced technologies, like lidar, are needed to discover settlements. After all, ancient civilizations in places like Greece, Egypt, and Mexico have ruins from thousands of years ago that are still standing today! So why doesn’t the Amazon have its own acropolis or stone pyramid?

Unlike the stone structure of those ruins, the Amazon’s indigenous people built with wood and earth. They’re obvious building materials, given their abundance in the rainforest. Unfortunately, though, wood decays if it’s not maintained. And as a result, potentially countless bridge ruins from bygone Amazonian civilizations seem to have been swallowed up by the jungle!