00:00A bridge, an essential structure whose existence dates back to the Neolithic.
00:06The oldest still standing is the Mycenaean bridge of Kazarma, built more than 3,000 years ago.
00:13But it is a river that no bridge can cross.
00:17The Amazon, the most important watercourse on the planet.
00:21Certainly, the Nile officially holds the record for length, but the Amazon is well known for both titles.
00:28Born in Peru, the Amazon River crosses Colombia and Brazil before throwing itself into the Atlantic by a gigantic delta.
00:36Its route even exceeds the journey of Sam and Frodon.
00:40And yet, no bridge can cross it.
00:43So why?
00:46First of all, these seasonal creeks radically change the flow.
00:51In dry periods, they spread over about 5 km wide.
00:55But under the effect of floodwaters, it can reach up to 50 km in a few weeks.
01:01In addition, these creeks move the bed of the river.
01:04Building a bridge on a land that is metamorphosed by spreading water for 4 months of the year
01:10is a considerable technical challenge, but not out of reach.
01:14Remember your geography classes.
01:17River banks, especially in the Amazon, are often unstable and prone to erosion.
01:23Torrential rains also generate tides, a real natural regulator of the creeks,
01:29which filter the water and shelter a fauna of great diversity.
01:33This implies that part of this humid area should be drained to allow the construction of a bridge,
01:40which would cause irreparable damage to the local fauna.
01:44In addition, the foundations necessary for this bridge should be deep, causing considerable costs.
01:51Rain causes another major problem in this project.
01:54It causes an elevation of the water level that can reach 13 to 15 m.
01:59Of course, bridges have been built above deep watercourses,
02:03such as the Padma Bridge, a colossal structure with a foundation of 127 m.
02:09However, due to the rapid erosion of the Amazon soil,
02:12the bridge should be designed from floating structures, called pontoons,
02:17which are not suitable for a river whose depth fluctuates at will.
02:21Now let's move on to another major obstacle for human engineering.
02:25The Amazon forest.
02:27Spread over 9 countries, this forest is so vast and dense
02:31that it could cover almost half of Europe.
02:34As a result, a bridge would most likely connect two sections of the forest,
02:39bringing insignificant progress for the local fauna, such as capybaras and jaguars.
02:44Naturally, the main beneficiaries of such a bridge would be humans.
02:48Indeed, most of the local population is spread out around the Amazon reefs,
02:53far from the river itself.
02:54After all, who would like to live like a beaver on the edge of a dam?
02:58There is even a state, Lamapa, on the left bank of the Amazon,
03:03which is completely cut off from the rest of Brazil.
03:06You could easily visit its neighbor, Guyana.
03:09But to reach a different region of Brazil,
03:12you would have to resort to other means of transport.
03:15With the exception of small riverine communities
03:18that live directly on the banks of the river,
03:20which goes without saying,
03:22large cities have been established near tributary rivers,
03:25such as the Rio Negro, which has a bridge,
03:28or the Nane river, in Peru.
03:30The bridges that make up the Nane and the Rio Negro
03:33are the only two structures of this kind in the Amazon basin.
03:37The lack of road infrastructure in the Amazon
03:41also makes the construction of bridges completely superfluous.
03:44In the 1970s, humanity was full of great ambitions
03:48to explore the Amazon more.
03:50It was in this spirit that they envisaged the construction of a highway
03:53crossing the Amazon basin from one end to the other.
03:56The Trans-Amazonian Highway,
03:58supposed to facilitate access to the heart of the forest,
04:00however, failed to meet these objectives.
04:03It seems that the difficulties related to the construction
04:06of more than 3,200 kilometers of road
04:08in the heart of a dense tropical forest
04:10were not anticipated.
04:12Halfway through, the project was abandoned
04:15due to its exorbitant cost
04:17and the many problems encountered.
04:19And today, the highways of the Amazon basin
04:22are constantly flooded,
04:24full of crevasses and mud.
04:26This situation creates a vicious circle.
04:29People do not settle near the river,
04:31and access to it is difficult.
04:33Roads do not lead there,
04:35because their construction is extremely complex.
04:37And this leads even fewer people
04:39to settle on the banks of the Amazon,
04:41due to the lack of roads to get there.
04:43So, in the absence of roads and bridges,
04:45how do the inhabitants survive in this region?
04:47You will not believe it,
04:49but the riverine populations use
04:51an invention as old as reliable,
04:53the boat.
04:54The Amazon river is entirely navigable,
04:56and the inhabitants use it as a road.
04:58Just like for motorcycles, cars and buses,
05:01the Amazon has canoes,
05:03outboards and ferries.
05:05There is even a specific ferry
05:07called Obidance,
05:09which serves the locality of Obidos,
05:11hence its name.
05:13The locals do everything on boats.
05:15They even have a floating hospital,
05:17which moves from city to city
05:19to treat the riverine populations,
05:21as well as a floating bank,
05:23where one can make all these transactions
05:25while admiring the immensity of the Amazon.
05:27Honestly, what a brilliant invention!
05:30The absence of bridges, however,
05:32has a major drawback.
05:34It prevents the exploration of real hidden treasures.
05:37For example, in the Amazon,
05:39there would be more than 10,000 archaeological sites
05:41still unknown.
05:43We may never be able to discover
05:45some remains, such as fortified villages,
05:47geoglyphs and other structures.
05:49It would be exciting to relive
05:51the adventures of Lara Croft
05:53in the heart of the Amazon,
05:55but this remains well hidden
05:57in the depths of the forest.
05:59On the other hand,
06:01only in boats can we observe
06:03this incredible phenomenon
06:05where the waters of the Rio Negro
06:07and the Solimo
06:09refuse to mix in the Amazon.
06:11For more than 5 km,
06:13these two streams flow side by side
06:15without mixing.
06:17The speed and temperature of the waters
06:19being different,
06:21you will observe a river
06:23and an impressive phenomenon
06:25known as the Water Encounter.
06:27The Amazon is not the only
06:29watercourse in the world
06:31considered to be without bridges.
06:33The Congo River,
06:35the second longest river in Africa,
06:37has only one bridge crossing it.
06:39The Congo-Brazzaville
06:41and the Congo-Kinshasa
06:43are separated by this river
06:45and to this day,
06:47no road has any connection between them.
06:49A little anecdote.
06:51At the time when the supercontinent
06:53of Gondwana existed
06:55and that all continents were united,
06:57the Amazon and the Congo River
06:59formed one and the same river,
07:01connected between them.
07:03Another place where the bridges make mistakes
07:05is located on the east side of the Thames,
07:07in London.
07:09The western part of the east river
07:11is narrower,
07:13which makes the construction
07:15of the bridges simpler.
07:17There are about 33 bridges
07:19In the 19th century,
07:21maritime companies estimated
07:23that building too many bridges
07:25on the Thames would be too expensive
07:27because this area was part
07:29of a navigation route
07:31and its bridges should be
07:33much higher than normal.
07:35Their structure should also
07:37be particularly long
07:39given that some sections
07:41of the Thames are
07:43nearly 570 meters wide.
07:45However, the construction
07:47of the bridges is only 13 kilometers long.
07:49When it was built in the 1970s,
07:51it was the second longest bridge
07:53in the world.
07:55This structure is so vast that in 2018
07:57a little girl was born
07:59while her mother was crossing it
08:01and since then the place
08:03inscribed on her birth certificate
08:05is neither more nor less than the bridge.
08:07There is no possible turn,
08:09so if you take it by mistake,
08:11prepare for a long journey.
08:13So, the next time you decide
08:15to visit the Amazon,
08:17don't forget to bring your own canoe.
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