“Water covers 70% of the planet. » The scene of the documentary. When the sea threatens the cities, broadcast Thursday night in prime time on France 5, stands up with ease. For several decades, human activity has led to global warming and that of the oceans. The level of the latter increases and impacts the coastal areas of the different islands and continents. “Nearly 800 million inhabitants are directly threatened by rising waters”, emphasizes the film by Laurence Thiriat, due to the proximity of many large cities to the coast. New York, Rotterdam or even Singapore are used as examples of these megalopolises that must constantly adapt their coastline to rising waters. In America, Europe and Asia, researchers and scientists are looking for technological solutions that can stop the phenomenon.

The Mercator oceanographic center, located in Toulouse, registered unspeakable people on the oceans and souligne that, after 1993, the level of the sea at a rate of 3.4 millimeters for an, soit a total of 10 centimeters to this day. “We cannot rule out a rise of up to two meters by the end of the century”says oceanographer Angélique Melet, who details the two main causes. “The ocean is warming and the water is expanding, absorbing more than 90% of the excess heat on Earth. And the glaciers like the polar ice caps are melting, the water running into the oceans like a faucet would fill a bathtub. » Depending on the local climate and sea currents, the rise in water is more or less important. In Asia, Singapore has been artificially deployed to the sea during the last decades and runs the risk, due to its geographical location, of being partially submerged.

“In Europe, the forecasts for 2050 are worrying”

There are many experiments to try to contain the phenomenon. In Singapore, the greening of buildings is increasing to absorb some of the CO2 gases and freshen the city’s air. Investments in renewable energies are becoming more and more important. At a technological level, a drainage system and hydraulic pumps have been put in place to evacuate rainwater and the construction of a marine dam equipped with a reservoir that allows fresh water to be stored. In New York, “one of the most threatened cities in the world”a collective is trying to restore a place for oysters on the surrounding seabed for its water-filtering properties and its ability to contain the movements of the sea. The most promising project it’s the one with this U-shaped belt, the “Big U”that would come to protect the island of Manhattan by restoring the coastal relief and building protective barriers to limit the risk of flooding.

read the fileThe fight against global warming, the great challenge of the 21st century

In the Netherlands, several experiments were carried out in Rotterdam to combat the adverse effects of North Sea storms. A work undertaken since the Middle Ages with the drainage of the marshes through a network of canals and the installation of dikes and then large anti-storm dams. The Dutch city has become the largest port in Europe and one of the most important economic centers in the country. “In Europe, the forecasts for 2050 are worrying”, advances the documentary mentioning the Netherlands, northern Germany, Belgium and France as well as the east coast of the United Kingdom as the areas most threatened by future maritime fluctuations. The Dutch dikes will not be enough to contain future floodwaters and the project to raise them runs up against to the scarcity of the resources necessary for its construction, such as clay. “In 2050, 140 million people around the world will be destined to become climate refugees. An inexorable change in the history of humanity that will have to reinvent itself to survive”concludes the documentary France 5.