Tuesday, December 6

Barcelona’s beaches could disappear in 30 years: “Without sand, storm surges will not be able to be stopped”


Last summer, the coastline of the Metropolitan Area of ​​Barcelona (AMB) saw how many of its beaches almost disappeared. This is the case of cities such as Barcelona, ​​Badalona, ​​Sitges or Montgat, where a few months ago there were barely 500 meters of sand left, when before there were more than 2 kilometers. This year has been one of the most disastrous for the Barcelona coastline, which began the season with 15% less sand. But it is not a new situation: it has been going on since 2014, when more frequent and violent storms began to be recorded, which gradually removed the sand from the coast.

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Due to this situation, the AMB has carried out various studies to be able to put figures on the dynamics of the coastline and propose appropriate actions. The most significant conclusion of these investigations is that, if we do not act accordingly, the beaches could lose more than 20 meters in 30 years, which would mean that many of them could disappear. In fact, all beaches recede, on average, one meter each year.

Much of the blame for this setback is, in addition to climate change, human action. According to the AMB, the Llobregat river dam and the Port of Masnou have a negative role in the regeneration of the beaches that surround them. “They act as a trap for sediments, which go down to them and remain stagnant,” says Daniel Palacios, head of the AMB beach service. These constructions, therefore, have put a brake on the natural dynamics of contribution and transport of sand from the beaches.

And the coast regulates itself. Or, at least, it did before human intervention. Urbanization means putting up barriers to the free circulation of sand and also eliminating elements of natural protection against storms. “Without sand, storm surges will not be able to be stopped and they can reach the promenades, further deteriorating the state of the beaches,” says Palacios.

The dunes, for example, are reserves of sand that the coasts have to supply the sediments that the storms take back to the sea. And, in addition, they also protected from the waves. So, by eliminating them, they have had to build artificial protection elements that can be more harmful than beneficial.

“When a wave finds a natural beach, the energy is dissipated in the sand. But if we build barriers, the shock energy is concentrated and causes the wave to carry more land towards the sea”, explained this summer Joan Vilaplana, director of the georisk observatory of the Col·legi de Geolegs de Catalunya. That is why the AMB is committed to creating a system of submerged sand barriers to try to protect the coastline.



Resume transfer of sand

Faced with the impossibility of demolishing elements that, such as ports, act as a block for the free circulation of sand, the AMB is committed to dividing the beaches, so that the sand does not remain accumulated in a few points and its distribution is favored. Another of the actions planned by the AMB is the transfer of sand from the beaches that have more to those that are running out. From the administration they calculate that more than 450,000 tons of sand will be necessary to stop the retreat of the beaches.

Even so, they warn that this technique is not a panacea. The transfer of sediments, normally, is deposited in the submerged areas, in such a way that the beach can regenerate -almost- alone. This simply serves to slow down the retreat, but does not add more sand to the visible part of the beaches, which are already badly damaged. Therefore, the measure has to be “specific and should not be the only one because, in many cases, it is ineffective,” according to Palacios. For it to work, various factors must be taken into account, such as the wind in the area, the weight or the type of sand.

According to experts, transferring sand has another risk: by removing the earth, the loss could be greater than the contribution. According to data from the AMB itself, for every 100 cubic meters of sand that is removed, almost 150 are lost.

The transfer of sand, which was very popular in the eighties, ceased to be practiced in 2010. The last of these interventions, which depend on the Ministry of Ecological Transition, cost 170 million euros between 2004 and 2010 to provide 600,000 cubic meters of sand. Taking into account that the price per cubic meter is six euros and that some 30,000 cubic meters of sand are lost each year, the sea has swallowed more than 1,500 million euros in the last decade.

Even so, from the AMB they extend their hand to MITECO so that it resumes these actions and to be able to guarantee the continuity of the beaches of the Catalan coast. One of the techniques for this is the so-called bypass, consisting of taking the sediment by boat and this is proposed, especially, for the port of Masnou. This is a somewhat different technique to the traditional transfer of sand, since the sediments are not deposited in the underwater bed, but rather in the dry part. This would mean an immediate recovery of the beaches and would stop the clear decline.



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