Society 01/11/2021

The Ebro delta, a European laboratory for the climate crisis

EU triggers pilot test of sediment transport from the Riba-roja reservoir to halt coastal regression

4 min
The Vasco restaurant has been surrounded by rocks to protect it from the sea at the Marquesa beach

BarcelonaIf there is somewhere close where we can already see the effects of the climate crisis it is the Ebro delta. It is like watching the sea level rise at an accelerated rate, not because the water is rising more than in other coastal areas, but because, in parallel, the Delta is sinking (due to the phenomenon known as subsidence) and the coastline is retreating due to the lack of sediments that reach it. "In the Delta we are experiencing what our beaches will suffer in 2050 or 2070, and this makes it an excellent natural laboratory in which to test solutions," explains UPC professor and director of the Maritime Engineering Laboratory, Agustín Sánchez-Arcilla.

So far in the Ebro delta "a lot has been studied and little has been done," admits Sánchez-Arcilla. The difficulty in bringing together the many players involved (various administrations, organizations, individuals) and also the lack of funding stranded concrete actions that go beyond addressing the emergency after a storm. Now, however, a European project (the REST-COAST) puts the Ebro delta in the spotlight and can accelerate actions. Funded with €18m and, in the case of Catalonia, led by the UPC, the project identifies 12 priority coastal points where urgent and structural solutions for restoration and protection against the onslaught of climate change must be deployed. Three priority sites have been identified, which are, in addition to the Delta, the Venice Lagoon and the Wadden Sea in the North Sea.

For Catalonia, the project will be an opportunity to carry out a pilot test of sediment transport in the Ebro Delta, a historic proposal that can alleviate the regression but has never been carried out before. The European push can be twofold: firstly, it provides resources for the drafting of the project, the analysis and monitoring, and secondly, it establishes that the competent administrations – in this case, the Spanish Ministry of Ecological Transition and the Generalitat – must be partners in the project and will be responsible for financing the pilot test, that is, the actual transfer of sediments.

The project will analyse how to transport them from reservoirs, "the closer to the Delta the better," says Sánchez-Arcilla, who holds back any names. The Catalan Government, however, does not: the sediments will come from Riba-roja reservoir. "The test wants to mobilise 100,000 cubic metres through controlled outflows from reservoirs, the general director of Environmental Policies, Antoni Ferran, explains to ARA. These will mean the river will transport the sediment through its natural course to its mouth. Doing it with trucks is ruled out due to the impact in terms of emissions it would entail, says the professor of the UPC, who insists that one of the EU's conditions is that the solutions to be tested are natural and low impact.

In addition, so that the Delta does not suffer the same fate "as Maresme beaches", continues Sánchez-Arcilla, these sediments will be fixed by planting a lot of vegetation very irregularly to better dissipate the energy of the waves and storms. "One of the keys is that, for the first time, civil engineers from the UPC and biologists from Eurecat are working together, something that seemed unthinkable", claims the project director. The pilot test does not solve the problem in the Delta, but it is a start which will allow sediments to arrive in sufficient quantity, a fact that should not be extraordinary but natural, Ferran says.

The UPC expert admits that the issue of sediment is particularly delicate: "We have to be careful what we do because floods are made sacrificing other uses of water (irrigation or electricity generation) and at a time with less fresh water available the balance is very complex. In fact, this point is a source of disagreement between the Ebro Hydrographic Confederation (CHE), which depends on the Spanish ministry, and the entities present in the Consensus Table for the Delta, which ask to review the basin plan and to guarantee ecological flows in the river to allow the arrival of sediments.

The REST-COAST project also includes setting up a kind of laboratory in the Ebro delta where the conditions of temperature increase predicted for the coming decades will be recreated to observe the reaction of vegetation which is to be planted in the coastal area to mitigate the effect of storms. "They will be like greenhouse huts where we will heat the air and the ground by 1.5 degrees to see the interaction between the water and the plants," Sánchez-Arcilla describes.

An inevitable scenario

At the rate at which greenhouse gas emissions are increasing, the planet is warming and sea levels are rising, adaptation is the only way out for coastal areas . The EU wants all pilot projects to be applicable in places with similar conditions and characteristics, because it predicts that the actions on the coasts will be many and varied in the coming decades. "The Ebro delta is a lighthouse, everything we are able to do well there will help us to go in the right direction to address other situations in deltaic areas or wetlands in Catalonia," says Ferran.

Sánchez-Arcilla recalls that even if the Climate Summit taking place in Glasgow - the COP26 - came up with maximum commitments to curb global warming, this would not stop the already guaranteed rise in sea level. "The thermal inertia of water is so great that even if we put coolers in the atmosphere, the water would continue to expand," he explains. How far this increase will go depends on the scenarios that scientists draw: the most optimistic speak of an average rise in sea level of 50 centimetres by 2100; the most pessimistic thesis say it could reach almost a meter.

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