Alcanar has become the perfect storm, the Catalan epicenter of the climate emergency next to the Ebro delta. We must act to mitigate the effects of the floods and we must do it quickly, agree the experts consulted. Intervene in the short but also in the medium and long term urban planning in the flood-prone areas next to the ravines, including expropriations, but with many other interventions.
Concrete measures must be applied already in the study phase to contain and laminate the large avenues of water launched from the Montsià mountain range through the dozen ravines that flow into the sea in the inhabited areas of Alcanar Platja and Les Cases d'Alcanar. They are always the most affected by floods, with the mixture of water, stones, mud, branches and dirt.
“It's about reducing flooding; There will be floods yes or yes, no one has any doubt, but they can be mitigated”, points out Roger Sauquet, professor of Architecture at the UPC and member of the GREC-Bombers (Group of Collapsed Structures). Sauquet has intervened in the latest floods in Alcanar (2018 and 2021) and has directed a UPC study to find solutions.
The most urgent are the urban centers of Alcanar close to the sea, but without forgetting other localities such as neighboring La Ràpita, Ulldecona or Santa Bárbara.
If structural action is not taken, the increasingly frequent extreme weather events will continue to cause flooding and million-dollar damage to public and private properties. There are not only houses, businesses and infrastructures in danger.
“The water takes what is its own, in Alcanar as in other municipalities they are heirs to an urban development from the seventies without planning tools. No matter how much we warn the population, many times the only way to protect Les Cases d'Alcanar or Alcanar Platja is to tell the residents to go up to high points in their houses, evacuation is impossible”, explains Rafael Prades, person in charge of Protection Civil in Terres de l'Ebre.
It is not by chance or by any atavistic curse that Alcanar has suffered three floods in five years (2018, 2021 and 2023). Causes and determining factors have been identified.
The orography, next to the sea, and with the Montsià mountain range (764 m) behind us. The terrible urban planning, with buildings next to ravines where the water precipitated in the mountain seeks its way out to the sea. And the climate crisis, which explains why meteorological phenomena (DANA) are becoming more frequent and more extreme.
There is hope because there are ways to intervene, with ongoing actions, according to experts in emergencies, architecture or the climate crisis. Of course, enough of putting more patches or limiting ourselves to rebuilding the most affected areas, as has basically been done until now with the scarce and late public aid.
"We have to act to give more space to the water, we have to rebuild differently and deconstruct in some cases, plan and make new legislation. There are many measures to implement, we have to rethink the coast", says Carles Ibáñez, director of the Climate Change Hotline (Eurecat) and the Climate Resilience Center (CRC).
Larger public investments will be needed. It is a complex action, between the public and the private, with expropriations of houses and the exchange of private lands now developable in the area of influence of the ravines. The affected owners must be compensated because the vast majority bought or built legally.
“We recommend as an emergency measure to use the still empty spaces next to the ravines and consider them floodable green areas. They are a treasure to mitigate floods. But many of these areas are today classified as developable,” warns Sauquet (UPC and GREC-Bombers). It is also planned to use agricultural farms to laminate the ravines with compensation for farmers.
“Some houses, plots and equipment will probably have to be expropriated to renaturalize the water circuit. It is the definitive solution to be studied by a technical commission with the involvement of the Government and the Generalitat,” says Joan Roig (ERC), mayor of Alcanar.
As if they were the foundations on which this serious problem is based, the location of Alcanar and its orography. An important part of the municipality is next to the sea, at ground level, but it has the Montsià mountain range right on its back, a few kilometers away.
When the torrential rains fall on the mountain, the water, converted into multiple torrents, seeks its natural outlet towards the sea through the ravines. The problem is that, due to the non-existent urban planning of the 60s, 70s, 80s and even 90s, it has been built and urbanized along several of the ravines in its final stretch. There are three destructive ravines: Sant Jaume (Les Cases d'Alcanar), Llop (Alcanar Platja and the Alfacs Camping) and Codonyol, between Alcanar and La Ràpita.
It points to the expropriation of several dozen houses in these areas. Fifty hundred has been given as a reference figure, but it is only an approximation. If other containment measures are applied, they will be less. “We propose allowing the houses to be raised one more floor to force that no one can live on the ground floors. In the most affected houses, the water has entered again through a door and has taken it out and destroyed everything on the other side, leaving everything full of water and mud, next to the Càmping dels Alfacs ”, adds Sauquet.
The steep drop, more than 700 meters from the mountain to the sea in just five kilometers, multiplies the speed with which the water flows down the ravines and the probability of collapse.
“The occupation of ravines accelerates the speed of the water and increases the capacity for destruction in urbanized areas near the coast,” adds Ibáñez (Eurecat). The ravines overflow and become runaway torrents causing floods also far from their channel, as happened in 2021.
The particular coastal orography of Alcanar has an enhancing effect when the cold drops of late summer arrive. The sea water reaches its maximum temperatures between the end of August and September, when the DANA usually arrive. The perfect Storm.
The mountain itself next to the sea retains the storms coming from the coast, anchoring the disturbances next to Alcanar, which amplifies the precipitations. “The Montsià mountain range, very high and very close to the sea, is a key factor. The cloudiness remains anchored in the mountain, which acts as a barrier and lever; It feeds back on the clouds and the precipitation does not stop for hours,” highlights meteorologist Xavi Segura.
With the climate emergency, the maritime storms are also increasingly stronger and the sea level higher, punishing an increasingly fragile coastline, as has been evidenced throughout the Ebro delta.
“We are risking people's lives, there is a real risk, we must focus investment on preventive measures for floods. The political discourse is exhausted, it has no further scope, we must move on to the technical discourse at once,” cries its mayor.
