Why does the Baix Ter flood when it rains?

During the easterly winds of two weeks ago that hit Catalonia hard, The Empordà plain was completely floodedEspecially the entire stretch of the Baix Ter, on both sides of the riverbeds before the mouth, with crops ruined, roads closed, and beaches covered in sediment. Even the Ullà retaining wall, a 17th-century structure, was breached, suffering structural damage from the storm. Glory In 2020, a project diverted water from the river through irrigation ditches and streams for surrounding crops. Two weeks later, the damage is still visible: fields are covered in puddles, rural roads are damaged, streams continue to flow strongly, and the Ter Gorge is full of logs and debris. Repairing it will cost the local councils and farmers thousands of euros, and they have already requested assistance from the Catalan government. And this is by no means the first time this has happened: every five to eight years, when there is heavy rainfall in the region or when the river is full due to torrential rains in the Pasteral reservoir basin, the situation repeats itself. In fact, according to the Catalan flood zone map, the area between Girona and Estartit is one of the largest flood-prone zones in the country. For all these reasons, mayors, business owners, farmers, and scientists are demanding improvements and working on new initiatives to prevent, as far as possible, the effects of future floods. The region's main complaint focuses on the state of the roads, which on days of heavy rain makes it impossible to travel by car between municipalities such as Ultramort, Verges, Jafre, Sierra de Daró, Torroella de Montgrí, and Pals. The Central Board of Users of the Baix Ter, which represents some forty municipalities, private landowners, and the irrigation community, laments this situation: "Any emergency becomes extremely complicated and puts the safety of people at risk, for example, those who need to go to the hospital in Palamós or travel for family reasons," explains Francesc. €50 million to improve roads

This is a long-standing demand: to raise by half a meter roads that haven't been upgraded in decades, with narrow lanes, often two-way, and without shoulders that run directly onto the ditch. After several meetings, the Generalitat (Catalan government) has committed to this, and the Department of Territory, just before the outbreak of commuter rail chaosThe Catalan government presented the mayors with a comprehensive program of actions to improve the roads of the Baix Ter region, with a total investment exceeding 50 million euros. The main project will be the improvement of the Verges–Colomers route (GI-633 and GI-634), with a budget of 14 million euros, which includes widening seven kilometers of road and improving its alignment. The project will be put out to tender in the second quarter of this year, and work will begin in winter, along with other improvements to secondary roads. In parallel, following the effects of the storm, the Catalan Water Agency (ACA) also intends to launch a comprehensive flood risk study of the Baix Ter region to define structural measures and reduce risks.

Promote infiltration

But what are the geographical and hydrological reasons that explain this natural tendency of the Baix Ter to become a large wetland when it rains? To begin with, it is a plain with sandy and clay soils, with few changes in elevation, and crossed by the Ter and Daró rivers and several streams, all of which flow into the sea. But this sea, when it has waves, also acts as a plug and makes it difficult for the river to flow into the river in a torrent.

To all this must be added the impact of human constructions, which, although deliberately located in somewhat elevated areas, are made of materials that repel water. "Urbanized areas cause rainwater to flow more quickly and with greater force towards the rivers and streams," explains Xavier Quintana, an ecologist at the University of Girona (UdG) and a specialist in the Baix Ter region. And, regarding the impact of the water released from the Sau and Susqueda reservoirs, he adds: "When the Pasteral intake is suddenly released because it has reached its capacity, the river water flows very quickly, making it difficult for it to infiltrate the subsoil and recharge the aquifers." Quintana also argues that it is necessary to improve the management of riverbeds and agricultural irrigation ditches to channel water to the sea with suitable vegetation. "The native vegetation of Mediterranean dry riverbeds bends with the water and slows the flow, but invasive species, such as reeds, can worsen flooding," he points out. Regarding reservoirs, he concludes that, despite reducing the frequency of floods, they can create a false sense of security: "There is always a point at which rainfall exceeds the capacity of technology." Lamination, retention or ancient meanders

In this context, projects like Hidronet Baix Ter, promoted by the Ter Consortium and the Girona Provincial Council, take on special significance. Now in its third year, this project aims to prevent flooding by fostering aquatic biodiversity and implementing flood control structures to slow water flow. "Zero risk doesn't exist. It's about improving critical points and learning to live with it," explains Teia Puigvert, director of the Consortium. She adds, "We must consider long-term solutions such as managing levees or encouraging the flooding of agricultural areas, compensating for losses while preventing harm to the population." Other measures already underway include retention ponds at the mouth of the Ulla River and in the former Ullastret pond, the restoration of old meanders, and urban planning adapted to the situation.