Valencia could have been completely submerged during the recent flooding if local authorities had not previously diverted the Turia River away from the city.
The autonomous community of Valencia, located on the eastern coastal region of Spain, experienced one of the worst floods in decades following torrential rain last week. According to meteorological agencies, nearly a year’s worth of rainfall fell on the area within just 8 hours, causing unprecedented damage and resulting in over 200 fatalities.
The storm, which began on October 29, was the result of a dangerous weather phenomenon known as DANA in Spain. Short for “isolated low pressure at high altitude,” DANA occurs when warm air over the Mediterranean Sea meets cold air in the atmosphere, creating volatile climatic conditions that lead to heavy rainfall. Experts suggest that this pattern is becoming increasingly common due to global warming.
Vehicles piled on top of each other after the flood in Valencia. (Photo: David Ramos).
While the province of Valencia is prone to flooding, local residents were unprepared in part because emergency warnings were issued too late. Many received alerts only after the streets had turned into rivers. Residents also did not anticipate such an event, believing the area to be safe from flooding after the Great Flood of Valencia in 1957. That flood prompted local authorities to undertake an ambitious project to divert the Turia River away from the city.
Initial assessments indicate that on October 29, the riverbed south of Valencia helped mitigate the disaster. Although it is still too early to analyze the overall impact of the flood, some experts believe the city could have been completely flooded without the river diversion project known as Plan Sur.
Valencia has faced several similar disasters over the past centuries. The city is situated in a low-lying area next to Albufera, the largest freshwater lagoon in Spain. This makes the region particularly susceptible to flooding. Several DANA storms have caused disasters in the area over the decades, with the worst being the Great Flood of Valencia in 1957, during which approximately three-quarters of the city was submerged and over 80 lives were lost.
DANA storms are relatively common in the Mediterranean. The interaction of warm and cold air leads to the formation of dense rain clouds. Once they move inland, they can drift slowly over large areas. Such storms often cause severe flooding.
Valencia underwent a complete transformation following the flood of 1957. After that year, authorities planned to divert the Turia River, Spain’s longest river, around the southwestern suburbs of the city and towards the Mediterranean Sea. The Plan Sur project was devised to prevent such disasters from recurring. Essentially, the project’s goal was to redirect the river away from the provincial capital.
As an impressive achievement in hydraulic engineering, the diversion process was completed in 1973. Today, the new riverbed can handle a flow of more than 5,000m3 of water. In comparison, the old river flowing through the city could only contain 3,700m3 of water before overflowing. The most recent flood marked the first overflow since the completion of the Plan Sur project. “If the river had not been diverted, Valencia would have been completely flooded from north to south,” said Federico Bonet from the Valencia Association of Civil Engineers and Canals.
While the river diversion project has saved many lives in central Valencia, there are still many questions about its overall impact. The new riverbed to the south can hold a larger volume of water, which theoretically means that residents in that area should be safe. However, in the past, many politicians and scientists have warned that the Plan Sur project is incomplete and could potentially lead to disasters.
During the construction of the riverbed as part of the Plan Sur project, authorities intended to create a large basin with a capacity of 164 million m3 of water under the regime of dictator Francisco Franco. However, Franco’s regime ran out of funds, and the basin was never completed. Since then, many have called for the project to be completed. For example, in 2010, the mayor of Valencia urged the Spanish government to finish the Plan Sur project. The flood at the end of 2024 and its consequences will be part of the analysis of the impact of the river diversion project in Valencia.
