The Tragic Valencia Floods—A Call for Proactive Coastal Management and Coordinated Action
Collaboratively written by Jacinta Hamley, Gonéri Le Cozannet, Carme Machí Castañer & Paul Sayers
The recent floods in Valencia have left a heart-wrenching toll on the region, where days of relentless rain culminated in a disaster of unprecedented scale. Over 200 lives were lost, communities were displaced, and critical infrastructure was left in ruins. This has crippled the area, and it will take a lot of time, money and people’s effort to get the communities out of an emergency situation, let alone back to a new normality.
Even though it is obvious that flooding events, such as the one now, have been occurring chronically in the Eastern Mediterranean region of Valencia in Spain from September to November, human-induced climate change has exacerbated these events, making them more intense and frequent and accompanied by unforeseen warm core storms.
The impacts went beyond only climate change; local land-use planning, stormwater and wastewater management, and inadequate, disjointed river basin management limited the area’s resilience to extreme weather events. Urban development on floodplains further heightened flood risks, especially in areas exposed to preferential river overflow pathways, simulated in hydrological models with intense rainfall and a 100 to 500 return period*.
The Need for Proactive Action
Climate change is fueling more heavy rainfall events and unforeseen extreme weather phenomena at the same time that sea-level and global warming temperatures rise, driving more coastal marine flooding. In the particular case of the nearby region of Valencia, where the Magro and Jucar Rivers overflood, the Albufera Lake, one of the most ecologically valuable landscapes of this peninsula, helped as a buffer to retain tonnes of sludge and water before draining them directly into the sea.
This disaster highlights the urgent need for real-time meteorological-hydrological-hydraulic modelling encompassed with alert systems to improve readiness for extreme and unforeseen climate-related emergencies. Strong adaptation and mitigation strategies that include a holistic understanding of the entire river basin, land-use spatial pattern, hydrological infiltration and retention rates, and defence systems are also needed.
Data and modelling services are essential here, as they incorporate information to support forecasting and bring in multiple critical scenarios to react and wisely manage the coastal territory, including both the land-use spatial planning and the hydraulic defence and active infrastructure for flood management. CoCliCo is an example of one such service specific to marine surges and coastal risk from sea-level rise. Our platform informs people, from citizens to decision-makers, about present and future coastal flooding risks from sea-level rise and supports adaptation and mitigation efforts to counter this.
Information is only one piece of the puzzle. For effective adaptation and mitigation, we need decision-makers to use all of this science-backed knowledge to take action. COP29 offers an opportunity to progress, particularly on climate finance and funding, and to protect those on the front lines of these climate impacts.
The Impact of Climate Change on Events Like the Valencia Floods
The Valencia flood disaster was catastrophic, causing extensive damage to critical infrastructure, including homes, public buildings, vehicles, power networks, roads, and highways. Tragically, many lives were lost, and numerous people suffered serious injuries. Recovery will take not only weeks but months, or even years, to reach a “new normal.” Hydraulic engineering experts estimate that the flooding across the Turia, Jucar, and Magro river basins in the Valencia region, Spain, has caused damages exceeding 30,000 million euros (ABC, 2024).
It was fueled by climate change: abnormally high sea surface temperatures in the Atlantic are increasing atmospheric moisture, and the higher temperature in the western Mediterranean region favours the formation of such extreme thunderstorms. Thus, these high-altitude isolated depressions, known locally as DANA, drew in moisture from warmer-than-usual waters, leading to intense downpours. As projected decades ago, such extreme rainfall events fueled by climate change have become more intense and frequent as the atmosphere and oceans continue to warm (Earth Observatory, Climate Central, ClimaMeter). Analysing the precipitation, we find that extreme rainfall on October 29th lasted approximately 24 hours, with accumulations reaching up to 450 mm/m² in certain areas. The average precipitation across the affected area was 100 mm/m², placing this event within the statistical range of a 100- to 500-year return period*, meaning it was possible but very unlikely. The upper and middle sections of the Poyo watershed saw rainfall levels higher than ever recorded for such a short period. Heavy rainfall was concentrated in the upstream and midstream areas of the Magro River, while the downstream area received much less. Similar extreme events have been recorded, such as storms on October 14, 1957, and the Tous Dam incident in 1982 (accessed via AEMET and avamet). We now know these events are not isolated incidents but part of a larger global pattern influenced by human-caused warming.
The Impact of Planning and Management
While climate change fueled extreme weather, factors such as land-use planning and infrastructure management compounded the storm’s impact.
Local land-use planning also influenced the severe effects on the region, intensifying the damage caused by extreme weather. Key contributing factors included patterns in spatial planning, land-use decisions, and standard practices in stormwater and wastewater management (Marcos-Garcia et al., 2023, Machi-Felici, 2008). “We are in a floodplain. We have built more than we should over the last 25 years (…)” (Javier Machi, dean of the Valencian Community College of Civil Engineers, translated in La Vanguardia)
In addition, a lack of integrated, transdisciplinary approaches to river basin management limited consideration of the watershed’s geomorphological and hydrological dynamics. This challenge is especially pronounced in areas with frequent torrential rain, where urban development has encroached on critical floodplain areas, further worsening flood risks.
Protecting Coastal Communities from a Range of Coastal Risks
Although the disaster that took place in Valencia was due to extreme thunderstorms and rainfall, we know coastal communities face a combination of threats from climate breakdown. The coastal flood hazards of sea temperature and level rise (due to ice melting), thermal expansion of the ocean, and, in some regions, coastal subsidence are also increasing extreme sea levels. This trend is not yet perceived by many because sea levels are rising by approximately 4mm/year globally. Yet, scientists know that we are locked into centuries of sea-level rise and are already seeing the effects in Europe. The historically 1-in-100-year coastal floods are projected to increase by x10 before 2050 in many locations along the Mediterranean and Atlantic coasts and along almost all remaining European coasts by the end of the century, under a low emissions scenario.
Unlike heavy rainfall, which will stop increasing when climate warming has stabilized, sea-level rise will continue for centuries due to the slow response of the ocean and ice sheets to contemporary climate warming. That’s why we need to simultaneously mitigate climate breakdown through global decarbonisation and nature-based solutions while introducing effective adaptation strategies to protect the most vulnerable communities and regions. What’s more, higher sea levels and heavy precipitation resulting in large run-off volumes can cause compound flooding in low-lying coastal areas, as was the case in the catastrophic floods in Venice in November 2019.
CoCliCo is a research project that aims at providing information on where is most at threat from sea-level rise and what the most cost-effective measures are to implement and hopefully prevent such destruction, such as flood defences, room for the river, and even retreating from the highest-risk zones. Importantly, the scale of adaptation needed in coastal areas offers an opportunity to leave more space for sediments and ecosystems and contribute to limiting coastal biodiversity losses, an issue of concern whose implications are still largely underestimated and receive little media attention (Machi-Felici, 2024).
The Need for Long-Term Vision
The loss in Valencia highlights a critical need for prioritizing coastal resilience, particularly as urbanization in vulnerable areas grows. For centuries, dating back to Roman times, these floodplain areas have remained largely unprotected, with development steadily encroaching on these fragile, flood-prone landscapes. Governments and local authorities now have the challenge of defining adaptation strategies that protect people and at-risk infrastructure and anticipate future disasters and responses, such as coastal nature-based solutions and grey infrastructure (e.g., dikes) while leaving opportunities for coastal ecosystems and using limited adaptation funding wisely.
The DANA volunteer groups were primarily made up of citizens from across the country who came on their own to assist those suffering in this critical situation. The experience in this region demonstrated that the most powerful response came from ordinary people, driven by compassion and solidarity, especially in the absence of a coordinated effort from higher-level authorities. At COP29, leaders must advance on climate finance and demonstrate commitment to meaningful adaptation and mitigation to prevent the worst of climate breakdown.CoCliCo supports evidence-based planning to aid communities and decision-makers in preparing for rising coastal risks in Europe. But these investments are just a starting point; a full response requires a long-term vision and policy alignment with the scale of climate challenges we face.
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* The return period is a way to describe how likely an event (like a flood or storm) is to happen over time. It’s usually measured in years and tells us, on average, how often we might expect a certain event to be exceeded.
- A 500-year return period flood has a 1-in-500 chance (or 0.2%) of occurring in any year.
- A 100-year return period flood means that, on average, there’s a 1-in-100 chance (or 1%) of a flood of that size happening in any given year. Within any given 100-year period, however, there is a 66% chance that it will be exceeded.
