The impact of the climate crisis on intense precipitation and Mediterranean floods

Pere Quintana Seguí

Ebro Observatory (URL - CSIC)

Index

• 1 The impact of the 2024 DANA
• 2 The analytical framework of risk
• 3 Hazard
• 4 Vulnerability
• 5 Exposure
• 6 Conclusions
• Authorship notes
• Bibliography

1 The impact of the 2024 DANA

What is a DANA?

• DANA: Isolated Depression at High Levels (Cut-off Low). A closed low-pressure system in the high troposphere that forms when a ripple in the polar jet stream detaches from the general west-east circulation.

• Vertical instability: This large isolated pocket encloses very cold air at high altitude. When situated over the warm and extremely humid air of the Mediterranean, it generates severe vertical instability that triggers deep convection processes and storm formation.
• The danger of blocking: Being decoupled from the main wind flow, DANAs have erratic movement and can remain blocked.
• Orographic forcing: In the Iberian Mediterranean, easterly winds push humid air toward the coastal orography, incessantly feeding the storm over the same basins.

Outline: To understand the trigger of this catastrophe, we must understand what a DANA is physically, what we used to call a “gota fría” (cold drop). It is not a hurricane or a simple storm. It is an immense pocket of polar air that has “fallen” or detached from the jet stream that circulates at higher latitudes, and remains floating over us. By having very cold air above and a very hot and humid Mediterranean Sea below, the atmosphere becomes tremendously unstable. It’s like putting a frozen lid on a pressure cooker about to boil: the system seeks balance by creating gigantic storms from the surface to the high troposphere. But the great problem with the DANA is its lack of movement. Being isolated from the great river of winds that would drag it to the east, it gets stuck. Reports tell us that the Valencia one suffered an almost total block for about 7 days. And if we add to this that the Levante wind pushed all that moisture against our mountain ranges, the result is that the DANA acted like a hose at maximum pressure that got jammed, discharging over the same valleys and ravines for hours.

DANA 10/29/2024

• Quasi-stationary DANA: DANA stalled over the southern peninsula (Gulf of Cádiz), blocked for days.
• Thermodynamic fuel: An abnormally warm Mediterranean injected record levels of instability and water vapor (Agosta-Scarel et al. 2025).
• Persistence and organization: Mesoscale convective systems stalled for hours over the same basins (AEMET 2024).
• Climate attribution: Global warming increased rainfall intensity by ~20% and expanded the area of extreme impact by more than 50% (Calvo-Sancho et al. 2025; Barriopedro et al. 2025).
• Orography: Coastal mountain ranges acted as continuous mechanical forcing, elevating the humid air mass incessantly.

Analysis of the ECMWF HRES model from October 29 at 00 UTC. (a) Geopotential height (2 dam interval) and wind at 700 hPa and thickness of the 850-925 hPa layer (2 dam interval); (b) mean sea level pressure (2 hPa interval), wind at 10 m and thickness of the 850-925 hPa layer (AME)

Outline: Visual and synoptic context introduction of the DANA at the end of October 2024. Briefly explain what atmospheric pattern caused it and why the storm system stalled for so many hours over the same area. As we have seen, the event was exceptional due to the combination of factors. We had a DANA that remained blocked. But the key to its extreme virulence was the fuel: recent studies confirm that a Mediterranean with record temperatures beat historical maximums of moisture and available energy, to which was added a tropical atmospheric river. All this energy did not fall at once in a disorderly way. The orography forced the air to rise and it organized into what AEMET calls “convective trains”: huge storms that are born and discharge water one after another, exactly over the same area, for hours (the hose effect). Finally, the most recent attribution studies already indicate that climate change acted like a steroid in this event. With a warmer atmosphere capable of retaining more water, rainfall intensity increased by around 20% and the total area punished by the downpour was more than 50% larger than it would have been in a pre-industrial climate.

Pluviometric data (daily)

Official data

• Turís: 771.8 mm (Absolute national historical record) (AEMET 2024; Calvo-Sancho et al. 2025).
• Chiva: ~500 mm in a few hours (Castro-Melgar et al. 2025).
• Utiel: 243 mm (AEMET 2024).
• Operational limitation: Official public data usually have a resolution of 1 h and are not always available in real-time during critical situations (Rombeek et al. 2025).

Accumulated precipitation in 24 h on 10/29/2024 (source: AEMET)

Outline: It is vital that we differentiate the magnitude of the event from how we measure it. On one hand, official AEMET data certify the thermodynamic absurdity we faced: almost 772 liters in Turís, the absolute record for Spain in official stations. But operationally, I want to highlight the fundamental role of citizen science and amateur networks (such as AVAMET or Netatmo stations). A recent study shows that these citizen networks are about 7 times denser than the official network. In addition, they offer data every 5 minutes and in real-time, while the official network sometimes reports every hour. During the DANA, these “citizen sensors” allowed seeing exactly where the storm was discharging in the headwaters (such as in the Magro or Poyo) long before the wall of water went down toward the coastal municipalities. The future of early warning and nowcasting involves integrating these networks into emergency centers.

Citizen data

Anticipation (Citizen Science and PWS)

• Density: The network of personal weather stations (PWS) and networks like AVAMET are ~7 times denser than the official network in Valencia (Rombeek et al. 2025).
• Real-time: They provide accessible data every 5 minutes.
• Tactical advantage: This hyper-density allowed monitoring storm dynamics and detecting extreme intensity peaks in the headwaters hours before the flood reached southern municipalities (Rombeek et al. 2025).
• Precision: Possible deficiencies in network maintenance are compensated by the density and speed of data publication.

Observation networks in the Valencian Community (Rombeek et al. 2025)

Record intensity (hourly data)

Hourly precipitation band in Turís Castellón Diario

• Hourly intensity: Turís recorded 185 mm in 1 hour (AEMET 2024).

Table 1: Outstanding pluviometric records (10/29/2024)

Duration	Turís (AEMET)	Previous record
1 hour	184.6 mm
6 hours	620.7 mm	312.0 mm (Málaga, 2018)
24 hours	771.8 mm	817 mm (Oliva, 1987)

• Drainage capacity: These precipitation rates exceed any urban infrastructure design or natural infiltration capacity.

Outline: The objective is to emphasize the extreme hourly intensity (mm/h), which is what overflows the basins, beyond the total accumulated. Compare with standard torrentiality thresholds to dimension the magnitude of the event.

Lightning hydrological response

Rambla del Poyo

• Gauge sensor collapse: It was destroyed at 19:00 h when it already recorded 1,938 m³/s (Lucia et al. 2026).
• Peak flow: Reconstruction using hydrological models (HEC-HMS/RAS) estimates a peak of about 2,900 m³/s at the station, reaching ~4,750 m³/s downstream (Lucia et al. 2026).
• Comparison: This flow in an ephemeral ravine exceeds the historical record of the Ebro River in Zaragoza (~4,130 m³/s in 1961).

Magre River: The “Perfect Storm”

• Extreme synchrony: The peak of a second storm moved downstream coinciding exactly in time with the transit of the first flood wave generated in the morning (Rombeek et al. 2025).
• An exceptional event: This overlap resulted in a mean precipitation over the basin with an estimated return period exceeding 10,000 years (Rombeek et al. 2025) (although these return periods are always very uncertain).

Human, material impact and infrastructure collapse

• Fatalities: More than 230 deceased persons (224 confirmed in the province of Valencia), the deadliest flood in all of Europe since 1985 (Barriopedro et al. 2025; Galvez-Hernandez et al. 2025).
• Economic impact: the costliest disaster in the history of Spain (Barriopedro et al. 2025). Destruction of capital stock estimated at more than 17,000 million euros according to IVIE, concentrated mostly in industry, services, and agriculture (Pérez et al. 2025; Barriopedro et al. 2025).
• Vehicle chaos: More than 141,000 vehicles disabled or swept away, which acted as extreme physical barriers blocking streets and hindering rescues (Olcina and Morote 2025).

• Collapse of critical infrastructure:
  • Transport: Flooding of critical sections of the A-7 and AP-7 highways, and total paralysis of the metropolitan and southern connection rail network (Castro-Melgar et al. 2025).
  • Essential services: Direct impact on 50 educational centers and 7 health/hospital facilities, in addition to massive electricity and telecommunications cuts (Castro-Melgar et al. 2025).

Outline: Visual and qualitative summary of damage. The numbers are chilling. More than 230 fatalities, the vast majority in Valencia, with a large part of them being people over 70 years old. On an economic level, we are talking about more than 17,000 million euros in pure destruction of capital, the greatest economic disaster recorded. A key element for rescues (and that you know well) were the vehicles: more than 141,000 cars swept away blocked access to municipalities. In addition, exposure was so high that water affected about 50 schools and 7 health centers, demonstrating that urban planning had put us in the maximum risk zone.

The terrain scenario for rescue teams

• “Urban trap”: Streets acted as fluvial canyons. Water reached up to 1.8 meters in height in a matter of seconds, trapping thousands of people in vehicles, garages, and ground floors (disproportionately affecting those over 70) (Galvez-Hernandez et al. 2025).
• Debris walls: Massive accumulation of vehicles and compacted mud created impenetrable physical barriers, completely blocking access for emergency and aid convoys to the “ground zero” zones (Castro-Melgar et al. 2025).

• Technological blackout: Massive power cuts and the fall of telecommunications left teams without critical communications and caused the loss of hydrological sensors in the first hours (Castro-Melgar et al. 2025; Lucia et al. 2026).
• Hyper-concentrated flows: “Dirty” water (mud, vehicles, and plant remains) transformed the flood into a hyper-concentrated flow (non-Newtonian behavior), exponentially multiplying its density and destructive force.

Outline: Reflect on the tactical conditions of the rescue. As emergency professionals, you face a war scenario. Streets, designed with impermeable asphalt, become fluvial canyons where water rose almost 2 meters in seconds, trapping the most vulnerable people in their ground floors. To this is added the logistical nightmare: tens of thousands of cars acting as barricades that prevent your trucks from reaching the rescue. All this, blind, without mobile coverage or repeaters, operating in total uncertainty. Finally, water is not just water; it is a “hyper-concentrated flow” loaded with mud and debris, which multiplies its drag and destruction power, smashing doors and walls that clean water would not knock down.

Chronology of public response

gantt
    title The Warning Chain (Oct 29)
    dateFormat  HH:mm
    axisFormat %H:%M
    
    section AEMET
    Red Warning (Coast)      :crit, 07:36, 12h
    Red Warning (Inland)     :crit, 09:41, 10h
    
    section Hydrology (CHJ)
    Poyo sensor collapse     :active, 19:00, 1h
    
    section Civil Protection
    ES-Alert message to mobiles :milestone, 20:11, 1min

Figure 1

• The 12-hour gap: Lethal lag between the declaration of extreme danger by AEMET (07:36 h) and the mass alert to the population (20:11 h) (Galvez-Hernandez et al. 2025).
• False sense of security: Institutional statements at 13:00 h stating that the storm would subside kept the population leading a normal life (working, moving) (Martin-Moreno et al. 2025).
• Preventive contrast: Institutions such as the University of Valencia cancelled all their activity the day before based on the same meteorological data (Martin-Moreno et al. 2025).
• Impact on rescue: The lack of prevention forced firefighters to intervene in a scenario of maximum citizen exposure, instead of a pre-evacuated area.

Outline: The key message is the 12-hour gap. At 7:36 AM there was already an official red warning, but the mass SMS arrived at 20:11, when most of the metropolitan area was already under water. Analyze the importance of operational anticipation in firefighters.

Why has it been so devastating?

• A dangerous event:
  • Thermodynamics: An abnormally warm Mediterranean injected between 15% and 20% extra moisture, increasing the hourly rain rate by 20% (Agosta-Scarel et al. 2025; Campos, Grayson, Saurral, Beyer, et al. 2025; Calvo-Sancho et al. 2025).
  • Persistence: An atmospheric blocking pattern and a tropical Atmospheric River sustained the stationary storm (Campos, Grayson, Saurral, Beyer, et al. 2025).

• A vulnerable society:
  • Social vulnerability: Massive failure in risk perception. The population did not know how to translate the technical warning into self-protection (e.g. going down to the garage to save the car was lethal) (Amengual et al. 2024; Galvez-Hernandez et al. 2025).
  • Institutional vulnerability: Critical gap of 12 hours between the meteorological red warning (AEMET) and the mass alert to mobiles (Galvez-Hernandez et al. 2025; Martin-Moreno et al. 2025).

• Exposure: Massive occupation (30% of homes in risk zones) and an impact area of 199 km² flooded (Olcina and Morote 2025; Castro-Melgar et al. 2025).

Outline: Scientific synthesis. This is the summary slide. Why has it been so devastating? Because all the worst possible factors of the risk equation aligned. 1. Thermodynamics: The current climate injected up to 20% more water into the atmosphere. 2. Persistence: A block and an “atmospheric river” injected continuous moisture like a conveyor belt. 3. Social Vulnerability: Total lack of risk culture. People tried to save cars in garages that flooded in seconds. 4. Institutional Vulnerability: Those 12 hours of inaction that allowed the population to be exposed to the maximum. 5. Exposure: 199 square kilometers under water and the terrible datum that 3 out of 10 houses affected had been built in floodable zones knowingly. An urban failure.

Was it the DANA or was it urbanism?

• Reckless expansion: Rapid and uncontrolled urban expansion toward alluvial plains and floodable peri-urban zones exponentially multiplied population and infrastructure at extreme risk (Castro-Melgar et al. 2025; Conesa 2025).
• Bubble legacy: Political and economic decisions prioritized profit over safety. It is estimated that 3 out of 10 homes affected by the DANA in Valencia were built in known risk zones during the real estate boom (1997-2007), disregarding hazard maps (Galvez-Hernandez et al. 2025; Olcina and Morote 2025).

• “Design” vulnerability: Scientific studies agree that the catastrophe was not only meteorological. Uncontrolled urbanism, deforestation, and lack of territorial planning created a death trap, aggravated by deficient institutional decisions (Lucia et al. 2026; Galvez-Hernandez et al. 2025).
• The challenge of reconstruction: Recovery cannot be limited to “rebuilding the same”. The situation demands a profound revision of urban planning based on climate resilience criteria and nature-based solutions, avoiding perpetuating risk (Verdú Martínez 2025).

Outline: We reach the key question: Was it the DANA or was it urbanism? The rain was historical, yes, but science tells us that the human and economic disaster was, to a large extent, caused by ourselves. For decades, especially during the real estate boom, land occupation in the Mediterranean was reckless. It was built on alluvial plains and ravines ignoring risk maps because fast economic profit prevailed. The data is chilling: 30% of the houses that flooded in Valencia had been built in flood zones already cataloged. This is what recent articles call “systemic vulnerability”: the water sought its natural course, but encountered entire cities. Therefore, the message for the future, as land use planning experts warn, is that we cannot simply clean the mud and rebuild exactly the same. We must assume that those areas belong to the river, and our urban planning must adapt to the new climate reality, not the other way around.

2 The analytical framework of risk

Dismantling the myth of “natural disasters”

• There are no natural disasters: Floods are a natural threat (a physical phenomenon), but not a natural disaster. The disaster is a social construction that depends on our exposure and our vulnerability (Llasat 2021; Kelman 2020).
• Catastrophe vs. Disaster: The catastrophe is the extreme rain, but the disaster is the resulting human and economic impact when colliding with a vulnerable and poorly planned territory (Rodríguez Salgado 2025).
• The human factor and the “levee effect”: The Valencia disaster evidences how uncontrolled urbanization and the false sense of security of infrastructure have triggered the population’s exposure to risk (Llasat et al. 2024; Olcina and Morote 2025).

Disaster by Choice, Ilan Kelman

Understanding the risk equation will allow us to understand why disasters are not “natural” and where we can act to reduce their impact.

Outline: Explain that nature is not “cruel”. As Dr. Llasat (world reference in Mediterranean floods) points out, torrential rain is a natural phenomenon, but the disaster is not. The Valencia disaster is the result of decades of human decisions on the territory. Llasat warns in her recent Nature article of the “levee effect”: we make a cement canal, we believe we are safe and we build thousands of houses in flood zones. If we remove that vulnerability and that exposure, we have a historical flood, but we don’t have a “disaster” with more than 200 victims.

The risk equation: R = H * V * E

Outline: Define each term: Hazard (rain), Vulnerability (preparedness), and Exposure (territory).

Which variables do we control?

• ⛔ Hazard: Uncontrollable variable. In our case they are extreme precipitation, which have become more intense and unpredictable due to climate change. We cannot stop the rain, but we can prepare for it.
• ✅ Exposure (Urbanism): Controllable variable in the medium term. It is a political and territorial decision: restrict new construction in risk zones, reverse urban planning nonsense, and return space to the “fluvial territory” (Castro-Melgar et al. 2025; Olcina and Morote 2025).

• ✅ Vulnerability (Culture/Preparedness): Highly controllable and immediate variable. It depends on citizen education and the effectiveness of alerts. Knowing what to do saves lives (e.g. not going down to garages) (Llasat-Botija et al. 2025; Martin-Moreno et al. 2025).

Conclusion: We cannot stop extreme rain, but through prevention, planning, and education, we can prevent it from becoming a catastrophe.

Outline: Reflection on where we can act as a society. Hazard (climate) is very difficult to reverse in the short term; the sea will continue to be hot and storms will be violent. However, exposure and vulnerability are pure human decisions. We can decide not to build more in floodable zones (exposure). And, above all, we can act today on vulnerability: educate people to understand that going down to save the car in the garage is a death trap, and design community alert systems that arrive on time. You, as rescuers, are the last link in the chain. Your work becomes a nightmare exactly when society fails in the control of its exposure and its vulnerability.

3 Hazard

Milestones of floodability in Catalonia

Year	Zone	Type	Operational lesson and critical factor
1940	Eastern Pyrenees	Extreme rain	Persistence: Up to 743 mm in 72 h. 90 victims (Amengual 2025).
1962	Vallés	Urban flash flood	Vulnerability: The greatest disaster of the 20th century (815 victims). Lethal danger of building in the riverbed (Rubí) (Amengual 2025).
1982	Pyrenees and Segre	Regional storm	Regional magnitude: Transboundary overflow. Impelled modern emergency plans (Llasat et al. 2024).
2019	Francolí	Sudden flood	“Dam Effect”: 20,000 trees clogged bridges. Their collapse generated lethal waves (6 victims) (Amengual et al. 2024).
2020	Litoral (Gloria)	Systemic storm	Compound events: Extreme maritime storm prevented natural river drainage.

• Floods in Catalonia are not new. History is full of extreme events that have taught us key operational lessons. The challenge is to put these learnings into practice so as not to repeat the same mistakes.

Outline: This table is a tactical summary of what you face. Each great disaster has taught us a different operational lesson. In ’62 we learned what happens when people live inside the stream: extreme urban vulnerability with 815 deaths. In ’82 we saw that a flood can collapse all of the Pyrenees at once, forcing the modernization of Civil Protection. But look at the Francolí of 2019: the great lesson for rescues is the “Dam Effect”. The river acted like an excavator uprooting 20,000 trees. Those logs clogged the bridges and, upon giving way, released a wall of water that killed 6 people. Water is dangerous, but the debris it drags makes it lethal.

History of floods in Catalonia

• An intrinsic threat: Flash floods are consubstantial to our geography due to short rivers, steep slopes, and proximity to the Mediterranean Sea.
• Historical memory: GAMA group studies conclude that the increase in disasters is directly linked to human occupation of floodable zones, rather than purely climatic anomalies of the past (Llasat et al. 2005; Llasat et al. 2016).
• The great lesson: Recurrence is the norm. Floods have always existed, but today, reckless occupation of the territory collides with an increasingly extreme and warm atmosphere (Blöschl et al. 2020).

Flood events in Catalonia (1981-2010) (Llasat et al. 2016)

Outline: To understand what happened in Valencia, we must first look at our own history. We have data since the 14th century that demonstrate that in the Mediterranean it has always rained like crazy [1]. Recurrence is the norm. However, studies show that the increase in recent disasters is not only because it rains harder, but because we have occupied the floodplains massively [2].

Milestones of floodability in the Valencian Community

Year	Zone	Type	Operational lesson and critical factor
1957	Valencia (Túria)	Fluvial flood	Urban redesign: The flooding of the historic center forced the “Plan Sur”. It showed that the structural solution (diversion of the riverbed) protected the city, but shifted the risk and false sense of security toward the south (Galvez-Hernandez et al. 2025; Conesa 2025).
1982	Ribera del Xúquer	Pantanada (Tous)	Dam safety: The collapse of the Tous dam was a turning point. It drove the creation of the sensor system (SAIH) and the modernization of risk management in Spain (Amengual 2025).
1987	La Safor and the Marina	Extreme rain	Persistence and intensity: The record of 817 mm in 24 h in Oliva evidenced the ability of stationary DANAs to saturate any drainage system in the Mediterranean arc (Amengual 2025).
2019	Baix Segura	Regional DANA	Plain vulnerability: Flooding by overflow in zones with almost zero slope. The collapse paralyzed the economy of an entire region and forced a rethink of territorial resilience (Conesa 2025).
2024	L’Horta Sud and Ribera	Flash flood (Ravines)	“Last mile” management: Explosive response of ravines (Poyo) and communication collapse. It highlighted the ineffectiveness of warnings in basins with very fast response (concentration time < 2h) (Lucia et al. 2026).

• In the same way, in the Valencian community, high-impact floods are not a novelty.
• The question is, how could the 2024 event be so devastating if we already had a history of extreme events that had taught us key lessons?

Outline: This table summarizes our evolution and our mistakes. In 1957, the Túria flood forced the creation of the Plan Sur. They saved the center of Valencia, yes, but as studies warn, we diverted the risk toward the southern municipalities (L’Horta Sud) creating a false sense of security that we have paid for now. In ’82, the collapse of Tous taught us the criticality of large infrastructures and drove the technological modernization and SAIH sensors. In ’87 we discovered the limit of intensity with those 817 liters in Oliva. In 2019 we saw how very flat areas like the Baix Segura create floods that paralyze entire regions for weeks. But the great operational failure and the great lesson comes in 2024. What I call the “last mile management”. A ravine like Poyo rises almost 2 meters in minutes. In basins with such fast response, the official warning system collapsed and the alert arrived when people were already drowning.

Climate change

• Definition: Long-term alteration of temperatures and global climate patterns, driven by the accumulation of Greenhouse Gases (GHG) of anthropogenic origin.
• Irrefutable evidence:
  • CO₂ concentration: We exceed 420 ppm, levels not seen in the last 3 million years.
  • Global warming: Increase of ~1.2 °C relative to the pre-industrial era (IPCC AR6).
  • Thermal records: The last decade has been the warmest historically recorded.
• The Mediterranean: Warms 25% faster than the global average (Cramer et al. 2018).
• Scientific consensus: Unequivocally caused by human activity (burning of fossil fuels, changes in land use and plant cover, etc.).

IPCC AR6

Outline: Explain simply that climate change is not a natural cyclic process on the human scale, but a thermal acceleration caused by our emissions. Highlight that for us (firefighters) it is not a theory, but a change in the frequency and virulence of emergency services.

Temperature trends (local)

Ebro Observatory (1880-2022): - Mean Temperature: Significant increase of +0.21 ºC/decade. - Maximum Temperatures: The most extreme indicator, with a rise of +0.32 ºC/decade. - Minimum Temperatures: Increase of +0.11 ºC/decade. - Heat days (T > 30ºC): Drastic increment of +6.1 days/decade.

🔴 There is no doubt that local temperature increases significantly and with more marked trends than global averages.

Thermal trends in Roquetes (1880-2022)

Outline: Present the results of the analysis of the historical temperature series of the Ebro Observatory. Highlight that warming is unequivocal and that maximums rise almost half a degree per decade, which feeds evaporation and energy available for extreme events.

The thermodynamics of intense precipitation

• The Mediterranean as a “battery”: Global warming accumulates thermal energy in the sea.
  • Reaching autumn with record temperatures (e.g. 28-29 °C) injects massive amounts of heat and moisture into the lower atmosphere (Agosta-Scarel et al. 2025).
• The 7% rule (Clausius-Clapeyron): Basic physics dictates that for every 1 °C of warming, the air can retain ~7% more water vapor (Calvo-Sancho et al. 2025; Campos, Grayson, Saurral, Olmo, et al. 2025).

• Explosive torrentiality: This massive overload of “fuel” (moisture) and energy makes precipitation much more violent in very short periods (mm/h) (Llasat et al. 2021; Calvo-Sancho et al. 2025).
• The role of the DANA: The appearance of a DANA generates atmospheric instability that “squeezes” that moisture in the form of torrential rain, exceeding any natural or artificial drainage capacity.

Outline: If we compare the atmosphere to an engine, the Mediterranean at 29 degrees at the end of summer is our particular gas station. As the sea warms, it injects more heat into the system. And here comes a fundamental physical law, the Clausius-Clapeyron relationship: for every degree the temperature rises, the atmosphere “sucks up” and retains 7% more water vapor. In other words, we are putting extra fuel into the engine. When the cold air of a DANA arrives and “squeezes” that cloud over a small basin, that extra percentage of water that falls at once in just an hour or two is exactly what marks the red line between an overflow that emergency teams can manage, and an inland “tsunami” that destroys infrastructure.

Dynamics also change

• Not only does climate change influence thermodynamics, it also affects atmospheric dynamics.

Sources: Francis and Vavrus (2015); Agosta-Scarel et al. (2025); Lorente-Plazas et al. (2020); Mishra et al. (2025);Barriopedro et al. (2025); Calvo-Sancho et al. (2025).

Observed precipitation trends

• High annual variability: Historical records since the end of the 19th century do not show a significant and generalized drop in total annual precipitation on the Mediterranean side, but a very high natural interannual and multidecadal variability (Vicente-Serrano et al. 2025).
• More rainy days (weak): Contrary to popular belief, exhaustive studies show that the total number of rainy days (especially weak precipitation) is increasing in much of the Iberian Peninsula in all seasons of the year (Gallego et al. 2011).

• The 24-hour mirage: Maximum rain indices at a daily scale barely show upward trends. The danger is masked because the 24-hour rain gauge records the total amount, but does not reflect the speed at which water falls (Llasat et al. 2016).
• The key is the sub-daily scale (Convection): The true increase in danger occurs in short-duration convective rain. Although daily totals do not rise, intensity rates in fractions of an hour or minutes are increasing drastically, triggering the risk of flash floods (Llasat 2021; Requena et al. 2023).

Outline: We have to debunk a very common myth. Neither does it rain less annually at a historical level, nor do we have fewer rainy days. A study publishing this very 2025 in the journal Climate Dynamics shows that the annual total has been stable for a century and a half, dominated by brutal variability. And in fact, data prove that the number of days it rains is increasing. So why do we have increasingly worse floods? Because of the “trap” of the daily datum. A 24-hour rain gauge doesn’t care if 100 liters fall throughout an entire day or in 45 minutes. The daily statistical datum does not rise, but the disaster does. Science shows us that what is increasing critically is convective precipitation (the sub-daily or hourly scale). Water falls in a much more explosive way in less time. For you, at an operational level, this is vital: you don’t face longer storms, you face “flash floods” where reaction times are reduced to minutes.

Observed precipitation trends

Trends observed at the Ebro Observatory (1880-2022) at a daily scale:

• Fewer rainy days (≥1mm): Decrease of -1 day/decade (1948-2022 period), on the limit of statistical significance (p=0.06).
• More intensity (SDII): Robust and significant increase in mean intensity per rain day (+0.15 mm/day per decade in the long series 1905-2022, p<0.05).
• Extremes (Max 24h): Positive signal in the last 25 years (+8.4 mm/decade, 1998-2022), although high variability hides statistical significance (p=0.29).

Conclusion: It rains fewer times, but when it does, the atmosphere discharges more intensely. But it must be emphasized that the changes are not very evident at a daily scale.

Outline: Local data from the Ebro Observatory. Explain that although total rain does not vary much, the structure of precipitation does. For firefighters, this means floods can be more sudden and violent even in a context of fewer total rainy days.

Intensity and frequency trends

Intensity (SDII)

Rainy days (≥1mm)

• Real climate signal: The black dots indicate the periods of significant trend.
• Double signal: The increase in intensity (blue) and the decrease in frequency (red) are significant since the beginning of the 20th century.

Outline: Explain what the sensitivity triangle is. The message for the public is that we are not “choosing” the dates for the result to come out, but that it is a real and stable physical change in our territory. Blue = more/more intense, Red = less/less intense.

Observed precipitation trends

Maximum intensity (hourly) at the Ebro Observatory (time scale of flash floods):

• Historical series (1957-2022): Signal marked by extremely high interannual variability.
• Recent trend (50 years): Increment of +1.7 mm/h per decade (since 1973).
• Signal last stage (30 years): Increment of +2.3 mm/h per decade (1993-2022).
• Significance: High variability hides statistical significance (p > 0.10), but the physical signal of increase in the era of accelerated warming is persistent.

Annual maximum precipitation series in 60 min

Outline: Explain that the hourly scale is the truly critical one for aquatic rescue. Although in long 100-year series we don’t see a clear trend, if we look at the last 25-30 years (the era of accelerated warming), the intensity of the strongest showers is rising almost 5 mm/h every decade. This drastically reduces the response time.

Future projections

(Cramer et al. 2018)

The Mediterranean is heading toward a scenario of interconnected and compound risks.

• Torrentiality projections:

  • Under high emissions scenarios, the magnitude of extreme events could increase up to 100% in 50 years (Zittis et al. 2021).

  • Rainfall rates in fractions of 1 to 6 hours increase drastically compared to daily averages (Requena et al. 2023; Calvo-Sancho et al. 2025).

• Droughts and floods are related: The increase in prolonged droughts degrades natural defenses and plant cover (forests), drastically reducing soil infiltration capacity (Cramer et al. 2018).

Outline: Where are we going according to climate models? Toward a radical alternation that scientists call “interconnected risks”. First, we will suffer more extreme droughts. This means that when the storm finally arrives, it hits a parched soil, without plant cover, which acts almost like asphalt. Water does not infiltrate, it runs directly toward the streams carrying the soil (erosion). And regarding projections, the rule is clear: the shorter the storm, the greater the impact of climate change. High-resolution models such as those used by Zittis (2021) project that the rarest and most destructive episodes can multiply their intensity up to 100%. For you, at an operational level, this means that the response times of basins and ravines will continue to shorten. The window of opportunity to save a life before the wall of water goes down will be increasingly small.

Droughts and floods

Droughts and floods are interrelated and can even occur at the same time.

• Dry Mediterranean soils have a great capacity for storage and initial infiltration: low usual runoff coefficients.

• But if precipitation exceeds infiltration capacity, the flood is triggered abruptly.
• The vicious circle: Prolonged droughts dry out vegetation, compact the soil and increase the risk of fires. This creates “hydrophobic” terrain (which repels water) and without natural barriers, which multiplies runoff speed, erosion and the destructive force of the flood (Granata et al. 2025; Cramer et al. 2018).
• Integrated management: Droughts and floods cannot be managed in isolation (Ward et al. 2020).

Outline: In the Mediterranean, drought and flood are the two faces of the same monster. We often think: “since we’ve been months without rain and the soil is very dry, the earth will drink all the water”. It is true that dry terrain has a “sponge” effect at first, but hydrological science is very clear: when we face extreme rain like that of a DANA, this infiltration capacity collapses completely. Water falls with such violence that it saturates the surface layer and slips. In fact, prolonged droughts create a lethal vicious circle. Heat and lack of water kill vegetation, compact the earth and favor large fires. When it finally rains like crazy over that hydrophobic soil without roots, water runs as if falling on asphalt, dragging mud and increasing the destructive capacity of the flood. Operationally, this means that after a severe drought or a fire, an intense storm is exponentially more dangerous.

Uncertainties and limits of climate predictions

• Despite uncertainties, the thermodynamics of climate change is very clear and we must prepare for a future with more droughts and more torrential precipitation.

• Current climate models systematically underestimate the intensity of short-duration convective storms, which implies that projections could be conservative compared to future reality (Llasat 2021; Calvo-Sancho et al. 2025).

• Precautionary principle: In territorial planning and infrastructure design, climate scenarios should not be taken as an absolute maximum limit. We must assume much larger safety margins against the new torrentiality.

Outline: If before we were talking about weather prediction, now let’s talk about long-term climate. How do we prepare our risk maps and our infrastructures for the next decades? Science gives us a clear warning: be careful with blindly trusting climate models. Global and regional climate models have a “blind spot”: resolution. They cannot simulate the typical Mediterranean convective storms well. This makes them systematically underestimate the amount of water that is going to fall in extreme and short episodes. In addition, there is a lot of dispersion. If we take 30 different models for the Mediterranean, predictions vary enormously among them. But what there is consensus on is that historical statistics no longer serve. A recent study with EURO-CORDEX models shows that if we design a bridge or a flood map to withstand a “100-year flood” based on data from the 20th century, we will be staying up to 30% short compared to what the 21st century is going to bring us. Therefore, the message for reconstruction and planning is the precautionary principle. What used to be a 100-year event will now happen much more often and with more violence. We cannot rebuild adjusting to the limit; we must oversize safety.

Prediction of extreme events

• Meteorological models predict synoptic conditions well, but have great difficulty accurately predicting the location, intensity and exact moment of a local convective storm (Amengual et al. 2024; Flaounas et al. 2022).
• Probabilistic scenarios: Operationally, we must move toward Ensemble Prediction Systems (Ensembles or EPS) of very high resolution (convection-permitting) (Amengual et al. 2024; Amengual 2025).

Image of the AEMET weather radar at 16:00 on 10/29/2024

• Nowcasting: Given that reaction time against a flash flood is minimal, survival depends on nowcasting (0-3 hour prediction). This requires aggressive real-time monitoring (Price et al. 2011).

• New warning networks: Integration of radars, lightning detection networks and citizen stations is critical to anticipate the flood before it wipes out municipalities (Price et al. 2011; Rombeek et al. 2025).

• Better not to need predictions: A society with low vulnerability and exposure will not depend so much on meteorological prediction.

Outline: We move now to operational meteorology. Where are we regarding prediction? Science tells us that, today, it is almost impossible to hit the exact point hours in advance. Mediterranean convective storms that cause flash floods have very low predictability, especially if they form over the sea. That’s why the first message is: forget the deterministic prediction of “it’s going to rain exactly here and this amount”. We must work with probabilistic predictions (EPS). Models will give us a range of scenarios, and Civil Protection must dimension the alert thinking about the extremes of that probability. As medium-term models have uncertainty in the exact “where”, our truly tactical weapon is “nowcasting”: minute-by-minute monitoring. When the storm explodes, the warning time is drastically reduced. This is where radars, lightning detection (which warn of cloud violence) and citizen networks save lives. These private stations give us data every 5 minutes and have a much higher density than the official network. That advantage is what allows launching a warning to the population before the wall of water goes down the ravine.

4 Vulnerability

Vulnerability

• Multidimensional concept: Pre-existing conditions (social, economic, political and demographic) that increase the susceptibility of a community to suffer damage from the same amount of rain (Cutter et al. 2003; Kreibich et al. 2022).
• Socio-demographic vulnerability: Mortality risk skyrockets in specific groups: elderly people (due to less mobility), population in ground floors, and tourists or foreign residents (due to ignorance) (Galvez-Hernandez et al. 2025; Llasat et al. 2008).
• The erosion of historical memory: Forgetting past floods deactivates spontaneous self-protection mechanisms (Llasat 2021; Amengual et al. 2024).

• Economic vulnerability: Municipalities and neighborhoods with lower incomes suffer worse impacts, have less prepared homes and face greater barriers to access insurance or recovery aid (Olcina and Morote 2025; Rodríguez Salgado 2025).
• Institutional vulnerability: It manifests when early warning systems fail or are delayed, when urban planning ignores risk maps due to economic pressures, or when there is lack of coordination between administrations (Galvez-Hernandez et al. 2025; Martin-Moreno et al. 2025).
• “Infodemic”: Disinformation and hoaxes on social networks can hinder the actual work of emergency teams on the ground (López-Carrión and Llorca-Abad 2025; Alcantara 2025; Torres et al. 2025).

Outline: If hazard (rain) is the trigger, vulnerability is the gunpowder. Two cities can receive exactly the same liters per square meter, but the number of victims will be radically different depending on their vulnerability. Science teaches us that vulnerability has several faces. There is the demographic face: in recent disasters such as the DANA, more than half of the deceased were over 70 years old trapped in ground floors [1, 2]. We also see high mortality in tourists or foreigners who, out of pure ignorance of the Mediterranean climate, try to cross flooded streams [3]. There is the economic face: working-class neighborhoods and areas with lower incomes are usually located in the topographically most dangerous areas and have much less financial capacity to recover from the blow [4]. But for us, the managers, the most important is institutional vulnerability. A citizen becomes infinitely more vulnerable if the early warning system (such as the ES-Alert to mobiles) reaches them when the water already covers their knees [5], or if for decades it has been allowed to build their neighborhood in an area that official maps already marked as floodable. Reducing institutional vulnerability saves lives immediately.

Reduction of vulnerability

• Early Warning Systems (EWS): that are understandable and reach the population in time.
• Education and community resilience: Citizen strategies for mutual support and self-management. (Rodríguez Salgado 2025; Olcina and Morote 2025).
• Governance and institutional adaptation: Institutions must have the capacity to integrate lessons from the past (coordination, laws, codes, prevention, etc.) (Galvez-Hernandez et al. 2025; Verdú Martínez 2025; Kreibich et al. 2022).
• Land use planning and resilient urbanism: We must move toward compact urban models and “sponge cities”, to retain water (Verdú Martínez 2025; Moragues et al. 2025).

• Increase the use of nature-based solutions: Gray infrastructures can generate false security. We must restore floodplains and wetlands to buffer natural impact and reduce flood peaks, without ceasing to use gray infrastructures occasionally, when necessary.

Outline: We have already seen that we cannot turn off the rain (the danger), but we can drastically reduce our vulnerability. Scientific literature marks a clear path for us that combines technical and social solutions. In the first place, people must be taken out of the path of water through strict land use planning and adapt our cities toward permeable models that absorb the blow. In the second place, we need Early Warning Systems with a “first mile” approach. That the notice reaches the mobile hours before, and that the population has participated in the design of the protocols to know exactly what to do. Third, Nature-Based Solutions: giving space back to the river (the fluvial territory) so that it overflows safely before reaching the city. Finally, the great lesson of disasters like the DANA is the power of the community (bottom-up approach). Networks of organized neighbors are the engine of resilience. And here you, the firefighters, have a fundamental role: not only in the rescue, but being the teachers of that “risk culture” that is missing in society. For this to work, we need an institutional governance that bets on education and on rebuilding the territory under the principles of the Urban Agenda, without committing the urban mistakes of the past.

New vulnerable citizens and tourists

Photo: Belgian vehicle trying to cross a ravine in l’Ametlla de Mar. Pere Quintana Seguí

• Vulnerability by mislocation: The lack of mental maps of the territory prevents identifying safe zones instinctively.
• Ignorance of local codes: Incapacity to interpret natural signals (e.g. rising level of a stream even if it doesn’t rain locally) or specific sound/visual warnings.
• False perception of security: The tourist usually underestimates the speed and force of a Mediterranean flash flood when comparing it with the fluvial dynamics of their home countries.

Outline: It’s not just that there are “more people”, it’s that the floating population and new residents lack the historical memory we were talking about. A Belgian or German tourist, accustomed to rivers that rise slowly for days, cannot conceive that a dry ravine becomes a 2-meter wall of water in 15 minutes. That “cognitive mislocation” makes them extremely vulnerable and generates very complex rescue services for you.

The challenge of alert communication

• Understandable alerts: Early Warning Systems (EWS) must be people-centered. To be understandable, the population must participate in their design to ensure the message is understood and generates action.
• Semantic confusion: The population often does not understand the difference between a meteorological alert (rain) and a hydrological one (overflow), nor the meaning of color codes (yellow, orange, red).
• Fast and effective: Technology loses its value if the alert depends on a slow chain of command and subjective aspects. Protocols have to be clear and objective.

• Action-oriented alerts: Alerts must dictate clear, direct and practiced behavioral patterns, especially because in many flash floods water reaches areas where it is not even raining.
• Trust: The population needs to trust alert systems to act correctly when notified of a danger. If too many alerts are issued or the population does not understand the message, alert fatigue or distrust can be generated, which reduces the system’s effectiveness.

Outline: We have the best radar technology and the best models, but they are of no use if we fail in the final link: the human being. Scientific literature talks about changing the approach from the “last mile” to the “first mile”. That is, the alert does not end when Civil Protection presses the ES-Alert button; the system only works if the citizen who receives the SMS knows exactly what to do in that second. And here we have two big problems. The first is institutional: protocols are slow. As we saw in Valencia, if there are political or bureaucratic doubts and the SMS is sent hours late, the system has completely failed. The second is understanding. After the Francolí floods in 2019, surveys showed that more than half of the population did not understand the alert levels by color or the probability warnings. In addition, people look out the window, see that it doesn’t rain much in their street, and decide to go down to take the car out of the garage without knowing that the flood comes from the headwaters. Therefore, the great tactical challenge is that ES-Alert alerts must be instantaneous, automated according to the data, and their messages must be purely behavioral: don’t tell us how many liters are going to fall, tell me not to cross the bridge and to go up to the first floor.

Training and risk culture

• Memory: The lack of recent extreme events erodes risk perception. The population confuses “dry climate” with “safe climate”, deactivating self-protection behaviors (Llasat 2021; Amengual et al. 2024).
• Risk literacy: It is urgent to integrate training in natural risks in the school curriculum and in adult education programs. Understanding a hazard map must be a basic skill (Olcina and Morote 2025).
• Media literacy: Disinformation (hoaxes) during the crisis generates institutional distrust and can induce fatal behaviors. Training must include the ability to verify sources in real-time (Torres et al. 2025).
• Simulations and family and community protocols: Risk culture is built with community practice (Olcina and Morote 2025; Llasat-Botija et al. 2025).

Outline: This is perhaps the most important point to save lives at zero cost. Hazard is physical, exposure is urbanism, but risk culture is education. Olcina (2025) highlights that education is the cheapest and most effective self-protection measure. If people knew that they should not go down to the garage with a red alert, we would have avoided dozens of deaths in Valencia. In addition, Sánchez Torres (2025) warns us of the danger of hoaxes: in the midst of chaos, a false rumor can make people make wrong decisions or distrust the evacuation orders of firefighters. We need a population that knows how to distinguish official information from the noise of social networks. For you, the firefighters, a trained population is an ally; a population without risk culture is a burden that multiplies risky rescues.

5 Exposure

Exposure: living in the path of water

• The main driver of risk: The historical increase in flood damage in the Mediterranean is fundamentally due to the increase in exposure and the occupation of the territory, rather than an exclusive increase in extreme rain (Llasat et al. 2005; Amengual 2025).
• The coastal demographic trap: Between 1985 and 2006, the population of the Mediterranean coast grew considerably, locating mostly near torrential courses (Llasat et al. 2014). In Spain, 41.9% of the population is concentrated in just 19% of the Mediterranean national territory (Amengual 2025).

• Uncontrolled urbanism and waterproofing: Urban expansion has occupied floodplains and ravines. The creation of new artificial and impermeable surfaces has eliminated soil absorption capacity, multiplying extraordinary floods (Galvez-Hernandez et al. 2025; Llasat 2021).
• The “Levee Effect” (False security): Structural interventions (channeling, walls) have encouraged massive occupation of floodable zones by reducing the perception of danger. When an extreme event exceeds these defenses, the catastrophe is multiplied due to the very high accumulated exposure (Viglione et al. 2025).

Outline: We return to the risk equation. We have already seen the hazard (rain) and the vulnerability (our fragility). Now it’s time to talk about the “elephant in the room”: Exposure. Exposure responds to a very simple question: How many people and how much economic value have we put in the way of water? Reference researchers such as M.C. Llasat’s team have demonstrated by studying records from the last 700 years that, if we have increasingly destructive disasters, it’s not just because it rains more, it’s above all because there are more and more of us living on the target. There is a real “demographic trap” on the coast. In just 20 years, the Mediterranean coast has added almost 100 million new inhabitants, and in Spain we concentrate more than 40% of our population in the coastal strip. We have built on top of ravines and we have asphalted and sealed entire floodplains driven by tourism and urban pressures. And here comes the ‘Levee Effect’. We make a concrete channel to protect a town, people feel safe, and city councils allow building thousands of houses just behind the wall. When a DANA or a historical flash flood arrives that overcomes that wall, the water wipes out everything. The work that was supposed to protect us ends up generating a trap of massive exposure.

Satellite diagnosis of the 2024 DANA

• Extension: 199 km² flooded in the Valencia Metropolitan Area.
• Exposed population: ~90,000 direct residents (~7.8% of the metropolitan population).
• Affected critical infrastructure:
  • 50 schools flooded or in exclusion zone.
  • 7 health centers/hospitals affected.
  • 30 km of railway lines and 15 km of highways underwater.
• Agricultural impact: 129 km² of rice fields in the Albufera submerged.

In many areas of Catalonia, a similar event would have similar impacts, due to the high degree of exposure.

Source: Castro-Melgar et al. (2025)

Pre and post DANA orthophotos (infoDana)

Flood zones in the Maresme (ACA)

Outline: Use Sentinel and Landsat data to show the spatial dimension. It’s not just a ravine, it’s a flood stain that covers almost 200 km² of productive and residential territory.

Schools and educational centers

• High exposure and unfeasibility of transfer: Educational centers concentrate vulnerable population in risk zones.
  • In the Valencia DANA (2024), 50 schools metropolitan were affected (Castro-Melgar et al. 2025).
  • In Catalonia, the Sustainability Observatory points out dozens of schools at serious risk. Local authorities assume that relocating these buildings is “almost impossible”, leaving emergency management as the only defense (Sánchez 2024; Elansari 2025).

• Suspending classes saves lives: In the 2024 DANA, the University of Valencia proactively suspended its activities due to AEMET’s red alert, saving lives by avoiding thousands of trips (Martin-Moreno et al. 2025).

• Difficulties in enforcing protocols: According to the protocol, the priority is safe confinement (Departament d’Ensenyament 1998).

  • Recently, at my children’s school they called us to pick up the children at the peak of precipitation.

• Education for resilience: It is urgent to integrate educational programs in natural risks to foster the real perception of danger and self-protection from childhood (Martin-Moreno et al. 2025; Olcina and Morote 2025).

Outline: Let’s stop at one of the most critical infrastructures: schools. They have a double vulnerability: they concentrate the most defenseless and they are physically very exposed. Only in the Valencia DANA, satellites confirmed 50 flooded colleges. In Catalonia the situation is very serious. There are regions like Maresme or Baix Llobregat full of schools and institutes in preferential flow zones. The mayors themselves recognize that moving those buildings is economically unfeasible. Therefore, we play everything on one card: emergency management. The great operational success of the DANA was the University of Valencia, which cancelled classes 12 hours before the SMS from the Generalitat, preventing thousands of people from taking the car. And here enters the great challenge for you as managers. I’ll give you a real case: in my children’s school, which is in a flood zone, they called us to pick up the children at the peak of precipitation! This is a massive mistake. The ‘Pla d’emergència del centre docent’ of the Generalitat explicitly prohibits it: it says that you have to keep the children inside, take them up to high floors and not go out into the street. Allowing dozens of parents to take the car desperate in the middle of the storm to go to school is a death trap that collapses access and your rescues. Therefore, if we want society to react well in the future, risk culture must not only be applied in schools, but must be mandatory taught in them.

Campings

• The magnitude of the risk: Four out of ten campings in Catalonia (124) are in potentially floodable zones. The ACA has identified 16 campings in critical situation (3Cat 2024b).
• Decree Law 17/2025: Case-by-case review. The new guidelines require strict Self-Protection Plans (PAU) and Early Warning Systems (SAPI) that guarantee a warning time that is, at least, double the time necessary to evacuate (Direcció General de Protecció Civil 2023; Abril Cabreros 2025).
• The Alcanar case, 2021: In Alcanar, the flood forced the evacuation of campings under the storm, dragged 600 vehicles and generated more than 11.5 million euros in damage (Llasat et al. 2025).

• Biescas, 1996: Camping located on an alluvial fan. 87 dead. Current Catalan regulations, in these situations, require unfavorable reports and forced transfers if they are not relocated (Direcció General de Protecció Civil 2023).
• Tourist vulnerability: Population that ignores Mediterranean torrential violence. To mitigate it, 3 new meteorological radars will be installed in the Pyrenees to gain critical anticipation time (3Cat 2024a).
• Will brave decisions be made?: There is a risk of yielding to technological temptation that does not resolve the underlying problem: location. The technological solution creates a false sense of security that can perpetuate exposure.

Outline: Let’s stop at the campings. The conflict between tourist economic activity and human safety. Today we know that 4 out of 10 Catalan campings have some risk of flooding, but there are 16 whose situation is critical. The sector has often felt in the crosshairs, but the recent Decree Law 17/2025 does not seek to make a “black list” to close them tomorrow, but to evaluate them one by one. The key now is in self-protection. The new Civil Protection instructions for campings are very clear: if you are in a flood zone, you must have your own Early Warning System (SAPI) and demonstrate that your warning time gives you margin to evacuate everyone twice. This doesn’t just happen in the narrow valleys of the Pyrenees. On the coast, as we saw in Alcanar in 2021 (one of the worst events of the last century there), urban planning around streams forced total evacuations very difficult under the storm and the water swept away 600 cars. And of course, the case that changed history: Biescas in ’96, with 87 dead. That taught us that putting tents on a natural alluvial fan is a death trap. Today, the law already classifies building on alluvial fans as “Situation 1”, which involves unfavorable reports if the facilities are not moved. For you, the emergency teams, evacuating thousands of tourists at dawn in 45 minutes is logistically almost impossible. That’s why, in addition to the plans, the Government has announced the purchase of 3 new radars for the Pyrenees, because in flash floods, gaining 15 minutes of notice is the difference between life and death.

Reduction of exposure

• Restrictive territorial planning: Urban policies must bindingly integrate risk maps, restricting or prohibiting new construction in high-risk zones and floodplains (Castro-Melgar et al. 2025; Verdú Martínez 2025).
• Relocation and “managed retreat”: For already urbanized areas with critical and unbridgeable risk, the long-term need to move key infrastructure and encourage migration or relocation of populations toward safe zones is raised (Viglione et al. 2025; Ward et al. 2020).

• Avoid false security: Avoid that the construction of defenses (walls, channeling, alert systems) serves as an excuse to make difficult decisions (Viglione et al. 2025).
• Recovery of fluvial territory: Instead of confining rivers, we must preserve and restore floodplains as buffer zones. Returning space to the river prevents, de facto, human exposure in the direct impact zone (Castro-Melgar et al. 2025).

We must stop fighting nature and start living with it.

Outline: If reducing vulnerability was about “making us stronger”, reducing exposure consists simply and plainly of “getting out of the way”. How do we get people out of the path of water? The main measure is land use planning. It must be strictly forbidden to continue expanding cities toward floodable zones. Recent studies after the DANA warn that risk maps have to be binding laws for city councils, not simple recommendations that can be skipped. But what do we do with what is already built in the middle of a ravine? Science begins to talk seriously about “managed retreat” or relocation. In the long run, maintaining certain neighborhoods or critical infrastructures on the target is unsustainable; sometimes the only safe way out is to plan their move to higher ground. In addition, we must control the ‘levee effect’: we cannot build a concrete channel and then allow thousands of homes to be built around it thinking that the risk is zero, because the day the water overflows the channel, the catastrophe will be total. Finally, the best way not to occupy the river space is to give it back. Reclaiming the “fluvial territory”, leaving natural plains without asphalt, is the physical guarantee that the water will have where to expand without taking human lives with it.

6 Conclusions

Conclusions (I)

• Disasters are not only natural: Flood is a physical phenomenon; catastrophe is, to a large extent, a human-origin phenomenon.
• Climate change is a risk multiplier, but not the cause: Increased exposure and vulnerability are mainly responsible for the increase in flood damage in the Mediterranean.
  • Without climate change we could suffer catastrophes similar to the DANA, although with less frequency and, surely, intensity.
  • Climate change increases the probabilities of extreme phenomena: More favorable conditions are being generated for Mediterranean flash floods.
  • The impact is being more through temperature than precipitation: Precipitation trends are very insignificant, but the increase in temperature increases the atmosphere’s capacity to generate extreme rains and this process is unstoppable.
  • It is difficult to know precisely how much more it will rain in the future, but we know that, even with current climate, risk maps and infrastructures designed for the 20th century are no longer sufficient. We must apply the precautionary principle and oversize safety.

Conclusions (II)

• Urban planning of the last decades has worsened exposure: if there had been no urbanization in risk zones, the DANA would have been an extreme meteorological event, but not a human catastrophe.
• We must make brave decisions to reduce exposure: land use planning must be restrictive, and in critical cases, relocation of infrastructure and even populations should be considered.
• We must stop fighting nature and start living with it: instead of trying to contain water with walls, we must recover the natural functionality of basins.
• Technological solutions that generate false security must be avoided: structural defenses (walls, channeling) and alert systems can be useful tools, but they cannot be an excuse to continue building in danger zones.
• We must reduce vulnerability in all its dimensions (social, economic, institutional, etc.) so that society is more resistant to inevitable impacts. In a world of floating population this is a huge challenge.

Conclusions: Operational and tactical challenges

• Warnings: Warnings must be automatic, immediate and behavioral (clear patterns like immediate vertical confinement). A good balance must be found to avoid the “boy who cried wolf” effect. The population must trust whoever publishes the warnings.
• Data: In a hyper-connected world we must take advantage of all possible data, official and citizen (citizen observation networks).
• Urban trap: Rescue teams must prepare for hyper-concentrated flows (mud, vehicles and debris) that annul technology, block access with physical barricades and transform streets into lethal fluvial canyons.
• Disinformation: In the midst of chaos, hoaxes can generate institutional distrust and hinder the work of emergency teams. Media literacy training is key to combat this “infodemic”.
• The Firefighter as a prevention agent: The most successful intervention is the one that does not occur. Your work includes social pedagogy: you are the most credible prescribers to teach that, before a red alert, the car is a death trap and the first floor is salvation.

Questions and debate

Authorship notes

• This presentation was made by Dr. Pere Quintana Seguí, researcher in hydrology and climate change, at the Ebro Observatory (Universitat Ramon Llull - CSIC).
• The content is based on an exhaustive review of the most recent scientific literature on floods in the Mediterranean, as well as on data and analysis of recent events such as the Valencia DANA (2024).
• Artificial intelligence tools have been used to produce the presentation for the generation of illustrations, infographics, summaries and information organization, but the content has been carefully reviewed and validated by the author to ensure its scientific rigor. Specifically, Gemini, Gemini CLI and NotebookLM have been used.

• Anaïs Barella Ortiz has carried out a final review to improve the wording and clarity of the messages, but the scientific content and conclusions are entirely Dr. Quintana’s.

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