Valencia floods, one year on: what have we learned, and how can we prevent similar tragedies in the future?

On October 29 2024, destructive storms hit several areas of the Iberian peninsula, causing the most extreme rainfall recorded in Spain during the 21st century. According to the Spanish State Meteorology Agency (AEMET), they were caused by a mass of cold air at high altitude between the Gulf of Cádiz and the Gibraltar Strait, which pushed very humid air from the Mediterranean towards the coast. Storms formed in chains, which were repeatedly reactivated over the same areas. In Turís, in the Valencia region, the AEMET recorded 185 litres per square metre (l/m²) in one hour, and 772 l/m² within 24 hours. The combination of extreme intensity and persistence triggered flash floods within a few hours. Read more: Valencia floods: Our warming climate is making once-rare weather more common, and more destructive The Júcar Hydrographic Confederation – which administers the Júcar river that flows through Castilla La Mancha and Valencia – estimated maximum flows of 3,500 cubic meters per second (m³/s) at the intersection of Rambla del Poyo and the A-3 motorway, and 2,400 m³/s where the Magro River meets the Forata dam. Satellite images show clouds gathering over eastern Spain at 6:30am on October 29, 2024. EUMETSAT, CC BY-NC-SA In addition to the 229 deaths in the Valencian Community, there were seven in Castilla-La Mancha (one in Mira, in Cuenca, and six in Letur, in Albacete) and one in Andalusia, in Alhaurín de la Torre, Málaga. 68 of the deceased were found on the ground floors of homes, and 35 in car parks and basements. According to Spain’s Data Integration Center (CID), more than half of the victims were aged 70 or over, and 15 were aged 90 or over. 24% of deaths were in the 80-89 age bracket, making it the largest group. What caused the tragedy? Construction in river areas intensified during Spain’s rapid development during the 1960s and 1970s, and also during the property bubble from 1997 to 2008. Indeed, of the 75,000 homes affected by flooding, 31% were built during this second period. The physical vulnerability of the buildings exacerbated the tragedy, as many ground floors became death traps once they were flooded. At 7:36am on 29 October, the AEMET issued a red alert for extreme rainfall. According to the Valencian government, the Júcar Hydrographic Confederation reported that at 12:07pm the Rambla del Poyo had exceeded the pre-alert threshold. By 18:43, the flow had reached 1,686m³/s. The Valencian government did not activate its Integrated Operational Coordination Centre (CECOPI) until 5pm. The ES Alert public warning system was not activated until 8:28pm, by which time many areas were already underwater. Read more: Why it can be hard to warn people about dangers like floods – communication researchers explain the role of human behavior Although the central government offered support from the outset, there was controversy over the level of its involvement, as it did not assume full control by declaring a national emergency. The low perception of risk among the general population, together with the delay in the ES Alert warning, were decisive factors. The fact that it was not actually raining in many of the affected towns created an additional false sense of security among residents. This led to risky behaviour, such as going down to garages to rescue vehicles and driving on flooded roads. Preventing future tragedies The good news is that there are actions we can take to prevent similar weather events from having such tragic consequences in the future. They can include the following measures: Characterise the uncertainty of risk analysis: Maps must be developed that quantify the probability of flooding in different areas as a percentage. This approach enables more effective land use planning – areas with a higher likelihood of flooding have greater restrictions, while areas with a lower probability can be used for purposes that entail a certain degree of risk. Map of flood risk probability. Red is the highest risk, followed by orange and green. Bodoque et al., 2023, CC BY-SA Integrate vulnerability and resilience into risk management: Develop indices to identify areas where the population is less able to adapt, as well as unsuitable housing conditions (ground floors, basements), mobility limitations or social isolation. With this information, authorities can design specific evacuation plans for vulnerable populations, establish neighbourhood support networks, and prioritise improvements to the most vulnerable homes. The areas of Castile and León that appear coloured on the map are vulnerable to flash floods. The clusters represent groups of towns with similar vulnerability characteristics. Aroca-Jiménez et al., 2022, CC BY-NC-SA Mitigate risk through structural measures: Among other things, this could include more efficient urban drainage systems, as well as dams at the head of rivers and storm tanks to mitigate flash floods. Self-protection measures in homes should also be promoted. These include permanent automatic water pressure barriers, pneumatic floodgates and watertight doors. Read more: Beyond sandbags – how to defend your house from flooding Improve risk awareness: Communication plans must be designed to increase public awareness of flood risks. Compulsory risk education programmes should be part of all non-university education, as proposed in the Civil Protection Emergency Training Plan. Photography and video competition on flooding as part of the risk communication plan for Navaluenga, Ávila. Bodoque et al., 2019, CC BY-NC-SA Promote participatory governance: Strengthening social capital is an effective way to improve community resilience. It enables participatory governance by creating spaces for dialogue where stakeholders (civil society, authorities, experts) can engage in decision-making on risk management. Implement a decision support system (DSS): A DSS must be implemented that connects AEMET data with the records of the Júcar Hydrographic Confederation in real time. The DSS would provide continuously updated information on rainfall intensity and water depth, enabling quick decision-making and reducing the need for consultations between administrations. Successful flood risk management demands a profound transformation that combines scientific knowledge, citizen participation and political will. The experience gained must translate into better informed and prepared societies, capable of anticipating and adapting to an increasingly challenging climate context.