In the aftermath of the catastrophic floods in the Valencia region of Spain, our member CIREF published the following translated article. It provides a science-based analysis of what happened, in order to combat misinformation and offer solutions that help prevent future disasters.   

After the catastrophe associated with the DANA event of October 29, 2024, CIREF would like to highlight and express the following considerations: 

First of all, from the Iberian Centre for River Restoration (CIREF), we want to express our utmost solidarity, affection and support for all the people affected by the tragedy as a result of the recent DANA (an isolated, high altitude, low-pressure weather system) that occurred between late October and early November of 2024. We express our solidarity especially to the victims and their families, but also to all those volunteers, belonging to different NGOs and professionals from different bodies and administrations of the State, the Valencian Community and other affected Autonomous Communities, who have worked and continue to work today in the care of the victims to restore normalcy as soon as possible.  

For all these reasons, we believe that it is worthwhile to contribute our methodical and scientific-technical analysis to this situation, with the objective of contributing to a greater empowerment of the population that will allow them to combat misinformation, and to alert the administrations so that events with such serious consequences do not repeat themselves. 

What Happened

An intense DANA, stabilized in the middle of the Peninsula, and fed by an overheated Mediterranean Sea, generated rains of great volume and intensity in different territories, reaching maximum values in the interior of the province of Valencia. From there, rivers, ravines and wadis (normally dry stream beds) have done their job of evacuating water and sediment to the sea. And the flood plains have also done their job of widening the river bed, dissipating its energy and temporarily storing water. This is a normal natural process, even with extreme conditions, like others that occurred throughout history and will surely occur in the future; it is a natural process necessary for planetary balance and its global health, to readjust atmospheric balance with the terrestrial and marine hydrogeomorphological balance. 

A Paradigm Shift

A natural process of these characteristics and magnitude, and even greater, is likely to occur more frequently in the Peninsula in the future, as a consequence of the anthropogenic climate change that has been leading us to increasingly higher temperatures, which have not slowed down and are driving us towards more frequent extreme phenomena. This forecast, supported by numerous scientific studies, will require major changes in human activity and settlement, which will have to be governed urgently and increasingly by the principles of humility, prevention and adaptation. 

We could venture that extreme climatic processes such as this one are already entering a new paradigm, more similar to volcanism. That is to say, processes that cannot be effectively contained with infrastructures and for which the only effective measures are to remove settlements from their reach, and to quickly and effectively evacuate the remaining population. It will therefore be very important to improve and deepen measures related to prevention, training the population and even developing simulations in areas with special risk. 

The Consequences

The damage caused by the catastrophe is entirely the result of human actions, due to exposure and vulnerability, in a highly urbanized area that is not adapted to extreme natural processes, even under normal climatic conditions. Urbanization makes land impermeable, increasing runoff from rainfall, and the foundations and subterranean garages that occupy the alluvial plains push more water to the surface. All this causes the three types of regular floods to become synergistic: pluvial flooding (occurs when an extreme rainfall event creates a flood regardless of whether there is an overflowing body of water), fluvial flooding (or river flooding) and phreatic flooding (when there is an exceptional rise in the level of the water table closest to the ground). 

The high load of sediments in flood waters, resulting from erosion that is sometimes also increased beyond what would be natural due to deforestation or degradation of the river basin, together with the plant matter from invasive species such as reeds (Arundo donax), vehicles, household goods, etc., increase the volumes and the capacity of water flows to generate damage. 

In turn, poorly dimensioned bridges, roads and other infrastructure installed in flood plains have altered flows and led to and aggravated the problem in specific areas. There are streets, homes, retirement homes, educational centres, and other essential public services built within in areas of maximum flooding.  

This disastrous outcome was foreseeable, as our towns have been developed in recent decades without adequate territorial and urban planning, prioritising economic interests over caution. This could have happened in other places and unfortunately it will continue to happen in the future, because today we have tools, mapping of flood zones, risk studies, studies on the effects of climate change, etc., that allow us to be very aware that much of our territories are not adapted and are highly vulnerable; in short, the risks are known. 

The Solutions

The current situation of many territories, aggravated by climate change and new infrastructure being built, should force us to regularly update flood-prone area mapping  and continuously re-evaluate risk. Let us consider that the greater frequency and intensity of expected events implies: 

• Clear reductions in return periods (the average number of years that elapse between two successive occurrences of a given event). 
• Increases in flows (the volumetric flow of water passing through a given point of a river), and depths (the height that the water surface reaches above the bottom).
• Greater extension in channels and floodable areas.   

Measures to solve or mitigate the effects and risks: 

Addressing land use planning and urban development in flood-prone areas in a radically different way, reorganising land use and leaving most of the surface and subsoil for the natural expansion and transport of sediment in these extreme processes, that is, vacating as much of the flood-prone areas as possible.  

• Give more space to the river channels and to reduce their energy, speed and destructive capacity, and reconnect the channels with their flood plains, true natural lamination (sediment transport).
• Redevelop or remove vulnerable constructions and infrastructures that pose a risk to people.    
• Adapt buildings in flood-prone areas that need to remain by eliminating or disabling basements and ground floors. 
• Resize bridges and other infrastructure, and continue to eliminate, with the utmost urgency and intensity, dams, barriers, fords and unnecessary or obsolete obstacles of all kinds, which prevent the proper transport of sediments and infiltration of the channels.  
• Apply sustainable urban drainage systems to encourage “sponge cities” and improve conditions in cases of heavy rainfall not associated with overflows, since they reduce stormwater runoff, which is rainwater not absorbed by the urban surface. 
• Forget about concrete as the only solution and abandon defence schemes based on river channelling, as done in the past. Some channelled sections in consolidated urban areas should be maintained or improved, but under no circumstances should this solution be generalized to other areas and river sections where it has been shown that concrete infrastructure has only exacerbated the problems and damage. 

In short, we must opt ​​for intelligent solutions based on nature, which imitate it, adapt us to it and adapt as best as possible to each case and territory. 

The Future must be Now

Geography, geology, ecology, environmental sciences, social sciences, engineering and architecture have a lot of knowledge to contribute and should be much more involved in decision-making. They have to contribute to a new land use planning, to the return rivers  their space, to a new way of building and to a new way of living where health and well-being take precedence over capital. 

For this reason, it is also necessary and urgent to increase early warning systems for floods, especially in torrential river basins with very few gauging stations up until now. Along these lines, it is essential to link meteorological warnings to hydrological warnings and generate a faster mechanism for issuing social warnings that are clear and forceful, without exception, and prevent personal injury. 

Progress must also be made in the dissemination and awareness of the population, and in the development of protocols and drills so that everyone knows what to do. Without forgetting that, according to the criteria of the Flood Directive 2007/60/EC and Royal Decree 903/2010, on flood risk assessment and management, municipalities classified as Areas with Significant Potential Risk of Flooding (ARPSI) must draw up their corresponding Municipal Action Plan. The drills make it possible to validate and adjust these Plans, as well as the operation of their Early Warning Systems. 

The recent catastrophe in Valencia, as well as in other areas of Castilla-La Mancha and Andalusia, is a consequence of prioritising the economy over the safety and health of people, the belief that our technological capabilities are above the evolution of nature, and also, not always but unfortunately on many occasions, the incompetence, lack of coordination and efficiency of the administrations, all aggravated by climate change. 

Our recognition and gratitude to the forecasting mechanisms, the AEMET and the SAIH (Automatic Hydrological Information Systems managed by the Hydrographic Confederation), for their accurate and rapid predictions, to the emergency services, civil protection, the UME, security and public order forces, as well as to the volunteers who, even as we write this note, are giving their all to help people and return normalcy to the affected areas as soon as possible. Our reprobation of the political irresponsibility that delayed and minimized the alerts (with dramatic consequences), to those companies that put production and business before the safety of their workers, to the hoaxes and misinformation and political battles that are hindering and slowing down the post-catastrophe management. 

The magnitude of this catastrophe must now imply a turning point, a before and after, which forces us to change behaviours, regulations, protocols and laws, to review our environmental, social and economic health priorities (which must be in this order, never the other way around) and to modify, ultimately, our way of understanding and managing the territory and risk prevention. We believe that prioritising an economic model that integrates these elements and priorities will also ensure that the economy and jobs of the future do not depend on assuming high and unnecessary risks. 

In Zaragoza, November 13, 2024. Originally published in Spanish on the CIREF website: https://cirefluvial.com/consideraciones-sobre-la-dana-del-29-deoctubre-de-2024/  

The Iberian Centre for River Restoration (CIREF) is a non-profit association that integrates professionals linked to the restoration of river areas in the Iberian Peninsula, both from the university, the administration, the field of consulting or technical assistance and non-governmental organizations. CIREF’s main purpose is to defend the conservation of fluvial ecosystems and the restoration of their ecological state.  

Contact person and phone number:  Camila Kuncar / +34 625 950 235