Water dynamics in southeastern Spain have a rhythm all their own. Riverbeds can remain nearly dry for extended periods, only to be transformed into raging torrents by sudden heavy storms. This phenomenon is deeply woven into the region’s culture and even its language, with terms like rambla, meaning “a natural channel for rainwater during periods of heavy rainfall,” and torrente, which refers to “a sudden, forceful rush of water caused by heavy rain or rapid snowmelt.” Reflecting on the tragic events of last week, a Spanish journalist recalled the words of Valencian singer-songwriter Raimon, who poignantly remarked, “In my country, the rain doesn’t know how to rain—it rains either too little or too much”.

“Al meu país la pluja no sap ploure/ O plou poc o plou massa”

By the time I am writing this article, 200 people have tragically lost their lives in Valencia [1]. Entire villages have been submerged, with water and mud destroying everything in their path. The devastation is truly heartbreaking.

Before diving into anything else, I want to share some resources and accounts for those who may be able to help:

• Red Cross Donation Hotline: +34 900 104 971
• Caritas Food Bank Account: ES19 3159 0078 5716 6338 6025
• Spanish Food Bank Association Account: ES34 2100 6106 8813 0126 8072
• GoFundMe for Affected People: Help for Flood Victims in Valencia

No matter how small, every contribution can make a difference during this crisis.

As mentioned above, water dynamics in this Mediterranean region follow a cycle of drought and intense rainfall events. It’s common for rivers to experience return periods, during which the river basin is inundated with heavy water discharges. In hydrology, a return period refers to the average number of years between the occurrence of floods of a certain magnitude.

The best way to understand this concept is through visual representation. In Figure 1, we see areas likely to be flooded every 10 years (return period = 10 years). In Figure 2, we compare this with areas affected by a 100-year return period. While higher return periods correspond to more severe flooding, they occur less frequently.

Fig.1: 10-year return period map showing data in the Valencia area, Spain. Map from the Ministry for the Ecological Transition and Demographic Challenge (MITECO).

Fig.2: 100-year return period map showing data in the Valencia area, Spain. Map from the Ministry for the Ecological Transition and Demographic Challenge (MITECO).

With climate change, extreme weather events are becoming increasingly common. We are now witnessing occurrences that should have a 100-year return period happening far more frequently than expected.

In this context, a gota fría (cold drop) refers to a depression of cold air at high altitudes, also known as a DANA (the Spanish acronym for Depresión Aislada en Niveles Altos) [2]. These air masses can span up to 2,000 kilometers in diameter. When they collide with warmer, more humid air currents, the result can be atmospheric destabilization and episodes of intense, heavy rainfall.

Of course, not every DANA results in rain, but when it does, the consequences can be as catastrophic as what we’re seeing now.

Nothing we can do to control the weather, but we can control how we build and develop our surroundings. In this case, the natural factors—such as unusually high rainfall and river channels multiplying their flow rates within hours—are beyond human control. However, one major contributor to the severe impact of this DANA has been the impermeabilization of the soil.

In this river basin, a significant portion of the land—20% of its surface—has been rendered impermeable, meaning water cannot seep into the ground [3]. Industrial and urbanized areas lacking green spaces exacerbate the problem by preventing water infiltration. As a result, all the water—and its tremendous force—remains on the surface, intensifying the damage caused by flooding.

This issue is not new. In 1998, the Yangtze River in China overflowed, partly due to soil impermeabilization. Rapid urbanization and accelerated industrial development paved over fields and green areas with roads, industrial zones, and expanding cities. The combination of excessive urbanization, deforestation, and heavy rainfall led to a catastrophic flood that claimed 3,700 lives [4].

To address such events, nature-based solutions (NBS) offer a promising path forward [5]. One example is the implementation of sustainable urban drainage systems, which involve incorporating green spaces throughout cities and urbanized areas. Parks, gardens, and other vegetated areas act like natural sponges, absorbing excess water and easing the burden on artificial drainage systems.

Nature-based solutions focus on protecting, restoring, and sustainably managing ecosystems to increase their resilience and capacity to respond to extreme events like the one Valencia experienced just weeks ago.

To sum up, we urgently need policies that heed the warnings of scientists—policies grounded in ecological wisdom and logic, rather than driven by the pursuit of profit. Rising temperatures, particularly at the sea surface, lead to increased evaporation, putting more moisture into the atmosphere and making hot air currents more frequent.

We must not only adapt to a warming climate but also address its increasingly severe effects. That is why we need to start taking drastic measures now to keep warming to a minimum, while also creating new strategies and protocols for this kind of – always more common – events.

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