More than a million houses are built in Spain in risk areas, most of them on the Mediterranean coast. Decades of uncontrolled urban planning practices that take effect today when there is a DANA or some other extreme phenomenon, experts explain.
“The problem is that we have a lot built from past decades. Since the 60s, the territory began to be occupied in a manner that was disrespectful of nature and now we are paying the consequences. We see houses practically stuck in ravines, industrial warehouses, road bridges that are made without the necessary dimensions to evacuate flood waters…”, ponders Jorge Olcina, professor of Regional Geographic Analysis at the University of Alicante.
The intensive urbanization of the land in many areas of the Mediterranean coast of the peninsula has worsened the floods that cause phenomena such as DANAS. “The occupation of areas prone to flooding has aggravated the problem in the southeast of Spain,” explain the researchers from the University of Alicante in their work. Adaptation Strategies.
The multiple works and investigations that have proven that building on areas at risk of floods in the event of torrential storms multiplies the danger are clear: waterproofing the land through construction – that is, covering it with concrete, asphalt or metal – reduces drainage. water when it rains, which “increases the risk of flooding in populations,” illustrates the European Environment Agency.
“Water retention is reduced”
The European Territorial Development Observation Network (EPSON) also explains that “flooding has become a growing problem due to increased sealing of land.” This sealing, which is what makes it waterproof, carries a greater danger of floods because “the natural retention of water through infiltration into the ground is greatly reduced.” In runoff over concrete, explains Esteban García, civil engineer, the majority of the water that falls is not absorbed by the ground, which encourages the creation of these large avenues.
And Spain has been sealing its floors with concrete for years. The country was, between 2006 and 2015, the second EU state that increased its waterproofed surface the most in absolute terms, only behind France, according to the European Environment Agency (EMP).
The work of the Alicante scientists shows that, within the context of climate change, “the increase in intense storms and sealed surfaces due to excess urbanization has led to an increase in urban areas affected by floods.” Especially in the southeast of Spain, where this dynamic has caused “greater exposure and vulnerability of the population to new risks.”
Olcina recalls that despite past excesses, “in Spain there have been regulations for some years now that prohibit the occupation of flood-prone lands, for example the 2015 Land Law. The autonomous communities also have special risk management plans that require them to do so. maps and regulate land uses in risk areas… That is there, but it must be complied with,” he adds.
The professor remembers that these situations are (somewhat) provided for in the law, although, as García explains, when there is a lot of rainfall, you know where the water is going to go, you can calculate how much it will fall, but you don’t know when. “The climate change law requires that all territorial planning must incorporate the climate change variable. Today we already have models that are indicating what is going to happen, and that must be transmitted to the territory and raise the level of caution. It is necessary to delimit larger spaces as flood zones, not only what the water law tells us, because we are seeing that the return periods [la probabilidad de cuándo va a volver a suceder un determinado evento] “They are fighting more and more quickly.”
García explains that infrastructures such as a dam or a canal are designed thinking about the largest flood that they may suffer in 1,000 years (there are different time scales for different types of construction and depending on the severity of the flood), but that there is a risk that, As with return periods, calculations are becoming obsolete and new estimates need to be made. In any case, it has a bad solution, he adds. “What do we do in that case? Grow dams? Strengthen the channels? It is not very clear how we could act,” he says.
“Reduce water energy”
The flood adaptation guide of the Ministry of Ecological Transition explains that “when intense rainfall occurs, the use of impermeable pavements and direct channeling of runoff lead to the creation of large avenues of water that cause the collapse of the general evacuation network. ”. In other words, if it rains a lot, that impermeable terrain causes the volume of water to grow and the speed of the flood to accelerate. From there comes the overflow.
That is why García places emphasis on the concept of “reducing the energy” of water. The EU, he says, has embarked on the path of recovering the natural channels of the rivers, as for example was done in Madrid or is being done, in sections, in the Los Angeles River (USA). “The naturalization of rivers allows the avenues to be laminated [disminuir el caudal y potencia de una riada] when vegetation grows and nature expands,” he illustrates. Just as the dunes next to the sea protect the coasts from the advance of water, he explains, natural, non-channeled rivers do so with their flows.
Meanwhile, more than a million houses in Spain are built in risk areas, 4.3% of Spanish homes, and the majority in the Mediterranean. For them there is no good solution, García explains: “They should not be there from the beginning” and they are susceptible to suffering the phenomenon again.
In Spain there is a large territory very exposed to floods. The sections that show obvious risk total almost 12,000 km, according to the latest measurements from the Ministry of Ecological Transition. The danger affects more than 2.3 million people in the basins managed by the central Executive.
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