More than a million houses are being built in Spain in at-risk areas, most of them on the Mediterranean coast. Decades of uncontrolled urban planning practices that take effect today in the event of DANA or any other extreme phenomenon, experts explain.
“The problem is that we have built a lot over the last few decades. Since the 1960s, the territory has started to be occupied in a way that is disrespectful to nature and we are now paying the consequences. We see houses practically stuck in ravines, industrial warehouses, road bridges built without the necessary dimensions to evacuate flood waters…,” asks Jorge Olcina, professor of regional geographic analysis at the University of ‘Alicante.
Intensive land urbanization in many areas of the Mediterranean coast of the peninsula has worsened the flooding that causes phenomena such as DANAS. “The occupation of areas prone to flooding has aggravated the problem in the south-east of Spain,” explain the researchers from the University of Alicante in their work. Coping strategies.
The multiple works and investigations which have proven that building in areas at risk of flooding in the event of torrential storms multiplies the danger are clear: the waterproofing of the land by construction – that is to say the covering with concrete , asphalt or metal – reduces drainage water. when it rains, which “increases the risk of flooding of 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 the increasing sealing of land”. This waterproofing, which makes the structure watertight, carries a greater risk of flooding because “the natural retention of water by 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 favors 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 to have increased its waterproofed area the most in absolute terms, behind France, according to the European Environment Agency (EMP).
The work of Alicante scientists shows that, in the context of climate change, “the increase in intense storms and impervious surfaces due to excessive urbanization has led to an increase in urban areas affected by flooding”. 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 the excesses of the past, “in Spain there have been regulations for several years that prohibit the occupation of flood-prone land, for example the Land Law of 2015. The autonomous communities also have special risk management plans that force them to do so. . map and regulate land use in risk areas… It’s there, but it must be respected,” he adds.
The professor reminds that these situations are (somewhat) provided for by law, although, as García explains, when it rains a lot, we know where the water is going, we can calculate how much it will fall, but you don’t don’t know when. “The law on climate change requires that all territorial planning integrates the climate change variable. Today we already have models that indicate what will happen, and which must be transmitted to the territory and raise the level of caution. It is necessary to demarcate larger spaces as flood zones, not just what the water law tells us, because we see that the return times [la probabilidad de cuándo va a volver a suceder un determinado evento] “They are fighting faster and faster.”
García explains that infrastructure like a dam or canal is designed with the biggest flood it could experience in 1,000 years in mind (there are different time scales for different types of construction and depending on the severity of the flood). flooding), but there is a risk that, as with return periods, the calculations become obsolete and new estimates will have to be made. Either way, it’s a bad solution, he adds. “What do we do in this case? Cultivate dams? Strengthen the channels? It’s not very clear how we might act,” he says.
“Reduce water consumption”
The flood adaptation guide from the Ministry of Ecological Transition explains that “when intense rains occur, the use of impermeable sidewalks and the direct channeling of runoff water lead to the creation of wide avenues of water which cause flooding. collapse of the general evacuation network. In other words, if it rains a lot, this impermeable terrain increases the volume of water and accelerates the speed of flooding. This is where the overflow comes from.
This is why García emphasizes the concept of “reducing the energy” of water. The EU, he said, is committed to the path of recovering natural river channels, as has been done for example in Madrid or is being done, in sections, in the Los Angeles River ( UNITED STATES). “The naturalization of rivers makes it possible to laminate the avenues [disminuir el caudal y potencia de una riada] when vegetation grows and nature expands,” he illustrates. Just as seaside dunes protect coastlines from encroaching water, he explains, unchanneled natural rivers do so with their flow.
At the same time, more than a million homes in Spain are built in risk areas, i.e. 4.3% of Spanish homes and the majority in the Mediterranean. For them, there is no good solution, explains García: “They should not be there from the beginning” and they risk experiencing this phenomenon again.
In Spain, there is a vast territory very exposed to flooding. The sections presenting an obvious risk total nearly 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.
