The arrival of a new DANA (Isolated depression at high levels) could cause heavy rains in the Mediterranean. According to the National Meteorological Agency (Aemet), which has already activated the orange alert in the Valencian Community due to the accumulated precipitation, the southern coast of Valencia could exceed 120 mm in 12 hours.
As meteorologist Mar Gómez warns at EL ESPAÑOL, it will make it rainbecause it is likely that precipitation will also fall in some points affected by DANA, which caused the death of 214 people in Valencia.
One of the main rain-related problems in areas flooded by DANA is the sewer system, with reduced capacity due to its collapse due to mud. In this sense, the mayor of Alfafar, Juan Ramón Adsuara, assured that the Valencian emergency teams concentrate their tasks on sewer drainage and scuppers.
Although large torrential rains, like those that occurred in this Valencian municipality, are not expected, its intention is to put an end to the clogging that many drains present so that there is good drainage to deal with it. the yellow alert that was activated in this city for the next few days.
Reduced capacity, additional problems
Other affected municipalities have also focused their efforts to prevent the effects that the new DANA could cause, which is expected to turn into an isolated cold storm (BFA) starting this Thursday. This is the case of Algemesí, where they provided special attention to sewer drainage and sewers.
The municipality recommended to the population that, given the “particularly intense” precipitation expected, the use of “wood, barriers” or any other object be considered at the entrance to low-rise houses and garages. And the state of the wastewater could cause water to accumulate in the streetsso the priority right now is to clean the sewers.
In the event of heavy rain, “additional problems could be generated, such as accumulations of water, because the current evacuation capacity of the sewer networks is not the same as under normal conditions”, explains- he. Ignacio Andrés Doménechprofessor at the Department of Hydraulic and Environmental Engineering at the Polytechnic University of Valencia.
However, if the precipitation were moderate and relatively prolonged over time, he believes the opposite effect could occur. This would even make it possible to “remediate” the problem of sludge in these infrastructures, where it risks solidifying within the pipes themselves. “This could be beneficialbut this will depend on the intensity and duration of the rain, as well as the configuration of the sewers themselves.
Faster response
Although in the sewer network of some municipalities, rains can have certain advantages, from a hydrographic point of view the reality would be very different.
“The soil affected by the last DANA has a saturation level that could make it react much more quickly to further rains,” he explains. Sergio Andrés Salazar-Galánprofessor at the Department of Geography, History and Philosophy of the Pablo de Olavide University and author of a doctoral thesis which focuses on reducing the risk of flooding in the Rambla de Poyo through water retention measures on the territory.
He agrees with Andrés that everything will depend on the intensity of the rain and how long the new DANA stays. But believe that further flooding is likely. And one of the peculiarities of rain when it falls on already saturated ground is that there is a greater probability that the different tributary channels will come together.
Thus, when a large territorial extent and intense precipitation combine with saturated soils, “the perfect ingredients for a big flood“.
As two weeks have passed and temperatures have been unsuitable for this time of year, water may have evaporated in some areas. This is not the case in places where there are puddles, where the floor is “completely waterproof” and the water will fall as if it were “on a sidewalk”.
Added to this is the fact that the zero point of Valencia The storm drainage system has already collapsedbeing full of mud. Therefore, precipitation could occur where the possibility of water infiltration is zero and the soil has a certain degree of saturation.
In the case of the Mediterranean coast, this also influences the fact that a large part of the Ramblas watersheds is “anthropologically intervened”. In this way, “there is no retention capacity in the soiland the water that falls will flow on the surface, having a ground waterproofed by the sidewalk.”
