And at the center of the debate between the Generalitat and the Government, the information offered on the Poyo ravine leaves an approximation of the seriousness of the matter: the flow of the Rhine was reached. The DANA that devastated the Valencia metropolitan area on October 29 had 30% sediment of the total volume of floodwaters, an index considered “high”, although within the norm for this type of extreme weather phenomena.
This is clear from a study of the flooding of Poyo Rambla carried out that day with the TETIS model of the Hydrological and Environmental Modeling Group (GIMHA) belonging to the Institute of Water and Environmental Engineering (IIAMA) from the Polytechnic University of Valencia (UPV). The president of the Spanish Water Technology Platform and professor of hydraulic engineering at the UPV, Félix Francés, explained to EFE that this rate of sediment and debris caused a 50% increase in density.
The expert highlighted that the floods in the DANA of Valencia caused by the Rambla del Poyo and other ravines south of the capital were of the “flash avenue” type, in which “the increase in flows is very rapid and a wavefront forms and advances rapidly through the channel network.
According to Francés, this front generates a characteristic noise due to the dragging of stones, trunks, branches and reeds, among other materials, so that I could hear the flood coming. Lightning floods form in ephemeral rivers, that is to say those which dry up most of the year, and in steep and relatively small basins.
Added to all this is the fact that they are in climates likely to generate torrential storms of similar duration to the basin’s response time, a combination of factors that provides a “short reaction time” for the emergency system. Water speeds, flow peaks and significant transport of sediment and debris increase the density of water flow and, according to the professor, promote buoyancy and drag of objects found passing by. from flooding, such as vehicles. .
