The storm Leonardo little by little begins to fade from the maps, leaving in its wake mainly alerts for strong gusts of wind in certain regions of Andalusia. The problem is that its footprint on the ground is just beginning to show its true dimension, since the main danger is that even if rainfall begins to decrease, the water continues to rise in the rivers. And this gives rise to the feared floods that are already has caused numerous evictions.
Extreme saturation. To understand why authorities and the AEMET maintain the emergency level 2 and red warnings despite lulls in rainfall, we have to look under our feet. The soil functions, under normal conditions, like a sponge capable of retaining large volumes of water. However, after weeks of constant rainfall, Andalusia has reached its saturation point.
In this way, the land does not support any more water, which increases the runoff coefficient throughout the territory. This means that each new liter that falls, no matter how small, will barely filter through the ground. The result is that it will run on the surface, turning slopes and mountains into giant slides towards the rivers.
Increase of the channel. This is the reason why 14 rivers are under red notice today and another 31 under orange. Rivers such as the Guadalete, the Genil, the Guadiaro and the Guadalhorce They are not just responding to today’s rain.but to the inability of the basin to drain what has accumulated in the last 48 hours.
We have an example in Huétor Tájar in Granadawhere the Genil River overflowed, making the entire town become a large lake. And this is the main risk we face despite the fact that rainfall is beginning to reduce its intensity.
The reservoirs. The other major front of this crisis is hydraulic engineering. The reservoirs act as buffers during floodsretaining the water to prevent it from devastating the towns downstream. But Leonardo has managed to finish filling these reservoirs to their maximum limits.
This has forced us to initiate technical releases with increasing amounts of water to avoid breakages or uncontrolled overflows of the dams. The problem is that doing so injects more flow into rivers that are already at the limit of their capacity, keeping towns like Ubrique or the lower areas of the Guadalquivir in suspense.
Sierra Nevada. Gravity in the Genil basin is not based solely on precipitation, but on thermodynamics. Leonardo is not a cold storm of polar origin, but rather an Atlantic storm loaded with humidity that is causing snow accumulated in previous weeks melts at a high speed. The result here is clear: a greater flow in the rivers that drain the Sierra that joins all the factors that we have mentioned before.
Landslides. For the next few hours, in addition to the increase in the riverbed, we must also keep in mind the risk of hillslide. In these cases, water saturation increases the weight of the soil and reduces its internal friction. This translates into a greater risk of landslides on roads and slopes, something that can especially occur in mountain areas such as Cádiz or Axarquía in Malaga.
More rain on Saturday. Faced with overflowing soil, the last thing you want is to receive more rain. But the reality is that this same Saturday a new storm comes in that has already activated an orange alert in a region that has been greatly punished by Leonardo such as Grazalema. In this case, accumulations of up to 80 liters per square meter are again expected, which may further aggravate the situation that is being experienced.
Images | Ted Balmer
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