floods, collapses and landslides, because so many warnings

Over 500 mm of rain, a third of what falls in a year, in just six hours: it happens in Liguria, which with that half meter of rainfall wins a sad national record. With the arrival of autumn, in an era in which floods and floods are a disturbing and increasingly frequent side effect of climate change, it is Liguria that suffers without many surprises. And it does so immediately, passing from a hot and dry summer season to a red alert, the first, which dropped a “water bomb” that targeted Savona and its province above all.

In Savona floods, landslides and floods. Quiliano, a bridge collapses

The damage was immediately very heavy, the images shocking: numerous streams were flooded – the Letimbro in Santuario, the Erro in Pontinvrea, the Bormida in Cairo Montenotte, flooding cities and towns, forcing emergency closures and evacuations as a precaution. and reopening old, largely badly healed local wounds.

In fact, there are countless landslides and landslides, with heavy repercussions on traffic, road and motorway closures and slowdowns to railway lines. Dozens of families remained isolated due to the flooding of streams, flooding, the presence of fallen trees, boulders and earth on the roads of a hinterland difficult to reach even with emergency vehicles. Not to mention the dozens of interventions to save people in danger or to make roads and structures safe: in Savona a bus was dragged by the violence of the water and a woman was rescued by the firefighters after being stuck in a car, in Quiliano a bridge collapsed in Tecci overwhelmed by the fury of the river, a vaccination center was closed in the Imperia area, also closed tunnels and underpasses that could turn into deadly traps, countless funds, cellars and flooded doors.

Flooding in Savona – Giovanni Toti Facebook credit

The unpredictable front that crosses the whole of Liguria

In light of the forecasts, and of the fact that the front of bad weather is moving slowly and unpredictably on the Ligurian territory, the Region has decided to extend the red alert until Tuesday morning: on the first day to end up in the viewfinder is was the west, but from Monday evening it will be the turn of the central part of Liguria and Genoa, with its hinterland already battered by landslides and floods (the Stura and Orba valleys in particular). And the appeal arrived both from the president of the Region, Giovanni Toti, and from the mayor of Genoa Marco Bucci is the same: “Stay at home, keep your travel to a minimum”. Not surprisingly, for many municipalities the closure of schools was decided, mindful of the tragedy of the flood of November 4, 2011, when at lunchtime the Fereggiano and Bisagno flooded killing six women who were returning home, some from work , others from school.

Arpal, the Ligurian Regional Environmental Protection Agency, has also warned against the front that has hit Liguria by analyzing its particularities, which collide – literally – with those of the region itself. Federico Grasso, an official of Arpal, explains it well to Today: “What is happening in Liguria in these hours is the result of a series of contributing causes. First of all, in the morning we had two very intense phenomena, between 4 and 11 the first and the second entered in full at 14, and at 17 still in progress. These are stationary phenomena that pour large quantities of water on the same territory for a long time. This morning it was the turn of the Bormida valley, in the afternoon the levels of the streams in the Stura valley are rising, we have had confirmation that the Orba has come out and we are also above the guard threshold in Campo Ligure ».

The map of the rain that fell on Liguria at 2 pm – source Arpal

Because Liguria is a land of warnings and floods

But why are floods and floods so frequent in Liguria, and always in the same periods? “The main point is the position – explains Grasso – The mountains that form the Ligurian arch are the first barrier that the currents from the south encounter as they go up the peninsula, with the Scirocco blowing in the corridor between the Italian peninsula, Corsica and Sardinia. . A current of hot air is generated which, upon encountering the Ligurian mountains, is forced to rise. At that point the air cools and precipitates, with consequent storms. Not only that: winds and currents come from different directions at the height of Liguria. and with different temperatures, an intersection that helps to form stationary lines in which it always rains on the same point for many hours. This ‘crossing’ also feeds into the Ligurian Sea basin, which in September-October is still warm, and the air absorbs even more humidity: we are in the worst situations, which is why phenomena of this kind are always recorded in September, October and November ”.

In October 2019, for example, it was the turn of the Stura valley; the year before a violent storm, the result of a very similar bad weather front, scourged the coast of the Ligurian Levant causing enormous damage; and then Genoa, with the floods of 2010 (precisely on 4 October, in Sestri Ponente), of 2011 (4 November) and of 2014 (9 and 10 October), seven victims and damages of millions of euros. Today Genoa relies on floodwaters: one, that of the Fereggiano, is already finished and functioning, the other, that of the Bisagno, should be so in 2024, but in the meantime the coverage has been completed. The objective is to try to contain and lower the level of two of the numerous streams, perhaps the most dangerous, that flow near or in the belly of the city and which in the event of a flood could become unstoppable again.

On the border between Piedmont and Liguria 178 mm of rain in one hour

Maximum attention therefore in the Ligurian capital between the evening of Tuesday and the night between Tuesday and Wednesday: “The stationaries will go on for one or two hours until the bad weather front completely enters our region – explains Grasso – it is a structure that extends for a thousand kilometers, imposing, capable of wiping out any other structure present. And this very energetic passage, with air masses with different temperatures, will accentuate the contrasts, causing widespread rains and thunderstorms that could be more intense than those we have seen. Just to give an example: in Urbe Vara Superiore, on the border between Piedmont and Liguria, 178 mm of rain fell in an hour. The record is 181 in Vicomorasso on November 4, 2011. The structure will cross the whole of Liguria in 6-12 hours depending on the obstacles it will encounter and “light up” the atmosphere, giving rise to very intense storms with gusts of wind accompanied by the phenomenon of the “downburst”, masses of air that the precipitation of water causes to move violently. Maximum attention is also paid to the sea: the Scirocco, which in the night will turn to Libeccio, will cause a powerful storm “.

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