Flood in Cogne, the Italian Society of Environmental Geology intervenes –

Massimiliano Fazzini (Climate Risk Team President of the Italian Society of Environmental Geology): “It’s not always just climate change. Now I will explain what happened.”

Naples, 1 July – “We are once again faced with a dramatic outcome of intense “meteorological” phenomena, harbingers of damage, fear but at least on this occasion, without any victims. And once again it is urgent to try to clarify the concepts, which are often and willingly used in a not entirely correct manner, in a context that finally needs clarity. The environmental outcome of the hydrometeorological event that occurred in the extreme north-western portion of the Italian territory is so complex, determined by a series of exogenous factors, that it cannot be described in a “haste and fury” without first having adequately analyzed different inputs that were harbingers of the disaster that occurred.

Let’s start first of all from the increasingly used concept of meteoric exceptionality: from a first superficial analysis of the historical data, in relation to the portion of the mountain territory affected by the most intense phenomena, it can be deduced that only at the Noasca rain gauge – in Valle Orco – the daily cumulates, hourly and three-hourly can be defined as statistically exceptional. But then why all this disaster, also characterized by notable areal extension? There are more answers, first of all, more important evidence, the lack of sufficiently extensive data from a temporal point of view; almost all the rain gauges analyzed have short-term historical series or detection inhomogeneities in the series itself, so stating that in that precise point the precipitation is exceptional is scientifically incorrect. Therefore it is only possible to state that the 172 mm of rain that fell, of which 127 mm in 3 hours at the Noasca rain gauge, could have return times lasting over a century.

On the other hand, the thermodynamic nature of precipitation was generated by a decidedly complex and rather rare situation; from the forecast models at the local scale, from the analysis of the radio sounding of Novara Cameri and from the observation of the RADAR and satellite animations, an intense convergence was in fact observed in the area affected by the atmospheric events between very humid and unstable air within the jet polar and an advection of very humid and warm currents coming from the south-eastern Mediterranean. The very complex orography, with peaks that are among the highest on the European continent, has favored intense mesoscale ascending motions.

Furthermore, at least in the early afternoon of Saturday, the freezing level was close to 4000 m. with consequent intense rainfall up to 3400-3600 m. above sea level. But how much actually “rained” at altitude, at the head of the valleys hit by the events? Nobody knows, since we do not have any quantitative monitoring tools at altitudes above 2300 m. above sea level except for the very approximate estimate of precipitation at the Plateau Rosa glacier, at the head of the Marmore torrent. Nor can the estimate deriving from the Doppler radar animations be so precise at the local scale. This phenomenon ultimately caused, on the one hand, the complete saturation of the surface layer of soils that were already thin and close to saturation, and, on the other, a more rapid melting of the snowpack that was still abundant in the area at the head of the affected catchment basins.

Since the arrival of the cold front, precipitation occurred in liquid form up to above 3500 m, affecting almost all of the mountain basins and falling on saturated soil due to previous rains and the melting of snow which was still very abundant at high altitudes. Violent torrential floods, determined by almost zero flow times and extensive debris flows, often recurring, have caused extensive and widespread effects in the valleys of the Orco, Soana and Stura di Lanzo torrents and of the five minor watersheds that characterize the Cogne Valley, with a magnitude even higher than some events that occurred in the area, in the summers of the 90s, between 94 and 96″. He stated it Massimiliano FazziniClimatologist, President of the Climate Risk Team of the Italian Society of Environmental Geology.

It’s not always climate change. “But does climate change have anything to do with it or not? The most scientifically correct answer is no! On the one hand, the thermal forcing active for more than half a century on the entire planet determines an ever-increasing quantity of energy available to the complex and chaotic system – sea – atmosphere; it is therefore logical to expect increasingly extreme and temporally frequent atmospheric phenomena. On the other hand, if statistics confirmed that every intense event – be it meteoric, thermal or hydrological – corresponds to a new record or at least one of the “numbers” – Fazzini continued – higher than a historical series of data, then there would no longer be any doubt: we would already be scientifically in a new climate, with more risks for the population. Yes, because man – who has certainly and in various ways caused this imbalance in atmospheric thermodynamics and beyond, must now try to adapt to these new critical situations, trying, once and for all and with the greatest possible common sense, to mitigate this risk that is increasingly present in everyday life. And we believe there is very little time left.”