Description of the Hydrogeological risk
Hydrogeological upheaval is extensively widespread in Italy and represents a major problem.
The geological and geomorphological conformation of our territory, characterized by young orography and mountain ranges still being pushed upwards, are undoubtedly amongst the natural factors laying our territory bare to hydrogeological upheavals.
The hydrogeological risk is also strongly influenced by the action of man. The density of the population, mountain land abandoned, illegal building practices, continual deforestation, use of farming methods with little respect for the environment and failure to keep the hill and mountain sides and water courses in good condition, have all certainly worsened the situation and evidenced the fragility of the Italian territory to a greater degree.
The frequent episodes of hydrogeological upheaval, often causing people to loose their lives and considerable damage to property, has imposed a policy of prevision and prevention no longer centred on repairing damages and providing economic relief as in the past, but focused on identifying the conditions at risk and adopting actions to reduce them.
Legislative measures have imposed placing areas at risk out of bounds, whilst an efficient system of warning and controlling the phenomena entailed setting up emergency plans to effectively coordinate the measures provided by the institutions against hydrogeological events. At the same time, numerous scientific studies are being conducted to analyze the phenomena and to determine the conditions at risk.
Hydrogeologycal risk can be expressed by a formula that links hazard, vulnerability and exposure of people and things:
• hazard expresses the probability that a harmful event of a determined intensity will occur in a zone within a determined period of time.
• vulnerability indicates how much an “environmental component”, such as population density, buildings, services, infrastructures etc., can sustain the effects of the intensity of a given event.
• value at risk or exposure indicates the element to be sustained in a certain event and can be expressed either by the number of human presences or by the value of natural and economical resources on the territory at risk.
Thus, the risk expresses the expected number of victims, of casualties, of damages to buildings, of distruction of economic activities or natural resources following a damaging event.