FLOOD

Flood refers to the temporary flooding of an areas generally not affected by the presence of water.

Traditionally, the phenomenon is triggered by an important meteorological event. In Italian, it takes the name of "flood" when the normal river and torrential regimes are increased to causing an overflow; this can happen, for example, as a result of intense precipitation or the rapid melting of high altitudes glaciers. When flooding is due to sea level rise, in Italian is generally indicated as "inundation". Localized floods can also affect lake areas as a consequence of the increase of the tributary's regime.

In its explosive force, the water drags with it sediments and debris which to remodel the morphology of the surrounding area. This mechanism - at the origins of the creation of large flat areas - becomes particularly risky when it affects densely populated areas. The phenomenon can also concern hilly and mountainous areas, where, depending on the geomorphological situation of the territory, it can generate important landslides.

Since its triggering cause is to be found in the weather conditions, the risk associated with floods falls within the broad category of "meteo-hydrogeological" or, more generally, "water" risks.

According to the most recent "Rapporto ISPRA sulle condizioni di pericolosità alluvionale in Italia e indicatori di rischio associati" (Report on flood hazard conditions in Italy and associated risk indicators - see below), 4.1% of the Italian population lives in areas affe cted by the risk of flooding; 7.8% of our cultural heritage is in the same territories. Even more significant is that about 7.4% of Italian municipalities present high probabilities that this phenomenon impacted on at least 1/5 of their territory.

With about 11.6% of the territory potentially floodable, Emilia-Romagna ranks among the regions with the highest danger of flooding, after Calabria (= 17.1%).

The climate change processes (with a consequent increase in extreme weather events) and not effective policies in guaranteeing a natural defence against floods are increasing the negative effects related to this phenomenon.

Population increased, often linked to the intensive use of the lands, deforestation and overbuilding, as well as poor cleaning of river and torrential beds are the main elements that make floods one of the relevant risks for Italy.

Despite the presence of regulatory references since the early 1900s, the first real approach to the issue of water management in Italy took place following the tragic event that occured in Polesine (Veneto) in 1951: were issued the Law 184/52 ("Piano di indirizzo ai fini di una regolamentazione sistematica delle acque e relazione annuale del Ministero dei Lavori Pubblici") and the Law 11/62 ("Piano attuativo per una regolamentazione sistematica dei corsi d'acqua naturali"). Four years later, the 1966 flood in Florence prompted the government to return to the issue, issuing Law no. 632/67 ("Autorizzazione alle spese per l'esecuzione di lavori di sistemazione e difesa del suolo") and the Presidential Decree n. 616/77, which transferred to the Regions the duty to intervene in the hydrogeological planning of the territory, also with specific environmental protection constraints. The concept of "assessment" in reference to hydrogeological risk came in the regulatory framework with Law no. 183/89 (“Norme per il riordino organizzativo e funzionale della difesa del suolo”), which reorganizing the responsibilities of National Bodies and Local Authorities in the monitoring activities. The same law also established that the Regions have the responsibility to drafting the Piano di assetto idrogeologico (or PAI), a map with the identification of the area subjected to floods risk. The Ministerial Decree of 14 February 1997 ("Direttive tecniche per l'individuazione e la delimitazione da parte delle Regioni a rischio idraulico") the government recognized the subdivision of the territory into areas with high, medium or low probability of flooding. The Legislative Decree no. 152/1999 assigned, once again, to the Regions water management and protection and required to all of them to drafting of the Piano di Tutela delle Acque.

Finally, with Legislative Decree 49/10, the terms "flood", "flood hazard" and "flood risk" were finally introduced into Italian legislation. The Decree transposed and implemented at national level the European Directive 2007/60 / EC (known as the “Direttiva alluvioni”), with the preparation of specific risk maps: the Flood Risk Management Plan (PGRA). The PGRA provides a homogeneous framework at the district level useful for the assessment and management of flood risks, with measures to mitigate the impact on the population, the environment, cultural heritage, economic activities and strategic infrastructures. The Plan has a duration of six years and the second implementation cycle is currently underway.

Did you know?...

although the origin of the floods is to be found in uncontrolled and disruptive weather phenomena, their effects have not always been considered harmful. This is the case of the seasonal flooding of the Nile River, which making productive the Egypt arid lands.

Furthermore, in history there have also been artificial floods, with the aim of slowing the advance of enemy armies (China 1938) or to create artificial lakes for the production of hydroelectric energy (Val Garfagnana, Tuscany 1947). On 9 October 1963, following a substantial landslide, a disruptive flood engulfed the Vajont valley (Belluno, Italy): the water overflowed from a hydroelectric dam and tragically poured into the valley below.