POPULATION EXPOSED TO FLOODS

    Panel 1
    Data aggiornamento scheda
    Autori

    Martina Bussettini, Barbara Lastoria

    Abstract
    Abstract

    This indicator provides an overview of the population residing in flood-prone areas (population exposed to flood risk) at the national, regional, provincial, and municipal levels. In Italy, the population residing in areas with high hazard/probability is 4.1% of the total national population (2,431,847 people); those exposed to medium hazard/probability are 11.5% (6,818,375 people), while the population in areas with low hazard/probability is 20.6% (12,257,427 people).

    Descrizione

    The indicator provides information on the population exposed to flood risk in Italy. The estimation was made using the following input data: the ISPRA 2020 National Mosaic (created by ISPRA in 2021), which is based on high hydraulic hazard areas (HPH), medium hydraulic hazard areas (MPH), and low hydraulic hazard areas (LPH), delineated by the Basin Authorities and updated to 2020; population data from the 15th National Census by ISTAT (2011); and ISTAT administrative boundaries (2020). The population exposed to flood risk refers to those living in flood-prone areas who may suffer damages because of flooding (deaths, missing people, injuries, evacuations).

    Scopo

    To provide an updated and unified overview of knowledge regarding the population exposed to flood risk at the national, regional, provincial, and municipal levels.

    Rilevanza
    È di portata nazionale oppure applicabile a temi ambientali a livello regionale ma di significato nazionale
    È in grado di descrivere la tendenza senza necessariamente fornire una valutazione della stessa.
    È semplice, facile da interpretare.
    È sensibile ai cambiamenti che si verificano nell'ambiente e/o nelle attività umane
    Fornisce un quadro rappresentativo delle condizioni ambientali, delle pressioni sull'ambiente e delle risposte della società.
    Solidità
    È ben fondato sul piano tecnico e scientifico.
    Presenta affidabilità e attendibilità dei metodi di misurazione e raccolta dei dati
    Comparabilità nel tempo
    Comparabilità nello spazio
    Misurabilità (dati)
    Adeguatamente documentati e di fonte nota
    Facilmente disponibili o resi disponibili a fronte di un ragionevole rapporto costi/benefici
    Un’ “adeguata” copertura spaziale
    Principali riferimenti normativi e obiettivi

    Flood Directive 2007/60/EC
    Legislative Decree 49/2010
    The aim set by the legislation is to provide an updated overview of flood hazard conditions across the entire national territory.

    DPSIR
    Impatto
    Tipologia indicatore
    Descrittivo (A)
    Riferimenti bibliografici

    Lastoria B., Bussettini M., Mariani S., Piva F., Braca G., 2021: Rapporto sulle condizioni di pericolosità da alluvione in Italia e indicatori di rischio associati. Istituto Superiore per la Protezione e la Ricerca Ambientale, Rapporti 353/21, Roma

    Limitazioni

    The indicator provides an overview of the population exposed to flood risk at the national level, detailed down to the municipal scale, based on flood-prone area data updated to 2020 and population data from 2011. It is important to note that flood hazard data are continually updated by the Basin Authorities, and therefore for purposes other than those of this indicator, reference should be made to the information published by these competent authorities.

    Ulteriori azioni

    There is a need to improve the level of spatial coverage of hazard areas especially for high probability scenarios and make better use of information from post-event analyses as part of the Preliminary Risk Assessment.

    Fonte dei dati

    Basin Authority 
    ISTAT (National Institute of Statistics) 
    MiTE (Ministry of Ecological Transition).

    Frequenza di rilevazione dei dati
    Annuale
    Accessibilità dei dati di base

    The 2011 ISTAT Census is available at the link: https://www.istat.it/it/archivio/104317
    The mapping of floodable areas is posted on the District Basin Authorities' websites and on the Ministry of Ecological Transition's National Geoportal: http://www.pcn.minambiente.it/mattm/

    Copertura spaziale

    National, Regional, Provincial, Municipalities

    Copertura temporale

    2020

    Descrizione della metodologia di elaborazione

    To determine the population potentially affected (exposed population) by flood hazard, data from the 15th national population and housing census conducted by ISTAT in 2011 were used, referring to the "Census Sections" territorial base from 2011. The exposed population is the population residing in flood-prone areas, calculated by intersecting in a GIS environment the flood-prone areas layer for each probability scenario with the census section boundaries representing the basic units for the aggregation of ISTAT population data. The population of each section within the flood-prone area is weighted according to the percentage of the section covered by the floodable area. Essentially, assuming no exact population location within the sections, a uniform distribution within each census section is adopted.

    Periodicità di aggiornamento
    Triennale
    Data quality

    The spatial data on flood-prone areas has undergone preliminary geometric and topological checks, and the consistency of the information across the different probability scenarios has been verified. Some areas of the national territory, especially for the high probability/hazard scenario, are not fully covered, or the delineations are either not available or only partially provided. Although the population data is based on the 15th ISTAT Census (2011), it is still sufficiently representative of the population distribution across the national territory.

    Stato
    Non definibile
    Trend
    Non definibile
    Valutazione/descrizione dello stato

    A significant increase in the population was observed due to the expansion of flood-prone areas. This increase is attributed to new studies, modeling, the use of data from past flood events, and future scenarios that account for the effects of climate change.
    Based on the analysis of the population residing in potentially flood-prone areas, the following results were found:

    • The population residing in areas with high hazard/probability (Figure 1) is 4.1% of the total national population (2,431,847 people).
    • The population exposed to medium hazard/probability (Figure 2) is 11.5% (6,818,375 people).
    • The population residing in areas with low hazard/probability (Figure 3) is 20.6% (12,257,427 people).
    Valutazione/descrizione del trend

    Compared to the ISPRA 2017 mosaic, the population residing in areas with high hazard/probability (HPH) from the ISPRA 2020 mosaic increased by 0.6 percentage points. Those exposed to medium hazard/probability (MPH) increased by 1.1 percentage points, while the population in areas with low hazard/probability (LPH) increased by 4.9 percentage points.

    Commenti

    The ISPRA 2020 mosaic, created in 2021 based on data updated to 2020, provides the extent of potentially flood-prone areas for flood probability scenarios defined by Legislative Decree 49/2010. This is based on the delineations produced by the Basin Authorities during the update of flood hazard and risk maps for the second management cycle of the European Directive 2007/60/EC.
    The regions of Veneto, Liguria, Emilia-Romagna, and Tuscany have higher percentages of population exposed to flood risk compared to the national values for all hazard scenarios (Figure 4). The highest percentages of population exposed to flood risk are observed in:

    • High hazard (HPH) scenario in Calabria (12.1%) and Liguria (10.5%).
    • Medium hazard (MPH) scenario in Emilia-Romagna (62.5%).
    • Low hazard (LPH) scenario in Emilia-Romagna (69.4%) and Tuscany (64.3%).

    The province of Ferrara in Emilia-Romagna has a population exposed to flood risk that, in the case of medium (MPH) and low (LPH) hazard scenarios, represents 100% of the resident population. Similar percentages are observed in Veneto, in the province of Rovigo, with regard to the low flood probability (LPH) scenario.

    In Lombardy, the province with the highest percentage of flood-prone area (Mantova) is also the one with the highest percentage of population exposed, but only for the high hazard (HPH) scenario. Meanwhile, Cremona and Sondrio are Lombardy provinces with the highest percentages of population exposed, respectively, for the medium (MPH) and low (LPH) hazard scenarios. In Friuli-Venezia Giulia, the provinces with the highest percentage of population exposed are Gorizia (HPH) and Udine (MPH and LPH). In Tuscany, the provinces with the highest percentages of population exposed are Pistoia (HPH), Pisa (MPH), and Prato (LPH). In Calabria, Crotone not only has the highest percentage of flood-prone areas but also the highest percentage of exposed population (Table 1).

    Allegati
    File
    Titolo

    Table 1: Values of population residing in flood-prone areas in Italian provinces for different flood probability scenarios expressed in absolute terms (no. inhabitants) and percentages (%) of the total population of each province (Prov. Population)

    Fonte

    ISPRA processing of District Basin Authority and Istat data

    Legenda

    ID = Istat code of the province

    Immagine
    Titolo

    Figure 1: Resident population in municipalities in floodable area by High Probability Hazard (HPH) scenario

    Fonte

     ISPRA processing of District Basin Authority and Istat data

    Immagine
    Titolo

    Figure 2: Resident population in municipalities in floodable area by Medium Probability Hazard (MPH) scenario.

    Fonte

    ISPRA processing of District Basin Authority and Istat data

    Immagine
    Titolo

    Figure 3: Resident population in municipalities in floodable area by Low Probability Hazard (LPH) scenario.

    Fonte

    ISPRA elaboration on data from District Basin Authority and Istat

    Immagine
    Titolo

    Figure 4: Percentage of regional population residing in floodable areas for the three flood probability scenarios and values calculated at the national scale

    Fonte

    ISPRA elaboration on data from District Basin Authority and Istat

    English
    Grafici interattivi