Descrizione 1
Stefano Calcaterra, Piera Gambino, Daniela Niceforo
The indicator analyzes the distribution of large and small dams in relation to the seismic classification of the national territory (Map of seismic zones OPCM March 20, 2003, n. 3274 and subsequent integrations), the Landslide Index of the IFFI Project (Italian Landslide Inventory), and the distribution of landslide-prone areas. For the year 2024, the indicator shows that the water surface of artificial and heavily modified natural lakes (the water perimeter for large and small dams) in areas with a null Landslide Index (IF) constitutes 71.6%, while only 1.8% falls in areas with a higher IF (IF>30). In terms of seismic activity, 7.4% of large dams and 2.2% of small dams are are located in the most dangerous area (seismic zone 1), while 20.6% and 11.9%, respectively, are in the least dangerous area (seismic zone 4). Due to incomplete data on the distribution of small reservoirs at the national level, the result is considered partial.
Reservoirs are water bodies, either artificial or naturally occurring but heavily modified by human action, located in areas constantly subjected to geological-hydraulic changes, even over short periods of time. The indicator provides information on the distribution of large and small dams (Law of October 21, 1994, n. 584) and their associated reservoirs in relation to certain geological hazard conditions: seismic hazard, Landslide Index, and the distribution of landslides recorded by the Italian Landslide Inventory (IFFI Project). Artificial reservoirs are classified as large dams, under the responsibility of the DG Dighe (Ministry of Infrastructures and Trasport- MIT, Directorate-General for Dams and Water Infrastructure, and data provider), and small dams/hilltop ponds/small reservoirs, which fall under the responsibility of the regions/autonomous provinces. These regions are also responsible for preparing the complete census, in compliance with Directive 2000/60/EC concerning water quality, and in some cases, they define the “environmental risk factor” associated with these reservoirs. Large dams include barriers or weirs with a height greater than 15 meters or that create a reservoir volume exceeding 1,000,000 cubic meters. Barriers with smaller dimensions and volumes are classified as small reservoirs. For the geolocated dams, the indicator provides the statistical result of the intersection with the national seismic classification, updated in 2023 by the Civil Protection Department (https://rischi.protezionecivile.gov.it/it/sismico/attivita/classificazione-sismica/). Furthermore, in cases where the shoreline coordinates of the water bodies associated with large and small dams is available, the distribution of these bodies is analyzed in relation to the Landslide Index and the bodies of landslides, provided by the IFFI Project (IdroGEO - IFFI Landslide Inventory isprambiente.it), within a 200-meter buffer.
Identify the distribution of artificial reservoirs or heavily modified natural reservoirs on the national territory in relation to the current seismic classification (OPCM March 20, 2003, n. 3274 and subsequent integrations), to the landslide census of the IFFI Project, and to the derived parameters (Landslide Index-IF). This indicator can support the assessment of environmental risks that may arise due to natural phenomena or those induced by human activities, thereby contributing to to the protection of the environment, natural resources, and the safeguarding of human life.
The Law of October 21, 1994, No. 584, along with the subsequent Circular of the Ministy of Public Works (Circ. Min. LL.PP. 482/199), and Presidential Decree (D,P.R.) of November 1, 1959, No. 1363 (of which only the first part remains in force, containing general provisions for design, construction, and operation) constitute the main technical and administrative legal provisions concerning the classification of large dams and small reservoirs, as well as the definition of responsibilities in this field.
Additional regulations currently in force ( Circular of the Ministry of Public Works, August 28, 1986, No 1125; Circular of the Ministry of Public Works of December 4, 1987, No 352; Law of October 21, 1994, No. 584; Circular of Presidency of the Council of Ministers, December 13, 1995, n. DSTN/2/22806; Ministerial Decree of Public Works, March 24, 1982; Law No 183/89; Legislative Decree 507/94 converted into Law 584/94; Law 139/04; Legislative Decree No 152/2006; Ministerial Decree of January 14, 2008; Ministerial Decree of Infrastructure and Transport , June 26, 2014) also define urgent measures for the safety of large dams in response to changes in national legislation on seismic risk (Law 64/1974, Law 139/2004, OPCM 3519 of April 28, 2006) and provide operational guidelines for organizing and managing of hydrogeological and hydraulic criticality conditions (DPCM February 27, 2004, Directive of the Presidency of the Council of Ministers, July 8, 2014).
With Legislative Decree No 94 of May 14, 2024, titled “Regulation governing the the approval process for projects and control and the superviosion of the construction and operation of retention structures (dams and weirs) ”interventions on existing dams and supervision of water derivation works are regulated, also serving as a reference point for the regional authorities, which may update the regulations applicable to "small dams” (https://www.mit.gov.it/comunicazione/news/dighe-pubblicato-gazzetta-il-nuovo-regolamento).
In the field of seismic safety, several circulars have been issued (DG Dighe Circular of September 27, 2017, No 21530; DG Dighe Circular n. 25157 of November 8, 2017; DG Dighe Circular of March 18, 2019, n. 6660, DG Dighe Circular of July 3, 2019, No 16790). These documents provide guidelines on methodologies and requirements for assessing seismic hazard at dam sites and update extraordinary inspections procedures following seismic events.
Certain regional regulations (Tuscany Regional Law No 43 of July 28, 2014, n.43; Piedmont Regional Law No 25 of October 6, 2003, and related Regional Regulations: No 12/R of November 9, 2004, and No 1/R of January 29, 2008; Abruzzo Regional Law No 18 of June 27, 2013; Aosta Valley Regional Law No 13 March, 2010 and Regional Government Resolution No 2073 of July 30, 2010; Sardinia Regional Law No 12 of October 31, 2007) define the risk categories for reservoirs, also based on the methodology outlined in the note from the by the Presidency of the Council of Ministers, Department of Civil Protection,, Forecasting and Prevention Service, on July 31, 1991 (No prev. 2554 gen. 804 “Method for determining the potential risk of existing small reservoirs").
The Technical Standards for Construction (Ministerial Decree of Infrastructure and Transport, January 17, 2018) (Annex A) establish that the reference seismic action for the design of a structure must be defined based on the seismic hazard values proposed by the Italian National Institute of Geophysics and Volcanology (INGV) within the Project S1 ( Continuation of Assistance to the Civil Protection Department for the completion and management of the seismic hazard map as required by Ordinance PCM 3274 of March 20, 2003).
Lastly, the "Method for determining the potential risk of existing small reservoirs," proposed by the Civil Protection Department (Presidency of the Council of Ministers - Department of Civil Protection Note of July 30, 1991, No prev. 2554 gen. 804), provides the definition of the Global Risk Factor R of a reservoir as the product of three factors (R=AxBxC), where:
- Factor A (Environmental Risk Assessment), evaluated in relation to: seismic risk, landslide risk, overflow risk, risk related to operation methods (e.g. drainage cycle);
- Factor B (Structural Risk Assessment), evaluated in relation to: structural integrity /safety, watertightness efficiency, foundation quality, drainage functionality, operational reliability;
- Factor C (Potential Risk Assessment), assessed in relation to: population density and presence of significant settlements (for civil protection purposes, population exposure, and asset value).
There are no regulatory targets established concerning this specific risk indicator
Descrizione 2
Castelli S., Cassese E., Frosio N., Magno A., Ropele P., Sainati F., Valgoi P. and Masera A. (2010) Small Dams in Italy. Proceedings of the 8th ICOLD European Club Symposium Dam Safety-Sustainability in a Changing Environment 22nd-23rd September 2010 Innsbruck, Austria; Giornata di studio sui temi: I comportamenti delle dighe italiane in occasione di terremoti storici. La situazione delle piccole dighe in Calabria (Prof. G. Principato). Roma 28 marzo 2017; IFFI-inventario dei fenomeni franosi: https://www.progettoiffi.isprambiente.it/; ITCOLD-Comitato Italiano Grandi Dighe, Le Piccole Dighe in Italia. Rapporto GdL, 2017; Provincia di Bolzano; Provincia di Macerata (Genio Civile); Regione Abruzzo: S.I.T. regione Abruzzo http://geoportale.regione.abruzzo.it/Cartanet; Regione Campania www.difesa.suolo.regione.campania.it; Regione Friuli Venezia Giulia http://irdat.regione.fvg.it/WebGIS; Regione Emilia-Romagna; Regione Lazio - Direzione Risorse Idriche e Difesa del Suolo; Regione Lombardia; Regione Marche: provincia di Macerata (Genio Civile); Regione Umbria: Provincia di Terni http://sia.umbriaterritorio.it; Regione Valle d'Aosta; Regione Veneto; Regione Toscana https://geoportale.lamma.rete.toscana.it/difesa_suolo/#/viewer/openlayers/372; Regione Sardegna http://www.regione.sardegna.it/; ARPA Sicilia; Regione Sicilia https://www.arpa.sicilia.it/temi-ambientali/laghi-e-invasi/, http://pti.regione.sicilia.it/portal/page/portal/PIR_PORTALE/PIR_LaStrutturaRegionale/PIR_AssEnergia/PIR_Dipartimentodellacquaedeirifiuti/PIR_PianoGestioneDistrettoIdrograficoSicilia; Ministero delle Infrastrutture e dei Trasporti-Direzione generale per le dighe e le infrastrutture idriche https://dgdighe.mit.gov.it/; RemTech EXPO ESONDA-Convegno, “Aspetti Ambientali delle dighe”, Ferrara 20 settembre 2024.
The analysis of exposure to seismic and geological-hydraulic hazards of artificial reservoirs can only be conducted with georeferencing of the dam structures and their associated reservoirs. To date, information regarding dam structures is complete only for large dams, as the national data is provided by the Ministry of Infrastructure and Transport - Directorate General for Dams and Hydraulic Infrastructures, in contrast, for small dams, the data is partial for some regions and entirely absent for others.
On the other hand, the perimeter of water bodies is partial for both types of reservoirs. Lastly, not all regions have published or implemented the classification of risk for small reservoirs, which is therefore available for some regions of central-northern Italy.
Complete information regarding georeferencing of small reservoirs and artificial bodies of water at the regional/national scale and risk classification should be acquired.
Qualificazione dati
For large dams: General Directorate for Dams and Water Infrastructure (Ministry of Infrastructure and Transport). For small reservoirs, data are provided by the autonomous regions/provinces, by the agencies entrusted with the census or management, or made public on the relevant web portals. Additional geographic information on bodies of water related to both artificial and heavily modified dams is contained in the Data Base prepared by the regions for the Water Framework Directive (shape file of Surface Water Bodies - Lakes - Reporting WISE2016). Information regarding landslides is extracted from ISPRA's IFFI Project while seismic classification is published by the Department of Civil Protection-Presidency of the Council of Ministers.
National for large dams, Regional (19/20) for small reservoirs.
2023 (National Seismic Classification Map DPC-Department of Civil Protection), 2024
Qualificazione indicatore
The vector data related to large and small dams are analyzed, processed, and queried through a geographic interface tool with the informational layers of the landslide susceptibility and seismicity across the national territory. The results obtained are expressed in statistical terms.
Currently, the indicator highlights that the percentage of portions of artificial or naturally heavily modified water body, classified as both large and small dams, located in areas with the highest Landslide Index (IF>30) is approximately 2%, while the highest percentage (72%) falls within areas with a null IF. Regarding seismicity, both large and small dams exhibit the highest concentration in with medium-low seismicity areas (zone 3) with values of 35% and 59%, respectively. It is not possible to provide an assessment of the current status due to the incompleteness of the information regarding the extent of the water surfaces necessary for defining landslide risk exposure for all types of reservoirs.
Compared to 2022, the information regarding the geolocation of dams and water bodies has increased. The dataset is still incomplete for some regions, for which only the information regarding large dams is available.
Dati
Tabella 1: Percentuale di specchi d’acqua interessati da dissesti (frane, DGPV e aree a franosità diffusa) in un buffer di 200 m (2024)
Elaborazione ISPRA su dati regionali
Figura 1: Distribuzione dei centroidi delle grandi dighe di competenza statale e delle piccole dighe regionali rispetto alle zone sismiche ai sensi dell’OPCM 3274/03 e successivo Opcm n. 3519 del 28 aprile 2006 (Classificazione sismica aggiornata a marzo 2023)
Elaborazione ISPRA su dati del MIT-DG e dati regionali
Figura 2: Distribuzione dei corpi idrici relativi alle Grandi e Piccole Dighe rispetto all’Indice di Franosità (IF) del Progetto IFFI (2024)
Elaborazione ISPRA su dati del Progetto IFFI (Inventario dei Fenomeni Franosi in Italia), del Reporting WISE2016 e di dati regionali
Figura 3: Percentuale di Piccole Dighe per classe di rischio (2024)
Elaborazione ISPRA su dati regionali
The distribution of dams relative to seismic zones as defined by OPCM 3274/03 is shown in Figure 1, where it is highlighted that the highest percentage of large dams (34.8%) falls in seismic zone 3 (medium-low shocks ), while for the zones with the highest and lowest seismicity (seismic zones 1 and 4), the percentages drop to 7.4% and 20.6%, respectively. For small dams, the analysis covered 19 regions where it is possible to identify, with relative certainty, artificial or heavily modified natural reservoirs. The percentages are 2.2% for the most dangerous zone (zone 1) and 11.9% for zone 4, while, like large dams, the highest value is seen in zone 3 (58.6%).
The analysis of the distribution of reservoirs according to the Landslide Index (IF) from the IFFI Project (an index calculated on a 1 km grid as the percentage ratio of landslide area to total cell surface) was analyzed using the perimeter of water bodies provided by the Water Framework Directive (WISE2016 Reporting) and regional datasets (Figure 2). Each water surface is discretized into 1 km² grids cells to which a percentage IF value is assigned. The highest percentage of water surfaces (71.6%), related to both large and small reservoirs, falls in areas with no landslides, while only 1.9% is located in areas with an IF greater than 30%. Specifically, for the available dataset on large dams (330 water surfaces), only 2%, located in the regions of Piedmont, Lombardy, Trentino-Alto Adige, Friuli Venezia Giulia, and Tuscany, have corresponding water bodies entirely located in areas with a landslide index >30. In all other cases, it concerns only portions, and in only few cases it does reach 90% of the lake's surface area. Table 1 shows the results of a specific analysis regarding the distribution of landslides in a 200-meter buffer around reservoirs, conducted in 10 regions for which georeferencing data for large dams' and small reservoirs' water bodies is available. These regions include Piedmont, Veneto, Friuli-Venezia Giulia, Liguria, Umbria, Abruzzo, and Sardinia, with the addition of Lombardy, Emilia Romagna, and Basilicata for 2024. The highest percentage of reservoirs located in areas with landslides in a 200-meter buffer around water surfaces is observed in the Umbria region, at 71.4%, and drops to 2% for Veneto. Lastly, Figure 3 shows the percentage distribution of reservoirs in the risk classes defined by the regions of Aosta Valley, Piedmont, and Abruzzo, and the provinces of Arezzo and Livorno. These classes, proposed by the Note P.C.M.-Dip. Prot. Civile of July 30, 1991, are the result of hydraulic studies conducted downstream of the dams, assessments of structural maintenance, and the vulnerability analysis of the reservoir to the instability. The Province of Livorno shows the highest percentage of reservoirs with high risk (80%).