Italy

Coastal erosion Italy

The Italian coast

The Italian coastline has a length of about 7500 km, of which about 3950 km (53%) are low or delta coastlines (6). Sand or gravel beaches stretch for approximately 3,240 km, whereas the remaining part are cliffs plunging into the sea and enclosing small pocket beaches. Sicily and Sardinia have 1,623 and 1,897 km of coastline, respectively. Sand or gravel beaches are prevalent on the former (1,117 km) and rock coasts on the latter (1,438 km) (1).

Tidal range is very limited, about 0.3 m along most of the Italian coast. Most Italian shores are exposed to severe storms, with extremes on the western Sardinia coast (annual significant wave height = 7.0 m) (1).

Vulnerabilities

About 1600 km (42%) of the low or delta coastlines (5), including 42% of Italian beaches, are already under erosion (2). Most of the Italian coastal environment suffers from intense and growing urbanization, tourism and industry pressure (6). The highest erosion rates affect the major Italian river deltas, where 10 m/year retreat can be frequently observed (the Arno, Obrone, Volturno and Po rivers). Pocket beaches are also eroding, even if at a lower rate. These narrow beaches are often located in deep bays; the economy of small islands is often linked to them. These beaches cannot shift inland for adaptation to beach erosion, and become progressively narrower, with severe impacts on the local economy. According to a survey carried out in 2008 (3), most pocket beaches longer than 300 m are eroding in Italy.

Factors that induce beach erosion in Italy are dam construction in rivers (thus restricting sediment supply to the coast) and land subsidence of river deltas. The latter is partly due to water extraction for agriculture and industry (8), and gas extraction (9). Long jetties to protect harbours prevented some short coastal segments from eroding but they rapidly induced or increased erosion of down drift sectors (1).

Loss of valuable land due to sea level rise, mainly where combined with isostatic and tectonic movements or anthropogenic subsidence,which will affect economic activities on the coasts, infrastructures and urban settlements, as well as recreational areas, protected natural areas and natural heritage sites (6)... if at the end of the 1980s 15% of the territory was beneath the sea level, in 2020 the lowlands could amount to the 48% of the coastal zone (7).

From the 1950's until the 1970's, industrial dredging removed as much as 600 million tons of sand from the riverbed of the Po river. The mining of sediment along with the trapping of sediment in reservoirs in the basin, and accelerated subsidence (about 3m for the Po delta over the last 100 years (11)) associated with groundwater withdrawal have resulted in localized coastal retreat of hundreds of meters (4).

The lagoon of Venice - Increased salt marsh vulnerability

An adverse effect of the commissioning of the storm surge barrier is a reduction of sediment accumulation on the salt marshes in the Venice Lagoon and hence an increase of the vulnerability of these marshes in view of sea level rise. The tidal range in the Venice lagoon is small. In these microtidal coastal wetlands, everyday tidal inundation hardly provides the sediment necessary for marsh survival. Only storm surges can mobilize sand and silt from adjacent tidal flats and deliver them onto the salt-marsh surface. Storm-driven contribution of sediment accumulation on the marsh surface accounts for more than 70% of the annual accumulation. Since the commissioning of the storm surge barrier, sediment accumulation during storms is much lower than in the past (12).

Adaptation strategies

Artificial coasts (harbours and shore protection structures) represent 7.5% of the entire coastline (10). Hard protection works include seawalls, revetments and rip-raps, detached (and sometimes submerged) breakwaters, (submerged) groins, and island-platforms. Beach nourishments have been performed in all Italian Regions. Beach nourishment proved to be effective in increasing tourist activity (1).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Italy.

1. Pranzini (2013)
2. GNRAC (2006), in: Pranzini (2013)
3. Simeoni et al. (2012), in: Pranzini (2013)
4. Cencini (1998); Sestini (1996), both in: Ericson et al. (2006)
5. GNRAC (2006), in: Ministry for the Environment, Land and Sea of Italy (2010)
6. Ministry for the Environment, Land and Sea of Italy (2010)
7. Antonioli and Silenzi (2009), in: Ministry for the Environment, Land and Sea of Italy (2010)
8. Bartolini et al. (1988), in: Pranzini (2013)
9. Vicinanza et al. (2008), in: Pranzini (2013)
10. Valloni et al. (2003), in: Pranzini (2013)
11. Syvitski et al. (2009); Teatini et al. (2011), both in: IPCC (2014)
12. Tognin et al. (2021)