Flash flood in Versilia and Garfagnana (Apuan Alps, Tuscany, Italy)
on 19 June 1996
by: J. Kerkmann (EUMETSAT)
Picture of the Versilia river on 20 June 1996
Meteosat-5 (infrared channel)
19 June 1996 (12:00 UTC)
Flash floods are quite common in Tuscany, Italy. On the basis of known data about the disastrous events that occurred
between 1918 and 1990, 86 disastrous rainfalls events were identified in Tuscany that have caused 582 flood events
along 170 different rivers affecting 375 places located in a significant number of communes (67% of the total number of
communes). The temporal distribution of such disastrous events indicated that most occur in the autumn when there are
frequent atmospheric disturbances, mainly of Atlantic origin, (including cyclones generated in the Gulf of Genova) and
because of the peculiar influence of the Mediterranean on the Tuscan climate.
The figure below shows peaks in the frequency distribution of disastrous 24-hour rainfall events in Northern Italy (this
example is for the Dolomites) lie in the months of April and November, which also happen to be the months of
maximum cyclonic activity in the Gulf of Genova. On the other hand, the peak occurrence of strong 15-minutes rainfall
events lies in the summer months when severe convection triggered by orography and diabatic heating is dominant.
Monthly frequency distribution in % of strong
precipitation events in Northern Italy (Dolomites)
One of the strongest flash floods in the Apuan Alps (Tuscany) occurred on 19 June 1996 when more than 400 mm of
rain fell in less than six hours (total precipitation at Pomezzana 470 mm, see figure below), causing 13 known deaths,
one missing person and immense destruction. The village of Cardoso was nearly totally destroyed by the flash flood that
rushed through the Versilia valley. The maximum rainfall intensity was about 88 mm in 30 minutes, which is one of the
highest rainfall intensities ever recorded in Italy. For comparison, a table with extreme rainfall intensities around the
world is given below.
Interval
(minutes)
1
8
42
100
1440 (1 day)
44640 (1 month)
525600 (1 year)
Precipitation
(mm)
31.2
126.0
304.8
600
1870
9300
26461
Place and Date
Unionville, USA, 1 July 1956
Füssen, Germany, 25 May 1920
Holt, USA, 22 June 1947
Schaueregg, Austria
Cilaos, La Reunion, 15/16 March 1952
Cherrapunji, India, July 1861
Cherrapunji, India, Aug 1860 - July 1861
Extreme precipitation events in the world (from Liljequist and Cehak, 1984)
The synoptic situation in the morning hours of 19 June 1996 was characterised by a low pressure system over Sweden
with a frontal disturbance extending from Finland to the Alps (see above satellite loop). The upper-level flow over Italy
was from the north-west with a weak low-level depression over the Gulf of Genova. Low-level winds over large parts
of Northern Italy were from south to south-west. The explosive development in the morning hours in the Apuan Alps
was probably a combination of a favourable synoptic situation (the so-called "loaded gun" with relatively warm and
moist air at low levels, overrun by cool, dry air at medium to high levels) and orographic lifting (uplift of the low-level
flow coming from the south-west along the steep Apuan Alps). The satellite movie above clearly shows a stationary
convective system over the Apuan Alps that is being regenerated several times in the period between 01:30 and 16:00
UTC, which explains the high rainfall. A similar explosive development can be observed about 12 hours later in Eastern
Italy and Slovenia, producing large hail and locally more than 100 mm rainfall.
Precipitation map for the area of the Apuan Alps on 19 June 1996
(from Mazzoni et al., 1997)
Half-hourly and accumulated precipitation at Pomezzana on 19 June 1996
(from Mazzoni et al., 1997, data from "Ufficio Idrografico e Mareografico Nazionale", Italy)
Disaster in the Apuan Alps, 19 June 1996
Victims
Thirteen fatalities and one missing person.
Buildings
More than 3.500 homes involved in the communes of Pietrasanta Stazzema, Seravezza, Forte dei Marmi, and about
4.000 homes damaged. Hundreds of industrial, commercial and agricultural buildings damaged.
Communication and railway lines
Tenth of a kilometre of provincial streets destroyed. The "Aurelia" highway closed to the traffic for two weeks. The
railway line from Genova to Roma blocked for about 10 days.
Isolated or destroyed villages
Cardoso and parts of Stazzema semi-destroyed. Several mountain villages remained isolated for many days (e.g.
Farnocchia, Pruno, Volegno and Pomezzana).
Literature:
Mazzoni, G.B., Olivieri, M. and M. Ratti, 1997: L'evento alluvionale del 19 Giugno 1996 in Alta Versilia. Nimbus,
Società Meteorologica Subalpina, Torino (Italy), 13-14, 136-140.
Liljequist, G.H. and K. Cehak, 1984: Allgemeine Meteorologie. Vieweg Verlag, Braunschweig, Germany, 396 pp