Geological hazards in Catalonia
http://www.icgc.cat
> Engineering geology > General information on geological risks > Geological hazards in Catalonia
General information on geological risks
Basic knowledge
Basic concepts of
geological hazards
Geological hazards
in Catalonia
Phenomena generated by
external and internal
geodynamics
Phenomena related
to external
geodynamics
Inventory of geological
phenomena in
documentary sources
Self-protection
advice
How to act when faced with
dangerous phenomena
such as slope movements
Geological hazards
In Catalonia, the main phenomena that have and could occur in the future are those generated by external
geodynamics, such as floods, slides, falls, torrential flows, collapses and avalanches, and by internal geodynamics,
such as earthquakes.
The main risk, with most impact in Catalonia, is flooding. This could affect the entire region, but mainly affects two
areas: the Pyrenees and the Pyrenean foothills, and the coast and the pre-coastal area of Catalonia. During the 20th
century the most important, due to their catastrophic effect, occurred in October 1907, mainly affecting the basins of
the Ebre and Segre; October 1940, in the Ter and Fluvià basins; September 1962, in the regions of Vallès, Baix
Llobregat and Maresme; November 1982 affecting the Pyrenean regions, and June 2000 on the mountain of Montserrat
and its surrounding area.
NII bridge by Esparreguera after the torrential rains of June 2000
For more images see Regio7.cat
Slides mainly occur in mountain areas with high rainfall where there is rock and soil with low resistance under certain
humidity conditions. One of the most important slides recorded occurred in Puigcercós (Pallars Jussà) in 1881. A
whole village had to be evacuated and its inhabitants moved to another area in the region. Slides frequently coincide
with significant rainy periods, such as those in 1907 and 1982.
Evidence of the slide at Puigcercós
The most significant falls, and those with a large media repercussion, over the last few years occurred on the
mountain of Montserrat. These can be destructive phenomena, due to both their size and high speed, and will continue
to occur whilst there are cliffs and steep slopes from which fragments of unstable rock and soil can detach.
Damage to the Montserrat rack railway caused by the fall on 28 December 2008
Over the last few years torrential flow dynamics related to intense rainfall have caused significant material damage.
Of note are the episodes of June 2000 on Montserrat, August 2008 in the Runer river (on the Andorra-Catalonia border)
and September 2008 and July 2010 at Port-Ainé.
Damage to the ski resort access road in Port-Ainé after the rains of 23 July 2010
Collapses occur due to limestone, salts and carbonate formations naturally dissolving. In the case of carbonate
formations, the evolution is very slow and often barely perceptible. On the other hand the evolution of salts is fast. In
Catalonia there are examples of collapses in the massif of the Garraf, the Banyoles lake basin and the Vall Salina
(Salt Valley) of Cardona. When we refer to collapses we talk of sinkholes, when the phenomenon is sudden and fast,
or subsidence, when it is slow and progressive. Human activity can also create collapses, such as those related to
mining for potassium salts. This is the case of Sallent, where the subsidence of the Estació neighbourhood is
occurring, leading to the evacuation of more than 110 people in 2009.
Situation of the Estació neighbourhood in Sallent, October 2010, where housing has been demolished in the area of
subsidence.
4% of Catalonia is susceptible to avalanches (1,320 km2), which corresponds to 36% of the area of the Pyrenees. By
region, those most affected are: Vall d’Aran, Alta Ribagorça, Pallars Sobirà, Ripollès, Cerdanya, Pallars Jussà, Alt
Urgell, Berguedà and Solsonès. The first three are the areas where the risk to buildings and transport routes is highest.
Historically, avalanches have caused the partial or total destruction of some villages in the Pyrenees, such as Gessa
(15th century, Vall d’Aran), Senet (1632, Alta Ribagorça), Sant Joan de Toran (1855, Vall d’Aran). During the 20th
century of note are the episodes in 1915, 1937, 1972 and 1996.
Avalanche in Pales de Ruda, 31 January 2005.
With regard to earthquakes, Catalonia has two areas of seismic activity: the Pyrenees and the Mediterranean
System. The main seismic activity can be found in the Pyrenees. In the past there have been destructive earthquakes
in Catalonia; 1373 in Alta Ribagorça and in 1427-1428 in the regions of Ripollès and Garrotxa. At the beginning of the
20th century, in 1923, there was an earthquake that measured 5.5 on the Richter scale, which caused damage in the
Vall d’Aran. More recently, in the eastern area of the Pyrenees, in 1996, the largest earthquake recorded for the period,
at 5.2 on the Richter scale, occurred in the region of Fenolledes (France). Earthquakes recorded in the Mediterranean
area have been smaller than those in the Pyrenees, reaching values of over 4, in 1987 and 1995 off the coast of
Tarragona; in 1991 off the Garraf coast and, in 1994, off the Maresme coast, without causing any damage.
Map of earthquakes that have caused damage in Catalonia.
08/04/14 12:36:16