Réf. Soldati & al 2004 - A

Référence bibliographique complète

SOLDATI M., CORSINI A., PASUTO A. Landslides and climate change in the Italian Dolomites since the Late glacial. Catena, 2004, vol. 55, 141–161.


Abstract : The paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the Italian Dolomites since the Late glacial. By analysing the dates from the two study areas, it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the Late glacial and the Holocene and between the Atlantic and the Subboreal, and to compare the results with those derived from other European regions. The types and causes of landslides taking place in these two periods were substantially different, reflecting the different morphoclimatic conditions that existed in the two areas when these mass movements were triggered. Finally, notwithstanding the importance of non-climatic causes, such as geological – structural factors and possible human influences, it is concluded that many of the dated landslides can be considered as indicators of climatic change.

Mots-clés
Landslide, climate change, late glacial, holocene, Italian Dolomites

Organismes / Contact
Dipartimento di Scienze della Terra, Universita degli Studi di Modena e Reggio Emilia, Largo S. Eufemia 19, 41100 Modena, Italy. soldati@unimore.it
Istituto di Ricerca per la Protezione Idrogeologica (IRPI)-C.N.R., Corso Stati Uniti 4, 35127 Padova, Italy

(1) - Paramètre(s) atmosphérique(s) modifié(s)
(2) - Elément(s) du milieu impacté(s)
(3) - Type(s) d'aléa impacté(s)
(3) - Sous-type(s) d'aléa
Temperature
Precipitation
  Mass movements Landslides

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
Italy Dolomites (eastern Italian Alps) Cortina d’Ampezzo (province of Belluno) and Alta Badia (Upper Badia Valley, province of Bolzano)     Holocene

(1) - Modifications des paramètres atmosphériques
Reconstitutions
Following the stadial-interstadial phases occurring between 22,000 and 11,500 cal BP (which led to the final withdrawal of the Late glacial stadial valley glaciers between some 14,000 and 11,000 cal BP) temperature was progressively rising towards temperate conditions.
Starting from about 11,000 cal BP, a subsequent increase of precipitation took place, followed by a climatic optimum between 9000 and 5800 cal BP. Finally, around 2700 cal BP (at the Subboreal – Sub-Atlantic boundary), a sudden climatic worsening occurred, with a considerable increase of precipitation and wide­spread glacier advancement.
Observations
 
Modélisations
 
Hypothèses
 

Informations complémentaires (données utilisées, méthode, scénarios, etc.)
Although paleoclimatic studies in Cortina d’Ampezzo and Alta Badia are still lacking, the chronological sequence and trend of the climatic changes induced by global events during this period may be considered similar to those reconstructed by various authors in northern and central European areas as well as in other Alpine areas. For the purpose of this research, the synthetic climatic frames presented mainly by Goudie (1992) and Orombelli and Ravazzi (1996) have been considered.

(2) - Effets du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

Sensibilité du milieu à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

(3) - Effets du changement climatique sur l'aléa
Reconstitutions
In the Cortina d’Ampezzo area, the most ancient landslide event there involved large rock slides, which affected the dolomitic slopes following the withdrawal of glaciers after the Last Glacial Maximum (LGM), and also slides and flows mainly occurring in pelitic materials of the valley floors (from 13,000 to 10,000 cal BP). A later series of flows occurred between 5500 and 2500 cal BP.

In the Upper Badia Valley (Alta Badia), the most ancient events go back to 10,000 and 9000 cal BP, and correspond with earth flows that followed vast rotational slides affecting the bedrock up to a depth of about 50 m. More recent earth flows, involving more modest amounts of material, took place between 6500 and 2300 cal BP. In these mid-Holocene periods, as well as at present, movements are believed to have occurred mainly as episodic shallower earth flows that mobilised, in part or totally, landslide material previously accumulated.

The first phase of marked slope instability is observed in the Preboreal and Boreal (about 11,500 – 8500 cal BP), and includes, on the one hand, large translational rock slides, which affected the dolomite slopes following the withdrawal of the Würm glaciers and the consequent decompression of slopes, and on the other hand, complex movements (rotational slides and flows) that affected the underlying pelitic formations and was probably favoured by high groundwater levels resulting from an increase of precipitation and/or permafrost melt down.

A second concentration of landslide events is found during the Subboreal (about 5800 – 2000 cal BP), when slope processes, mainly rotational slides and/or flows, took place in both the study areas. These slides may be considered reactivations of older events linked to the phase of precipitation increase that has been documented in several European regions during this mid-Holocene period. On the other hand, during the Little Ice Age, the scarce number of landslides dated in the study areas does not enable an increased frequency of landsliding to be detected.

The recurrence in time of landslide activity since the Late glacial was certainly also influenced by non-climatic factors but many landslide events previously described might be considered as indicators of climatic changes. For this purpose, the comparison with bibliographic data relating to other European mountain areas is significant. In fact, concentrations of landslides during periods similar to those of the areas studied were reported in various European regions, such as the United Kingdom, the Iberian Peninsula and Eastern Europe. Investigations carried out in the Swiss Alps (Lateltin et al., 1997) pinpointed a concentration of events in the Preboreal, between 11,200 and 10,000 cal BP, in the Subboreal, between 5900 and 3500 cal BP, and in the lower Sub-Atlantic, between 2600 and 1700 cal BP. To this, an intensification of events occurring during the past 500 years should be added.

Some agreement between the temporal distribution of landslides in various European regions and in the Italian Dolomites are evident. Indeed, all the cases previously described fall more or less precisely into the two periods of greater activity thus identified. In a European perspective, the Preboreal period coincides with the oldest period of frequent postglacial slope movements in Europe that was identified by various authors. On the other hand, a second period of occurrence corresponds to an increase of precipitation reported in literature. However, the hypothesis of a direct influence of this climate change on landslides, partially confirmed by the European case studies above mentioned, still needs further verification.
Observations
 
Modélisations
 
Hypothèses
 

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
Frequency of landslides
Precipitaion?

Research carried out in the past few years has led to a typological and chronological characterisation of the various landslides found in Alta Badia and Cortina d’Ampezzo areas. During these investigations, numerous tree trunks and wood remnants were found along erosion scarps or during excavations and borings together with soils, sediments rich in organic matter and peat that had been buried by landslide deposits. Moreover, samples of wood remnants and peat were found within lacustrine deposits that in turn resulted from landslide damming of rivers. Conventional radiocarbon dating of these remnants allowed the chronological reconstruction of the mass wasting processes occurring in the two study areas.

In the Cortina d’Ampezzo area, over 30 landslides differing in type, size and degree of activity were identified and mapped (Panizza, 1990; Panizza et al., 1996; Pasuto et al., 1997; Soldati, 1999). Detailed geomorphological investigations and radiocarbon dating allowed the valley’s geomorphological evolution to be outlined.

As in the former study area, also in Alta Badia, many landslides were identified and mapped in recent years. On the basis of 40 radiocarbon age determinations, some postglacial phases of activity were determined in 13 of them.

An effort has been made to assess which of the numerous radiocarbon dates collected in the study areas are related to events of a type or magnitude that can be indicators of Holocene climatic changes. The degree of paleoclimatic significance of each of the dated landslides has been assessed on the basis of the following criteria:
geomorphological context in which the landslide has taken place;
type of landslide;
material involved in the landslide;
size/magnitude of the landslide;
type of dated material;
depth at which the dated material has been found (either from excavations or drillings);
borehole stratigraphy when dated material is collected from drill holes.


(4) - Remarques générales

 


(5) - Syntèses et préconisations
 

Références citées :

Abele, G., 1997. Influence of glacier and climatic variation on rockslide activity in the Alps. Paläoklimaforschung-Palaeoclimate Research 19, 1 – 6.

Alexandrowicz, S.W., 1997. Holocene dated landslides in the Polish Carpathians. Paläoklimaforschung-Palaeoclimate Research 19, 75 – 83.

Corsini, A., Pasuto, A., Soldati, M., 2000. Landslides and climate change in the Alps since the Late-glacial: evidence of case studies in the Dolomites (Italy). In: Bromhead, E., Nixon, N., Ibsen, M.-L. (Eds.), Landslides in Research, Theory and Practice. Thomas Telford Publishing, London, pp. 329 – 334. - [Fiche biblio]

Corsini, A., Marchetti, M., Soldati, M., 2001. Holocene slope dynamics in the area of Corvara in Badia (Dolomites, Italy): chronology and paleoclimatic significance of some landslides. Geografia Fisicae Dinamica Quaternaria 24, 127 – 139.

González Díez, A., Salas, L., Díaz de Terán, J.R., Cendrero, A., 1996. Late Quaternary climate changes and mass movement frequency and magnitude in the Cantabrian region, Spain. Geomorphology 15, 291 – 309.

Goudie, A., 1992. Environmental Change, 3rd ed. Oxford Univ. Press, Oxford. 329 pp.

Ibsen, M.-L., Brunsden, D., 1997. Mass movement and climatic variation on the south coast of Great Britain. Paläoklimaforschung-Palaeoclimate Research 19, 171 – 182.

Lateltin, O., Beer, C., Raetzo, H., Caron, C., 1997. Landslides in Flysch terranes of Switzerland: causal factors and climate change. Eclogae geologicae Helvetiae 90, 401 – 406. - [Fiche biblio]

Matthews, J.A., Brunsden, D., Frenzel, B., Gla¨ser, B., Weiß, M.M. (Eds.), 1997. Rapid Mass Movement as a Source of Climatic Evidence for the Holocene. Paläoklimaforschung-Palaeoclimate Research, vol. 19. Gustav Fischer Verlag, Stuttgart. 444 pp.

Panizza, M., Pasuto, A., Silvano, S., Soldati, M., 1996. Temporal occurrence and activity of landslides in the area of Cortina d’Ampezzo (Dolomites Italy). Geomorphology 15, 311– 326.

Panizza, M., Pasuto, A., Silvano, S., Soldati, M., 1997. Landsliding during the Holocene in the Cortina d’Am-pezzo Region, Italian Dolomites. Paläoklimaforschung-Palaeoclimate Research 19, 17 – 31.

Soldati, M., 1999. Landslide hazard investigations in the Dolomites (Italy): the case study of Cortina d’Ampezzo. In: Casale, R., Margottini, C. (Eds.), Floods and Landslides: Integrated Risk Assessment. Springer-Verlag, Berlin, pp. 281 – 294.