Réf. Perret & al 2006 - A

Référence bibliographique complète
PERRET, S., STOFFEL, M., & KIENHOLZ, H. Spatial and temporal rockfall activity in a forest stand in the Swiss Prealps - A dendrogeomorphological case study. Geomorphology, 2006, vol 74, 219-231.

Abstract: This study provides an appropriate method for the assessment of spatial and temporal variations in rockfall activity in a given place. Dendrogeomorphological analyses clearly have the potential to produce detailed results on annual or decadal fluctuations of rockfall activity over a long time period, as well as on varying spatial rockfall patterns. In this study, high temperatures are connected with a high rockfall rate, whereas low temperatures result in decreased rockfall activity. On the other hand, precipitation totals showed no significant correlation with the rockfall rate.

Mots-clés
 Rockfall, dendromophology, Swiss PreAlps, frequency, spatial distribution

Organismes / Contact
Department of Geography, University of Berne, Applied Geomorphology and Natural Risks, Hallerstrasse 12, CH-3012 Berne, Switzerland
Department of Geosciences, Geography, University of Fribourg, Groupe de Recherches en Géomorphologie, chemin du Muse´e 4, CH-1700 Fribourg, Switzerland

(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 Rockfalls

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
Swiss Swiss Prealps
Schwarzenberg, 0,3 ha, in the uppermost part of a talus slope (at the foot of a ~400m limestone cliff)
 SE 1250 m asl 1881-2000
1900-2000

(1) - Modifications des paramètres atmosphériques
Reconstitutions  
Observations
Mean annual as well as summer and winter temperatures at Château d'Oex show a highly significant, positive trend betwenn 1910 and 2000.
In contrast, precipitation totals (mean of 3 stations) apparently have no significant trends at all.
Modélisations
  
Hypothèses
  

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

The meteorological data used are the average values for three stations located in a triangle 10 km around the studied site and the Chateau d'Oex data, station located more than 40 km from the studied site.


(2) - Impacts 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) - Impacts du changement climatique sur l'aléa
Reconstitutions
The spatial rockfall distribution changed slightly over the last decades (1941-1970, 1971-2000) and rockfall activity increased considerably over the last century.

In contrast, rockfall magnitude presumably remained on a comparably low level.

Based on 10-year moving averages, a highly significant positive correlation between mean temperatures and the rockfall rate at Schwartzenberg was identified. This means that higher temperatures result in increased rockfall activity.

On the other hand, no correlation with precipitation totals was revealed.
Observations

 
Modélisations
  
Hypothèses
  

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
Rockfall frequency and spatial distribution Temperature and precipitation
Reconstruction of 301 rockfall events (1724-2002) with dendrogeomorphological methods (250 used).

Temporal analyses of rockfall activity : calculation of averaged rockfall rates, trends in rockfall activity and their Pearson's correlations with mean annual or seasonnal temperatures and precipitation totals.

Analyse of the spatial distribution of rockfall by interpolating the number of rockfall injuries by tree.

Each scar on the tree is considered as one rock fall event.

(4) - Remarques générales

 

(5) - Syntèses et préconisations