geographia - Studia

O. POP, J. - C. THOURET, V. SURDEANU
The morphometrical parameters of the three landslides analyzed
Table 1
Morphometrical parameters
Saut de
la Pucelle
Montagn
e de la
Plate
Egravats
Maximum length L. max. (m) 1,027 1123 554
Maximum width l. max. (m) 762 926 394
Maximum height H. max. (m) 210 360 250
Maximum length of track zone L. s. (m) 355 547 174
Maximum length of deluvial deposit L. m. s. (m) 584 662 336
Maximum height of deluvial deposit H. m. s. (m) 110 120 150
Height of track zone H. d. (m) 60 280 110
Radius of detachment zone R. (m) 119 451 220
Perimeter of affected area P. (m) 2996 3851 1889
Landslide surface S. (m²) 455356 850943 167713
Landslide volume V. (m³) 26780071 33059867 10206570
In the case of Egravats, the different tree-age determined using dendrochronology
can be explained in two ways:
a) the firs colonized progressively the stabilized landslide surface, depending on
ecological factors (concurrence between tree species, soil presence/absence and characteristics,
substratum instability, etc.); therefore the colonization time gap can vary depending on these
ecological factors (Pierson, 2007);
b) the anthropic influence (e.g. tree-cutting) can also play an important role in the
selection of trees that remain in the study area.
The position of the roots and the absence of tilting trees suggest that the
colonization occurred some years after the landslide stabilization. This is also confirmed by
the presence of moss and lichen cover on the surface of the blocks. The presence of large
blocks downstream the non-tilted trees also suggest that they were mobilized before the
colonization period and they did not damage the trees. Therefore, using the dendrochronological
approach, we can only say that the last landslide event affecting the entire area occurred 3-5
years before 1840 (the age of the oldest sampled tree).
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