Study: Avalanches along the Northwestern slope of Todorka Peak, Pirin mountains

Aim of this Study is to study the effect of avalanches on trees on the Northwestern slope of Todorka Peak, Pirin mountains and to date past avalanche events. It was a part of the PhD study of Eng. Momchil Panayotov.

Pirin Mountains are the second highest in Bulgaria (Vihren peak, 2917m a.s.l.). The climate in the range is formed under the complex influence of Mediterranean and Atlantic air masses, with the predominance of moist Mediterranean masses. This is reason for milder winters with frequent snowfalls and occasional Southwestern winds. Due to its specific climate Pirin Mountains have become refuge for numerous plant species, many of which are endemic. This is the reason why the majority of the northern part of the range has been declared a national park and included in UNESCOs Man and Biosphere list of very important natural zones. On the territory of the park are situated some of the best-preserved forests of the Balkan endemic species Pinus peuce and the very rare Pinus heldreichii.

Todorka peak (2748m a.s.l., 41.45'N, 23.25'E) is situated in the central part of the mountains , just opposite to the highest Vihren and Kutelo peaks.

The Northwestern slope of Todorka peak with its numerous avalanche tracks and couloirs descending through Macedonian pine forests

The specific position of the Northwestern slope of Todorka peak is the reason for big snow accumulations. This, together with the fact that the slope is with one of biggest vertical drops in Bulgaria is the reason why it has very high avalanche activity.
On the slope there are eight major avalanche couloirs separated by wide shoulders (ridges).
The middle and lower parts of the ridges are covered by forests dominated by Macedonian pine (Pinus peuce Griseb.) with limited participation of Norway spruce (Pecea abies Karst.), Scots pine (Pinus sylvestris L.) and Bosnian pine (Pinus heldreichii Christ). The trees at the treeline are about 120-140 years old, while those at the forests below reach up to several hundred years (oldest found tree > 600 years).

Above the forests and along the borders of the avalanche couloirs there are dense communities dominated by mountain pine (Pinus mugo Turra ssp. mugo ) with limited participation of small Macedonian pine trees, Common juniper (Juniperus communis Willd. var. nana ), Goat willow (Salix caprea L.) and Mountain ash (Sorbus aucuparia L.), White birch (Betula pendula Roth) at lower altitudes.

Observations of forest stands and single trees show that the highest zones of the forests have been influenced periodically from falling avalanches.
The steep slopes and the fact that there are wide spaces between the old trees contribute for the initiation and falling of avalanches of different sizes in the forests below the treeline.

The runout zone of one of the couloirs. There are signs of huge avalanche in the past (the ridge to the right of the couloir).

Taking cores from old trees with the aim to build a "reference chronology"

To determine the growth differences between potentially influenced and not influenced by avalanches trees there were collected increment cores from several different locations. One of them is at the top of a slope where there is no possibility of avalanche influence. On this place has been marked a permanent plot and carried out measurements of tree diameters and heights.
The other trees, which have been selected for analysis, are situated at treeline locations on the ridges between the avalanche couloirs. For determining of the avalanche regime and dating bigger slides, cores have also been extracted from trees, which are situated on the borders of the avalanche couloirs and in the runout zones.

Besides influence from avalanches the trees in the forests at the treeline and below it experience periodic influence from big snowfalls and possibly accumulation of rhyme and ice. There have been observed occasions with breakage of the top of the stems of smaller trees and big branches of old trees after intensive snowfalls.
Since the slope is lee to the prevailing strong Southwestern winds they are not from the most important limiting factors for the growth and development of the trees.

The collected data from filed measurement and observations have been inserted in GIS, which facilitates composition of thematic maps, filed work and future research in the specified regions and sites.

Up to this moment there have been built Reference chronology and the major avalanches in two couloirs have been dated.


PANAYOTOV, M (2011) Avalanches on the northwestern slope of peak Todorka (Pirin Mts, SW Bulgaria) and their influence on forests. Phytologia Balcanica 17(2): 237-246

Panayotov, M.P. and Yurukov, S. (2007) Tree ring chronology from Pinus peuce in Pirin Mts and the possibilities to use it for climate analysis. Phytologia Balcanica, 13(3): 313-320

Panayotov, M.P. (2007) Determination of avalanche events by analysis of tree rings of Pinus peuce. Econological Engineering and Environmental Protection, No.1: 75-82; in Bulgarian, English abstract;


Dr. Momchil Panayotov, e-mail: mp2@ abv.bg (Please note: there is an empty space after the "@" symbol. Youi have to remove it to send e-mail)