Snow avalanche activity in the Țarcu Mountains, Southern Carpathians. Comparative analysis based on tree ring studies.

Information regarding the Spatio-temporal behavior of extreme natural phenomena, such as avalanches, has become necessary due to the increase in human casualties and property damage in recent decades. Thus, the prevention of geomorphological risks associated with high mountain areas requires knowledge of the characteristics of geomorphological processes that occur here. Avalanches occupy a central place among these phenomena with the greatest destructive capacity (Voiculescu, 2000).

The aim of this study is to 1) reconstruct the past activity of snow avalanches in the Tarcu Mountains and to fill a gap in knowledge due to the lack of such studies in the studied area and 2) to point out the synchronicity of major events with those reconstructed in other mountain areas in the Southern Carpathians: Bucegi, Făgăraş, Piatra Craiului, Parâng Mountains. The morphology of the investigated area determines the formation of constrained avalanches. For events reconstruction, we used semi-quantitative Shored index (Shroeder, 1980). We identified 51 events in a 101-year chronology in Picea abies: 12 events with I_t  between 10-20% and 6 events with I_t  between 20-40%. The relatively young age of the trees is a good indicator of the disturbances caused by past events. We based our reconstruction on dating growth disturbances such as reaction wood, traumatic resin ducts, and scars. Reaction wood, very present in our case, highlighted the intensity of avalanche activity and the expansion of events. Resin ducts and scars are a good indicator of avalanches that brought us important information in the dating of events and helped us to delimit the affected areas (the 2005 synchronous event with other 9 couloirs). The return period values are higher than those obtained by Corona et al. (2010) in the French Alps (2.5-12 years), smaller than those obtained by Corona et al. (2007) in the Swiss Alps (slightly over 20 years) and similar to those obtained by Decaulne et al. (2012) in Northern Iceland (15-20 years). 11 events synchronous with events of another 11 couloir (1985, 1987, 1988, 1998, 2000, 2005, 2006, 2007, 2008, 2010, 2016).

In the future we want to highlight the type of avalanche by relating the activity of avalanches to cold season temperatures by using the Standardized Winter Index (IIS) (Micu, 2009; Voiculescu, Onaca, 2014) and climate scenarios, cf. Germain et al. (2009). Our study can be the basis for the elaboration of hazard and risk maps, in the perspective of tourist investments in the Tarcu Mountains or in the development of tourist activities in safe conditions.