# Torrential Hazards' Mitigation Measures in a Typical Alpine Catchment in Slovenia
## 2 Materials and Methods  
### Case Study Description: Kravvec Ski Resort Area  
The Krvavec ski resort area is part of the Kammik-Savinja Alps, a mountain range located in the northern part of Slovenia (Figure 1). The total area of Kammik-Savinja Alps in Slovenia is around 1000 km\({}^{2}\) and there are several mountains with elevations above 2000 m a.s.l., with the highest one being Grintovec Mountain with an elevation of 2558 m a.s.l. The Krvavec ski resort stretches from around 1500 m a.s.l. to around 2000 m a.s.l. The area is characterized by steep slopes and narrow valleys (Figure 2). The cabin lift is the main means of transport for skiers in winter during the ski season. As can be seen from Figure 1, there are two steep torrential ravines (i.e., the Brezovski graben and the Lukenjski graben) in the upstream slopes from the station of the cabin car. The average longitudinal channel slope of these two torrents is \(\sim\)25-30%, and the total catchment area is close to 2 km\({}^{2}\)[22]. Around three-quarters of both catchment areas are forested, while the rest are agricultural areas [22].  
Figure 1: Location of the Krvavec ski resort area on the elevation map of Slovenia (legend is in meters above sea level) and an overview of the situation in the torrents upstream of the valley station of the Krvavec ski resort cabin lift. Slovenia is positioned between 45.50526\({}^{\circ}\) to 46.83694\({}^{\circ}\) (latitude) and 13.52639\({}^{\circ}\) to 16.45091\({}^{\circ}\) (longitude). The Krvavec meteorological station is positioned at 14.5333\({}^{\circ}\) longitude and 46.2973\({}^{\circ}\) latitude and at 1742 m a.s.l.  
Figure 2: Two photos of the situation in the Brezovski graben and Lukenjski graben torrents, respectively. The channel width is between 1–2 m to several meters.  
The mean annual precipitation at the top of the Krvavec ski resort area (approx. 1700 m a.s.l.) is around 1620 mm (in the period 2010-2020), with no clear seasonal pattern (Figure 3). Moreover, there is a clearer pattern in the monthly rainfall erosivity distribution with a clear peak in the summer period (Figure 3). The rainfall erosivity was calculated based on the 30-m rainfall data for the 2010-2020 period based on the RUSLE methodology ([PERSON] _et al._, 2018) and using the RIST software ([PERSON] _et al._, 2018). The average annual rainfall erosivity in the 2010-2020 period was around 3531 MJ \(\times\) mm \(\times\) ha\({}^{-1}\)\(\times\) h\({}^{-1}\)\(\times\) year\({}^{-1}\), which can be regarded as relatively large ([PERSON] _et al._, 2018). Therefore, it is evident that hydro-meteorological events can occasionally be relatively extreme in this alpine part of Slovenia. In combination with steep slopes and other torrential characteristics, this can lead to rainfall events, such as the one that occurred in May 2018 (Section 2.2). This local thunderstorm triggered a local debris flood that partially devastated the valley station of the Krvavec ski resort cable car and interrupted the local access road to the station ([PERSON] _et al._, 2018)--for protection against such torrential events, several structural protection measures were built in the past ([PERSON] _et al._, 2018; [PERSON] _et al._, 2018), but most of these torrential structures were already in relatively bad condition before, and especially after the May 2018 event (Section 2.3).