# Torrential Hazards' Mitigation Measures in a Typical Alpine Catchment in Slovenia
## 3 Results and Discussion
### Ongoing Monitoring  
The monitoring system of torrential processes in the Krvavec area can be divided into the following parts:  
* Measuring local rainfall using one tipping bucket as a rainfall gauge (resolution 0.1 mm) (will be installed at the top of Brezovski graben torrent);
* The Brezovski graben is regularly surveyed using Unmanned Aerial Vehicles (UAV drones), and surface changes (eroded slopes and new deposits upstream of the flexible barriers) between the two field measurements are determined from a difference between two consecutive LiDAR maps of the torrent. These measurements will explicitly tell us about erosion and sedimentation dynamics in the torrential channel and reveal the efficacy of the built flexible net barriers to retain coarse torrential debris. After they are filled up with coarse debris, they will support unstable torrential flanks, and sediment transport to downstream sections closer to the cable car station will increase again;
* Six devices, called Guards(r), were installed on four flexible barriers in the Brezovski graben (barriers 1, 3, 7, 8, 9, and 12) and on two flexible barriers in the Lukanjski graben (barriers 2 and 6). Introduced in late 2020, a Guard(r) is a waterproof, small, battery-powered autonomous device (2.6 kg, battery life estimated to be between 7 and 10 years), easily installed on the suspension rope of a selected protection barrier for permanent monitoring (24/7) of its environmental and physical status under the toughest conditions [32]. It monitors corrosion (due to air pollution) and movements (due to debris or rock impacts) of the flexible nets, as well as reporting events, such as a rockfall or a debris flow via a mobile network (i.e., GSM, UMTS, LTE) to a dashboard on your computer--without a need to go to the field site. It is, in essence, an IoT (Internet-of-Things) smart data logger developed to estimate corrosion damage to a single rope within flexible net barriers [33], but it is additionally equipped with an impact sensor unit, measuring accelerations of up to 200 g and forces to up of 294 kN. The Guards(r) report events when a barrier is moved due to inflowing debris or sediments (even single surges in the case of a wet debris flow), or a single falling/rolling large rock hits it, but also due to strong winds or even wild animals. Such reports are then compared to local weather (wind, air temperature, and rainfall data) to differentiate among causes for barrier movements. The installed Guards(r) started operating in March 2023, and until the end of July, occasional activities were reported. In total, in this period, there were 42 entries in the cloud-based database that were associated with an increase in force on the flexible net barriers. The measured force ranged from around 1 g to around 17 g. In this period, there were 6 days when the reported number of events was larger than 1 (Table S1). It can be seen that on days with more than one activity detected by Guards, there was either strong wind or a storm in that area (Table S1). Furthermore, the maximum 30-m wind speed and rainfall were above average (Figure S6). However, the reported 30-m rainfall values shown in Table S1 all have a return period of less than 5 years according to the intensity-duration-frequency (IDF) curves for that location (i.e., the 30-m rainfall rate with a 5-year return period equals 25 mm). It can also be seen that there are some days where the activity detected by the Guards(r) was not driven by extreme wind or precipitation (Table S1). Some events were also detected on the days without rainfall (Table S1). During the period of Guard(r) operation, there were some days when wind speed was relatively high, or 30-m rainfall rates were relatively high, but there was no activity detected by the Guards(r) (Figure S6).