Debris flow monitoring in the Moscardo catchment_ recent research and future development

Marco Cavalli, Federico Cazorzi, Stefano Crema, Sara Cucchiaro, Lorenzo Marchi, 2019, Debris flow monitoring in the Moscardo catchment_ recent research and future development, Early warning systems for debris flows_ state of the art and challenges, Bolzano (BZ), 16-19/10/2019,

The Moscardo Torrent is a small stream of the eastern Italian Alps. The catchment ranges from 890 (fan apex) to 2043 m a.s.l. and covers an area of 4.1 km2. The low rock mass quality makes the steep slopes of the catchment supply large amounts of debris to the channels through rockfalls and shallow landslides. The large sediment availability, along with a high degree of sediment connectivity, and the characteristic of rainfall regime (mean annual precipitation amounts to approximately 1700 mm with high-intensity storms in summer) create the perfect conditions for debris-flow occurrence. The Moscardo Torrent was the first catchment instrumented for debris-flow monitoring in Europe. Debris flows have been monitored since 1989, with some gaps in 1998-2000 and 2008-2010.Recently, the monitoring system has been renewed. At the present time, the monitoring system consists of a couple of ultrasonic sensors placed at a distance of about 80 m over the channel bed to measure the flow stage, a high-resolution infrared and visible video camera, and three rain gauges at different elevation. In the period 1990-2018, 28 debris flows were recorded by the monitoring system or assessed by means of post-event field surveys. The analysis of debris-flow volumes, along with geomorphic changes through the comparison of LiDAR surveys between 2003 and 2013, shows the role of channel control works built in the first decade of 21st century in attenuating the magnitude and the frequency of debris flows. Since 2009, however, the Moscardo Torrent featured several debris flows with two of them transporting large sediment volumes (57,000 and 89,500 m3) at the monitoring site, thus suggesting a recovery of the efficiency of debris flows transport. The effect of channel control works on debris flow dynamics has been also investigated through SfM surveys at a specific site in the middle part of the catchment where recent check dams were built in 2015. The poster presents an overview of the Moscardo Torrent monitoring system and the main results of the most recent research in the catchment. Future development of the monitoring site is also outlined.

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