Tracer Characterization of Water Sources and Erosion Monitoring in an Alpine Catchment

Avalanches, landslides and debris flows in the mountains pose significant threats to infrastructure, ecosystems, and human lives, with their aftermath altering hydrological processes and notably affecting erosion dynamics. However, existing research lacks a comprehensive understanding of how precipitation exacerbates erosion on a previously damaged hillslope, and what the spatial origin is of overland flow in relation to other water sources present in a catchment. This thesis is aimed at investigating precipitation-induced overland flow on a steep hillslope previously damaged by an avalanche event, through the monitoring of the hillslope erosion processes and a tracer characterization of the water sources. The study area is a small Dolomitic catchment named Bridge Creek Catchment (BCC), which is located in the northeastern Italian Alps. The implemented methodologies included the sampling of water sources (rain water, stream waters, spring waters, overland flow and shallow groundwater) for isotopic analysis (δ2H and δ18O) and electrical conductivity (EC) measurements, as well as the collection of soil and sediment samples for texture and bulk density analysis. Samplings were carried out about biweekly from late May to early November 2024. Results showed that overland flow generally retained the isotopic and EC signature of recent precipitation events and had high temporal variability, while stream and groundwater had more consistent composition throughout the season. In addition, EC measurements and leaching tests revealed the mobilization of ions during the generation of overland flow on the eroded hillslope. Soil texture of the eroded sediment was generally sandy clay loam and had a low bulk density, and 11602.2kg of sediment was removed via overland flow from 67% of the total hillslope area over the sampling timeframe. The outcomes of this study provide valuable insights into the complex hydrological interactions between precipitation, overland flow, and erosion on damaged hillslopes, contributing to the resilience of mountainous ecosystems and communities facing increasing risks from natural hazards in a changing climate.