Effects of climate warming on debris flow activity and sediment supply in high mountain regions.

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In the framework of the paraglacial cycle (i.e., the theoretical model that describes the sediment flux evolution after deglaciation), this project wants to analyze the effects that the ongoing climate warming has on the sediment supply and on the occurrence of debris-flow events in mountain catchments. Previous studies on these topics indicate that climate plays a crucial role in the surface processes dynamics and sediment transfer in mountain basins. However, the different response of mountain catchments to the modern climate-change suggests that some other parameter, in addition to the increase in water discharge and sediment availability that follows the melting of ice, may control the dynamics of sediment production and sediment transfer. Recent studies have suggested that a good connectivity and a balanced transport capacity of the rivers may be pivotal in this context. However, studies that investigate these aspects within the sediment cascade of mountain basins and in light of climate warming remain scarce. In this project, I propose to analyze two small valleys of the Italian Alps in the effort to understand the response of mountain catchments to climate warming and assess the role that glacial melting, permafrost degradation, and increased extreme precipitation may have on sediment supply and debris-flow activity. To reach these goals, I propose to combine different techniques and analyze: 1) the variations in the sediment transport dynamics of mountain basins by means of cosmogenic nuclides techniques; 2) the chronology of debris-flow events through dendrochronology dating; and 3) the location of debris flows and rock falls initiation areas by the time-series analysis of orthophotos. By analyzing basins with different morphologies, I will be able to frame the effects of local parameters (such as morphology, vegetation, and connectivity) in the sediment transport dynamics of mountain catchments. This approach will allow me to explore the effect of temperature and extreme precipitation increase on both glaciated and deglaciated basins, and to assess their influence on the release and transport of sediment. By combining these different techniques I will cover different timescales, integrating existing information (i.e., database of natural hazard events) with new data on the past, and using them to explore possible future scenarios. The project outcomes are expected to bring us one step forward in the understanding of how climate may modulate surface processes in mountain catchments. The relevance of these results is not limited to the scientific community, but is expected to be of primary importance also for local and regional authorities, who may use the project’s outcomes to reduce the vulnerability of mountain regions and develop sustainable management plans for Alpine environments.