LANDSLIDE AND DEBRIS-FLOW SEDIMENT FLUX IN GLACIAL AND PERIGLACIAL MOUNTAIN DRAINAGE BASINS OF THE EASTERN ITALIAN ALPS

While it is widely recognized that deglaciation and permafrost degradation can induce generalized instability in steep mountain terrain, beyond the documentation of single catastrophic mass-wasting events, there appears to be little empirical work on how the colluvial sediment cascade functions under conditions of increasing atmospheric temperature rise in a formerly glaciated landscape structure. Understanding and quantifying the influence of similar transient conditions on mass-wasting processes holds critical long-term implications on the overall sediment flux reshaping post-LGM landscape evolution, as well as more practical short-term applications on water quality issues, damage control to infrastructure, and reservoir siltation. We present an integrated approach that aims to: (i) document the spatial distribution of mass-wasting activity and sediment production in the Saldur River basin (97 km2); (ii) detect causal linkages between mass-wasting intensity, the potential spatial distribution of discontinuous permafrost, and patterns of glacier retreat; (iii) identify source-to-sink colluvial sedimentary pathways as modulated by the spatial organization of active and relict glacial and periglacial landforms; and (iv) test the reliability of a geomorphometry-based index of sediment connectivity. To these ends, we map rock glaciers, protalus ramparts and moraines, and compile a field- and air photo-based multi-temporal (1959-1969-1982-1997-2000-2006-2008-2011) inventory of colluvial sediment sources. We then combine these data with two historical datasets of debris flow and landslide events (both implemented and maintained by the Autonomous Province of Bolzano) and analyse mass-wasting spatial distribution and intensity in relation to proximity to glacier fronts, intact and relict periglacial landforms, and a permafrost index map (i.e., PermaNET; http://www.permanet-alpinespace.eu/). This work is part of SedAlp (www.sedalp.eu), a project funded through the Alpine Space Programme, and benefits from COST Action ES1306: Connecteur