How will bedload transport respond to climate change in Alpine regions? The "ALTROCLIMA" project

Alpine regions are among the areas that are the most intensely impacted by climate change. Predictions of how such changes affect meteorological conditions, as well as snow and ice cover and water discharge in mountain regions, are well established. However, how climate change has affected and will affect sediment transport in general and bedload transport in particular in such environments has yet to be studied.

Bedload transport within Alpine rivers is of ecological importance for river systems, impacts the economic efficiency of hydropower and is a critical parameter in assessing hydrogeological risks. This transport is determined by the sediment supplied to the river and the river's capacity to transport these sediments. These complex processes are closely intertwined with climatological conditions within a catchment, particularly in catchments with substantial glacial coverage. However, predicting how bedload transport behaves due to a changing climate is challenging.

This project fills this knowledge gap and investigates the link between bedload transport and rapid climate change in Alpine environments and aims to predict future trends for the current century. To reach this goal, a wide range of objectives has been set. We work towards providing the first reliable, multi-site quantification of past bedload transport changes under warming conditions, as well as to determine the role of geomorphic processes on bedload export in the analysed river networks. Furthermore, we are working on establishing modelling frameworks to predict subglacial and hillslope sediment supply as well as hydrological discharge to create a bedload transport modelling chain. The modelling chain is based upon the D-CASCADE model, which allows quantifying the spatio-temporal bedload (dis)-connectivity in river networks. Supplying the model with climatological and hydrological predictions enables the estimation of future bedload flux and erosion/deposition patterns under different scenarios. The approach for estimating the evolution of bedload transport will be developed and tested in the Solda (Italy) and Navisence (Switzerland) catchments, due to the data availability of the recent bedload transport history. Once validated and calibrated, the approach will be applied to further selected catchments.

In summary, the project aims to provide a decadal-scale quantification of changes in Alpine bedload transport due to climate warming and predict its evolution in the 21^st century. We anticipate an initial increase in sediment transport with increasing glacial melt, driven by climate warming. However, this surge may be temporary as diminishing glaciers reduce their contribution to river discharge after a phase of maximum discharge rates. Beyond the academic value of this research, it will offer critical insights for water resource managers in Alpine regions.