Abstract ID: 3.11422 | Accepted as Talk | Talk | TBA | TBA

Climate change is resulting in rapidly increasing temperatures in the European Alps, rising twice as fast compared to the global average. The resulting unprecedented glacier retreat is well studied, but little is known about the impact on sediment yield. Thus, the objective of this research is to understand the paraglacial response of Alpine basins to warming, especially in the context of peak water and peak sediment, through an inter-basin comparison.

DEMs (Digital Elevation Model) from aerial archival photogrammetry (1970s) and corresponding DoDs (DEMs of Difference) were created for multiple glaciated basins in southwestern Switzerland. These allowed for a basin-scale analysis of sediment erosion and deposition patterns. A comparison to records of sediment yield provided by hydropower companies was used to infer the drivers of these changing patterns and to better understand sediment export of these basins over the last decades.

The DoDs show very few localized sediment sources, with most hillslopes having remained stable over the studied time period. However, hydropower records indicate a rising trend in sediment export from these basins since the 1980s. This indicates that glaciers are the dominant suppliers of sediment in these glaciated basins.

These analyses suggest that during a period of rapid climate warming the sediment yield is dominated by glacial sediment supply and with only relatively small and localized supply from hillslopes, the latter representing the paraglacial supply. As glaciers become smaller and peak sediment is attained, we would expect the paraglacial component to gain importance, but remain inferior to the previous glacial erosion. The exact timing of peak sediment with respect to peak water will likely depend on a multitude of factors, including, but not limited to, glacier size, basin topography (slope), connectivity (including temporary sediment stores like overdeepenings) and the reduction of transport capacity following peak water. Understanding how sediment yield has been influenced by recent warming is crucial for predicting the future evolution of sediment export from alpine basins. This is especially relevant for anticipating ecological changes to fauna and flora, mitigating risks to human lives and infrastructure and managing hydropower installations.