Development of hydraulic functions in proglacial soils - investigations in two alpine valleys

The retreat of glaciers as a result of climate change is increasingly creating proglacial areas in which new soils are developing. These soils can play a key role in the hydrological processes and water regulation of alpine regions. However, the development of hydrologically important properties of proglacial soils remains largely unquantified. In this study, we explore the development of soil-hydraulic properties of proglacial soils over time and the factors that influence this development. We hypothesized that proglacial soils increase their capacity to retain water over time. 

For this purpose, twelve soil samples were taken from moraines of different ages and geological compositions from two alpine valleys - the Langtalferner with crystalline till, and the Pazielferner with carbonatic till, both in Austria. Samples were analyzed in the laboratory for their physical and hydraulic properties (dry weight, loss on ignition, grain size distribution). Sample volume was calculated using terrestrial structure from motion photogrammetry before and after sample extraction to determine other properties such as density and porosity. Pedotransfer functions, which are used to mathematically estimate properties that are difficult to measure directly, were used to determine other hydraulic properties such as saturated hydraulic conductivity. 

We found that the soil rock fraction is higher in the crystalline till than in the carbonate till. These fractions remained stable with soil age. Organic matter increases significantly in the crystalline Langtal with soil age, while no corresponding increase was found in the carbonatic Pazielferner. We also tested the expectations that a) with increasing soil age the grain size distribution will show a higher proportion of clay and a lower proportion of sand, and b) that the porosity will increase with the rise in clay content to allow greater water retention as the soils age.