Gruppe für Paläo-Geoökologie

Alpine solifluction and its environmental controls – spatio-temporal monitoring at Blauberg (Furkapass, Central Swiss Alps)

Project leader: Heinz Veit, Armin Rist

Co-workers: Hans Kallen, Lukas Munz, Sebastian Gygax, Alexander Groos

Financed by: GIUB internally

Duration: 2011 – 2020 (thereafter possible takeover by other institution)

Solifluction is defined as slow superficial downslope movement of substrate induced by ground frost. The occurrence of this phenomenon is often seen as indicator for periglacial activity and the related climate. Therefore, various single effects of environmental factors on the solifluction rate were intensively studied by means of their temporal variability. However, most of these studies were performed in (sub-)polar periglacial regions over short periods neglecting the spatial variability. Addressing these inherent gaps of knowledge, the objective of our study is to develop a quantitative model based on measured data to determine the rate of alpine solifluction depending on environmental factors varying in time and space.

This study is performed at the north slope of Blauberg at Furkapass (Central Swiss Alps) between 2380 m and 2700 m a.s.l. This study site belongs to the Alpine periglacial belt comprising seasonal ground frost on the lower slope and permafrost on the upper slope. The exposition ranges from NNW to NE. Regarding geology, the study site is partly situated in the northern paragneiss zone, partly in the Urseren zone consisting of Mesozoic sediments. Climatically, the study site is at the border of the climate regions Valais and Northern Side of Central Alps resulting in a mean annual air temperature between – 4 °C and -1 °C, an annual precipitation of 2800 to 3200 mm and a mean winter snow depth of 150 cm to 250 cm. Alpine meadows extend up to about 2500 m a.s.l., the open scree slope above up to about 2650 m a.s.l. where fissured rock faces follow.

To reach the objective defined above we measure outcome parameters as well as environmental influencing factors varying spatially and temporally. The outcome parameters are:

  • Surface displacement on, besides and below 24 lobes at 9 to 12 points for each lobe

  • Depth-dependent displacement on/below lobes at 2400 m, 2500 m and 2600 m

  • Digital Elevation Model (DEM) in several years and related terrain increases and decreases

  • Spatial occurrence and dimensions of solifluction lobes and related landforms

As environmental influencing factors the following are measured:

  • Air temperature, humidity and pressure, wind speed, precipitation, snow depth and radiation at a meteorological station

  • Potential solar radiation at 17 points along a transect from 2380 m - 2700 m

  • Snow depth and water equivalent at 27 points from 2390 m – 2640 m distributed over slope

  • Bottom temperature of winter snow cover (BTS) at 8 points along transect from 2400 m - 2640 m

  • Evolution of spatial snow cover distribution by automatic camera

  • Liquid and plastic limit of soil matrix on/below 9 lobes between 2350 m and 2600 m

  • Spatial distributed Normalised Difference Vegetation Index (NDVI) by drone in summer

  • Spatially distributed ground surface temperature depending on daytime in summer and autumn

  • Depth-dependent ground temperature/water content at 2400 m, 2500 m, 2600 m on/below lobe

  • Depth of vadose zone at 2400 m, 2500 m, 2600 m on/below lobe

  • Ground electrical resistivity to detect permafrost by geoelectric soundings from 2500 m - 2600 m

The solifluction movement rates and the related periglacial landforms are controlled by the ground’s hydrological, thermal regime and mechanical behaviour. These primary environmental factors are influenced by secondary ones, i.e. weather/climate, snow, vegetation, geology, substrate and relief which are quantified by tertiary measurable single factors. While the single factors constituting weather/climate, snow and vegetation vary both in time and space, those ones constituting geology, substrate and relief vary mainly spatially (temporally only in the long-term). Based on this concept of variable dependencies the data will be analysed statistically leading to the strived model quantifying solifluction by means of the environmental conditions allowing to involve solifluction in paleo-geoecological reconstructions more reliably.