Sediment reworking of Little Ice Age lateral moraines in the Italian Alps: A morphometric and morphodynamic analysis using multitemporal aerialimages and current UAV-data

Kurzfassung/Abstract

The rapid glacier recession in the European Alps exposes high amounts of unconsolidated sediment, especiallyin the form of moraines, which is reworked subsequently by processes such as gullying, slope wash and debrisflows. The temporal development of the morphodynamics depends both on the abundance of loose sediment afterdeglaciation and on morphometric properties such as the altitude a.s.l., the aspect and slope gradient of the respec-tive slopes. Apart from slope adjustment due to reworking of sediment, the moraine slopes can also be stabilizedby vegetation succession, depending on the geomorphic activity and climatic conditions.To date, there is only limited understanding of the morphodynamic activity since deglaciation after the Little IceAge (LIA) and the factors influencing it. To gain deeper insight into the processes and factors involved as well astheir connections, our research focuses on the following key questions: (1) What differences in morphodynamicactivity appear on the lateral moraine tracts of cirque and valley glaciers deglaciated since the LIA? (2) Whichgeomorphological characteristics, as for example the degree of gully incision, can be detected and how are theyrelated to the altitude a.s.l. and to morphometric parameters like the slope gradient? (3) Are there differences inthe morphodynamic activity between slopes well connected with fluvial systems and those, which are hardly con-nected? (4) Can differences in vegetation succession be noted, depending on the altitude of the respectable glacier?(5) Does vegetation cover have a detectable influence on morphodynamics or vice versa? We address these ques-tions with a strong focus on the general altitude of the respective moraine tract in comparison to moraines of otherglaciers. Moreover, the time since deglaciation, which varies along the moraine tract in accordance with the pro-gressively melting glaciers, is considered thoroughly.For our analyses, moraine tracts of 10 glaciers in the German, Austrian, and Italian Alps were selected, of whichthe latter are presented here. These glaciers not only differ in their location within the Alps, but also regarding thealtitude of their tongues and their size. This enables a correlation analysis of the morphometric, morphodynamicand vegetational properties depending on these general characteristics of the glaciers.For the long-term detection of sediment reworking and changes in slope morphometry, we use a series of historicalaerial images, dating back to 1959, to generate Digital Elevation Models (DEM) by photogrammetric analyses. Inorder to detect recent geomorphological processes and to analyse vegetation cover and morphometry, we derivehighly accurate DEMs from our own UAV-surveys conducted in summer 2017.