Slope Wash, Gully Erosion and Debris Flows on Lateral Moraines in the Upper Kaunertal, Austria

Abstract

The science on high-mountain proglacial systems is a rather young field of study, but has gained importance since a few years ago. In this context, we investigated a part of the lateral Little Ice Age (LIA) moraine that was built up by the second longest glacier of the Eastern Alps. The Gepatschferner glacier in the Upper Kaunertal, Central Austrian Alps, created up to 150-m-high moraine slopes during its LIA advance that are now prone to paraglacial reworking. To analyse the degree of reworking and to identify the driving forces behind the slope development with both their spatial and temporal variations, we conducted several case studies, mainly based on data acquired by remote sensing techniques (multitemporal TLS and aerial photographs) and their derivatives (DEMs, DoD, orthophotos). First, a medium-term (5 years) overall balance of erosion and deposition of the studied slope is calculated. Second, seasonal variations of the process dynamics are uncovered based on short-term TLS measurements within c. one year. Third, the sediment contributing area (SCA) is delineated to estimate fluvial reworking. Fourth, following paraglacial adjustment studies by Curry et al. (2006), we measured and analysed gully development with time since deglaciation. The case studies lead to the conclusions that paraglacial adjustment of the study slope is still in progress. Extreme events in summer play a dominant role for morphodynamics, followed by processes during winter, whereas springtime offers important preparatory conditions for sediment transport. Fluvial transport is considered to have minor effects on the moraine development compared to gravitational processes. And last but not least, the development of gullies depends more on natural boundary conditions than on time since deglaciation.