The importance of geomorphology for debris-flow activity in Alpine catchments

Abstract:

Debris flows pose a severe threat to alpine areas, as their discharge can be up to an order of
magnitude larger than a typical flood event in a mountain catchment. In this study we are
examining geomorphological fingerprints, which are suspected to be decisive if debris-flow
activity is present or not (slope-area plots, terrain roughness, Melton number, weathering
potential of geological units, etc.) for catchments in contrasting regions in the Austrian Alps.
To quantify the geomorphological processes important for debris-flow initiation – such as
channel refill, bank/bed erosion and landsliding - a set of six selected catchments is
periodically monitored over three years. A comparison of repeated digital surface models and
aerial photographs created through photogrammetric UAV surveys provides the base for
identifying zones of active erosion and deposition within the catchments and thus quantifying
the local sediment dynamics. Furthermore debris-flow activity as well as clearwater
discharge is monitored with camera-traps in the channel reaches. This combined information
will give an insight, which geomorphological boundary condictions play the most important
role for debris-flow initiation in the Austrian Alps and in which settings they are present. Our
study aims to be the foundation for an improved regional risk assessment in Alpine regions.