A new modelling approach to delineate the spatial extent of alpine sediment cascades

The delineation of sediment cascades in alpine geosystems requires the identification and localisation of the effective geomorphic processes. In order to classify the terrain on that basis, modelling approaches originally designed for natural hazard zonation were extended. Four sub-models are used to simulate geomorphic processes: (1) potential initiation sites, (2) process pathways, (3) run-out distances and (4) geomorphic activity (erosion, transport and deposition areas). By overlaying the datasets comprising the spatial extent of geomorphic activity, a map of geomorphic process units, i.e. a map with units of homogeneous process composition can be generated. As the modelling of process pathways includes a topology of process links, the map can be used to address several geomorphologic problems, e.g. process interaction, sediment routing, hillslope-channel coupling and the identification of areas of predominant erosion and deposition (sediment storages). This paper presents the design of the modelling approach and selected results of rockfall, slope-type and torrent bed-type debris flow modelling in an alpine basin (Lahnenwiesgraben) in the Northern Limestone Alps, Germany.