EUROCORES_TOPOEUROPE_1. Call_Quantifiying Late and Postglacial sediment fluxes and storage (SourceSink)

Within the ESF-Eurocores programme TOPO-EUROPE the CRP (collaborative research project) SourceSink ("From Source to Sink: integrated natural hazard assessment through the quantification of mass transfer from mountain ranges to active sedimentary basins") encompasses 15 IPs (individual projects) and 16 APs (associated projects). In this context, the project (IP 04) focuses on the quantification of Late and Postglacial sediment fluxes and storage in nested Alpine catchments. Sediment cascades in alpine environments are influenced by topography, (neo) tectonics, climate and human impacts and by the interaction between these components. An analysis of sediment cascades implies a differentiation of source areas, pathways and (terrestrial) sedimentary sinks. As large Alpine areas currently shift to "new" source areas due to permafrost degradation (e.g. destabilizing talus slopes) and glacier retreat, this increasing sediment availability is of major importance in terms of natural hazard assessment. Moreover, this study will contribute to a deeper understanding of the paraglacial sedimentation cycle in different sized Alpine environments. The study area is located in the Eastern High Tauern Range (Austria) encompassing a part of the Möll catchment with several tributaries. Based on a systems approach, different subsystems of specific sediment fluxes and storages types within the sediment cascade will be identified and quantified. This requires the understanding of single landforms and landform units that indicate areas of erosion (e.g. source areas of debris flows) and sedimentation (e.g. floodplains, talus systems). The outcome of this project (i) will improve the resolution and knowledge of source area characteristics, and (ii) will contribute to a better understanding of the source to sink linkage of terrestrial sedimentary systems on relatively short spatial and temporal scales. The cross-scaling approach requires a combination of field and modelling techniques, including the (i) identification and spatial distribution of landforms and processes through orthophoto-interpretation, geomorphological mapping, and morphometric digital terrain analyses; (ii) quantification of single landform volumes and entire catchment storage (volume/mass) by shallow coring (<20 m), field geophysics (ground penetrating radar, electrical resistivity tomography, refraction seismic tomography), morphometric and knickpoint analyses, and the application of the Sloping Local Base Level (SLBL-) model; (iii) calculation of present-day erosion rates by means of slope process monitoring (incl. repeated terrestrial laser-scanning and continuing a 20- years time series of solifluction rates) and (iv) calculation of Late and Postglacial erosion rates by coring, sampling and numerous 14C datings. The project will substantially improve the knowledge about dynamics of source systems. It will be characterised by an intensive cooperation within the CRP (e.g. meetings, workshops) and an exchange with national and international colleagues outside the programme. Due to the intensive fieldwork, the realisation of the project demands one PhD-position, a project accompanying reimbursement of work on an hourly basis and three one-year scholarships promoting young researchers to a high international scientific level (doctoral and diploma theses).

Main objectives of research addressed by the collaborative research project (CRP) SourceSink ('From source to sink: Integrated natural hazard assessment through the quantification of mass transfer from mountain ranges to active sedimentary basins') refer to the interdependency and major controls of alpine topographic evolution and corresponding foreland basin sedimentation. To reach this goal, a number of individual projects (IP's) focussed on the identification, analysis and quantification of erosion (source areas), transfer (carriers), and deposition of sediments (sinks) on different spatial and temporal scales within the Danube River Basin and on links and feedbacks between them. This project (IP4), entitled 'Quantifying Late and Postglacial sediment fluxes and storage in nested Alpine catchments - a geomorphological perspective of the source area', contributes a detailed small-scale investigation of postglacial sedimentation and denudation in the inner-alpine Gradenbach catchment (~32 km, Schober Mountains, Austrian Alps), which is interpreted in a larger-scale context (several neighbouring catchments draining into the upper Möll River). Quantitative analyses have been carried out in the Gradenmoos Basin (subcatchment size: ~4.5 km), an effective sediment trap in the central Gradenbach catchment considered to be a valuable Holocene sedimentary archive. To understand current catchment configuration, a digital geomorphologic landform inventory was created using a combined, field and GIS-based mapping approach. The infill architecture of the basin (incl. sedimentation rates), total sediment storage volumes as well as corresponding rates of denudation and rockwall retreat have been accurately reconstructed using high-resolution surface (terrestrial laserscanning) and subsurface data (geophysical prospection, core-drilling), GIS-based bedrock interpolation and 3D modelling techniques, as well as temporal investigations (palynologic and stratigraphic analyses; radiocarbon dating). Today, the basin archives a complete Holocene sedimentary record covering a time period of ~11.000 years. During large parts of the Holocene, sediment output is negligible since the existence of a former lake in the basin could be proved for ~7.500 years after deglaciation. Total sediment storage amounts to ~20 Mio m3, whereas hillslope deposits surrounding the basin overbalance the basin fill deposits by a factor of five. Derived from theses volumes, rates of rockwall retreat and mechanical denudation of less than 520 mm/ka, however, indicate comparatively low values despite of steep slope gradients and coarse and blocky weathering conditions in the area. The project delivers an accurate and almost complete small-scale sediment budget analysis, contributes new data on postglacial rockwall retreat in the eastern Alps, and copes with several uncertainties disregarded in former studies, such as the quantification of pre-Holocene basal till underneath present-day landforms, the incorporation of redeposited sediments, and the absolute timing of Holocene sedimentation and denudation.