Sediment Budgets in High-Mountain Areas: Review and Challenges

The changes in the sediment transport regimes of high-mountain areas as a consequence of global warming have received growing attention by geomorphologists, not only because these changes can imply a heightened threat to human infrastructure. While many studies dealing with high-mountain sediment transport processes (e.g., rock fall, debris flows, avalanches, stream transport) have focused on one process only, few studies have tried to establish a holistic view of the sediment transport in high-mountain catchments. This review chapter identifies the need for research in high-mountain sediment budgets, aims at providing an overview of studies that have contributed to this goal, and discusses the methodological state of the art in the different steps necessary for sediment budget construction. In addition, relevant research gaps will be identified, thereby showing potential for future research

A Sediment Budget of the Upper Kaunertal

This chapter presents the sediment budget of the Upper Kaunertal (Ötztal Alps, Austria) for the years 2012–2014 as obtained in the framework of the PROSA (high-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps) research project. An important methodological basis of this high-mountain sediment budget is the usage of study area-wide LiDAR data (TLS and ALS) of comparatively high temporal and spatial resolution to measure rates of erosion and deposition, and to regionalize/upscale rates at the local scale. After several billion measurement points and data from fieldwork, mapping, and modeling efforts had been processed and evaluated, it was possible to identify and quantify sediment transfer by all relevant processes at the scale of the 62 km2 study area. These processes include rockfall of three different magnitude classes, debris flows, avalanches, creep on talus, fluvial processes (hillslopes and main fluvial system), rock glaciers, and glaciers. After a short presentation of the process-specific methods to obtain catchment-wide rates, we discuss process-specific results and the budget. The sediment budget does not only show the relative importance of the mentioned processes and spatial subunits (proglacial vs. non-proglacial) in the Upper Kaunertal. It also gives insight into the importance of high-magnitude events and the configuration of the sediment transport system

An Inventory of Proglacial Systems in Austria, Switzerland and Across Patagonia

Deglaciation since the Little Ice Age has exposed only a small areal proportion of alpine catchments, but these proglacial systems are disproportionately important as sediment sources. Indeed sediment yields from proglacial rivers are amongst the highest measured anywhere in the World. Motivated by a desire to understand where exactly within catchments this sediment is coming from and how it might evolve, this chapter presents the first digital inventories of proglacial systems and the first comparative inter- and intra-catchment comparison of their geometry, topography and geomorphology. Whilst focussing on the description of these inventories and on descriptive statistics, it highlights the potential of these data, with examples from Austria, Switzerland and Patagonia, for interpreting landscape evolution status, predominant earth surface processes and glacial meltwater inundation patterns. Switzerland has by far the highest proportion of very small (<0.5 km2) proglacial systems. Patagonia has the most even distribution of proglacial systems in terms of areal size and elevation above sea level. We found no east–west or north–south spatial pattern in geometric or topographical metrics, such as hypsometric index, thereby refuting a straightforward control of climate-driven precipitation or air temperature. However, we note that geology, particularly rock hardness, could be a major factor in proglacial system character. Likely sediment sinks can occupy up to c. 30 and 20% of proglacial systems in Austria and Switzerland, respectively, but up to 90% of those in Patagonia where many systems terminate on a coastline. Meltwater influence maps and landform maps, derived from contributing area and slope data, respectively, will not only be useful for many environmental science disciplines but also for water resources, landscape managers and natural hazards authorities. Overall, this chapter presents an objective and easily implemented method for making proglacial systems inventories and for characterising inter- and intra-catchment geomorphological form and function

Sediment Connectivity in Proglacial Areas

Sediment connectivity is an emerging property of geomorphic systems and has become a key issue in research on geomorphic processes and sediment cascades. Sediment connectivity represents coupling relationships between system compartments and elementary units, and thus its understanding has important implications for the behaviour of hydro-geomorphic systems. The investigation and characterization of sediment connectivity and its evolution through time are of particular importance in proglacial areas and high-mountain environments since they are subject to intense morphodynamics and frequent changes in their structure and subsequent variations in sediment connectivity. This chapter aims to review the state of the art of sediment connectivity in proglacial and high-mountain environments studies, provides a synopsis of the most widespread landforms in mountain headwater catchments and describes their role with respect to coarse sediment connectivity. In addition, a section of the chapter is dedicated to the description of a recently developed topography-based sediment connectivity index. An example application to two contrasting alpine glacier forefields shows the effectiveness of this index for investigating and interpreting spatial patterns of connectivity in high-mountain catchments. Finally, we sketch avenues for future research regarding sediment connectivity (not only) in proglacial systems