Abstract
High mountain environments have shown substantial geomorphological changes forced by rising temperatures in recent decades. As such, paraglacial transition zones in catchments with rapidly retreating glaciers and abundant sediments are key elements in high alpine river systems and promise to be revealing, yet challenging, areas of investigation for the quantification of current and future sediment transport. In this study, we explore the potential of semi-automatic image analysis to detect the extent of the inundation area and corresponding inundation frequency in a proglacial outwash plain (Jamtal valley, Austria) from terrestrial time-lapse imagery. We cumulated all available records of the inundated area from 2018–2020 and analyzed the spatial and temporal patterns of flood flows. The approach presented here allows semi-automated monitoring of fundamental hydrological/hydraulic processes in an environment of scarce data. Runoff events and their intensity were quantified and attributed to either pronounced ablation, heavy precipitation, or a combination of both. We detected an increasing degree of channel concentration within the observation period. The maximum inundation from one event alone took up 35% of the analyzed area. About 10% of the observed area presented inundation in 60–70% of the analyzed images. In contrast, 60–70% of the observed area was inundated in less than 10% of the analyzed period. Despite some limitations in terms of image classification, prevailing weather conditions and illumination, the derived inundation frequency maps provide novel insights into the evolution of the proglacial channel network.
Highlights
Glaciers in high mountain areas are undergoing drastic alterations at unprecedented and increasing rates as an impact of global climate change [1,2,3]
We demonstrate the applicability of a methodological approach to constrain spatial and temporal dynamics of surface runoff in a sample outwash plain (Jamtal valley, Austria) to overcome data scarcity on paraglacial processes
We present the derived and geo-rectified inundation frequency maps, depicting the annual cumulation of all available and classified images, plus a detailed analysis of the daily maximum inundation area (IAdmax)
Summary
Glaciers in high mountain areas are undergoing drastic alterations at unprecedented and increasing rates as an impact of global climate change [1,2,3]. An increase in extreme (convective) rainfall events is expected [12,13], partly driven by increased evapotranspiration from the surface In this context, the anticipated progressive system shift from supply-limited sediment transport (driven by glacier activity) to more transport-limited processes (during rainfallinduced events) in high alpine catchment areas has been the subject of recent scientific debate [14]. The extent of the inundated area in proglacial outwash plains and the frequency of inundation is largely unknown because of the typically remote location of outwash plains in the proximity of retreating glaciers These environmental conditions usually complicate more direct measurements, especially since the object of investigation is prone to frequent geomorphic processes and changes
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