21 Apr 2022
21 Apr 2022
Status: this preprint is open for discussion.

Use of fluorescent sand to assess plot-scale hydrological connectivity and sediment transport on young moraines in the Swiss Alps

Fabian Maier1,, Florian Lustenberger1,2,, and Ilja van Meerveld1 Fabian Maier et al.
  • 1Dept. of Geography, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
  • 2Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Mountain Hydrology and Mass Movements, Zuercherstrasse 111, CH-8903 Birmensdorf, Switzerland
  • These authors contributed equally to this work.

Abstract. The surface of the earth is constantly changing, especially in mountain areas, where glacial retreat uncovers large bodies of unconsolidated sediment. However, our knowledge on overland flow (OF) generation and related sediment transport is still limited, partly due to a lack of methods to trace the pathways of water and sediment on the surface. To investigate how different surface characteristics affect hydrological- and sediment connectivity on natural hillslopes, we studied five plots on two moraines of different ages in a proglacial area of the Swiss Alps. On all plots, we performed sprinkling experiments to determine OF characteristics, i.e., total OF, peak OF flow rate, peak turbidity and sediment concentrations, and total sediment yield. Here we test if a fluorescent sand tracer, together with UV lamps and a high-resolution camera, can be used to visualize the pathways of OF and to determine the typical sediment transport distances. The results highlight the ability of the setup to detect sand movement, even for individual fluorescent sand particles (300–500 µm grain size), and to distinguish between the two main mechanisms of sediment transport: OF-driven erosion and splash erosion. The experiments also revealed that the higher rock cover on the younger moraine enhanced surface hydrological connectivity and resulted in larger sediment transport distances. In contrast, the higher vegetation cover on the older moraine promoted infiltration and reduced the length of the surface flow pathways and erosion. The study, thus, demonstrates the potential of the new method to improve the observation of surface hydrological connectivity and sediment transport. These observations can help to improve our understanding of OF and sediment transport in complex natural settings.

Fabian Maier et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-165', Anonymous Referee #1, 01 Jun 2022 reply
    • AC1: 'Reply on RC1', Fabian Maier, 18 Jul 2022 reply

Fabian Maier et al.


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Short summary
Knowledge on overland flow generation and sediment transport is limited due to a lack of observational methods. Thus, we used sprinkling experiments on two natural hillslopes and tested a novel method using fluorescent sand to visualize the movement of soil particles. The results show, that the applied method is suitable to track the movement of individual sediment particles and the particle transport distance depends on the surface characteristics of the hillslopes.