40 Structure from Motion in an alpine environment – evaluation of the method and assessment of channel topography change on the example of the mountain stream Ova dal Fuorn (Swiss National Park, SNP)

Thiex Daniel1/2, Wiesmann Samuel2, Seitz Steffen1

  1. Eberhard Karls University Tübingen, Department of Geography, Tübingen, Germany
  2. Swiss National Park, Zernez, Switzerland

Within the scope of his master thesis Daniel Thiex investigated streambed changes of a small mountain stream (Ova dal Fuorn) in the territory of the Swiss National Park (SNP). Mountain streams can experience big changes in their geomorphology due to natural events like heavy rainfalls during a thunderstorm. In the light of climate change, it is assumed that these severe weather events are more likely to happen on a higher frequency and more severe (Harb et al. 2013). Knowing about the magnitude of the changes caused by those events can be a first step in analysing them and in reaching a better understanding about their consequences.

To investigate the streambed around 750 aerial photos were taken with a drone and used to calculate a digital elevation model. The model was then compared with earlier models to identification active areas within the streambed (erosion as well as deposition) and quantify those. In a second step the work investigated the applied method, one that creates elevation models out of pictures (technical: Structure from Motion), closer.

Thanks to this work it could be shown that the Ova dal Fuorn lost material in the entire study area for the period 2003 – 2009, whereas for 2009 – 2018 a big increase could be observed. Main reason can be seen in one severe heavy thunderstorm in 2017, when the Ova dal Fuorn got dammed up by another stream leading to a lot of material being deposited at the confluence. On the methodology side it could be shown that Structure from Motion can be a useful tool to obtain high resolution digital terrain models on a centimetre scale in an alpine environment, making it a useful tool to create small-scale elevation models.

References

Harb, G., Schneider, J., Sass, O., Stangl, J., 2013. Sedimentfracht und Klimawandel in alpinen Einzugsgebieten (ClimCatch), in: Technische Universität Dresden, Institut für Wasserbau und technische Hydromechanik (Ed.), Technischer und organisatorischer 51 Hochwasserschutz - Bauwerke, Anforderungen, Modelle. Dresden. Dresdner Wasserbauliche Mitteilungen, pp. 297–305.