APPLICATION OF PHOTOGRAMMETRY IN FRESHWATER ECOLOGY: ANALYSING THE MORPHOLOGY OF A HIGH ALPINE FLOOD-PLAIN

The shape and structure of river channels (channel morphology) are important features of freshwater habitats. However, determination of parameters characterizing the morphology of rivers and flood-plains with classical methods is very time consuming and sometimes even impossible. The application of digital photogrammetry reduces the time for data acquisi-tion and allows analysis of complex and remote flood-plains: Aerial photographs capture a distinct flow situation, which can be analysed later in the laboratory with high accuracy and without time constraints. In this project, a digital elevation model (DEM) and color-infrared orthophotos were generated at a resolution (DEM: 2 m, Orthophoto: 0.25 m) that allowed the measurement of different morphological parameters of channels in the Val Roseg flood-plain (eastern Swiss Alps). Based on these photogrammetric data, channel area, channel length, mean channel width, channel slope, bank inclination, and riparian vegetation density were successfully calculated. The assessment of variabil-ity in width and slope of channel segments however was affected by the highly complex floodplain structure and the limited DEM resolution. Multivariate analysis showed, that the morphological parameters clustered the channel segments into different channel types, thus indicating the high ecological relevance of the results.