ABSTRACT
Estimating the fine sediment budget in alpine rivers is an important challenge to better understand the morphodynamics of such rivers. In this paper, we describe the dynamics of fine-sediment deposits over a gravel bar before and after two flushing events in an alpine river based on pictures taken from the side of the river. These pictures are processed using a new image analysis method. It allows to estimate the spatial distribution of fine-sediment deposit on the gravel bar using photos taken at different dates. Photos before and after the flushing events in 2018 and 2019 were analysed. Comparison with the local in-situ measurement of surface grain size distribution has been carried out using the Wolman peddle count method. The image detection method presents a good agreement on the spatial distribution and variations of fine sediment deposits on the gravel bar with an acceptable bias. A discussion is provided on the limits and validation of the proposed method as well as on its applicability on medium term analysis.
