Influence of channel geomorphic units on bedload transport and river morphology during low-magnitude bed-forming floods coupled with sediment augmentation

In this study, we map different types of channel geomorphic units in a sediment-starved, residual-flow reach before and after an artificial flood. Bedload particles of a previous sediment augmentation measure are tracked with passive integrated transponder tags, and water depth and flow velocity are recorded across 10 cross-sections. The analysis focuses on the influence of channel geomorphic units on bedload transport and river morphology. Our hypotheses are (i) that during low-magnitude bed-forming floods with sediment pulse migration, existing channel geomorphic units influence bedload transport, and more specifically, (ii) that their type influences the retention rate of bedload particles. Furthermore, we hypothesise that (iii) the density of channel geomorphic units is linked to the hydromorphological diversity of a river section. We provide evidence that supports the first two hypotheses and contradicts the third one. We consider our results to be transferable to similarly regulated reaches based on an analysis of site-specific conditions and alternative explanatory factors. Further research is needed to transfer the results to varying flood and sediment supply conditions in unregulated reaches.