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

Abstract

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 ten cross‐sections. The analysis focuses on the influence of channel geomorphic units on bedload transport and river morphology. Our hypotheses are that during low‐magnitude bed‐forming floods with sediment pulse migration, (i) 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.

Performance and accuracy of cross‐section tracking methods for hydromorphological habitat assessment in wadable rivers with sparse canopy conditions

“…There are no significant tributaries between the dam and the study reaches, so the water levels in both reaches were near-constant throughout the field surveys. More detailed descriptions of local environmental conditions and the river restoration context are provided in the literature (Mörtl et al, 2023;Schroff et al, 2022).…”