River bed degradation in a compound channel after base level fall

Abstract

The bed degradation of a compound channel induced by a base level fall can significantly impact the flood conveyance capability and stability of riverine structures. This study found that severe compound channel degradation is due to the coupled effects of flood discharge and base level fall. Laboratory experiments examined the impact of base level fall on the grain size distribution at the bed surface, flow discharge in the main channel and floodplains, and longitudinal profile of the bed elevation. Two riverbed degradation patterns of a compound channel after base level fall were clarified. Relative to the original bed slope, degradation pattern (I) had a higher bed slope, but degradation pattern (II) had a lower one. A calculation method was proposed to determine the critical conditions for identifying these two riverbed degradation types. Both experimental and published data confirmed that the proposed method is valid for identifying these two compound channel degradation patterns.

KEYWORDS:

• Base level fall
• bed degradation
• compound channel
• critical condition

Acknowledgements

We sincerely appreciate the editor’s and reviewers’ constructive suggestions, which significantly improved the paper quality.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study received financial support from the National Natural Science Foundation of China [U20A20319, 52022063, and 52279074], the Sichuan Science and Technology Program [2023NSFSC1989] and the Fok Ying Tung Education Foundation [171067].