**6. Conclusions**

In order to investigate secondary flow effects on cohesive sediment deposition in a meandering reach of the Yangtze River, a 2D depth-averaged model (N model) has been improved to consider different impacts of secondary flow and cohesive sediment transport. The improved 2D model includes three different submodels, that is, the Lien (L) model [37], with a wide application in literature; the Bernard (B) model [35], considering the phase lag effect and sidewall boundary conditions of secondary flow; and a nonlinear (NL) model [1] accounting for the saturation effect of secondary flow in sharp bends. All of the models can reflect velocity redistribution caused by secondary flow to a certain degree. A module for cohesive sediment transport has been coupled into the N model as well. The simulation results are as follows.


**Author Contributions:** Conceptualization, C.Q. and X.S.; methodology, C.Q.; software, C.Q.; validation, C.Q.; formal analysis, C.Q.; investigation, C.Q.; resources, Y.X.; data curation, Y.X.; writing—original draft preparation, C.Q.; writing—review and editing, X.S.; visualization, C.Q.; supervision, X.S.; project administration, X.S.; funding acquisition, X.S.

**Funding:** This research was funded by the National Key R&D Program of China (2018YFC0407402-01).

**Acknowledgments:** The authors would like to thank Baozhen Jia for her helpful advice and discussion about this paper and Yanjun Wang for the formation of the ideas about this paper.

**Conflicts of Interest:** The authors declare no conflict of interest.
