## 5 Conclusions  
This study developed a system for measuring flow-sediment movement and three-dimensional bedforms, collected data under various slopes and flow conditions, and analyzed the statistical distribution patterns of two-dimensional and three-dimensional bedforms characterization parameters. It also examined the characteristics of bedload transport on dune bedforms and assessed the impact of bedload transport on bed resistance. The major conclusions are stated as follows:The experiments demonstrated that the bedforms can evolve into two-dimensional and three-dimensional dunes under different slopes and flow conditions. The statistical analysis of bedform parameters, such as the dune length, the dune height, the crest height, and the trough depth exhibited that the dune length followed a lognormal distribution, whereas the dune height followed Gamma and lognormal distributions for the two-dimensional and three-dimensional bedforms, respectively. The crest height and the trough depth followed normal and Gamma distributions, respectively. These findings provide a quantitative framework for predicting bedform evolution.  
This study challenged the applicability of the traditional bedload transport formulas to dune bedforms and experimentally showed that the sediment transport rates calculated by these formulas significantly deviated from the measured values in the presence of dunes. A new bedload transport formula was proposed and derived from fitting the measured data using the nonlinear least squares method. This formula considers the relationship between bedload transport intensity and flow intensity, demonstrating high accuracy, with a comprehensive error of 0.016. This proposed formula is significant for improving the accuracy of the prediction of bedload transport rates.  
At high flow intensities, mass bedload transport significantly contributes to increased bed resistance. The dune height was positively correlated with bed resistance, whereas the influence of dune length on bed resistance was less significant. Although the dune height did not consistently increase with rising flow intensity, the increase in bedload transport notably contributed to bed resistance. This insight is crucial for understanding and predicting the sediment transport capacity of rivers.  
Conceptualization, W.C.; methodology, X.G. and C.L.; formal analysis, X.G. and G.Z.; data curation, X.G. and G.Z.; writing--original draft preparation, X.G.; writing--review and editing, X.G., W.C., C.L. and G.Z.; supervision, C.L.; project administration, X.G., W.C. and C.L.; funding acquisition, X.G., W.C. and C.L. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the National Natural Science Foundation of China (Grant Nos.: U2243218; 12072373), the China Institute of Water Resources and Hydropower Research (IWHR) Research & Development Support Programs (SE0145B022021), and the Yellow River Institute of Hydraulic Research (YRIHR) Science & Technology Development Foundation (HKF202307).  
Not applicable.  
Data Availability Statement: Data recorded in the current study are available in all tables and figures of the manuscript.  
All the authors would like to thank the editor and the expert reviewers for their detailed comments and suggestion for the manuscript. These were very useful to hopefully improve the quality of the manuscript.  
The authors declare no conflicts of interest.