**6. Conclusions**

The present study investigates the clear-water and live-bed scour characteristics at complex bridge piers in close proximity to each other with four different pier arrangements: side-by-side arrangemen<sup>t</sup> with aligned flow, side-by-side arrangemen<sup>t</sup> with 30◦ skew angle, a staggered arrangement, and a tandem arrangement. The main conclusions drawn from the paper include:


attention should still be paid to the side-by-side piers with aligned flow, for which there is a risk with high flow intensity of higher scour than the method predicts.

6. Due to the complexity of predicting scour depth at complex piers, the conclusions drawn in the present study should be integrated with other factors that may also influence the scour pattern, e.g., the proximity to other artificial structures or natural topography, general bed level variation and channel bends.

**Author Contributions:** Conceptualization, Y.Y. and B.W.M.; Formal analysis, Y.Y. and G.H.M.; Investigation, Y.Y.; Methodology, Y.Y.; Supervision, B.W.M.; Validation, Y.Y.; Visualization, Y.Y.; Writing–original draft, Y.Y.; Writing–review & editing, Y.Y., B.W.M., G.H.M., and A.Y.S.

**Funding:** This research was funded by China Scholarship Council (CSC).

**Acknowledgments:** The authors would like to thank the technical support provided by the Fluid Mechanics Laboratory of The University of Auckland as well as the sta ff, including Geo ffrey Kirby, Dan Fray, and Oane Galama. In particular, the first author would like to thank Yu Huang for her precious help during the past years.

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