The Effect of the Pick Angle of Spur Dikes on the Ecological Riverbed Evolution Within a 180° Bend.

The rational layout of spur dikes has a significant impact on the flow structure, patterns of fluvial erosion and deposition. In addition to serving as a protective measure for riverbanks, these dikes also play a role in promoting the formation of various riverbed features, such as deep pools and shallow shoals nearby. These unique characteristics create a rich habitat for aquatic organisms, thereby enhancing ecological sustainability and development. Using the computational fluid dynamics (CFD) technique and the RNG k--ε model for parameter calibration and verification, this study undertakes a rigorous investigation into the hydrodynamic properties and the fluvial erosion-deposition processes occurring in the vicinity of spur dike units with diverse deflection angles situated at the concave bank of a 180° bend. The results indicated that, in relation to energy dissipation and water level fluctuations, the spur dike with a 90° deflection angle exhibited the most prominent characteristics, yielding the greatest water level disparities and the most significant energy losses. The spur dike exhibiting an upward deflection angle occupied a secondary position, whereas the spur dike with a downward deflection angle demonstrated the least notewor- thy effects. Furthermore, a positive correlation was identified between vortex intensity and the degree of riverbed erosion and deposition. Counterclockwise vortices contributed to deposition, whereas clockwise vortices were prone to cause erosion. In terms of the distribution of shear stress, the scope and magnitude of the intense shear stress zones formed at the head of the spur dike and on the opposite bank exhibit a distinct pattern where the spur dike with a 90° deflection angle shows the largest impact, followed by the upward deflection spur dike, and the downward deflection spur dike demonstrates the smallest impact. So, the selection of deflection angles for spur dikes significantly influences riverbed scouring and deposition, water flow characteristics, and ecological outcomes. It is crucial to scientifically and rationally design and arrange spur dikes to achieve a balance between controlling riverbed scouring and deposition, preserving ecological balance in river channels, and ensuring the safety of engineering projects. [ABSTRACT FROM AUTHOR]