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The successful stabilization of riverbanks and the construction of sustainable foundations, extensive knowledge of the scour process and accurate assessment of scour depth around spur dikes are required. This study focuses on optimizing the spur dike shape to manage flow turbulence effectively and minimize local scour while considering the impact of downward seepage. The investigation was conducted within an experimental flume featuring a mobile bed under a clear water regime and the provision for downward seepage. The investigation concentrated on three distinct spur dike shapes (T, L, and rectangular) under different seepage velocities (VS1 and VS2) and a no-seepage condition. The current study also illustrates changes in bed morphology, temporal evolution and longitudinal profile of scour depth with and without downward seepage. The results reveal that the downward seepage intensifies the motion of sediment particles, and more seepage leads to an escalated particle detachment, resulting in deeper scour depressions. The T-shaped spur dikes exhibited the lowest scour depths compared to the other shapes, both with and without seepage. The negative impact on velocity and RSS magnitude was observed at the near channels bed where maximum scour depth was achieved. This phenomenon is closely linked to horseshoe vortices’ formation and current generation. These factors play a pivotal role in the detachment of particles from the base of the structure.

In this paper, the significance of the shape of spurs on flow and bed morphology is understood, accompanied by an appeal to investigate alternative shapes like L-head, T-head spurs, and hockey-shaped spurs, which could offer considerable benefits for river management. The spurs with T-head shape are found to be more efficient in reducing the bed scouring of the channel relatively, although it depends on the orientation of the spur, location of installation, and shape of the channel. Furthermore, development of horseshoe vortex is found insignificant near the base of the T-head spur dike. T-head spurs could more effectively redirect flow and prevent erosion while L-head spurs may enhance riverbank stability. This highlights the need for more investigation into how different spur shapes collectively affect river morphology, flow velocity, and sediment transport patterns. Temporal variations in bed morphology, especially the scour depth and sediment transport dynamics near spur dikes, should also be investigated to understand their changing impact better. Finally, this study provides a complete summary of existing knowledge gaps and future research initiatives relevant to various shapes of spur dikes and their role in riverbank erosion management. HIGHLIGHTS Review the shape of the spurs installed for the river bank protection.; There is a need of investigation into how different spur shapes collectively affect river morphology.; T-head spur dike shows significant development of vortex at its base.; L-head spurs show better riverbank stability.; Present work analyses the design principles of various shaped spurs.;

Abstract The present work experimentally analyses the flow behaviour near the T-shaped spur dike field with no seepage, 5%, and 10% downward seepage. Experiments were aimed at analysing the channel morphology with different discharges. According to the results, downward seepage movement causes significant modification in the channels bed elevation and the development of scour depth. The maximum scour depth is observed at the edge of the first spur dike facing the flow. The rate of scouring also increases with the effect of seepage. Due to downward seepage, the flow distribution is shifted near the channel bed. However, near the channel boundary attained some velocity, significantly enhancing the sediment transport rate. The wake zone between the spur dikes saw very low-velocity magnitudes of positive and negative values. This reveals secondary current generation inside the loop and cross-stream circulation. With an increment of seepage percentage, the velocity, Reynold shear stress, and turbulent kinetic energy magnitude also rise close to the channel’s boundary.

Flow in streams and rivers typically erodes the banks, causing channel bank migration laterally, resulting in loss of nearby land, modification in channel morphology, excessive sediment transport, and water quality degradation. A spur dike is a hydraulic structure placed at the channel bank projecting outward to guide or divert the flow away from the bank, thus protecting it from erosion. The stability of the riverbed and banks is influenced by turbulent characteristics such as three-dimensional velocity distribution, turbulent kinetic energy, Reynolds shear stress, turbulent intensity, and bed shear stress. The researchers found that these turbulence parameters are instrumental in sediment movement along the channel's bed and from its banks. Spurs dikes are a significant river training structure provided along the river bank to protect from erosion. Several aspects related to spur dikes, such as their geometry, physical features, design considerations, flow and scour patterns, etc., are critically reviewed in this paper. Despite the numbers of literature in the field of turbulent characteristics and scour depth around spur dike, the role of vegetation and the effect of seepage around spur dike still remains an unexplored area. These knowledge gaps of spur dikes in field conditions are discussed for future studies. HIGHLIGHTS Assessment of spur performance for bank erosion control.; Details of spur types and design criteria discussed.; The gaps in current knowledge about spurs identified.; Future research direction regarding the effect of seepage and vegetation on spur performance is presented.;