In study, effect of porous groins on flow hydrodynamics in a meandering compound channel was experimentally investigated. Porous groins constructed from gravel materials with porosity levels of 20%, 40% and 60% were evaluated. A three-dimensional acoustic velocimeter (ADV) was used to measure the velocity components in (x, y, and z) directions at 45000 points for three porous groins. The findings indicated that the structural porosity plays a key role in governing flow stability and stress distribution, making it a critical factor in the efficient design of flood control and sediment transport structures. Changes in the porosity of groins not only affect the magnitude of hydrodynamic parameters such as kinetic energy (TKE), Reynolds shear stress (RSS) and secondary flow power (S.F.P), but also play a significant role in altering the spatial distribution patterns of these parameters. The results showed that the maximum S.F.P, , u/U0, v/U0 and w/U0 at 20% porosity were 15.8%, 41%, 17.39%, 40% and 30% higher than those observed at porous groins of 40%, respectively. In addition, they were and 37.5%, 85%, 35%, 250% and 73.33% higher than those observed at porous groins of 60%, respectively. The results of Reynolds shear stress for three groins showed that the maximum shear stress in groin with 60% porosity is 66.67% and 75% higher than those with 40% and 20% porosities, respectively. Understanding the impact of porous groins on the complex hydrodynamics of flood flows in meandering compound channel is a crucial step towards developing effective strategies for erosion control, optimal flood management, and maintaining the stability of hydraulic structures under natural and extreme conditions.

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