Abstract: Gravel materials are widely used in hydraulic structures such as self-spillway dams. Darcy’s law is used in engineering applications to represent flow through soil in this case the flow will be Laminar. When analyzing the flow through coarse porous materials such as gravel it leads to deviation in the results from Darcy’s law because of high velocity of flow that causes a nonlinear relationship between hydraulic gradient and bulk flow velocity. The present study aimed to investigate the behaviour of flow through monosized gravel and to determine the effect of hydraulic gradient and gravel mean size in hydraulic conductivity under turbulent flow condition. The porous materials used in this study were seven monosized gravel samples with diameters ranging from -4.75+4 to -31.5+25 mm. A hydraulic conductivity test rig was constructed to measure the hydraulic conductivity of the gravel samples. Hydraulic gradient values used to conduct the experiments ranged between 0.01 and 0.237 while the discharge values ranged between 0.0149 and 0.255 L/sec. The results showed that the flow through monosized gravel didn’t obey Darcy’s law and a strong non-linear relationship was found between hydraulic gradient and bulk flow velocity with average R² equal to a 0.99. Results also demonstrated that a strong power formula was found between hydraulic conductivity for monosized gravel and Reynolds number with average R² equal to a 0.97. In addition, the results showed that friction factor has high values at low Reynolds number and for Reynolds number equal to or >200, friction factor decrease and it reaches an approximately constant magnitude.