Abstract: Flow resistance in gravel-bed rivers is usually investigated by considering variation in relative roughness height
while relevant friction law for the porous permeable layers is not well understood. By applying Ergun equation
this study investigated the friction law of seepage through packed beds composed of glass beads. Different flow regimes were observed with varying head loss measured. The results show that the friction factor decreases with increasing Reynolds number and the data collected for different cases collapse almost into a single curve when the wall effects are considered. Finally an improved Ergun correlation is proposed to evaluate the flow resistance of packed permeable beds with small bed-to-particle ratios.