A drag coefficient, lift coefficient and equivalent roughness are crucial factors for designing revetment and bed protection blocks of rivers. The drag coefficient and lift coefficient to specify the hydrodynamic forces acting on the blocks have been investigated for various types of concrete blocks mainly in sub-critical flow conditions. Although super-critical flow can be seen in steep slope rivers and downstream of weirs, authorized values for those coefficients have not been established in

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... uch flow condition. The coefficients measured in sub-critical flow are therefore applied in designing structures at present condition. In this study, the hydrodynamic force acting on concrete blocks and connected stones in super-critical flow conditions was experimentally investigated. Experimental results showed that the drag and lift coefficients for single setting in super-critical condition were a little bit larger than those for sub-critical condition and those coefficients for group setting were identical to the sub-critical condition.