Hydraulic structures, e.g. stilling basins, mainly use hydraulic jump to dissipate energy at the downstream of spillways, chutes and gates. In the present study, the effect of a hydraulic jump was examined by using experimental tests. To this end, several tests (60 tests) were performed for inflow Froude numbers within the range of 4 to 12 in a flume with a width of 35 cm. In these tests, rhombic roughness was installed and tested changing bed slope from 0 to 0.3 percent, and the parameters such as flow rate, initial depth, sequent depth, jump length of water surface profile, water head over spillway, and upstream water head were carefully measured. Data analysis showed that rhombic roughness can reduce the jump length to sequent depth ratio up to 35.5%. For a constant rhombic roughness, y2 / y1 ratio increases by 6.5%, on average, with increasing Froude number. For a constant Froude number, Lj / y2 ratio decreases by 1.2%, on average, when a rhombic roughness is installed.
