Experimental results of determining scour hole dimensions resulted from submerged circular jet in a plunge pool containing non-cohesive materials are presented in this paper. The effect of nozzle flow velocity, the height of nozzle installation and the bed particle diameters, are evaluated toward this end. Non-cohesive materials with average diameter of 4.06, 7.14, and 8.73 mm are used in this study. The elevation of jet installation toward the surface of plunge pool bed is changed with the values of 24, 35.5 and 44 cm. The nozzle flow velocity was differentiated between 2 and 10 meter per second. The comparison of observed results with previous studies show that the erosion parameter absolutely unable to normalized the effect of particle diameters, jet installation effect and nozzle flow velocity on the relative scour dimensions. The sensitive analysis on general introduced relations in this paper indicates that the variations of flow velocity and jet installation elevations has a double effect on estimating scour hole dimension in comparison to the material size and grading variations. The results also showed that armoring of the plunge bed has an important role in estimating relative parameters of scouring.