Overtopping is one of the major causes of dams and levees failure. There is uncertainty in estimation of the erosion parameters especially for coarse- grained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, results from a box test performed on three coarse grained materials in a 0.3-meter wide flume are discussed. The three materials share the same median grain size D50 of 2 mm, however, they vary in fines content between zero to 20%. The box measured 0.3 m wide x 0.6 m long x 0.15 m deep. Each of the three materials was compacted in the box at near optimum moisture content and dry density as determined from standard Proctor test. Each material was tested at varying hydraulic loadings to determine the erosion rate after equal time intervals. The water depth and velocity were measured at each hydraulic loading using Pitot tubes and the acting bed shear was calculated. The effect of fines content and level of acting shear stresses is discussed in the paper.