This study was carried out to evaluate the transport capacity equations of the Yalin equation and the WEPP model for steep slopes, and to recommend the best-fitting exponent value of shear stress in the WEPP transport capacity equation. The transport capacity was measured in a 5 m long, 0.4 m wide hydraulic flume, and the diameter of test sediment varied from 20 to 2000 m with a median diameter of 280 m. Flow discharge ranged from 0.625 10-3 to 5 10-3 m2 s-1, and slope gradient ranged from 8.8% to 46.6%. An averaged dimensionless critical shear stress of 0.052 was used for Tc calculation in the Yalin equation. The relationship between transport coefficient Kt and shear stress was graphically determined for the transport capacity equation of the WEPP model. The transport capacities predicted by the Yalin equation and the WEPP model were compared with the measured Tc to qualify their suitability on steep slopes. The results showed that the Yalin equation overestimated the measured Tc by 109%. The error increased as a power function of shear stress (r2 = 0.97). The transport capacity of the WEPP model underestimated the measured Tc by 65%. The absolute error increased as a linear function of shear stress (r2 = 0.91). Paired t-tests showed that the transport capacities calculated using the Yalin and WEPP equations were different significantly from measured Tc at the 0.05 level. Sediment transport coefficient Kt, calculated with the WEPP equation using the measured Tc of this study, varied with shear stress. However, Kt converged to a steady value of 0.053 when the best-fitting exponent of 2 for shear stress was used (r2 = 0.98). Thus, Ktt2 is considered when estimating Tc for steep slopes. More studies are needed to further evaluate the WEPP Tc equation as well as this new equation using various soils on steep slopes.