Abstract:The drawback of Shields diagram is that the unknown variables appear in both ordinate and bscissa parameters. For the convenience of practical use, Vanoni build auxiliary lines using a third parameter X, the use of this auxiliary lines enables to determine its intersection with the Shields diagram and its corresponding values of shear stress. To build the auxiliary line, it is necessary to drawθ-X curve, firstly. Reanalysis the parameter X, it is found that X is a function of dimensionless diameter d*(X=0.316d*1.5). So θ-X relationship can be deduced with Yalin-Silva θ-d* equation. Using the Yalin-Silva θ-d* equation and experimental incipient data, auxiliary lines are developed in this note for finding the critical shear velocity. Then, the auxiliary lines equation is gotten, the slope of auxiliary lines is verified mathematically, also. Finally, a new set of auxiliary lines are built in the rang of 0.01≤Re*≤1000, unlike the original Vanoni auxiliary lines, they lie on the top of θ=0.1 line in Re*<1 region.