Isbash Equation

$$D_{50} = \frac{V^2}{2 \times g \times C^2 \times (S - 1)}$$

Where:

• $D_{50}$ = Average diameter of 50% of the spherical rocks for the rip rap in meters
• $V$ = Average channel velocity in meters per second
• $g$ = Acceleration due to gravity ($9.806 \, \text{m/s}^2$)
• $C$ = Isbash constant (0.86 for highly turbulent flow, 1.20 for low turbulence flow)
• $S$ = Specific gravity of the rock (ranges from 2.50 to 3.00)