The relation of viscous force between different layers of fluid is given as,  $F=\eta A\frac{dv}{dx}=\eta A\frac{v}{H}$, here $\eta$ is the viscosity of water, $A$ is the area, and $\frac{dv}{dx}$ is the rate of change of velocity with the change in position.  

Shearing stress$= \frac{F}{A}=\eta \frac{v}{H}$.