Bottom Friction

Bottom Friction

The mean (short-wave averaged) bed shear stress, $\tau _{bi}$, is calculated as

$\tau _{bi}=\lambda _{wc}\tau _{ci}$ (2-8)

where

$\lambda _{wc}=$ nonlinear bottom friction enhancement factor $\left(\lambda _{wc}\geq 1\right)$ [-]

$\tau _{c}=$ current-related bed shear stress vector [Pa]

The current bed shear stress is given by

$\tau _{ci}=\rho c_{b}UU_{i}$ (2-9)

where

$\rho =$ water density (~1025 kg/m³)

c_b = bed friction coefficient [-]

$U=$ current magnitude = ${\sqrt {U_{i}^{2}+U_{j}^{2}}}$ [m/s]