Wu et al.

The bed- and suspended-load transport formula of Wu et al. (2000) are given by

1)	$\begin{array}{l}q_{bk}^{*}=\begin{cases} 0.0053\sqrt{R_{k}gd_{k}^{3}}\left(\frac{\tau '_{b}}{\tau _{crk}}-1\right)^{2.2}\,\,\mathrm{for}\,\,\tau '_{b}>\tau _{ck}\\ 0\,\,\,\,\,\text{otherwise} \end{cases}\right.\,\,\,\end{array}$

2)

$\begin{array}{l}q_{sk}^{*}=\begin{cases} 2.62\times 10^{-5}\sqrt{R_{k}gd_{k}^{3}}\left[\left(\frac{\tau _{b}}{\tau _{crk}}-1\right)\frac{U}{\omega _{sk}}\right]^{1.74}\,\,\,\,\mathrm{for}\,\,\tau _{b}>\tau _{ck}\,\mathrm{and}\,\,\tau '_{b}>\tau _{ck}\,\,\,\\ 0\,\,\,\,\,\text{otherwise} \end{cases}\right.\end{array}$

where

$\begin{array}{l}{q_{bk}}^*\end{array}$ = fractional bed-load sediment transport potential [L²/T]

$\begin{array}{l}{q_{sk}}^*\end{array}$ = fractional suspended-load sediment transport potential [L²/T]

$\begin{array}{l}R_{k}\end{array}$ = $\begin{array}{l}ρ_{sk}/ρ_w−1\end{array}$ = submerged specific gravity of a particle [-]

$\begin{array}{l}ρ_{sk}\end{array}$ = sediment density [M/L³]

$\begin{array}{l}ρ_{w}\end{array}$ = water density [M/L³]

$\begin{array}{l}τ_{b}\end{array}$ = bed shear stress [M/L/T²]

$\begin{array}{l}τ'_{b}\end{array}$ = skin bed shear stress [M/L/T²]

$\begin{array}{l}τ_{crk}\end{array}$ = critical shear stress [M/L/T²]

$\begin{array}{l}d_{k}\end{array}$ = Sediment diameter [L]

Since the total bed shear stress is equal or larger than the skin bed shear stress, it is possible for the original formulation to produce suspended load without bed load. This situation is considered unrealistic and is avoided here by adding the additional condition in the above equation.