Bulk properties refer to properties of the sediment-water mixture. Bulk properties usually refer to sediment bed properties such as porosity, bulk densities, and erodibility parameters. The erodibility parameters are discussed in a subsequent section while the porosity and bulk densities are covered below.

Density

The wet bulk density is density of the water-sediment mixture and is defined as

where

$//<![CDATA[ \begin{array}{l}m\end{array} //]]>$ = mass of water-sediment mixture [M]

$//<![CDATA[ \begin{array}{l}m_{w}\end{array} //]]>$ = water mass [M]

$//<![CDATA[ \begin{array}{l}m_{s}\end{array} //]]>$ = sediment mass [M]

$//<![CDATA[ \begin{array}{l}V_{}\end{array} //]]>$ = total volume of sediment mixture [L³]

The wet bulk density is usually utilized for describing the density of the transported water-sediment mixture. Given a fractional sediment concentration with varying grain densities, the density of the water-sediment mixture can be computed as

where

$//<![CDATA[ \begin{array}{l}ρ_{m}\end{array} //]]>$ = water-sediment mixture density [M/L³]

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

$//<![CDATA[ \begin{array}{l}c = ∑_kc_k\end{array} //]]>$ = sediment volume concentration [-]

$//<![CDATA[ \begin{array}{l}ρ_{sk}\end{array} //]]>$ = grain class particle density [M/L³]

$//<![CDATA[ \begin{array}{l}c_{k}\end{array} //]]>$ = grain class (fractional) volume concentration [-]

Wet bulk densities can vary from 1330 kg/m³ to 2230 kg/m³.

Viscosity

Thomas (1965) proposed the following equation for the water-sediment mixture viscosity

where

$//<![CDATA[ \begin{array}{l}μ_{m}\end{array} //]]>$ = water-sediment mixture viscosity [M⋅T/L]

$//<![CDATA[ \begin{array}{l}μ_{w}\end{array} //]]>$ = water viscosity [M⋅T/L]

$//<![CDATA[ \begin{array}{l}c\end{array} //]]>$ = sediment volume concentration [-]

The above equation has an accuracy of 97.5% for c < 0.25%.