7.9 Materials

7.9.1 Command Status

Optional - Additional material properties may be added to the 2D HD simulation class material definition.

7.9.2 Description

A subset of the commands described previously are also available for application on a material by material basis. This allows for spatial variation in the specification of some advection dispersion related model parameters. These commands are issued and interpreted within a material block in the same manner in which bottom roughness is spatially specified (see Section 5.14). Using scalar diffusivity as an example, this specification takes the following form.

! Define material scalar diffusivity
Material == 4 ! Material ID
Horizontal Scalar Diffusivity == 0.7 ! {0.0} Horizontal scalar diffusivity (m^2/s)
Horizontal Scalar Diffusivity Limits == 1.0, 99999. ! {0.0} K_d_min (m^2/s), K_d_max (m^2/s)
Vertical Scalar Diffusivity Limits == 0.01, 99999. ! {0.0} K_d_min (m^2/s), K_d_max (m^2/s)
End Material

In spatially varying advection dispersion properties via materials, the following apply.

The material numbers and extents used for advection dispersion commands are the same as those used for related parameterisations such as bottom roughness. For example, if material 4 is sufficient for roughness in one area but advection dispersion behaviour needs two subareas, material 4 must be subdivided into two material coverages. These coverages require different material numbers and advection dispersion properties, but retain the same roughness properties.
As for the specification of bottom roughness, the order in which advection dispersion related material commands are specified is important. Material related commands overwrite any prior spatially coincident commands.
Multiple materials can be specified in a single material block to avoid repetition

The commands available for material based specification of advection dispersion properties are presented in Table 7.20.

Table 7.20: **Material Properties Commands**
Command	Description
Horizontal Scalar Diffusivity	Optional - Assigns a material specific horizontal scalar diffusivity coefficient or value. Overrides the Global Horizontal Scalar Diffusivity command.
Horizontal Scalar Diffusivity Limits	Optional - Assigns material specific horizontal scalar diffusivity limits. Overrides the Global Horizontal Scalar Diffusivity Limits command.
Vertical Scalar Diffusivity Limits	Optional - Assigns material specific vertical scalar diffusivity limits. Overrides the Global Vertical Scalar Diffusivity Limits command.
Shortwave Radiation Extinction Coefficients	Optional - Assigns material specific fractionation of shortwave radiation into PAR, UVA, UVB and NIR. Overrides the global command.