General System Parameters

The system parameters are specified at the top of the data file, an example of the structure of this section of the file is shown in Figure 2 (note that the heading '1234...' should not be included in the file).

Datafile Format (initial data block)

Where

Title = data file title of up to 40 characters. (If more than 40 characters are used then only the first 40 will be transferred to tabular and graphical results.) The first character must not be blank (ie not a space).

α = active layer thickness factor. The maximum active layer thickness is calculated as D95 multiplied by α. In calculating D95 size interpolation is used on an estimated or user defined D100 value. D95 is determined from the composition of the local parent bed material. Typical α values are 1 or 2 for flat beds, although a high value, eg 1000, will force greater mixing of active and sub-layers.

K = sediment transport equation calibration coefficient (set to 1 to get original equation)

λ = bed porosity (eg 0.4)

Δz_c = erosion/deposition depth change criteria to cause updating of channel geometry (m). For example, a value of 0.010m will mean that the section geometry is only updated after 0.010m of net erosion/deposition has been calculated. The criteria are applied independently at each channel node.

method = integer defining the method to update the channel geometry. Enter:

0 do not update section points

1 to move all section points at a node by a uniform Δ z

2 to move all section points at a node below the water surface by a uniform Δ z

3 to move those section points at a node below the water surface by a Δ z distributed according to local shear stress (water depth)

m = exponent used in method 3 to distribute changes in bed elevation around the cross section. Likely range is 0 to 2. A value of 0 will give a uniform distribution and 1 will weight erosion/deposition to the larger water depths. Only required to be present if method=3.

n= number of sediment sizes in the size distribution (between 1 and 10)

type = sediment transport calculation methodology. Enter:

COMPOSITE for no sediment sorting

SORTED for sediment sorting

See earlier section for guidance on how to select the appropriate algorithm.

di = sediment diameter (in mm) for size fraction i. They should be given in order of increasing size

ρi = sediment density (in kg/m3) for size fraction i. The density for size fraction 1 is used to represent the full distribution for some internal calculations.

stequ = sediment transport equation to be used for sediment size di. Enter one of the following codes:

1 Engelund-Hansen equation (1967)

2 Original Ackers-White equation (1973)

3 Revised Ackers-White equation (1993)

4 Westrich-Jurashek (1985)

7 Parker equation (1990)

10 Modified Parker equation (1990)

Pi = proportion of size fraction I in the size distribution (0 £ Pi £ 1 and S Pi = 1).

This distribution is the default for the bed material and the material entering at inflow boundaries. The bed material grading can be locally changed using a GRADING data block. The distribution at inflow boundaries can be set, if required, in the inflow data block.