Bed Resistance Values == [ {MANNING N} | MANNING M | CHEZY ]
(Optional)
Sets the bed resistance formula to use. The default value is Manning’s n.
Depth/Ripple Height Factor Limit == [ {10} | ]
(Optional. Only used if bed resistance values are set to CHEZY)
Sets an upper limit on the ratio of the water depth over the ripple height in the formula for calculating Chezy values based on water depth. The value must be greater than 1/12, and if less than 1/12 is set to the default value of 10.
Read Materials File ==
(Optional. Presently only available for MANNING N based bed resistance values.
Can be extended to CHEZY and MANNING M upon request.)
Reads a text file containing Manning’s n values for different materials (land-use types). The file can contain comments using the “#” and/or “!” delimiters. A maximum of forty (40) materials is allowed – this can be increased upon request. In earlier versions the maximum was twenty (20).
The first number is the Mat (Material ID) number, which must be an integer. The second value is the Manning’s n value (see example below).
Optionally, as of Build 2005-05-AN, the third and fourth numbers set the initial and continuing loss rates in mm and mm/h if using Read MI SA Rainfall (see example below).
It is highly recommended that this approach be used, especially for model calibration. Editing this file is far easier than making changes to Manning’s n values in GIS layer(s).
The material values may also be used to define bed resistance values across 1D XZ cross-sections (see Section 3.13.5.2).
The file format is shown in the example below. See Set, Read MI and Read MID with the MAT option for setting the Mat values.
! Comments and blank lines are allowed in this file
! First value is the Mat value
! Second is the Manning's n value
! Maximum of 20 different materials
1, 0.03 ! waterways
2, 0.08 ! river banks
11, 0.06 ! grazing land
12, 0.04 ! parks and gardens
13, 0.15 ! sugar cane
14, 0.12 ! natural forest
15, 0.02 ! roads
To include the initial loss (mm) and the continuing loss rate (mm/h) optionally enter a third and fourth value as shown below. If an IL is specified, a CL must also be specified otherwise and ERROR occurs. Both can be omitted, in which case, they are both set to zero.
Warning: This command overwrites any previous “Bed Resistance Values” command by setting bed resistance values to CHEZY.
Sets the number of timesteps between recalculation of Chezy values based on the ripple height. The default value of zero indicates Chezy values are not recalculated (ie. remain constant throughout the simulation).