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RD CARD
ROUGHNESS ASSIGNMENT BY DEPTH
RD CARD
Field
Variable
Value
Description
0,C1-2
IC1
RD
Card group identifier
0,C3
IC3
b/
Option 1: Universal assignment for entire grid.
T
Option 2: Assignment by element material type (KMAT)
1
ISTART
+
First value for the global assignment to begin. Element material type or
element number as indicated by the value of IC3.
2
IRUFF
0,+
ON/OFF switch for auto Manning'N-value calculations based upon
the local depth. Negative or zero turns the option off. Positive value
turns the option on and sets the defaults as in the table below.
3
RDRO
0,+
N-value for non-vegetated water. If IZBA = 0, this should be a
maximum value. If IZBA = 1, this should be an average value. Any
positive number will override the default for RDR0.
4
RDDO
0,+
Depth at which vegetation effects roughness. Any positive number
will override the default for RDD0.
5
RDRM
0,+
N-value for vegetation water. Any positive number will override the
default for RDRM (NOTE: RDRM = 0 for all 3-D elements).
6
RDCOEF
0,+
Roughness by depth coefficient in the following equation: (positive
value will override the default)
7
IZBA
0,1
Toggle for automatic assignment of RDCOEF based on the
instantaneous depth to roughness height ratio. A value of 0 deactivates
the option. A value of 1 activates the option.
NVALUE=RDRO/(DEPTH**RDCOEF)+(RDRM*EXP(-DEPTH/RDDO))
NOTE: Default parameters are set depending on the value of IRUFF:
=1
settings for the Miss. River Delta project:
RDRO=.02
RDDO=2.0
RDRM=.026
RDCOEF=.08
=2
settings for S-shaped River example test case
RDRO=.04
RDDO=4.0
RDRM=.040
RDCOEF=.166667
=3
settings for San Francisco Bay Estuary project
RDRO=.04
RDDO=2.0
RDRM=.040
RDCOEF=.166667
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