
TAB is the table number of the cross section to be modified.
If a cross section with the given table number appears in
subsequent input in FEQX, FEQXLST, or FEQXEXT, then that cross
section is analyzed applying the information in the remainder
of the line to define a floodway crosssection table. If a
table number is given in TAB and no subsequent cross section
with a matching number is present in the input, then the
information is read but not used. If a cross section is input
without an entry in the floodway table, then the cross section
is processed as usual. The input is terminated by assigning a
negative value for the table number.
OPT specifies the options for modifying the cross section.
Valid options are ELEV, CONV, and USET.
The data required in the following fields depend on which
option is selected.

If OPT = ELEV

ELEV is the watersurface elevation applied to compute the
conveyance in the cross section. Normally, the watersurface
elevation corresponding to the 100year flood is utilized. The
elevation in ELEV must be specified, and it is an error if the
value given in ELEV is lower than the minimum point of the
cross section or higher than the last point on either the left
or the right end of the crosssection boundary description.
BOT is the elevation of the bottom of the cross section as
specified in the profile in the FEQ schematization of the
stream. This must be given only if it differs from the
elevation of the minimum point in the crosssection boundary
description. If left blank, the bottom profile given in the
FEQ schematization for this cross section matches the minimum
elevation in the crosssection boundary description. The
symbol `same' is printed if the field is left blank.
LEFT is the limit of the encroachment from the left of the main
channel. If an offset is to the left of LEFT (that is, farther
from the main channel) is computed in the floodwayboundary
determination, then that offset is retained. However, if the
offset computed for the definition of the floodway is closer to
the main channel than LEFT, the floodway boundary is limited to
LEFT. In a case where the value in LEFT overrides the computed
left boundary of the floodway, the decrease in the
standardflood elevation requested in LOSS is not attained, and
the user must examine the FEQUTL output to determine what
portion of the requested decrease was attained. If this
information is left blank, the encroachment is unlimited and
the symbol '+inf', denoting positive infinity, is
printed as the limit.
RIGHT is the limit of the encroachment from the right of the
main channel. RIGHT serves the same function as LEFT, but for
the right side of the main channel. If this information is
left blank, the encroachment is unlimited and the symbol 'inf',
denoting negative infinity, is printed as the limit.
LOSS is a decrease from the standardflood elevation given in
ELEV. For example, if the floodway is to start at an elevation
of 672 ft above sea level and the standardflood elevation is
672.7 ft above sea level, then the value in the LOSS column
should be 0.7 ft. If the LOSS column is blank, the global
value of the decrease (Line 3) is applied.
 If OPT = CONV

ELEV is the watersurface elevation applied to compute the
conveyance in the cross section. Normally, the watersurface
elevation corresponding to the 100year flood is utilized. The
elevation in ELEV must be specified, and it is an error if the
value given in ELEV is lower than the minimum point of the
cross section or higher than the last point on either the left
or the right end of the crosssection boundary description.
BOT is the elevation of the bottom of the cross section as
specified in the profile in the FEQ schematization of the
stream. This must be given only if it differs from the
elevation of the minimum point in the crosssection boundary
description. If left blank, the bottom profile given in the
FEQ schematization for this cross section matches the minimum
elevation in the crosssection boundary description. The
symbol 'same' is printed if the field is left blank.
LEFT is the limit of the encroachment from the left of the main
channel. If an offset that is to the left of LEFT (that is,
farther from the main channel) is computed in the
floodwayboundary determination, then that offset is retained.
However, if the offset computed for the definition of the
floodway is closer to the main channel than LEFT, the floodway
boundary is limited to LEFT. If the computed value for left or
right floodway boundary corresponding to the requested
reduction in conveyance is overridden by the input boundaries
of the floodway (LEFT or RIGHT), the user must examine the
FEQUTL output to determine what part of the requested reduction
in conveyance was attained. Thus, if the specified value of
LEFT results in a 3percent reduction in conveyance on the left
side of the channel, the requested reduction in conveyance is
10 percent, and the specified value of RIGHT is not limiting,
then only 8 percent of the requested 10percent reduction in
conveyance is attained. If this information is left blank, the
encroachment is unlimited and the symbol '+inf',
denoting positive infinity, is printed as the limit.
RIGHT is the limit of the encroachment from the right of the
main channel. RIGHT serves the same function as LEFT, but for
the right side of the main channel. If this information is
left blank, the encroachment is unlimited and the symbol 'inf',
denoting negative infinity, is printed as the limit.
LOSS is the loss of conveyance utilized to determine the
encroachment limits for the floodway. This loss value is
evenly divided between the left and the right sides of the
channel. If the LOSS column is blank, the global value of the
reduction in crosssection conveyance
(Line 2) is applied.
In both the ELEV and CONV options, the values of BOT, LEFT, and
RIGHT are optional and may be left blank if the default values
are suitable. LEFT and RIGHT can be applied to preserve a
specified floodway width because these values always override
any computed encroachment inside the specified limits.
 In OPT = USET

ELEV is the watersurface elevation applied to compute the
conveyance in the cross section. Normally, the watersurface
elevation corresponding to the 100year flood is utilized. The
elevation in ELEV must be specified, and it is an error if the
value given in ELEV is lower than the minimum point of the
cross section or higher than the last point on either the left
or the right end of the crosssection boundary description.
BOT is the elevation of the bottom of the cross section as
specified in the profile in the FEQ schematization of the
stream. This must be given only if it differs from the
elevation of the minimum point in the crosssection boundary
description. If left blank, the bottom profile given in the
FEQ schematization for this cross section matches the minimum
elevation in the crosssection boundary description. The
symbol 'same' is printed if the field is left blank. In this
case, specification of BOT is optional.
LEFT is a fixed left boundary for the floodway encroachment,
which must be specified in this option.
RIGHT is a fixed right boundary for the floodway encroachment,
which must be specified in this option.
LOSS is not required in this option.
