These settings include variables that will remain constant for a
GeoFluv™ design, e.g., precipitation event values, and other detail
settings specific to a GeoFluv™ design area that the user will
typically not change for each design iteration.
The Settings button at the top of the Design GeoFluv Regrade dockable dialog box provides a convenient way for the user to access all these settings in one place. The Settings button is accessible at any time. Left-clicking on the Setup tab's Settings button opens the Natural Regrade Global Settings dialog box. Each of the settings is described below.
Maximum distance between connecting channels (ft.): This is a drawing setting that defines a maximum separation of polylines that Natural Regrade will recognize as channel polylines. The maximum distance should be set as small as the user can comfortably draw. The user types this value into the edit box. Some users may be able to hold and click the cursor more accurately than other users and this setting accommodates those differences.
Maximum distance from ridge
line to channel's head (ft.): This is an essential local variable in the
GeoFluv™ approach. It is the shortest distance from a ridgeline to
the head of a stable channel. The user will determine this value,
in the vicinity of the GeoFluv project, for stable landforms that
developed in earth materials similar to the disturbed earth
materials within the GeoFluv™ boundary. The value is a function of
local factors including soil cohesiveness, vegetation canopy,
cover, and root density, storm intensity and other climatic
factors, and topographic relief. The user types this value into the
edit box. The 80-foot default value is for an erosive semi-arid,
high-altitude desert region in the southwestern United
States.
Maximum Distance for Subridge: The user can vary the Global sub-watershed ridge length in the Natural Regrade Global Settings dialog. The sub-watershed ridges and swale valleys form by similar processes of erosion as do the channel-containing valleys, but the watershed area above them is not great enough to generate discharges that form defined channels. This means that in some areas the landform dimensions of these smaller features may have greater convex lengths than in channel-sized valleys. The user can input a maximum convex length for the sub-watershed ridges that will be applied globally in the GeoFluv design by typing the desired value in the edit box; the remainder of the profile will be concave when possible. The swale distance setting is not changed when the sub-watershed ridge setting is manually input.
Maximum Distance for Swale: The user can vary the Global
sub-watershed swale length in the Natural Regrade Global Settings
dialog. The
sub-watershed ridges and swale valleys form by similar processes of
erosion as do the channel-containing valleys, but the watershed
area above them is not great enough to generate discharges that
form defined channels. This means that in some
areas the landform dimensions of these smaller features may have
greater convex lengths than in channel-sized valleys. The user can input a maximum
convex length for the sub-watershed swales that will be applied
globally in the GeoFluv design by typing the desired value in the
edit box; the remainder of the profile will be concave when
possible. The
sub-watershed ridge distance setting is not changed when the swale
setting is manually input.
Slope at the mouth of the main valley bottom channel (%): This setting, along with the Channels tab's "Advanced...Specify mouth elevation." setting, may be the most critical value to creating a stable final landform design using the GeoFluv™ approach. The GeoFluv™ design must integrate with upstream and downstream areas to achieve stability. That means that GeoFluv™ channel reaches must have longitudinal profiles that blend smoothly with up-and downstream channel reach profiles. The user will determine the slope downstream of the mouth of the main valley bottom channel by survey, e.g., a point every 25 feet for about 400 feet. The user can plot a longitudinal profile from these points and select an input value for the channel slope upstream that will blend smoothly into the downstream profile. The user types this value into the edit box.
In some cases, disturbance may continue for a great distance
downstream of the GeoFluv™ boundary. In those cases, the user
must
determine the slope at the eventual downstream, undisturbed tie-in
point, extend that profile upstream to the GeoFluv™ boundary,
and specify a smooth tie-in slope value.
"A" channel reach (ft.): This is an essential local variable in the GeoFluv™ approach, and reflects many of the same local variables as does "Maximum distance from ridge line to channel's head" above. It is one-half of a meander length. The user will determine this value for stable landforms, in the vicinity of the GeoFluv™ project, that developed in earth materials similar to those within the GeoFluvTM boundary. The user types this value into the edit box.
2-yr, 1-hr (in.) (see documentation): This is where the user inputs the precipitation value for the storm event that determines the bankfull channel dimensions and plan-view channel geometry. This is an essential local variable in the GeoFluv™ approach. The GeoFluvTM approach uses a 2-yr, 1-hr storm event to design these features for ephemeral upland channels, and it can be used for ungauged intermittent and perennial channels as well. The value can be typed into the edit box, or entered by using the Rain Map button for sites in the U.S. and Puerto Rico.
Clicking on the Rain Map button produces a dialog box in which the user will select the state or territory of interest, and the storm frequency and duration using dropdown menus. When the user selects a state or territory, Rain Map zooms in to that selection. The user then moves the cursor to the GeoFluv™ project area, left-clicks on it, and the interpolated value is entered into the "Rainfall (in.)" field in Rain Map. When the user clicks on the OK button at the bottom of the Rain Map dialog box, the dialog box closes and the rainfall value is automatically entered into the Natural Regrade Global Settings precipitation event edit box (next to the Rain Map button).
If the user has data from a stream gauging station sufficient to determine the discharge associated with an annual recurrence interval (bankfull) event, they can directly enter that value into GeoFluv™ using the "Channels" tab's "Advanced . . ." button and "Use manual Qpk.". The user is cautioned that increasing these values beyond the actual event value will not create a "design safety factor", but rather will create a channel that is not competent to transport sediment during more frequent, lower-discharge events, i.e., it will cause sediment deposition in the channel that can cause channel blockage, etc.
50-yr, 6-hr (in.) (see documentation): This is where the user inputs the precipitation value for the storm event that determines the flood-prone channel dimensions. This is an essential local variable in the GeoFluv™ approach. The user can input the value using methods discussed in the "2-yr, 1-hr" section above.
The dominant channel morphology has been shown to be related to about a 50-year recurrence interval event, rather than some extreme 100-year, 200-year, probable maximum, or other event. The GeoFluv™ approach uses an intense 50-year event to design the flood prone area of the channel and places the entire amount of the 6-hour storm into the channel instantaneously to calculate a peak discharge associated with extreme channel-forming events. All this discharge is contained within the channel banks in Natural Regrade's default GeoFluv™ channel design. The user can also design a floodplain or terrace adjacent to the channel to accommodate greater discharges; when these are relatively wide the tremendous increase in cross sectional area allows the additional discharge to spread across the surface without causing undesirable erosion.
Target drainage density (ft./ac.): This is an essential local variable in the GeoFluv™ approach. It is the total valley length divided by the area within the GeoFluv™ boundary. The user will determine this value for stable landforms, in the vicinity of the GeoFluv™ project, that developed in earth materials similar to those within the GeoFluv™ boundary. (Refer to Introduction section for more detail.) It is a function of local factors including soil cohesiveness, vegetation canopy, cover, and root density, storm intensity and other climatic factors, and topographic relief. It is the extent to which a drainage network will develop given those local factors to achieve a stability comparable to surrounding land areas. The user types this value into the edit box.
Target drainage density variance (%): This is an essential local variable in the GeoFluv™ approach. It captures the range of acceptable drainage density values for the GeoFluv™ project area based on the range of locally-measured drainage density measurements as described above and in the Introduction section. For example, if the lowest drainage density value that the designer has determined can be stable is 80 feet/acre and the highest drainage density value that is measured in similar local earth materials is 120 feet/acre, the user could set a target drainage density value of 100 feet/acre and a target drainage density variance at 20 percent to capture that locally-determined range of 80 to 120 feet/acre. The user types this value into the field.
Force ridges to be lower than
GeoFluv boundary: This toggle setting allows the user to
specify if any point on a main ridge line can be higher than where
the ridge line meets the GeoFluv™ boundary. A main ridge line in
the GeoFluv™ approach is a ridge that defines a subwatershed divide
within the GeoFluv™ boundary. When this box is checked (toggled
on), the elevations on the main ridgeline will all be lower than
the elevation on the GeoFluv™ boundary where the main ridgeline
intersects the GeoFluv™ boundary. When this box is left blank
(toggled off), a ridgeline may have a high point of greater
elevation than the GeoFluv™ boundary, e.g., creating a knob or
butte feature. In this case all runoff will still remain within the
GeoFluv™ boundary and exit at the mouth of the main valley bottom
channel. The feature allows the user to create a topographic
feature within the GeoFluv™ boundary that may vary from the
pre-disturbed surface, but is still a stable landform. This can be
used to minimize the movement of piles of earth material when
creating a stable landform design.
Angle from subridge to channel's perpendicular, upstream (deg.): This is a local variable in the GeoFluv™ approach. This is the angle that subridgelines make in the upstream direction from the valley bottom to the main ridgeline. The user will determine this value for stable landforms, in the vicinity of the GeoFluv™ project, that developed in earth materials similar to those within the GeoFluv™ boundary. Setting this value similar to surrounding stable landforms will help the GeoFluv™-designed landform blend harmoniously with surrounding natural landforms. Natural Regrade will automatically create all the subridges in the draft landform using this value. The user can edit individual ridgeline orientations from the draft landform to suit site-specific design needs, however, Natural Regrade's ability to create the subridges and subridge valleys saves the user a tremendous amount of design time when producing draft landform designs. The user types this value into the edit box.
North or East straight-line slopes (%): This setting allows the user to specify a global target for a maximum ridge-to-toe slope profile steepness on the north- and east-facing slopes (between 315 and 135 degrees). The north and east-facing slopes are generally steeper in natural landforms because they get less sun and can retain more moisture, factors that favor tree growth and its associated root-binding of slope soils. Because the slope faces can contain an infinite degree of aspects in the GeoFluv™ approach, Natural Regrade does not produce the identical slope angle for all north or east-facing slopes with this setting; it is rather a best-fit slope adjustment toward the specified target value. The user should remember that changing the slope on one side of a ridgeline will affect the slope on the other side of the ridgeline. The user types this value into the edit box.
Maximum straight-line slopes (%): This setting allows the user to specify a global target for a maximum ridge-to-toe slope profile steepness on all slopes within the GeoFluv™ boundary. As in "North or East straight -line slopes" above, it is impractical for Natural Regrade to control every area of the design with this setting; it is a best-fit slope adjustment toward the specified target value. The user should remember that changing the slope on one side of a ridgeline will affect the slope on the other side of the ridgeline. The default value is 33 percent because agricultural machinery commonly in use for land reclamation has difficulty working across steeper slopes. The user types this value into the edit box.
Maximum cut & fill variance (%): This setting allows the user to specify a global maximum for the cut and fill material balance for the GeoFluv™ design surface as compared to another surface, e.g., Pre-disturbed surface. A value of 100 percent means cut and fill are balanced. A value of 125 percent means that there is 25 percent more material that needs to be removed to create the surface than there are areas requiring fill. The user types this value into the edit box.
Minimum cut & fill variance (%): This setting allows the user to specify a global minimum for the cut and fill material balance for the GeoFluv™ design surface as compared to another surface, e.g., Pre-disturbed surface. A value of 100 percent means cut and fill are balanced. A value of 80 percent means that there is 20 percent less material that needs to be removed to create the surface than there are areas requiring fill. The user types this value into the edit box.
Cut swell factor: This setting allows the user to specify a global swell factor for cut material from bank volume to loose volume. A value of 1.000 means that the loose volume is the same as the bank volume. A value of 1.120 means that the excavated loose material fills 12 percent greater volume than did the same material in place before excavation. The user types this value into the edit box.
Fill shrink factor: This
setting allows the user to specify a global shrink factor for fill
material from loose volume to fill volume. A value of 1.000 means
that the fill volume is the same as the loose volume. A value of
0.900 means that the filled and settled/compacted material fills 10
percent less volume than did the same loose material after
excavation. The user types this value into the edit box.
Channel head elevation tolerance: Natural Regrade
alerts the user via pop-up dialogs when channels designed from the
user-input valley lines on the Surface for Elevations would require
changes in elevation or slope to make smooth concave
profiles. The alerts
can be very precise, to decimal point values, but the user may not
be concerned to be alerted for extremely small
variances. The channel
head elevation tolerance setting allows the user to input an
elevation variation that the user finds significant, for example if
the user is concerned about lowering or raising the channel
elevation by 0.3 units, they would enter 0.3 in the edit window and
pop-up alerts will only appear when greater variances
exist. Note: When the
project area is relatively large, even small differences in
elevation over the area can result in significant changes in
material volumes.
Channel head slope tolerance: Natural Regrade alerts the user via pop-up dialogs when channels designed from the user-input valley lines on the Surface for Elevations would require changes in elevation or slope to make smooth concave profiles. The alerts can be very precise, to decimal point values, but the user may not be concerned to be alerted for extremely small variances. The channel head slope tolerance setting allows the user to input a head slope variation that the user finds significant, for example if the user is concerned about starting the channel at plus or minus two percent from the specified head slope value, they would enter 2.0 in the edit window and pop-up alerts will only appear when greater variances exist.