The "Data for main channel" fields display information that GeoFluv™ will use to create the main valley-bottom channel that conveys all runoff from within the GeoFluv Boundary downstream to the base level elevation. The GeoFluv™ design is built headwards from the base elevation.
Head Elev. (ft.)
displays the elevation at the head of the main valley bottom
channel. GeoFluvTM can determine a
head elevation from the three-dimensional surface entered using the
Pre-Disturbed Surface button. The head elevation will appear in
this field when the user enters a three-dimensional surface file.
Alternatively, the user may specify an elevation using the Channels
tab's Advanced button to access the "Specify head elevation" option
on the 'Channel "main" Advanced Settings' dialog box.
Base Elev. (ft.) displays the elevation at the that is the local base level for the main valley bottom channel. GeoFluvTM can determine an approximate base-level elevation from the three-dimensional surface entered using the Pre-Disturbed Surface button. The approximate base-level elevation will appear in this field when the user enters a three-dimensional surface file. This elevation is adequate for creating draft GeoFluv™ designs, but the user must use an accurate field-surveyed base-level elevation for the final design. The user may specify the field-surveyed base-level elevation using the Channels tab's Advanced button to access the "Specify mouth elevation" option on the 'Channel "main" Advanced Settings' dialog box. (See also Settings tab's "Natural Regrade Global Settings", Slope at the mouth of the main valley bottom channel (%) for this related critical setting.)
Valley Length (ft.) displays the length of the main channel that the user has identified using the Setup tab's Select Main Channel button. After the user inputs the transition point from the main channel's headwater reach (slope >-0.04) and its valley bottom reach (slope <-0.04), GeoFluvTM will display the length of the selected main channel in this field and use the value to calculate the main channel subwatershed drainage density.
Drainage Density displays the drainage density value for the main valley bottom channel subwatershed as determined from the main channel Valley Length (ft.) and the GeoFluv Boundary Area (ac.). The drainage density is displayed in units of feet/acre in U.S. units, a convenient unit for landform design work.
If the drainage density is within the variance that the user specified in the Design Natural Regrade dockable dialog box's Settings button, Natural Regrade Global Settings, "Target drainage density variance (%)", then the value will be highlighted in green; if the value is outside the user-specified variance it will be highlighted in red. A red warning can mean that the drainage density is too high or too low. If too high, the channel can be shortened or the GeoFluv Boundary area decreased. If the value is too low, the main channel can be lengthened or more channels can be added using the Channels tab's Add button.