Current Channel Settings

This button allows the user to specify settings that will vary the channel discharge and the related channel geometry and upland ridge and subridge morphology specific to the subwatershed active in the Channels tab current channel name box. The settings are organized on two tabs, Geometry and Watershed. The Geometry tab has settings for maximum velocity, upstream slope, downstream slope, width to depth ratio, sinuosity, random scale factors on sinusoidal channel, subridge spacing on sinusoidal channel, and channel head and mouth elevation. The Watershed tab has settings for runoff coefficient when using the Rational Runoff Method (the default method), or to allow input of discharge computed by an alternate method, and to add runoff from contiguous land areas.

Command Prompt: (blank, dialog box appears)

Left-clicking on the "Settings" button brings up the "Channel 'xxxx' Settings" dialog box that gives the user the options shown below. The optional settings made in the "Channel 'xxxx' Settings" dialog box will apply only to the Channel 'xxxx' subwatershed. The blue subject bar at the top of the dialog box displays the name of the channel's subwatershed to which the Settings will apply. The user will select a different channel in the "Current Channel" window of the "Channels" tab and then left-click on "Settings" to make these changes to other channels and their subwatersheds, e.g., 'Channel yyyy', 'Channel zzzz," etc. After specifying the settings in the dialog box, the user can apply them by left-clicking the "OK" button at the bottom of the dialog box.

Geometry tab

Maximum Water Velocity (ft./s.): The user can specify a maximum water velocity for the channel by typing the desired value into the edit box. Velocity is inversely related to channel cross-sectional area for a given discharge according to the relationship Q/a=v, where Q is discharge (cubic feet per second), a is area (square feet), and v is velocity (feet per second).

Upstream slope %: The user can specify the upstream slope for the channel using this edit box. This feature can be used to vary the channel's longitudinal profile that will join to a mouth slope dictated by the receiving channel slope at their confluence. It can also be used to tie into the upstream slope when the headwaters of the channel are at the GeoFluv Boundary and join with an upstream channel slope draining "Additional watershed area."

Downstream slope % (Only adjustable on main channel.): The user can specify the mouth slope for the main channel at the GeoFluv Boundary to join smoothly to the downstream channel slope by typing the desired slope into the edit box. If the Channel's tab Settings dialog box is open for any tributary to the main channel, the edit box will read "n/a."

Width-to-Depth, slope>-0.04: xx.xx , <-0.04: xx.xx: The user can specify width-to-depth ratios for channels with slopes greater and less than -0.04 by typing the desired width-to-depth ratio into the edit box. The default values are 10.00:1 for channels with greater than -0.04 slope and 12.5:1 for channels with less than -0.04 slope.

Sinuosity, slope>-0.04: xx.xx , <-0.04: xx.xx: The user can specify sinuosity for channels with slopes greater and less than -0.04 by typing the desired sinuosity into the edit box. The default values are 1.15 for channels with greater than -0.04 slope and 1.48 for channels with less than -0.04 slope.

Random scale factors on sinusoidal channel: The meander pattern of the idealized draft valley bottom channels (<-0.04) will be determined by mathematical constants and thus will be very uniform, changing (enlarging) as a function of flow (related to discharge) and valley bottom orientation. Checking the 'Random scale factors on sinusoidal channel' box will randomly vary the constant values, within their acceptable ranges for stable channels, such that radius of curvature, meander length, and meander belt width vary. This random variation produces a more natural appearance for the channel and related upland landforms.

Subridge spacing on sinusoidal channel: This setting applies to channels with slopes <-0.04. The lower-gradient channels, with slopes <-0.04, may have an adjacent floodplain (or terrace) area and the uplands landform may begin some distance from the channel banks. The user can use this setting to create some of this open floodplain or terrace area by increasing the spacing between subridges. A subridge spacing setting of 3, for example, will create a subridge on every third meander bend of the channel with an opening for the floor of the subridge valley between these subridges.

Note: The user must select odd-number spacing; specifying even number spacing will result in all subridges and subridge valleys on opposites sides of the valley. Even spacing can be made with manual SurvCADD editing. The user can also manually add or delete subridges, or vary subridge longitudinal profiles using Natural Regrade's longitudinal profile editors, to introduce more variation to the draft GeoFluv^TM landform.

Specify head elevation: The user can specify the head elevation for any channel, rather than accepting an elevation that is automatically determined from the Pre-disturbance file specified in the Settings tab. The user checks the box to select this option and then proceeds in one of two ways. The user can type a desired headwater elevation into the Specify Head Elevation field. Alternately, the user can left-click on the Pick button and then identify a (COGO) point of the desired elevation on the drawing. To use the Pick method, the user left-clicks the cursor near the desired point and then, by moving the cursor diagonally, creates a box around the point. The user left-clicks again to define the opposite corner of the box surrounding the desired point and the point elevation is entered into the Specify Head Elevation field.

Specify mouth elevation: The user can (and should) specify the mouth elevation for the main channel only. This setting becomes inactive on the tributary channels because their mouth elevation is controlled by the main channel's longitudinal profile. The procedures for setting the elevation are the same as in Specify Head Elevation above.

[Note: The user should specify the mouth elevation of the main channel in the GeoFluv^TM project area because this elevation and the channel slope immediately downstream of this point may be the most critical variables for assuring a stable landform design. The elevations that Natural Regrade interpolates from the 'Pre-disturbed surface' specified in the Settings tab are appropriate for creating and comparing draft design alternatives, but a channel mouth elevation interpolated from a map surface can vary from the actual elevation on the order of feet. A channel will be expected to adjust to elevation and slope inaccuracies by erosion.]

Watershed tab

Use Rational Runoff Method: This is the default setting for calculating runoff to the GeoFluv^TM channels in Natural Regrade and is the setting that will be used when the box is checked. The Rational Runoff Method calculates a peak discharge using the formula Qpk = CIA, where C is the runoff coefficient, I is the rainfall intensity, and A is the acreage. The user enters the appropriate runoff coefficient for the area within the GeoFluv^TM boundary in the Runoff Coefficient field and Natural Regrade does all the related calculations.

Use manual Qpk: The user can choose to input a peak discharge value calculated by some other method should he wish by checking the 'Use Manual Qpk' option. When the user checks this box, the runoff coefficient field in the Use Rational Runoff Method setting (and use of that method) becomes disabled. The user then types in the peak discharges that he wants to use for the two storm events.

[Note: The GeoFluv^TM approach uses the 2-yr, 1-hour storm event to calculate bankfull discharge and the 50-yr, 6-hr event to calculate a flood-prone discharge. Reclamation landforms constructed using the GeoFluv^TM approach that use these inputs have been stable in a very harsh and erosive high-altitude desert environment through extreme storm events. Using other input values may give unsatisfactory results.]

Additional Watershed Area: This setting allows the user to incorporate runoff from contiguous lands into the GeoFluv Boundary. When the user checks the Additional Watershed Area box, the fields below become active and offer a choice of how the additional runoff will enter the GeoFluv Boundary. If the head of the GeoFluv^TM channel is downstream of the Additional Watershed Area, as when joining to an upstream channel reach, the user should select the "At head of channel" option. The GeoFluv^TM channel's headwater dimensions will then be sized to accommodate the runoff from the area above the channel headwaters within the GeoFluv Boundary and the Additional Watershed Area upstream of that. If the Additional Watershed Area is subparallel to the GeoFluv^TM channel, checking "Evenly along length" will introduce the runoff from the Additional Watershed Area gradually along the GeoFluv^TM channel reach and the channel dimensions will increase proportionately along the reach. The remainder of the settings are as described above in "Use Rational Method" and "Use manual Qpk."