Channel to Surface

The Channel to Surface command merges the designed channel surface into an existing surface (DTM). The design parameters of the channel are used to define the surface parameters of the channel. The channel surface is combined with the existing ground surface to provide a new surface containing the original surface data plus the channel. The new surface is a fully triangulated model that can be used to display contours, triangles, and other surface information. The elevations of the selected channel must be below the existing surface. To verify that the channel is below the existing surface, display a network profile containing the channel. Use Drainage > Edit/Review if necessary to change the channel elevations.

Before Using This Command

The command prompts you to identify an upstream and a downstream channel. If only one channel is to be modeled, select the same channel for both upstream and downstream. If the channel is trapezoidal or rectangular, the bottom edges are displayed in the graphics file. The merged surface is created in memory. To save the merged surface to disk, use File > Save As.

When multiple channels are connected, they must have the same bottom width to be modeled together. Trapezoidal and rectangular channels can be connected, but they must have the same bottom width. V-shaped channels cannot be modeled together with trapezoidal or rectangular channels. If channels that do not have the same bottom width are connected, you must model them individually, adding them to the surface one at a time. Surface modifications can then be performed using InRoads or InRoads Site.

The design surface should be empty before you run the command. Select the upstream and downstream channel. After you Apply the Transverse, Bottom and Top of Slope features are created in the design surface. Bottom and Top of Slope names are appended with L (Left) and R (Right). These features are combined with the features of the original design surface to create the new design surface. Now, the new design surface is populated with Transverse, Bottom, Top of Slope features. To create a new surface select Feature Rename, Replace, or Append to specify the action when a duplicate name is detected. The Rename option specifies to increment the duplicate name with a numeric value. The Replace option specifies to replace the duplicate name. The Append option specifies to attach to the original name.

Dialog Box Options

Upstream Channel

selects the beginning of the channel network that you want to model.

Downstream Channel

selects the end of the channel network that you want to model.

Original Surface

specifies the surface to which the software projects slope. This surface contains existing triangulated surface data.

Design Surface

specifies the surface that will be created containing a merge of the original surface and the channel. This surface should be empty.


defines the spacing between generated lines on the sloped surface. The software obtains the correct interval by measuring along the channel where the sloping begins.

Exterior Arc

specifies the arc (in degrees) between projected slopes on an exterior corner. This option creates smooth, rounded corners.

Maximum Distance

specifies the maximum horizontal length of the vector that can be projected out from the graphic element to the original surface.


specifies the name and feature style for the features generated by this command.

Name specifies a seed name to use for the features that are added to the design surface. Style specifies a feature style for the features that are added to the design surface.


creates breakline features from the left or right side of the channel bottom to the intersection of the channel side slopes with the original surface at the specified interval.

Bottom Name

creates a left and a right longitudinal breakline feature representing the channel bottom.

Top of Slope Name

creates breakline features that represent the longitudinal intersection of the channel side slopes with the original surface.

Point Density Interval

increases the density of triangle vertices along the feature when the surface is triangulated. Setting this parameter to a value greater than zero ensures that triangle vertices appear along the feature in the triangulated model and that those vertices are separated by no more than the specified interval.

A value of zero has no effect. This option does not apply to Random features.

This parameter increases the accuracy of your DTM. Imagine having a linear feature defined by only two points, 200 feet apart. The problem is that without densification, only these two points (the endpoints) are added to the DTM. Thus, when you triangulate the model, no triangle vertices appear along the feature (other than at the endpoints). If you want triangle vertices to appear every five feet along the 200-foot length of the feature, you would define a Point Density Interval of five.

Duplicate Names

determines how to resolve naming conflicts if the software detects a feature already exists with the specified name. You can Append, Replace, or Rename duplicate names when creating a new surface.


appends or attaches to a duplicate name.


replaces a duplicate name with a new one.


renames a duplicate name using the original name as the seed name and increments the duplicate name with a numeric value.


initiates the command using the information defined in the dialog box. The dialog box remains active after you click Apply.


dismisses the dialog box and exits the command.


displays help.