1. Home
  2. Knowledge Base
  3. Cross Sections
  4. Automated Draw Cross Sections Command (HEC-HMS)
  1. Home
  2. Knowledge Base
  3. GeoHECHMS
  4. Automated Draw Cross Sections Command (HEC-HMS)

Automated Draw Cross Sections Command (HEC-HMS)

In GeoHECHMS, the Automated Draw Cross Sections command causes the software to automatically cut cross sections along a reach polyline. The software will attempt to uniformly space cross sections along the routing reach, creating cross sections that are perpendicular to the reach. In places where adjoining cross sections might cross each other, the software will intelligently bisect the cross section point of intersection and then run the adjoining cross sections parallel to each other.

Follow the steps below to use the Automated Draw Cross Sections command:

  1. From the Input ribbon menu, select the Cross Sections dropdown menu and then choose the Automated Draw Cross Sections command.
    Automated Draw Cross Sections Input ribbon menu command
  2. The Automated Draw Cross Sections dialog box will be displayed.
    Automated Draw Cross Sections dialog box

The following sections describe the Automated Draw Cross Sections command and how to interact with the above dialog box.

Selecting Reach Polyline

This section is used to select the reach alignment polyline(s) that will be used to automatically draw cross sections.
Select Reach Polyline section

Click the [Pick] button, and the dialog box will temporarily disappear. A prompt will be displayed on the status bar instructing the user to select the reach alignment polyline(s). The user can then select the reach alignment polyline(s) from the Map View.

Once finished, press the [Enter] key or right-click and select Done from the displayed context menu. The Automated Draw Cross Sections dialog box will be redisplayed, and the total number of selected reach alignment polylines will be shown in the Reach polyline read-only entry.
Reach polyline read-only entry

Note that if a reach alignment polyline(s) has been preselected before running this command, the same number of selected polylines will be displayed in the Reach polyline read-only entry.

General Settings

This tabbed panel is used to define the general settings for the cross sections to be created.
General Settings panel

Cross Section River Stationing

This section is used to control the numbering of the cross section river stations. The cross section river stations need to be unique per river reach, and need to increase in value as they move up the river reach. Cross sections can be numbered using a fixed increment or by the river chainage along the river reach. The river chainage can be in miles or feet if working in US units, or kilometers or meters if working in metric (SI) units.

The following options are provided:

  • Numbering direction: This dropdown combo box defines the direction in which the cross section IDs are increasing. The following options are available:
    1. Increasing Downstream
    2. Increasing Upstream (HEC-RAS style) (default)
      Based on the option selected, the content of the Use Reach Distance subpanel and the Cross Section Placement section will be changed.
  • Cross section ID prefix: This option allows a prefix to be added to the start of the cross section ID. By default, the Cross section ID prefix checkbox is checked.
  • Cross section ID suffix: This option allows a suffix to be added to the end of the cross section ID. By default, the Cross section ID suffix checkbox is checked.
  • Cross section ID preview: This read-only entry provides a preview of the cross section naming specifications defined above.

Use Reach Distance

This subpanel is used to number the cross section by using the river chainage along the river reach. Select the Use Reach Distance radio button to enable this subpanel.

The following options are provided:

  • Downstream cross section ID: This entry field allows the user to define the downstream most cross section ID for each selected reach and is used to determine the starting point for numbering the cross sections along the reach.
    Note that if the Increasing Downstream option is selected in the Numbering direction dropdown combo box, then the Downstream cross section ID entry will be changed in the Upstream cross section ID. In addition, the numbering methodology is altered to account for the selected direction.
    Numbering direction dropdown entry
  • Upstream cross section ID: This entry field allows the user to define the upstream most cross section ID for each selected reach and is used to determine the starting point in order to number the cross sections along the reach.
  • Distance units: This dropdown combo box defines the unit for the reach length. Two available options are:
    1. Feet
    2. Miles
  • Decimal precision: This optional checkbox defines the decimal precision to be used in determining the cross section IDs. By default, this checkbox is disabled (i.e., grayed out). If enabled, then the user can enter a value ranging from 0 to 6.

Use Auto Increment

This subpanel is used to number the cross sections using a fixed increment. Select the Use Auto Increment radio button to enable this subpanel.
Use Auto Increment subpanel

The following options are provided:

  • Cross section ID digits: This option permits specification of a set number of digits to use for the cross section ID. For example, using 3 digits causes the cross section ID to be of the format 001, 002, etc.
  • Next available Cross section ID: This entry defines the next element ID number to be used.
  • Cross section ID increment: This entry defines the increment to use when numbering elements. The default value is 1.

Cross Section Placement

This section is used to define the placement of cross sections along the selected reach polyline(s).
Cross Section Placement section

The following options are provided:

  • Approximate (max) cross section spacing
    This field allows the user to define the maximum distance between cross sections when placing the cross sections. The software will attempt to uniformly space the cross sections along each river reach, up to this maximum spacing. This prevents the last cross sections created along a reach from being spaced too close together. By default, the software uses a value of 500 feet (when working in US units) or 150 meters (when working in metric SI units). Clicking on the […] button allows the user to measure the approximate (max) cross section spacing from the Map View.
  • Cross section width
    This field allows the user to define the cross section width to be used when extracting cross section geometry from the terrain data. However, the defined cross section width is a starting point; additional criteria are provided to control how much data is to be extracted when the user extracts the ground geometry from the terrain. By default, the software uses a value of 500 feet (when working in US units) or 150 meters (when working in metric SI units). Clicking on the […] button allows the user to measure the cross section width from the Map View.

    Note that the Cross section width field is ignored if the user has enabled the Cross Section Geometry Extraction Control section from the Extraction Data panel.
  • Offset from downstream reach end
    This entry field is used to define the distance from a downstream reach end where cross sections should be located. This prevents a cross section from being placed directly at a river reach. By default, the software uses a value of 500 feet (when working in US units) or 150 meters (when working in metric SI units). Clicking on the […] button allows the user to measure the offset from river reach end from the Map View.

    Note that if the Increasing Downstream option is selected in the Numbering direction dropdown combo box, then the Offset from downstream reach end entry will be changed in the Offset from upstream reach end.
    Offset from upstream reach end

Extraction Data

This tabbed panel is used to define the data extraction specifications based on the options selected for the cross sections.
Extraction Data panel

Extract Elevation Data

This optional section is used to define the elevation data source(s) to be used for extracting the cross section geometry. Depending upon the elevation data source type that is selected, different options are provided to specify additional elevation data information.

Refer to this article in our knowledge base for information on the types of terrain elevation data that can be used for constructing cross sections.

If the Extract Elevation Data checkbox is unchecked, then the subsequent sections below it will be unavailable (i.e., grayed out). In addition, no geometry will be created when the cross sections are created. The cross sections will be just flat horizontal lines at elevation 0.

The user can also apply the elevation offset by enabling the Apply elevation offset checkbox entry. On selecting this checkbox, the entry field next to it becomes available for entering an elevation offset value. For example, the user can define a negative offset value to lower the junction for specific circumstances, such as in the case of a manhole bottom elevation.

Cross Section Geometry Extraction Control

This checkbox optional section is used to provide additional control in terms of the cross section geometry data to be extracted from the terrain model for the automatically drawn cross section polylines. These controls provide additional intelligence on whether to extend or limit the cross section cutting, based upon whether specific criteria have been met. This assures that an adequately deep enough cross section is created on both sides of the river reach. The software will attempt to retrieve the cross section geometry data to the depth specified within the specified maximum cross section width.

If the drawn polyline does not extend outward far enough to get the cross section depth specified, the software will automatically extend the constructed cross section further outward. Similarly, if the drawn polyline extends too far outward for the depth specified, the software will automatically trim the constructed cross section.

Alignment Settings

This panel is primarily used to perform automated cross section creation along sinuous (meandering) river reaches and is not used for other conditions. By default, the content of this panel is disabled (i.e., grayed out). Select the Generalize Cross Section Alignment checkbox option to enable this panel.
Alignment Settings panel

To learn more about this panel, refer to this article in our knowledge base.

Roughness

This panel allows the user to adjust the Manning’s roughness values for the left overbank, channel, and right overbank areas during the construction of cross sections.
Roughness panel

To learn more about this panel, refer to this article in our knowledge base.

About the Author cxscvlgeo

  • Was this helpful?
  • YesNo

Was this article helpful?

Related Articles