2D Zone Data Fields (InfoWorks)

2D Zone data can be edited on either the 2D Zone Grid Window of the Polygons Grid or the 2D Zone Property Sheet.

Most data can be edited on the grid, but some fields cannot be displayed in the grid format.

To view and edit all polygon data, use the Property Sheet.

The following describes all the data which can be used to define a 2D Zone. For details of results fields, see the 2D Zone Results Data Fields topic.

Common Data Fields

Fields that are common to the majority of objects can be found in the Common Fields topic.

2D Zone Data

Database Table Name: hw_2d_zone

Show Columns

Database Names

Size, Type and Units

Defaults and Error Limits

Field Name

Help Text

Database Field

Data Type





Error Lower Limit

Error Upper Limit

Warning Lower Limit

Warning Upper Limit


The name of the zone.












Zone area. Default value calculated from polygon geometry.











Maximum triangle area

A measure of mesh resolution used when creating a 2D mesh. Maximum allowable triangle area for areas in the 2D Zone that are not in a mesh zone.






100.0 m2





Minimum element area

Minimum mesh element area used for calculating results.

Mesh elements with area less than the minimum area specified, will be aggregated with adjoining elements, until the minimum area is met. This is done for the purpose of calculating results in order to improve simulation stability and run time.

Mesh elements will not be aggregated across wall objects or Mesh Zone boundaries.

The minimum element area is also applied to limit the extent to which triangles are subdivided during terrain-sensitive meshing.






25.0 m2





Mesh generation

The type of mesh generation. Choices are:

  • Classic - the classic meshing approach that has been present in InfoWorks ICM since it was first released.
  • Clip meshing - A meshing approach that makes use of primary and secondary meshing phases. It is particularly suited to models with complex geometry and objects that may be approximately coincident.

See 2D Mesh Generation Methodology for further information about these two meshing methods.

The default meshing method is Clip meshing unless overwritten by a user-defined default.

mesh_generationText20 0

User Defined Default


Boundary type

Boundary condition for the 2D Zone.

(In any boundary case where water is allowed to flow out of the 2D Zone, the water volume that has flowed out of the 2D Zone is recorded in the log file to check mass conservation.)

Note that a Porous Wall, Porous Polygon, Base Linear Structure or 2D Boundary collinear with the boundary of the 2D Zone, will override the boundary condition of the 2D Zone along the coincident portion of the boundary. In the case of a porous wall, porous polygon, or base linear structure, coincident portions of the wall/polygon are considered infinitely high, regardless of any crest level specified.

Database Value


Help Text

Vertical wall

Vertical wall

The boundary of the 2D Zone is considered to be an impermeable infinitely high barrier.

Water cannot flow out of, or into, the 2D Zone.

Critical condition

Critical condition

If the level in the boundary element of the 2D Zone is above the boundary face level, flow out of the 2D Zone will be calculated using a broad crested weir equation without energy loss.

If the level in the boundary element is below the boundary face level, the boundary is considered to be a vertical impervious wall.

Water cannot flow into the 2D Zone.

Supercritical condition

Supercritical condition

If the flow in the boundary element is supercritical (Froude > 1) and directed outside of the 2D Zone, then the flow at the boundary face will be considered supercritical and calculated using the boundary element depth and velocity, regardless of the boundary face level.

If the conditions of the flow are not supercritical, or the flow is going into the 2D Zone, the boundary face will be considered as a vertical wall.

This situation is useful in areas where the user knows that the flow is flowing out of the 2D Zone without any effects on the 2D Zone.

Water cannot flow into the 2D Zone.



The boundary of the 2D Zone is considered to be surrounded by a bottomless pit. Water that reaches the edge of the 2D Zone will flow out of the zone and will be lost from the simulation.

Water cannot flow into the 2D Zone.

Normal condition

Normal condition

It is assumed that slope balances friction forces (normal flow). Depth and velocity are kept constant when water reaches the boundary, so water can flow out without losses.






Vertical Wall





Terrain-sensitive meshing

Check this option to apply terrain-sensitive meshing during the mesh generation process. The Maximum height variation field must be specified.

See Terrain-sensitive meshing for more details.

Maximum height variation

Enabled when Terrain-sensitive meshing is checked.

The maximum height variation that is permitted within a single triangle.

Triangles with a height variation greater than this will be split provided this would not result in a triangle smaller than the Minimum element area.

max_height_variationDouble L31.00.001   

Minimum angle

Minimum allowable angle between triangle vertices when creating a 2D mesh.











Roughness (Manning's n)

Manning roughness (n), used when creating a 2D mesh. The roughness value assigned to mesh elements in areas in the 2D Zone that are not in a roughness zone.

This field is automatically disabled if a Roughness definition object is selected in the Roughness definition field.











Roughness definition

The name of the Roughness definition associated with the 2D Zone.

Any Roughness definitions already specified can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.





Apply rainfall etc directly to mesh elements

Check this option to apply Rainfall profiles and their corresponding Evaporation profiles to 2D mesh elements in the zone.

See 2D meshes for further details.

2D Meshes and Subcatchment Overlap

If 2D meshes and subcatchments overlap, rainfall will be applied to both subcatchment and 2D mesh independently by default. To prevent applying rainfall twice in subcatchment areas, set the Apply rainfall etc field to outside subcatchments.











Apply rainfall etc

Enabled when Apply rainfall etc directly to mesh elements is selected.

Used to define whether application of rainfall and evaporation will be applied to the entire mesh, or outside of subcatchments only.

Database Value


Help Text



Rainfall and evaporation will be applied to all mesh elements in the 2D Zone

outside subcatchments

outside subcatchments

Rainfall and evaporation will only be applied to those mesh elements whose centroids are not inside a subcatchment boundary. Use this option to prevent rainfall being applied twice to subcatchment areas.











Rainfall profile

This specifies the name of the rainfall profile applied to the mesh elements in this polygon. Each profile within a Rainfall Event has a unique name. You must set a value in this field, or set the field flag to #D to use the User Defined Default.

If the field does not contain a valid rainfall profile ID, the following action is taken when you run a simulation:

  • If the Rainfall Event contains a single profile, this profile is applied in the simulation. This makes the assumption that if there is only one profile, you will want to apply it to the whole model.
  • If the Rainfall Event contains more than one profile, InfoWorks ICM uses the first profile in the event. A warning is included in the simulation log file.

When using a Rainfall Event containing rain-gauge boundary data, the Rainfall Profile is over-ridden and depends on which rain-gauge boundary contains the mesh elements. See Spatially Varying Rainfall.











Infiltration surfaceThe name of the Infiltration Surface (2D) applied to this zone.infiltration_surface_idText64       
Turbulence Model

The name of the Turbulence Model (2D) associated with this zone.

The specified turbulence model will be used as the default for the 2D zone, i.e. it will be applied to all 2D mesh elements that are not contained in specific Turbulence Zones (2D).

Rainfall percentage

Percentage indicating how much of the rainfall depth will fall directly onto the ground within the 2D zone.

Used to avoid double counting, e.g. of rainfall falling onto building roofs and flowing directly into the drainage system.

rainfall_percentageDouble  3 0100  

Mesh summary

Read only field containing meshing summary data (e.g. ground model, data source for voids, break lines and walls, mesh zones used, number of triangles etc.), a list of mesh warnings and resampling information.

Only the latest meshing information is stored in this field. Previous meshing summary information will be overwritten if re-meshing of the zone takes place and the mesh results are loaded.

See Creating 2D meshes.











Mesh data

Mesh element properties and simulation results (if loaded), can be displayed using this field.

Click to display the Select element dialog. Enter the mesh element ID and click OK to display data for the mesh element in the 2D Zone Mesh Element Properties dialog.

mesh_dataArray  0     

2D Zones

2D Zone Results Data Fields


Polygons Grid

Property Sheets