Editing the terrain – Object edits

Workspaces let you change your terrain model and observe the effects on the analyses. This section discusses the tools in the Objects section. 

These tools are there for modelling real world objects that can impact both the terrain and the land cover, and that can have additional descriptive fields used by the analyses performed on the workspace. For example, editing a building will both change the terrain and the land cover map of the Workspace.  The subsurface terrain editing tools, on the other hand, have no impact on the terrain but change how water flows in your workspace.

For an overview of the workspace editing process please consult the introduction page.

Some subsurface features use to model water flowing under bridges in the elevation model.

Subsurface structure (pipe, culvert)

Creates a subsurface structure between the two end points of the path. The edit does not change any elevation on the terrain, but it allows water to be transported between the end points without affecting the terrain between them. The subsurface structure will transport an unlimited amount of water, but it does not store any water itself – it has zero volume.

Usage example: Model culverts and underpasses without obstructing flow over the top of the structure.

If you work with our DynamicFlood simulation engine, you can set a diameter for the culvert to be taken into account by the DynamicFlood analysis.

Subsurface basin and sewage drains

Creates a sink point on the surface connected to a subsurface basin with a specified volume. This volume can either be typed in manually or set to an event-specific runoff volume from the watershed of the sink point. This runoff volume is determined by first clicking query runoff next to the volume input field and then, selecting the sink point position on the map. The event determining the runoff volume can be varied by dragging the rain slider which appears when clicking query runoff.

Usage example: Model the effect of a subsurface basin or a sewage drain with a guaranteed service level (e.g. a sewage drain dimensioned to handle the runoff volume for a 15mm rain event).


When creating a workspace (and not uploading your own data or using an alternative terrain model), buildings are imported into the workspace from the national buildings database.

Buildings are then regular workspace objects that can be modified or deleted.  They raise the terrain by 10m (with respect to the highest point in the terrain model under the building footprint), so that flow paths must go around them, and show up in the land cover map.

Buildings are always added last to the terrain model.  So you can model a landscape using e.g. contour lines, and then place a building on top of this landscape, but you cannot use workspace tools to modify the terrain "on top" of the building.  This limitation is necessary to let DynamicFlow treat buildings correctly.