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.

Subsurface structures

Scalgo Live has a rich set of tools for modelling subsurface structures such as pipes, culverts, underground basins and large underpasses. Most of these can even be combined into larger stormwater pipe networks. In this section we discuss how these tools work at the individual level, we refer to the stormwater network documentation for more information about modelling subsurface pipe/sewer networks. 

When you select the subsurface tool through the icon shown above, you get three options:

Path

Creates a subsurface structure between the two endpoints of the path. The edit does not change any elevation on the terrain, but it allows water to be transported between the endpoints 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.

When you open the profile view of a culvert, it will represent the culvert as a dashed grey line connecting its endpoints. The elevation for the endpoints shown here is taken from the workspace terrain - no elevation is stored with the subsurface structure itself.

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. 

Paths can be connected to form larger networks.

Point

Creates a sink point on the surface connected to a subsurface basin with a specified volume.

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 15 mm rain event). 

Points are also automatically placed on the endpoints of all subsurface path features, and they connect adjacent segments in  subsurface networks.

Points can have a number of properties that modify their behavior:

Inlet. The inlet property determines whether water is allowed into the network at this point. Similarly, water is only able to leave the network at inlet points.

Inlet radius (for inlets only). By default, a point only captures water from flow paths that flow through the same terrain cell as the point. Therefore, it can be tricky to create a node that draws water from a particular flow path. To remedy this, we support the notion of an inlet radius which allows you to capture flow paths up to a certain distance away from the point. If you select the point, the inlet radius (if set) will be shown as a blue circle around the point.
(Note: Since all computations take place on a raster, the precise definition is that the center of the cell containing the flow path should be within the radius of the center of the cell containing the inlet point.)

Volume. A point can be associated with a volume, this can for example be used to model a subsurface basin in the Flash Flood Map.

Sink. Finally, a point can be designated as a sink, please see the documentation for stormwater networks for more information.

Area

The area tool connects two linear segments with each other under the surface of the terrain. Unlike points and paths, areas cannot be part of stormwater networks.

Usage example: Connect the two sides of a long bridge in a simple way.

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.

If you want to change the terrain on top of a building, you can delete the building and re-construct the building outline using one of the other terrain tools.