Structures¶
Structures represent building footprints or other solid obstacles within the domain. What they do to the model depends on the method you choose for each one.
Not for culverts, bridges, or weirs
"Structures" here means buildings and solid obstacles that block or impede flow. It is not for hydraulic conveyance structures (culverts, bridges, weirs). Those are modelled in ANUGA with the Inlet_operator, Weir_operator, and Culvert_operator operators, which the hosted scenario package does not yet expose as a dedicated input field. If your model needs them today, you can configure operators when you run ANUGA yourself. For the modelling expectation a reviewer will check, see the Verification checklist, section 7 (invert and capacity).
Methods¶
Each structure feature carries a method property, and the three do genuinely different things:
| Method | Behaviour |
|---|---|
| Reflective | The footprint is cut out of the mesh as an interior hole, tagged reflective. Water cannot enter it at all. This is the default. |
| Mannings | The footprint stays in the mesh and is given a Manning's n of 10.0, so flow through it is heavily retarded rather than blocked. |
| Raised | The footprint stays in the mesh and its ground is raised, by the height you set on the structure or the scenario's default of 5 m. |
Reflective is the default for a new structure, so a footprint you draw and leave alone becomes a hole rather than a friction patch.
Choosing Raised reveals a Raised height (m) field on the form. Leave it alone to inherit the scenario default.
Which method to use¶
- Reflective suits solid masonry you are confident water does not pass through. It removes triangles from the mesh, and the hole perimeter can add mesh cost of its own.
- Mannings suits built-up areas modelled in aggregate, where some flow between and through structures is realistic, and it keeps the mesh simple.
- Raised suits a structure you want represented as topography, such as a levee, bund or pad, rather than as an obstacle.
How it works¶
For Reflective structures, each footprint becomes an interior hole in the generated mesh with a reflective tag, so ANUGA applies a reflective condition around it.
For Mannings structures, the footprint is added to the friction set with a Manning's n of 10.0, overlaying any friction polygon underneath it. See Friction Maps.
For Raised structures, the footprint is rasterised onto the terrain and its height added to the ground before mesh generation.