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In existing urban areas, especially during road reconstruction projects, we often face situations where only part of a roof can be disconnected from the foul system.
Currently, in InfoWorks ICM, a building object can only be linked to a single node. However, in reality, many roofs drain to two different systems:
The front side can often be disconnected and connected to the stormwater system.
The rear side usually remains connected to the combined system, since the drainage runs through the crawl space and combines with domestic wastewater.
This means that in many cases, only around 50% of the roof area can be connected to the stormwater network, while the remaining 50% stays on the combined system.
Problem:
When using buildings, it is not possible to represent this split realistically because buildings can only be connected to one node.
In the past, when using subcatchments, we could duplicate a building polygon — connecting one subcatchment to the stormwater system and the other to the combined system. However, this approach no longer works because building polygons cannot overlap, as they are treated as mesh-level zones.
Idea:
Enable building objects to connect to multiple nodes, with a defined percentage of the total roof area assigned to each connection.
For example:
50% of the roof area connected to Node A (storm system)
50% connected to Node B (foul system)
Benefits:
More realistic representation of partially disconnected roofs in existing urban environments
Consistent modelling approach for both new and existing areas
Eliminates the need for complex or artificial workarounds
Improves the accuracy of rainfall-runoff distribution and flow allocation in mixed systems
Thank you for raising this and thanks to those who voted.
I will progress the status of this to "Gathering Support" so we gauge the interest of this improvement from the wider ICM community.