Total area of the roof.
Urban Developer does not enforce a maximum area for this node type, however, the algorithms used to determine the hydrologic response (particularly peak flow) are not accurate for areas greater than 1000 m2 or flow path lengths longer than around 50 m. It is unlikely that you will have one roof node of 1000 m2 or greater flowing to a single downpipe. You can duplicate roof nodes if necessary.
The roof area must be configured to represent the total number of dwellings in downstream Average or Behavioural Water Use nodes. For example, 4 houses with 100 m2 roof space each would need to be attached to a single roof node with 400 m2 total area.
|m2||350||[1, 1000]||> 0|
|Average depression storage depth|
Represents the depth of the roof area’s depression storage (in millimetres) satisfied in a rainfall event, before surface runoff occurs.
In practical terms, maximum depression storage in the roof node represents the small amount of loss that occurs due to surface irregularities, water absorbed by debris in the gutters or in rust holes in the roof. It is a way of modelling the reality that you never see 100% of rainfall from a roof surface ending up as runoff, although runoff will usually be close to 100%.