A roof node represents a physical roof catchment surface. The roof model has no infiltration and quickly produces surface runoff during a rainfall event. You must specify a catchment area, time of concentration for the roof catchment, maximum depression storage, and what percentage of the roof area is connected to a rainwater harvesting tank.
Restrictions
The roof node surface area must be > 0.
Node inputs
Inflow: The roof receives inflow from other roof nodes. The inflow into the node, and the rainfall falling onto the catchment area of the node is then routed over the surface.
Link type:: Runoff
Node outputs
• Runoff to tank: Runoff quantity is proportional to the % of roof connected to tank.
Link type (page 66): Runoff
• Runoff bypassing tank: Other runoff; not connected to a tank.
Link type (page 66): Runoff
| Input | Description | Units | Default Value | Recommended Range | Constraints | |
|---|---|---|---|---|---|---|
| Min | Max | |||||
| Node name | Identifying name for the roof. The name must be unique. | NA | NA | NA | NA | NA |
| Roof area | 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 canduplicate roof nodes if necessary. | m2 | 350 | 1 | 1000 | > 0 |
| Time of concentration | The time of concentration represents the time taken for surface runoff to travel from the most hydraulically-remote point on the roof to the roof outlet. | min | 2 | >1 | NA | > 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%. | mm | 1 | NA | NA | 100 |
| Percent of roof connected to tank | Some roofs may have only a proportion of runoff directed to a tank, with the remainder being directed to stormwater or domestic garden use. | % | 100 | NA | NA | [0, 100] |