Using Rainfall Events
To use a rainfall event in a simulation, the event must:
- contain profiles that are linked directly to subcatchments in an InfoWorks network, or indirectly via rain gages in a SWMM network.
- be included when scheduling a run (more than one event may be included in a run)
Linking rainfall profiles to subcatchments in InfoWorks networks
Link a profile from the rainfall event to a subcatchment by setting the appropriate profile number in the Rainfall Profile field of the subcatchment.
- A default value must be set in the Rainfall Profile field on the Subcatchment Page in the Subcatchment Default Parameters.
- A rainfall profile must be set for every subcatchment. To do this, either set a value in the Rainfall Profile field for the subcatchment, or use the default flag (#D) to apply the value set in the default parameters.
Linking rainfall profiles to rain gages in SWMM networks
In a SWMM network, profiles from a rainfall event (observed or design rainfall for multiple catchments) are linked to a rain gage by specifying the name of the profile in the Rainfall profile field of the applicable rain gage.
For design rainfall for single catchments, the design rainfall is automatically applied to every rain gage in the SWMM network, therefore no linking of rainfall profiles to rain gages is required.
A rain gage must be associated with a subcatchment in order for the rainfall data to be applied during a simulation. This is done by specifying the name of the applicable rain gage in the subcatchment's Rain gage ID field.
If a rain gage is not linked to a rainfall profile or a subcatchment is not linked to a rain gage, the network will fail validation.
Rain gages can also be associated with a Unit Hydrograph Group to model, for example, extra RDII inflow during and immediately after rainfall events, caused, for example, by seepage of rainwater into defective pipes. Rain gages are associated with a Unit Hydrograph Group by specifying the name of the applicable rain gage in the Rain gage field.
Spatially varying rainfall
InfoWorks ICM supports the use of spatially varying rainfall events in InfoWorks and SWMM networks to approximate the movement of a rainfall event across a subcatchment.
Rainfall profiles can be applied within the rainfall event to geographical regions. The profile is then applied to any subcatchment whose centroid falls within the geographical region.
When the rainfall profiles contain data defining their geographical region, InfoWorks ICM automatically uses this region data. In InfoWorks networks, the Rainfall Profile field for the subcatchment is ignored, while in SWMM networks, subcatchment's Rain gage ID field is ignored.
For more information on using geographical regions in InfoWorks networks, see Spatially Varying Rainfall and Using Spatial Rainfall in Simulations, and Using Spatial Rainfall in SWMM Simulations for details of how geographical regions are applied in SWMM networks.
Setting up simulations
To include rainfall events in the run, drag and drop one or more rainfall events into the Rainfall Event box on the Schedule Hydraulic Run View (InfoWorks) or Schedule Hydraulic Run View (SWMM).
Within the run, there will be one simulation per event for observed rainfall events.
For generated design events there may be more than one simulation per event if more than one return period or duration was included when generating the event.
