Runoff Routing Models
Runoff routing models determine how quickly the rainfall enters the drainage system from the catchment.
The runoff routing model for a Runoff Surface is set in the Runoff Surface Grid Window of the Subcatchments Grid or in the Runoff Surface Property Sheet.
Different routing models can be assigned to each surface type, but all the surfaces on a particular land use must have the same routing model.
Routing Models
The routing models currently available in InfoWorks ICM are listed below:
| Routing Model | Description | Subcatchment Data Fields used | Appropriate for: | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clark | Flow is routed using the Clark unit hydrograph method. Lag time and time of concentration are defined by the user. |
Time of concentration Lag time |
France and anywhere the Hydrological Engineering Center’s Hydrological Modeling System (HEC-HMS) models are used. | ||||||||||
| Desbordes | Flow is routed using a single linear reservoir, whose routing coefficient depends on subcatchment area, ground slope and percentage impermeable |
Catchment slope Catchment dimension (length) |
French systems running with event based simulations. The Desbordes routing model can be used for continous simulations, provided sub-events to define storm in the rainfall data is specified | ||||||||||
| HEC Snyder (Snyder Alameda) |
Flow is routed using the Snyder unit hydrograph method implemented using an equivalent Clark UH. Lag time and peaking coefficient are defined by the user. |
Peaking coefficient Lag time |
Users migrating models using the Snyder UH method, as implemented in HEC-HMS | ||||||||||
| Kadoya |
Flow is routed using the Japanese Quasi Linear Reservoir Method. See the Japanese Runoff Methodology technical paper for further information. |
Catchment area | This model is used as a standard runoff model in Japan | ||||||||||
| Large Catch | Flow is routed using two equal linear reservoirs in series, whose routing coefficient depends on rainfall intensity, contributing area and surface slope as in the Wallingford model. The software also applies a timestep lag and routing factor multiplier. The timestep lag and routing multiplier are functions of subcatchment area, ground slope and catchment length. |
Catchment slope Catchment dimension (length) |
UK systems where most subatchments are larger than 1 ha | ||||||||||
| Non-Linear |
Flow is routed using the Japanese Storage Function Method. See the Japanese Runoff Methodology technical paper for further information. |
Catchment slope Catchment dimension Equivalent roughness Storage factor K Exponent p Non-linear routing method Lag time method |
This model is used as a standard runoff model in Japan | ||||||||||
| ReFH | Flow is routed using a kinked triangle unit hydrograph. Time of peak flow, unit hydrograph peak and degree of kink are defined by the user. |
Time to peak Unit hydrograph peak Degree of kink |
UK drainage systems | ||||||||||
| SCS Unit | Flow is routed using an SCS unit hydrograph. Time of peak flow and total runoff time are either user defined or calculated from built in methods. |
Catchment area Time to peak Base Time |
Not suitable for mountainous or flat wetland areas | ||||||||||
| Snyder Unit | Flow is routed using the Snyder unit hydrograph method. Lag time and peaking coefficient are defined by the user. |
Peaking coefficient Lag time |
Developed using data for subcatchments in the Appalachian Highlands | ||||||||||
| Sprint | Flow is routed using a single linear reservoir, whose routing coefficient depends on subcatchment area, ground slope and percentage impermeable. | Catchment slope | Work done under the SPRINT project for large lumped catchments | ||||||||||
| SWMM | Flow is routed using a single non-linear reservoir, whose routing coefficient depends on surface roughness, surface area, ground slope and catchment width. |
Catchment slope Catchment dimension (width) |
USA drainage systems using the SWMM runoff model (in conjunction with the Horton or Green-Ampt runoff volume models for the pervious surface). | ||||||||||
| Unit | Flow is routed using a unit hydrograph. Time of peak flow and total runoff time are either user defined or calculated from built in methods. | Fields used depend on the method of calculation selected | Depends on the method of calculation selected | ||||||||||
| Wallingford | Flow is routed using two equal linear reservoirs in series, whose routing coefficient depends on rainfall intensity, contributing area and surface slope. | Catchment slope | UK drainage systems where most subcatchments are under 1 ha | ||||||||||
| Rational | Flow is routed using a triangular unit hydrograph which is based on the hydrograph method with rational formula (described in the Japanese Runoff Methodology technical paper). |
Fields used depend on the selected Time of concentration method:
|
Developed for subcatchments using a constant rainfall time series with the Japanese rational method | ||||||||||
| Cascade |
Flow is routed using a specified number of linear reservoirs in series, where it is held in each reservoir for a constant period of time. |
Storage factor K | Developed for hydrology modelling in Germany and suitable for Germany or locations with similar climatic conditions. | ||||||||||
| RAFTS |
Flow is routed using 10 non-linear reservoirs per subcatchment or per runoff surface according to the RAFTS (Laurenson) method. The RAFTS adapt factor and RAFTS n parameters are specified by the user either in the subcatchment parameters or the runoff surface parameters. The Degree urbanisation and RAFTS B parameters can be specified by the user or calculated by InfoWorks ICM if their data flag is set to default. These are required when RAFTS B is to apply on a subcatchment basis. |
Degree urbanisation RAFTS adapt factor RAFTS B RAFTS n Per-surface RAFTS B Equivalent Manning's n (only if the RAFTS B data flag is set to default and RAFTS B is to be applied on a per subcatchment basis) Catchment slope |
Developed for hydrology modelling in Australia and south-east Asia, and suitable for rural and urban catchments. |
