Surface Pollutant Model


This model calculates the buildup and washoff of pollutants on catchment surfaces and in gully pots.

The model treats sediments and attached pollutants separately from dissolved pollutants.

These two processes are modelled completely independently by InfoWorks ICM. They do not interact in any way.

The diagram below illustrates the two processes involved in the surface pollutant model.

Surface Pollutant Model

Use the Surface Pollutant Editor to define the subcatchment characteristics required by the Surface Pollutant model.

These characteristics are defined in an object called a Pollution Index.

Innovyze Washoff Model

The rate at which eroded sediment runs off into the system is calculated using your chosen hydraulic runoff model.

The washoff of sediment (always Sediment Fraction 1) from the surface and the resulting inflow of each attached pollutant based on their potency factors are calculated. The washoff is taken from the effective impermeability.

No dissolved pollutant enters the system from the washoff model; only sediment and attached pollutants are introduced to the sewer network using the washoff model.

Gully Pot Model

The calculations for the gully pot model use the runoff from Runoff Surface 1 defined in the Land Use Definition. By convention, Runoff Surface 1 is the road surface.

The runoff is calculated by the hydraulic engine, using the runoff model you selected for hydraulic calculations.

No sediment deposition or erosion is modelled by the gully pot model. Only dissolved pollutants are introduced to the sewer network using the gully pot model.

Pollution Index

The Pollution Index is the water quality equivalent of a Runoff Surface:

Runoff Surfaces and Pollution Indices are applied via a Land Use:

See the Pollution Index topic for details.

Model process

The Surface Pollutant Model Process topic describes the operation of the Surface Pollutant Model as part of a simulation.

Further information

The calculation of buildup and washoff can be split into 4 main steps. To get more information on these steps, follow the links below:

Pollution Index

Surface Pollutant Model Process

Surface Pollutant Build-Up

Gully Pot Pollutant Build-Up

Surface Washoff and Gully Pot Flushing

Surface Pollutant Editor

Desbordes Model

Runoff Models