More 2D Sediment Modelling Options in InfoWorks ICM

An earlier blog (http://blog.innovyze.com/2014/08/05/2d-suspended-sediment-modelling-in-infoworks-icm/) described some of the options in InfoWorks ICM available for suspended sediment modelling. Since then software development has been undertaken within ICM which allows the modelling of bed load sediment from InfoWorks ICM version 5.5.  Such functionality allows improved representations of geomorphological process that may take place in fluvial and floodplain environments for example.

Bed Load Sediment Modelling

Within the suspended sediment blog it is mentioned that 2 model types can be selected, total load and suspended load models.  If the former is chosen, it represents both the suspended and bed sediment.  If selecting the suspended load model then previously this modelled suspended sediment only.  However it is now possible to explicitly model the bed load sediment transport separately to complement the suspended sediment modelling.

To do this, within the Water Quality and Sediment Parameters we select a bed load formula within the 2D Bed Load model section.

Figure 1: Bed Load Transport Model Selection

Figure 1: Bed Load Transport Model Selection

There are 4 available bed load transport models which can be selected:-

  • Meyer-Peter-Müller
  • Wong and Parker
  • Van Rijn
  • Einstein-Brown

Each of these is described in detail in the ‘2D Sediment Transport’ help page.  The user is recommended to read the original papers before using the sediment equations.

Critical Shields Method

As well as selecting a bed load transport model, it is also necessary to choose a critical shields method to determine the Shields number which is used to calculate the initiation of motion of sediment.  This can be defined using the Shields Curve approach (defined below) or a user-defined value for the critical Shields parameter (note, that within the UI this is shown in m, however it is unitless)

Figure 2: Shields Curve Parameterisation within InfoWorks ICM

Figure 2: Shields Curve Parameterisation within InfoWorks ICM

Sediment can then be modelled using either, Initial Sediment conditions defined either via the Initial Conditions 2D, sediment input via pollutographs or via 1D-2D linkages.  These approaches and the different bed layers are described in the suspended modelling blog.

QM Parameters

An additional option is now available in the QM parameters dialogue in which the user can choose to model the 2D bed load.

Figure 3: Bed Load QM Parameters

Figure 3: Bed Load QM Parameters

Since version 6 of ICM there are also parameters within the Water Quality and Sediment parameters which allow the user to define limits to erosion rates and deposition rates within a simulation.  This is useful when calibrating sediment models to observed data.

Results

New result parameters have been added specific to the bed load sediment modelling functionality to represent the sediment deposition and net erosion rate for bed load, these are available as a total value and also specific to the independent sediment fractions.  Specifically these are:-

  • Total deposited sediment depth due to bed load
  • Total deposited sediment depth SF1/SF2 due to bed load
  • Total deposited sediment depth due to bed load
  • Total deposited sediment depth SF1/SF2 due to bed load

The above result parameters are also available for the suspended load.

Summary

Infoworks ICM now has the ability to undertake total load sediment transport modelling, suspended and bed load modelling.  In version 5 total load and suspended sediment modelling functionality was added to the software.  This has been further enhanced in version 5.5 with the addition of functionality to allow the explicated representation of bed load modelling.  Currently the 2D sediment modelling functionality is only available on the CPU engine and is not available on the GPU engine.  However, the functionality now allows users to under geomorphological modelling in a range of environments using InfoWorks ICM.

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    About Duncan Kitts

    Duncan Kitts is a Senior Support Engineer with Innovyze in the United Kingdom, specializing in River modelling and 2D modelling. He has over 9 years experience of modeling the key hydraulic processes involved in both fluvial systems and urban drainage environments. Duncan is responsible for providing support of both infoworks ICM and Infoworks RS.
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