SMS:CMS-Flow Transport Control

This tab allows the user to specify model parameters relating to both salinity and sediment transport modeling in CMS-Flow. These are two separate options. The tab also includes controls to allow specification of spatially varied data that impact sediment transport. The controls include:

Time Steps

In addition to the timestep specified in the general parameters tab for hydrodynamic calculations, the explicit model also allows the specification of longer timesteps for processes that do not vary as rapidly. These include the salinity and sediment transport.

• Transport rate: If either salinity or sediment transport are enabled in this tab, the user must specify a this time step". It must be larger than the hydrodynamic timestep and is generally at least a factor of 20. The default transport rate timestep is 60 seconds.
• Morphologic: If sediment transport is enabled for a simulation the user specifies the morphologic timestep. This controls how frequently the bottom elevations of the domain are updated in the hydrodynamic calculations. This timestep is generally measured in hours because the change in bed elevations do not occur rapidly enough to impact the hydrodynamics.

Salinity

CMS-Flow includes the capability to simulate the diffusion of saline water in fresh water. This section includes controls to enable and initialize these calculations.

• Calculate salinity: Turn on the calculation of salinity concentrations in the CMS-Flow simulation.
• Global concentration: This control allows the user to specify an initial concentration for the entire domain. Generally, a constant value is chosen, with 0.0 ppt (fresh water) being a commonly used value. Since this is not a realistic condition for salinity studies, the first portion of the simulation is often ignored (as with a hydrodynamic ramp) while the model computes spatially varied salinity concentrations. Hot start files can be used to skip this portion of a simulation for subsequent runs.

Sediment

The Sediment section of this tab turns on the calculation of sediment transport and specifies the formula that CMS-Flow will employ for sediment transport.

• Calculate sediment transport
• Use non-equilibrium transport

Hard Bottom

CMS-Flow includes the option to limit sediment transport on a cell by cell basis to simulate the existence of hard bottom. This section of the dialog allows the user to select, or create a dataset to represent these limiting depths.

• Create Dataset: By default, when SMS creates a "hard bottom" dataset, an inactive value (-999) will be assigned for each cell. This value indicates that no limit to scour exists. The user may select cells and assign limiting depths.
• Select Dataset: If survey data exists that defines the limiting depths of scour, these can be interpolated to the grid, creating a spatially varied data set. The select button allows the user to select such a set to use as the hard bottom data set. SMS copies this dataset to an editable set allowing further modification to these values.

D50

CMS-Flow relies on a spatially varied data set of median particle size to compute the shear stresses used in sediment transport and morphology calculations. This section of the dialog allows the user to create/select the dataset that defines these particle diameters. The buttons operate similar to the buttons for Hard Bottom described above.

• Create Dataset: When creating a data set, SMS prompts the user for the median particle size that will be assigned as the initial value for all cells.
• Select Dataset

== External Documentation ++

• Lund Cirp and Watanabe Formula
• Two-Dimensional Depth-Averaged Circulation Model CMS-M2D: Version 3.0, Report 2, Sediment Transport and Morphology Change[1]

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