ST Boundary

Include boundary

A boundary condition is only applied in the simulation if this option is checked. Note, that this option is not available for open boundaries, where the ST boundary condition is mandatory.

ST boundary type

Three boundary types are available:

·         Fractional sediment transport: the load or concentration at the bound­ary for each sediment fraction must be specified.

·         Bed level change: the relative change of bed level at the boundary must be specified.

·         Bed level: the elevation of the bed at the boundary must be specified.

The ST boundary type can be controlled only for open boundaries. For sources along the river network, the ST boundary type is always a fractional sediment transport.

Input type

A Bed level or Bed level change boundary type can be set to either use or constant or time-varying value.

ST value

When the input type is set to Constant, the constant value for the bed level or bed level change is specified here.

File

When the input type is set to Time series, the time series used for the bed level or bed level change is specified here. The button to the right may be used to either browse, create, edit or plot the time series.

Item

This field shows the selected item in the time series.

Scale

The boundary condition value (constant or time series) will be multiplied by the specified Scale factor. This factor may be used to edit the boundary con­ditions without changing the input values, e.g. when performing a sensitivity analysis.

Fractional sediment transport table

For a Fractional sediment transport boundary type, the boundary condition for each fraction has to be specified in the table. For each fraction, the following data must be specified:

Fraction

The name of the fraction. Each fraction is described with its own row in the table.

Type

The fraction type (cohesive or non-cohesive) cannot be changed and is inher­ited from the Sediment fractions definitions menu.

Boundary type

The boundary condition for a cohesive fraction can be expressed using one of the two types below:

·         Concentration: boundary input is specified as a concentration (mass/volume) and the simulation engine will multiply the HD inflow at the boundary location to define the total mass entering the river at the boundary location.

·         Load: boundary input is specified as a specific load (mass) which is directly applied in the simulation engine as the load at the specific loca­tion. An eventual HD inflow source at the boundary location is hence not used to determine the mass inflow to the model.

A non-cohesive fraction is always expressed with a load, if only the bed load is included in the calculation for this fraction in the Sediment fractions defini­tions menu.

Input type

Here the boundary can be defined as a constant value during the simulation or a time varying value.

Scale

The boundary condition value (constant or time series) will be multiplied by the specified Scale factor. This factor may be used to edit the boundary con­ditions without changing the input values.

Constant

The boundary value must be specified here when the input type is set to Con­stant.

File name

When the input type is set to Time varying, the time series containing the boundary values must be selected here.

Item

This field shows the selected item in the time series, when the input type is set to Time varying.

Boundary condition buttons

View all ST boundaries

This button opens a new window which gives an overview of all fractions from all existing ST boundary conditions with type Fractional sediment transport, without having to navigate between each ST boundary. Data may be edited from this table and sorted by clicking in the headers of the table.

Copy to selected boundaries

This button may be used to copy the content of the Fractional sediment trans­port table from the active boundary to the selected boundaries.