Bed Parameters¶

For advanced morphological analyses, the 'Bed parameters' editor controls how the bed of the channels is described in the model.

Layers layout¶

The bed material may be represented by one or two layers. The active layer is the layer in which sediment transport occurs. This active layer overlays a passive layer. Each layer is divided into the number of fractions specified in the 'Sediment fractions' editor.

The 'Layers layout' selection defines the number of layers used in the simulation:

Active and passive layers: this option requires at least two sediment fractions
Active layer only: this option is always available
Fully alluvial model (no layer): this option can be selected when only one sediment fraction is simulated and when that fraction is non-cohesive.

Target thickness of active layer¶

The following parameters are required for the target thickness of the active layer. Default values are mandatory and applied throughout all calculation points in the river network unless local values have been defined. Local values may be applied at specific locations defined by Link ID (river or pipe ID) and Chainage. The target thickness is calculated as a factor on the current water depth, though always within the range defined by the minimum and maximum value. To give it a fixed value, set Minimum and Maximum values to the desired fixed value.

Factor on depth¶

The factor to multiply on the current water depth to get the target thickness of the active layer during simulation.

Minimum value¶

The minimum allowed thickness of the active layer during simulation.

Maximum value¶

The maximum allowed thickness of the active layer during simulation.

Morphological update method¶

The selection of the morphological update method applies to river networks, but only when the morphological update is included, in the 'General parameters' editor.

A default method must be specified. Three options are available:

Horizontal distribution: sediments rest on the cross-section's bottom with a flat sediment surface. Primarily for use in cross sections with a fixed underlying bed, e.g. bottom of cross section made of concrete or sediment transported in pipes.
Uniform distribution: erosion and deposition are evenly distributed along the cross section.
Proportional to depth: erosion and deposition are proportional to water depth. This method uses the Floodplain level definition, specified in the cross sections (in the 'Cross sections' editor). Primarily for use in cross sections with floodplain to exclude the floodplain from sediment transport calculation.

The default method is applied throughout all calculation points in the river network unless local methods have been defined. Local methods may be specified in the secondary table, with locations defined by River ID and Chainage.

Note

For pipe networks, the morphological update method is always 'Horizontal distribution'.