TUFLOW Message 2050

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TUFLOW Message
ERROR 2050 - Lowest ZC elevation at/along SX link is above 1D node bed.

Alternate Message
WARNING 2050 - Lowest ZC elevation at/along SX link is above 1D node bed.

Message Type
ERROR
WARNING

Description
"The lowest 2D cell centre elevation (ZC level) at/along the SX 1D/2D interface is above the bed of the connected 1D node or element. The lowest ZC level at or along the 1D/2D interface plus the 2D cell's wet/dry depth must be below the bed of the connected 1D element for SX type 1D/2D connections. The SX boundary type creates a flow boundary to the 2D cells, to maintain mass balance, this automatically becomes a water level boundary to the 1D node. In order to allow water to enter or leave the connection the 2D cell must at or below the 1D bed level.
In the image below there is a 1D culvert below a road embankment. The image shows a section through the embankment, the brown line is the ground surface in the 2D and the black represents the culvert. At the downstream the model is correctly configured (the 2D cell is below the 1D bed level). However, at the upstream location the 2D elevation (shown in brown) is above the culvert invert. In this location Error 2050 will be created.
Error 2050 Image01.JPG

Suggestions
Revise the location of the 1D/2D connection or use a breakline layer to ensure that at the SX connection there is at least 1 cell where the 2D elevation is at or below the 1D bed level.
The ZC level of the 2D cell can be automatically lowered using ""Z"" in the Flag attribute for the object - see table of 2d_bc attributes in the manual. However, care needs to be taken as this lowers the cell centre only and does not necessarily create a flow path for water into / out of the connection cell(s). Incorrect use of the "Z" flag can results in stability issues. For the 2012-05 release, it is possible for the user to set a maximum change in ZC elevation caused by the use of any "Z" flags for 2D SX links. This allows the modeller to automatically lower 2D cells within the specified limit, but flag an ERROR 2050 if there is a substantial change, which usually indicates there is something inconsistent between the 1D channel bed and the 2D topography.
If there is a inlet (vertical) structure that allows flow from the ground level to the pipe a pit structure should be used to represent this.

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