The "Depth Correction" functionality is gone in MIKE+. What shall I do?

We need to step back a little bit and ask ourselves: 
What is "Depth Correction" functionality in MIKE 21 FM?

Depth Correction in MIKE 21 FM was often used to force cell-centered topography when a mesh file, in which topography is defined at element nodes, is applied as a domain definition. It was a commonly-used workaround to apply grid elements instead of unstructured elements before a dfs2 file became an option for a domain definition.

Typically a mesh file converted from a dfs2 file was applied as a model domain and then a dfs2 file was specified as a depth correction to force the cell-centered topography.

Depth Correction" is no longer available in MIKE+.

When you import a MIKE 21 FM (or MIKE FLOOD with MIKE 21 FM) with depth correction enabled, a warning is generated in the log. This functionality was not migrated to MIKE+ where a dfsu file became an option for a domain definition, in addition to a mesh and a dfs2.

A dfsu file stores cell-centered (averaged) values in unstructured elements.

So: how can I convert a MIKE 21 FM model with depth correction to a MIKE+ model?

There are two options, depending on if you already have a dfs2 or dfsu file with topography information.

Option A: Replace the domain definition with a dfs2 file if you have a dfs2 file with a topography. 

Option B: Replace the domain definition with a dfsu file.


Re.: Option A: Replace the domain definition with a dfs2 file.

A dfs2 file needs to satisfy the format of a model domain definition. (e.g. Closed boundary grids must contain Land Value or higher).  Even though this option is straightforward to implement, you may find it cumbersome to define open boundaries with a dfs2 file if your model domain is not a rectangular shape.

Re.: Option B: Replace the domain definition with a dfsu file.

You can create a dfsu file which has identical topography to your M21FM model with depth correction and use it as a domain in MIKE+.

1. Create a copy of your MIKE 21 FM model and remove all boundary conditions including Sources, Precipitation/Evaporation, and infiltration. Make sure that no water is leaving or entering the model domain.

2. Create a result file with "Surface Elevation" saved for "Whole domain" and just for one timestep.

3. Run the model for one timestep.

4. The "Surface Elevation" output dfsu represents the topography used in the MIKE 21 FM model.

5. Use this dfsu file as the model domain in MIKE+. 

Related Products: MIKE 21/3, MIKE+