MIKE+ | Trick: How to create river bank couplings to be used in MIKE+?

Question
Which options are available in MIKE+ to create ”River bank" 1D-2D couplings in a river flood model?

Answer
The first step is to choose the appropriate location of the river banks markers along the cross-sections, i.e. decide which part of the cross-section will be used for the main river/1D flow by applying markers 1 and 3 (the part of the cross-section outside is not used in the 1D calculations and can be modelled by the 2D model).

There are at least three ways to create “River bank” 1D-2D couplings. 

• At the MIKE+ ‘Coupling tools’ menu click on the “Create couplings” button (1D-2D coupling ribbon) to display the Create couplings dialog - see Fig. 1. Running the tool should create a list of XY coordinates for the “River bank” coupling(s).

  
  Fig. 1. The 'Create couplings' dialog

  Alternatively, at the 1D-2D couplings editor one may use the “Insert” button to create a new ‘River bank’ coupling.
   
   

• If creating a new mesh at the 2D domain editor in MIKE+, i.e. applying the “Domain file created from MIKE+ definition” as the ‘Source’ option (not using an existing mesh) it requires the use of the “Exclude rivers” button (2D overland menu > 2D domain tools) to create a polygon of the riverbed which will be excluded from the generated mesh - see Fig. 2.

  
  Fig. 2. The 'Create couplings' dialog
   

  The ‘Domain definitions’ layer can be exported as a shapefile in the “Layers and symbols” table of Contents - see Fig.3.

  
  Fig. 3. Exporting the “Domain definitions” layer to shapefile

  Here is the Domain definitions shapefile after importing in GIS s/w - see Fig. 4.

  
  Fig. 4. Displaying the “Domain definitions” shapefile

  It is required to to cut off the river bank lines from the rest of the domain lines. Then use the MIKE Zero toolbox GIS tool Shp2Xyz (MIKE Zero Toolbox > GIS > Shp2Xyz) to create a list of XY coordinates - see Fig. 5.

  
  Fig. 5. Converting a shapefile to xyz text file in MIKE Zero Toolbox 

  The converted XY coordinates text file can then be inserted at the “Location in 2D domain” table in the ‘1D-2D couplings’ editor using the “Insert from file” button in order to define the spatial distribution of ‘River bank’ couplings - see Fig. 6.

  
  Fig. 6. Inserting an .xyz text file in MIKE+ as ‘River bank’ coupling 

   

• In Mesh Generator (or if using an existing mesh in MIKE+, open this in Mesh Generator with the MIKE+ 2D domain option: “Edit in Mesh Generator”):
  Select ‘Mesh’ menu > ‘Arc editing’ > click on the ‘Select points’ button > click on first vertex at the left bank > right click > convert “Vertices -> nodes” > repeat for last vertex at the left bank > click on ‘Select arcs’ button (and click on the left bank) > right click on the arc > ‘Export to XYZ’ (repeat for right bank line) - see Fig. 7.

  
  Fig. 7. Exporting arcs from Mesh Generator as .xyz text file

  In MIKE+ 1D-2D couplings editor use “Insert from file” XY coordinates to load left bank for left coupling (as in Fig. 6). Repeat for the right bank.

At the end of the process always ensure that the couplings are appropriately located and the two models are correctly exchanging water.  Please note that an adjustment may be needed in the resolution of the mesh along the river banks vs. the resolution (Dx) of the 1D model (the latter is defined by the distance between consecutive calculation water level points (h-points) or cross-sections (since a water level h-point is located at each cross-section)). The recommended ratio between the number of h-points by the number of adjacent elements is between 1:1 to 1:10, with a ratio of 1:5 often giving accurate enough results (i.e. 1 h-point associated with 5 elements or in other words ensure you have ~5 elements between consecutive h-points).

FURTHER INFORMATION AND USEFUL LINKS
Manuals and User Guides
MIKE+ Documentation Index

Training options
MIKE+ 2D Overland Flow – Getting started with urban flood modelling