User specified Cross Sections¶
User-specified cross sections can be either open (river or canal) or closed (pipe).
The user-specified cross section is specified in raw form as a sequence of (x,z) coordinates, each coordinate being connected by a straight line to its neighbours in the sequence. The order of the coordinates is important, see the XZ Open and XZ Closed type cross sections. Note that the x-coordinates need not be increasing.
If the cross section is closed, it is assumed that the first and last (x,z) coordinates are connected.
In MIKE+ (Collection System) it is also possible to specify a cross section in a height-width format. Height and width values are translated into (x,z) coordinates before being processed (converted to processed data by the engine).
Figure: XZ Open and XZ Closed type cross sections.
Markers on open cross sections¶
Markers are information attached to the (x,z) points and used when the engine converts raw data of open cross sections into processed data.
There are seven different markers, three of which are required:
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Left levee bank (required)
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Lowest point (required)
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Right levee bank (required)
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Left low flow bank
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Right low flow bank
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Left coordinate marker
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Right coordinate marker
Markers 1 and 3 define the left and right edges of the cross section, respectively. Marker 2 defines the lowest point of the cross section, and markers 4 and 5 define the points where the banks of the cross section begin (the banks are typically the shallow area close to the edge). Markers 6 and 7 defines the points in the cross section matching the coordinates that are used for determining the correction angle - they are not at presently used.
If no markers are specified, then the left levee bank is set to the first (x,z) point and the right levee bank is set to the last (x,z) point. The lowest point marker is set to the point with the lowest z value.
MIKE+ (Collection System) has a type of cross section called XZRM-Open. The data from MIKE+ contains coordinates of the cross section ((x,z) points), the relative resistance at those points (R) and markers (M). The resistance values are relative to the resistance Manning’s M value specified for the link in MIKE+.