As of Build 2005-05-AN, cross-sections can be specified for G and S channels using the 1d_ta approach at the channel ends, rather than a single cross-section somewhere along the channel. This has a couple of benefits:
The upstream and downstream inverts for G and S channels can be based on the beds of the cross-sections, thereby saving some effort to enter this information. To do this, set the Upstream_Invert and Downstream_Invert attributes in the 1d_nwk layer to –99999. If either of these attributes is greater than –99999, the invert is set to the attribute value rather than that of the cross-section bed.
Cross-section surveys from other 1D models often have the cross-sections at the channel ends, therefore, this makes it easier to use these data.
There are a few rules on how end cross-sections are interpreted and applied as follows:
The 1d_ta (or 1d_xs) cross-section lines must have a vertice snapped to the channel end.
If a 1d_ta cross-section line occurs elsewhere along a G or S channel with end cross-sections, the midway cross-section prevails. This is particularly useful where two channels’ ends are snapped to an end cross-section, but the end cross-section is to be applied to only one of the channels (eg. one channel is a river channel using end cross-sections, and the other is an overbank channel). For the overbank channel, specify a cross-section line somewhere along the channel, and preference will be given to this cross-section rather than the end cross-section.
End cross-sections cannot be used to override previously defined cross-section properties for a G or S channel. You can override the end cross-sections using a midway cross-section.
For channels other than G and S channels, end cross-sections are ignored.
