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'''Figure 8 Original hazard output for 2.5/5/10/20m mesh SGS model.'''<br>
=Model Mesh Size vs Remap Result=
=1D/2D SX Links Defined Using 1D Nodes (1d_nwk) =
Besize the quality of hazard output discussed above, the model mesh size can still impact the remapped output in different ways.
As of the 2017 release of TUFLOW, nodes within a 1d_nwk file can be used to specify the location of 1D/2D boundary cells and also automatically assign an estimate of the appropriate number of 2D cells for the connection.
==Road Crest==
At location that bed elevation changes sharply, the remapped water depth may become negative if the output grid size is too large.
For a culvert, this is done by snapping a 1d_nwk point feature to the end of the 1d_nwk line feature and setting the 1d_nwk point attributes:
* Type = Node
* UCS = T
* CONN_1D_2D = SX
2D cells will be automatically selected as a 1D/2D SX links. The number of cells that are associated with the 1D/2D SX link will be defined by the nodal storage of the 1D channel. The figure below shows the 1D/2D linking cells in the 5m, 2m and 1m cell size models using this method.<br>
[[File:1D2D Model Stability 004.png|500px]]<br>
The modelled flow rates are shown in the figure below. As can be seen, comparable peak flow rates are obtained regardless of the cell size (i.e. cell size convergence is demonstrated). The stability in the 1m cell size case has been improved markedly, though there are still some oscillations at low flows. <br>
[[File:1D2D Model Stability 005.png|500px]]<br>
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