Tuflow and estry manual Version 3

3.13.2.4Procedure for Assigning NA Tables

It is important to note the logic in assigning node storage.

1. 
   User defined NA tables are read from any 1d_ta NA table links. The overwrite principle applies, so that if a NA table has been previously defined, the latter NA table prevails.
   
2. 
   User defined NA tables are read from any fixed field NA tables. The overwrite principle applies, so that if a NA table has been previously defined from Step 1 or in this step, the latter NA table prevails.
   
3. 
   Nodes without any NA tables assigned in Steps 1 and 2 above, and have one or more connected channels that have the Use_Chan_Storage_at_Node attribute set to “T”, have their NA table automatically calculated from the channel widths.
   
4. 
   As of Build 2005-05-AN, the Length_or_ANA attribute of a node (or pit) in a 1d_nwk layer can be used to add additional surface area to the NA table (see Table 4 .10). If no NA table exists after the above steps, and the Length_or_ANA attribute is greater than zero, a NA table of constant surface area is created.
   
5. 
   If there are any nodes remaining without a NA table, an ERROR occurs.