Tuflow and estry manual Version 3

3.11.3Building the Topography (Zpts)

The model topography is defined by elevations at the cell centres, mid sides and corners. Each cell has the following elevations assigned to it as shown in Figure 4 .6:

• 
  “C” Zpt (ZC) – middle of cell
  
• 
  “U” Zpt (ZU) – middle right of cell
  
• 
  “V” Zpt (ZV) – middle top of cell
  
• 
  “H” Zpt (ZH) – top right hand corner of cell
  

One of most important aspects of TUFLOW modelling is to understand the roles of the elevation points.

The ZC point:

• 
  defines the volume of active water (cell volume is based on a flat square cell that wets and drys at a height of ZC);
  
• 
  controls when a cell becomes wet and dry (note that cell sides can also wet and dry); and
  
• 
  is used to determine the bed slope when testing for the upstream controlled flow regime (see Section 3.14.3).
  

The ZU and ZV points control how water is conveyed from one cell to another. If the cell has dried (based on the ZC point) the four ZU and ZV points on the cell sides are deactivated. ZU and ZV points also wet and dry independently of the cell wetting or drying.

ZH points play no role hydraulically. However, they are the only elevations to be written to the SMS .2dm mesh file, as SMS elements require elevations at the element corners (alternatives to this are being investigated for future releases).

A 2D domains Zpts is built up using one or more of the commands shown in Table 4 .8.
Table 4.8 2D Zpt Commands