Tute M01 Inspect Zpts SAGA

Introduction

In this page we look at the process on assigning elevations to the TUFLOW Zpts that define the elevations in the model using SAGA GIS. Ensure that SAGA is open, and open the DEM, which is provided as part of the Module Data and is named DEM_M01.sgrd.

Method

1. Open the blank Zpt layer 2d_zpt_M01_5m_002_P.shp, this was written in the TUFLOW\Model\saga\ directory. The Zpts will appear as a mass of points when zoomed to the full extent.

All Zpts in SAGA GIS
2. In the Workspace section of the interface (this can be toggled by using Window >> Show Workspace), navigate to the Data tab (tab located at the bottom of the window). Right click on the 2d_zpt_M01_5m_002_P.shp and select Save As. Save a copy of the table as 2d_zpt_M01_5m_003_P.shp. This is done for version control, we will edit the version 003 of the table as the input will be used in model run 003.
3. Open the newly created layer 2d_zpt_M01_5m_003_P.shp and close the previous version 2d_zpt_M01_5m_002_P.shp.
4. Ensure the Object Properties (Windows >> Show Object Properties) windows is visible, navigate to the Attributes tab. Select the Action cursor, and select a 2d_zpt. The attributes for the selected zpt will be shown, the SAGA window should look like the below:

All Zpts in SAGA GIS, with attributes selected

As can be seen the elevation for all zpts is a nuyll value of 99,999. The next step is to assign values based on the DEM.


5. Save the current TGC file as M01_5m_003.tgc. Comment out or delete the Write MI and Stop lines entered previously (these are no longer needed).
6. Add the following lines to the TGC file and save.
Set Zpts == 75
Read RowCol Zpts == ..\model\saga\2d_zpt_M01_5m_003_P.shp


Conclusion

The Zpts have been inspected from the DEM, the geometry control file (.tgc) updated to use the inspected Zpts. Please return to the tutorial model module 1 page where the next step is to define the active areas.