The Geographic Wizard is the first in a series of steps required to create a catchments scenario. It consists of a structured sequence of windows (described below) that guides you through the process of defining the catchment area. On completion of the wizard, you will be presented with a node-link network.
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| Note: After a scenario has been created using the wizard, you cannot change the network, ie. you cannot merge or remove sub-catchcments. |
On completion of a step, move to the next step by clicking Next and backwards by selecting Back. Note that you cannot go back to the network definition step once you have completed it and moved on to the next step. Cancel allows you to quit the wizard at any time. Note that you You will lose all the data entered so far. Once you have completed all steps, click Finish to close the wizard and view the catchment in the Geographic Editor. This figure also shows the action buttons that are visible at the bottom of every screen in the wizard.
Welcome screen (Step 1)
The Welcome screen gives some information about the steps within the wizard. These include:
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The DEM based network generation method (shown in Figure 1) requires a DEM, and divides the entire node-link network into sub-catchments based on a user-specified measure of upstream area (sometimes called stream threshold), usually for first-order streams. You can define points on the stream network where confluences between sub-catchment will be formed. The minimum sub-catchment area can also be modified. For example, in a node-link network spanning 1000 km2, entering a stream threshold of 10 km2 will produce approximately 100 sub-catchments.
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DEMs that have been derived only from contour maps or from other remote sensing technologies such as light detection and ranging (LIDAR) or shuttle terrain radar mapping (STRM) are usually not hydrologically correct. Such DEMs need to be adjusted to represent the flow of streams in the right direction. This is because they create a sense that there are spurious pits in the landscape when actually, none are present. |
The Draw Network method (shown in Figure 2) allows you to define the networks manually, by loading a sub-catchment map (a raster with cell values set according to sub-catchment number) and then connecting sub-catchments by clicking and dragging using the mouse. This specifies how those sub-catchments are linked together by the node-link. You should use this method when you have previously defined the boundaries of your sub-catchments, either by using Source or an external program.
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