Flow accumulation map:

Select an input raster map that is the output of a previous Flow accumulation operation. Open the list box and select the desired input map or map list, or directly drag a raster map or map list from a Catalog into this box.

Stream threshold:

Type a value for the minimum number of pixels that should drain into a pixel examined to add this pixel to the output drainage network.

Example: when using a stream threshold value of 10:

• pixels in the flow accumulation map that have a value > 10 will be assigned value True in the output drainage network map.
• pixels in the flow accumulation map that have a value � 10 will be assigned value False.

Use stream threshold map:

Select this check box when you wish to use a map containing various stream threshold values; subsequently, select an input raster map (with a value domain) that contains the threshold values.

Tip: A threshold map can be prepared with the Variable threshold computation operation. A threshold map can for example be based on internal relief values or on certain infiltration values for specific geological units, etc.

Clear this check box when you wish to use a single stream threshold value.

Flow direction map:

When using a stream threshold map, select a raster map that is the output of a previous Flow direction operation.

The Flow direction map is used to automatically fill possible gaps between found drainage lines. As a result, you will always obtain a continuous drainage network.

Output raster map:

Type a name for the output raster map that will contain the extracted drainage network.

Description:

Optionally, type a description for the output map. The description will appear in the status bar of the Main window when moving the mouse pointer over the map in a Catalog, and in the title bar of a map window when the output map is displayed. If no description is supplied, the output map will use its own definition as description.