6. Fill Sinks and Calculate Flow Direction

6.3. Calculate the Flow Direction

The next step is to fill the sinks (artificial depressions in the DEM) and calculate the flow direction raster. PCRaster does both in one step with the lddcreate tool. Check the documentation for the details.

1. In the Processing Toolbox go to PCRaster | Hydrological and material transport operations | lddcreate

2. In the Lddcreate dialog choose dem as DEM layer. Keep all other defaults so it will fill the sinks completely. Save the results to flowdirection.map.


3. Click Run. This can take a few minutes before the result appears in the map canvas. Click Close to close the dialog.

The lddcreate tool fills the sinks in the DEM and results in a local drain direction (flow direction) map. If you need the filled DEM, you can use the lddcreatedem tool.

In the next step we'll style the flow direction map.