Tutorial: Automate Stream & Catchment Delineation using the Graphical Modeler

3. Create the graphical model for stream delineation

3.6. Snap outlet to delineated stream

The next step is to snap an outlet digitized from a map to the delineated stream from the previous step.

1. Go to the Input panel and double click on Vector Layer.

2. In the Vector Layer Parameter Definition type Outlet on map for the Description and set the Geometry type to Point. Keep the Mandatory box checked.

3. Click OK.

We're going to add another input for the tolerance of the snapping.

4. Double click on Number in the Input panel.

5. In the Number Parameter Definition dialogue type Tolerance as Description, choose Float as Number type, type a minimum value of 30, maximum value of 500 and default value of 100 meters. Keep the Mandatory box checked.

6. Click OK.

4. Go to the Algorithms panel double click the Snap geometries to layer algorithm.

5. In the Snap geometries to layer dialogue change the Description to Snap outlet to delineated stream, choose for Input layer the Outlet on map, for the Reference layer the Channels output from the previous step and for Tolerance the Tolerance input. Change Behavior to Prefer closest point, insert extra vertices where required.

6. Click OK.

Now we need to add the coordinates to the attribute table so we can use them later for the catchment delineation.

7. In the Algorithms panel double click on the Add geometry attributes algorithm.

8. In the Add geometry attributes dialogue type Save outlet with coordinates ad Description. Choose the Snapped geometry output as Input layer and save the layer as Snapped outlet.

9. Click OK.

The model looks now similar to the figure below.

Model stream delineation complete

10. Save the model by clicking .

11. Close the Graphical Modeler window.