Tutorial: Automate Stream & Catchment Delineation using the Graphical Modeler

2. Data preparation

We'll make two graphical models:

  • Stream delineation
  • Catchment delineation
The Stream Delineation Model should be applicable to SRTM 1-Arc Second tiles that you can download for many areas in the world. For this tutorial four tiles are provided, which cover the area of the Rur catchment.

1. Start QGIS
2. Add the DEM tiles
Four SRTM tiles

Because the four tiles cover much more than the Rur catchment area, we also need to digitize a bounding box. You can digitize a polygon or zoom in to the study area and use the Create layer from extent tool from the Processing Toolbox. Make sure that the on-the-fly projection of your project is changed to the projection that you want to use, which should not be a Geographic Coordinate System with lat/lon coordinates in degrees!

For this tutorial we have provided the bounding box.

3. Add the bounding box to the map canvas.

4. Click right on the boundingbox layer in the Layers panel and choose Set CRS | Set Project CRS from Layer.

This changes the project CRS from GCS (EPSG:4326) to UTM Zone 32N/WGS-84 (EPSG: 32632) that we're going to use.