Tutorial: Delineate Multiple Subcatchments

Course: GIS OpenCourseWare for Hydrological Applications
Book: Tutorial: Delineate Multiple Subcatchments
Printed by: Guest user
Date: Wednesday, 26 January 2022, 8:38 PM

1. Introduction

In another tutorial you've learned how to delineate a catchment of a specific outlet. Sometimes, however, you want to do this for multiple outlets or for all subcatchments in a catchment.

After this tutorial you'll be able to:

  • Snap digitized pour points to a delineated river
  • Delineate the catchments of snapped pour points
  • Create pour points for all subcatchments in a catchment
  • Delineate all subcatchments in a catchment
The data provided with this tutorial contains a GeoPackage with a filled DEM, catchment boundary layer and hydrography.

Please note that this tutorial only works with the QGIS 3.10 LTR version and not (yet) with 3.14.

2. Digitize pour points

First we're going to digitize the pour points (points for which we want to delineate their contributing areas, i.e. catchments).

1. Start QGIS.

2. In the main menu go to Project | Open From | GeoPackage...

3. In the Load project from GeoPackage dialogue browse to the data_multiple_subcatchments.gpkg GeoPackage, choose the Multiple_Subcatchments project and click OK.

In the project you see the Rur catchment boundary, hydrography and filled DEM (filling a DEM is explained in the tutorial on stream and catchment delineation, which you need to apply to your own data before following the steps in this tutorial).

Now we're going to add a background map from which we can digitize some outlets. We'll use OpenStreetMap.

4. Install the QuickMapServices plugin. Go to the main menu and choose Plugins | Manage and Install Plugins...

5. Install the QuickMapServices plugin and click Close.

6. In the main menu go to Web | QuickMapServices | OSM Standard

7. Switch off the DEM and Hillshade by unchecking the box before the layer name in the Layers panel.