What is catchment delineation?
Catchments were delineated by modifying the flow direction of rivers, lakes, reservoirs, and overland flow, instead of using DEM values. Because of the higher accuracy, this method can be used as a new solution for watershed division in the plains area.
How do you find drainage area?
Drainage areas are determined by tracing all of the water bodies flowing into the stream or river upstream of the proposed site. A divide or ridge surrounds every drainage basin. A divide is defined as “the line of separation or dividing ridge marking the boundary between two drainage systems.”
What are the steps for catchment delineation in QGIS?
We can summarize the steps for catchment delineation as follows: Preprocess information: merge, reproject, subset the information. (NOT IN THIS EXERCISE) Fill the voids or gaps in the DEM: r.fill.dir Derive the flow direction and flow accumulation rasters: r.watershed
How to calculate Dem in hydrological analysis QGIS?
Select the DEM in the Elevation field, and leave the default values for the rest of parameters. Some algorithms calculate many layers, but the Catchment Area one is the only one we will be using. You can get rid of the other ones if you want. The rendering of the layer is not very informative.
Which is the first module to execute in QGIS?
The first module to execute is Catchment area. You can use anyone of the others named Catchment area. They have different algorithms underneath, but the results are basically the same. Select the DEM in the Elevation field, and leave the default values for the rest of parameters.
What happens if you increase initiation threshold in QGIS?
If you increase the Initiation threshold value, you will get a more sparse channel network. If you decrease it, you will get a denser one. With the proposed value, this is what you get. The image above shows just the resulting vector layer and the DEM, but there should be also a raster one with the same channel network.