I am trying to use QGIS to assess what areas will flood if the river floods a specific height. I have a DEM of the area as well as a vector file of the lines of the river of interest. I cannot get a raster file of the river height. Is there any way to do this?

  • You might check with these folks: hatarilabs.com
    – Stu Smith
    Apr 6, 2021 at 1:44
  • 1
    Could you please clarify what you mean by "areas will flood if the river floods a specific height.". If it is a flat water level, you can simply just mark the area in the DEM that fills to that level. However most river systems are a bit more complex than that, youll likely have a slope and varying levels in tributaries.
    – itsgupta
    Apr 6, 2021 at 3:21
  • For example if the river level rises 1 foot, what will flood, I can't just fill the DEM to a set level because the river does not run at a constant elevation Apr 6, 2021 at 18:22
  • Search for HAND - height above nearest drainage.
    – FelixIP
    Sep 17, 2021 at 2:48

1 Answer 1


If you have GRASS enabled in your processing toolbox, you can use r.lake. This method takes a DEM, a water level and a starting point as input. The output is a raster map with the flooded area.

  • It is clear from tool name that this tool is wrong one for river flooding.
    – FelixIP
    Sep 17, 2021 at 2:45

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