Complete Updated Workflow Stream and Catchment Delineation in QGIS

This video shows how to derive streams and catchments from SRTM DEM tiles from scratch in QGIS 3.16 LTR. The workflow uses different plugins: QuickMapServices, SRTM-Downloader, PCRaster Tools and GRASS tools.

0:00 Introduction
0:20 Define study area extent
3:04 Download SRTM tiles
4:30 Mosaic SRTM tiles
5:24 Reproject and subset DEM
7:04 Style the DEM
8:37 Convert DEM to PCRaster format
9:26 Fill sinks and calculate flow direction
10:40 Style flow direction with directional ramp
15:50 Calculate Strahler orders
16:50 Calibrate Strahler orders
19:29 Derive channel network
23:25 Style channels with Strahler orders
25:52 Smooth channel network
27:13 Define outlet of catchment
29:02 Derive catchment of outlet
29:37 Polygonize catchment
31:00 Style catchment boundary polygon with inverted polygon shapeburst fill
33:10 Clip channels with catchment boundary
33:54 Store results and project in a GeoPackage

#QGIS #QGISHydro #GISOCW

[borislavagacheva]

Thank you so much! I would have given up on calculating the Strahler order very early on if i hadn't found this tutorial!!

[Phil-wizp]

Great video! I was really frustrated that the SAGA Upslope Area tool doesn't work, this does the job equally well. Thanks!

[cevuardriddick]

Thank you 🙏 very much Mr. Hans for your tutorial. Help me a lots 🙏👏🏿 Merci infiniment 🇻🇺🇻🇺

[thangamraja]

Very informative and useful. Thank you for sharing

[Daldek]

Hi, Hans!
Thanks for the great series of vidos on hydrology in QGIS, I find it very useful!
Unfortunalte, I encountered an error trying to define an outlet point from a catchment. When running "Column file to PCRaster Map" I got an empty raster file. Well, on my disk it takes up some space, but it does not contain any numerical values. Would the seolution be to use point layer instead of txt file and rasterize it? I work with QGIS 3.28 (LTR).

[rubenbloem]

Hi Hans, thank you for your helpful videos. I've been following your tutorials closely, particularly the warp reprojection process. However, I've encountered an issue when I reach the step where I need to export and save the raster layer. In the 'save raster layer as' editor, I notice that your default resolution values for the horizontal layer are approximately 20.7896 and 30.1119. Strangely, on my end, the resolution defaults to values significantly lower, often less than 0.1. I suspect this discrepancy might be causing errors in my workflow. Could you offer any insight into why my map layer resolution defaults to such low values? I wonder if there's a crucial step or setting that I might be missing. Your guidance would be greatly appreciated. Thank you.

[francktheeten]

Very interesting thank you and felicitation for this nice tool !

[RegenerativeTV]

Great tutorial! really appreciate it. Best wishes

[rhernan]

Oh this is wonderful! Thank you for putting out such thorough content!

I was wondering, and I’m not even sure this is the right question to ask, when should one prefer to use PCRaster over GRASS and vice versa?

[robsonpassos]

Thank you very much for the video, PCRaster tools work perfectly for me. Just out of curiosity, is there any tool in PCRaster to calculate the horizontal and vertical distance from water courses?

[IATEBISCUITS]

Hi Hans, great video. instead of strahler order i used flow accumulation to derive the channel network. Is there a way to automatically search and define multiple outlet points of catchment when you are working with a large area?

[jqplebian]

Hello Hans. First off thank you for all your videos, they have been quite helpful. I have pcraster properly installed and have followed your instructions, but when I run 'lddcreate' my system does not seem to get anywhere. I let it run last night for about 10 hours and when I got up it was still running. My windows resource monitor shows qgis-bin.exe is using a good chunk of memory but the disk is sitting idle. The CPU status monitor for qgis-bin.exe is stuck at 'not responding'. I am at a loss here. I know when you talk about lddcreate in this video you say we the users have to be patient, but is 10-12 hours realistic? The DEM is not all that large, about 1.4GB. If you have any advice I would really appreciate it. Thanks!

[maiyourathaankarunanandara]

Hello Hans, I am an water engineer and I wanted to thank you for your contributions, which is really helping me to improve and experience the new tools and methods in hydrology.
I have couple of questions regarding catchment delineation.
1. What method does LDDCreate tool in PCRaster use to calculate the flow direction in not modified DGM, for example D8, Multiple Flow Direction (MFD) or D-Infinity (DINF) methods
2. I wanted to calculate the flow direction (Fließweganalyse) of my hilly catchment area and in my DEM the tunnels and bridge openings underneath the railway (Zug und Straßenbhanunterführung) are filled (These are not located on the river way). In this case do I have to burn the DEM first then do the fill sinks and the rest will be followed by in this tutorial? because in reality through this openings rain water is flowing downstream and merging to the river network.
3. How do i use the flow accumulation method to show the flow path of my catchment area (Not only main river but also foreland waterways)?

[diepnguyenngoc]

Hello, a problem occured when I run Lddcreate. The algorithm started but didn't manage to finish. My QGIS didn't respond anymore. Problem occured again when I reopened QGIS. I'm using QGIS 3.22 LTR. Is it the reason why ?

[szzor]

Hello Hans,

thank you for the tutorial, this is exactly what I need for my studies, but I have a question.

I am stuck at the pcr "Fill sinks and calculate flow direction" point. My QGIS tells me that the "PCRaster is not installed - algorithms will not be available". If I try to run the algorithm, it aborts immediatley saying "PCRaster library is not available". Do you know what the cause may be?

Thanks in advance!

[FormikFilms]

Hi, is there anyone else with the issue that the new layer of 'Convert to PCRaster Format' is shifted to the north by about a kilometer, when running this command? I double-checked that all of my layers are in the 32232 CRS (I am working on the Ahr catchment)

[lolaojelabi]

I keep getting this error every time I try the "reclassify by table" tool: PCRaster driver: value scale can not be determined; specify PCRASTER_VALUESCALE.
Execution failed after 0.02 seconds

[camelapedernal]

Hello Mr. Hans, if I would like to derive sub-catchments from other outlets, is it necessary for me to copy the coordinates of that outlet as well? If so, what will be the number after the comma in the new set of coordinates? Thank you in advance

[mehdiben]

Thanks a lot Hans for these videos and also for PCraster tools, every thing is working just fine like your tutorial, but i have an issue when i m on the part of Defining outlet of catchement, when i run the COLUMN FILE TO PCRASTER MAP the execution fail, it says it s an Assertion Error and i m pretty much sure i followed the exact same pats that you did on the vid, pls sir do y have any suggestions to this issue . THANKS

[berkayvaiz]

Hello Hans, I have followed your previous tutorial of deriving with saga. I am working on a Coastal Catchment and my DEM has the sea. When I use strahler order with saga I get streams where sea is supposed to be. Might be a beginner mistake, This is my first time with QGIS so ı am inexperienced.