Longitudinal River Elevation Profiles in QGIS

In this video you learn how to create longitudinal river elevation profiles in QGIS. Two methods are demonstrated: one with the Profile Tool plugin and another using a combination of three plugins (QChainage, Point Sampling Tool and Data Plotly).
There's another video where the second method is done without the QChainage and Point Sampling tool plugins, but with native QGIS processing tools: • Adding cities and town...
This video is part of IHE Delft OpenCourseWare. More free materials are available at www.gisopencour...
(c) OpenStreetMap Contributors

[@nomenetasaili7339]

Thanks for this. Must say your text book is really good. Thanks for writing it.

[@sebastiankrolik3927]

thanks to you and this video I will be able to earn my degree

[@rakeshkumarsahoo6296]

Respected sir,
Please tell me how can I plot the stream steepness Index profile using QGIS. If in QGIS this feature is not available then which software I should follow...kindly guide me.
Thank you very much.

[@sureshpatil1817]

Sir please suggest the name of plugin in Qgis which gives us geomorphological parameters such as length of river, number if rivers, Bifurcation ratio, stream frequency etc

[@suryateja6497]

very very helpful sir! Thank you

[@suneelkumarahirwar5189]

Sir, We are requested to please make video on how find reservoir capacity(volume) & reservoir area at required elevation in QGIS. When we find volume by raster surface volume and raster volume tool it gives much much different result i.e. 650 Mcm from actual value 130 Mcm in case of pawai Dam, so it creates confusion. If you make video over that subject it will help all irrigation engineers to design a Dam. Thank you sir...

[@naveenkumarshakya4736]

Survey kar le bhai wrd main paisa de to rahe hai.

[@simonebrotto1977]

All your videos are great Hans! Question: how do you usually estimate the channel bed slope of the main stream (used in steady flow manning equation) starting from DEM? I usually use profile tool plugin, copy to clipboard, in Excel I add a chart with linear best fit line, that slope is the dimensionless value for bed slope. I think this method is quiet straight forward and correct although it involves some extra QGIS manipulation, do you agree? Is there a tool (grass or saga) able to output bed slope value? Thank you

[@HansvanderKwast]

I think the approach is correct. The assumption here is that bed slope is equal to slope of DEM. With the PCRaster Tools plugin you can calculate the average or median slope of a river with a few steps. If that is useful, please let me know and I'll make a video.

[@HansvanderKwast]

But I think for the manning equation that's not needed. You need the general slope of the hydraulic grade. So I think your fitting method works fine.

[@simonebrotto1977]

@@HansvanderKwast best fit linear uses linear regression so you get the same result with =reg.lin in excel. Profile tool plugin gives you the chance to save a temporary file but unfortunately it contains just Zs not Xs (as for table). Point sampling tool saves both, distance and altitude so starting from this vector i think one should be able to obtain slope through linear regressione, maybe using statistics panel or some expression in field calc

[@simonebrotto1977]

@@HansvanderKwast I am more familiar with Grass and Saga tools, quite inexperienced with PCRaster, anyway for sure someone will appreciate it

[@sureshpatil1817]

Great information sir

[@daleduenas]

Hi, sorry for the inconvenience, but I can't see the answer to your question. Could you please share it. Cheers

[@tulikamondal3049]

thank you for this very helpful information sir.
i just had I question, in the graph prepared by the profile plugin what does the X and Y coordinate suggests? and what does the interpolation profile suggests?

[@HansvanderKwast]

X is distance along the profile line. Y is elevation (or value of the raster if you use another layer).

[@tulikamondal3049]

@@HansvanderKwast what is the unit used here? for elevation and distance? I've used SRTM DEM here

[@HansvanderKwast]

The y values are sampled from the raster. So if the pixels have values in meters, like the SRTM DEM used here, it will be in meters. The x axis uses distance in map units I assume. So it depends on the projection.

[@tulikamondal3049]

@@HansvanderKwast thank you. That was very helpful.

[@rojalinpriyadarshini2277]

Sir, how to get the ''River Vector'' Layer among the Channel Network of a catchment i.e. the Longest Stream.

[@MRKRIS10]

Thanks you very much mr

[@vijaykumarkashyap1840]

Dear sir, many many thanks for your amazing qgis video.
Sir, how can we develop hecras geometry file of a river in qgis latest version to further analyse it in hecras??

[@HansvanderKwast]

Have a look at RiverGIS plugin: rivergis.com/

[@mteixeira87]

Thank you so much!! :)

[@abdolkarimmehrparvar6583]

How can I draw the river line? I edited the channel layer and in the attribute table I removed all the channel except the river i want but in the profile the points are not in sequence and the profile has too many up and downs and it's not a descending profile.

[@ujjwalmeshram7183]

Dear sir, please tell me how to create stream length gradient index curve in qgis

[@TheLuxedeluxe]

I keep getting an error message "Active layer is not profilable layer."

[@atillakoyuncu660]

sir, can we calculate SL index in this way? Could you help

[@edifyingyou3769]

Hello, I am confused. Can you tell me how is that "River" vector layer created with those attributes?

[@HansvanderKwast]

For the profile you just need a line vector of the river that contains one feature. You can get that by dissolving. In the example I used a delineated river (explained in this video th-cam.com/video/2Ub0c7Ss-T4/w-d-xo.html) and used the longest distance, which I've manually selected and exported.

[@geetikachauhan6908]

Dear sir, My SRTM dem shows the lowest elevation along the river as 532m, however, my river profile lies between 550m to 570m. Sir, why is there a difference? Do the DEM contains information about the Thalweg of the river?

[@HansvanderKwast]

That depends on the DEM and the treatment. In my example I used a filled DEM. If the streams are derived from the filled DEM the lowest point of the DEM will be also the lowest point of the river (if you take the segments all the way to the outlet). If you use an existing river layer, like from OSM, then there is not everywhere a match with the DEM, because of sinks and spikes that are artefacts. Also the spatial resolution of the DEM will affect how well you can represent your river profile. SRTM gives an average elevation for 30 m x 30 m pixels.

[@geetikachauhan6908]

​@@HansvanderKwast Thank you, sir, for the detailed reply. I have learned a lot from your videos, thank you, for making them.

[@aloisiojbc9496]

@@HansvanderKwast Great video. By generating the river vector using a lower Strahler order (let's say 5 instead of 7, as u explained in the video: Webinar 4: Stream & Catchment Delineation), can I avoid the river vector dropping out of the river channel? (the problem is that. At some points, the shape is out of the river channel, and the plugin (Point Sampling Tool) captures the wrong Z value. Did u manually correct the river vector? I have used the fill Sink (wang & liu), but the river vector line is still going outside the river channel, which causes higher Z values.

[@HansvanderKwast]

@@aloisiojbc9496 If you calculate the channels with the same filled DEM you should have the correct values. The channels algorithm uses the Strahler algorithm first, which is derived from the filled DEM. Then it will vectorise the Strahler orders above the chosen threshold. If river pixels are not at the lowest point, something else is wrong. Mismatch of projections? Other DEM used?

[@bbase322]

If your footage is off, how do you fix it?

[@HansvanderKwast]

Not sure what you mean.

[@bbase322]

@@HansvanderKwast I believe the length is in meters, how do I change it to feet?

[@sureshpatil1817]

Sir please suggest the name of plugin in Qgis which gives us geomorphological parameters such as length of river, number if rivers, Bifurcation ratio, stream frequency etc