Great help for learner, thank you sir

Thanks for the very helpful video. Great seeing Kastoria's Lake represented in one of your videos too!

Thank you Hans for the video. Two comments: 1. Would have been better if you had created streams. 2. The tools you developed, PCRaster, is a wonderful tool but as there are a number steps to create streams and delineate watersheds, it is difficult to remember and go through each step. Instead, you better combine them in some way so that all tasks are done only with minimum number of clicks like SWAT, etc.

Thank you sir, wonderful

Excellent another video

how to use Qgis to design storm water channel designs or sewer design using SWMM as calculating tool and Qgis for DEM ?

Most of your tutorials focus on just having one outlet point, and they derive one catchment. What if I had an entire mine site full of possible catchments, should I use the saga method, the PC grass method, or the PCR method? And if they SRM data is for a very rural unexplored place (say Mongolia) how do I know the outlets, for example I may know a few outlets from the channels vector, but not all possible outlets. Will the methodologies above derive subcatchments?

@HansvanderKwast

4 ай бұрын

In fact this video shows how to do that. If you use the pit tool, it will find all outlets based on depressions in the DEM. If you want more control and find all subcatchments based on Strahler orders, use this approach (which I think is really nice): kzread.info/dash/bejne/Z6l7w66CnMSsmJs.html. Note that this video was made before the PCRaster Tools plugin was published, but all tools in the video are now available through the plugin. Finally, the Resource Sharing repository has several tools that can help you: github.com/jvdkwast/qgisrepository

Hallo Hans, My question is regarding the PC raster IDD tools. I am working with 1m DEM covering 16km2 of area. I wanted to create a catchment out of this DEM and therefore I used IDD tool to create a flow direction, but this process was running almost one hour and I have to stop it. Could you please explain me why creating flow direction in PC raster taking an extended amount of time in comparison with arc gis flow direction method?

@HansvanderKwast

6 ай бұрын

That's a huge dataset. If ArcGIS does it faster for the same dataset, it's because it's using another algorithm. PCRaster allows more tuning with 4 parameters, which comes at a cost of calculation time. It also combines fill sinks with the flow direction algorithm, so you need to compare it with ArcGIS fill sinks. Some algorithms are rougher and more suitable for large datasets. In QGIS you can use from SAGA the Wang & Liu XXL algorithm or the one from WhiteboxTools. These are better for larger datasets. More about choices of algorithms in this video: kzread.info/dash/bejne/onyNq7FvksjXqaw.htmlsi=4xWwo7KaK-lO4g5e. Anyways, you need to think of a 1 m DEM is fit for purpose. Normally such a high resolution is not necessary for catchment delineation. Accuracy is also not the same as resolution.

@HansvanderKwast

6 ай бұрын

It's actually not super big, 16 M pixels should be doable. Are you sure the projection is not in GCS, but metric? Maybe something else going wrong?

@maiyourathaankarunanandara3382

6 ай бұрын

@@HansvanderKwast I always work with projected coordinate system, in my case UTM32 (Germany)

@maiyourathaankarunanandara3382

6 ай бұрын

@HansvanderKwast I have to do the flow direction analysis with this 1m DEM in order to identify the water movement in an urban area. With these results, I have to crate a 3d model to simulate heavy rainfall scenarios.