 Hello, this is Hans van der Kost, senior lecturer at IHC Delft Institute for Water Education. In this video I'm going to demonstrate two methods to derive river elevation profiles. The first method is quite straightforward and we use the profile tool to visualize the elevation profile on the river. The second method uses the Q-Chainage plugin where we sample on a fixed distance the elevation from elevation model. And then we visualize it in a graph using the data plot lead plugin. So make sure you have a river vector layer, which should be one line dissolved, so there's only one feature, as you can see here, and you need a digital elevation model. So first we're going to install plugin, which is the profile tool plugin. In another video I also explain how this works. The profile tool is really useful to make profiles of a terrain using elevation model. You can draw a line, but here I'll show how to use the river line vector to make the profile. We click on the profile tool and we add the layer, that's the DEM, you can change the color of the line that it will produce in the graph, make it blue, because this is about water, and then I choose selected layer and I choose the river and it will plot then the profile of that river based on the DEM, and when I follow with my mouse the line it will show where we are on the river. You see a few steps in the river, with the space bar you can pan. To see what these jumps in the landscape are I'm going to switch off the DEM and look at OpenStreetMap. You can see that those steps are related to reservoir lakes. At the end of a reservoir lake there's a jump in the profile. We can also choose a slope percentage, then that's the derivative and there we see then where the peaks are are the jumps, so that makes those jumps in the landscape clear and where there are DEMs. We can also see the table with the sampled values, we can copy that to the clipboard and process it in other software, or we can export this graph as a picture. For the second method I use another plugin, that's the QChainage plugin. With the QChainage plugin you can sample at fixed distances on a line and it will create a point layer with those distance samples. So I choose here the river layer and I sample every thousand meters and you can then give an output name. Let's call it river sample thousand so it's clear that's thousand meters. Then under advance you can set where you want to start or to end or to divide it in equal parts and you can add some labels. But for us this is sufficient and you see it creates every thousand meter a dot. And here is the last dot because it starts from the upstream and it goes downstream and there's the first dot at the beginning of the line. The next tool I want to use is the point sampling tool. Very nice plugin where you can sample from other layers, rest or vector, so make sure the DEM is on. Here I can sample with the river sample points from the DEM. I use the distance from the original file and I call the field in the output distance and the DEM I call Z. Give it an output file name, go to the river sample Z thousand. Do okay, it generates a copy but then with the sampled values from the DEM. See that in the attribute table, so there's distance which I can sort and then you see every kilometer there's an elevation from the upstream to the downstream. Then another nice plugin is the data plotly plugin to create nice graphs. There we go, we can choose the plot type, there are different types here but here is scatter plot or bar plot is applicable. Make sure you choose the right layer and there are distance and Z. You can change the colors, I'll keep it like this. Then there you can change the title of the plot, the legend title. X label and Y label and some other settings. I'm gonna create the plot then it opens there and we see it has dots. And we also see those jumps and where it stays a bit constant where those lakes are. I think it's nicer to rename the legend here. So I'm going to call it 1000 meter sample point, click update plot, there it is. That's the final result. We can also make it a bar plot. I click clean plot and then I do create plot and there we see it as bars. So in this video I presented two methods to visualize the river profile using the DEM and different plugins. I hope you've enjoyed the video and please subscribe to my YouTube channel if you want to see updates. And for more free materials you can go to IHE Delft OpenCourseWare. Go to the link gishopencourseware.org.