 Hello, this is Hans van der Krust from IHC Delft Institute for Water Education. In a previous video I've showed how to delineate streams and a catchment. In this video I'm going to show you how to style those results. This is based on the book QGIS for hydrological applications by Kurt Menke and myself. You can find the steps in chapter 4 of the book. Let's start with styling the channels of the raw catchment. Let's have a look first at the attribute table so we know better how to style it. We see there are two columns that are important, order and order cell. They refer to the strahler order. The order cell are the values in the original strahler order raster, similar as we created in some steps in the catchment delineation procedure. The same algorithm is part of the channels and basins algorithm. However, that also converts it to this vector layer and then the order column renumbers the original cell orders to new orders starting from one. So if we sort then we see that order of cell 8 becomes 1, 9, 2, etc. We open the layer styling panel and make sure that the raw channels is active. You can also select it over here. We change the renderer to graduated because we want to have a gradual scale applied to the column of order. You can also choose order cells, but here we will choose order. And because the orders are integer values, we change the precision to zero. So there will be no decimals. We change the methods to size. So we are not changing the color based on the attribute, but the size, so the thickness. And we change the size on a scale from 0.3 to 1 millimeter. We keep the mode at equal interval, but we change it to the amount of classes that we have. Here I chose a cutoff of 8 and it's until 11. So that means that there are four classes and there we see that it is applied. Now we can change the symbol and we set the color to RGB 1566 and 220 to get the right colors of blue. You click on this arrow to go back to the main screen of the settings. And now we can adjust the legend because we have order 1234 and not ranges. So I can just simply double click on the legend column and edit the values. And now we are ready. We have styled our channels layer with the strahler orders. Now we are going to style the flow direction raster layer. A flow direction layer indicates the direction of flow for each pixel to the steepest downward pixel. The direction of flow can be expressed by compass direction. However, it's not possible to store text in a raster. The compass direction can also be expressed by degrees on a circle where north is 0 degrees, east is 45 degrees, etc. To store 360 degrees, which is the full circle, we would need more than 8 bits because in 8 bits we can only store 2 to the power of 8 values, which means 0 to 255. To have more bits in a file, we need to increase the file size. However, in the algorithm to calculate the flow direction, we use the d8 method, which looks around the cell that we consider in 8 discrete directions. Therefore we only need to recode the directions into 8 values, where each value represents a discrete direction from the center pixel of a 3x3 matrix. Each software however does it in a different way. The SAGA algorithm that we use in QGIS from the processing toolbox uses 0 for north, 1 for northeast, etc. Which means that it stores values from 0 to 7 for all the compass directions. A value of 255 is used for surfaces that are flat and don't have any flow direction. We set the renderer to palleted unique values because it is a discrete raster, although there is an order, and we click classify. Since the value of 255 represents flat surfaces, we're going to remove this now for the time being from the classification. So it's now 0 to 7. We're going to choose a spectral color ramp, but we're going to modify it. So click right, and I'm going to edit the color ramp. In this window we can edit the color stops for the ramp. The idea is that the far left and right sides will represent northern flows, and we will set both of those stops to the same blue color to make it a circular ramp. We will then set the center stop to a bright yellow for southern flows. The stop in the middle on the right will be western flows, and the stop in the middle to the left will be eastern flows. So we click the drop down menu for color 1, and we choose pick color from the context menu, and we use that to select color 2. So it will be equal. Click the center stop, it will represent the southern flows and assign it a bright yellow. For the eastern stop we do green, and for the western stop we use magenta. Now we're going to add the flat areas back again. Click the plus sign, and there we change value to 255. 8 doesn't exist, that's just a default value, and we click on the color and we change it to white. We just pick the standard white there, and with the arrow we go back to the main screen. Now you see that the label column is still not very useful. That's exactly the thing that will appear in the legend, so we can just simply double click there and edit the values to the right compass directions. To get a better effect we are going to use a hill shade, so here is our DEM, and I'm going to duplicate the DEM, and I'm going to use that one as a hill shade, and for that we can use the hill shade renderer. I'm going to put it just below the flow direction map, switch that one off, and I'm going to use here the hill shade renderer. And you see by default the sun is in the northwest, which in reality is never the case, but that gives us the hill shading effect. And now I blend it, but when I zoom in I'll see a lot of these pixels. It has to do with the resolution, and I can blur it a little bit, but it's better to do that for the hill shade itself, because that is causing the issues. So here I put the hill shade to billionaire, and we see now a more smooth image appearing, and that just looks better with the hill shades. We are now going to style the digital elevation model in a similar way. We already have the hill shade, we put the DEM on top, and here we can then choose single band pseudo color, because it's a continuous raster with gradients, and we can choose another ramp. If we say create new color ramp, we can choose here CPT city, and CPT city gives us access to a lot of presets, and we choose here topography and elevation. And now we see that this ramp is assigned, and if we put the blending mode to multiply, then it will blend nicely with the hill shade that we have in the background. We can change the stretching of the colors also to the area that we're zoomed in to get more contrast. So now we have more contrast in the high areas, and if I zoom into the lower areas, and I click update canvas, then I get more colors there. If I want again the whole raster, and I click whole raster and colors will be stretched over the full range. The last layer that we're going to style in this video is the catchment boundary of the roar catchment. So make sure it's selected, and we change the renderer to inverted polygons, which means we're going to style everything outside of the polygon, and we can use that as a kind of a mask to make the area really come out. If I click on simple fill, I can change the symbol layer type to the shapers fill, and the shapers fill creates a kind of gradient between two colors, so we keep the two color setting here, and we're going to change the first color to 135, 135, and 135 for RGB, which makes it a gray, and the second color we keep that white. We set the distance of the shapers to four millimeter to make it a little bit smaller, and we change the underlayer rendering, the opacity to 65. Now we can see through the outside polygon our DEM. I'm going to add another renderer, simple fill, because I want the boundary to come out as a black line, so I choose here simple fill, and for the symbol layer type I choose outline simple line. Make the stroke width a bit bigger, and I change the color to completely black, so RGB should be 0, 0, 0, and that's the final result. Here we see our catchment map with the inverted shapers polygons really coming out of the screen within the background, the digital elevation model. We could also do that for, for example, the open street map layer, we see the same effect because we have this inverted shapers fill polygon of our catchment boundary.