 Hello, welcome back on my YouTube channel. In today's video I'm going to explain how to calculate the flow accumulation using the PC Raster Tools plugin. We'll start off with this GeoTiff DEM, it's an SRTM DEM that has been clipped and styled with some hill shading. First thing that we need to do is to convert it to the PC Raster format. So we go to the Processing Toolbox and find the Convert to PC Raster Format tool and we have to define that the output data type is scalar because these are real numbers, continuous raster and I save the output as DEM and now we have the DEM as a copy in the PC Raster format. In order to do any flow analysis we need to calculate the flow direction map which in PC Raster is the LDD, the local drain direction map and we can create it using the LDD Create tool. We keep the default settings, you can check the documentation to control how the things are filled and now we can check the AccuFlux tool which calculates the flow accumulation. It needs this flow direction map and a material layer and you can see there in the help string that that's a scalar raster that it needs. So that could be a rainfall raster or any other material that you want to route but in this case we are just interested to calculate the standard flow accumulation map and then we use a value 1 for each cell that we will accumulate and then each cell will have the accumulated amount of pixels and we can create that using the spatial tool. If we give all cells a value 1 it will accumulate all the cells using the AccuFlux tool. So I create here a raster named material which has for each cell a scalar value of 1. Now I can fill in the dialog of AccuFlux with LDD and material and I call the result flow accumulation. So for material you can also use a rainfall or any other material that you want to route but if you just want to have a standard flow accumulation map you use this scalar 1 map that we just created. Now values can be quite extreme non-linear from a lot of small values to fewer higher values representing the river so you can play with these settings of how to scale your values when you style it. You can use a cumulative count or you can also use the quantile method depending on what you need to visualize it. Using map algebra you can then also choose which flow accumulation threshold can be used to choose the rivers. So I hope you have enjoyed this video. If you like these videos please subscribe to my YouTube channel and you will get updates about new ones. Thank you for watching.