HOW TO DELINEATE WATERSHED IN QGIS | DERIVE STREAM NETWORK & ADD AN OUTLET POINT USING QGIS | VLOG

today we will see how to delineate watershed in qgis derive a stream network and add an outlet point first of all open a new project in qgis then click on layer add layer add raster layer then browse your dm that you would have downloaded from usgs earth explorer website or bhuvan browse using the three dots then click on open add and close this so the dem is added the next thing is to install one plugin which is quick map services for that go to plugins manage and install plugins search for the plugin quick map services here as i have already installed this plugin so it will show me reinstall plugin or uninstall plugin but if you have not installed it then you will get an option of install plugin it will take a few seconds to get installed then after you can close this then in the menu toolbar you can see the option is web quick map services osm osm standard then in your added layers on the left side just right click on the layer dem and go to properties then after go to information as you can see it is geographic crs is geographic we will change it to projected so this cancel and then go to raster in menu toolbar then go to projections and then warp so it will be reprojected here an input layer it will be dem [Music] and we need to select the target crs that browse icon untick that no crs and then filter first of all you will need to search your utm zone so here my utm zone is 45n so i'll just write wgs 84 45 n [Music] you will need to write it completely like wgs 84 utm 45n then click on ok [Music] and run once it's completed just close it then in the status bar you can see this epsc 4326 we need to change that also so again it will be the same search for wgs 84 utm zone here it is 45 n for my case you can search your utm zone by using a website i'll provide that link in description then apply and then okay so now the crs has been changed to projected one i'll just untick this dem then you will go to processing and tool box then after search for field syncs and in that we'll click on field syncs wong and leo here in dem you will have to select reprojected then we'll untick everything except the field dm like the flow directions untick that and watershed basins also we'll just keep the field am and then run it will take a few seconds don't stop the process in between here it's done now you can click on close so we have got our field dem [Music] the next step is in processing toolbox search for stroller order and then just double click on that star order here in elevation it will be field dm and then we just need to run it and then close so as you can see on the left side we have got it from 1 to 11 then just untick all the layers and zoom into the location from where you want to delineate the watershed then after go to raster and raster calculator here double click on straddle order at 1 and an operator select greater than equal to here in this case i'm keeping it a 6 as my bends are from 1 to 11 then an output layer give a file name of your choice i am keeping it as sto then just save it and click on ok so now as you can see instead of 1 to 11 it is 0 1 then right click on that go to properties go to transparency and then an additional no data value just keep it as 0 then apply and ok so you'll be clearly able to see from where you need to delineate then in menu toolbar just click on that i arrow icon and as you can see on the right side in processing toolbox in the results viewer when you will click on a stream then here i'm getting is no data banned as one and this is the location from where i want to delineate my watershed and there i should get bend as one the next step will be up slope area so in processing toolbox search for up slope and double click on upslope area then here you need to input this target x and y coordinates as you will get this coordinates in the results viewer just copy the x and y coordinates first coordinate you will need to copy the target x coordinate and second in the target y coordinate then in elevation you will have to select the field dm and in method it will be 0 deterministic 8 and then run and then close this the watershed has been delineated i'll just zoom to layer and don't compare your results because the delineation will depend on the location from where you have delineated from the target inputs that you have given then go to raster and conversion polygonize raster to vector input layer will be upslope area and then run it's done then just close this [Music] then in vectorized right click open attribute table just delete the features having d d n as 0. for that click on that toggle editing which is a pencil like key you can see and then delete then just save your edits third icon is which is save edits then close this by performing the last step we converted it from raster to vector and now we will derive the stream network for that in the processing toolbox search for channel basins and then as you can see this channel network and drainage basins double click on that in threshold you will need to input the value that you have given in raster calculator here for my case i had given it as 6 and then in elevation select the dem and untick all these like flow directions flow connectivity stroller order then the drainage basins just keep these channels as we want to derive the stream network junctions and then run then close this so we have also derived the stream network now we'll just clip it in processing toolbox search for polygon clipping or just type clipping you will get this polygon clipping double click on that and in clip features select vectorized and input features will be your channels then run you can also give the file name and it will be good if you give your file name give the file name and then save it and then run then just close this then i'll untick this channels and this is done and the last thing that i want to show you is how to add an outlet point like i want to add my outlet point at this location then i'll go to layer create layer new shapefile layer give the file name as outlet browse using the three dots and in geometry type select point even you will need to change these coordinates it will be same like utm zone 45n give the name outlet and save it click on ok then select that layer right click on it and go to toggle editing and then add point feature then just zoom to the place where you want to add the outlet point just click there and here you can write it as 1 and ok so as you can see the outlet point has been added so this is how you can delineate the watershed and just save that layer edits derive the stream network and add an outlet point and one more thing i have written all the steps in my blog and i'll provide the link in description if you have any doubt then you can just read that thank you

Channel: itiscivilengineering CIVILELITE

Views: 299

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Id: hkdNXYKW240

Length: 15min 23sec (923 seconds)

Published: Sun Oct 31 2021