Watershed and stream network delineation on large scale basins with QGIS 3 - Tutorial

hello my friends my name is welcome to this tutorial this tutorial is for determination of the watershed and channel network on large case basins with qas okay so the first step here is that we are going to download data for i mean the elevation model for our area of interest for that you are going to receive a folder where that has the well this is where we are going to store the elevation models these are the output here json or chip file and these are the some united that is check files that reflect that shows or that points to our area of interest okay so here i will upload the file that it will be my hero json okay great then i will select here okay and my main i mean my first result but that could be my first result but because it's not actually you will be your first result will be st str mlg but i can also look for that str mlg somehow and this is it has to be capital xtr mlg1 yeah and this i don't understand that okay so if you i mean if i don't place if i don't place anything here okay i will look for that okay i will load my json these these data sets appear first okay but actually if i type um a name actually it won't it i cannot query that that data set this is not a problem for me this is probably from nasa okay and then you can use this one or you can use this other data set this one as well okay um for me whichever is it's okay so and there are four granules here so and the visualization this is quite good okay so i will download all of them [Music] okay download data okay and then i i'm sure okay these are from the previous tries so here i'm going to download this one this one this one and this one so actually it's download [Music] we will be downloading four files okay maybe one is missing so for eighty one five four five eighty i think that is missing five let's see 480 481 5581 581 okay great so i will start here struck here struck here and this one i will destroy here okay great so this control c i will place here on my them okay and these are the most important steps here on qs okay i'm really sorry that my q as in spanish in spanish it's a beautiful language okay i hope that you can manage some ways but i hope that you can get it you can get the workflow in this okay okay so here on documents i'm going to open the four files okay here i have the four files okay let me let me do something okay i need something more smart so i have changed qas to english so you are not going to hustle with introductions introductions okay so hearing home on this folder where we are have placed our uh them files we open them okay these are the four of them and then what we are going to do is we are going to create a virtual raster build virtual roster okay so we are going to select the four dams okay okay and then we are going to place everything in one band okay great so here i have my one band actually i'm not interested anymore in these ones why i do delete them because it creates disorder on the computation because we are dealing mostly with temporal rasters or temporal files so in sometimes the or like the majority of the errors is because you have pull or you have work with a lot with a raster that was not the most suitable okay so then we are going to grab our raster because why because what i have seen is that the field things the hydrological correction of one lieu works with utm it doesn't work with geographicals and these ones by default what the ones that you download comes in wgs 84 so we need to to [Music] to come to com reproject so actually this is saying raster [Music] um [Music] wrap to forget okay wrap represent i don't know why i mean this is not if i type graph actually nothing wrong but if i type with capital actually nothing comes but if i go here reactions here is actually wrap wire sorry my english is not good enough okay so here is this um the target will be i will change it to utm actually this is in song 17 south in wgs84 okay and then here i will uh here the output resolution i can do two processing ones first i can change the projection and then i can change the output resolution why do i change the upper solution because i'm talking about large scale bases so in large scale basins uh i'm not interested in defining the watershed network on them of 30 meters not because that is not possible because it will take so long so actually i will change the resolution to 120 and this will be quite a advantage to work because it takes less time and on large scale basis the difference is minor okay it will have a difference if you are working in a small scale basing what i mean what is the difference in between a large scale and small game actually not that much okay so this is uh this is already in three two seven one seven so it's in utm and then if we go to properties and then here on information we'll see that the pixel size is 120 okay i am going to save this one okay save us why because if you see both are output okay so i don't want to i mean i have to be very order okay otherwise i will have some problems so this is will be them then wgs 17 south then we yeah 17th out and with that last resolution of 120 meters okay great so okay great so i get rid of the other ones because i actually don't need it okay from that i'm going to do the fixings of one lu so feel things while you okay on the minimum slope i'm interested i feel the time and the flow directions but not interested in the watershed basins okay uh you can place a background map to okay okay so this is the flow direction okay i can place a background map here a google satellite that is actually sorry the problem is that is this one okay yes copy print this if you want this on your so and then with that you get the macro mark and then what we are something that we are looking for in this in order to see that if our geoprocesses is right is that our fdl has to be uh positive numbers okay so what does it mean that okay i will show you on the property symbology unique values classify and then here in greens and this one in red actually we are not interested in finding a red spots here and why not because the response means that it's a sink okay so it's actually a a cell that has no flow direction okay and if you have those cells your them you are not going or you are one you won't be able to define the string network okay here actually it's all right so i can save this as well i can save this as well so this is feeling okay okay so i get rid of all of them because i'm not interested in anymore okay and then what else i'm going to do is that i'm going to create channel network and dragnesh basins okay so here and this will be from the field that is the only one i won't be interested in flow connection flow connectivity not in the stroller i will be interested in drainage basin channels channel bases and not interesting junctions okay so it won't mean that it won't calculate them it means that it won't it won't save them or it won't plug it to the canvas once it's ready okay takes a little bit um just to show you something on this is the just to mention something i did this many times but on the for example in the times before i use sarah in order to select to to work with the to to define the basins but here i'm using just qas with the latest developments okay yes okay so here i have the bases but those are the jose the maxify basins what i am what i would like to know for example is i want to create a basis from this point okay maybe a basin from this point so this is actually possible okay so for that we need to do something that is called absolute area absolutely okay first i i need i really need to be very close to the stream network okay and then i need to go to coronary capture okay and here on the system of projection i have to change the project system reference to to my utm and here i will capture any play any point that is close to the stream network so is this one okay so and why because if i do absolute area i need a target x so it will be the x of this point the tile y it will be the y of this point the elevation what will be will be our theme nothing else and then run and then the method uh any any of them i mean i have no particular choice for any medal i don't have a particular choice for an image okay let's wait a little bit okay and then you will see that the output basing will be plotted but as it will be plotted as it will be plotted [Music] as as a raster so we what else we need to do is polygonize polygonize and then what the area okay run okay great and then here well there are many small volumes here actually i'm interested in this one okay and then here on output i have to sport save fit feature as only selected features as hello and then here on out here on out this will be called basing okay and the next thing that you might be interested is on the river networks okay now channel network okay so these are the this is the channel network actually the colors are not so pretty okay so there is a way where we can use the flow accumulation or the channel the channel the drainage area in order to define the water network okay but i haven't been successful in doing that uh okay for doing this it took me a time so i think the process so far is okay but i will work on something for the uh for the to define this with a certain threshold of flow accumulation okay so here on segments i will do clip this is clip clip operator overlay i will clip the segments by basins [Music] let's see if this works and here i have clipped no no no no no no wait okay okay i will get rid of this is this because actually okay so these are the clip and the clip have not clipped anything okay so this one is known okay so here i have segments and here i have my base clip however segments should be clipped by basing okay i don't know why but it worked this way okay that's why it's important to be order okay so this is the clip version of mine okay so now what you can have is the watershed and the drainage and the channel network of our large-scale basing a procedure in qas why is large-scale basing because this is actually 100 kilometers okay for me it's large okay so really thank you for [Music] for this really thank you for your patience um hope that this tutorial will be helpful for you is kind of a basic procedure but it's basic not because it's easy it's basic because it's fundamental on the work that we do with water resources okay my name is or montoya you will find the some of the step rasters and the and the area of interest in on the description of the video strongly i strongly recommend that you follow this video and then you do by your own because uh like the probabilities of failure if you do it on your own area of study are much bigger that if you do first on the tutorial and then on your own my name is al montoya from hatred labs and for you please follow our youtube channel sign up for our online course follow our blog and share with your friends okay have a great have a nice day bye bye

Channel: Hatari Labs

Views: 3,778

Rating: 4.9322033 out of 5

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Id: jiREWrkHjs8

Length: 21min 8sec (1268 seconds)

Published: Fri Feb 05 2021