Hydrological Analysis Tutorial using ArcGIS Pro

hi guys welcome back to the channel in this tutorial I'm going to show you how to delineate a watershed starting from a digital elevation model like this using arjs Pro Now by definition a watershed is basically the area of a land that drains into a particular Lake a river or another water body of some sort and in this tutorial we are going to specifically derive a set of rivers from this elevation raster and after that for a specified point on the river we are going to to derive the corresponding drainage area which is going to be basically our Watershed now as I told you guys I'll be using an elevation data set to get started which is uh this file right over here and I'll be sharing this file with you guys as well just so that you guys can see whether you can follow along and create the same outputs that I'm going to create in the next few minutes and in the background you can see that I have already opened up my arjs Pro workspace what I'm going to do is I'm going to drag this Tiff file and drop it on my workspace like this and as you can see that'll automatically Zoom me into the extents of the stiff raster and if I zoom out a little bit you can see that my area of interest is somewhere around the southwest region of uh South Africa so once you import this stiff raster file over to your workspace this is how it basically shows up and uh the color variation basically shows us the elevation difference across this region and in case if you would like to have these displaying colors to be a bit more vibrant what you can do is you can just uh right click over here and head over to symbology and from here you can select a color scheme of your choice so let's say for this particular example I might go with a color scheme like this where in this case you can see right over here the highest values actually shown in blue color and the lowest values are shown in this brown color I might go ahead and invert this or you could just go ahead and select another color scheme as well let's say if I were to go with this one and in this case you can see that the highest values are shown in blue color and the lowest values are shown in this yellowish sort of colors and if I remove this uh invert that has been applied on this color scheme you would sort of be able to get an understanding of how the river network is supposed to look like as those are the points on this raster which is supposed to have the lowest elevation so if I were to graphically sketch out and show you guys what exactly we are going to do in today's tutorial it's going to be something like this as you can see right over here we can sort of see the river line if I happen to pick a point on the river just like this and if I were to sort of estimate what the corresponding drainage area of this point is supposed to look like it should be something like this well I'm doing a very rough sketch so I might not be accurate with my boundary definitely So based on the color variation you should be able to get an idea that the land that's uh contained within this boundary whenever there's a rainfall event due to the topographical variations all the water that falls over this part of the land should eventually end up in these kind of small streams and that will eventually travel into these largest streams and eventually it'll make its way to this point and and the same thing would happen over here as well eventually it goes into this kind of a larger stream and would make its way into a higher order stream and eventually pass through this point and in this case this is going to be my Watershed boundary so I hope you manage to get a grasp on the concept of watershed from this simple sketch and in today's tutorial we're not going to do this manually we are going to get the help of rjs pro to not only get the rivers derived but also the corresponding drainage areas as well all right now let's switch back to arjs Pro and in the process of deriving a set of rivers and the corresponding water sheds we're going to actually have to follow a structured set of steps and the very first step out of those would be to perform a fill operation on this roster now depending on the source that you actually get your elevation data from now I have gotten mine from USGS Earth Explorer web portal so if you're really getting started with a very raw set of elev data there's a good chance that you might actually find this kind of small imperfections in your Ras data set so by doing this fill operation what we are going to do is we're going to basically fill it up so that we would no longer have these kind of syns present in our raster and to do the fill operation what we can do is we can head over to wiew over here and go to Geo processing and from here head over to the toolbox and you can scroll down and go to spatial analyst tools and under hydrology you'd be able to find the tool that we looking for which is fill so well most of the tools that we're going to use especially for deriving the Watershed and the set of rivers is going to be contained within this hydrology tab however if you were to go beyond that and perform any other sort of GIS operation you can basically pick uh any of these other tools that's available for us through aggis Pro so let's uh get started by running this field tool so just uh double click over here and as the input surface roster what I'm going to do is I'm going to select my elevation data and when it comes to the output roster I'm just going [Music] to well provide it with a proper name uh let's call this uh fill roster and after that let's hit run and and uh see whether the tool works correctly or not so you can see that it's going to take a couple of minutes depending on the size of the roster great now you can see that we have gotten this fill roster which is the newly generated raster and if you pay close attention to what these elevation values were before you can see that the top elevation is 3475 which is not changed in this newly created rust but if you look at the the lowest elevation which happened to be 300 previously but now it has been increased to 307 and that actually says that there has been some imperfections or some syns in this previous raster which actually got filled when we put this original elevation data raster through that fill operation and now we have this newly created raster so I would even go ahead and get rid of this because from here onwards this would be the r that I'll be using as my base roster the field roster and any operation that we're going to to perform from here onwards will be performed on this roster so let's go ahead and get rid of this original elevation data roster and I'm not going to change the symbology this time I'm just going to let it have this original color scheme and after performing the field operation the next operation that we're going to perform is called floor Direction which happens to be right over here under hydrology tools as well so just click on Flow Direction and now we're supposed to provide the input surface roster and as you might have guessed we just have only one roster which is this filled roster which is going to be the input roster for this flow Direction tool so let's go ahead and select that and what we can do is we can just go ahead and maybe change the file name to make it a bit uh more descriptive of what sort of a roster we are going to create and right over here you can see that when it comes to the floow direction type we have a couple of options and I'm going to retain this to be d8 and without getting into the vids of it if I were to just uh place my mouse point right over here you can get a very quick description of what each of these different flow Direction types mean now under d8 the flow directions will be determined by the d8 method and this method assigns flow directions to the steepest down slope nebor and as it says over here this is the default method and I'm not going to change that so we're just going to go ahead with the d8 method and click run over here and we'll do a bit of interpretation once we get the output from this operation and and since we have the output uh floow Direction raster right over here we might be able to get into the details of this d8 method and see what exactly we got as this uh flow Direction roster so it says d8 over here and sure enough you can see that we actually got eight different uh classes so so it's fair if you happen to have a guess that having eight different classes might somehow be related to d8 method and you would be right and if you zoom in and start looking at these different pixels you can see that all the pixels have been assigned one of these values and that set of values happen to be one 2 4 8 16 32 64 and 128 and this is what's called the direction coding so right now on the screen you able to see what this direction code actually refers to so all the pixels uh that have been assigned number one that are shown in this sort of a gray color are corresponding to a floor Direction that's towards the east side and alternatively any pixel that has been assigned the value of 16 which is shown in this kind of a blue color has a direction towards the west side so by that definition if you would like to see the pixels that are sort of draining to the north side you would have to look at the pixels that has been assigned uh number 64 which is shown in this kind of purple color and so on so if you didn't really have any idea what each of these different colors happen to mean now I guess you have a very clear idea so it's not just a random assignment of colors each color that has been assigned to each of these pixels does have a meaning and that relates to the direction coding all right so let's head over to the next step what we just created was the floow direction roster and following that the next thing that we're going to create is the flow accumulation Ruster and as the name suggests what flow accumulation rust is going to give us is basically the points or the or the areas where the flow is going to get accumulated which typically happens to be rivers and legs and water bodies things like that so let's go ahead and uh back up one step and we'll head back to the hydrology tools and right over here you can see the flow accumulation tool and as you can see over here the input to the flow accumulation tool is going to be the flow Direction Ruster which is this one right over here we can just drag this and drop it over here or you could have simply just selected it from here as well and the out output I'm just going to name that as flow accumulation and we're going to leave the rest of the settings uh in the default vales let's hit run now this step usually takes a bit longer than the other two steps so if you're not really seeing the result immediately just be patient for for a few minutes all right if you notice we actually got a completely black screen with with a slight shade of a line uh that's running across right over here and if you look at the range of vales you can see that values around zero are basically shown in black color and this kind of extremely high values are shown in white color so if I zoom into this white line that I can see right over here and if I head back to map and pick this explore tool what I can do is I could just uh click on one of these white pixels or in this case it actually looks like a gray pixel because it's very close to this maximum value but it's not the maximum value so if I click right over here what I would be able to get is basically the information corresponding to that particular pixel and you can see that that particular pixel happens to have a value of about 7.6 million so naturally you might be wondering what this value actually happens to mean because in the previous two steps uh we did understand what each of these values happen to mean and in this step you can see that we have started seeing these insanely large values so so what does this actually mean well by definition depending on the location that you select this is going to be the total number of cells of the drainage area that basically happen to drain to that selected point now it might not really make sense just because we can not really see the river Network just yet but uh let's say if I were to zoom in like this and if I get rid of this well let's hide these layers uh for the time being and if I hide the flow accumulation layer as well You' be able to see that underneath in the base map there's actually a river running through and believe it or not this flow accumulation step which we started all the way from our original DM really managed to capture the shape of that River and it's indic indicating that all of these cells are cells that have very high flow accumulation compared to all of these other cells which probably indicates that there's actually a river running through and sure enough if you happen to deactivate this layer and check what's underneath you can see that compared to these small streams there's actually a larger river running through so that's what we are getting from this flow accumulation raster but in case if you're wondering why aren't we seeing any other rivers why do we just see this one single river which happens to have a relatively larger flow accumulation that's because of the way how this color scheme has been defined so what I can do is I can right click and head over to symbology and instead of using a stretch style what I could do is I could uh go with a classify type of a representation and well the color scheme I'm going to flip this back to black and white and in terms of classes Let's uh switch this back to two and right over here you can see that we actually can manually specify values but if I head over to this histogram you can now start seeing that this is value zero and this happens to be the maximum flow accumulation value all the values from zero until this particular value is now being shown in black color and all of these other vales are shown in white color so the reason why you're only seeing these major river lines but not the minor tributaries is because all of those minor tributaries happen to have a value that's within this range and now it's basically is being shown in black color that's why we don't really get to see that so if you really want those minor rivers to show up what you what we need to do is we have to sort of play around with this level and make sure that we actually include those lower flow accumulation vales into this this White Band and not to the black color band and there actually multiple ways of doing that what I prefer to do is usually to go over here and make the changes manually so right now we have a value that's close to let's say 9.6 million I'm just going to put put in 10,000 and see what happens yeah let's head back to the histogram again I can't even see the black color band because all the flow accumulation pixels that are within 10,000 and this maximum value are now being shown and that includes my smaller tributaries as well as the larger tributaries as well and this actually might be a river Network that's bit too detailed in nature so you can always go back and play around with this Valu so if you don't want to go down to 10,000 maybe we could even put in 50,000 and see what happens so definitely you can you can see that uh that detailedness drops down and now we only start basically seeing the major rivers and the corresponding tributaries and if I go as high as even let's say 150,000 you can see that we really did lose some detail but I think for today's tutorial this is actually a sufficient level of detail that I'm looking for and out of all of these Rivers the river that happens to be right over here is basically my R of Interest by the way when this is zoomed out it appears as if the the lines are broken but if you actually zoom in properly you can see that the the line is actually a continuous line well that's not to say that it's actually a polyline feature just yet it's still a raster just that it happens to be a continuous set of white color pixels which is indicative of the river again if you happen to deactivate this you can see that underneath we can see the actual River that's running uh running down like this which actually says a lot about the demm that we selected that explains that that demm is actually sufficiently accurate enough for us to do this kind of a river line derivation as well as catchment derivation which is what we're going to do next all right so the next step is basically to specify a point on this River Line that you would like to have as the outlet of your catchment of your Watershed and I'm going to specify that point right around here before this River joins with this incoming River so I'm just going to pick my outlet to be somewhere over here and to specify this point you would have to create a new Point feature and place it right on top of one of these pixels so that's the way to specify the location of the point so to do that I'm just going to browse to the folder that I'm working in right now let's go to view and open up the catalog Pane and from here you can see that under folders currently I'm working in this folder right here in case if you would like to make a new connection to whatever the folder that you're working in you can right click and select add folder connection and you can browse through to the folder but in my case I happen to uh keep my data right over here so you can see the original elevation data set that we worked with at the beginning so to create a new Point feature I'm going to have to right click on this main folder and head over to new and select shape file and basically just give it a name I'm just going to call this outlet location and quite important the geometry type is not going to be polygon it's going to be of the type point and when it comes to the coordinate system I'm just going to pick the coordinate system of one of these layers basically all of them are having the same coordinate reference system and I'm just going to copy the same coordinate system of let's say this flow accumulat layer which is the wgs 1984 geographic coordinate reference system after that you can go ahead and click run and now as you can see over here we managed to create an empty layer called the outlet location we don't really have any records or features in this layer just yet if you really want to check you can right click and uh go to attributes table and over here you can see that we don't really have any rows over here which indicates that we do not have any Point specified just yet so to specify a point you have to put this into editable mode and to do that you can head over to edit and after that click on create making sure that you have selected the correct layer right over here so hit create from here and over here you can select the corresponding layer as well it's outlet location and after that uh make sure that you have selected this point which is going to create a point feature after that I'm just going to zoom out just a little bit to make sure that I have captured the extent of the river that I'm looking for which is this one right over here and I would like to specify my point somewhere over here before it joins with this incoming River so let's maybe pick this pixel to be my outlet point and after that to finish the specification of point you can just click right over here and finish so if you head over to the attributes table of this layer right now you can see that there's one record which is this one right over here and we just need one record since we are trying to generate only one waterers shed now mind you in few minutes I'm also going to tell you how to create multiple water sheds and when creating multiple water sheds you would have to create multiple points as well well we'll we'll discuss a bit more on that when we get to that so at this point we just have one single point and well I would have to go over to this save button and uh save my edits to make sure that I don't accidently move this point around and let's clear all the selections and we can see our point right over here well if it's not really noticeable what we can do is we can right click and head over to symbology and make sure that we maybe increase the size of this point a bit go to properties pick a color that's uh much more visible and maybe increase the size of the point as well yeah now you can see that it's very clear all right so we made sure that this point lies exactly on top of this cell and as the next step what we have to do is we have to head back to our hydrology tools by heading over to analysis tools and right over here under hydrology you can see that we have the set of tools that we've been using so far and the next tool that we're going to use is called Watershed so as you can see over here the input rust for the Watershed tool is going to be flow Direction rust not the flow accumulation rust so the flow accumulation Ruster was helpful for us to see the extent of the rivers or the formation of the rivers based on the points which happens to have the highest flow accumulation but for this Watershed tool the input is going to be the flow Direction rust which is this one right over here which we can drag and drop it over here and on top of that we also supposed to provide the outlet point the corresponding Outlet point for which we would like to generate the drainage area and that was specified by this outlet location Point feature which I can select from here and when it comes to the PO uh PowerPoint field we don't really have to bother about this much at this stage so I'm just going to let it be the ID and the output roster I'm going to name it as Watershed one and just to make sure that we don't really get any errors with regard to the extent of the generated Watershed what I'm going to do is I'm going to head over to this environments Tab and make sure that my processing extent covers the entire extent of let's say my Flo Direction raster which basically ensures that my generated water shed is going to cover the entire extent of my roster but that does not mean that it needs to have an extent all the way from this corner to this corner it's just a specification of the extend to ensure that it utilizes the raster fully without having any areas cut down all right after that we can just go ahead and hit run and that should actually generate the Watershed correspond responding to this Outlet Point all right now you can see that the water shed got generated however we cannot really see that or we cannot distinguish that from the background because it's drawn in black color what I'm going to do is right click and head over to symbology and well under this uh primary symbology we're just going to select unique values because there's going to be just one value and I'm going to change that to be let's go with the a color like this now you can see that it perfectly managed to create the boundaries of the wed not really getting into the land areas that corresponds to or that basically flows into these other rivers and what you also could do is if you want to see the underlying River you could head over to rasay and maybe increase the transparency just a bit yeah when you do that you would be able to see the underlying River correctly as well now you could actually just take a step further and Export this to be a polygon because right now it's still a raster so you could do things like calculate its area and I think I'm going to do that however before getting into that I would also like to show you guys now this is generating just one water shed now what if you like to create a subcatchments that pertains to these minor River branches that are flowing into this major river and you can control the number of catchments that gets generated by controlling the number of Outlet locations now in this case you can see that I just had one outlet location that's why it basically captured the entire drainage area that drains into that particular Outlet point but if you have multiple Outlets it's going to capture its own drainage area and basically give us multiple subcatchments and that's what I would like to show you guys as well before we head over to the step of uh basically converting all of these generated water sheds into polygons all right so as you might have imagined what I would have to do is I would have to increase the number of Outlet locations in that case so I would uh head back to the same layer I'm not going to create a new layer I'm just going to use the same layer and select edit and create click on this once and this time in addition to this main point I'm also going to create point along these Junctions so let's if I were to pick a point somewhere over here it should basically create a subwatershed or a subcatchment uh that's draining into this River Line and well if I be a bit more specific and put a point right over here and one point right over here as well that should create uh two separate subcatchments corresponding to these two River lines and well what I could do is I could also add another point right over here before it joins this main river because that way I would be able to generate a subcatchment that corresponds to this River Line as well and at the same time let's if I want to have an entire subcatchment for this River Branch before it joins the main river I could put a point somewhere over here and that should generate a subcatchment that looks basically like this and uh let's head up here and maybe add two points because I would like to have two catchments for each of these River lines as well well this one yeah why not we can go ahead and add a point to this River Line as well now again you have to make sure that you place this point before it actually joins the main river that way it would be able to distinguish which river line you're actually referring to and draw the corresponding uh drainage area this River Line I'm just going to let it be and let's say make sure that right over here at this Junction I have put one more point over here so that it'll generate a unique Watershed or unique catchment for this entire thing as well now I think that should be sufficient enough for demonstration purposes after that what we need to do is we have to head back to analysis tools and we we're going to use the water shet tool again and uh input well I would have to go back and save my edits so go to edit and make sure that you have saved your edits and clear all your selections and now if you right click and go to the attribute table well you would be able to see 10 different features right that's the number of points that you created 1 2 3 4 5 6 7 8 9 10 and this time it's quite important that uh each point has its own sort of unique ID now you can see that this under this ID column we have like basically zeros for everything which is not really ideal if you really want to distinguish between each of these different points however under F ID you can see that uh a unique number has been assigned for each of these different points which is starting from 0 until 9 now you could go ahead and edit this ID field and well basically manually type from 1 to 10 I guess and assign a unique value for each of these different uh points or you could just basically rely on this FID column because it has already assigned a unique ID for each of these different points so that's what I'm going to to do so in this case I'm not really going to mess with this ID column I'm not going to manually input a set of unique ID numbers I'm just going to rely on this existing FID and make sure that you have cleared all the selections you don't want to be selecting any one single point during this operation and after that you can head over to this Watershed tool ensure that you have input uh this flow Direction roster and in this time our PowerPoint data set is going to be given by the same file which is outlet location and as I told you guys now we need to be really specific about which column we are going to select over here so if I select ID column which happen to have zeros for basically every point it's not going to be able to distinguish between each of these different points and create its own unique waterers shed and since that's what we after we have to make sure that we select F ID because that that had a unique value for each of these different points and the output rust I'm just going to name this as subcatchments and after that we can just hit run but before that again make sure that you're working at the correct uh extent I'm just going to specify the processing extent to be well the extent of the entire roster we can just pick a flow Direction and it'll automatically pick the extend coordinates of the entire raser and after that select run and just like that you can see that how it managed to generate on unique catchments depending on the pow points that we specified well if I increase the transparency I would be able to see the underlying River lines as well and so let's go ahead and do that go to R layer and increase the transparency and I think I could deactivate this Watershed one yeah that actually gives us a very nice Outlook of how it how things are supposed to look so yes you can see that at this point it managed to generate a corresponding subcatchment which uh defines the drainage area that's supposed to be running through this point and basically it has done for every point that we specified which is basically what we needed and usually one of the next steps would be to calculate the corresponding area pertaining to each of these different catchments and you cannot do that well technically you can but uh it's not that easy to do that when everything is in roster format so that's why you have to convert this into a polygon first and after that we can run one of those geometric calculations on those polygons and obtain the area so let's go ahead and do that and we can head over to the tool box again and this time we'll be using a different tool so the tool is called rust to polygon so you can simply search for itth over here on this search panel and it should be the first one that you get and as you can see it asks for the input rust and this case our input rust is going to be the subcatchments Ruster just drag it and drop it over here and the field is going to be value and I'm going to name this as subcatchments as well and I'm going to retain this simplify polygon sticked because if you don't do that at the edges you will start seeing this kind of a pixelated uh Edge and I don't want that I would like these polygons to be simplified so that in the generated polygon you would actually see a smooth line at the edge instead of seeing this kind of a pixelated Edge well let's change the name of this to be subcatchments polygon and after that click run and just like that you would be able to see that we managed to create the polygons as well so underneath these polygons you can see still the you can still see The rosters and now since I have polygons I could actually play around with the symbology and let's say click right over here and get rid of the field color and maybe have just the boundaries and let's specify the boundaries in this kind of a dark blue color click apply and you can now see that this nice out line of each of these different polygons and not only that you can head over to the attribute table and over here you can see that by default we get uh two different measurements shape length and shape area however you have to keep in mind that uh currently we are working in Geographic coordinates so this area might not really make sense what we have to do is we have to change the coordinate system from a geographic coordinate system to a projected coordinate reference system and after that that we can calculate the area in a unit like square meters so what I'm going to do is I'm going to right click over here and go to properties of my map and under coordinate system I'm just going to pick this uh 1984 web Mercator coordinate system click apply and click okay you can even see that the shape changed slightly now what we have done is we have actually changed the coordinate system of the data frame but we haven't changed the coordinate reference system of any of these different layers so what I'm going to do is I'm going to right click over here and go to data and Export features and I'm going to create a new feature called well let's call it subcatchments one and the reason why I'm doing this is I would like to create a new shape file with this new coordinate system and that's going to be the coordinate system of the current map click on this button right over here you'd be able to see that currently my layer is actually using two different coordinate reference systems and I'm going to pick this one so we have specified the output coordinates and everything seems to be fine now click okay and that should create this new subcatchments file so if you inspect the the two different coordinate systems right click on the original layer go to properties and over here under spatial reference well Source spatial reference you'd be able to see that the spatial reference it's going to be a geographic coordinate reference system that's what it was before and after the conversion if you head over to properties right now you can see that it's a projected coordinate reference system which means that we can work in units like meters over here you can see that the unit the linear Unity is meters and now I can very confidently right click over here and go to attribute table and well it has automatically generated the area for me or if you would like to do the area calculation maybe in a different unit what you can do is you can add a new column like this and just give it a name like area calculation and select the data type to be double you can save the new field after that come back to the original attribute table and you can see that uh that newly created field over here what you have to do is right click over here and go to calculate geometry and make sure that you select the property correctly over here so what you need is basically the area for each of these different items and from here you can pick the correct area so let's say since this has been already calculated in square meters let's see if I wanted to calculate the area in square kilometers or in hecas I could select the coordinate reference system to [Music] be this one right over here and click okay and as you can see it basically generated the area for me in hectors now one more thing before we wrap up this tutorial for today if you would like to create a set of polyline features that uh that would represent this set of rivers as well well you could quite simply do that as well so as the final thing I'm going to generate a set of rivers using this flow accumulation roster so that we could very nicely overly those rivers on top of each of these different catchments and to do that I'm going to use another tool called reclassify so since since we have the toolbox right over here just search for the tool called reclassify so let's pick this tool and what I'm going to do is I'm going to take this flow accumulation roster so let's hide these layers for the time being and I'm going to take this I'm going to take this flow accumulation rust and perform a permanent reclassification now what do I mean by that right over here you can see that I have classified this into two different classes but this is a temporary classification if I were to just remove this layer and then put that back into ajs Pro it's not going to retain this classification the classification that I did over here through symbology was just for visualization purposes but now I'm going to make it permanent by using this tool called reclassify I'm going to use this layer as the input where the reclass field is going to be the value and right over over here based on this set of values I'm going to have just two classes so from 0 until 150,000 we going to have one class and from 150 until the maximum number we're going to have another class and let's name this as reclassify flow accumulation roster and after that you can hit run and that's going to result in a permanent reclassified Ras over here you can see that we just have two classes class number one and class number two which happens to sort of represent what we had or all the pixel values that we had under this class and this class right over here and as you can imagine what we're interested in is just basically all the pixel values that are under number two which is shown in pink color well I'm going to change the colors over here this one to be maybe in blue well just for visualization purposes again and I could put this back to be black and now if I open up the attributes table of this you can see that we have two basically two sets of information so the first one is basically referring to all of these different pixels that are shown in black color and the second row is referring to all the pixels that are shown in blue color which is what we are interested in basically so what I'm going to do is I'm going to make sure that I select this row which means I'm going to select all of those lines and after that I'm going to head over to analysis and tools and I'm going to use a new tool called roster to polyline and after that as the input raster I'm going to drag this and drop it over here ensuring that this row is selected and as the output fly line feature I'm just going to name this as reverse and after that we can hit run and now you can see that it basically generated new shape file of the type polyline and if I go ahead and deactivate all of these flow accumulation layers and these other layers as well well you could see that this is the newly generated uh reverse polyline type shape file well I could go ahead and maybe increase the width to be around two and you can see that it pretty much follows these original River lines uh which can be seen from the base map now it might not be reflective of the path precisely that actually has to do with the errors associated with the DM if you really if you're really working with a very high resolution DM then yes these uh generated D lines will precisely match well technically it should match the the actual location of the rivers but depending on the resolution of the DM that you're using your results might vary just a little bit but as you can see it's not that far off it still traces this uh actual River Line quite accurately and now if I place my catchments on top of this well my subcatchments that should look something like this so with my base map right over here you can see that it basic Bally shows us precisely how my subcatchments uh form and well this well with this 3D Outlook you're really able to see how this particular thing works as a watered where during rainfall all the water that falls Within These boundaries will eventually end up or will eventually flow into this main river and will'll pass through this Outlet point so guys just like what we did if you if you're really interested in calculating the the distances of the rivers you could do that as well because now this this is in in poly polyline format and similar to the area calculations you could actually perform length calculations or distance calculations on poly lines but I think I'm not going to do that in this tutorial because you guys get the basic idea so that concludes the tutorial for today I hope the the steps that we followed were clear for you guys however if you do have any questions add a comment down below and I'll get back to you as soon as possible and if you did like the tutorial you can show your support Always by hitting that like button if you really enjoyed the tutorial and if you think that the tutorial is valuable for you guys and if you would like to stay tuned for this kind of interesting GIS related tutorials you could always stay subscribed to this channel as well so until I see you guys with another tutorial take care and bye-bye

Channel: GeoDelta Labs

Views: 3,532

Keywords: catchment delineation using arcgis pro, how to delineate catchments, how to delineate watersheds, hydrological analysis arcgis pro, watershed delineation arcgis pro, how to derive catchments and river

Id: RFyo_ewHUa4

Length: 45min 40sec (2740 seconds)

Published: Thu Feb 29 2024