stream / river extraction from DEM using ArcGIS
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- čas přidán 28. 12. 2017
- how to extract stream / river network from DEM using ArcGIS. This is the second part of my watershed analysis tutorial in ArcGIS . For the first part, kindly check : • watershed / river basi...
if you want to get the stream / river order (strahler, shreve or horton), here is how : czcams.com/video/zqp4PxTjCPk/video.html
I did have words to say Thanks , great work
Great video!
Thanks
Hi, great video! Just one question: on which base do you establish your threshold value for the Con tool? Thank you!
Nice question mate, because I made this video for technical education (how to) only, I dont have any consideration or references to determine the threshold value,
But in real life real application, things became complex. To get a value that represent the real life river networks, you at least must have reliable consideration, like existing river network data (which can be used to assess the modeling result) or field knowledge.
DEM quality also affect almost anything in the modeling, sometimes best result cant be achieved because we didnt have good quality DEM
@@GEO2004 Thanks fro replying me....I permit to continue just because I read something around, yet it's not so clear to me. Therefore, I have a DTM (8x8) and the river network in shapefile (its values are the length, type and origin-end point), yet I would like to extract from the DTM the river network in order to have a more complete datum (the aim is to use the river network into the path distance tool in order to gain a path able to use the rivers too) . My question is: how to do this? I mean, I could follow your tutorial and it's ok, yet I need the aforesaid value to use in raster calculator. Do you have some detailed tip to give me (yours, paper or what else)? Thank you for your time!
@@robertofilloramo1703 my master thesis is also using path distance tool. i was using it to generate least cost path for highway route planning. I also involve river network as one of the inputs to generate cost distance raster. If you have existing river network in vector format, why dont you just convert it to raster instead generate the raster river network from your dtm?.
@@GEO2004 I did it, yet some books did not appear in my shapefile therefore I wanted to have a more complete datum extracting a new river network from the DTM
@@robertofilloramo1703 you mean you want to get the elevation value for every cell of your raster stream network? If that is what you want, the best way to do that (in my opinion) is.. you are right, it is better to get it from your DTM using stream extraction like what I shown on the video, it is more coherent, and to get the best threshold value, you can play it around by perform trial and error, until you get the most satisfied result (a river network that pretty close to your existing shapefile river network), It will be difficult, but if your DTM is very accurate and good, you will get it in no time :)
you can also tweaking further the extraction process by (1) involving Pour Points to control the flow direction process, (2) fill all sinks and depression prior to flow direction computation, (3) clip the DTM into segmented watershed/basin and perform separated river extraction for every watershed (piecewise approach instead of global approach). Hopefully my explanation is quite clear :)
I think this is very good.
Hi I would like to ask. Which Dem inage should I use to process this? I would like to do a drainage density map. I just processed Dem and clip it with my polygon area. Do I have to extract TIN?
any DEM will do it. If you like to make a drainage density, seems you should do more processing steps. For example, based on what I show on the video, you can make river/stream networks and export it to polyline vector, and after that you can perform density mapping ( in ArcGIS you can use Line Density Tool). No need to make TIN. Unles your data is came from TIN format.
@@GEO2004 noted. Thank you for the answer. :)
Can l ask wats e most easiest way t extract flood depth from a digital elevation model using arcgis
Hmm, unfortunately I also dont know how to do it, but I am going to explore it when I have some spare time, may be I will make a video if I find it
for the Con expression, how do I know what certain accumulation value to place into the expression "value > "
By trial and error, I dont know the best way to get the exact value, because the value will be different for every region or every DEM product
@@GEO2004 How do we come to know at which point our trial and error should come to an end... I mean, when can we say that we have achieved the correct stream network at some stage of trial and error process. Kindly reply.
I cant say for sure but to some extent you use reference data like river network map produced by official agency,
Basically it is just the nature of the algorithm, you set a parameter, you get a result, if you are not satisfied, you can tweaks the parameters, you know what I mean?
@@GEO2004 Yeah Got it. Actually I need to produce this accurately as an input for ArcSwat and whenever I upload a river network layer while doing watershed delineation process, it produces an error. It has happened many a times now and I couldn't understand how to reach to a suitable output stream file. Maybe I am missing out on something. But Thank you for responding.
Ah yeah, I never use arcswat so I cant help you on this one
hye, please help. i manage to do until flow accumulation. i cannot extract using con. it generate a single color box image. no stream. what should i do?
Check again your conditional sql query, may be your syntax is not correct
thank u so much!
You are welcome
Thank you for you great work! Since I am not an English native speaker, I wonder what does 'depressionless DEM' mean？
Haha sorry, I actually not a native speaker too, I dont know if depressionless is a formal word, what I actually mean is a dem that has no sink or no void pixel (imagine a small pond or lake) which all the water flow going there without a way out
@@GEO2004 Oh I understand. Thank you!
one question:the "flow accumulation tools" takes forever to run, is it possible?
there is always a possibility, your extent, your DEM spatial resolution, your DEM Bit Depth, your Hardware computer, have significant roles to processing time,
it would be more helpful if you describe clearly what your problem is
@@GEO2004 up until now it's been 12 hours my processing is running and the result for flow accumulation still unknown. the DEM is derived from LiDAR point clouds which in 0.25m resolution. the area covered is in 18kmx18km.
seems, you need more RAM and fast CPU to do that in fast way, if you can access arcgis desktop 10.6, you may use that version because at newer version, they offer parallel processing, if you have latest version of arcgis pro, that would be better because it works on 64 bit, so your RAM capability will be used in full mode.
another solution which I could suggest is try to resample the DEM to coarser resolution (maybe 1 or 2 meters) and try to process that and monitor how much time needed to finish the process. if at coarser resolution it still needs quite amount of time, you can imagine how much time needed to process at super fine resolution like 0.25 meters
@@GEO2004 Thank you, I should do the resampling part first. Actually my PC's RAM is 16gb with processor i7. that should no problem, right? Is it because of the Arcgis version? (Mine is 10.3)
@@nurafiqah5296 yes, the hardware shouldn't be a problem, I guess it is related to your data
after run the flow direction tool, in the layer FlowDir its appears like unnatural inclined line, but its doesn't exist when I skip Fill tool to make depressionless DEM,its that Okay?
Thats fine, fill sink is only optional tool, sometimes the tool could introduce unwanted effects
@@GEO2004 thank you for the reply, but I facing up other problem, try another coordinate system (projected coordinate system, previously I use geographic coordinate system) with Fill Tool and have result red cross icon and no layer showing up, and it's happen to all layers I try latter, always red cross icon showing up. any clue for this
@@TheRofidac which coordinate system?, if the coordinate system using non cartesian map unit, it is likely will causing error
@@GEO2004 projected coordinate system I use: DGN95_Indonesia_TM_3_zone_49_1, and for Geographic Coordinate System I use: GCS_WGS_1984, re install and trying multiple time, and its work.
I tried same procedure but my length of the river is not showing in meters. I projected my dem, converted to tin but not showing in meters please solve my problem
which projection you are using ? may be I could help from there
WGS_1984_UTM_Zone_44N
First thing before you change the projection, make sure your data has valid projection (if it is not valid, the source tab in the layer properties will says the projection is unknown), and if it is unknown, you must know the original used projection of your data, then assign in using DEFINE tool in the arctoolbox, then you can REPROJECT it from there
how to clip DEM exactly for required basin from say, DEM of asia.
I already made tutorial how to do that, check czcams.com/video/ue0QSaUoriU/video.html
Hi,could you introdues me new method extraction sinkhole from DEM please?
have you tried Sink Tool available on Spatial Analyst Toolbox?. It uses Flow direction result as only input. That tool might not perfect, but worth of try
@@GEO2004 Tanks for your help,but I'm looking for a new method for extracting Sinkhole from the DEM, like Hao Chen's article
@@paryaazarboon7187 sorry, never explore that
Hi! The con function is not working for me unfortunately. Why would that be?
Usually it is because you are not yet activate the spatial analyst extension
@@GEO2004 I’ll give that a try. Cheers and thank you for replying!
already welcome!