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I'm a very new ArcGIS user currently working on my first project regarding chemical spills on land.

The Background:

Software that I have to use is ArcMap.

Currently, I am trying to use the pour-point tool to delineate the flow path from a proposed spill/leak point of a chemical bearing pipeline.

So far I have used only the Hydrology Toolset and this is what I did in sequence...

  1. Filling the LiDAR Data
  2. Generate Flow Direction
  3. Generate Flow Accumulation from the Flow Direction
  4. Delineate the drainage Basin and also turned it to polygon features to outline the flow accumulation passages.
  5. I created a new point shapefile and assume it as the "proposed leaking point" (Please view the hand drawn diagram below)

The problem:

Firstly I measure by estimating the distance of the "proposed leaking point" to the nearest flow accumulation line (12m). Then I run the snap-pour point tool with a little addition to the measurement (snap-distance: 15m). After it transforms the point shapefile of the "proposed leaking point" as a pour-point (as shown in blue in the diagram below) and snapped it to the nearest highest flow accumulation point... I then use the watershed tool..

However... This only delineates the whole stream (watershed) which contributes to the pour-point. This is not what I am looking for as it is not taking into account the "proposed leaking point".

The Question:

How do I get the delineation or the flow line of the chemical from the "proposed leaking point"?

enter image description here

ArcMap is not working so I had to draw this.

Edit: Additional Images

enter image description here Image above shows the pour-point that creates a watershed of the contributing streams.

enter image description here Image above shows where I would like the flow line to be if there is a leak at that point of the pipeline.

Nusi
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  • Do you also have soil permeability as a layer? Flow direction will show you which way the spill will go but needs to be reduced by how much 'soaks in'; note you should also know the size of the spill, otherwise everything downstream is affected, like creating a drainage line from a pour point. After you've worked out that factor it should be the same as creating a mini watershed with the user pour point. – Michael Stimson Oct 09 '17 at 01:37
  • Ahh I have not added the soil permeability yet.. If im not mistaken will it will be done by inputting it as a weight raster when I run the flow accumulation tool? Also in regards to the size of the spill... the project is for the case when a chemical spill may occur in the future so Im creating something to prepare for that thus Im unsure of the size of the spill :S – Nusi Oct 09 '17 at 02:13
  • I'm not sure how you would implement it. One thing to be aware of though is if chemical X is saturating soils and is hydrophilic it could come out in the next rain event and pollute downstream but if chemical X is hydrophobic it should stay right where it is. Another massive assumption is that the permeability is the same for chemical X as for water. You could have a look at https://gis.stackexchange.com/questions/114947/calculating-flowpaths-downstream-of-a-point which might give some guidance. – Michael Stimson Oct 09 '17 at 02:21
  • Tracing flow path downstream is very basic thing to do. Specify point as destination in cost path tool (plus flow direction). However in my opinion it does not represent spill. The best simulation of a spill using GIS only I found at William Huber site http://www.quantdec.com/SYSEN597/studies/flood/index.htm – FelixIP Oct 09 '17 at 02:34
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    Welcome to GIS SE. As a new user, please take the [Tour], which stresses the importance of asking one question per Question. You have at least two here, which makes this too broad for our 'Focused question / Best Answer" model. Keep in mind that we are more of a problem-solving site, than a tutorial one, so you should include information about the exact release (and license-level) in use (along with any extensions), what you have tried, and what problem you have encountered. – Vince Oct 09 '17 at 02:36
  • https://gis.stackexchange.com/questions/228942/automated-mapping-of-cost-paths-from-multiple-origin-points/229068#229068 – FelixIP Oct 09 '17 at 20:02

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