Iterating watershed over multiple points to obtain overlapping polygons.

05-26-2021 02:38 PM
New Contributor

Hi, I have 4000 points features that I am looking for a way to calculate the contributing area for separately. These are representing drains in the urban water system on the mainland. Hence, overlapping polygons are  and an independent calculation of the watershed for each point is what I am looking for.

The watershed tool  alone provide me with the wrong answer and I have tried approaching  with a small model which I have pasted below.


Bok25.csv is essentially a list of of 4000 street drains containing an ID number and the coordinates. My problem with running this model is that all 4000 points are snapped for each iteration (I think) and that the file is overwritten each time. What I am looking for is a way to run the "for loop" below 4000 times:

1) Select only one point from the list

2) Snap only one point to a highly accumulated cell within 1 m distance

3) Calculate the contributing area for that one point

4) Store the value of contributing area in a list or .shp with the ID so I can identify which drain has what contributing area. 

Would also be very convenient if the loop stores all polygons or values in one list or shp so I dont have 4000 separate files. 

I am using ArcMap 10.8.1 desktop application. Is there a way to do this? I have been browsing around the forum for a while and could not find anything. I also contacted reddit with no luck. 

All help is much appreciated as I have spent many hours trying to figure this out. I am new to ArcMap and just recently noticed the model builder. Other input on methods such as toolboxes to acheive my goal is also much appreciated. 

Wish you all a good day. Hopefully I am in the right thread. 

Kind regards,

Frustrated master student 😉

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2 Replies
MVP Esteemed Contributor

Could you take care of the following?

1. Don't use the event layer as input. Export the Event Layer as a File Geodatabase Feature Class. Use the File GDB Feature Class for iterating feature selection.

2. Ensure that no field is selected under "Group by Field" option.

3. Use in-line variable substitution  to define the final output. e.g. C:\Watershed\wshed_%Value%.tif

Think Location
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New Contributor

Hi thank you for replying!

I tried to export to a File Geodatabase Feature class by exporting but it would not let me for some reason. I just hit -> export -> and changed the file format. Did not work for some reason. 

Regarding point 3. in you're comment. Would not using %Value% create 4000 files which is ultimately what I do not want? 

Might be a lot to ask for, but would you happen to know how I can implement pour point into here? Is it maybe best to just snap all points first then do the iteration?

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