How to clip/intersect a shapefile (with multiple overlapping polygons) to another shapefile boundary while keeping unique shapes

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02-03-2021 02:09 PM
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mw-
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New Contributor

Hi there, 

So I've run across this issue where I have a shapefile with multiple overlapping polygons (unique forest disturbance events) and I need to clip it to specific boundaries within another shapefile (watershed extent and their different boundaries). Since each event has a different year and ID, their coverage or extent over the same watershed varies (should be clipped shape and areas are visually different).

See: Polygons1, Event 1 and Event 2 photos.

I've tried running clips and intersects, but clips amalgamate all of the unique events into one coverage event per watershed and intersects, while keeping all unique events (e.g., Event 1 2003 and Event 2 2017), merge overlapping unique polygons (from the raw data) into the exact same output polygons in regards to shape and therefore, give different events identical area calculations, which cannot be true.

See output problems for intersect: Problem 1, Problem 2, Problem 3.

What my solution needs to look like is each unique forest disturbance polygon needs to have its own output polygon (clipped to each watershed boundary) so I can calculate the percentage coverage for each event in the watershed it occurs in! I've been to my library GIS Lab to go over this and they recommended for me to try this with the "Extract by Mask" tool, but my input data is not raster so I am a bit confused? I am even approaching this correctly?

Also: every layer is projected to the same coordinate system and nested within the same geodatabase (I have multiple forest disturbance layers that I am working with).

Any help or suggestions are greatly appreciated, thanks!

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DanPatterson
MVP Esteemed Contributor

An overview of the Extract toolset—ArcGIS Pro | Documentation are the basic overlay tools

How Pairwise Intersect works—ArcGIS Pro | Documentation describes the differences in outputs between the traditional intersect and pairwise intersect.  Have you had a look at that or is it the first clip that is important?


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DanPatterson
MVP Esteemed Contributor

An overview of the Extract toolset—ArcGIS Pro | Documentation are the basic overlay tools

How Pairwise Intersect works—ArcGIS Pro | Documentation describes the differences in outputs between the traditional intersect and pairwise intersect.  Have you had a look at that or is it the first clip that is important?


... sort of retired...
mw-
by
New Contributor

Hi Dan,

Thanks for the reply and info. I've looked over those tools and believe that the pairwise intersect worked! That is exactly what I needed ArcGIS to do - solve each unique event one at a time, so thank you. I believe how the regular intersect tool works by intersecting each overlapping layer in my forest disturbance input was causing problems and creating many more output features than actually existed.

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