I'm using ArcGIS 10.4.

I have a shapefile that has many catchments in it. I wanted to dissolve all these catchments to get just the boundary of the study area.

I used dissolve to do so

enter image description here

The problem is that I have found traces after I dissolved all polygons as below

enter image description here

How do I get rid of these traces?


You can download the shapefile from this link.

  • 1
    Can you zoom in a lot further on one of these traces, please? And on the original data at the same extent.
    – PolyGeo
    Apr 23, 2017 at 6:18
  • @PolyGeo Please, check update
    – shiny
    Apr 23, 2017 at 6:56
  • I still cannot see whether these "traces" are lines or polygons or what linework they came from. I need to be able to compare input vs output before I can start to think about what may have caused them.
    – PolyGeo
    Apr 23, 2017 at 7:32
  • 1
    Feature to line, feature to polygon using 1 selected
    – FelixIP
    Apr 23, 2017 at 7:49
  • Try creating topology. Use Must Not Have Gaps for the rule. This is probably the safest way to identify problems which our eyes cannot detect.
    – blu_sr
    Apr 23, 2017 at 13:19

2 Answers 2


Due to topological errors in the smaller catchment polygons, those lines appeared after dissolving. You can delete the lines appeared inside the dissolved polygon manually using Delete Vertex from the editor tools. Deleting vertex tool can delete a vertex or multiple vertices at a time to reshape the feature. To do that:

  1. Click the Edit tool on the Editor toolbar and double-click the feature you want to edit
  2. Click the Delete Vertex tool on the Edit Vertices toolbar and click the vertex you want to delete.
  3. If you want to delete multiple vertices, click the Delete Vertex tool on the Edit Vertices toolbar and drag a box around the vertices.
  4. Save edits.

The link above shows also the icons in the Edit Vertices toolbar that you can use to accomplish your task.


Try tool Integrate:

Integrate is used to maintain the integrity of shared feature boundaries by making features coincident if they fall within the specified x,y tolerance. Features that fall within the specified x,y tolerance are considered identical or coincident.

Set the cluster_tolerance variable as small as possible.

Be sure to backup your data prior to running the tool since it will modify you data.


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