Creating donut holes without losing existing polygons using ArcGIS for Desktop?

Question

Using ArcGIS 10.1 for Desktop is there a way to do a similar operation to creating a donut hole or island in a polygon without losing the existing features?

I have mapped small lakes as several different polygons based on vegetation type.

However, I want to map the vegetation surrounding the lakes, too - but if I create a circular polygon over the top of the lake and the surrounding area, it includes the area I've already mapped and given attributes to.

So I want to 'cut out' a hole in the middle of the new polygon without losing the polygons that are now covered by it.

Answer 1

Two ways spring to mind. The most efficient depends on how many inner polygons you have.

Clip: Select one of your existing 'lake' polygons then choose clip from the editor menu. Use a buffer distance of 0 and discard the area that intersects. This will clip a hole in any overlapping polygons. You will have to do this for each inner polygon.

Cut Polygon Tool: Select the overlapping polygon then choose 'cut polygon tool' from the editor toolbar. Use the trace tool to draw the outer limits of your inner polygons. This will cut the outer polygon into two pieces. Delete the inner piece to have a hole.

Answer 2

If you don't mind doing this manually:

Start editing in ArcMap.

Double click on the feature that needs holes to start editing the vertices.

Find the continue feature tool that pops up (read http://resources.arcgis.com/en/help/main/10.1/index.html#//01m800000039000000).

Right click and select finish part to tell ArcMap you don't want to modify the existing boundaries but add new parts to it.

Activate the trace tool from the editor toolbar and trace around the existing polygons you want to cut out, one at a time, and after each one right click and finish part.

Finish the sketch and the polygon now has holes.

If you forget one go back to the continue feature tool, if you add one in error then delete the part from the sketch properties (can be hard to find).

Beware: if you make a part in/part out hole you will create a non-simple feature, this edit will be rejected by SDE and cause problems later in other feature class types; if you want to have a void that extends outside the polygon use the reshape tool.

Answer 3

I think it is much easier to use the Erase (Analysis) tool, it does exactly what you want: delete from a larger layer a smaller layer, so for two circles creating a doughnut.