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Question
I have "lakes" added inside my research area, and I have prepared the polygon shapefile for my model domain in QGIS.  

I get an error message saying “Warning: Polygon #2 dropped since overlapping with polygon #1", when I import the polygon shapefile and convert it to supermesh - see Fig. 1 and Fig. 2.

Why? And How can I solve this problem?

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Fig. 1 - Import and convert the polygon shapefile
 

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Fig. 2 - "Warning Message: Polygon #2 dropped since overlapping with polygon #1!" 


Answer
The error indicates that some of the polygons are completely located within another polygon (like an enclave). 

There are two solutions: 

#1: Work in GIS 
Before converting to FEFLOW supermesh automatically, check and modify the shapefile maps in ArcGIS/QGIS to make sure there is no overlapping polygons. 

#2: Work directly in FEFLOW  
Create the supermesh manually instead of converting to FEFLOW supermesh automatically
Simply set the shapefile maps as a background in FEFLOW. Make sure there are no overlapping by tracing every polygon using "Add Polygon" and "Split Polygon" manually. Avoid any polygon which is completely located within another polygon.  

Fig. 3 shows an example of overlapping polygon

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Fig. 3 - Overlapping polygon


Fig. 4 shows an example of how to set the correct polygon - the inner polygon must be connected to at least a second outer polygon without overlapping.   

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Fig. 4 - The correct polygon 

 

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