I am a generalist developer getting the hang of basic GIS. I made this GeoJSON map by clipping and converting different shapefiles. The problem is that the precincts of New Orleans extend into the Mississippi river. I want them to stop at the river. Is there any easy tool or method to get the shapes from not overlapping? The borders of the precincts should end at the river. The precincts should not extend into the river. I am using all open source tools.
At this point, I can see that you have lines for the boundaries of your river. Here is what I would do if I had your problem:
1) Manually edit your river lines in order to "close" it.
2) Convert this feature class to polygon
3) Erase the river from the parcels
Best way to ensure the integrity of your GIS databases for your project in a Open Source way, it's by working with Topology for your PostGIS database.
In your case, you should have two separate layers (polygons): land parcels and the rivers. Then with PostGIS Topology, you could identify and fix when "two polygons must not overlap".