mega issue: "fix" broken contours in IA, ND, and IN hypsography datasets

[jordansread]

We have a number of contours that may need to be manually fixed/closed in QGIS or something else (not sure of a method to do it programmatically) where the contour lines end without connecting back to themselves. This causes us to either have to drop the lake or drop the contour ring. We may be losing some valuable lakes because of this.

[jordansread]

Examples: broken polygon rings which don't close since these are linestrings. Also, casting to polygon may work, but accidentally subtract area because of node ordering (?)

[jordansread]

@hcorson-dosch no need to look at this for a long time, but just putting it on your radar as a topic to discuss in the project.

Perhaps you have an approach you could recommend for this particular problem.