So, you want to build a 100% fenced border and all the costs that entails up and over 200 foot tall sheer canyon cliffs, and through salt marshes. You want to cut off drainage for farms during heavy rainstorms.
WTF do you know about the border?
One of the things we know is that a border fence, however expensive, is cheaper than being invaded. The fence is only needed, of course, where there aren’t natural obstacles—the “canyon cliffs” and “salt marshes”, where they exist, can take care of themselves.
As for drainage, if your farm’s drainage requires leaving your country open to invasion, you’re going to have to stop farming and get a job.