Difference is, the flood wont be around in a few thousand years.
Wrong. The Fukushima exclusion zone will be gone long before the dam, let alone a thousand years. Thats pure propaganda. The most active isotopes are long gone now, leaving caesium-137 with a 30-year half life.
That will affect the area for centuries, but not so much as you think.
Chernobyl even, is only "uninhabitable" by law. Hundreds live there illegally, and no-one has developed a 3rd eye or superpowers yet. Background levels are getting low (less than on a commercial flight), though hot-spots remain.