What I am saying is that the people that decided to build and live in the American Bottoms did so of their own free will. Building in a flood plain has risks and the inhabitants chose to take those risks.
My explanation simply was meant to show that prices are generally cheaper below the bluffs because of those, among other, risks. Someone that chose to live on the bluffs and paid more to escape those risks should not be penalized for doing so. My reply was in answer to your observation that roads and other developments are causing water issues is somewhat vague to me. Granite City has had its share of development over the years as well. None the less buying property in a flood plain is risky and is priced accordingly. WHy expect others that take measures to avoid those risks, at extra cost to them, now be penalized for doing so?