Except for the design flaw pointed out by Roger, your idea for the rebuilding of New Orleans is spot on, Pat.
Speaking as a geologist who did some study of New Orleans long before the Katrina disaster, any rebuilding of New Orleans that does not seriously consider the fact that large parts of the city are below sea level, and that many of those areas are subsiding daily even farther below sea level, and that the dikes surrounding the city were inadequate (and still are), and that it is only a matter of time before they are again breached and the city will again be flooded -- is doomed to failure.
So, Pat, it is unfortunate that the federal, state and local planners now attempting (sorta) to rebuild New Orleans don't consider your suggestion seriously -- Well, on second thought, maybe those particular arks illustrated in your post, were designed by those planners -- who else would build a door below the waterline!! -- perhaps only those who would rebuild a city below sea level.
