I had the same question you did about flooding at Hannibal that you did
after seeing a CNN report yesterday (July 4) morning.  They said nothing
about the museum or the other Twain buildings which interest me.  NBC
Nightly News answered the question today.  A levee has kept flooding from
the
museum and businesses in the heart of downtown.  Some residents are
understandably angry that the levee could protect buildings there and not
in their neighborhoods; but one official said that the levee was too
expensive even for the area it covered and could not possibly be extended.

Life on the Mississippi is apparently just as interesting as it was in
Twain's time.

David Tomlinson