ALA's current FAQ has Katrina as its number one question right now. It's at: http://www.ala.org/ala/contacts/alafaq/faq.htm
Their Hurricane Katrina News page (library/museum news in the wake of Katrina) is at: http://www.ala.org/ala/alonline/hurricanekatrinanews/katrinanews.htm
I didn't cry until I read parts of that page. Somehow the line "Long Beach Public Library destroyed" got me right where it hurts.
I hope things like old, valuable manuscripts were in watertight vaults and/or evacuated. Most libraries' disaster plans (if they're any good) include who will take what where when, as in, "The Director will remove the X historical collection, call numbers Y to Z, to the ABC library or to storage in such-and-such city". Small public libraries/branches won't have as much irreplaceable stuff, but one would hope they also have plans for removing/placing up high things that can't be replaced.
Water damage in libraries is a whole area of study unto itself. I suspect in the case of Katrina there are going to be more cases of "it's not damaged, it's just all gone
" than there will be of items merely being damaged. In practical terms, books that are merely wet can usually be salvaged if there is staff to oversee the process and space to air them out; libraries with excellent disaster plans have contracted for space in conservation freezers owned by various companies. (That means mostly academic libraries. Public libraries don't have the money for this.)
Over time mold is a huge concern, too, in damaged buildings and damaged books--I have seen regular books in perfectly safe, air-conditioned libraries sprout mold overnight for no good reason. Imagine if there is no power in a library building for a matter of weeks, no space to separate the materials and air them out, high humidity indoors and out, no staff to begin the effort because they are refugees in other areas. Once mold attacks a book you have to get rid of it, because it isn't usable and mold spreads. So, I think even libraries with their roofs still attached, if they have standing water or even a few leaks, will have serious problems and have to pitch a lot of their materials.
Finally, FEMA does have basic tips on salvage/conservation of valuables at: http://www.fema.gov/ehp/salvage.shtm
, with a section on books/paper here
. Notice their emphasis on freezing paper items. This is the state-of-the-art mold prevention response. Tough to do with no electricity...