I can't say re FEMA's work sheet nor what other agencies are involved in other states. Through recent experience I can only speak to what's happening here in CA. CalFire is using its personnel with boots-on-the-ground to survey damage and record the Lat and Long of eye-balled damage and destruction then transferring the data to street maps it posts on-line. When clients come to us (and other ngo's) for help, we verify that they have/had a residence that was destroyed.
For answers as to who is doing what in the area of disasters (e.g., the flooding you mentioned), I think the best source would be the OES for affected county(ies) and state. That's where the responsibility starts.
When I responded a couple of years ago to the Sabine R. flooding in south TX, the local JP declared what areas were "totally destroyed." So, we went accordingly with the addresses in the zone/area he declared.
I'm guarded re what might be included something like flmsg (or Winlink). We, the ARC, has a data base known as "The Exchange" that is a compendium of everything from sop to nuts for disaster response, including forms and worksheets. For example, there is the Safe and Well individual registration form that can be filled out either directly by a client or with the help of an ARC volunteer. Then there is the Safe and Well "Helper" Excel spreadsheet for compiling registrants and forwarding upstairs for posting to the S&W web site. (Recall if you were solicited by the ARRL to go to Hurricane Maria/Puerto Rico to forward this spreadsheet.)
Hope that helps.