I guess you could sue but that's risky and FEMA might have the court records sealed for cases that went against them so it will be hard to get a history for this type thing.
It'd be useful to find out what people did in similar situations in the past but how would this even be researched? Civil engineering journals might have examples of successful outcomes and you might look for a journal that publishes cases of the Army Corps of Engineers.
How much to clear this mess?
By what method?
How much for a new road?
How much is that per head?
"class n. in legal (not sociological) terms, all those persons in the same category, level of rights (e.g. heirs of dead person who are related by the same degree), or who have suffered from the same incident. Whether a person is part of a class is often crucial in determining who can sue on behalf of the people who have been similarly damaged or collect his/her share if a class action judgment is given. (See: class action)"
Also, if there is a law library nearby you could look up caselaw for this type of thing.
They helped me once on an employment law issue.
If you get bids you are 100% sure of paying that price. If you sue you are maybe 50% sure of paying some big bucks and it may last for years so the expected cost or 'expected value' of a lawsuit is difficult to calculate.
It'd be good if you could get this situation into the papers or on TV.
And I thought I had troubles.