Overhead damage from water such as a roof leak, or air conditioning unit should be considered an urgent issue. There are two aspects that can make this more of a concern than ground level flooding, contamination and structural integrity
As materials soak up water, such as dry wall, they become weaker and quickly become a risk of falling. Its important to dry or remove these risks as soon as possible.
Another concern is contamination. Even if you have a clean water source, as water passes through your insulation and other various contaminates in the attic it can become a health risk.