The theme you are likely to encounter only in a text responding to Hurricane Katrina and not in a text responding to 9/11 is environmental issues following a natural disaster.
Hurricane Katrina was a natural disaster that involved significant environmental factors, such as flooding, erosion, and the impact on ecosystems. In contrast, 9/11 was a terrorist attack, and while it had profound social, political, and humanitarian implications, it did not involve the same type of environmental issues associated with natural disasters.