I'm not an expert and in my hiking ,fishing trips didn't require this but noone mentioned a gas mask . If is going to be a natural disaster ,volcano eruptions ,fires ,explosions or even military strikes a gas mask could be the diference between life and death . I noticed that everyone is ignoring the gas mask including me and all the others when I was in the mandatory army service .
I allso think is good to have food and water for a few days but is better to have the meens to get them for a longer time ,much longer then 72 hours . You saw what happent with Katrina ,and don't forget that it happent in the most developed country ,wit enormous resorces of all kind . Here I would expect any help from government if somthing big comes up .