As terrible as it seems, tragedy is a great buyer of stock images. Following Katrina, there were so many sites looking for pictures, not just of the event itself, but of a generic nature.
Who would want such images?
Well if you did a Google search for Katrina you might be able to see who and why was a buyer of the images.
On the right here is an image from successful photographer Lisa Young. This sort of image would do well with DIY companies and even Home Depot.
Of course images of the actual event sell, and they have deeper uses other than editorial.
You might find a lot of engineering companies who do an explanation of what went wrong, and their suggestions to fix it, or to highlight a solution they might have for other low lying flood areas around the world.
So do not imagine you are being sadistic by capturing these events. You are a story teller who has an obligation to capture things as you see them.