disaster

災害(さいがい)	A TV news-worthy disaster:tornado, tsunami, earthquake.

災い(わざわい)	A personal misfortune:house burned down, father had a stroke.

災難(さいなん)	This means disaster in the sense of ‘How was your trip to Tahiti?’ ‘Oh my god, it was a total disaster!!! First we missed the plane, then I got an infection, then on top of all that our hotel was run by zombies!’ 災難　 carries the sense of a bunch of random unconnected misfortunes. It never rains, but it pours, kind of thing.