A disaster that is difficult is particularly difficult, making it more of a misfortune. Obviously a disaster that wasn't difficult wouldn't really be that bad, so a difficult one gets the "misfortune" or calamity label.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
Fortunately, I was overseas at the time, so I was able to escape the disaster.
Today at school I learned a proverb that goes, "calamity is the touchstone of a brave mind."
I wonder why misfortune is always following that guy? Is it just by chance or is there something wrong with him?