Is there such a thing as a natural disaster?

Is there such a thing as a natural disaster? If so, what are the criteria? I'm thinking of flooding. I learned in history that every year the Nile River flooded in Egypt. The people evacuated to higher ground. When the flood was over, they used the flood plains for farming. It was natural irrigation. If they had refused to evacuate, would that make the flood a "disaster?" Isn't that like saying every time it rains, the rain is a "disaster?" What about sunlight? If you don't wear sunscreen and you get skin cancer, is a sunny day a "natural disaster?"