Complex sentence: Hurricane Katrina of the 2005 Atlantic hurricane season was the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States.
Split into simpler sentences: Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States.