Complex sentence: Severe flooding of its tributary rivers from July 18-21,1996, devastated the region and proved one of Canada's costliest natural disasters, now referred to as the Saguenay Flood.
Split into simpler sentences: Severe flooding of its tributary rivers from July 18-21,1996, devastated the region. One of Canada's costliest natural disasters, it is called the Saguenay Flood.