The hurricane battered the coast, causing the city to flood, and tens of thousands of people were stranded without food or water. When an event causes great suffering, we call it a cataclysm.
Cataclysm comes from the Greek word kataklysmos, which means "a deluge or flood." So saying something was “a disaster of cataclysmic proportions” is particularly apt when you're talking about a tsunami. Still, people use the word cataclysmic to describe non-watery disasters, too, like stock market crashes, painful breakups, and failed grammar tests.