水灾用英语叫做 "flood"。来源是拉丁语 "fluctus"，意思是 "涨潮"或 "汹涌"。例句如下：

The heavy rain caused a flood in the city.

（大雨导致城市发生水灾。）

The flood destroyed many homes and businesses.

（水灾摧毁了许多家庭和企业。）

Many people were stranded by the flood and had to be rescued.

（许多人因水灾而被困，需要救援。）