A flood — an overflow of large amounts of water that inundates land, such as river flooding or flood disasters due to heavy rain.
大雨で川が氾濫し、洪水が発生した。
The river overflowed due to heavy rain and a flood occurred.
洪水の被害で多くの家屋が流された。
Many houses were swept away by the flood damage.
洪水対策として堤防を強化する必要がある。
It is necessary to strengthen levees as a flood control measure.