こうずい洪水kouzui
1.

A natural disaster that occurs when excessive rainfall or snowmelt causes river water levels to rise rapidly, overflowing onto nearby land and impacting the surrounding area.

2.

A sudden and overwhelming surge of water from a waterway, often leading to extensive inundation and damage in the floodplain.

3.

A scenario where a large volume of something, such as people or light, emerges in a rapid and overwhelming manner, similar to a flood-like occurrence.

Example:

洪水がその村を飲み込んでしまった。

だいこうずい大洪水daikouzui
1.

A catastrophic and overwhelming inundation of land, typically resulting from excessive rainfall or natural disasters, often associated with divine retribution or significant mythological events.

2.

A large-scale water overflow that leads to extensive damage, often referenced in folklore as a means of cleansing or punishment by higher powers.

3.

An event characterized by the rapid accumulation of water in areas usually dry, which can disrupt communities and ecosystems, frequently depicted in cultural narratives as a significant turning point in history.

Example:

家が数軒その大洪水で流された。