KanjiJLPT N1
Flood

deluge, flood, vast

Mnemonic

A massive storm pushes all the rivers together into one unstoppable surge—a flood. The storm merges every stream together into a single roaring wall of water that devours the entire valley below.
Additional thoughts
Picture countless tributaries forced together by storm winds, converging into one colossal flood wave. The togetherness of the waters is what makes it catastrophic rather than ordinary rain.
Quick recall
A storm forces all waters together into one devastating flood.

Details

The keyword for 洪 is flood. This kanji refers to a great deluge or overwhelming rush of water, particularly the kind of massive, devastating inundation that submerges vast areas of land. It conveys a sense of enormity and power beyond normal water levels, often associated with catastrophic natural disasters. The character can also be used more broadly to suggest something vast or immense in scale.
On'yomi
こう

Used in vocab