外がい水すい氾はん濫らん

noun

river flooding; flooding from rivers overflowing

Technical term used in disaster prevention and hydrology; refers specifically to flooding caused by river water overflowing or breaching levees, as opposed to inland flooding (内水氾濫).

See also: 河川氾濫

• 台たい風ふうによる外がい水すい氾はん濫らんで、堤てい防ぼうが決けっ壊かいした。

  The levee broke due to river flooding caused by the typhoon.

• 外がい水すい氾はん濫らんと内ない水すい氾はん濫らんの違ちがいを説せつ明めいしてください。

  Please explain the difference between river flooding and inland flooding.