氾濫

1. Origins, structure, and basic meaning

• Structure: 氾濫 is read はんらん and means water overflowing from a river or similar body and spreading into the surrounding area.
• Basic usage: It is used to explain river flooding or consequences such as a road being cut off.

2. Common pitfalls and similar expressions

• Rising water and overflow
  • Rising water and overflowing are different. 川が氾濫する means the river overflows, not merely that its water level rises.
• による for cause
  • In 長雨による氾濫, による connects the flooding to its cause: prolonged rain.