Inundação vs. cheia vs. enchente vs. dilúvio
While inundação, cheia, enchente, and dilúvio all relate to excess water, their usage depends heavily on regional preference (Brazil vs. Portugal) and the specific nature of the event. Inundação is technical, dilúvio is about rain intensity, while cheia and enchente are the most common everyday terms with distinct regional leanings.
Inundação
B2This is the most formal and technical term, used in both Brazil and Portugal. Inundação specifically refers to the effect of water covering land that is normally dry, such as a basement, a street, or a field. It often implies property damage.
A inundação destruiu as plantações de arroz.
(The flood destroyed the rice crops.)
O sistema de drenagem falhou e houve uma inundação no centro da cidade.
(The drainage system failed and there was a flood in the city center.)
O seguro da casa não cobre danos por inundação.
(The home insurance does not cover flood damage.)
Cheia
B1In Portugal, cheia is the standard terminology for a river overflowing its banks; it is the most common word for flood. In Brazil, cheia is often used to describe the natural hydrological cycle of high water (seasonality) rather than just a disaster, though it can still mean an overflow.
Em Portugal, as notícias alertaram para a cheia do rio Douro.
(In Portugal, the news warned about the flooding of the Douro River.)
Na Amazônia, a época da cheia é boa para a navegação.
(In the Amazon, the high water season is good for navigation.)
A população ribeirinha já está acostumada com as cheias anuais.
(The riverside population is already used to the annual river rises.)
Enchente
B1In Brazil, enchente is the most common everyday word for a flood, especially flash floods in cities caused by heavy rain. In Portugal, it is used less frequently for disasters and refers more generally to the action of rising water or tides.
A tempestade de verão causou uma grande enchente em São Paulo.
(The summer storm caused a major flood in São Paulo.)
Os carros ficaram parados por causa da enchente na rodovia.
(The cars were stopped because of the flooding on the highway.)
Sempre que chove forte, os moradores temem uma nova enchente.
(Whenever it rains hard, residents fear a new flood.)
Dilúvio
C1This word corresponds to deluge. It is used in both countries to describe extremely heavy, torrential rain. It is often hyperbolic or biblical (referring to Noah's Ark) and focuses on the falling rain rather than the standing water on the ground.
Está caindo um dilúvio lá fora, é melhor não sair agora.
(A deluge is coming down outside, it is better not to leave now.)
Segundo a Bíblia, Noé construiu a arca para sobreviver ao dilúvio.
(According to the Bible, Noah built the ark to survive the flood.)
Depois desse dilúvio, as ruas certamente ficarão alagadas.
(After this downpour, the streets will certainly be flooded.)
Summary
Use inundação for formal contexts regarding submerged land. Use cheia if you are in Portugal (general flood) or describing seasonal river cycles in Brazil. Use enchente if you are in Brazil describing urban flooding. Use dilúvio when emphasizing the intensity of the rain itself.