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“Mùa mưa, lũ đã gây thiệt hại nặng nề cho nông dân.”
During the rainy season, the flood caused severe damage to the farmers.
A large amount of water covering normally dry land, often causing damage.
Lũ lụt đã làm ngập hết các cánh đồng.
The flood inundated all the fields.
Usually paired with classifiers like "cơn" (e.g., "cơn lũ").