what does 'they are expecting high water' mean?

Question

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Answer 1

Definition of high water
1. Same as high tide (sense 1) (sense 2)
2. highest water level: the highest level reached by any stretch of water, e.g. during a flood (hyphenated before a noun)
3. time of highest water: the time when the water level of a river or other stretch of water is at its highest

Answer 2

*Simple easy meaning is Flood.*