Flash flooding on the West Coast on Monday morning put about 80% of some farms underwater.
At its worst, the Ahaura River reached a record 8.7 metres and the Waipuna hit its highest level since 1977.
Helicopters were used in the Grey Valley to herd hundreds of cattle to safety, fencing was damaged, crops lost and dairy sheds flooded.
Farmer Debbie Bland told Morning Report it was the worst flooding she has seen in more than 20 years.
Mrs Bland said she saw power lines down in the Grey River, water lapping at a dozen houses and paddocks covered in silt.
Waipuna Station owner Ken Ferguson said the flooding there was the worst he has seen in some 50 years.
However, he managed to shift most of his sheep, beef cattle and deer to safety as the waters rose.
