River levels are beginning to drop on the West Coast, as heavy rain eases

But authorities aren't relaxing, with one Buller rain gauge recording about 300 millimetres yesterday.

Civil Defence Controller Al Lawn says any more of that kind of rain in the wrong places, could cause issues.

The district's staying in a state of emergency - as well as a voluntary evacuation order in parts of Westport, Seddonville and Mokihinui.

Lawn says their preparation is paying off - with bunds, pumps and sandbags helping mitigate the severest impacts.