Mrs Curtis said yesterday that she changed jobs about eight months ago and, despite the support of her employer, she had found it increasingly difficult to keep up with the demands of being a member of the community board.
"I'm not able to give it everything I had and the time it deserves", which led to her resignation, Mrs Curtis said.
Waitaki electoral officer Debbi Miall said the by-election would be publicly notified and nominations to fill the vacancy called on Thursday.
The electoral roll for the Waihemo ward would also open for inspection.
The by-election will be held in September on a date which will be advertised in the public notification on Thursday.
Under the Local Electoral Act, an extraordinary vacancy more than 12 months before the next local body elections - due to be held in October next year - had to be filled by a by-election.
