Upgrade works on the Kowhai Park stopbanks in Wanganui are set to begin next week.

Horizons Regional councillors agreed to the $1 million works about a year ago after it was found there was significant variation in the standard of protection these provided.

New Plymouth-based Whitaker Civil Engineering has been awarded the contract for the major part of the upgrade, which will comprise raising earth stopbanks, constructing timber retaining walls and concrete floodwalls and modifying roadways within Kowhai Park.

Horizons group manager operations Allan Cook says the works will result in a consistent standard so that a 50-year flood can be contained.

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"The present low standard of protection was demonstrated in October last year when a 23-year return period flood was only just contained with hastily-erected sandbag walls. Since then, temporary measures have been in place aiding prevention of a stopbank breach," Mr Cook said.

"For safety reasons, it will be necessary to close off public access to sections of the park as works progress. Some disruption for the public is unavoidable. However we will do our best to minimise that and, wherever possible, will provide alternative passageways around the works site."

The works are expected to be substantially completed within 12 weeks. The estimated cost of the overall flood protection upgrade project, including works in the Matarawa Stream immediately above Anzac Parade, for which tenders are yet to be called, is $1,020,000.

The works will be undertaken within three separate zones, with works to be substantially completed in each before the next begins.

The first zone comprises the arboretum extending from Georgetti Rd to the Matarawa Stream. Works activity will then shift to the area between Dublin St and Helmore St, while the final zone comprises the area adjoining the children's playground.