Westport flood protection scheme faces extra costs

Westport was completely flooded on July 18, 2021. Photo / George Heard

A proposal to improve drainage of floodwaters around Westport will have further cost implications for the planned flood protection scheme for the town.

A proposal to improve, extend or build new culverts and open up existing drains is detailed in a report by West Coast Regional Council engineering staff, following an investigation into improving drainage.

"Any costs associated with improving the drainage within the rating district will be in addition to the flood protection scheme budget that was consulted on in 2021," the report notes.

Currently the flood protection scheme is expected to cost over $10 million.

The drainage proposal was to be considered by the Westport Rating District Joint Committee today, and follows recommended emergency works by the Westport Technical Advisory Group (TAG) following post-flood damage assessments from the July and February floods.

The report notes that drainage issues had been identified at the consultation phase of the regional council's 2021-31 long-term plan process last year.

The council had subsequently adopted a plan to address the Westport flooding issue via extensive floodwalls and stopbanks.

"Drainage was identified by many submitters ... as a major issue and one that needed to be considered alongside other flood mitigation proposals."

Staff had now inspected the main "arterial" drains and culverts in Westport and reported to the TAG there were options for improving drainage issues.

"This includes cleaning out the existing drains to improve flow, increase the size of culverts, and increase the number of culverts and appurtenances to improve the efficiency of the flood protection structures."

This included 12.8km of existing drains around the town, 34 existing and an estimated 31 potential culverts.

Further investigation was needed on culvert size once the height of the proposed floodbank for the town was confirmed.