The Otago Regional Council is proposing to build a single bund about 800m long and up to 1.5m high along with swale and a 1m high box culvert beneath Riccarton Rd, to give 15 properties around Riccarton Rd, Dukes Rd and Gordon Rd, "some degree of" protection.
Flood risk in the area north of the Silver Stream, between the three roads, was highlighted following an April 2006 event which flooded 80 rural and residential properties and smaller floods in July 2007 and May 2010.
In 2010, a concept for low bunds in the area was investigated, but reworked to "minimise cost while maximising effectiveness", after suggestions to widen the Silver Stream to contain similar floods was deemed too expensive at an excess of $5 million.
Provision for the work had been included in the council's long-term plan, but how the works would be funded still needed to be developed and public consultation undertaken before the council decided to do the work.
Typically, flood protection works are funded by those who benefit from them.
Environmental engineering and natural hazards director Gavin Palmer said the works would give residents more time to respond in a flood situation and contain smaller "nuisance" events such as in 2007 and 2010 but otherwise the benefit was "pretty limited".
"It's up to the community whether spending the money is worth it."
Cr Gretchen Robertson said spending $430,000 to give 15 properties some degree of flood protection was a "lot of money".
"It's something the council and the community will have to ponder long and hard."
Chairman Stephen Woodhead said staff had talked to the affected property owners last week, outlining the proposal and suggesting they needed to make their opinions known through the annual plan submission process.
"Let us see what the feedback says, pull together the numbers and take it to the community."
A rough indication of the likely costs was needed before the council or community could go much further, he said.
"They might decide they'd be prepared to live with the risk rather, as the cost of covering some risk is just too high."
Dr Palmer said it would be a delicate balance to ensure the proposed works did not exacerbate flooding problems elsewhere, but it was thought the work would produce some wider benefits to other areas by reducing the flow.
While the work was provided for in the draft long-term plan, as no consultation or consents had been granted it was likely the work would have to be deferred for a year to allow for that to happen, he said.
