Source: Radio New Zealand
Some residents were warned to prepare for possible flooding. RNZ / Nathan Mckinnon
Residents in Banks Peninsula are waking after heavy rain overnight, with up to 100 millimetres predicted to fall between Monday evening and Tuesday mid-morning, and flooding expected in some areas.
Christchurch mayor Phil Mauger warned people not to travel unless they had to.
“It might be a lot of rain, but it’s not for a long time, so we’re keeping an eye on it and hoping for the best.
“Keep an eye out for slips and water running off hills where it doesn’t normally run off a hill and report it, because that’s where slips and dropouts will start to occur.”
He said council staff had spent Monday checking sumps, stormwater outfalls and clearing culverts.
“I don’t mind if a road floods for a very short time, but I don’t want water into people’s houses, that’s not a good look.”
He said Civil Defence teams were ready to mobilise “at the drop of a hat” if needed.
Last May, Little River, about 30 kilometres south of Christchurch, was cut off after State Highway 75 through the town was inundated by half a metre of water.
Residents of the Banks Peninsula town were angry and frustrated and said opening the nearby Lake Forsyth to the ocean would have mitigated flooding in the area.
Mauger said Lake Forsyth / Te Roto o Wairewa had been closely monitored over recent days as water levels had risen and concerns but the weather conditions were too rough for it to be opened to the sea successfully.
Consent conditions determined when the lake could be opened. It had to reach a minimum level of 2.3 metres in summer, and could only be opened early if forecasts show it may rise above 2.7m.
Previous forecasts did not show the lake reaching that threshold, so it could not be opened and sea conditions in recent days had made an opening impossible.
“I think the council’s done all it can do at the moment, it’s cleared as many drains as it can and the culverts under the road, especially by Little River, to get the water into Lake Forsyth.”
Council staff were watching the conditions closely and expected to open the lake later this week, potentially on Wednesday, once conditions allowed.
Given the amount of rain forecast, Little River residents were warned to prepare for possible flooding, and other parts of Banks Peninsula to be aware of the potential for slips and road disruptions.
Mauger said the council had been working on a longer term solution to address flooding at Lake Forsyth and Birdlings Flat, with large pipes currently installed that could be mechanically opened to drain water to the sea when needed.
Christchurch City Council general manager of city infrastructure Brent Smith said teams had done preparation work in the areas expected to feel the greatest impact.
“We’re taking our usual precautions by ensuring beach outfalls and wet weather grilles are clear. Pumps and personnel are on standby for the Flockton area and the most critical location in Southshore. The upper Heathcote flood storage basins will be functioning as they should during this event, so people may notice fluctuating water levels in the river,” Smith said.
“Take care and drive to the conditions, do not drive in any floodwaters. If you do need to travel through pooled water, please drive slowly and carefully, and treat all floodwater as contaminated.”
Staff were also monitoring sensors in place on Lighthouse Road and the surrounding area for any land movement, with several homes in the area evacuated during heavy rain last May.
Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
