Canterbury residents are being urged to watch for rapidly rising streams and rivers, surface flooding and slips after MetService issued a heavy rain warning for the areas tomorrow.
A MetService spokesman said a front was forecast to move slowly southwards over northern and central New Zealand today, bringing a broad band of rain with some heavy falls, and east to northeast gales.
An associated low to the west of the upper North Island would also move slowly southwards, then weaken and cross the South Island on Wednesday.
An orange heavy rain warning has been issued for Canterbury residents south of the Rakaia River. The area should expect periods of heavy rain between 1am Tuesday and 3am Wednesday, with 100 to 130mm expected to accumulate about the foothills, and lesser amounts elsewhere. The rain will peak at about 10 to 15 mm per hour.A heavy rain watch is in place for Canterbury from the Rakaia River north. The area may approach warning criteria between midnight Monday and 6pm Tuesday.
MetService has also issued a number of road snowfall warnings, including for Lewis Pass from 2pm to 9pm tomorrow, Arthur's Pass 3pm to 2am tomorrow, Porter's Pass from 4pm to 1am, Lindis Pass from 8pm to 11pm tomorrow and the Crown Range Rd from 1am to 4pm tomorrow.
Christchurch and Banks Peninsula residents should also prepare for the possibility of more flooding and slips this week.
"This July has been one of the wettest on record and unfortunately there is more rain to come over the next few days," said Christchurch City Council Civil Defence and Emergency Management manger Brenden Winder.
"With the ground already saturated and river levels reasonably high, it is likely we will get surface flooding in parts of the district so people should prepare for that. We may also get some slips in hillside areas.
"The worst of the rain looks like it will hit us on Tuesday and Wednesday. Strong easterly winds are forecast to accompany the rain, which may create issues with estuary and river levels, particularly around high tide on Tuesday afternoon and Wednesday morning.
"Staff and contractors are ready to respond to issues that might arise and our contact centre will be open around-the-clock for residents who need help.
"We will prioritise responding to calls where safety is an issue or where people’s homes and businesses are at threat. If people feel their safety is at risk they should call 111 immediately," Winder says.
He said residents do not need to report flooding on roads to the council unless there is a genuine safety issue. The roads will cope with stormwater ponding on them and the water will drain away once the rain stops.
"Our contractors have been checking key parts of the stormwater network in preparation for this week’s rain and we have released water from the storage basins in the upper Heathcote so that we have capacity to store stormwater during the peak of this weather event," Winder says.
"If you know there are leaves blocking sumps or drains by your property, it would help us if you could remove them, if it is safe to do so, and put them in your green wheelie bin.
"If you live in an area that is prone to flooding, please think about where you park your car. Don’t park it somewhere where it could get caught in flood water.
"Please remember too that if you’re driving on the roads and you come across ponded water that you can’t detour around, proceed slowly so that you don’t push it onto people’s properties.
"If you come into contact with flood water, you should treat it as contaminated and wash your hands thoroughly afterwards," Winder said.
Meanwhile, North Otago could expect up to 130mm of rain to accumulate between 6am tomorrow and 8am on Wednesday, especially inland, with peak rates of up to 15mm per hour.
Dunedin residents could expect up to 90mm of rain between 7am tomorrow and 9am on Wednesday - again, with peak rates of up to 15mm per hour.
"Heavy rain may cause streams and rivers to rise rapidly," the MetService spokesman said.
"Surface flooding and slips are also possible, and driving conditions may be hazardous.
"People are advised to keep up to date with the latest forecasts in case any changes are made, or further areas are added," he said.
The Dunedin City Council has also issued a warning in regard to the rain, and says its contractors are busy preparing and will respond to any issues as they arise.
- John.lewis@odt.co.nz and Star News
