Wettest July could bring more flooding
Christchurch could be in for more flooding next week, with rain forecast to return to a city on track for its wettest July on record.
After surprise flooding on Thursday, which Christchurch City Council attributed to getting more rain than forecast, staff are giving residents an early warning to prepare, and say they will be monitoring the already wet ground across the city.
Christchurch received 44mm of rain in the 24 hours to 2pm on Thursday, and Akaroa received 79mm.
The rain caused the Opa¯ ¯ waho/ Heathcote and O¯ ta¯ karo/Avon rivers to break their banks in sections, causing closures on several roads in low-lying areas for much of the day.
MetService said this July was shaping up to be the wettest one on record for Christchurch, with a severe weather warning for the Garden City likely in the days ahead.
The city has already received 157 millimetres of rainfall this month, more than double the monthly average of 61mm. The wettest July on record is 1977 with 180.8mm of rain and MetService predicts this could be toppled in 2022.
‘‘It is likely this total will be surpassed before the month comes to an end due to this next event starting on Monday,’’ a MetService spokesperson said.
Christchurch can expect a dry weekend, but from Monday, rain is expected to return throughout Canterbury.
‘‘We expect the rain to be quite persistent for Christchurch from Monday until the end of Wednesday.
‘‘This is likely to be a significant event due to the wet weather you have been experiencing down there over the last month and the basin being saturated.’’
The criteria for a rain warning was for widespread rainfall greater than 50mm in six hours or 100mm in 24 hours.
Council’s head of Three Waters, Helen Beaumont said advice to residents is to ‘‘clear your own gutters and ensure your cars are parked well away from areas that are vulnerable to flooding’’.
She said the council’s approach would be to mitigate the effects of flooding.
‘‘For these larger events we will proactively clear critical stormwater grilles, check and excavate beach outfalls, deploy pumps to vulnerable locations across the city, let the general public know what to expect, communicate with Civil Defence and make staff available to monitor the event and supervise the response across the city.’’
Beaumont said the basins would reduce peak water levels, but in cases of significant rainfall, rivers could spill out onto streets.
‘‘For moderate events this generally means that we need to close the low-lying roads, often disrupting access to houses and commercial buildings, and many residential properties close to our rivers and streams will see their sections and some garages flooded.’’
On Thursday, the flooding caught many people by surprise and some residents were left stuck inside their homes, while several cars were waterlogged, especially those parked next to the Heathcote River.
Asked why residents weren’t warned about the possibility of flooding, Beaumont said the council relied on weather forecasts from MetService just like the general public did.
Fire crews were called to a fully submerged vehicle in the Heathcote River just after 9.30am yesterday.
Spreydon fire station officer Cory Stewart said when they arrived no-one knew if a person was inside the vehicle.
Two crew members entered the river to check the vehicle but no-one was found inside.
‘‘We don’t know who it belonged to or how it ended up there,’’ Stewart said.