Peter Meecham / Stuff
Flooding around the Heathcote River in Christchurch flooding on Eastern Terrace in the suburb of Beckenham.
July will be the wettest ever for Christchurch, with a severe weather warning for the Garden City likely in the coming days.
The city has already received 157mm of rainfall this month, more than double the monthly average of 61mm. The wettest July ever recorded is 1977 with 180.8mm of rain and Metservice predicts it could topple in 2022.
“It is likely that this total will be surpassed before the month comes to an end because of this next event starting Monday,” a spokesperson said.
After Thursday’s unexpected flooding, Christchurch can expect a dry weekend. However, rain is expected again across the Canterbury region from Monday.
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KAI SCHWORER/Things
The roof of an underwater car can be seen in the Heathcote River at Waimea Terrace in Christchurch. Emergency services checked the vehicle to make sure no one was inside.
“We expect the rain for Christchurch to be quite persistent from Monday to the end of Wednesday.
“This is probably a significant event because of the wet weather you’ve been experiencing there over the past month and the basin being saturated.”
The MetService severe weather team has spoken to Christchurch City Council and is likely to issue a severe weather forecast for the week ahead over the weekend.
The criterion for a rain warning was for widespread rainfall of more than 50mm in six hours or 100mm in 24 hours.
PETER MEECHAM/STUFF
Heavy rainfall has led to flooding around Christchurch’s Heathcote River.
As the roads reopened on Friday, Metservice said there was a good chance of more flooding for the city.
Christchurch received 44mm of rain in the 24 hours to 2 p.m. Thursday. Akaroa received 79mm.
The rain caused the Ōpāwaho/Heathcote and Ōtākaro/Avon rivers to burst their banks in sections, shutting down several roads in low-lying areas for much of the day.
Thursday’s floods surprised a lot of people and some residents were trapped in their homes, while a number of cars were flooded, especially those parked next to the rivers.
A local resident watches the Heathcote River outside his driveway in Christchurch on Tuesday as it flows around homes on Waimea Terrace.
The City Council has spent tens of millions of dollars in the past six years protect low-lying parts of the city from flooding.
Along the Heathcote, the dredged the river to increase capacity, stabilized the banks and the municipality was building four rainwater storage basins in the upper Heathcote catchment at a cost of approximately $96 million.
The basins are designed to store water and release it slowly into the river over time, rather than all the water draining down the river at once. Once completed, these basins would have the capacity to store more than 2 million cubic meters of water.
Two of the three storage basins have been completed, but one of the completed basins – Curletts Rd – has not been operational since February when the council discovered leaks in the concrete structure housing the lock gates.
The water level in the Heathcote was expected to rise again, especially between Lincoln and Cashmere Rds, but it would not cause significant flooding, acting council chair Mary Richardson said.
The Christchurch City Council said it would drain water from the basins in the coming days once the river level has dropped.