Beginning on Friday, 27 January 2023, regions across the upper North Island of New Zealand experienced widespread catastrophic floods caused by heavy rainfall, with Auckland being the most significantly affected as the Auckland Anniversary holiday weekend began.
Severe flash flooding occurred across Auckland from around 5:00pm on 27 January local time, after heavy rain in the afternoon. Flooding was widespread across the city, with West Auckland and the North Shore being the worst affected areas. The National Institute of Water and Atmospheric Research reported that an entire summer's worth of rain fell within one day in what it described as a 1-in-200-year event. The event is considered to be the worst flooding in Auckland's modern history. Over the following days other areas of the upper North Island were impacted.
Minister of Finance Grant Robertson stated at the time that the event was New Zealand's costliest non-earthquake event ever, although this record was broken only two weeks later when Cyclone Gabrielle impacted the country.
Background In January 2023, Auckland and the upper North Island experienced relentless maritime heatwave conditions caused by the annual La Niña cycle and exacerbated by climate change. Heavy rain plagued the northern and eastern areas of the country through most of January, with flooding events shortly after New Year, and Tropical Depression Hale impacting the country on 10 and 11 January. Before the events of 27 January, there was already sentiment brewing among some in the country that the summer of 2022–23 was the country's "worst summer ever".
According to Victoria University of Wellington climate scientist James Renwick and University of Auckland urban planning lecturer Timothy Welch, Auckland, along with many other areas in the country, experiences ageing stormwater infrastructure systems which are unable to cope with population growth and the impact of climate change. Tar seals and concrete surfaces on roads, carparks, and buildings also prevent rainwater from dispersing into the ground, causing water to pool up and surfaces to flood during heavy rain events. Significant flooding events had previously occurred in Auckland in August 2021 and March 2022.
Timeline
Late January From 27 January, a tropical atmospheric river carrying a long band of rain and thunderstorms lay mostly stationary over the upper North Island, blocked by a large anticyclone to the southeast of the country which prevented it from moving south across New Zealand. This atmospheric river was brought down into the New Zealand area by the remnant low left behind by Tropical Depression 06F, which moved south into the Tasman Sea.
According to the National Institute of Water and Atmospheric Research (NIWA), Auckland Airport received more than its average monthly rainfall for January () within one day on 27 January. By 10:00 pm on 27 January, other locations in Auckland had reported record daily rainfalls before the day was over; the Museum of Transport and Technology (MOTAT) had had , Albany had had , and Māngere had had . The highest daily rainfall occurred in Māngere, with a total of . Metservice also reported that of rain fell at Albert Park in a span of 34 hours. The peak 2-minute rainfall in Māngere was . Some parts of the city had over of rain within a week. 27 January was declared the wettest day in Auckland on record, with of rain at Auckland Airport exceeding the previous record of . January 2023 was declared the wettest month ever in central Auckland by NIWA, with the total of surpassing the recorded in February 1869.
Some flooding also occurred in the Northland region on 27 January. On 28 and 29 January, the rain spread south of Auckland, causing widespread flooding in the Waikato and Bay of Plenty regions, with some flooding in the Gisborne region. On 31 January, NIWA forecast that the atmospheric river moving through the upper North Island would once again reach Auckland between midnight and dawn. NIWA also reported that a subtropical low-pressure system was predicted to hit Northland that afternoon.
Early February Following lighter rain on 30 and 31 January, areas of Auckland flooded for a second time on the morning of 1 February after more heavy downpours. MetService reported that about of "intensive rainfall" had fallen in parts of Auckland in the early hours of 1 February. Auckland Emergency Management reported there were landslides and flooding in Devonport. Flooding was reported in several areas including Sandringham, St Lukes, near Eden Park, Onehunga, and Wairau Valley. Whangarei Airport in Northland reported of rain between 9:00 pm on 31 January and 4:00 am on 1 February, with half that amount falling around 9:00 pm.
After the heaviest rains subsided, the risk of landslides in Auckland and across other areas of the North Island persisted due to the extreme amount of water in the soil. Even light rains presented the threat of further slips.
On Saturday 4 February, no rain fell at Auckland Airport for the first time since the floods began.
Other events While the North Island was being impacted by extreme weather, MetService confirmed that the humid tropical air that had been brought into the New Zealand area also caused some severe weather in the South Island. Severe thunderstorms impacted some areas of Otago and Southland, while the eastern South Island including parts of coastal Canterbury, Otago, and Southland experienced heatwave conditions at the beginning of February. Heavy rain along the western coast of the South Island caused some slips and minor flooding in the West Coast and Tasman regions, closing a portion of SH 6 on Sunday 5 February, while a small tornado hit Greymouth just after midnight on Monday 6 February.
On 28 January, the Interislander ferry Kaitaki lost power while sailing between Picton and Wellington in Cook Strait at around 5:00 pm. The ship drifted towards Sinclair Head in rough seas churned up by the weather system impacting the North Island. The crew managed to restore some power and made it to Wellington at around 9:00 pm with the assistance of tugboats. The power outage was determined to not have been caused by the weather.
Cyclone Gabrielle brought further severe weather to the North Island from Sunday 12 February to Thursday 16 February, killing 11 people.
The upper North Island, particularly Auckland, experienced another significant flooding event a few months later on Tuesday 9 May, resulting in one death.
Preparations The events of Friday 27 January were largely unexpected, with only orange rain warnings having been issued before the beginning of the event. On the evening of 27 January MetService upgraded the orange rain warning in Auckland to a red rain warning, the highest level of warning available, while the city was already flooding.
In anticipation for more heavy rain arriving on Tuesday 31 January and Wednesday 1 February, MetService issued red rain warnings again for Northland, northern Auckland, Coromandel, and parts of the Bay of Plenty, while an orange rain warning was issued for southern and central Auckland. St John bolstered resources across the upper North Island, supermarkets closed their doors early, and residents raced to clean up debris from the first flooding event in preparation for the possible second flooding event. A state of regional emergency was declared in Northland on 31 January in anticipation of the event, which was rescinded the following day after the event turned out to not be as bad as anticipated in the region.
While no phone alerts were issued during the initial events on Friday, on Sunday 29 January, at 7:47pm, Auckland Emergency Management issued an emergency alert across Auckland via the cellular phone network, warning of possible heavy rain and thunderstorms over the following 12-hour period. Another alert was issued at 3:32 pm on Tuesday 31 January, warning of more rain north of Orewa over Tuesday and Wednesday.
Impact The flooding in Auckland on 27 January affected 25 suburbs in the city, closed major motorways, and left 6,000 to 8,000 homes in need of damage assessment. Multiple slips threatened or destroyed buildings across the city, including a Manukau Coastguard building at French Bay / Otitori Bay. On 28 January shortly before midnight, a landslide in Tauranga destroyed a house. As of 12:00 pm on Wednesday 8 February, 277 red placards, 1,615 yellow placards, and 2,566 white placards had been issued on buildings across Auckland. As of Monday 27 February, there were 357 houses with red placards and 943 houses with yellow placards. A red placard indicates the building is unsafe to enter, a yellow placard indicates the building has restricted access, and a white placard indicates minimal damage.
Emergency services in Auckland responded to 719 weather incidents, answered 2,242 emergency calls, and made 126 rescues on Friday and Saturday morning. A total of 811 water damaged cars had to be manually removed from roads, while 20 water damaged buses were removed from service. Mayor of Auckland Wayne Brown stated that over 200 lifts were reported to not be working across the city after the floods, potentially isolating elderly residents at the top of apartment buildings, but Age Concern Auckland CEO Kevin Lamb stated that they had not had any calls about elderly people experiencing difficulties because of lift outages.
A second event in Auckland on 1 February resulted in several homes, businesses, and roads being inundated by flooding, with major slips being reported. 44 families with 168 members were placed into emergency accommodation after this event, while Fire and Emergency New Zealand responded to 63 incidents, including rescues. In total, 1313 injury claims were made to ACC in relation to the floods.
The New Zealand Insurance Council predicted that the event will result in the highest number of weather related insurance claims on record, with insurance companies expecting that this will be the costliest weather event in New Zealand ever. AA Insurance stated that the floods were its largest vehicle claims event in history, with an estimated 10,000 cars expected to be written off. Perils estimated the insurance loss was about NZ$2.2 billion (US$1.43 billion). The previous costliest weather event in New Zealand history for insurance claims was a hailstorm in Timaru in 2019 that caused NZ$171 million of insurance damage. The event also surpassed the total cost of NZ$351 million of weather-related insurance claims in New Zealand during the entirety of 2022, which was previously the highest number in a year ever. Auckland mayor Wayne Brown estimated the cost to recover from the event is about NZ$4 billion (US$2.6 billion).
Deaths and evacuations Four people died on 27 January; two drowned in Wairau Valley on the North Shore, one was killed by a slip in Remuera, and one drowned in the Waikato town of Onewhero, with thousands forced to evacuate their homes. Two children were reported missing in Auckland during the night of Saturday 28 January, and were later found with a woman.
It was expected that hundreds of pets and livestock would need medical care after the Auckland floods. Countless numbers of animals were lost and died in the floods.
On Saturday 28 January, severe flooding in the Waitomo District of the Waikato region resulted in many evacuations, particularly around the town of Te Kūiti.
More people had to be evacuated during the second flooding event in Auckland on Wednesday 1 February.
Infrastructure damage
Roading network By 11:36pm on Friday 27 January, the NZ Transport Agency announced multiple state highway closures in the Auckland region due to slips, flooding, tree clearing, and storm damage, among other damage on local roads and streets controlled by Auckland Transport. State highway closures included:
SH1 Brynderwyn SH12 multiple locations SH1 Dome Valley SH1 Puhoi SH16 between Kumeū and Wellsford