Floods and storms are the most frequent hazard in Hawke’s Bay. Many major damage causing floods have been recorded in Hawke’s Bay, and stopbanks, pumping stations and other protection measures have been put in place. Find out what you need to know, how to prepare, what to do when it happens and also what to do after the event.
Usually there will be sufficient warning of a storm. Keep up to date with daily weather forecasts online (websites and apps ) or through radio and television. You can sign up to receive MetService Severe Weather Warnings and Watches as they are issued – the MetService has good information on the services it provides.
However sudden storms and flash flooding can occur without warning in individual catchments.
Learn more at Get Thru.
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Floods may be listed as Hawke’s Bay’s number five hazard, but it is our most frequent hazard in terms of losses and declared civil defence emergencies.
Much of the built-up and farmed areas of Hawke’s Bay are on low-lying land and river flood plains. This means there is a risk of flooding.
A severe storm or flood happens every 10 years on average.
Major storms affect wide areas and can be accompanied by strong winds, heavy rain or snowfall, thunder, lightning, and rough seas. They can cause damage to property and infrastructure, affect crops and livestock, disrupt essential services and cause coastal inundation.
Rivers normally flood every winter when a storm brings more rainwater than can soak into the soil. In Hawke's Bay, stopbanks have been built alongside many of the rivers to hold in the extra flood water. However in a severe storm, rivers could breach stopbanks and the flood waters may go through farms, homes, shops, schools and damage roads and other infrastructure.
Examination of the rainfall and flood records shows that there have been long periods without major floods and other periods where they have been more frequent.
The common factors in most flood events in Hawke’s Bay are:
Almost immediately after the 1886 flood which flooded most of Meeanne, Hastings and parts of Napier and changes the course of the Ngaruroro River, local people started to demand stopbank protection for their land, property and families.
Hawke’s Bay people and property are now protected from flooding by a significant network of stopbanks and protection systems on both the Heretaunga Plains and the Ruataniwha Plains.
These flood protection works are designed to contain a 1% annual exceedance probability flood – which is the same as saying a flood with a 1 in 100 chance of occurring in any one year and a 10% chance of occurring in any 10 year period.
These protection works have significantly reduced the effect of small to medium sized floods on surrounding land and property, but a large flood could still overwhelm the protection systems and have a devastating effect. Such a flood is called a Super Design Flood because it is exceeds the water capacity that the flood protection system has been designed to.
Flooding from localised downpours in urban areas can also overwhelm drainage systems, especially in the cities which are on flat land and rely on pumping for drainage. These local storms/flash floods often aren’t able to be predicted.
With climate change, rainfall patterns in the Hawke’s Bay will change over the next century; winters are predicted to become drier, but overall flood risk is not expected to decrease as single events may be more intense.
By national standards Hawke’s Bay’s rivers are not large with the exception of the Wairoa and Mohaka Rivers. However, many major damage causing floods have been recorded. Individual floods have ranged in size from cyclonic storms that have caused regional flooding to localised downpours that have affected minor catchments or caused drainage systems to overflow.
Since 1867 there have been numerous major storms resulting in severe flooding in Hawke’s Bay (see the Table below [insert from current website]). You can learn more about these events on the NIWA historical weather events database.
Type of Event: Flood
When: 18 October 2004
A thunderstorm dumped several days' worth of rain on Napier in just a few hours. Described as a rain bomb, this deluge was a 1/50 year event. Rain quickly filled drains and then covered roads, which are constructed below the level of properties to act as large drains.
However, the rain was so intense (up to 180mm of rain was recorded in a few hours in the epicentre of Tamatea/Greenmeadows) that water then spilled over into numerous properties. Eight homes were flooded as well as businesses in the Onekawa industrial area. Losses were estimated in the millions of dollars.
Council Services staff, the Fire Service and Police closed a number of roads to minimise the impact of vehicle bow wave action. Many roads and properties in Napier's southern suburbs were flooded including in Taradale, Tamatea, Pirimai, Greenmeadows and the more rural area of Meeanee.
Fortunately, because of the design of Napier's road profile, very few homes were affected by floodwater.
The Fire Service mobilised the Salvation Army to cater for emergency workers at the Napier Fire Station. The Salvation Army catered for over 60 staff and 10 displaced people.
The Salvation Army Centre in Greenmeadows was offered as a refuge for those who needed it, and some 12 residents from that area visited the centre.
Police and the Fire Service assisted a number of stranded motorists to get to higher ground.
All the agencies involved in the response coped well and additional assistance was not required, so the threshold for declaring a state of emergency was not met.
Access was limited to some schools, including Tamatea Intermediate. Student safety and the risk of power failure were also considered in not reopening a number of schools on 19 October.
The Maraekakaho community was flooded in July 2007. A few houses were evacuated, while others were accessible only to residents.
Type of Event: Cyclone
When: 7 March, 1988
Where: East Coast, North Island
One of the most damaging cyclones to hit New Zealand, Cyclone Bola struck Hawke's Bay and the Gisborne/East Cape region in March 1988. Slowing as it moved over the area, it resulted in continuous torrential rain for three days.
|Formed||February 24, 1988|
|Dissipated||March 4, 1988|
|Highest Winds||165 km/h (105 mph) (10-minute sustained)
195 km/h (120 mph) (1-minute sustained)
|Lowest Pressure||940 hPa (mbar)|
|Damage||$87 million (1988 USD)|
|Areas Affected||Fiji, Vanuatu, New Zealand|
The Heretaunga Plains in flood in 1935 before stopbanks had been built by the Hawke’s Bay Rivers Board and Hawke’s Bay Catchment Board. This photograph highlights how horticultural land would regularly be flooded if we weren’t protected by stopbanks.
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