What is a flood?

Floods are one of Aotearoa New Zealand’s most frequent emergency events. They happen when storms and heavy rain make rivers overflow their banks or drainage systems overflow into the streets. About two-thirds of New Zealand's population lives in areas prone to flooding.

Normal rainfall soaks into the soil, is taken up by trees and plants, and runs off the land to form our streams and rivers. Floods happen when there is too much water and the run-off is too much for rivers to carry. There are four main types of floods:

  • Rising rivers happen during heavy rain when rivers can overflow their banks into the floodplain. A floodplain is a flat section next to a river, and these can flood quite regularly.

  • Flash floods happen when heavy rain falls in a small area with little warning.

  • Coastal areas can sometimes flood because of unusually high tides or tsunamis.

  • Urban areas have a lot of concrete or hard surfaces. They stop rainwater from soaking into the soil, so it is channelled into stormwater drains. When the rain falls faster than the stormwater system can manage, we get urban flash flooding. These floods usually happen very quickly and can block roads and damage buildings. Luckily, they usually don’t last very long.

Flood waters can destroy the land. They can wash away or damage roads, bridges, railway tracks and buildings. They can ruin crops and drown livestock. New Zealanders have to take care and prepare, particularly in flash floods where fast-flowing water filled with debris can sweep people away.

After a major flood, there will be a lot of damage and pollution to clean up. It may take months or years to recover. To be flood-safe, action has to be taken at every step pre, during and after a flood event. Here's more about what to do at each phase.


Get ready before a flood:

  • Find out from your local council if your home or business is at risk from flooding and how they’ll alert you if you need to evacuate. Ask about:

    • Evacuation plans and local public alerting systems

    • What to do with your pets and livestock if you have to evacuate

    • How you can reduce the risk of future flooding to your home or business

  • Work out what supplies you might need and make a plan with your whānau.

  • Practise your emergency plan and your evacuation route to higher ground.


Know what to do during a flood:

  • Put safety first. Don’t take any chances. Act quickly if you see rising water.

  • Floods and flash floods can happen quickly. If you see rising water do not wait for official warnings. Head for higher ground and stay away from floodwater.

  • Never try to walk, swim or drive through flood water. Many flood fatalities are caused by people attempting to drive through water.

  • Always assume that flood water is contaminated with farm run-off, chemicals and sewage. Contaminated flood water can make you sick. Make sure you wash your hands, clothes and property after contact with flood waters.

  • If flooding is possible, stay informed. Follow your local Civil Defence Emergency Management Group online. Contact details for major cities at the end of this list.

  • Be prepared to evacuate and keep your grab bag near. Listen to emergency services and local Civil Defence Authorities. Follow instructions about an evacuation in your area - self-evacuate if you’re unsafe

  • Move pets to a safe place and move stock to higher ground. If you have to leave, take your pets with you. If it’s not safe for you, it’s not safe for them

  • Turn off water, electricity and gas if advised to

  • Move valuable and dangerous items as high above the floor as possible. This includes electrical equipment and chemicals. Use watertight containers to store important items

  • Lift curtains, rugs and bedding off the floor

  • Check on your neighbours and anyone who may need your help

Civil defence emergency management groups (CDEMs) are responsible for coordinating and delivering effective emergency management in their regions.


After a flood, stay away from damaged areas. You might hamper rescue and other emergency operations and be at further risk from the residual effects of floods.

  • Only return home after Civil Defence and emergency services have told you it is safe to do so. It may not be safe to return home even when the floodwaters have receded.

  • Look before you step. After a flood, the ground and floors may be slippery or covered with debris, including broken bottles and nails.

  • Help others if you can, especially people who may need extra help.

If your property is damaged:

  • Do not do anything that puts your safety at risk or causes more damage to your property.

  • Contact your insurance company as soon as possible.

  • If you rent your property, contact your landlord and your contents insurance company.

  • Take photos of any damage. It will help speed up assessments of your claims.

Food Safety in floods

Keep your food and water safe.
During an emergency:

  • Fridges, freezers, and ovens may break down, and food could spoil more quickly

  • Water supplies could get cut off or get polluted

  • Sewerage systems could get disrupted

  • To avoid getting sick from food during emergencies:

    • eat foods that will expire soon first – for example, bread and meat because they spoil more quickly than non-perishable food

    • eat canned foods last

    • open the fridge and freezer as little as possible to help keep them cooler for longer

    • do not eat vegetables or fruits that have been lying in floodwater

    • cover all food with plastic wrap, or store it in waterproof containers

    • leave bottles, drink cans, and water containers in the fridge (if it's working) to keep things cold

    • throw out bad or rotting food before it spoils other food.

Focus on hygiene when preparing and cooking food:

  • Maintaining hygiene around food preparation and cooking requires more thought than normal

  • Always wash and dry your hands before preparing food – if water is in short supply, keep some in a bowl with disinfectant

  • Ensure all kitchen utensils are clean before use

  • Cook food thoroughly

  • Cover all food with plastic wrap or store it in waterproof containers

  • Rubbish containing food scraps must be protected from flies and rats by wrapping the scraps or putting them in a sealed container

How to use clean water and keep it safe and clean:

  • To cook, wash dishes, and wash your hands, you can use water from:

    • a hot water cylinder

    • a toilet cistern – as long as no chemical toilet cleaner is present

    • a spa/swimming pool – they can be used to wash yourself and your family

  • You can also use bottled water

Boil or purify water before using it in food preparation. This helps to avoid spreading viruses and bacteria between food. Once boiling, cover and store food in a clean container and place it in the fridge (if it's working) or in some other cool place. Re-boil the water if it is not used within 24 hours.

If you do not have a power supply to boil water, then purifying tablets or bleach can be added to ensure its safety. Add 5 drops of household bleach per litre of water (or half a teaspoon for 10 litres) and leave for 30 minutes. Do not use bleaches that contain added scent or perfume, surfactants, or other additives – they can make people sick.

After an emergency, make sure food is safe:

Knowing what is safe to eat during the "clean-up" phase after an emergency can become a guessing game. Understand what may or may not be safe to eat:

  • Check the food – does it smell or look different? Has the colour changed and does it have a slimy texture? If so, it's probably unsafe to eat

  • If food is still visibly frozen (for example, it still has ice crystals on it), and the packaging isn't damaged or open, you can still safely refreeze it

  • You should not refreeze food that has defrosted

  • You can still keep or use food that was frozen but has defrosted, you just need to keep it cold

  • Do not use any tinned food that has been damaged (e.g. if the can is open, become deeply dented, or is heavily rusted)

You should always be prepared for a disaster. If you follow the guidelines above, they may help prevent you or your family from becoming ill. Food safety is just one step in staying safe during and after an emergency. Your local CDEM has more information on what to do in an emergency.

Prepare a survival kit for next time:

There are many things you can do to minimise the impact on your health before disaster strikes. Put together an emergency food survival kit. Do it now, and make sure you include enough of the following items to last at least 3 days:

  • Canned or dried food – luncheon meat, ham, fish, fruits, vegetables, cereals, tea, coffee, powdered soup, salt, sugar, sweets, biscuits, and a can opener

  • A primus or portable gas cooker or barbecue to cook on

  • Eating equipment – utensils, knives, pots, cups, plates, bowls, matches, lighters

  • Bottled water – 3 litres/day, or 6 to 8 large plastic soft-drink bottles of water per person per day

  • Bottled water – 1 litre for washing food and cooking each meal, washing dishes and washing

  • Milk powder or UHT milk

Storing your survival kit:

  • Regularly restock and refresh your emergency food supplies

  • Consider your family's medical or dietary needs. If you have babies or children, make sure they have enough suitable food

  • Check use-by dates and make sure cans and packaging are not damaged or rusty

  • Throw away any item that is not in good condition

  • If you live in a place that's at risk of flooding, keep your survival kit above where the water might reach

Find out more:

If you have any questions or need extra support, we're here to help you anytime, in any language. Simply start a chat with us via the home screen of the Sonder app.

Information sourced from: MPI NZ, NZ Ministry of Health, and Get Thru.

Image credit: Casey Horner, Unsplash.

All content is created and published for informational purposes only. It is not intended to be a substitute for professional advice. Always seek the guidance of a qualified health professional.

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