Flood waters can destroy the land, washing away roads, bridges, railway tracks and buildings. Crops can be ruined and livestock drowned. Lives are also at risk, particularly in flash floods.

Floods are one of 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.

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 to be carried by the rivers.

There are four main types of flood:

  • Rising rivers happen during heavy rain, when rivers can overflow their banks into the floodplain. A floodplain is the 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 tsunami.
  • Urban areas have a lot of concrete or hard surfaces, which stop rainwater from soaking into the soil, so it is channelled into storm water drains. When the rain falls faster than the storm water 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 and wash away or damage roads, bridges, railway tracks and buildings. Crops can be flooded and livestock drowned. People have to take care and be prepared, particularly in flash floods where fast-flowing water filled with debris can sweep people away. The waters can even be strong enough to pick up vehicles.

After a major flood there will be a lot of damage and pollution to clean up. It may take months or years to recover.

What do we do before a flood?

  • Know how to reach the nearest high ground.
  • Move animals to safety.
  • Keep valuables and some food and water above the high water mark. Attics or upstairs rooms are good places for storage, as long as there is easy access.
  • Remind adults to store chemicals in a high, safe place. If a flood occurs and these chemicals leak, they could be dangerous.

What do we do during a flood?

  • Listen to the radio for weather reports, advice and instructions.
  • Do not try to walk or drive through flood water.
  • Take your grab bag with you if you have to leave your home.
  • Remind adults to turn off water, electricity and gas.

What do we do after a flood?

  • Only return home once you are told it is safe to do so.

  • Don't go sightseeing through flooded areas.

  • Do not drink floodwater. It could be contaminated.

Find out more about what to do before, during and after a flood.

Home learning

Are you ready in case a flood occurs?

Find out about the worst flood in your area and how high the flood waters reached. Record this height and share it with your family — would it reach your home? 

Make a plan with your family to get through an emergency. Think about the things you need every day and work out what you would do if you didn't have them. 

Make your plan — print it out, stick it on the fridge and make sure everyone knows the plan. 

Find out about past floods that have happened in your region.

Digital resources

National Geographic logo

Floods 101 is part of a series of natural disaster videos produced by National Geographic.

A map of a local area allows the user to adjust floodwaters to show how much of the land could end up under sea level.

Stemworks logo

STEM-Works have a series of learning experiences that focus on floods and tsunami.

Te Ara logo

A New Zealand perspective on floods from Te Ara, the Encyclopedia of New Zealand.

Learn about emergencies

Earthquakes, floods, landslides, storms, tsunami and volcanic activity can be frightening because they can strike at any time and often without warning. Explore the types of emergencies below and learn better ways to prepare.