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Last reviewed: Mon, 28 Apr 2014

Flooding



Floods are New Zealand’s number one hazard in terms of frequency, losses and declared civil defence emergencies. Floods can cause injury and loss of life, damage to property and infrastructure, loss of stock, and contamination of water and land.

Floods are usually caused by continuous heavy rain or thunderstorms but can also result from tsunami and coastal storm inundation. A flood becomes dangerous if:

  • the water is very deep or travelling very fast
  • the floods have risen very quickly
  • the floodwater contains debris, such as trees and sheets of corrugated iron     

Getting ready before a flood strikes will help reduce damage to your home and business and help you survive.

Before a flood

  • Find out from council if your home or business is at risk from flooding. Ask about evacuation plans and local public alerting systems; how you can reduce the risk of future flooding to your home or business; and what to do with your pets and livestock if you have to evacuate.
  • Know where the closest high ground is and how to get there.
  • Develop a Household Emergency Plan. Assemble and maintain your Emergency Survival Items for your home as well as a portable getaway kit.
  • Check your insurance policy to ensure you have sufficient cover.

During a flood or if a flood is imminent

  • Listen to local radio stations as emergency management officials will be broadcasting the most appropriate advice for your community and situation.
  • If you have a disability or need support, make contact with your support network.
  • Put your household emergency plan into action and check your getaway kit. Be prepared to evacuate quickly if it becomes necessary.
  • Where possible, move pets inside or to a safe place, and move stock to higher ground.
  • Consider using sandbags to keep water away from your home.
  • Lift valuable household items and chemicals as high above the floor as possible.
  • Fill bathtubs, sinks and storage containers with clean water in case water becomes contaminated.
  • Turn off utilities if told to do so by authorities as it can help prevent damage to your home or community. Unplug small appliances to avoid damage from power surges.
  • Do not attempt to drive or walk through floodwaters unless it is absolutely essential.

After a flood

  • It may not be safe to return home even when the floodwaters have receded. Continue to listen to your local radio station for civil defence instructions.
  • Help others if you can, especially people who may require special assistance.
  • Throw away food including canned goods and water that has been contaminated by floodwater.
  • Avoid drinking or preparing food with tap water until you are certain it is not contaminated. If in doubt, check with your local council or public health authority.
  • Look for and report broken utility lines to appropriate authorities.
  • If your property is damaged, take notes and photographs for insurance purposes. If you rent your property, contact your landlord and your contents insurance company as soon as possible.

How to fill and place sand bags

Sandbags are useful to protect your property from some types of flooding:

  • across doorways for houses on a concrete pad
  • across a garage door
  • to divert water down hill

However they can’t stop water coming from under the house and through the floorboards or other access points.

1.     Making sandbags
Make them out of feed bags, hessian bags or plastic (polypropylene) sacks. If you have only the plastic open weave type bag, put one inside the other. Don’t use kitchen rubbish bags as they will slip around in the water and may split.

2.     Filling sandbags
Fill them with a heavy or sandy soil or with sand. Don’t use gravelly or rocky soils as they will let the water through. It’s easiest if there are two people to fill the bags.  One holds the bag and the other shovels the soil or sand in. Only fill it half to two thirds full. This gives the soil or sand room to expand as it holds the water.  Don’t tie or seal the bag – when you put it in place, fold the flap into a triangle and tuck it under the bag.

Sandbag flow

3.     Building the sandbag wall
Place your sandbags lengthwise and parallel to the water flow with the tucked end facing the flow. If you need more than one row’s height, place the second row crosswise, and the third row lengthwise to strengthen the wall.

4.     Drying sandbags for re-use
When the water has receded, separate your sandbags, lay them out or stand them up and let them dry out thoroughly. When they are dry, store them for use again. If you leave them wet, they will rot or deteriorate quickly.

5.    Disposing of sandbags
To dispose of sandbags scatter the sand in your garden. Please do not leave on the kerbside as this may clog up the drains.

Sandbags are available from: Textile Bag and Sack Company: 55 Byron Street, Sydenham. Ph 961 3535

Sand is available from any garden centre.

Canterbury District Health Board FAQs

Read the Frequently Asked Questions provided by the Canterbury District Health Board (CDHB). [PDF, 34.8 KB] 

Authorising Unit: Civil Defence and Emergency Management

Last reviewed: Monday, 28 April 2014

Next review: Tuesday, 28 October 2014

Keywords: civil civil defence emergency volunteers volunteer, civil defence, emergencies, emergency, emergency services, flood, flood control, flooded, flooding, floods