Flooding at MercerOn this page:

Many New Zealand towns are built on or near a river crossing, stream or waterway, and danger from flooding is common. Stopbanks constructed to keep out floodwaters often have a limit that can be exceeded during heavy or unusual storm events.

Pre-flood precautions

  • Know the Civil Defence warning signal for your area.
  • Know where to get help - know where your nearest Civil Defence post or Police Station is.
  • Know how to reach the nearest high ground.
  • Know how to turn off electricity and gas supplies at the mains.
  • Find out about the worst flood in your locality and how high it rose.
  • Calculate where such a flood would reach to in your home.
  • If possible, keep your valuables, some clothing and food above this high-water mark.
  • Store weedkillers, insect killers and other chemicals in a high safe place above your estimated high-water mark if possible. In a flood, they can cause contamination, possibly poisonous fumes, that will endanger both your family and rescue volunteers.
  • If you have unused space above your ceiling, consider building some inexpensive storage there, for survival needs, with easy access when a flood threatens. High cupboards are a good alternative.
  • Keep a survival kit always ready.
  • Prepare a getaway bag for each member of your household, including pets. Include important documents in this bag.
  • Keep the insurance cover on your home and its contents up-to-date.

When a flood threatens

  • Listen to your radio for information.
  • Follow official civil defence advice and instructions.
  • When floodwaters get close to your home, disconnect electrical appliances and move valuables, clothing, food, medicines and chemicals above the likely reach of floodwater, if possible.
  • If you have to leave your home, take your getaway kit with you.
  • Turn electricity and gas off at the mains.

During a flood

  • Get to the nearest high ground if possible.
  • Do not go into floodwaters alone.
  • Do not go sightseeing through flooded areas.
  • Do not drink floodwater, it could be contaminated and bad for your health.

After a flood

  • It may take time to get everything back to normal after an emergency.Contact your doctor if you are unwell.
  • Let your local council know of any conditions that could be dangerous or could encourage the spread of diseases.

Salvaging food items and utensils

Floodwaters can carry bugs that cause disease from the ground surface, septic tanks and sewerage systems. These can contaminate food.

  • Wash cooking, eating, and other kitchen utensils in hot soapy water, if they have been covered by floodwater. Rinse thoroughly in safe water, then disinfect by immersing for one minute in a solution of 500 ml (about two cups) of household bleach in 10 litres of water. Rinse again in safe water. Alternatively, boil all utensils for three minutes.
  • Destroy all unpackaged food and food items packed in paper, cardboard or non-waterproof material that have been exposed directly to the floodwater.
  • Get rid of all foods needing refrigeration when they have been unrefrigerated for more than two hours. If the power has been off to the freezer for more than two days, get rid of all thawed food.
  • You can save foods in waterproof, airtight containers (e.g. tins) that have been in floodwater, but make sure they are thoroughly cleaned before opening. Wash and scrub them in warm water with soap or detergent, then rinse them in clean water from a safe supply. Alternatively, soak them for at least one minute in a solution of 500 ml (two cups) of household bleach mixed with 10 litres of water, then rinse clean.
  • Wash and disinfect your can opener before using it.
  • Throw out the contents of bottles with crown tops and crimped or screw caps if they have been submerged in floodwater. It is safer to get rid of all home preserves, as these have a higher risk of contamination than commercial items.
  • DO NOT use packaged or canned food if it has been punctured, is bulging, leaking or the top has popped up. Throw out any canned foods dented on the side or along the top or bottom seams.
  • Cook all food thoroughly and eat it immediately. Cook only enough for each meal. Do not save leftovers.


  • Boil water before drinking.
  • If your water tank is affected by floodwater, get rid of the contents because it may be polluted, clean the tank out and disinfect it.
  • If you use bore water, pump the bore to waste for 24 hours. If the bore is under water do not pump.
  • If your water comes from a well, mix 2.5 litres of household bleach with 45 litres of water and pour down the well. Replace the well cover and turn on each tap until there is a smell of chlorine in the water. Turn off the tap, but do not use the water for eight hours, then open all taps and flush out the chlorine.