16 Hazards of floodwater

by Feb 27, 2022Preparation



Almost everywhere floods and to prevent injury or death you need to know the hazards of floodwater.  The floodwater can be pooling or fast-flowing in creeks, drains or streets.  You could be at home or in transit.  The dangers are everywhere and most are hidden by the floodwater.

  1.  Contamination by chemicals
  2. Contamination by sewerage
  3. Fast moving current
  4. Floating debris
  5. Deep water
  6. Submerged objects
  7.  Bacteria and viruses
  8. Insect infestation
  9.  Contaminated drinking water
  10. Powerlines
  11. Dead animals
  12.  Contaminated soil and debris
  13.  Panicked animals
  14. Driving through floodwater
  15. Swimming in floodwater
  16. Stress and trauma

 Hazards of floodwaters

 Contamination by chemicals

 As floodwaters run through industrial estates, fuel stations, hardware stores, people’s backyard sheds it picks up chemicals, oils, acids, poisons, herbicides and more.  Some chemicals are water-soluble others float on the surface.

 These chemicals can cause infections, burns, irritations and other personal injuries.


 Contamination by sewerage

 The excess floodwater runs into the sewerage system, which increases the pressure in the system making it spill out through manholes and drainage.   Sewerage contains bacteria, pathogens, diseases, medications and viruses.  This can cause infections of cuts and mucus membranes.   Ingested contaminated water can cause vomiting and diarrhea.


Fast-moving currents

 Fast-moving currents carry objects from upstream.  These items can be hidden in the foaming muddy water.  The currents can – 

  • Sweep your vehicle downstream
  • Knock you off your feet and sweep you downstream
  • Hit you with floating trees and debris
  • Dump debris in the middle of the road and then hides it
  • Washes away the road, culverts and bridges.

 As the currents go over and around objects, they can form whirlpools trapping you or objects.


 Floating debris

 Trees, cars, building materials, rocks, and backyard junk can be dragged along on the surface or under the floodwaters.  If you are walking through the flood water you can be hit by the debris or can fall over it causing cuts and injuries.  You could also be swept downstream when you are knocked over in the current.


 The water may be deeper than you anticipated and you think ‘it will be alright’.  Next thing the water is over your bonnet and the car has stalled.  At this stage, you have a panic digging around in the flooded car for your mobile phone which no longer works.  Rescue won’t be happening soon.


Submerged objects


Floodwaters can be muddy, have a foam top layer or be murky from currents and contamination.  As you drive along you don’t see all the objects under the water that can damage your car or cause an accident.






Emergency Kit


    Bacteria and viruses

     Soil-borne microbes come out of the soil such as Melioidosis [2].  Other disease-causing microbes can come from sewerage, dead animals, garbage, rotting food and similar putrid items. 

     These microbes can enter through cuts, scratches, mucus linings (eyes, nose, mouth, groin) and by breathing them in.  Some microbes are fatal, especially if not caught early enough. 

    Insect infestation

     Stagnant water can breed mosquitoes that can spread dengue fever, Ross River virus, malaria and more depending on which country you are in. [3]

     The putrid mess and dead animals can breed flies which can help spread infections.  It may take time to clean up the water and mess so ensure you are protected with a good insect repellent.


    Contaminated drinking water

     The drinking water in the tap can be contaminated after a flood event by–

    • Contaminated floodwater entering the water system through damaged water mains
    • Power failure at the water treatment plant not being able to purify the water

     To prevent illness from the contaminated drinking water have some bottled water in the pantry and follow the directions of the local authorities.  You may just have to boil the water.


    Power lines

     Damp ground and water can conduct electricity from fallen power lines or damaged power equipment.  Don’t rely on the circuit breakers or earthing devices to save you.  Assume all electricity lines and equipment is live.  And even if they are not live, someone can just turn on the power and they will be live again.


    Dead animals

     Animals that have drowned in the floodwaters can contaminate the water, breed flies and stink out the place.  Damp conditions and animals in water break down quicker than animals on dry land as the conditioners are more favourable for the microbes.  Try to remove dead animals early to save the smell.


      Contaminated soil and debris

     The hazards down go away with the floodwaters.  Anything that can absorb water (foam, wood, carpet, materials) will absorb the contamination from the floodwaters.  This will cause smells, staining, microbe increases and the item will decay faster.

     Soil that is contaminated may become infertile and stink every time it gets damp.  The contaminated soil may need to be removed and replaced with fresh soil. 


    Panicked wildlife

     Flood water and flowing water can have panicked wildlife fighting for life.  If you are walking through the water, you may become the lifesaver of a passing lizard, spider or snake.  You may want to save the animal but do it safely at a distance.  Even domestic animals can be dangerous if they are panicking.

     Picking up an injured animal can result in a bite or scratches.  These injuries can be contaminated with bacteria and viruses.





    Driving in flood water

     Being in a vehicle does not make you immune to the dangers of floodwaters.  More people die in floodwaters by driving through and other means.

     It can take as little as 15cm (6 inches) of floodwater to reach the floor of most modern cars [1].  This can cause the car to lose grip on the road and start to float.  By this stage, you have lost control of your vehicle.

     Any current slow or rapid can move the vehicle off the road or bridge.   Vehicles can become submerged or caught up on a tree at an angle making escape difficult.

     Moving water that is 60cm (2 feet) is enough to sweep away heavier vehicles such as a four-wheel-drive [1].  The “Don’t drive through flood water” message has been around for decades but there are still people ignoring the message. 

     Instead of driving through flood water park at a high spot and wait it out or turn around and go to higher ground.

     If you leave a vehicle in floodwaters leave a note on the dash saying you have safely evacuated the car, so the emergency services do start looking for you. 

    Swimming in flood water

     Children and young adults see water and want to swim.  Flowing water becomes a surfing or boating activity.  They don’t see the dangers of contaminated water, floating debris and wildlife.  Every year people are swept away downstream or into underground stormwater systems while swimming in the floodwaters.

     And then there are all the microbes they are breathing in or ingesting.


     Stress and Trauma

     Apart from the physical dangers, there are psychological problems.  People are stressed by –

    • Worrying about family members in the area
    • Damage to their home, cars and belongings
    • The drama portrayed on the media and social media
    • The loss of loved ones
    • Missing or dead pets
    • Loss of income as businesses are affected
    • The whole situation became overwhelming

     How to avoid the hazards of floodwater

    •  Stay out of the floodwater to prevent contamination and injury.
    • Don’t drive through flood water of any depth
    • Change your plans if the area is flooded
    • Thoroughly wash anything that has come into contact with the floodwaters (objects and body parts)
    • Listen to local authorities’ safety advice
    • Have an emergency kit at home and in the car to see you through the short term disruption
    • Wear your protective equipment when doing a flood clean up.



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