Floodwater is often contaminated by overflowing sewerage or septic systems, and by agricultural or industrial wastes and chemicals.
The main health risks from floodwaters are the transmission of water-borne diseases. Contact with floodwaters can lead to stomach illness, wound and skin infections, and rashes. Eating contaminated fruits and vegetables that have been in contact with floodwaters can also lead to illness.
To protect your health, assume all floodwaters are contaminated. Avoid contact with polluted water and soil if possible.
How to protect your health during a flood
Floodwaters can contain many things that may harm human health, such as:
- human or livestock waste
- household waste
- industrial and medical hazardous waste
- lumber, vehicles and building materials
- debris that might contain asbestos or other harmful materials
- wild animals such as rodents and snakes
Assume all floodwaters are contaminated
Don’t wade through water, even shallow water; and try to avoid contact with mud and dirt. Wear gloves if you are handling pets or items that have been in contact with floodwater, mud or dirt.
If you cannot avoid contact with floodwaters, we have prepared the following tips to help you avoid infection.
Before entering floodwater
- Cover cuts and scratches with waterproof bandages.
- Wear protective clothing such as rubber boots or solid shoes, rubber gloves, and goggles.
After coming into contact with floodwater, mud or soil
- Wash your skin with soap and clean water as soon as possible. If you don’t have soap or water, use alcohol-based wipes or sanitiser.
- Wash contaminated clothes in hot water and detergent before reuse.
- Take care of any wounds, and seek medical attention if necessary.
- If you are using watercrafts such as kayaks, boats or paddleboards during a flood, make sure they’re cleaned well afterwards to avoid contamination and infection.
Wear gloves and always wash your hands thoroughly after participating in flood clean-up activities
Avoid swimming in waterways or beaches after a flood
EPA advises against swimming at all waterways and beaches for 48 hours after a heavy rain, and for much longer in the event of a flood. You should avoid contact with the water if:
- you notice the water is discoloured or has an odour
- there is sea foam following flooding or heavy rainfall
- there is a current EPA water quality alert.
Swimming in poor water quality can lead to illnesses, such as gastroenteritis. You should see your doctor if you suspect you are unwell from swimming.
Increased risk of algal bloom outbreaks after a flood
Algae and cyanobacteria (also known as blue-green algae) are organisms that live in water and can grow quickly, or “bloom." This can occur in slow-moving/stagnant water which contains nutrients. This is often due to runoff containing fertilisers and wastewater which may contain sewage.
Blooms can look like foam, scum, mats, oil sheens, or paint on the surface of the water. A bloom can change the colour of the water to green, blue, brown, red, or another colour. Some algal blooms may not be visible.
After a large flood event, increased nutrients, low flows and light can create ideal conditions for algal bloom growth. This can lead to large outbreaks. Algal blooms can affect fresh water environments such as rivers, creeks, lakes and other inland water bodies. They can also affect marine environments like Port Phillip Bay and coastal waters.
Most algae are harmless, but some are harmful to people and animals. Some algae can produce toxins which can cause serious illness.
Harmful algae can cause irritation to the skin, eyes, ears, nose, and mouth with direct contact. Drinking algae-affected water or consuming food (such as fish or shellfish) containing these toxins can lead to gastroenteritis. This can cause vomiting, diarrhoea, fevers and headaches. These toxins may also affect the liver or nervous system and have more severe health outcomes.
If you are concerned about your health, you should seek medical advice immediately.
Drinking water from a private or town water supply
Floodwater and flood-related debris can contaminate private water supplies. If your water supply looks, smells or tastes unusual, do not use it. Do not use potentially contaminated water for drinking, preparing food or bathing. Do not give it to animals.
- Department of Health has guidance on the use of private water sources during a flood event.
- If your town drinking water is impacted by a flood, contact your local water authority for information.
If there is a flood and your water supply looks, smells or tastes unusual, do not use it.
Risk of foodborne illness from eating flood-impacted produce
If your garden has been in contact with floodwaters, your homegrown produce may not be safe to eat. While some of your fruits and vegetables may be salvageable, if you are in any doubt, it is best to dispose of them.
Do not eat:
- leafy vegetables, such as spinach, cabbage, lettuce and kale
- produce that was already damaged before the flood. For example, a tomato with split skin with exposed flesh will not be safe to eat.
- raw soft fruits, such as strawberries or raspberries. They cannot be washed thoroughly, so they are only safe if they can be cooked.
Use caution before eating:
- vegetables with protective shells, husks or skins, such as peas and sweet corn. They should be thoroughly washed, peeled and cooked before eating
- fruits and vegetables that were immature at the time of flooding. Although they should be safe to eat by the time they are ready to harvest, they should still be washed thoroughly before eating.
While some of your homegrown fruits and veggies may be salvageable after a flood, if you are in any doubt, it is best not to eat them.
Eating fish from flood affected waters
Water from floods is usually contaminated and it is not safe for fishing.
Do not eat fish if:
- it was dead when you found it
- it was alive when you caught it, but it looks diseased, stressed, lethargic or is behaving in an unusual way.
Use caution before eating:
- fish taken from water, where flooding has passed. They should be thoroughly rinsed and gutted before cooking.
Soil testing for flood-impacted residents
We are collecting soil samples from flood-affected areas to assist residents in their clean-up efforts following recent floods. Soil samples will be collected and analysed for bacteria (E.coli), trace elements such as metals and metalloids, and organic chemicals such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) and petroleum hydrocarbons.
Please note that due to the time it can take to transport samples over increased distances to the laboratory, it may not be possible to analyse for some parameters.
You can request for your soil to be tested by calling the EPA on 1300 372 842 (select option 8). EPA will test your soil and provide a report to property owners, with broader results provided to councils to inform their clean-up efforts.
If you would like a PDF version of this information, download floodwater soil testing factsheet (PDF, 476KB)
Flood-affected residents can request soil testing at their property by phoning EPA on 1300 372 842 (select option 8)
Reviewed 30 November 2022