Tag Archives: flood

What is a flood?

Floods are a natural, reoccurring process that have historically shaped the landscape of most countries. Southeast Queensland’s subtropical climate makes it prone to weather that can cause flooding, and as we’ve experienced in recent years, more extreme weather conditions have caused widespread mass flooding with challenging consequences. Floods in our region are predominantly caused by heavy rainfall, but may also be a result of swollen rivers and tidal surges.

There are two types of flooding that can occur:

Flash flooding refers to water coming ‘down’ and involves intense rainfall, usually over a short period of time, rapid rise of water levels and high flows of water moving through the catchments.

River flooding refers to water coming ‘up’ and involves prolonged rainfall and slow rise of water levels.

How does rainwater move through a catchment?

With a natural, forested catchment, most rain falls on hill slopes and vegetation. Vegetated hill slopes creates minimal erosion. Vegetation stores the rain in soil, slowly releasing water over time, which helps sustain flows of water during dry periods. In a highly modified catchment, such as a city or town, the natural vegetation has been dramatically changed, therefore hill slopes and catchments will react very differently. In these modified environments, impervious or hard surfaces, such as roads, buildings and roofs reduce the amount of rainfall that can soak into the ground, causing more water to become runoff. This fast flowing movement of water carries large amounts of sediment and pollutants into stormwater drains and out into our waterways.

What is litter?

Litter in our waterways is a serious pollution problem that affects our wildlife, aquatic habitats, water quality and the recreational use of our waterways. Litter is almost any material that is disposed of incorrectly, including: fast food wrappers, drink bottles, cigarette butts, poorly secured material escaping vehicles and rubbish bins, paint tipped down the drain and much more. It is estimated that approximately 80% of all waterway litter originates from land based activities.

Floods and litter

When litter is dropped on land, rain and flooding carries it into stormwater drains, which empty into creeks and rivers. Once litter reaches our waterways, it is very difficult to remove. If the catchment has no vegetation to slow down flood water, the amount of litter and pollutants that enter our waterways significantly increases.

How does litter affect waterways?

Queensland sadly has the highest amount of litter of all mainland states in Australia. After being washed into our creeks and rivers, discarded litter slowly makes its way to our oceans. Waterway litter is extremely harmful to wildlife, who become entangled or mistake litter for food, resulting in injury or death. Waterway litter caused the death of at least 100,000 marine mammals, including turtles, dugongs and whales, as well as almost one million seabirds worldwide each year. Aquatic habitats such as coral and seagrass beds are also damaged by litter. In addition, litter makes our waterways look dirty and unattractive, which reduces recreational use and impacts on tourism.

Litter impact facts

  • Studies have found that 30-40% of sea turtles found dead in Moreton Bay have a significant amount of plastic litter in their stomachs.
  • 80% of litter in our waterways is made of plastic such as plastic bags, plastic water bottles and food wrappers. Most plastic objects never biodegrade – they just break down into smaller and smaller pieces.
  • ŸAn estimated 4.5 million cigarette butts are littered every year worldwide. Cigarette butts contain toxic chemicals which will start to leach out within an hour of contact with water.
  • ŸLiquid litter such as paint and household chemicals contain toxins that are hazardous to people and wildlife, and degrade water quality. Even when these products are diluted they should never be tipped down stormwater drains or dumped into or near waterways.

Healthy waterways

Healthy Waterways is a not-for-profit, non-government organisation working to protect and improve waterway health in SE Qld. They facilitate careful planning and coordinated efforts among a network of member organisations from government, industry and the community.

Healthy Waterways Clean Up Program

The Healthy Waterways Clean Up Program collects over 240,000 items of floating litter from SE Qld waterways each year. The program, which has been operating for over 10 years, also aims to increase community understanding about the issue and impacts of waterway litter. The Healthy Waterways Clean Up Program recorded a 50% increase in the number of plastic water bottles collected from local waterways between 2007 and 2012. Please use a reusable water bottle instead!

8 tips to limit your litter

1. Dispose of rubbish in a bin and ensure rubbish is secure.

2. Use the three R rule: reduce your use of plastic, reuse items you may otherwise throw away, and recycle as much as possible.

3. Use a reusable water bottle instead of buying plastic water bottles.

4. Smokers, out your cigarette butts in the bin!

5. Pick up any litter you see and remind everyone to dispose of rubbish carefully.

6. Report littering and illegal dumping via the Department of Environment and Resource Management or your local council.

7. Carry a litter bag in your vehicle or on your bicycle.

8. Contact your local catchment group to organise or join a waterway litter clean up day or program. Clean Up Australia Day activities are important, as well as regular ongoing activities year round.

For more information, contact:

Healthy Waterways



Australian Marine Conservation Society



Courtesy of Healthy Waterways.

Well, it’s official. I’m am definitely over this excessive rain, and so are my chickens, dogs, cats, guinea pigs and everything in my garden, including my plants and trees.

While a couple of weeks has done a lot of good in the garden, greening up everything, helping food production and growth, and bringing frogs and other life, the pendulum has swung and enough is enough. I am beginning to see signs of water logging in some beds, the chickens are unhappy and I’m seriously behind on all major projects around the house. Including just the ability to catch up and clean up since before Christmas.

The bad news

So what happens in our gardens when they start to get water logged? What does water logged mean? How much rain is too much rain, and what damage can it cause in the short term? When the ground simply can’t absorb or drain anymore water, water starts to sit in the soil, and for too long, which causes loss of macro and microbial life, such as worms, beetles, spiders and other arthropods, plus all the good bacteria, protozoa, nematodes and many more, through either mass exodus or death.

At the same time, organic material in and on the soil, such as compost, mulch, manure, etc reaches maximum water absorption and starts to rot. This can cause problems when the rain stops and the sun comes out, in the form of smell from decaying matter, and the usual suspects that this brings, such as flies, maggots and others. This drenched, rotting matter can also stay wet in the soil for longer than needed when rain stops, continuing to rot plant and tree roots if too close to them.

At the point when plants and trees simply cannot ‘drink’ any more water, or store any more water in their roots, root rot can set in if roots are not in well draining soil, causing damage or death. This will occur faster in species that don’t like ‘wet feet’, while others will survive and withstand wet feet for longer periods.

The signs

When a garden bed or soil has reached maximum absorption water will appear to sit on the surface in puddles, or garden beds with borders can even fill up. If this water sits in the bed or soil, without any drainage, for more than a day (after already prolonged rain), damage can set in. Roots literally drown. At this point, maximum saturation has occurred and detrimental processes kick in. Some plants or trees may show signs of water logging quickly, such as yellowing leaves, rotting of leaf veins, leaves falling off, wilting and softening, darkening of root colour, with usually a decayed smell, as the skin or bark of roots is rotting. Other signs include young shoots and tips dying off, stunted growth, low or no seed or fruit production, and often swelling. Any or all of these equal stress for the plant or tree. And of course any seeds or seedlings planted are very unlikely to germinate or mature due to swelling and rotting.

A little science

Water logging causes problems for plant and tree roots in a few ways:

  • ŸRoot function is reduced because of limited oxygen and CO2 diffusion
  • This attracts organisms that feed on decomposing roots
  • This also the prevents the stems, leaves, etc of the plant from obtaining nutrients and water (even though there is too water in the ground and roots)
  • Water logging in summer and warmer climates is much more damaging because root oxygen-CO2 exchange is a lot more active and demanding. Plants and trees can often survive water logging much better in winter or cold climate soils
  • Aquatic and marginal aquatic plants, plus some ‘wet feet’ plants and trees, can survive very well in water logged soils
  • Some soils are more water logging than others, because of their denser texture and poor drainage qualities, and will remain very wet for longer periods after rain has stopped

Some short term solutions and remedies

  • After heavy, prolonged rains or flooding, wash or sweep up organic and other matter which may have collected along pathways, drains and surfaces, to prevent this material from polluting and decaying on or near garden beds. In floods especially, this matter can be polluted or contain toxins. Do not handle without gloves.
  • Avoid walking or moving on soil to reduce compaction and muddying soil. Only work your soil again when it has suitably dried out and is ready to be worked
  • On inspection, gently remove as much water logging affected parts of plants as possible – leaves, shoots and tips, branches, etc, plus pull out and dispose of any dead or affected plants and trees
  • After flooding, do not eat edibles for a while, as they may contain pollutants. Discard any suspect plants or fruit, especially edibles that are eaten raw
  • Avoid growing edibles in soil or beds you suspect may contain toxins, especially edibles eaten raw and quick grow crops like salad greens
  • Because of leaching in floods and water logging, apply a suitable fertiliser and mulch to the soil once conditions are favourable again
  • Quality foliar (leaf surface) fertilisers can also help to rebuild and nourish water logged plants and trees
  • Once you think plant and tree roots are no longer water logged, water them well, as they can suffer from not enough water, even after a flood or heavy prolonged rains

Some longer term solutions and remedies

  • Seek to improve your soil structure and drainage properties through healthy cultivation and soil fertility, such as increasing the humus content
  • Try aerating your soil and beds with a deep soil aerator
  • Create mounded or raised garden beds for planting where possible
  • Increase drains and drainage around and away from garden beds to divert rain and flooding where possible
  • Create flow stoppers to slow down water flow into certain areas when flooding or heavy rains
  • In lower areas that are more susceptible to water logging or flooding, choose water loving plants and trees, or those more tolerant of wet feet and wet soils

With a little common sense and planning, gardens be improved to prevent, reduce or minimise water logging and light flooding. Low areas or beds can be raised, or managed differently, such as growing different plant species. Soils can be improved to drain better. General drainage and water flow can be improved around gardens and properties. There is usually always a solution to water logging and flooding challenges. It just requires a little work and design. Best of luck!