So willows cause flooding on floodplains?

All over the internet you can read about how willows cause increased flooding. For a sample, just try here:

“…..the trees are a menace and cause flooding….”

or here:

“They form thickets which divert water outside the main watercourse or channel, causing flooding…..”

or here:

“…..willows form thickets which can cause floods and erode vulnerable banks, especially on flood plain areas.” (my emphasis)

Although some of us hold to the peculiar idea that climate extremes (especially high rainfall periods) have something to do with it, according to anti-willow literature, it is willows that cause flooding.

Furthermore, as far as I can tell, flooding is a BAD thing.

But have you ever heard the phrase: ‘…of droughts and flooding rains.’? It’s from Dorothea Mackellar’s well-loved poem ‘My Country’.

If you’re someone who occasionally get’s the chance to step outside the office, you’d have noticed that southeast Australia is full of floodplains–they’re all over the place! These are natural landscape features which occur regularly in proximity to flow-lines. They are periodically inundated by flooding and have, over time, developed a generally flattish geomorphology composed of alluvial deposits. Often they are populated by species and ecological communities that are adapted to occasional flooding.

So, floodplains are a sure indication of the natural process of flooding. In fact, not much could be more natural in southeast Australia, because flooding on floodplains has long been an essential life-giving driver of many major ecosystems in this part of the world.

But what happens when an Australian floodplain floods? Well, lots of things really: wetlands are replenished with water and nutrient, many fish and birds spawn and breed, forests are inundated with life-giving waters causing spikes in seeding and seedling recruitment.

The Barmah-Millewa forest (links above) is just one very large example of how floodplain ecosystems rely on flooding to function properly, but these same principles can operate at any scale down to even the smallest surface flow. Flooding boosts nutrient and hydration levels in soils adjacent to flow-lines. Within native and non-nativist ecosystemseven within agricultural ecosystems, the productivity of floodplains is boosted by periodic flooding.

So what’s the story with the story about how willows are bad because they increase flooding? Surely more flooding is a major ecological benefit (and an agricultural-productivity benefit too); especially within Australia’s widely incised stream systems which now flood less-often than they once did–or even not at all. Surely, under these circumstances, flooding caused by willows should be widely welcomed.

But no; this natural process of nutrient and water replenishment on floodplains, which apparently willows are increasing (actually, just helping to reinstate), is often presented as a terrible problem.

Obviously, increased flooding wouldn’t be welcomed as a good thing where human settlements and infrastructure have developed upon historic floodplains. But does this mean willows are considered as bad for causing floods when they might damage human infrastructure, but good for causing floods when ecological and agricultural productivity are boosted?

…..Well no, apparently not; because you don’t see anything written about the ecological benefits of riparian willows that cause floods, even though we know flooding is essential to the health of Australian floodplain ecology.

Basically, it seems the take home message from all of this is perfectly clear:

Floods in Australia can be both good AND bad…..

……except if they are caused by willows when they must be unquestionably bad under all circumstances.

Is that a fair assessment of the situation?

7 responses to “So willows cause flooding on floodplains?

  1. Clear Water Floods .

    A old fashioned clear water flood is a lovely thing to see .

    Had one a few months ago . 10 ” of rain in a few days after a long dry spell .

    The sheet erosion from the neighbours upstream came boiling through our boundary fence , a turbid mix of cow manure , wombat scat and topsoil . Knocked it down .

    Firstly it ran into our dry meandering stream beds and disappeared into the floor . A few hours later water started bubbling up through the floor downstream and flowed upstream to meet the walking pace front headed downwards .

    Then bubbles started appearing all over the flood plain , pressurised by the rising water in the channel .
    The turbid flood ( or liquid fertiliser as I prefer to think of it ) , hit fascines , flipped over to bleed energy and overtopped the levee banks .
    It spread over some 20 acres , hitting the clear filtered water coming up from the aquifer and precipitating its load .

    Thousands of tons of water left our property filtered clear , oxygenated and headed for Sydneys drinking water supply . To whom we send the invoice for environmental services ?

    The frogs started laying eggs next day . If we were on the western fall it would have been the trigger for cod and perch breeding too.

    Self Levelling .

    I love to see how the system reinforces and self levels the live weirs . Phragmites is our keystone species . It came back when we got rid of the cows .
    Rising water will power through any little rills in the berm . faster water carries more sediment load .
    As it strains thought the rushes it drops the load , then rhizomes grow up into the new soil and automatically fill the rills .
    As long as the hard hooves are kept out this self repair system can add metres in height to a live weir in only a decade .

    Now days even the biggest flood doesn’t over top the live weirs , it moves through them .

    We do love a good flood .


    • Sounds like you know how to do them right Peter! Floodplains have always had the most productive and fertile soils, those valley-fills don’t build themselves with in-situ rainfall. Self-levelling indeed, just add vegetation.

  2. Pingback: What?! So suddenly willows cause erosion?!? | Flood Creek Non-Nativist Landcare

  3. Floodplains are for flooding. Yes it’s their main ecological function. Preventing flooding is a sure sign of ecological illiteracy. Without regular flooding, living streams and rivers cannot cleanse and rejuvenate themselves. Without floodplains, streams and rivers become polluted ecotoxic drains.

    Warnings of global water calamities are coming from many sources with the Arts leading the way ~ as always! Tolkein’s Lord of the Rings is not a children’s story. It is a chilling parable of modern times. We are beset by hordes of Orcs ~ those tree hating, river killing, water thieves who despise Nature as incompetent.

    To understand why Nativists and other Orcs are so full of hate and loathing for willows, you need look no further than colleges and universities teaching biology and ecology as closed system sciences. These nescient institutions are ignoring the irrefutable fact that all ecosystems and living communities are dynamic open systems which cannot be studied or understood using closed system scientific theories or mechanistic models. To do so is scientifically invalid . And their dodgy science is compromised futher by their failure to ensure their graduates have adequate spatial cognition and ecological literacy.

    On-going research of spatial literacy among post-grads and academic lecturers in Asia-Pacific English teaching universities is providing copious evidence that a traditional Asian axiom is spot on! Knowledge and intelligence are inversely related!

    Laozi the renowned Chinese sage refused to teach Confucius. After ignoring his initial requests, Laozi told Confucius to go away, telling him his head was so full of knowledge, there was no room left for intelligence. And so it is with our knowledgable post grads and closed system academics whose heads are so full of knowledge, they can no longer “see”. Their spatial literacy is so appalling, they cannot perceive the exciting dance of riparian ecosynthesis. Blindly believing in their academic knowledge, their knowledge filled minds impose “academic” world views onto everything they encounter. This helps explain why among traditional indigenous communities in Asia-Oceana, PhD is now known as a mental affliction known as “Permanent head Damage”.

    There are several reliable indicators of poor spatial cognition and ecological illiteracy among the eco-colonial communities in Oceana: One is the perception that willows cause floods. Another is the Nativist dogma that “native species” are superior ecologically to other biota. Sadly, ecological illiterates seem to have no respect for Nature either. In their blind ignorance they wage war on Nature with weapons of mass destruction ~ burning, bulldozing, biological warfare and indiscriminate applications of ecotoxic poisons.

    If you would like to know why willow communities are so important to our streams, river and lake ecosystems, I invite you to read “The Crucial Roles of Willows in Sustainable River Management” published by Watershed System Foundation, Aotearoa 2009.

    • Hi Haikai, my experiences in southeast Australia have made me aware of how dramatically changed this landscape is by erosive incision and a consequent lack of flooding on floodplains. Whether a person sees flooding as generally good or generally bad, it makes no sense for them to speak of ecological “restoration” without knowledge or consideration of past or present hydrology and fluvial morphology. Willow removal and the planting of eucalypts alongside incisions in former swampy meadows as if they were now restored pre-European streams shows exactly how ecologically and historically illiterate we are. Who let all these cashed up headless chooks loose?

      I’m fortunate enough to have a copy of the document you mention and would like to make it available to readers of this site if possible (can’t find it online elsewhere). Will contact you outside of this forum to discuss.

      Interested readers should watch this space.

      Regards, Ben

  4. great read and analogy 🙂 where are the hobbits when we need them!

  5. Read this article. Cause? Willow warriors removed willows in an upland, corridor and left all the cut debris behind. Guess what happened next??
    Read the article.

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