Wonders of the Big Wet

Ovens River red gums

In July, I invited readers to send in observations about how the ‘Big Wet’ years of 2010-2011 affected native vegetation in their local area. Many readers submitted fantastic comments, which I promised to synthesize. I’ve divided the observations into a series of topics which I’ll post in the next few weeks as there were far too many comments for one blog post.

This week, I’ve pooled together all of the observations from the wettest of the wet areas, from floodplains, rivers and wetlands. I’ve linked all of the observations to create the story below, and you can also read the original comments on the initial blog post if you wish. In the text below, the words in plain text are mine and those in italics were submitted by readers. Once again, I thank everyone who sent in their fantastic observations. I hope you enjoy reading them.

Down by the river…

In many regions, the most noticeable change was in wetland communities. In Gunbower Forest on the Murray, the drought-driven decline in tree health eased, saving many trees from a lingering death. New saplings came up after the floods subsided; about 200 red gum saplings appeared along our seasonal creek, all growing very strongly. But too much of anything ain’t a good thing, and flood waters killed inundated trees in some areas. One family lost most of our recently planted tubestock in the floods.

Death by flooding is part of the natural flood cycle in many areas. Billabongs that had been colonised by ‘wheat crops’ of young River Red Gums about 10–20 years old were dramatically transformed into truly aquatic ecosystems, after flood waters killed many colonizing saplings. Elsewhere, artificial weirs and levies that altered natural flow patterns created big problems….

In the lower Loddon and Avoca Systems… the huge flood combined with choking levy banks resulted in prolonged flooding of Black Box woodlands…. In some places this resulted in the death of the old Black Box trees, more than 50% in some parts of the forests… west of Kerang.Levy banks have ruined these floodplains and big floods will continue to degrade these forests as a result.

Luckily, many observations were far more joyous, as the floods prompted many wetland plants to flourish. It was floodplain heaven out there in 2011!! …. Wetland ecosystems… thrived on the plains, and upland swamps responded in a green flush.

Millewa billabong

In Gunbower Forest the cover and richness of understorey flora doubled in response to the high rainfall in 2010-2011 and areas that flooded… had twice the diversity of characteristic floodplain flora and half the array of dryland flora than areas that weren’t flooded.

The Big Wet was a great time for rare wetland plants. Rare and threatened flora flourished after the initial flood peak…. Two of the annual herbs that grew in a drying wetland were new records for Victoria. For one species, the nearest previous collection was about 1000 km away. 

After decades of drought, the Big Wet bought lots of Big Wonders. It was the first time that I’ve seen “flowering” Swamp Lily (Otellia species) in the red gum wetlands in my region…. It was really nice to have wetlands with these Swamp Lily flowers for a number of weeks.

I was also quite amazed by the response of flooding within a very ephemeral Black Box wetland that hadn’t flooded since the 1950s. It transformed from a chenopod woodland into a wetland, with an understory not even remotely similar to what it had before it flooded. The flood killed all the chenopod shrubs and a diverse range of flood stimulated herbs such as Mimulus, Trigonella, Centipeda, Triglochin, Lythrum, etc, came up in abundance. These species only grow following long muddy floods (i.e. a couple of months), and there is no way the seed was transported there, so it makes you wonder just how long these seeds can survive. When an annual species only grows for 3 months, and flowers for one week, once every 60 years, I guess it could be overlooked… It could also be made extinct really easily.

As one reader said… just when you think you know a wetland you realize you don’t.


And the prize goes to….

I promised prize books to the two readers who submitted the best responses: Ten Commitments: Reshaping the Lucky Country’s Environment (edited by David Lindenmayer and colleagues) and As If For a Thousand Years: A History of Victoria’s Land Conservation and Environment Conservation Councils, by Danielle Clode. The ‘winners’ are – insert drum roll here – Rus and Eris, both of whom sent in lots of fantastic observations. Congratulations to both of you, and many thanks to everyone who sent in their observations. Please leave a note below if the observations above trigger more memories from the Big Wet. Next week I’ll summarize the changes you saw out on the dry plains.

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