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Autopia Management

3 February 2011

Greenfleet flood report

Extensive flooding around Australia has caused tragic loss of life and immeasurable damage to private property and our thoughts and best wishes are with the affected communities. 

However, the flooding has been good for Greenfleet's biodiverse carbon forests with just a couple of minor exceptions.

Background

Southern and central Queensland and north eastern NSW experienced heavy rainfall in late December / early January, with two thirds of Queensland inundated and many districts experiencing severe flooding. 

Northern Victoria also received heavy rainfall in early January, breaking monthly records in some areas, with the resulting flooding reaching the highest levels ever recorded in several rivers. 

These very high rainfall and flooding events are believed to be mostly due the current severe La Niña event with the Southern Oscillation Index at +20 to +30. [i]

Many of the species planted by Greenfleet are tolerant of periodic flooding and are selected for this reason in areas near rivers and floodplains. Some iconic species like the River Red Gum rely on periodic flooding for long term health of the trees themselves and the surrounding ecosystem.

After a decade of drought in many areas the floods will benefit most Greenfleet forests, leaving behind soil that is rich in nutrients and organic matter with good moisture levels.

Observations

Greenfleet has inspected all sites in areas known to be impacted by the floods and has found just two sites with adverse impacts - one at Ipswich (Qld) and one near Maryborough (Vic). Of nearly 2,000 hectares potentially impacted, our concerns are limited to just 31 hectares. In contrast many of the other sites are showing rapid new growth as a result of the floods.  

At Bundamba, Ipswich, a 25ha site was flooded in early January when the Bremer River reached a peak of 11m. The site still has around 5-10cm of water across it, which is likely to remain until the end of the wet season in April. Significant losses have been noted in two species planted at the site, concentrated in patches. Some species on the site are also putting on new growth and are not expected to suffer from the ongoing flooding. Greenfleet will visit this site again in the coming months to gauge the extent of any additional losses and make any decisions on replanting at that time.

At Deep Creek, near Maryborough, a small 6ha site has been flooded by the Loddon River over the past week. Normally this would not be an issue, as the species planted are flood tolerant - however, the site was only planted in July 2010 and the young seedlings have been totally submerged by the flood. While we expect that some seedlings will not survive, there is potential for some survival, particularly in areas submerged for less than one week. Survival at the site will be assessed in the coming weeks once water levels subside and road access is restored. 

 

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[i] Southern Oscillation Index, Bureau of Meteorology http://www.bom.gov.au/climate/enso/