By KIERAN FINNANE
The popular misconception about sand being taken out of the Todd River is that this is done as a flood mitigation measure, deepening the channel to allow a greater volume of water to flow within the banks. In truth, it would take major works to achieve this, including the removal of causeways and the re-location or re-laying of services that are under the river (such as water, sewerage, and electricity).
The works that are undertaken are better described as “channel improvement” to prevent channel migration and bank scouring.
The Town Council’s Director of Technical Services, Greg Buxton explains why this is done “to ensure the river doesn’t change course and endanger the properties close to the existing river banks.”
The sand won from the works is used at the landfill, mixed with other soils to cover rubbish. This use does not motivate the works, says Mr Buxton. Council’s new management regime at the landfill has reduced the requirement for cover by 65% and it will be further reduced when the new transfer station is built, by the end of 2012 or early 2013. This means that there is more than enough clean fill both stockpiled and coming in from construction sites, in particular from infrastructure works in the town camps, to cater for cover needs for years to come. Having the river sand as part of the mix puts it to use but it could be done without, says Mr Buxton.
Guided by bed level data produced by the Department of Natural Resources, council has completed sand removal from north of the Schwarz Crescent causeway. Works downstream are waiting for Aboriginal Areas Protection Authority (AAPA) approval. As reported earlier this week (see separate article, ‘No shift in council’s priorities in the river’), works at Heavitree Gap are seen as a priority and would contribute to reducing the threat of flooding. “Silt, fines and sand” deposited at the gap by flows have “grassed up” with couch and kikuya, matted into a solid mound (pictured) that now stands well above the Bloomfield drainage line. These conditions could lead to the river breaking its banks in a Q20, let alone a Q100.
Mr Buxton says action to remove this “beaver dam” has been supported by three native title holders who contacted council at the beginning of the year on the matter. AAPA, however, is obliged to consult a wider group of custodians before a certificate can be issued. Mr Buxton says they are working towards a certificate that would allow re-channeling works on an on-going basis to bring the bed back to “a manageable level”.
The Alice Springs News Online asked Mr Buxton why that situation had been allowed to build up to the point that it has. We recalled the extensive works to clear this section of the riverbed of weeds, particularly couch grass, and sand, undertaken in the early 2000s as part of the Alice in 10 Todd and Charles Rivers Project. Why hasn’t there been regular follow-up maintenance?
The Alice in 10 project was before Mr Buxton’s time – he’s been in his current position for four years – but he ‘s also of the view that the work has only become necessary as the result of the rainfall over the last 12 months.
This time 11 years ago we were reporting on the lack of a long term strategy to manage the river for weeds. There’s no sign of this changing anytime soon.
We put to Mr Buxton that council’s management of buffel and couch amounts to no more than a token effort. However, he does not agree that these grasses are “a huge problem”. He says council manages them by slashing in an ongoing six to eight week cycle, with its own crew aided by trusties from the prison. He admits, however, that this effort has been “a bit light on” over the last couple of months as the crew was redirected elsewhere to slash and burn firebreaks, with priority areas identified by the fire service.
He also suggests that management of buffel grass would not have prevented the loss of the last three major trees in the river to burn, as they had been deliberately targeted by arsonists.
He says council could only consider a more intensive weed management program, including spraying, with funding from the government. Council simply does not have the workforce to do a careful spraying program.
Would he push for the necessary funding? He was reluctant to go that far.
Pictured below: Council removing river sand north of Schwarz Crescent in May 2010. Photo by ALEX NELSON.
Saturday, April 20, 2024
The freedom of the press still furnishes that check upon government which no constitution has ever been able to provide – Chicago Tribune.
The council did the right thing a few years ago removing the sand at The Gap etc., as poisoning the grass wasn’t going to remove the network of root and stem structures from the sand that was holding it together. Couch root and stem systems can be found 3 or more meters under the sand, and with a flood wetting down 3 meters then it will come back up again. It will take a lot of poison to kill the roots down that far, and as the length of root stem will be broken a lot of the time by flooding, spraying the top plant is not going to get the other little bits just waiting for the next flood.
It is only commonsense that the sand is going to move during each flooding of the river and end up in a position it is probably not wanted. The photo above shows how much sand had built up in that area alone. Water has always been close to the surface in the above area, making it difficult to ride a horse across the river at the above spot without sinking into the sand, even though it looked dry.
The road at times has been well above the river sand level, so if it is covered with sand it needs to be removed. Those mounds were not in The Gap in the 60s as we used to ride our horses home from the common every weekend without having to worry about obstacles in the creek bed. Spraying buffel grass on the surface doesn’t remove it as the seed falls into the dead clump and regrows. The only way to remove buffel is to dig it out i.e. bulldoze it out!!
Couch is a natural drought resistant ground cover that doesn’t stop other plants from growing. It is easy to mow and keep tidy as a lawn, requiring little or no care, to regenerate after a long dry spell.
Where couch is allowed to grow it will keep out the nuisance grasses like buffel and love grass, which move in when couch is removed.
The Alice Springs area grasses were said to be herbage and four day grasses which germinated and grew after very minimal rain, flowered and died off again until the next rain. Only the couch survived during each bout of rain.
Maxine (Posted December 24, 2012 at 10:02 pm): you claim couch “is a natural drought resistant ground cover that doesn’t stop other plants from growing.”
You also say that “Where couch is allowed to grow it will keep out the nuisance grasses like buffel and love grass, which move in when couch is removed.”
Just a question: if couch “doesn’t stop other plants from growing”, how then does it “keep out the nuisance grasses like buffel and love grass”?
I have never had a problem with it stopping my plants growing in my garden where ever I have planted various plants. I have observed when the couch was poisoned the buffel and love grasses took over, and landscapers had also told me they have observed this also.
The question is why didn’t these grasses grow in the same position before the couch was poisoned? For instance, my Peruviun lilies grow in my garden happily without the couch showing all year but during their dormant three months the couch takes over the bed as a ground cover. But as soon as the bulbs start growing again the couch goes back to ground. The end result is a constant green cover in the garden area where the bulbs have been for 30 years. I dug out all the buffel when I first bought my block and the couch came up and stayed. I am sure if I got rid of the couch I would then have a problem with the buffel again.
Maybe it is a grass thing! They tolerate different other types of plants but prefer to only have their own kind of grass growing next to them. From what I can remember from a kid the mitchel grass planes didn’t have much else growing in the area, not even many trees! But couch grass grows quite happily amongst the river trees and didn’t appear to be harming them, during the drought, if any this it would have helped retain the moisture in the top soil. Grass becomes damp to sit on at night. Couch does go to ground after the first frost and remains under ground until the frosts stop. During this time other plants can take over the area, like other grasses. In a nutshell, grasses usually like to have an area of their own, say like roses, so as couch is the lesser of the evils i.e. buffel and love grass, then I would rather have it in my yard. If you plant other species in your yard the couch will back off. Trees are only affected when couch or other grasses are present if you don’t supply enough water to support both species.