Erosion control Project

My 121 Ha property, “The Granites” at Carapooee, consists of a granite outcrop with sloping granitic sand terraces at the foot. There is about 7 km of erosion gullies on the property, which represents a serious loss of habitat, resulting in a significant sediment load in the Carapooee Creek and ultimately the Avoca River.

The sandy soil of the terraces has very little clay to bind it and so erodes readily. There is an underlying soft sandstone layer which is eroded slowly by the process of falling water.

The photo below shows typical erosion.

The Project

The Kara Kara Conservation Management Network secured a grant for some erosion control work on this property. The grant paid for 60 tonnes of rock, gravel/sand mix, filter cloth and seeds for regeneration.

Half of these materials have been used to control the erosion in a 400 m section of one gully, where about ten leaky weirs have been placed using the rocks across the eroding sections and a further five areas of undercut have been stabilised.

The objective of the work is to

• stop the spread of drops from propagating upstream

• stop widening of the gully floor

• stop further undercutting

• Slow the water speed in the bottom of the gully

The slope of the steep sections and drops were jack hammered until the slope was about one in five. Filter cloth was laid across the gully floor and covered with the sand/gravel mixture. Rocks were the placed over the filter cloth to form a water race and leaky weir to slow the water flow and collect sediment.

This has effectively stopped all erosion in the bottom of the gully. Any further erosion of the sides of the gully results in reducing the slope of the wall. Eventually the walls will become revegetated. The sediment from this erosion is collected by the leaky weirs and does not leave the erosion area.

Other leaky weirs were placed across the gully floor to slow down the water flow.

A typical undercut is shown below. By placing a rock wall beside the undercut, eroding water flow is kept away from the undercut. The undercut will eventually collapse, but will not widen further.

The work requires at least annual inspections and minor repairs. As the sediment builds up at each wall, additional rock will be added to raise the height.

Natural Healing of some gullies

Some of the gullies have self-healed just by removal of stock (in 1995) and reducing rabbit numbers. The slope of the sides of these gullies has become less steep and grasses (mainly weeds) and trees are regenerating there, thus stopping further erosion.

The photo below illustrates this effect.

Round the Traps

Current News

Bulokes

(Allocasuarina luehmannii) are listed under the Victorian Flora and Fauna Guarantee Act 1988 and endangered under the Federal Government Environment Protection and Biodiversity Conservation Act 1999.

In this district, although there are many stands of Bulokes, most are quite old and very few are regenerating. This is mainly due to grazing pressure from stock on farms as well as rabbits and excessive numbers of kangaroos.

I have noticed that many of these trees are suffering from the recent long drought and there is often sever wind damage, possibly due to their age.

On my property at Carapooee, there were 28 old Bulokes when it was purchased in 1999. The property is under a Trust for Nature covenant, to protect it in perpetuity.

Even though there has been no stock on the property since 1995, there was very little recruitment and seemed to be only from suckering in areas disturbed by erosion. In recent years, however there have been hundreds of seedlings of various ages around all of the female Bulokes as shown below.

The only difference that I can see is that the rabbit population has been dramatically reduced by, the drought and constant ripping and fumigating.

I would like to see small areas on farms fenced to exclude stock and allow some regeneration.