Working file – Scottv 2 | Landholders Driving Change

Graziers get help from the group to tackle erosion problems

Three Mile is a 258 ha property 6.5km south west of Scottville owned and managed by Carl and Leanne Groocock.

Todsure is a 299 ha property located 4km south west of Scottville owned and managed by Carl and Leanne Groocock and their daughter and son-in-law Barry and Brooke Collett. 

The neighbouring properties sit on Three Mile Creek in the Pelican Creek sub catchment of Bowen River and have two major land types – mostly narrow-leaf ironbark on deeper soils with a smaller area of alluvial country along Three Mile Creek. 

The majority of drainage lines through the narrow leaf ironbark country are severely gullied, while the alluvial country along Three Mile Creek is severely scalded, that is, claypans. 

Most of the soils are Sodosols which are highly prone to erosion problems.

Three Mile and Todsure graziers Carl Groocock and Barry Collett.

The active gully was reshaped and treated with topsoil and seeded with pasture varieties. The area between a newly constructed diversion bank and the gullied area was contour ripped to reduce surface water runoff feeding the gully, and to help increase infiltration.

Following rain in February 2020, the reseeded gully area responded well. When done in association with other land management practices, contour ripping can reduce sediment erosion in areas with highly-erodible soils. 

THREE MILE

One site remediated

This site was an active gully about 15m wide and 0.8m deep, consisting of a series of actively eroding gullies. 

It was remediated by a 250m long diversion bank and a 20m water spreading structure at the outlet of the bank.  

The area between the diversion bank and the gullied area was contour ripped to help manage surface runoff feeding the gully.  

Earthworks took four days to complete.

The reshaped gully and immediate surrounds was treated with topsoil and seeded with pasture varieties.

 A new fence has been constructed to manage stock access to the site.

Landholder benefits

  • Remediation of erosion features that will reduce soil erosion and sediment entering local waterways.
  • Improved soil and pasture health, and improved paddock water infiltration, surface water management and groundcover in, around and above the erosion features.
  • Improvements in land condition and water quality on the property.

A 250m long diversion bank was constructed to help reduce surface water runoff to the nearby remediated gully.

Following rain in February 2020, groundcover responded well.

Before and after: The diversion bank and surrounding area that was contour ripped.

Hover on each of these photographs taken before remediation work began to see the end result.

Looking down from the central section of the diversion bank towards the gullied area that was reshaped and surrounding area that was contour ripped to reduce surface water runoff and promote water infiltration.

On-ground works have resulted in water that falls on Todsure causing no erosion damage and soaking into the ground to grow pasture. (Hover on the picture to remove the labels to see more clearly).

Looking back to the dam wall from the gully head before remediation work began.

Members of the Scottville Mob gather on the newly-constructed dam wall at Emohruo during a field day recently.

 

TODSURE

Two sites remediated

Site One

This site was a minor gully that was reasonably stable but had the potential to become active and get larger. 

The site was remediated by reshaping the gully and filling it with river rock and coarse sand so that the fill was level with the surrounding ground level. This has pushed the runoff away from the erosion area onto adjacent well grassed areas.

Earthworks took half a day to complete.

Site Two

This site consists of a gullied drainage line that runs into Todsure Dam. During the wet season surface water runoff gouges this drainage line and flows into the ‘leaky’ dam before flowing into the creek. It was important to fix the drainage line, as well as the dam.

The top gully in this drainage line is a broad low feature while the main gully is about one metre deep. 

This site was remediated with two diversion banks  A small new dam was constructed over the main gully head, using diversion banks, water spreading structures and pasture reseeding to manage and divert surface runoff feeding the gullied section below the new dam. 

The existing dam below the gully will eventually be filled and reshaped to rehabilitate the area and allow water to shed more safely downstream.

The landholder put forward an alternative design for remediating this site that cost less to remediate than the original design option by eliminating the need for a rock chute structure. Instead, by building a new small dam, it has provided additional reliable water source. 

This design involved creating a small dam over the proposed location of the rock chute, while constructing two diversion banks, each about 200m long, and water spreading structures, and contour ripping was carried out to manage surface runoff feeding the gullied section below the new dam. 

This design involved creating a small dam over the proposed location of the rock chute, while constructing two diversion banks, each about 200m long, and water spreading structures, and contour ripping was carried out to manage surface runoff feeding the gullied section below the new dam. 

As the subsoil and rock on the property was particularly dry, and hard on the earthmoving gear, the new dam was not as big as expected, but it can be widened and deepened in the future. 

Diversion banks were 2.5m wide, 50cm high and 100-120m in length, on a 1 in 300 slope. Bank mounds were left flat on top to let rain soak in to help reduce erosion.

Exposed bank subsoil and reshaped areas were spread with topsoil and then hand sown with bags of Reclaimer Rhodes Grass and Tropical blend (Buffel grass, Jap rye, Secca). 

Earthworks took nine days to complete.

Fencing on Todsure will ensure paddocks are better spelled, pasture growth enhanced and grazing pressure more controlled around the gully sites.

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