Thursday, 23 May 2013

Darryl Hill's soil sense at Mt Bundy Station

Darryl Hill holds the attention of attendees at the Mt Bundy Field Day

Darryl Hill has spent years observing erosion on pastoral stations and testing erosion controls first hand. He is now recognised as one of the leading experts in erosion control across Australian Rangelands.

Darryl presented a soil conservation workshop at the Mt Bundy Station Field Day recently. These are what I thought were his key messages:

·         The greatest cause of fenceline or track erosion is windrows channelling water flow away from natural drainage lines - Reinstate the natural flow direction as often as possible (by removing windrows or installing banks).

·         Maintain or re-instate broad sheet flow rather than narrowing flows. Concentrated flow has higher velocities with greater risk of scouring.

·         Peg banks with a dumpy level so they direct water in the direction of natural flow and onto stable vegetation at a slow velocity. A grade of 0.2-0.5% is recommended. This means a fall of 5cm over a 10-25m long bank.

·         Start building banks at the top of the catchment and work down.

Darryl building a bank to divert water away from a gully head
·         Use flat bottomed drains instead of “V” shaped drains. “V” drains concentrate flow and therefore carry water at higher velocities, and are harder to maintain.

·         Batter the sides of gullies so any water flowing in can flow gently without scouring the base and causing continual gully migration.

·         It is often uneconomical to fill washouts. If erosion controls are installed, a washout will usually rehabilitate itself.

·         When maintaining fencelines and firebreaks, dig the blade in only as much as you need to and as little as possible (water crossing sunken tracks can start gullies).

·         Spread windrows back over the track to fill potholes back to natural ground level. Don’t cut with the blade down to the depth of the deepest pothole.

·         The washout is the result and not the problem – Usually it is rainfall that is blamed for the erosion, not realising that the roadway may be the cause.

Darryl said that erosion control measures on tracks and fencelines:

·         Reduce maintenance time by 30-50%.

·         Reduce travel time by 5 – 10%.

·         Reduce vehicle maintenance by 5 – 10%.

·         Increase fire break effectiveness by 2 – 5%.

·         Decrease the risk of stock escaping from paddocks.

·         Decrease soil and silt levels flowing into stock watering dams, waterholes and watercourses.

Listen to Darryl by clicking here

Listen to the ABC's Carmen Brown and property owner Scott Witham by clicking here

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