Building a sediment fence

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Being burnt out is a devastating experience. To help avoid the added worry of a contaminated water supply, sediment fences made out of fabric, shade cloth or straw should be in place as soon as possible after the fire so you are prepared before the next rain.

Protecting your most vital water supply from contamination should be your first priority after a fire.

If your dam or waterway is at risk, a quick and simple way to help keep your water clean is to build strategically placed sediment fences at the inflow points. The aim of a sediment fence is to slow down runoff containing debris, manure and soil so that any material drops out before it reaches the water.

Diagram of hill showing how rainwater runoff will flow downhill and how sediment fences can redirect it before water reaches a catchment at base.

Decide where your fences will go and how many you will need by assessing the catchment size, steepness of the slope and contours of the surrounding area.

Materials can include star posts and wire salvaged from fire-damaged fences, along with straw, shade cloth or other readily available items.

Diagram showing a sediment fence with a downwards curve at each end, which allows runoff water to flow around it.

To start building your fence, mark out where it will go with spray or by laying posts on the ground.

Drive star posts into the ground one to two metres apart. For steeper ground, posts should be closer together.

Run wires through steel post holes at heights of 150mm and 400mm.

Attach and strain between end posts.

If using shade cloth or fabric, roll out the material on the up-hill side of fence and fix to the strained wire with tie wire or fencing staples.

Run wire around the upper side at ground level and strain.

Two people working together to build a sediment fence using posts in the ground, green shade cloth and wire to fasten the shade cloth to the post.

Pin extra shade cloth up the slope using any old fencing wire or materials that are available.

Straw supported by rabbit wire can also be used to build a sediment fence.

Set out the steel posts in the same way as for the fabric fence.

Roll out the rabbit fencing to slightly overlap at both ends, then fold it around end posts and fix firmly with fencing staples or tie wire.

Lay biscuits of straw against the rabbit mesh on the up slope side and fix with wire pins.

Use rice straw if available as it is free of weeds and stock find it unpalatable.

Example of a sediment fence built from straw that is supported by rabbit wire. Straw is laid against the rabbit mesh on the up-slope side. The fence is curved to allow water runoff to flow around the sides of the fence.

Rabbit wire without straw can also be used for courser barriers that will collect the biggest debris further up the slope.

Repeat any of these processes to erect further fences.

Whichever method you use, ensure that water flows around the first fence, then runs into the second and does the same for any subsequent fences.

Check all fences after the first rain to make sure the structures are still secure and there are no gaps.

Leave the fences in place until ground cover is established again, when they should be removed so as not to become a hazard in long grass.

Page last updated: 23 Nov 2021