Erosion control solutions

Erosion takes many forms, so a range of techniques can be used to repair it and prevent it from happening again. Different solutions are used to fix gully, streambank and road erosion on farms and grazing land. They improve the condition of the land, increase production, and reduce fine sediment flowing into waterways and out to the Great Barrier Reef.

Download our Erosion Remediation Brochure.

ROCK CHUTES

Rock chutes are used to repair gully erosion.  They are short and steep and lined with quarry rock.

When to use them:

Rock chutes are effective in a number of situations. They stop gully erosion in catchment landscapes by controlling and slowing the water flowing over a gully head. This also prevents the headward/upward progression of erosion. Rock chutes are also used for over-steepened sections of waterway where there is high water flow and ongoing erosion. Chutes reduce the elevation while using natural waterway processes.

Things to consider:

  • A well-constructed engineered rock chute typically provides longer-term erosion control.
  • This is a higher-cost erosion control method, and the distance of the erosion site from from accessible quarry rock will further impact cost.

GULLY COMPLEX RESHAPING/CONTOURING

Gully complex reshaping creates smooth, gradual slopes that reduce runoff and ongoing erosion. Soil treatment and revegetation are essential parts of this technique.

When to use:

Reshaping is used on many forms of erosion gullies. It is particularly useful for stand-alone gullies caused by rain falling on steep, exposed areas with susceptible soils, i.e. where there is no catchment upstream delivering rainfall runoff to the gully. Reshaping creates smooth and gradual slopes with treated and covered soils.

Things to consider:

  • A relatively low-cost technique compared with other methods.
  • Some ongoing maintenance may be needed to ensure long-term success.
  • Capping the finished area with topsoil is essential for the regrowth of grasses and other vegetation to hold the soil in place.

BANK BATTERING AND REVEGETATION

Bank battering creates a flatter, more stable gradient for steep and eroding streambanks. It is sometimes combined with quarry rocks (well-graded and suitably sized), beginning at the toe of the bank and extending to a height based on the flow of water. Planting trees and grasses is also part of the process, to stabilise the bank batter in the short and long-term.

When to use:

Bank battering and revegetation is used – without rocks – when waterways have a lower flow or when there is a tighter budget. In high-flow waterways, rock toe protection is also needed. The type of soil can be a factor too. Looser soils such as sandy loams are more likely to erode and a waterway with a lower flow may still need rock protection.

Things to consider:

  • This is a higher-cost remediation control technique when rock is needed, and a lower cost technique when rock isn’t used.
  • Timing of the work: If a major flooding event happens too soon after construction, it could compromise the project. The rock needs to settle, and vegetation needs to establish itself.
  • Location: How far away is the nearest quarry and supply of trees for revegetation work?
  • Follow-up work is needed, from watering to weed control, so the trees can get established.

TIMBER PILE FIELDS

Timber pile fields slow down water to better protect eroding or at-risk stream banks. They are multiple rows of numerous timber piles, of a specified diameter, driven into the streambed and bank. Timber pile fields also trap sediment, helping to build the area up to support vegetation that can eventually replace the piles as the bank’s protection.

When to use

Timber pile fields can be used when bank protection is not the only desired outcome. Other outcomes may be improved or restored instream habitat and riverside vegetation.

Things to consider:

  • The stream’s sediment load: The higher the load deposition, the more likely it is that vegetation will establish and succeed the piles.
  • The availability of suitable timber e.g. size, durability and strength.
  • Ongoing maintenance is needed if woody vegetation does not occur naturally.
  • Timber pile fields might not be suitable in estuarine or tidal areas because of marine borers.

ZUNI BOWLS

Zuni bowls are used to repair gully erosion. They are a step fall followed by a plunge pool, lined with carefully selected and placed rocks.

When to use them:
Zuni bowls are effective in situations where a rock chute would be too large or expensive. They stop the upward progression of a gully head by stepping the water down through a rock-lined pour-over. The water is slowed further by the plunge pool at the base of the pour-over.  Zuni bowls are used for smaller sections of gully erosion, typically in relatively small and steep flow paths.

Things to consider:

  • The selection and placement of rock is critical to the function and design life of a Zuni bowl. It is strongly recommended to use a machinery operator trained in Zuni bowl construction.

WHOA-BOYS AND ROAD DRAINAGE MANAGEMENT

Whoa-boys are earth bunds/diversion banks constructed across tracks or roads. They need to be high enough to divert run-off water, and low enough for safe vehicle use. Approach and exit ramps are part of construction.

When to use

Use on existing tracks with signs of erosion or gullying, or in construction plans for new tracks.

Things to consider:

  • The slope of the track and the catchment up-slope. The steeper the track and the larger the catchment, the more whoa-boys should be constructed at regular intervals.
  • Some ongoing maintenance is needed so whoa boys remain intact after rainfall events.
  • A relatively low-cost technique that can be undertaken by landholders, ideally with some training in whoa-boy placement and construction.

Rock Chute - before and after

Before and after photos gully erosion solution - rock chute

Gully complex reshaping - before and after

Gully complex reshaping - before and after

Bank Battering - before and after

Before and after photos of erosion control solution - bank battering

Timber Pile Fields - before and after (different locations)

Before and after images of gully erosion solution - timber pile fields

Zuni Bowl - before and after (different locations)

Before and after photos erosion control solution - zuni bowl

Completed Whoa-Boy

Erosion solution - whoa boy

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