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Grass chutes

A grass chute is a relatively short, steep earthen channel arrangement that involves excavation works to reduce the slope (battering). The works usually occur at a head-cut or knickpoint feature associated with channel/floodplain deepening processes. The reduced slope chute improves bed slope stability, riverbank stability and creates more favourable conditions for vegetation establishment. Vegetation may comprise native and/or introduced species, however, native species are often preferred as introduced species risk becoming invasive weeds. A suitable vegetation composition may include grasses, rushes, reeds and/or shrubs.

Long section and cross-sectional diagram of a typical grass chute arrangement. Image by Queensland Government

Potential benefits from this intervention:

  • Allows for medium to long-term stabilisation of bed deepening processes (preventing knickpoints/erosion heads from propagating in an upstream direction in either a channel or floodplain), while minimising potential site disturbance and costs.

Potential negative implications from this intervention:

  • Battering disturbs soil and results in the bank being more vulnerable to erosion in the short-term, while the revegetation establishes. This may not only impact on bank stability but also water quality.
  • High disturbance during construction including vegetation removal and heavy machinery within rivers.
  • May be more prone to failure compared to other bed grade control management options including rock chutes and timber sleeper drop weirs.

Intervention considerations:

  • Seek appropriate specialist advice and check legal obligations (e.g. permits).
  • This technique generally has limited application and is most suitable for ephemeral systems or floodplain flow re-entry points where the grass chute will be subject to infrequent and short duration flow events.
  • Grass chutes typically require specialist technical input to account for site and reach based physical processes, topography and hydrologic and hydraulic characteristics.
  • Without vegetation establishment on the battered bank face, the site is unlikely to be successful in the long term.
  • Alternative/complementary forms of channel stability may be required (e.g. some rock armouring) to provide long term channel stability.
  • The disturbance and cost associated with battering may not justify physical intervention.
  • Safety of volunteers and employees including seasonal exposures (e.g. heat) and high risk areas (e.g. crocodile presence in waterways or areas with soil contaminant risks).

Last updated: 23 June 2022

This page should be cited as:

Department of Environment and Science, Queensland (2022) Grass chutes, WetlandInfo website, accessed 5 October 2022. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/management/rehabilitation/rehab-process/step-4/intervention-options/grass-chutes-mod.html

Queensland Government
WetlandInfo   —   Department of Environment and Science