Rock chute

A rock chute is a relatively short, steep grade control structure that provides a stable transition from one bed gradient to a lower bed gradient through rock armouring. Rock chutes are typically either installed to:

• stabilise riverbed deepening processes (e.g. a knickpoint/erosion head).
• reduce the longitudinal bed gradient of a river by creating a backwater influence upstream of the rock chute and subsequently contributing to sediment deposition.

Rock chutes often address the symptoms of a larger problem in the catchment such as a change in the sediment or flow regime. The long-term goal should be to address these changes alongside providing sufficient local vegetation to improve the strength of the site.

Potential benefits from this intervention:

• Allows for rapid stabilisation of bed deepening processes (preventing knickpoints/erosion heads from propagating in an upstream direction).
• Can be successfully used to address site and reach based processes.
• Angular quarry rock allows for minor channel adjustments.

Potential negative implications from this intervention:

• High disturbance during construction including vegetation removal and heavy machinery within rivers.
• Rock chutes have the potential to alter sediment supply into downstream reaches and initiate sediment starvation (downstream progression of bed degradation).
• Rock chutes have the potential to restrict/prevent fish passage if this requirement is not taken into consideration during the design process.
• May not be conducive to recreational activities.
• Rock chutes are difficult to construct in small rivers.

Intervention considerations:

• Seek appropriate specialist advice and check legal obligations (e.g. permits).
• Rock chutes typically require specialist technical input to account for site and reach based physical processes, topography, and hydrologic and hydraulic characteristics.
• The disturbance and cost associated with a rock chute may not justify its use.
• Consider the potential implications associated with a reduction in sediment transport into downstream reaches.
• Consider if the rock chute needs to account for fish passage requirements.
• Determine if other infrastructure is threatened and whether it could more efficiently be moved rather than protected.
• Consider the design life required from the structural component and whether vegetation can establish adequately in this timeframe.
• Safety of employees including seasonal exposures (e.g. heat) and high risk areas (e.g. crocodile presence in waterways).

Additional information

Publications:

Department of Sustainability and Environment (DSE). 2007. Technical Guidelines for Waterway Management, Department of Sustainability and Environment, Victoria.

Keller, R.J. 2003. Guidelines for the design of rock chutes using CHUTE. Cooperative Research Centre for Catchment Hydrology, Melbourne.

Last updated: 14 December 2021