Rock ramp fishway

Rock ramp fishway – Key considerations

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• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

In addition to the general information for all fishway types, the following applies to rock ramp fishways.

Requirements for effective passage

A low gradient is essential for successful rock ramp fishways. It is also important to have high and low-flow slots between the ridge rocks[1].

Suitability and limitations

The irregular placement of rocks in the fishway provides a range of alternative water velocities and depths to cater for differing behaviour of fish and other aquatic species negotiating the barrier. The larger and stronger swimming fish use the deeper, higher water velocity sections, and the smaller and weaker swimming fish use the shallower, lower water velocity sections[3][4].

Rock ramp fishways are generally considered effective for the whole fish community, particularly juvenile diadromous and small bodied species (see monitoring section)[2].

This type of fishway has a reasonably high degree of redundancy (i.e. if partly blocked by debris, etc., will still function in rest of fishway), however, as with all fishways does require routine maintenance.

A rock supply is required relatively close to site as this is a major cost consideration and a range of rock sizes are required including a well-graded rock mix to secure ridge and wall rocks.

There are many rock ramp fishways across Queensland, mostly in the Burdekin, Fitzroy and Mackay-Whitsunday regions, but also the South East Queensland, Southern Gulf, Wet Tropics, Southern Queensland, Desert Channels, Cape York and Northern Gulf regions. Nearly all are constructed of rock (embedded by concrete), as opposed to prefabricated concrete blocks, and several operate in conjunction with a different type of fishway. For example, rock ramps with cone fishways (e.g. Seaforth and Jolimont creeks in the Mackay-Whitsunday region) and rock ramps with culverts (e.g. Kirknie Creek in the Burdekin region, Stoney Creek in the Fitzroy region and Leitchs Crossing on the South Pine River in South East Queensland), and a rock ramp with a mechanical and cone fishway on Cedar Grove in South East Queensland.

One limitation of rock ramp fishways on weirs and dams is that they normally do not allow for low headwater levels (i.e. levels below full supply of the storage).

References

1. ^ Jones, M, O'Connor, JP & Arthur Rylah Institute for Environmental Research (2017), Monitoring the performance of fishways and fish passage works. [online] Available at: https://nla.gov.au/nla.obj-664272102 [Accessed 1 March 2021].
2. ^ Moore, M, McCann, J & Power, T (2018), Greater-Brisbane-Fish-Barrier-Prioritisation-Report.pdf. [online] Available at: http://catchmentsolutions.com.au/files/2018/05/Greater-Brisbane-Fish-Barrier-Prioritisation-Report.pdf [Accessed 11 November 2020].
3. ^ O'Brien, T (1998), Fish passage on small instream structures, notes prepared for Department of Natural Resources and Environment Victoria.
4. ^ Thorncraft, G & Harris, JH (2000), Fish passage and fishways in New South Wales - a status report, Cooperative Research Centre for Freshwater Ecology, Albury, N.S.W..

Last updated: 10 May 2021