Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Kyogle weir a cost effective rock-ramp fishway design (#131)

Matt Sorenson 1 , Matthew Gordos 2 , Graham Kennett 1 , John Gan 3 , Luigi Molinari 3
  1. Kyogle Council, Kyogle, NSW, Australia
  2. Department of Primary Industries – Fisheries, NSW Government, Wollongbar, NSW, Australia
  3. Public Works Advisory | Department of Finance, Services and Innovation, NSW Government, Lismore, NSW, Australia

Kyogle Weir was a 3m high drop-board weir structure that limited fish migration to the upper Richmond catchment for 95% of river flows.  As such, Kyogle Weir was one of the highest priority barriers to migrating fish in coastal NSW.

The innovative full width V-shaped fishway design, installed as part of this project, allows fish to ascend the now 2m high headloss drop via 23 incremental rises of 100mm over a 50m distance, opening up over 300km of waterways in the upper Richmond sub-catchments.

The use of the V-shape creates a high flow central region where large debris can pass through freely, and quiet zones on the fringe that fish can use to ascend the structure. Accordingly, this enables fish migration, whilst reducing accumulation of debris on the fishway, thereby reducing ongoing maintenance costs.

Being a solid structure made from precast concrete, rock and steel plates, headlosses between baffles were able to be accurately set, construction time in-stream was minimised and the ongoing maintenance of the fishway (as compared to other fishways) is significantly reduced. Furthermore, the durability of the fishway was able to be demonstrated shortly after construction, with the structure withstanding an extreme flood event produced by ex-tropical cyclone Debbie, resulting in limited rock movement and no effect on headloss.

Through this project, this design has now been shown to be an efficient and durable concept which is planned to be rolled out across NSW as the preferred design for low-head (<2m), 'natural-like' fishways. The specific design and construction techniques utilised for this project resulted in a fishway that only cost $0.65 million per vertical meter, almost half the cost of typically vertical slot fishway projects in Australia that generally cost over $1.0 million per vertical meter.

  1. Northern Rivers Catchment Action Plan 2013-2023: http://northcoast.lls.nsw.gov.au/__data/assets/pdf_file/0011/496829/NR_CAP_2013.pdf
  2. Eastern Freshwater Cod Recovery Plan May 2004: https://www.dpi.nsw.gov.au/fishing/threatened-species/conservation/what/recovery/efc