Background
Freshwater fish populations have collapsed internationally over the past 125 years. This is substantially due to the disruption of upstream fish passage by low (1 to 8m) barriers to millions of kilometres of formerly fish-accessible river reaches. Road crossings comprise the majority of these barriers. Heavily trafficked crossings can be very difficult to remediate due to disruption by construction activities or unsuitable river substrate.
Methods of remediating culverts where complete reconstruction of the road crossing is possible, or where the channel gradient is gentle, are well established (e.g. Witheridge, 2011). However, there are many road crossings where heritage, spatial or geotechnical issues make conventional fishways impossible or extremely expensive.
Peirson and Harris (2025) have recently published upstream fish passage methods with standard Tube Fishway designs for low barriers. The relatively narrow road-crossing conduits required by Tube Fishways mean that they may provide passage where other approaches are infeasible.
Methods
Using two design case studies (Marsden Street Weir at Parramatta, NSW and Audley Weir in the Royal National Park NSW) the potential for Tube Fishways to remediate upstream fish passage is illustrated. In both cases, these sites are subject to severe space constraints, significant heritage issues, flood overtopping, heavy debris loads and human or vehicular traffic loadings. Conventional approaches have proved difficult to implement.
Results
Methodology for Tube Fishway construction at both sites is presented including the following elements:
Conclusion
This paper illustrates practical Tube Fishway application for upstream fish passage at road crossings. The design, construction, maintenance and cost aspects of their implementation are presented.