All reasonable efforts should be taken to program construction activities during those periods when flood flows and fish passage is not likely to occur. As a minimum requirement, avoid fish migrations and breeding periods as advised by the local fisheries department/authority.
The old crossing should be removed in its entirety where it acts as a barrier to fish passage.
Temporary sidetrack crossings should be constructed from clean fill (free of fines) using pipe or box culvert cells to carry flows, or a temporary bridge structure.
All temporary works, flow diversion barriers and instream sediment control barriers must be removed as soon as practicable and in a manner that does not promote future channel erosion.
The construction site should be left in a condition that actively promotes native revegetation and
shading of habitat pools.
Monitoring is highly recommended during both pre and post construction (especially on Class 1 and 2 streams in Table 1) to ensure that the new waterway crossing design is successful in achieving the desired flow velocities and fish passage outcomes. The monitoring program should be designed in consultation with fisheries scientists and the local fisheries department/authority.
Culverts and causeways need to be maintained for a variety of purposes, including:
to maintain the structure's required hydraulic capacity to prevent adverse property flooding and/or to maintain the desired flood immunity of the road way
to maintain fish passage
to remove debris
to remove sediment deposits
to repair bed or bank erosion resulting from the operation of the structure
Such maintenance activities have the potential to both improve and hinder fish passage. The removal of debris generally improves fish passage. In some cases the removal of sediment can adversely affect the development of desirable fish habitat within the "wet" cells, while in other cases it may be necessary to maintain the designated "wet" cell at a lower elevation to the "dry" cells.
Debris deflector walls and sediment training walls can be used to reduce the impacts of debris blockages and sediment deposits on fish and flood passage. Guidelines on the design of these walls are provided in Witheridge (2002).
Wherever possible, in-stream maintenance activities should be programmed for those times of the year that minimise overall environmental harm, giving appropriate consideration to anticipated critical periods of fish passage and seasonal high flows.
© Catchments & Creeks Pty Ltd
fish passage requirements for waterways crossings