What is a waterway barrier work?
Free movement along waterways, into other types of wetlands and onto floodplains is an essential requirement for the survival and productivity of many fish species. Many species must move into different habitats for breeding or rearing of young, or to access critical habitats for food and protection.
Movement occurs within and between inland rivers and creeks and along coastal streams throughout adult, juvenile and larval stages. Some fish move between fresh and saltwater for access to feeding and breeding habitats. Some species migrate large distances through marine, estuarine, palustrine, lacustrine and riverine environments.
Waterway barrier works
The meaning of waterway barrier works is provided in the schedule dictionary of the Fisheries Act 1994 and is defined as a dam, weir or other barrier across a waterway if the barrier limits fish stock access and movement along a waterway. They can be permanent or temporary structures.
Prior to the regulation of waterway barrier works, many structures such as dams, weirs, floodgates and culverts were built on waterways in Queensland without consideration of fish passage.
Other waterways have been filled with soil or other materials, resulting in fragmented fish habitats in some locations. In many cases, fish are unable to move into waters upstream or downstream of these barriers. This loss of access to habitat has caused a decline in distribution of native fish populations, including species of commercial, recreational and traditional importance such as barramundi, mullet and Australian bass.
In Australia, declines of inland species such as Murray cod, freshwater catfish and silver perch are thought to be largely due to the impacts of barriers to fish movement.
Waterway barrier works examples
Waterway barriers can include:
- dams and weirs – designed to impound water, preventing or vastly reducing upstream and downstream fish movement
- bridge crossings – abutments, piers or piles and other components within the waterway can reduce the cross-sectional area of the waterway
- culvert crossings – generally reduce the cross-sectional area of the waterway through which water can flow, increasing velocities, causing turbulence and creating darkness. The extent of the impact may depend on the size of the culvert and the extent to which the culvert or array of culverts is proposed to span the waterway
- bed level crossings – if not constructed properly, can hinder fish passage on low to medium flows due to head loss differences and increasing velocities
- causeway crossings – can hinder fish passage on low to medium flows due to head loss differences and increasing velocities. They incorporate fill or construction materials, that are a physical barrier to fish passage.
- tidal or flood gates – designed to stop the flow of water in a particular direction, only allowing fish passage when the gate is open
- fences across a waterway – have the potential to trap, injure and kill fish if not designed with fish passage considerations
- levee banks across a waterway – levees built across tributaries connecting floodplain wetlands to larger waterways are waterway barriers. The main reason for the construction of levee banks is to stop flood water or tidal water moving into floodplains or low-lying areas, which are often the site of human habitation or agriculture. In doing so levees cut off access from the main river system to floodplain wetlands, which are used by fish for feeding, breeding and as nursery grounds
- silt curtains – designed to stop the movement of silt and sediment; however, can impede fish passage when fixed across a waterway
- netting and screens – installed across waterways to prevent intrusion of predators such as crocodiles and sharks, they may prevent movement of fish depending on mesh size and if lack of maintenance has resulted in a build-up of debris
- litter booms – can impede fish movement beneath the floating litter boom where lack of maintenance has resulted in a build-up of debris
- trash racks – if fitted to culverts can act as a barrier to fish movement if mesh or grill aperture is inadequate or if lack of maintenance has resulted in a build-up of debris
- riffle structures – if constructed across a waterway for infrastructure protection, erosion and sediment control or water quality improvement, they can act as a barrier in low flows
- revetment wall and abutment works – have the potential to impede fish passage by narrowing waterways and increasing water velocities
- rock and grass chutes – constructed to prevent the progress of head-cut erosion upstream; however, can exacerbate fish passage issues if not designed and located appropriately
- retrofitting fish ways to existing barriers – can exacerbate fish passage issues if not designed and located appropriately
- filling within waterways – removes habitat available to fish and can fragment upstream and downstream fish habitats by removing the ability for fish to access previously connected fish habitats
- piping waterways – piping waterways removes the ability for fish to access pre-existing habitat and/or the habitat condition is impacted and cannot be restored. Fish may not enter the piped system due to darkness, velocities or other reasons, and are likely to be more vulnerable to predation within, entering or exiting a pipe
- waterway diversions or meander realignments – generally proposed to facilitate adjacent development or minimise impacts of other waterway barrier works. Development of such nature can greatly impact fish populations if designed and constructed without fish passage and habitat considerations
- maintenance or changes to existing unauthorised waterway barrier works – structural repairs on existing barriers that are not authorised under legislation for constructing or raising of waterway barrier works prolongs the life of the structure and hence the duration of the impact that it has on fish habitat and fish passage
- significant changes to existing authorised waterway barriers – alterations that result in changes to an authorised waterway barrier work have the potential to impact on fish passage and fish habitat, for example, by reducing the cross-sectional area of the waterway, increasing velocities and causing turbulence, reducing the frequency of drown-out of the structure or impacting the operation of a fish way
- temporary waterway barriers – constructed for a variety of reasons to facilitate other works; however, may impede important fish movements at a critical stage of their spawning cycles or interrupt other migratory patterns
- cumulative waterway barriers – multiple waterway barriers accumulating in series within a waterway can amplify impacts on fish passage within that waterway and the other fish habitats it connects; in some cases, a series of barriers can become an insurmountable obstacle course for fish to pass. For example, if a series of barriers reduces the frequency of upstream and downstream fish passage at individual barriers and/or creates delays for fish to move at each barrier encountered, this can, over time, change or isolate the geographic range of fish populations and their productivity and sustainability
Some structures proposed to be located within waterways do not have to be a barrier to fish passage if they can be designed accordingly. This would avoid the requirement for development approval for constructing or raising waterway barrier works and the fees associated with the application process.
For more information on which structures are not considered to be waterway barriers refer to What is not a waterway barrier work?
To construct or raise waterway barrier works within a waterway, the works must comply with accepted development requirements or a development application under the Planning Act 2016 needs to be lodged.