Waterway barrier works

Bed level or low-level crossings, if not constructed properly, can hinder fish passage on low to medium flows due to head loss differences and increasing velocities.

Bridge crossings, abutments, piers or piles and other components within the waterway can reduce the cross-sectional area of the waterway.

Causeway crossings can hinder fish movement on low to medium flows due to head loss differences and increasing velocities. They often use fill or construction materials that are a barrier to fish passage.

Changes to existing authorised waterway barriers include any alterations to a barrier that is authorised for constructing or raising waterway barrier works under a self-assessable code, accepted development requirements or development approval that has the potential to impact on fish passage and fish habitat. For example:

• 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 fishway.

Culvert crossings reduce the cross-sectional area of a waterway through which water can flow, increasing velocities, causing turbulence and 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.

Dams and weirs designed to impound water, preventing or vastly reducing upstream and downstream fish movement.

Fences across a waterway have the potential to trap, injure and kill fish if fish passage is not considered as part of their design.

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.

Fishways (new or retrofitted) can exacerbate fish passage issues if not designed and located appropriately.

Levee banks built across tributaries connecting larger waterways to floodplain wetlands. The purpose of levee banks is to stop flood water or tidal water moving into floodplains or low-lying areas, where people live or farm. As such, levees cut off access from the main river system to floodplain wetlands, which are used by fish for feeding, breeding and as nursery grounds.

Litter booms can impede fish movement beneath the floating litter boom where lack of maintenance has resulted in a build-up of debris.

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.

Pile fields can reduce the cross-sectional area of the waterway and can exacerbate fish passage issues if not designed and located appropriately.

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 piped systems due to darkness, velocities or other reasons, and are likely to be more vulnerable to predation within, entering or exiting a pipe.

Revetment wall and abutment works have the potential to impede fish passage by narrowing waterways and increasing water velocities.

Riffle structures constructed across a waterway for infrastructure protection, erosion and sediment control or water quality improvement can act as a barrier in low flows.

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.

Silt curtains designed to stop the movement of silt and sediment can impede fish passage when fixed across a waterway.

Temporary waterway barriers may be constructed for a variety of reasons to support other works, but they can slow or stop fish movements at a critical stage of their spawning cycles or interrupt migratory patterns. For example:

• sediment control measures
• bunds
• coffer dams
• work platforms
• access tracks.

Tidal or flood gates designed to stop the flow of water in a particular direction, only allowing fish passage when the gate is open.

Trash racks, if fitted to culverts, can act as a barrier to fish movement if the mesh or grill aperture is inadequate or a lack of maintenance has resulted in a build-up of debris.

Waterway diversions or straightening proposed to facilitate adjacent development or minimise impacts of other waterway barrier works. Works within waterways associated with these types of developments can harm fish and their habitats if fish passage and fish-friendly structures are not considered during design and construction.

Works on existing unauthorised waterway barrier works include structural repairs on existing barriers that are not authorised for operational work for constructing or raising waterway barrier works under a self-assessable code, accepted development requirements or development approval. This type of work prolongs the life of the structure and hence the duration of the impact that it has on fish habitat and fish passage.

Aids to navigation, including beacons, buoys and port entry lights.

Bank revetment or other bank stabilisation works when they:

• fill minor erosion pockets to regularise the bank of the waterway, or
• are in waterways less than 50m wide at the main channel width and do not extend into the waterway beyond the toe of the bank, or
• are in waterways greater than 50m wide at the main channel width and do not extend beyond 10% of the width of the waterway (main channel width) and do not raise the bed level of the waterway above its natural profile.

Changes to chemistry or physical properties of water due to structures or activities. While these changes may significantly impact on the behaviour of fish and fish movement, they are not waterway barrier works.

Jetties, pontoons and boat ramps regardless of their size, construction material or location.

Levee banks when they are:

• built parallel to a waterway
• sit outside the main channel width.

Any levee that sits within the main channel width will require development approval.

This type of levee can significantly impact lateral fish movement, including to tributaries or wetlands that connect with a floodplain habitat.

New multi-span bridges:

• in all waterways, the abutments do not extend into the waterway beyond the high bank, and the abutment revetment works do not extend into the waterway beyond the toes of the banks
• in all waterways, bed scour protection is placed at, or below the natural bed level of the waterway, and does not alter the profile of the low-flow channel
• in purple, red, amber and green waterways, bed scour protection cannot extend more than 20m upstream, or 20m downstream beyond the footprint of the bridge
• in grey waterways, bed scour protection cannot extend more than 5m upstream, or 5m downstream beyond the footprint of the bridge
• in amber and green waterways, the pier/pile and/or pier/pile platform are completely outside the low-flow channel
• in purple, red and grey waterways, the pier/pile and/or pier/pile platform can be within the low-flow channel.

New single span bridges:

• the abutments do not extend into the waterway beyond the high bank
• the bank revetment works do not extend beyond the toe of the bank
• no scour protection is placed on the bed of the waterway upstream, downstream or under the structure.

Removal of existing waterway barriers where all components of the barrier within the waterway are removed in their entirety.

Removal of weeds (aquatic or terrestrial) if the characteristic of the low-flow channel is not impacted, and the banks of the waterway are stabilised to resist erosion.

Repair and replacement of existing waterway barrier works to reinstate the works to their design as authorised under a self-assessable code, accepted development requirements or development approval for constructing or raising waterway barrier works.

Re-snagging, placing large woody debris into a waterway for the purposes of fish habitat creation, bank stabilisation and/or the reinstatement of an eroded bank when they do not cause a bund, riffle or weir structure within the waterway.

Storm-water outlet construction and associated scour protection works, if they do not reduce the cross-sectional area of the waterway.

Works associated with existing waterway barriers:

• de-silting and removing trash
• removing flood debris
• filling of erosion scour up to natural bed or bank level
• sealing cracks
• replacing sealant in joints
• replacing or repairing baffles in accordance with original design specifications.

Works on braided waterway channels outside the major channel/s. Seek advice from planningassessment@dpi.qld.gov.au to confirm the major channel/s.