Waterway barrier works

Bed 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 slow 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.

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.

Levee banks built across tributaries connecting floodplain wetlands to larger waterways. 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.

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.

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.

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

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.

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 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.

Maintenance or changes to existing unauthorised waterway barrier works include 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.

Retrofitting fishways to existing barriers can exacerbate fish passage issues if not designed and located appropriately.

Changes to existing authorised waterway barriers include any alterations that result in changes to an authorised waterway barrier work that have the potential to impact on fish passage and fish habitat, are considered a waterway barrier work and require development approval. 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.

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.

Waterway diversions or meander realignments proposed to facilitate adjacent development or minimise impacts of other waterway barrier works. These developments can seriously harm fish and their habitats if fish passage and fish-friendly structures are not considered during their design and construction.

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.

Recessed rock rib level with, or below, bed level (may aid in bed replenishment or stabilisation).

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.

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 change the characteristics 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, but does not change the characteristics of the low-flow channel (i.e. cause scouring of the low-flow channel banks or bed).

Bridge maintenance:

• encasing existing bridge piers, piles or platforms in concrete
• abutment revetment maintenance works do not extend into the waterway beyond the toe of the bank
• reinstating existing, or installing new, bed and bank scour protection, including the use of gabion bags, at or below the natural waterway bed or bank level, and does not change the characteristics of the low flow channel and:
• in purple, red, amber and green waterways, bed and bank scour protection does not extend for more than 20m upstream, or 20m downstream beyond the footprint of the bridge
• or
• in grey waterways, bed and bank scour protection does not extend more than 5m upstream, or 5m downstream beyond the footprint of the bridge.

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 therefore on fish movement, they are not waterway barrier works.

Bank revetment or other bank stabilisation works (both maintenance and new works) when they:

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

Maintenance of waterway crossings:

• de-silting and removing trash
• removing flood debris
• filling of scour erosion up to natural bed or bank level
• sealing cracks, repairs to head walls, wing walls and aprons
• replacing sealant in joints
• replacing or repairing baffles/roughening elements.

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 maintenance of approved fishways if the works match the approved fishway designs once constructed. If there are changes that do not meet the approved designs, the works will require development approval.

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.

Road resurfacing at waterway crossings if the repair thickness is the same, or comparable within 100mm to the original road surface thickness or deck level.

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

Temporary bunds or instream sediment control devices that are part of waterway maintenance may be waterway barrier works and will require development approval.