Alluvium was engaged by Dubbo City Council to develop a functional and detailed design for weir upgrade and fish passage at the South Dubbo Weir in Dubbo NSW. The weir I vital for Dubbo’s water supply, but had become undermined, and associated turbulence on the downstream side was a public hazard. Further it was a major barrier to fish migration in the Macquarie River.
The options assessment identified a rock ramp fishway as the preferred approach as it met the twin objectives of stabilising the existing weir and providing for fish passage past this historical barrier.
The rock ridge fishway presents an elegant solution to the fish passage challenge as it provides suitable conditions for fish to move upstream for the full range of flow conditions from low flows of 80 ML/d to drown out flows of 25,000 ML/d. The perennial issue of strategically locating the fishway entrance is made redundant by making the fishway entrance the full width of the River. We undertook extensive 2D modelling to refine the arrangement of the rock ramp and assess upstream and downstream implications across the full range of flow scenarios.