Big Al's Brook Realignment 2020-2026

The realignment of Big Al’s Brook, delivered as part of the M1 Pacific Motorway upgrade at the Gateway Motorway offramp in Underwood, demonstrates how integrated road design can enhance freshwater habitat and ecological resilience. To meet WWBW approval conditions, a 350‑metre reach of this Bulimba Creek tributary was reconstructed to include large refuge ponds with stepped sandstone block walls and vegetated banks, linked by run habitats designed to support fish passage and habitat complexity. Post‑construction monitoring by AFPS has recorded 83 fish from nine species (five native, four exotic) across the five ponds, with most individuals closely associated with instream vegetation such as submerged aquatic weeds and fringing or emergent plants. The sandstone block walls have also proven highly productive habitat, supporting dense populations of shrimp and Macrobrachium spp., and providing shelter for eels within wall voids. A turtle observed in one of the ponds further highlights the diversity supported by the new alignment.