Under the ACT Planning Strategy 2018, the Western Edge Investigation Area (WEIA) was classified as an area for potential future urban growth. As a part of several concurrent studies, Alluvium was engaged to identify and describe the water-related values of the WEIA (ecological, social and cultural), catchment management issues relevant to the area, and potential constraints and opportunities arising from future development with respect to water quality, hydrology and geomorphology.

One of the key findings of this investigation was that an area’s urban development can significantly increases flows entering the receiving catchments. With conventional drainage infrastructure, development would broadly lead to the following increases in nutrient loads across all WEIA subcatchments:

  • Tenfold increase in suspended solids (TSS)
  • 5-6 times increase in total phosphorous (TP), and
  • 3-4 times increase in total nitrogen (TN).

Alluvium were engaged to investigate the area and provide guidance on the planned development that would minimise the environmental and ecological impact.

We used MUSIC modelling, which predicted that even if development targets for stormwater treatment were met, export loads of TSS, TP and TN would all increase significantly.

Taking these findings into account, along with the hydrological and water related constraints and opportunities, our final report identified parts of the WEIA with the greatest potential for urban settlement, stormwater management and environmental offset zones, Designated/Special Purpose Zones, and Hills, Ridges and Buffer zones.

The findings from this study, together with information from other studies, will assist the ACT Government in planning for the WEIA, consistent with the ACT Planning Strategy, and to develop sustainable land use management principles relating to the rate, scale and location of any land use changes within the WEIA.