One of Australia’s most significant infrastructure projects in decades, the Western Sydney Airport (WSA) will be an international and domestic airport with two runways, a terminal and airport facilities at the ultimate development stage. The WSA site has a total catchment area of 1400ha and is situated in the upstream reaches of Badgerys Creek. The proposed WSA trunk drainage network consists of approximately 48km of underground pipe network, 56km of open channels, 8 detention and 10 bioretention basins. Adding to the design complexity, the detailed design of the drainage network considered four milestone development stages concurrently.
This presentation outlines the stormwater management strategy of the WSA site and the design challenges to meet the specific airport operational requirements. Due to the significant change of the catchment characteristics throughout the 4 development stages, stormwater quality and quantity control requirements were a key target for the design. Other critical criteria for the design included maximum ponding duration and no supercritical flow conditions within the open channels. These were addressed through detailed DRAINS software modelling of storm events from the 4EY to the 1% AEP. The modelling challenges and learnings experienced in applying the ensemble of ARR 2019 temporal patterns are discussed. This includes the approaches used to resolve model instabilities associated with DRAINS modelling of the complex network of open channels, storages, headwalls, underground pipe network, diversion weirs and detention basins with associated inlet/outlet structures. The other modelling challenges were the building of large MUSIC models and incorporating the complex drainage network in the model.