In 1946, the Cooks River Improvement Act was passed, its primary aim being to control flows and prevent degradation of the banks. It gave control of the lower reaches of Cooks River (from Tempe to Canterbury Road) to the NSW Public Works Department for flood mitigation and river diversion works. The river was dredged, “swamps” were reclaimed, and the banks of the lower river were strengthened with iron sheet piling. These works reduced dry weather flow, but, conversely, during wet weather, they caused major flood damage. “The solutions chosen for the river’s problems were engineering ones which had the effect of providing a more efficient stormwater drain for the urbanised Cooks River Valley”. Between 1947 and 1955, the Alexandra Canal and lower reaches of the river were diverted 1.6 kilometres west of the natural outlet to allow for the reclamation of the large mangrove and saltmarsh basin at the mouth of Cooks River to enlarge Sydney Airport. This area had been relatively isolated from development, and the tidal flats “were the summer home of great numbers of migrating waders, from their far northern breeding grounds”. The works “embraced old works and landmarks closely associated with the early history of Sydney’s water supply and sewerage, including the pump-house and adjacent supply ponds for the Botany Swamps water supply, and the sites of the one-time Botany and Rockdale sewage farms”.

(Source: http://www.canterbury.nsw.gov.au/resources/documents/CRFWG-intstrat-2008.pdf)