The Rushcutters Bay catchment between Sydney Harbour and Oxford Street (Figure 1) is located primarily within the Woollahra Municipal Council Local Government Area (LGA). A small part is located within the City of Sydney LGA. The catchment drains the suburbs of Paddington, Rushcutters Bay and parts of Darlinghurst, Edgecliff and Woollahra.

Flooding problems have been experienced at a number of locations within the catchment during periods of heavy rainfall. Woollahra Municipal Council has undertaken to address this issue by preparing a comprehensive Flood Study covering both the upper and lower parts of the catchments.

The upper section comprises a pipe and overland flow system whilst the lower section comprises an open channel section through the White City tennis complex.

The drainage systems within the upper catchment comprises a network of underground pipes that were largely installed by Woollahra Municipal Council in the 1930's. The open channel section and larger pipe systems were installed by Sydney Water.

The land usage within the study area is predominantly urban residential development, comprising a mixture of pre-1900 terrace buildings and new brick buildings including a number of medium density developments. The non-residential development in the catchment includes several schools, parks (including Trumper Park and the White City tennis complex), churches and community buildings. There are no significant industrial developments and few major commercial developments.

The area drains into Sydney Harbour at Rushcutters Bay via the Sydney Water open channel, which generally runs in a north-westerly direction. The channel floodplain is largely contained within a series of parks and open space areas. Upstream of Glenmore Road the main channel is covered through Trumper Park up to Jersey Road and beyond.

Flood Problem Areas: The study indicated that floodwaters cross Trumper Park and the White City tennis complex in 5 year ARI and greater events. The yards of many private properties adjoining the open channel would also be inundated. In the upper parts of the catchment floodwaters would cross roads and enter private properties.

Outcomes: The main outcomes were as follows:

• full documentation of the methodology and results,
• preparation of flood contour, hazard and extent maps for the open channel section of the Rushcutters Bay catchment and upstream to Hampden Street,
• identification of peak overland flows and pipe capacities in the piped and overland flow section of the catchment,
• a modelling platform that will form the basis for a subsequent Floodplain Risk Management Study and Plan.

One outcome from the study was to highlight the importance of collecting and maintaining a database of historical rainfall and flood height data. Whilst both Woollahra Municipal Council and Sydney Water have some flooding records, it is vital that flood height data from any future events be recorded (photographed) within say 24 hours of the event. In the upper catchment the magnitude and direction of flow paths should also be accurately recorded.