This report details the flood gauging operation undertaken on 30th April, 1988 and presents the data collected for the Georges River catchment, Sydney.

The Georges River catchment area is approximately 960 square kilometres and is shown in Figure 1.1. The main arm of the river begins its course near the Cataract Dam, and exits into Botany Bay. The main channel is joined throughout its course by minor streams and creeks. The Woronora River catchment also drains into the Georges River.

The catchment area comprises a large part of the south western urban area of the city of Sydney, and the floods that have occurred in the catchment have at times caused significant damage to property.

To rationalise future development of the area in the face of potential flood threats, various numerical and physical models have been developed by both the University of N.S.W. Water Research Laboratory, and the Public Works Department's Manly Hydraulics Laboratory. The success of the models in predicting the flooding characteristics of various flood events depend upon collecting specific flood data over a series of floods for model calibration and verification. To this end, all known information regarding previous floods has been documented (Ref. 1 and 4), but there is a need for more comprehensive flood data, especially for major floods.

Manly Hydraulics Laboratory (M.H.L.) was requested by the Department's Coast and Rivers (C&R) Branch to co-ordinate and undertake flood monitoring at various sites over the area which is being modelled. These monitoring sites appear in Figure 1.2. Previous reports (Ref. 1 and 4) detail the results of gauging of earlier floods undertaken in 1978, 1983 and 1986.

Flood gauging on the 30th April, 1988 was carried out by personnel from the Department's M.H.L. and C&R.

The general extent of the flooding 12 hours after the peak can be seen in Plates 1 4.

The current metering lines, flood gauge locations and automatic recorder locations from which data was collected are as follows: i) Current metering/gauge observations at:

1. East Hills Footbridge
2. Mountbatten Bridge
3. Lansdowne Bridge

ii) Automatic recorders located at:

1. Milperra Bridge
2. Cutler Road, Lansvale
3. Scrivener Street, Warwick Farm (* This recorder malfunctioned during the flood event.)
4. Liverpool Weir
5. Prospect Creek, Lansdowne