Flooding is a relatively infrequent occurrence in the Goulburn LGA and the impacts of flooding, when it occurs, are significant to the community. The earliest recorded flood was in 1870, and a number of other significant events were recorded in 1900, 1925, 1942, 1950 1952, 1959, 1961, 1974 and 1990. The 1961 event is reported to be the highest flood in recorded history on the Wollondilly River at Goulburn. Between May 1962 and June 1977, a stream gauging station was located on the Wollondilly River at Marsden Weir, allowing detailed information on flooding during this period. Although there have been no recent major flood events, flooding is a random phenomenon that can occur at any time. It is essential that the community, as a whole, take precautions against future events, be they minor or major.

In response to the impact of flooding from the Wollondilly River and Mulwaree Ponds on the Goulburn community, the Goulburn City Council has recognised the need to develop an integrated Floodplain Risk Management Plan to manage flood hazard in the community.

Following engagement by Council in 2001, SMEC Australia undertook a detailed Floodplain Risk Management Study and the preparation of a draft Floodplain Risk Management Plan, under the direction of the Floodplain Working Group (FWG), which includes members of the community. The Study and Plan have been prepared in accordance with the principles and guidelines in the NSW Flood Prone Land Policy and its attendant Manual.

Sections of the City of Goulburn are highly susceptible to damage and disruption from floodwaters from both the Wollondilly River and Mulwaree Chain of Ponds. The 1961 flood event is reported to be the highest flood in recorded history on the Wollondilly River at Goulburn. The Flood Study (1986) indicates that this event was greater than a 1% Annual Exceedance Probability (AEP) flood event (see Flood Study Figure 5.4, which is included as Figure 1.1 in this report). The most recent major flood occurred in 1974 and, while there have been other significant flows in both rivers, these have not resulted in significant flood damages.

The passage of time since a major flood and the lack of knowledge of the impacts of an extreme flood are major issues for floodplain management in Goulburn. Unlike many other major centres throughout the State, the residents of Goulburn are not “flood aware” and one major component of the Floodplain Risk Management Plan (FRMP) must be a detailed program to raise the level of community awareness.

In response to these flood hazards, and a desire to prepare a long-term management plan for the City, Goulburn City Council has determined to develop a FRMP for the City. This FRMP will be developed in accordance with the NSW Flood Prone Land Policy and the principles and guidelines in the Floodplain Management Manual 2001.

The first step in developing a FRMP is to carry out a flood study, to determine the nature and extent of flooding within the area for historical and potential future floods. This flood study was undertaken by the Water Resources Commission (now DLWC) in 1986. The second step in developing a FRMP is to undertake a Floodplain Risk Management Study and develop a Floodplain Risk Management Plan that addresses the existing, future and continuing flood hazards affecting Goulburn City. This report presents the draft Floodplain Risk Management Study and a draft Floodplain Risk Management Plan for the Goulburn LGA.