INTRODUCTION

St Georges Basin is a coastal lagoon within the Shoalhaven City Council area (Figure 1). The Basin has a surface area of approximately 37 square kilometres discharging through the Sussex Inlet Channel to the Pacific Ocean at Bherwerre Beach. The total catchment area to the Pacific Ocean is approximately 327 square kilometres. The Basin itself therefore represents approximately 11% of the total catchment. A number of properties surrounding the Basin and its tributaries are very low lying and flooding has caused damage in the past. Historical flood level data for the more recent significant flood events of February 1971 and June 1991 were provided by many residents as part of the St Georges Basin Flood Study (September 2001 - Reference 1). In the last 30 years the land usage around the Basin has undergone significant changes, from a predominantly rural community, to a community with significant areas of urbanisation. The town of Sussex Inlet in particular has undergone massive changes, mainly due to the development of the canal estates which commenced in 1971. There has been a significant increase in population and a heightened awareness of environmental issues. These changes have already affected the Basin and there is the potential for further changes to occur. In view of these factors it is necessary to define the existing flood problem and carefully manage future development on the floodplain.