The catchment area of the Lake Macquarie waterway to the Pacific Ocean is approximately 700 square kilometres, of which approximately 95% is within the City of Lake Macquarie. Of this approximately 110 square kilometres (16%) is the area of the lake. The lake is approximately 22 kilometres in length and up to 8 kilometres wide, with a perimeter of approximately 170 kilometres. The lake is surrounded by extensive rural and residential developments that value its scenic quality as well as its commercial and recreational value. The entrance to the Pacific Ocean is by the narrow and shallow 4 kilometre long Swansea Channel. The lake level is normally at 0.1 mAHD and average tidal fluctuations are ± 0.05m. Elevated ocean levels (high tides and storm surge) as well as intense rainfall over the catchment cause the lake level to rise. The highest recorded level is 1.25 mAHD in 1949, with 1.05 mAHD reached in the June 2007 long weekend storm/flood event, and 1.00 mAHD recorded in February 1990. The June 2007 long weekend storm/flood event and the February 1990 event were of the order of a 30 year ARI design event. Flooding causes significant hardship (tangible and intangible damages) to the community and for this reason Lake Macquarie City Council has undertaken a program of studies to manage flood risks. The present study was initiated by Lake Macquarie City Council to research and to update the 1998 Flood Study, to incorporate predicted impacts of climate change and catchment modifications. The primary objective of the Study is to assess scenarios that would arise due to climate change, such as an increase in rainfall and sea level rise. The study builds on the 1998 Lake Macquarie Flood Study - Parts 1 and 2, which defined design flood levels for the foreshore area. In addition, this present study incorporates modelling of the June 2007 long weekend storm/flood event which occurred subsequent to publication of the 1998 Flood Study. The outcomes of this Study provide an indication of the impacts likely to occur on lake levels due to flooding and climate change. This report does not consider the effects of flooding due to a tsunami.