The key objective of this Flood Study is to develop a suitable hydrologic/hydraulic model that can project flood and permanent inundation water levels in Lake Macquarie from rainfall, sea level rise and storm surge. These results will be used by Lake Macquarie City Council, in consultation with the community of Lake Macquarie City, to manage flood and permanent inundation risks to low lying land around the Lake Macquarie waterway. The key stages in the process are: Undertaken a comprehensive review of the 1998 Lake Macquarie Flood Study (Part 1 – Reference 1) and develop suitable hydrologic/hydraulic models to define flood behaviour over the full range of design events for existing catchment conditions, Use the hydrologic/hydraulic models to assess various climate change scenarios, including application of the NSW Government’s sea level rise benchmarks, Assess the potential increase in storm surge as a result of climate change and its impact on elevated ocean levels, Review the potential impact of climate change on the local wind/wave climate as this affects the extent of wave runup on the foreshore, Assess the hydraulic and hazard categories for existing and climate change conditions. This report details the results and findings of the above investigations. The key elements include: a summary of available historical flood related data, establishment of the hydrologic and hydraulic models, calibration of the hydrologic and hydraulic models, definition of the design flood behaviour for existing catchment conditions, sensitivity analysis of the design flood behaviour, assessment of the impacts of climate change on the still water and wave runup water levels re-definition of the flood extent and hydraulic and hazard categories mapping for existing and climate change conditions. A Flood Study is a technical document and not easily understood by the general public. A glossary of flood related terms is provided in Appendix A to assist. If more explanation of terms or a better understanding of the approach is required, type “NSW Government Floodplain Development Manual” into an internet search engine and you will be directed to the NSW Government web site which provides a copy of this manual and further explanation. Flood levels given in this report relate only to the water level with the lake itself. Design water levels in the creek systems entering the lake (Cockle Creek, Dora Creek etc.) will be higher than those shown for the lake.

The objectives of the Flood Study are to: • Identify all the flood-related data by searching all relevant data sources. • Determine the likely extent and nature of flooding and identify potential hydraulic controls by carrying out detailed site visits of the study area. • Define existing catchment condition flood behaviour for mainstream flooding in the catchment with due consideration to the impact of Lake Macquarie levels on flooding characteristics. • Define design flood levels, velocities and flow distributions for the catchment. • Define the extent of flooding for the 200 year, 100 year, 20 year, 10 year and 5 year ARI floods and Probable Maximum Flood (PMF) for the catchment. • Define Provisional Flood Hazard for the flood-affected areas. • Define the Hydraulic Categories for the flood-affected areas. Two numerical modelling tools were developed: • A hydrologic model to convert rainfall on the catchment into runoff. The hydrologic model combines rainfall information with local catchment characteristics to estimate runoff hydrographs. • A hydraulic model to convert runoff hydrographs into water levels and velocities throughout the study area. The model simulates the hydraulic behaviour of the water within the study area by accounting for flow in the major channels as well as all the potential overland flowpaths, which develop when the capacity of the channels is exceeded. It relies on boundary conditions, which include the runoff hydrographs produced by the hydrologic model and the appropriate downstream boundary level from Lake Macquarie.

FLOODPLAIN RISK MANAGEMENT STUDY The specific aims of this study are to:,

The overall objective of this study is to develop a Floodplain Risk Management Study where management issues are assessed, management options are investigated and recommendations are made. Thereafter a Floodplain Risk Management Plan detailing how flood prone land within the study area is to be managed can be completed. The objectives of the Flood Risk Management Study are to:,

Study Objectives Key objectives of this study are to:,

Flood Risk Management Study & Plan - Main report (Part 1 of 4) This Lake Macquarie Waterway Flood Risk Management Study and Plan constitutes a review of the second and third stage of the management process, namely the August 2000 Lake Macquarie Floodplain Management Study and the July 2001 Lake Macquarie Floodplain Management Plan. This review has been prepared by consultant WMAwater for Lake Macquarie City Council and was undertaken following a review of the 1998 Lake Macquarie Flood Study, to include the June 2007 long weekend storm/flood event and incorporation of the implications of climate change. The results of this Waterway Flood Risk Management Study and Plan Review will provide the basis for the future management of flood liable foreshores areas surrounding the Lake Macquarie waterway. The study concentrates on those areas of the foreshore within the boundaries of Lake Macquarie City Council, with no investigation of land within the Wyong local government area.

The main objective of this study (in two parts) has been to determine water levels in Brisbane Water for the full range of flood and ocean events that can occur due to the various natural physical processes, taking joint occurrence issues into account to some extent. The flooding behaviour can be influenced, either separately, or by a combination of, catchment rainfall runoff flooding, rainfall directly onto Brisbane Water, elevated ocean levels, local winds and, to a minor extent, the condition of the ocean entrance channel near Ettalong. The outcomes from this study include: -,

This Floodplain Risk Management Study investigates what can be done to reduce or manage the effects of flooding in the catchment. The Floodplain Risk Management Plan recommends a mix of strategies to manage the risks of flooding. Using the merits-based approach advocated in the NSW State Government’s Floodplain Development Manual (2005) and in consultation with the community, Council and state agency stakeholders, a number of potential options for the management of flooding were identified. These options included: • flood modification measures; • property modification measures; and • emergency response measures. An extensive list of options was assessed against a range of criteria (technical, economic, environmental and social). Hydraulic modelling of some of the flood modification options was undertaken to provide a comprehensive analysis of those options that would involve significant capital expenditure.

AIMS OF THE CURRENT STUDY In broad terms, the current Floodplain Risk Management Study has investigated what can be done to minimise the effects of flooding in the Haslams Creek catchment and recommended a strategy in the form of a draft Floodplain Risk Management Plan. Specific objectives of the study include: a review of the results from the 1999 Flood Study; consideration of the potential for culvert blockages and associated flood impacts; the implementation of a community consultation strategy, to ensure community input is obtained at key times throughout the study; a description and quantification of the flood problems in the Haslams Creek catchment including the likely cost of flooding to the local community; the identification and assessment of potential floodplain risk management measures to reduce the risks and hazards of flooding; a detailed review of issues relating to planning and development controls within the floodplain. Don Fox Planning Pty Ltd has prepared a document entitled Report on Planning Issues as part of this study. It is reproduced in Appendix A. Included in this report, is a proposed draft Development Control Plan (DCP) entitled “Managing Our Flood Risks”; the development of a recommended draft Floodplain Risk Management Plan for the Haslams Creek catchment that outlines the best measures to reduce flood damage, based on environmental, social, economic, financial and engineering considerations.

Floodplain Management Plan Report and figures. This Plan provides the basis for the future management of flood liable lands adjacent to the lake in the Lake Macquarie City Council area. The Plan was developed from the Lake Macquarie Flood Study (Part 1 - January 1998 and Part 2 - April 1998) and the Lake Macquarie Floodplain Management Study (August 2000). The Lake Macquarie Flood Study determined design flood levels for the 1%, 2% and 5% AEP floods and an Extreme flood event. It examined the still water level and also the effect of wave runup along the foreshore. The design events represent floods which have a certain probability of occurrence. The “1% AEP” or “1 in 100" flood has a 1 in 100 chance of being equalled or exceeded in any year. On a LONG TERM average it will happen once in every 100 years, but it is wrong to think it can only happen once in a century. Because floods are random events there is still a 1 in 100 chance of such a flood occurring next year no matter what happens this year.