In view of the increasing catchment development and the need to accurately define the flood problem, Lake Macquarie City Council engaged Webb, McKeown & Associates, to undertake a Flood Study. The primary objectives of this Flood Study are: • to define the flood behaviour of the North Creek catchment by producing information on flood levels, velocities and flows for a range of design flood events under existing catchment and floodplain conditions, • to assess the hydraulic categories and undertake provisional flood hazard mapping, • to assess the extent of the flood problem by undertaking a damages assessment, • to formulate suitable hydrologic/hydraulic models that can be used in a subsequent Floodplain Risk Management Study to assess various floodplain management measures, including the effects of further development. This report details the results and findings of the Flood Study investigations. The key elements include: • a summary of available data, • reasons for the choice of hydrologic and hydraulic models, • calibration of these models, • establishment of design flood behaviour, • flood damages assessment. The Flood Study does not consider flooding from local drainage which may result from inadequate urban drainage provisions.

This study investigates the hydraulic effectiveness of the current levee, assess the need for future improvements and also attempt to establish the flood overtopping levels of the levee, for the benefit of emergency services.

Wingecarribee Shire Council engaged Catchment Simulations Solutions to prepare a Flood Study for the Nattai River catchment. The extent of the catchment is shown in Figure 1 in report (refer Flood Study: Volume 2). The objectives of the Nattai River Catchment Flood Study are:,

The Wollombi Flood Study Review and Model Upgrade completed in 2010 represents the initial stage in the floodplain management process and establishes the basis for the current floodplain risk management study. The objectives of the Wollombi Floodplain Risk Management Study are to:  Identify and assess measures for the mitigation of existing flood risk;  Identify and assess planning and development controls to reduce future flood risks; and  Present a recommended floodplain management plan that outlines the best possible measures to reduce flood damages in the Wollombi locality. This report documents the Floodplain Risk Management Study and presents a recommended Floodplain Risk Management Plan for the Wollombi Village.

Study Objectives Key objectives of this study are to:,

Objectives The objective of this Study is to define the nature of the existing flood behaviour in the Burradoo BU2 catchment. To achieve the objective, the following tasks were undertaken:,

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:,

The objective of the study was to assess the impacts of climate change on the baseline 1% AEP flood condition within the Williamtown / Salt Ash Flood Study area. Central to this was the development of a new two-dimensional hydraulic model of the study area, in order that the impacts could be properly assessed. In completing the flood study review, the following activities were undertaken: • Review of relevant studies regarding flood conditions and climate change impacts within Port Stephens; • Site inspection to confirm the presence and configuration of key hydraulic structures; • Merging of the existing Williamtown / Salt Ash Flood Study and Williams River Flood Study modelled to produce a composite model capable of properly assessing the impact of climate change in the study area; • Updating of model topography with available LiDAR survey data; • Calibration of 1% AEP design event flood levels with the 4.84m AHD level from the Flood Frequency Analysis at Raymond Terrace; • Prediction of design flood conditions in the catchment using the developed model; and • Production of design flood mapping series. The climate change scenarios that were considered were combinations of 2050 and 2100 sea level rise conditions with baseline, +10% and +30% flood flows. A sea level rise of 0.4m by 2050, results in around a 0.2m increase to the 1% AEP flood level in Fullerton Cove. A sea level rise of 0.9m by 2100, results in around a 0.6m increase to the 1% AEP flood level in Fullerton Cove. For the 1% AEP event peak flood levels in Fullerton Cove increase by around 0.1m and 0.3m for the 10% and 30% flow increases respectively. The dominant flooding mechanism (in terms of peak design water levels) for the Williamtown / Salt Ash locality is mainstream Hunter River flooding. Under these conditions, Hunter River flooding results in Fullerton Cove filling and discharging into the Tilligerry Creek floodplain, under crossdrainage structures and through overtopping of Nelson Bay Road. The baseline flood level within the Tilligerry Creek floodplain is increased from 1.2m AHD to 2.6m AHD, under the worst case climate change scenario. The flood levels along Windeyers Creek are driven by flow conditions in the Hunter River. Hunter River flood water provides a backwater influence in Windeyers Creek, which fills the storage area to the east of the Pacific Highway. The total volume of water flowing from the Hunter River along Windeyers Creek determines the flood level reached in the storage area. A higher flood level in the Hunter River will result in a higher flood level in the storage area. At this location, the sea level rise scenarios have little impact on peak flood levels. There is only a small difference between flood levels for the baseline condition and the 2100 scenario. However, the increased flood flow scenarios do have a significant impact, with peak flood levels increasing by around 0.2m and 0.6m for the 10% and 30% flow increases respectively. The baseline flood level at this location is increased from 4.4m AHD to 5.2m AHD, under the worst case climate change scenario. The flood study review will form the basis for the subsequent floodplain risk management activities, being the next stage of the floodplain management process.

The Flood Study had three main components:,

The Raymond Terrace Flood Study has been prepared for Port Stephens Council (Council) to define the existing flood behaviour in the western Raymond Terrace catchments and establish the basis for subsequent floodplain management activities. The study will also assist Council in considering future upgrades to the drainage network and flood relief pump capacity to the Hunter River. This project has been conducted under the State Assisted Floodplain Management Program and received State financial support.