Data contains * DEM * Flood Mapping * Hydraulic and Hazard Categories

St Marys (Byrnes Creek) Catchment Floodplain Risk Management Study and Plan Hydraulic model input files including TUFLOW model

MIKE-11

Complete report

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.

Hydraulic model results for report figures.

THE STUDY AREA The Upper Parramatta River catchment covers an area of 110 square kilometres and covers all land that drains to the Parramatta River upstream of its tidal limit at the Charles Street Weir, between the Barry Wilde Bridge (Wilde Avenue) and the Gasworks Bridge (Macarthur Street). Most of the catchment is urbanised and has a population of more than 230,000. However, there are significant areas of urban bushland, generally located along the major watercourses. A map of the study area is presented as Figure 1.1. The Upper Parramatta River has a number of tributaries that flow into it within the study area. The two largest tributaries are Toongabbie Creek and Darling Mills Creek. Other tributaries include the following: Brickfield Creek; Domain Creek; Finlaysons Creek; Coopers Creek; Pendle Creek (also known as Pendle Hill Creek); Greystanes Creek (also known as Girraween Creek); Grantham Creek; Blacktown Creek; Lalor Creek; Quarry Creek; The Quarry Branch (also known as Northmead Gully); Excelsior Creek; Blue Gum Creek; Rifle Range Creek; Hunts Creek. The Upper Parramatta River catchment includes parts of the following four local government areas (LGAs): Shire of Baulkham Hills — including the suburbs of Oatlands, Carlingford, North Rocks, Northmead, North Parramatta, West Pennant Hills, Castle Hill and Baulkham Hills; City of Blacktown — including the suburbs of Toongabbie, Seven Hills, Prospect, Blacktown, Lalor Park and Kings Langley; City of Holroyd — including the suburbs of Westmead, Wentworthville, South Wentworthville, Greystanes, Pendle Hill, Girraween, Prospect, Toongabbie and Merrylands West; City of Parramatta — including the suburbs of Parramatta, North Parramatta, Westmead, Northmead, Wentworthville, Toongabbie, Old Toongabbie and Winston Hills. OBJECTIVES OF THIS STUDY The primary objective of the current Upper Parramatta River Floodplain Risk Management Study and Plan is to bring together, and place in appropriate context, all past, current and proposed future activities related to the reduction of flood risk in the catchment. In broad terms, the current study has investigated what can be done to minimise the effects of flooding in the Upper Parramatta River catchment and recommended a strategy in the form of a Floodplain Risk Management Plan. As mentioned above, despite the expenditure of more than $35 million on flood mitigation works and measures since 1989, none of the four councils within the area of the Trust have adopted a formal Floodplain Risk Management Plan as required by the New South Wales (NSW) Government’s Flood Prone Land Policy. This study and plan constitute key components of the NSW Government’s floodplain risk management process as outlined in the Floodplain Management Manual (NSW Government, 2001) (see Section 1.4). Some of the objectives of the study include: briefly outlining the hydrological and hydraulic modelling activities that have been undertaken for the catchment to date; briefly reviewing the past, current and future flood-related activities of the Trust and the four constituent Councils; reviewing, in detail, issues relating to planning and development controls within the catchment’s floodplains; identifying additional floodplain risk management measures that particularly relate to community awareness about flooding, the release of flood-related information to the community, flood warning and emergency management; developing a mutually agreeable Floodplain Risk Management Plan for the Upper Parramatta River catchment that outlines the best measures to reduce flood damage, based on environmental, social, economic, financial and engineering considerations. Report The structure of this report is as follows: Chapter 2 summarises the flood problems, together with the behaviour and impacts of flooding in the Upper Parramatta River catchment. Chapter 2 also discusses the modelling of flood flows and flood levels in the catchment; Chapter 3 provides an overview of the previous

Hawthorne Canal Flood Study - Hydraulic Model Inputs (TUFLOW)

Volume 1- Main report; Volume 2- Planning

Hydraulic Model Inputs (TUFLOW)