Flood Study Overview, Flood Study Report, 12 technical volumes, 4 map book volumes, Engagement Outcomes Report

Hydrologic and hydraulic model input files

This report describes the hydraulic modelling for the first stage of a flood study of the Hawkesbury-Nepean Valley commissioned by the Water Board in 1987. The study is required in order to "determine the effects that various arrangements of major or future works for Warragamba Dam have on flooding in the valley" (Revised Brief for the Preparation of an E.I.S., Water Boards August 1987). Stage 1 required a simplified model to be developed, calibrated and used to provide a measure of the relative effects on flooding of options for such works. The model used is described in Section 2. Section 3 describes the calibration phase, in which three historical floods were used to adjust model parameters in order to match historical and modelled flood heights. The various options for Warragamba Dam flood protection works have an impact on the outflow hydrographs from the dam. Outflow hydrographs were determined for each option for five "design" floods and run through the calibrated hydraulic model. Peak flood heights were then tabulated and compared at three key locations In the valley. Section 4 describes the options while Section 5 discusses the modelling methods used to run these cases. The results are presented as a series of tables and graphs.

The Hawkesbury-Nepean River Flood Study (May 2024) provides high-resolution spatial and temporal data identifying areas in the Hawkesbury-Nepean Valley affected by flooding, including backwater inundation of tributaries, and assesses the potential impacts of climate change on flood behaviour. The study covers the 21,400km² catchment and the 190km river length from Bents Basin near Wallacia to Brooklyn, encompassing Local Government Areas such as Penrith, Hawkesbury, Blacktown, The Hills, Wollondilly, Liverpool, Hornsby, and Central Coast. This dataset includes outputs from state-of-the-art hydrologic and hydraulic modelling, offering detailed flood information on peak levels, depths, velocities, extents, and hazard classifications for events ranging from frequent floods to the probable maximum flood (PMF).

The Hawkesbury-Nepean River Flood Study (May 2024) provides high-resolution spatial and temporal data identifying areas in the Hawkesbury-Nepean Valley affected by flooding, including backwater inundation of tributaries, and assesses the potential impacts of climate change on flood behaviour. The study covers the 21,400km² catchment and the 190km river length from Bents Basin near Wallacia to Brooklyn, encompassing Local Government Areas such as Penrith, Hawkesbury, Blacktown, The Hills, Wollondilly, Liverpool, Hornsby, and Central Coast. The TUFLOW model input files provide the most up-to-date and reliable flood information for the Hawkesbury-Nepean River and should be used to inform all flood-related decision making from June 2024. Please contact tim.day@reconstruction.nsw.gov.au to receive a copy of this dataset.

The tool should be used in conjunction with the associated guide and with the assistance of the regional DCCEEW flood program representative. This tool has been updated December 2023. Note that the associated guideline has not been updated but is largely still relevant to the current version. Any additional queries may be directed to floodteam@environment.nsw.gov.au

Complete Report

Refer to this document for instructions on how to run the flood investigation brief tool

This document is based on the national guidance document. It is to be used in conjunction with the NSW Flood Investigation Brief Development Tool to help users make appropriate choices when using the tool.

Volume 1 - Hydrologic Models