Griffith CBD Catchment Overland Flow Flood Study

The flood study carried out for the Griffith CBD catchment identifies flood liable properties for a range of design floods and finds approximately 168 properties that are flood liable during the 1% AEP event.

The Griffith CBD and upstream areas have experienced flooding in the past. This has been attributed to the insufficient capacity of the existing pipe drainage system, the flat topography across much of the area and the impediment to overland flow paths posed by the Main Branch Canal and the Temora-Roto Railway Line that passes to the immediate north of the CBD. In recognition of these flood issues, Griffith City Council (Council) have appointed WMAwater to carry out an Overland Flow Flood Study for the Griffith CBD catchment under the guidance of Council’s Floodplain Risk Management Committee.

The main objective of this study is to:

• Define the overland flow flood behaviour within the Griffith CBD catchment over the full range of design flood events;
• Detail the number of properties at flood risk, extent of flood damage, and provide Council with the technical basis to prepare a Floodplain Risk Management Study & Plan;
• Prepare a modelling system suitable for use in the Floodplain Risk Management Study and Plan, for assessing flood mitigation works; and
• Provide Council with a modelling tool for the pit and pipe drainage system.

The study has established suitable hydrologic and hydraulic modelling tools, demonstrated their capacity to emulate local flood behaviour via calibration/validation (as data allows) and then applied these tools to establish the existing flood risk for a range of design flood event probabilities in conjunction with a range of event durations.

This study has assessed major overland flow flooding throughout the Griffith CBD catchment in general and in the commercial areas in particular, providing Council with a sound understanding of the full range of potential flood risks and enabling Council to determine an optimum mix of works and measures to manage these risks.