Understanding and Managing Flood Risk in Perth Project

 

About the project

The previous information in relation to catchment hydrology for the Swan and Helena Rivers was dated and did not reflect current industry standards or consider the impact of observed changes in catchment rainfall since the 1970s. Current floodplain mapping is based on hydrologic assessments undertaken in 1983. As a result, the available floodplain mapping may not be suitable to support land use planning and development decision-making and flood emergency response.

The four stage regional project titled 'Understanding and Managing Flood Risk in Perth' is a flood study for the Swan and Helena Rivers to assess risk, collate data, prepare mapping and develop floodplain strategy and community awareness in relation to managing flood risk.

A flood study has three main technical components:

  • Hydrology -- how much water will flood an area?
  • Hydraulics -- where will the water go and what areas are likely to be impacted?
  • Damage assessment -- what damage will the water do and what are the risks?

The staged project will build resilience in Perth's Eastern Region in relation to flood risk by providing the information and tools needed to improve the ability of emergency response agencies and the community to prepare for and take appropriate actions during major flood events.

Stage One - Hydrology

The EMRC was successful in receiving $100,000 funding from the Western Australian State Emergency Management Committee to implement the 'Understanding and Managing Flood Risk in Perth's Eastern Region' Stage One project. The project was funded under the Commonwealth Government's National Partnership Agreement on Natural Disaster Resilience as part of the Natural Disaster Resilience Program and was a collaboration between the EMRC, Department of Water, and the Cities of Bayswater, Belmont and Swan.

Stage One of the project undertook a hydrology assessment for the mainstream Swan River from Perth Water upstream to Walyunga National Park and the Helena River from its outlet to the Swan River to the Helena River Pipehead Dam. Riverine flooding, caused by heavy or prolonged catchment rainfall events, is the dominant mechanism of flooding within the study area. Estuarine flooding, a form of major storm or tidal surges, is the dominant flooding mechanism downstream of Perth city.

EMRC engaged the services of Hydrology and Risk Consulting (HARC) to undertake the hydrology assessment which was peer reviewed by the University of Melbourne to ensure robust and defendable flood estimates that can be used for future flood forecasting.

The Swan and Helena Rivers Flood Study: Hydrology assessment estimated the volume of water in the Swan Avon Catchment from a range of rainfall events and included the potential impact of climate change on design rainfall and flow estimates. This study looked at how long it needs to rain for and how much rain it will take to cause flooding in the catchment, as well as estimating the probable maximum flood that could theoretically occur over the catchment.

Overall, the 'Understanding and Managing Flood Risk in Perth's Eastern Region' Stage One project was very successful and substantively met its objects, by providing a greater understanding of the expected runoff rates from the catchments that will increase the reliability of real-time flood forecasts which will in turn improve the ability of emergency response agencies and the community to take appropriate actions during major events.

The results from Stage One will be used to inform future stages of the project which will include hydraulic modelling and mapping for use by government, planners and emergency services to support land use planning and development decision-making in Perth's Eastern Region, a risk and vulnerability assessment, preparation of a Floodplain Development Strategy and community information tools and engagement.

Disclaimer

The views expressed herein are not necessarily the views of the Commonwealth of Australia, and the Commonwealth does not accept responsibility for any information or advice contained herein. This activity has received funding from programs the Australian Government Attorney-General's Department as part of the Natural Disaster Resilience Program.

AG Department SEMC DRA

Final Report - Stage One - Hydrology

A - Flood Study Hydrology Swan Helena River Area Extent Map (233 KB)

B - Flood Study Hydrology Avon River Catchment Map (281 KB)

C - Flood Study Hydrology Helena River Sub-Catchment Map (383 KB)

D - Flood Study Hydrology HARC Swan Helena Rivers Final Report V3.0 (9 MB)

E - Flood Study Hydrology University of Melbourne Technical Peer Review (113 KB)

Final Report EMRC Understanding Managing Flood Risk Stage One Hydrology NDRP1415-29 WEB

Stages Two and Three - Hydraulics and Risk Assessment

The EMRC was successful in receiving $20,000 funding from the Western Australian State Emergency Management Committee under the All West Australians Reducing Emergencies (AWARE) program to implement the 'Understanding and Managing Flood Risk in Perth: Stages Two and Three' project in 2016/2017. This project is a collaboration between the EMRC, Department of Water, the member councils Town of Bassendean, City of Bayswater, City of Belmont and City of Swan, and neighbouring councils the City of South Perth and Town of Victoria Park.

The project continues the flood study for the mainstream Swan and Helena Rivers and involves the following key components:

  • Preparation of a calibrated hydraulic model utilising the results from Stage One and the Assessment of Swan and Canning River Tidal and Storm Surge Water Levels by URS (2013);
  • Revised floodplain mapping for a range of flood events;
  • Flood Risk and Vulnerability Assessment (informed by the outcomes of Stage Two); and
  • Floodplain Development Strategy.

There are two objectives of this project:

  • Stage 2: To provide updated modelling and mapping of the Swan and Helena Rivers with consideration of the effects of climate change for a full range of design flood events which will improve knowledge of risk to reduce emergencies.
  • Stage 3: To inform flood hazard mitigation strategies and decision-making on proposed land use and development of the floodplain to reduce risk and improve emergency preparedness.

EMRC engaged the services of BMT WBM Pty Ltd to undertake the project. The project will commence in January 2017 with estimated completion in September 2017.

Towards the end of the project there will be a number of opportunities for presentations and discussions in relation to the outcomes of the project. If you are interested in attending these presentations, please contact EMRC on the details provided below.

Office of Emergency Management AWARE

Latest news

  • In July 2016, EMRC was successful in its funding application under the State Emergency Management Committee's All West Australians Reducing Emergencies (AWARE) program for Stages Two and Three of the flood risk project. The Stages Two and Three project has been initiated and the Request For Tender on Tenderlink closed on 18 November 2016.
  • On 1 December 2016 the State Emergency Management Committee (SEMC) changed its name to the Office of Emergency Management (OEM). The OEM retains the same role as the SEMC Secretariat was well as the added Assurance function and reports directly to the Minister for Emergency Services.
  • In late December 2016, the Tender was awarded to BMT WBM Pty Ltd with work commencing in January 2017. Data has been collected, provided and, in some cases, revised for the consultants to begin their model build.
  • In early February 2017, Perth experienced a large rainfall event followed by a second event a few days later that caused flooding for the Avon and Swan Rivers. Department of Water noted this to be below 10% AEP flood levels and of a similar size to the 1974 event (2017 ~ 380 cumecs; 1974 ~ 420 cumecs). As a result of the similarities it was agreed to substitute the 2017 event for the 1974 event to calibrate the hydraulic model as the data is more reliable which will produce a better modelling result. This additional data collection will delay the project slightly.
  • On 10 February 2017, EMRC awarded the Technical Peer Review contract to Water Research Laboratory. Peer review will occur at methodology, calibration and validation of the hydraulic model, to ensure that the model is defensible and capable of producing flood behaviour information suitable to support further floodplain management and planning initiatives.

For further information please contact:

Joanne Woodbridge - Environment and Sustainability Coordinator
Phone: (08) 9424 2243
Email: joanne.woodbridge@emrc.org.au