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.

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 was 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.

Stage Four - Understanding Flood Risk Adaptation Planning

Stage Four Flood Risk Adaption Planning enabled disaster resilience through guiding planning and development and decision-making that incorporated climate change considerations, to assess the vulnerability of public, private property, infrastructure and to facilitate adaptation emergency response planning activities. This project aimed to make information and recommendations on flood risk readily available to participating Local Government for risk managers and planners to make informed risk management and development decisions as well as assist with the adaptation process. Stage Four involved a gap analysis investigation and an adaptation plan for participating Councils.

Understanding Flood Risk Stage Four was built on previous stages and developed a Flood Risk Adaptation Planning documentation for participating local governments, involving internal and external Government stakeholders to understand, quantify and develop flexible adaptation options. The project highlighted the need to raise awareness in the community around the potential for flood to ensure community safety.

The EMRC engaged the services of BMT Group Ltd to undertake the project, which commenced in March 2020 and was completed by the end of the calendar year.

Community Awareness Campaign - 'Flood Aware. Be Prepared'

The Community Awareness campaign ‘Flood Aware. Be Prepared’ aims to provide participating Councils with the tools to communicate the updated flood risk mapping to their affected residents, businesses and general community. All communications materials will include vulnerable institutions and disabled persons’ needs and be inclusive to Culturally and Linguistically Diverse communities. This project aims to seek Commonwealth National Disaster Resilience Program funding of up to 50% to support participating Councils implement this project.

This plan aims to build resilient communities through raising awareness of the flood risks associated with the Swan and Helena rivers in the communities within Perth's Eastern Region. Resilience is built through multiple mechanisms but this starts with raising awareness. To date Local Government Authorities (LGAs) in Perth's Eastern Region have not completed a flood awareness campaign that provides up to date flood risk mapping and preparedness information to their communities. In addition, the community information sessions that have been conducted are not delivering consistent messaging across the Region with respect to flood risks and preparedness. This project aims to build resilience in the community through raising awareness about flood risk in a consistent manner across six LGAs in conjunction with the Department of Fire and Emergency Services (DFES) and the Department of Water and Environmental Regulation (DWER).

Latest news

In January 2021, The EMRC was successful in securing the Commonwealth - State National Disaster Resilience Program (NDRP) grant for the Understanding Flood Risk Community Awareness Project 'Flood Aware. Be Prepared’ The campaign aims to build resilient communities through raising awareness of the flood risks associated with the Swan and Helena Rivers in the communities within Perth's Eastern Region.

In June 2018 the EMRC, in collaboration with consultants BMT, commenced development of the Swan and Helena Rivers Floodplain Development Strategy. The Strategy provides a regional direction to guide the management of existing flood risk and sustainable future development in the floodplain. Multiple Council areas are located within the floodplains of the Swan and Helena Rivers, requiring coordination in the management of the floodplain; particularly changes to topography which have the potential to alter flood behaviour and risk. The Strategy also supports regional coordination for disaster management, and community engagement and awareness.

For further information please contact:

Julia Christensen - Urban Environment Coordinator
Email: Julia.christensen@emrc.org.au