Understanding and Managing Flood Risk in Perth. Design and implementation of a climate risk management project

Transcription

1 Understanding and Managing Flood Risk in Perth Design and implementation of a climate risk management project

2 Overview Climate change risk is uncertain! Flood modelling for this catchment is complicated!!

3 Perth s Eastern Region

4 Project initiation identifying the need Natural Disaster Resilience Program 2014/15 funding released by State Emergency Management Committee in August 2014 Department of Water confirmed that flood data and mapping was out of date and required review to meet updated industry standard methodologies for the full range of expected flood events

5 Strategic context Mitigation strategies for flood are identified in the State Emergency Management Plan for Flood (Westplan Flood, 2010) EMRC s Regional Climate Change Adaptation Action Plan Swan and Helena Rivers Management Framework Aligns with EMRC Year Strategic Plan

6 History of flooding in Perth Images, graphs and data throughout the presentation kindly provided by the Department of Water and Environmental Regulation

7 Historical flood events

8 Current planning ARI = Average Recurrence Interval (years) AEP = Annual Exceedance Probability (%) 100 year ARI = 1% AEP i.e. there is a 1 in 100 chance every year of this event occurring Floodplain planning is based on the current 100 year ARI

9 No. of Flood Affected Buildings City of Fremantle Town of East Fremantle Town of Mosman Park City of Melville Shire of Peppermint Town of Claremont City of Nedlands City of Subiaco City of Perth City of South Perth City of Canning Town of Victoria Park City of Vincent City of Bayswater City of Belmont Town of Bassendean City of Swan Quantifying risks from flood modelling 1 in 100 AEP event - number of flood affected buildings for each local government area 250 Residential Commercial Major Sheds Public Facility

10 No. of Flood Affected Buildings What about possible climate change impacts? Residential Commercial Major Sheds Public Facility in 10 1 in 25 1 in 50 1 in in m 1 in m 1 in SLR Annual Exceedance Probability (AEP) 1 in 10 1 in 25 1 in 50 1 in in in in m 1.0m SLR Residential , Commercial Major Sheds Public Facility TOTAL ,094 2,

11 Summary of drivers Need for updated information New industry standard methodologies Pressure for floodplain development Understanding of full range of expected events needed for: planning emergency response planning infrastructure design risk management strategies

12 Balancing activities and risk Floodplain management is a balance of the: social, economic and ecological costs and benefits of carrying out activities on the floodplain Against the: risk, hazard and adverse consequences caused by flooding North Street, Bassendean, in July 1983 (above) and January 2017

13 Objectives of floodplain management Floodplain management measures have economic, social and environmental outcomes Planning land uses to minimise flood risk and damage costs Non-structural measures are promoted rather than structural measures Floodplain mitigation measures minimise damage and are acceptable to the local community Flood warning systems and emergency management arrangements cope with the impact of flooding All levels of government and the local community accept their responsibilities in floodplain management

14 Aims of the flood risk project To update the floodplain mapping that informs land use planning, development decision making and emergency response activities To prepare mitigation options to reduce the risk/impact of flooding to the community

15 Stages of a flood study Three main technical components: Hydrology how much water could there be? Hydraulics where will the water go? Damage assessment what damage will the water do? Outputs from the overall flood study will include: Statistical models and data files Mapping Risk and vulnerability information Strategies, plans and policies to manage flood risk

16 Work completed prior to EMRC project Assessment of Swan River tidal and storm surge water levels was commissioned by the Department of Water and completed in 2014 Revised mapping which updated the 1985 data with new tidal and storm surge levels

17 Staged project to access available funding Stage One - Hydrology Stage Two Hydraulics Stage Three Risk Stage Four Community Great Northern Highway bridge over Swan River, January 2017 February 2017

18 Stage One - Hydrology Natural Disaster Resilience Program funding under National Partnership Agreement administered by State Emergency Management Committee Project partners included: Department of Water, City of Bayswater, City of Belmont and City of Swan Catchment hydrology assessment completed by Hydrology and Risk Consulting (HARC) in 2016 New design rainfall information

19 How do you manage uncertainty? Sensitivity analyses to changes in the catchment modelling parameters to: Increases in sea level Increases in rainfall intensity Decreases in rainfall intensity Decreases in runoff due to drier conditions Increases in runoff due to vegetation change/bushfire frequency Sensitivity of flood levels to a range of possible events

20 What did we learn? The Swan Avon River extended catchment is HUGE ~ 124,000 km 2 To reach the Probable Maximum Flood event, it would have to rain for a really long time, everywhere Flood modelling for this catchment is complicated!

21 Stages Two and Three Hydraulics, Mapping and Risk Assessment All West Australians Reducing Emergencies (AWARE) funding through Office of Emergency Management Expanded project partners to include: All Stage One partners, Department of Water, City of Bayswater, City of Belmont and City of Swan, plus Town of Bassendean, City of South Perth and Town of Victoria Park Consultants BMT WBM Pty Ltd successful tenderer Model developed, calibrated and peer reviewed (Stage Two) Includes 2017 flood event which replaced 1974 calibration event Design runs underway with final hydraulics report due in late September 2017

22 Hard at work

23 Stages Two and Three Hydraulics, Mapping and Risk Assessment Outputs from the hydraulic modelling will inform revised floodplain mapping (Stage Two); Flood Risk and Vulnerability Assessments (which will include LGA consultation); and Floodplain Development Strategy (Stage Three) Presentations to key stakeholders including visualisations of hazard mapping Outputs provided to emergency agencies, local and state government

24 More things we ve learned Historical data may not be as good as you expected Climate change impacts are uncertain Extreme weather events are unpredictable Delays happen Flood modelling for this catchment is complicated!

25 Stage Four - Flood Intelligence and Adaptation Planning Natural Disaster Resilience Program under National Partnership Agreement administered by Office of Emergency Management Flood intelligence website development Risk adaptation planning for councils Community engagement delayed until risks fully understood and planned for within local government

26 Next steps Current project will progress with completion expected around February 2018 Presentations of outputs to key stakeholders and agencies Stage Four to go ahead in 2018 Stage Five is the community engagement aspect and will be subject to future funding Swan River at Great Northern Highway, January 2017 February 2017

27 For more information Contact Joanne Woodbridge on or Thank you to all project partners and funding bodies including the Australian Government, Office of Emergency Management, Department of Water and Environmental Regulation, Town of Bassendean, City of Bayswater, City of Belmont, City of Swan, City of South Perth and Town of Victoria Park