Climate Change Risk Assessment Project
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1 CLIMATE CHANGE RISK ASSESSMENT PROJECT A methodology enabling local government to assess the vulnerability of foreshore areas to sea level rise April 2010 Caring for the Swan Canning Riverpark CLIMATE CHANGE RISK ASSESSMENT PROJECT Swan River Trust Level 1, 20 Terrace Road East Perth WA 6004 PO Box 6740 East Perth WA 6892 Phone (08) 9278 0900 Fax (08) 9325 7149 Email [email protected] Website www.swanrivertrust.wa.gov.au Swan River Trust after hours contact number 0419 192 845 Front cover: Waves overtopping a seawall along the Kwinana Freeway during a winter storm in 1995 Source: The West Australian newspaper (13 July 1995) ACKNOWLEDGMENTS The Swan River Trust acknowledges the assistance and support provided by Jessica Bayens, Jodie Gardner and the Risk Management Taskforce at the City of Perth. The Trust thanks the Office of Climate Change, Western Australian Local Government Association (WALGA), Department of Water, City of Mandurah and Eastern Metropolitan Regional Council (EMRC) for their feedback and support. The Trust thanks the Department of Water who provided high resolution Light Detection and Ranging (LiDAR) data to enable the creation of the sea level rise maps. The Trust also thanks the Swan River Trust Technical Advisory Panel (TAP) for their feedback and support, and Department of Environment and Conservation’s GIS Applications Section who created the projected sea level rise maps for the project area. CLIMATE CHANGE RISK ASSESSMENT PROJECT TABLE OF CONTENTS EXECUTIVE SUMMARY ......................................................................................................... 1 INTRODUCTION ..................................................................................................................... 2 Project background.................................................................................................................. 2 PROJECT SCOPE .................................................................................................................. 3 Assumptions and limitations .................................................................................................... 3 Project area ............................................................................................................................. 3 Risk assessment ..................................................................................................................... 4 Spatially mapped sea levels .................................................................................................... 4 Predicted future water levels in the project area ..................................................................... 4 METHODOLOGY .................................................................................................................... 7 Step 1 – Determine assets you wish to assess ....................................................................... 8 Step 2 – Determine consequence ........................................................................................... 9 Step 3 – Determine likelihood.................................................................................................11 Step 4 – Determine risk for assets ........................................................................................ 12 RECOMMENDATIONS ......................................................................................................... 13 Infrastructure ......................................................................................................................... 13 Social ..................................................................................................................................... 13 Ecological .............................................................................................................................. 14 REFERENCES ...................................................................................................................... 15 LIST OF FIGURES AND TABLES Figure 1 Dynamics of the Swan River ..................................................................................... 3 Figure 2 Water level categories ............................................................................................... 5 Figure 3 Determining likelihood categories ........................................................................... 12 Table 1 Snapshot of common assets found in the Swan Canning Riverpark .......................... 8 Table 2a Multi-criteria analysis for determining consequence scores for infrastructure ........ 10 Table 2b ................................................................................................................................. 10 Table 3 Consequence categories ...........................................................................................11 Table 4 Risk matrix ................................................................................................................ 12 1 EXECUTIVE SUMMARY Storm surge, high tide and climate change induced sea level rise will enable flooding and damaging waves to penetrate further inland (CSIRO & BoM, 2007). This methodology, based on the Australian/New Zealand Risk Management Standard (AS/NZS 4360:2004), assists local government to identify which foreshore assets in the Swan Canning Riverpark are most at risk from sea level rise. This information is intended to help prioritise and target local government adaptation strategies. In December 2007, the Swan River Trust’s Technical Advisory Panel (TAP) prepared a paper on potential impacts of climate change on the Swan Canning Riverpark. The paper recognised that climate change has the potential to alter the ecological function of the Riverpark and the way people interact with the rivers as a whole. This project builds on the results from that study. Climate change will cause sea level rise and trigger an increase in the frequency and magnitude of extreme events, which include high tides, storm surges (low barometric pressure), wind and wave setup (CSIRO & ACECRC, 2008). This project has incorporated those extreme event factors in water levels, though the sea level rise maps used in this methodology are only an indication of the risks that may result under future climatic conditions. Assessing the risk to foreshore assets from sea level rise will assist in prioritising adaptation strategies. This methodology should be used as a ‘first pass’ to assess the risk of foreshore assets. Those assets at greatest risk will require a more detailed assessment to guide adaptation priorities and actions. It must be noted that even though temporal considerations are incorporated in the risk assessment process, some assets will only be impaired for a short time. Even though the frequency and severity of events are predicted to increase, the inundation for many foreshore assets may only be experienced for a few hours, several times a year. Please note that throughout this report, ‘social’ represents ‘people’ and ‘human usage’. 2 CLIMATE CHANGE RISK ASSESSMENT PROJECT INTRODUCTION Project background Planning, protection and management of the Swan Canning Riverpark is coordinated by the Swan River Trust. The Trust receives expert advice on scientific and management issues from the TAP comprising experts with a diversity of knowledge and expertise. In December 2007, the TAP prepared a paper on the potential impacts of climate change on the Swan Canning Riverpark. This paper recognised that climate change has the potential to alter the ecological function of the Riverpark and the way people interact with the rivers as a whole. Five key strategies were identified to adapt to the adverse impacts of climate change, these were: i assessing foreshore vulnerability; ii improving water quality through oxygenating water, trapping nutrients and ensuring adequate river flow; iii using monitoring and modeling to predict future changes; iv managing biodiversity; and v protecting infrastructure. The Trust is committed to progressing each of these adaptation strategies to increase the resilience of the Swan Canning Riverpark. This project partly fulfills that commitment by providing a methodology for assessing the effect of sea level rise and increased frequency of extreme events on foreshore areas. This methodology will enable local government to identify which foreshore assets adjacent in the Swan Canning Riverpark are most at risk from sea level rise. This information is intended to help prioritise and target local government adaptation strategies. 3 PROJECT SCOPE Assumptions and limitations In developing this project the Trust has assumed that climate change will bring uniform sea level rise in the project area. Therefore, sea level rise was essentially added to the 1990 water levels for the project area. These data include effects from storm surges and tides. This project uses sea level rise projections from the 2001 Third Assessment Report (TAR) by the Intergovernmental Panel on Climate Change (IPCC), which are benchmarked against 1990 water levels. In future years, the predicted sea level rise figures used here will need to be revised as climate change projections are updated. It must be noted that even though temporal considerations are incorporated in the risk assessment process, some assets will only be impaired for a short time. Even though the frequency and severity of events are predicted to increase, the inundation for many foreshore assets may only be experienced for a few hours, several times a year. When