Sea level rise in Western Australia – has it been adequately planned for?

How will rising sea levels affect WA’s coast?

The recent United Nations Climate Change Conference in Doha, Qatar, has resulted in Australia’s signing to the renewed Kyoto protocol, extended until 2020.

However, it was the 2012 State of Australian Cities report released by the federal Department of Infrastructure and Transport a week ago (4th December 2012) that made waves locally, regarding climate change in Perth. Specifically, that:

  • In 2011, Perth experienced a total of 50 days over 35°C, being the peak of a three-year spike of hot weather which has seen more days over 35°C than any other time in the past 30 years.
  • One of Australia’s three driest capitals, Perth has experienced a reduction in average annual rainfall between 1952 and 2011.
  • Sea level rise around Australia has been equal to and in some cases greater than the global average of approximately three millimetres per year. Since 1993 Perth, along with Darwin, experienced the highest rates of sea level rise of our major coastal cities measuring nine to ten millimetres per year (tidal gauge measurements at Hillarys Western Australia), well above the global average.

Given the recent publicised prediction of a temperature rise of 4-6 degrees by the end of the century (as opposed to the goal of keeping global temperature rise to the generally agreed safe limit of 2 degrees above pre-industrial levels), published in Nature Climate Change and generated by the Global Carbon Project, the decline in rainfall, increasing intensity of extreme storm events and sea levels rise is expected to accelerate faster than previously predicted.

Marked increasing trend in Global Mean Sea Level Rise (Source: CSIRO CMAR, 2012, http://www.cmar.csiro.au/sealevel/ )

The Climate Commission headed by 2007 Australian of the Year Tim Flannery released The Critical Decade: Western Australia climate change impacts report in 2011, which addresses state-specific climate change issues.  A key message from the report is that rising sea levels will exacerbate existing vulnerability to flooding and beach erosion. It is probable that flooding events will lead to damage of cities, towns and the supporting infrastructure in low-lying coastal areas  and will lead to erosion of sandy beaches.

In 2009 the Department of Climate Change predicted that an estimated 18,700 to 28,900 residential buildings in  Western Australia may be at risk of flooding towards the end of this century – with a value of between $4.9 billion  and $7.7 billion, assuming a 1.1 m rise in sea level. The southwest Local Government Areas of Mandurah, Busselton, Rockingham and Bunbury are considered to be at the greatest risk of inundation as sea levels rise, collectively representing over 60% of residential buildings at risk in Western Australia. Mandurah has been one of the fastest growing areas in the last decade and has seen more than 40% increase in development in low lying areas (below 3 m).

Perth_18_150_Map_22

Predicted high sea level rise scenarios relevant to a 2100 time period in Mandurah (Source: OzCoasts (GeoScience Australia, 2012)

The state government has addressed the issue of climate variability through an increased emphasis on water supply planning and the implementation of water sensitive urban design. The same cannot necessarily be said of sea level rise, however.  This is particularly critical given the majority of Australians live near the coast.  While documents such as the State Planning Policy 2.6: State Coastal Planning Policy and the State Government’s Climate Change Adaption Strategy (released in October 2012) highlight the need to consider mitigation and adaptation actions in regards to sea level rise, they do not provide detailed implementation advice.

It will become more critical for individual Local Governments to develop coastal management guidelines and policies to address site specific conditions in order to successfully adapt to sea level rise, more intense storm surge events, coastal erosion, and prevent the potentially huge costs associated with storm and flood damage.  Risk assessments and adaption/resilience planning should be applied to both existing and new coastal infrastructure and development as this becomes more of a critical issue. The issue of how to best approach coastal management of infrastructure and development is yet to be discussed in detail as guidance provided to date by State Government is highly generic in nature.

It is anticipated that the IPCC will release their 5th Assessment Report with latest updates on the scientific, technical and socio-economic aspects of climate change, including sea level rise, around September 2013.

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