Storm tides, coastal erosion and inundation
|Title||Storm tides, coastal erosion and inundation|
|Year of Publication||2010|
|Authors||Helman, P, Metusela, C, Thomella, F, Tomlinson, R|
|Institution||National Climate Change Adaptation Research Facility|
|Keywords||Byron Bay, case study, erosion, extreme tides, Gold Coast, inundation, Narrabeen, New South Wales, NSW, planning, Qld, Queensland, regulation, review|
The majority of Australia’s population and major cities are located on the coast. Since the 1950s, many coastal settlements have changed from ‘family’ beach holiday villages to permanent settlements, and in some cases growing urban areas. The Gold Coast is now the sixth largest urban area in Australia, and Noosa has highly priced CBD real estate. Many of the people who have moved to rapidly growing coastal areas have not experienced the physical or economic impacts of major coastal storms, and are unaware of the risks from sea level rise and intense tropical cyclones.
This study reviews the vulnerability of Australian coastal communities to storm tides by analysing historical storm surges and more recent storm events along Australia’s East Coast. Narrabeen, Byron Bay and the Gold Coast are used as case studies to conduct a detailed analysis of the vulnerabilities, impacts and responses to past events in these communities. The report identifies lessons learnt from past events, and looks at current challenges and priorities that should be considered when developing appropriate adaptation responses in Australian coastal communities.
This report focuses on the period of storminess that occurred between the late 1960s and early 1970s, when each of the case study areas was severely impacted. It is shown that since that time there has been a period of relative calm, during which much of the development on the coast has occurred and various adaptation strategies have been implemented. Extreme coastal storms are widely variable over recorded history, but many link to the climate indices, the Southern Oscillation Index (SOI) and more importantly the Inter-decadal Pacific Oscillation (IPO), which explain the decadal time scale of storminess periods. It is noted that there have been no comparable extreme events since 1974 in the case study areas.
The impact of past extremes is exemplified by the 1967 sequence of storms that resulted in houses being lost, complete erosion of beaches and extensive damage to public infrastructure on the Gold Coast. By comparison, the 2009 events had significantly less impact (a one-in-ten year event versus the 1967 one-in-100+ year event), but caused considerable concern due to the level of current development and higher sea levels. The characteristics of past storm erosion and inundation events that made them particularly severe and damaging were the sequence and duration of storms and, in the case of tropical cyclones, their path. It is noted that if Tropical Cyclone Hamish had crossed the coast anywhere from Hervey Bay to the Gold Coast there would likely have been a similar impact to that which occurred in 1967.
At the time of the earlier events, the Gold Coast and Byron Bay case study areas were relatively undeveloped, but with beachfront and low-lying properties at risk. Because of this low-key development, there was an adequate coastal reserve to allow natural coastal process recovery. The communities also tended to comprise long-term residents who had experienced earlier storminess back in the 1950s. With rapid development from the 1970s onwards, the vulnerability of growing coastal urban areas increased rapidly as community resilience decreased due to the loss of ‘corporate’ memory of storm events and high population turnover. This period has been characterised by a ‘calm weather planning’ mentality at all levels of government and the community.
Initially, adaptation responses were set in place at different times, namely:
However, the responses are limited in their effectiveness for future adaptation under climate change. A key barrier to adaptation has been individual attitudes to extreme events, such as the view expressed after the 1974 Gold Coast storms that this was a one-in-100 year event, and would therefore never happen again in a lifetime.
The immediate response to extreme storms was similar at each location. Individuals took action in terms of protecting their property by using concrete blocks, old tyres, car bodies and sand bags. Mobilisation of the army and other higher level responses also occurred. By comparison, the response in 2009 was limited to some sandbagging and beach scraping. However, emergency management systems that had been developed since the 1970s saw evacuations planned for some events.
The recent events in 2009, and the scientific view that a return to a period of storminess and higher sea level is likely, has seen some renewed action taken to address climate change risk, particularly with regard to upgrading of coastal hazard guidelines and policies in each state. Communities are, however, left with the legacy of over three decades of reduced funding, loss of technical expertise in responsible authorities, and ‘calm weather planning and policy’.
Present-day communities in the case study areas have a high level of vulnerability to future extreme events, due to:
As for future development of adaptation strategies, the case studies have demonstrated the following:
The sea level around Australia has risen some 130 mm since 1820, with 70 mm of that rise occurring since 1950. Rising sea levels will result in greater impacts from storm tides – a major natural hazard for coastal communities. Severe storms and cyclones account for onethird of the total damage cost to the Australian community from natural hazards, which was estimated at $40 billion between 1967 and 1999 (calculated in 1999 dollars).
Ensuring resilience to anticipated future climate change impacts is crucial. Early key actions should focus on building both national awareness of climate change and adaptive capacity. Climate change planning and action have tended to be left to environmental divisions within councils. The complexity of cross-cutting climate change risks in the coastal zone requires an effective collaborative inter-jurisdictional reform effort. Australia needs an over-arching national coastal policy that clarifies the roles and responsibilities of all levels of government when addressing the impacts of climate change. Priorities for collaborative action need to be identified as a first step in coordinating a national reform agenda.
Adaptation to climate change as a means of maximising gains and minimising losses has remained relatively unexplored at the location-specific level. Preparing for adaptation to climate change is justified; costs for preparing now are small in comparison with the costs of likely future impacts. Plans should identify where the existing buffer is of sufficient width to accommodate future impacts, where immediate protection or retreat is required, and how actions can be undertaken. The precautionary principle should be applied, as future events may exceed those experienced over the last two centuries.