Scientific uncertainty in coastal management
As noted above, a key element of the 1992 Australian ESD strategy is dealing cautiously with risk, uncertainty and irreversibility. In the same year, the National Greenhouse Response Strategy was released in an attempt to address issues relating to global wanning and the emission of greenhouse gases. Included in the greenhouse strategy is a recognition of three key issues relating to coastal management:
• the need to understand the science of climate change, in particular the predictions of sea-level rise, its implications and the level of uncertainty
• the need for climate change research, including monitoring of sea-level change
• the need to provide adaptation techniques and strategies for dealing with and assessing coastal vulnerability.
The first of these has been the subject of major international scientific investigations through the Intergovernmental Panel on Climate Change (IPCC), which has produced a number of reports (Houghton et al. 1991, 1992, 1996, 2001). One aspect of these reports is the examination of the effects of climatic change on sea level through global wanning, thermal expansion of the ocean, and an increased contribution of meltwater from glaciers, and also the effects of a rising sea level on coastal environments.
The first of these IPCC studies caused great concern for coastal managers because of the extent of sea-level rise predicted and the potential for coastal flooding and erosion. Sea level was predicted to rise by a best estimate of 0.66 m rise by 2100 (Houghton et al. 1990). The later IPCC reports have provided a significant downward revision of earlier sea-level rise predictions, but more recent calculations have continued to produce similar best-estimate figures, either by more qualitative expert analysis (0.61 m by 2087: Woodworth 1993), or by detailed recalculation (0.46 m by 2100: Wigley & Raper 1993). The 1996 IPCC report (Houghton et al. 1996) further revised the best estimate to around 0.49 m by 2010. The most recent IPCC report (Houghton et al. 2001) has not significantly changed this sea-level rise estimate and quotes the central value figure as a sea-level rise of 0.48 m by 2100 (see Figure 4.9).
Figure 4.9 IPCC predicted sea level rise to 2100
Source: modified from Church et al. 2001
Earlier in this chapter it was noted that a major problem in identifying the current rate of eustatic sea level change from tide gauge data in Australia is the influence of other effects such as human-induced subsidence or geological uplift, which may affect the tide gauge records. Some authors, such as Gomitz (1993), suggest that, after extracting long-term trends and data averaging, it is possible to obtain a true picture of sea level rise. Gomitz presents evidence based on 16 tide gauge data studies from overseas to suggest that the rate of global sea level rise over the last hundred years has been between 0.5 and 3 mm per year, with most estimates being from 1 to 2 mm per year (Gomitz 1993). However, as shown earlier in this book, it is possible to obtain quite different sea-level trend records from long-term tide gauge data sites that are relatively close to each other.
The problem for coastal managers is dealing with the level of uncertainty with the predictions and at the same time needing to have in place a good monitoring system. In Australia the National Tidal Facility (NTF) collects, compiles and analyses all the tidal records. The NTF has also developed a system of highly accurate tide gauges which are linked to satellite altimetry in order to obtain any evidence of vertical movement of the tide gauge site over time.
The issue of scientific uncertainty appears most pronounced for the sea- level issue. Although the predictions for sea-level rise have been reduced over the last 10 years, some states decided to act earlier than others. For example, in South Australia a policy was developed in 1991 on coastal flooding and new coastal development. This policy was based on the earlier (1990) IPCC predictions. Consequently all new development in South Australia has to be protected from the threats of a 0.3 m sea-level rise to the year 2050 and the capability of protecting the development from an additional 0.7 m rise to 2100. The policy incorporates the need to calculate the impact of erosion over this time and to allow for any localised factors such as subsidence. The fact that this policy is based on a 1.0 m sea-level rise to 2100 rather than the more recent central value of 0.48 m is a good example of using a precautionary approach in the face of scientific uncertainty.
Coastal ecosystems are strongly dependent on sea level. For example, some saltmarsh communities are adjusted to conditions within a few centimetres of high tide. Human use of the coast is also closely linked to tide levels. However, sea level is not the only significant change accompanying climate change. Change in storm frequency and wind direction, changes in run-off and watertable levels, and changes in disease vectors will all be significant at the coast. The World Coastal Conference in the Netherlands in 1993 concluded that climate change was a stress which could best be addressed by nations working to integrate their coastal management arrangements. Australian states have begun the task, including assessments of vulnerability to climate change, but to date a national response has not been forthcoming.
In recognition of the problem of coastal vulnerability from the predicted sea-level rise, the IPCC developed a 'Common Methodology for Coastal Vulnerability' assessment (see chapter 1). The intention was to conduct a rapid assessment of the capacity of different countries to cope with the impact of sea- level rise, particular the developing countries which may require international aid to assist them. But as noted by Harvey et al. (1999a), the Common Methodology had mixed results: many countries could not complete the necessary steps, and there was criticism of the methodology itself.
The Australian government funded some preliminary studies that lead to criticisms of the Common Methodology at the World Coast Conference. The Common Methodology was not considered appropriate for Australia because the economics-based assessment technique is inconsistent with the planning approaches used in this country. As a result of these criticisms an alternative methodology was proposed by Kay and Waterman (1993) and was incorporated into the brief for a nationally funded project, the National Coastal Vulnerability Assessment Case Studies Project. This project was carried out in each of the states and territories of Australia during 1994-95 through nine case studies funded by the Commonwealth government at a cost of $500 000 over two years. These studies were conducted at the following sites:
• Batemans Bay (New South Wales)
• Mackay (Queensland)
• City of Clarence (Tasmania)
• Gippsland and Port Philip Bay (Victoria)
• Metropolitan Perth (Western Australia)
• Kakadu and Darwin Harbour (Northern Territory)
• Upper Spencer Gulf (South Australia).
The location of these is shown in figure 4.10. One of the aims of the project was to meet Australia's international commitment under the Climate Change Convention (see table 4.1) to produce vulnerability assessments. The results of the project were taken to the IPCC meeting in Montreal in October 1995. These have also been subsequently published (Waterman 1996), including a CD containing all of the individual state studies.
However, it appears that very few of the states applied this revised Kay and Waterman (1993) methodology, as proposed. Tasmania attempted to use the Common Methodology but considered it to be too general, whereas Western Australia encountered problems in trialling a different methodology called Impact Zone – Connected Area Analysis. The Queensland case study attempted to develop a supplementary methodology to complement the Common Methodology; New South Wales used methods developed within its own Coastal Hazard Policy; and the Northern Territory study attempted to develop methods based on various existing databases (Waterman 1996).
The two states (Victoria and South Australia) that attempted to use the Kay and Waterman methodology both encountered difficulties. The Victorian study 'expressed major doubts over the usefulness of the methodology at anything but a local level' (Waterman 1996, p. 48). The South Australian study initially followed the Kay and Waterman methodology (as required by the project brief) but encountered several problems. These have been detailed in Harvey et al. (1999a) as the lack of predetermined spatial or temporal scales; the fact that the methodology included only the impacts of sea-level rise in Stage 1 and ignored other potential impacts of climate change, and the lack of context to present human-induced hazards on coastal zones. In addition, the methodology gave no guidance for ranking management and response option priorities.
For these reasons, Harvey et al. (1999a) proposed an alternative methodology which they applied to various sites in South Australia, and from this study a GIS-based methodology for vulnerability assessment was developed (Harvey
Figure 4.10 Locations of the National Coastal Vulnerability Assessment case studies
Source: Harvey et al. 1999a
et al. 1999). However, it appears that the Australian government has not progressed with any coastal vulnerability assessment studies or produced policy outcomes from the 1994-95 studies, as noted by McLean (2001).
The concept of ESD is understood to be a fundamental component of coastal management in Australia and has formed the basis for both the national coastal inquiry (RAC 1993) and the Commonwealth Coastal Policy (Commonwealth of Australia 1995). The ESD principles have also been incorporated into a number of state coastal policies, where they exist, and state planning legislation and regulations.
One aspect of the Australian ESD strategy which is linked to global warming is the issue of scientific uncertainty surrounding predictions of sea-level rise. This is a major issue for coastal managers, who need scientific data on which to base decisions for coastal planning, coastal development and coast protection strategies. In the face of such uncertainty, there is a need to take a precautionary approach and at the same time conduct research and monitoring in order to increase the confidence of scientific predictions relating to our future coasts. It is also apparent that while Australia conducted coastal vulnerability studies in the mid 1990s, it has not produced anything significant since.