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NSW Coastline Management Manual

New South Wales Government
September 1990

ISBN 0730575063

Appendix D: Hazard Management Options

Appendix D7 - The Management of Uncertainty

1 INTRODUCTION

To a greater or lesser extent, all planning studies are confronted with uncertainties arising from inferred future conditions. This is particularly true of planning within the coastal zone, with the extent of the sea level rise and other climatic changes postulated to accompany the Greenhouse Effect being one example of future uncertainty which is relevant to coastline hazard management.

In addition to future uncertainties, planning studies for coastline hazard management are also subject to other, more inherent uncertainties in the estimation of the extent of current coastline hazards. These uncertainties arise from the complex and interrelated nature of coastal processes, data deficiencies in coastal process studies, and our less than complete understanding of these processes.

As all planning and management studies must address the problems of uncertainty, a general procedure for dealing with uncertainty is of interest.

2 A STRATEGY FOR PLANNING UNDER UNCERTAINTY

A simple strategy for dealing with uncertainty is as follows:

A robust strategy is one in which planning and management decisions remain viable even if the actual future outcome is more or less extreme than assumed in the original analysis.

3 DEVELOPING STRATEGIES

The stages involved in developing a strategy for planning for uncertainty are discussed below. It should be noted that these stages are relevant both for developing management strategies which take account of the inherent uncertainties associated with the coastal process, and also, for responding to future uncertainties associated with climate change.

3.1 Identifying Ranges of Values

The need to test the outcomes of management options against a range of scenarios is discussed in relation to both existing and future uncertainties involved in coastal planning and management.

The inherent uncertainties associated with the coastal process relate (in this instance) to the accuracy of predictions of the processes resulting from coastal process or hazard definition studies. These studies are largely based on analysis of a relatively short, recent history of events. Of particular concern is the question of how representative the weather patterns were during this period. For example, the late sixties and the seventies appear to have been quite stormy, while the eighties have been relatively quiet. It is quite difficult to place numerical estimates of accuracy on the results of these studies but it would be prudent to test management options against a range of values for the events being considered.

Regarding the uncertainties associated with climate change, these can be assessed in terms of a possible sea level rise over time, the possibility of increased storminess, the possibility of increased rainfall and flooding, the possibility of increased cyclone activity in the north of State, etc.

The range of scenarios which might be selected for assessment of their effects on management options will depend on a number of factors including the physical or economical life of the development, its importance and cost, and the consequences of damage. Given the early stage of research into some of the issues associated with climate change, it is not considered appropriate to nominate a specific range of values which might be applied to a particular circumstance. The Public Works Department, the Department of Planning, other State agencies and the CSIRO will continue to monitor research in the area of climate change and its implications, and will be in a position to provide advice on the most up to date information at a given time. It will be the responsibility of the developers to ensure that they possess the best available information when considering the likely impact that climate change may have on a development proposal.

3.2 Investigating Consequences

Once a range of scenarios relating to the uncertain factors/events has been determined, it is then necessary to interpret the outcome of those events in terms of whether they represent a potential coastal hazard. In terms of future uncertainties associated with climate change, these may result directly from the effects of sea level rise, or may be due to other aspects of climate change.

It should be noted that in terms of sea level rise these are well accepted theories as the extent of resultant coastline recession. However, methods available for predicting other impacts of climate changes are less well understood, and are constantly being refined. Nevertheless, it should be possible to broadly indicate areas of the coast which may be subject to future additional hazards of this order. This may lead to particular sites along the coast being identified as susceptible to specific threats such as erosion, inundation or cyclonic activity, and this may assist in the selection of appropriate coastal management strategies.

The Public Works Department will provide advice on the outcome of various scenarios and also provide comment on the accuracy of previous technical studies. This advice can be provided in the first instance, in general terms, within the context of a hazard definition study. More specific advice can be provided during the coastal management study when the sensitivity of the option is being considered.

3.3 Robust Planning

Given the uncertainty that exists concerning a number of factors relating to planning and development control in the coastal zone, the most appropriate planning response is to ensure that management strategies are flexible and therefore robust enough to withstand future changes not precisely predicted now. This may involve considering a number of approaches in preparing management plans depending upon the likely developments involved, and the nature of the hazards being planned for. For example, it may be necessary to adopt strategies which temporarily permit certain types of development in localities which may be subject to coastal hazard in the future. Similarly, a policy of planned retreat may give the same type of flexibility for future decision making, given the uncertainties concerning future climate change, and in our understanding of workings of the coastal processes.

Another more general method of achieving robust planning is after having decided upon the appropriate management option, to examine the effect of future changes being more or less extreme than originally predicted. This approach is assisted by ensuring that there is flexibility in the design of coastal developments, as the following examples help illustrate:

In view of the uncertainties associated with development in the coastal zone, such flexibility in the design of development should be considered an essential element of robust planning.

4 CONTINGENCY PLANNING

As part of the planning for uncertainty it is necessary to consider that future events may differ significantly from predictions either in relation to future climate change or the uncertainties associated with coastal processes being more or less extreme than were planned for. Contingency plans for such developments should be thought out at the feasibility and design stages of the project. Council may look more favourably at developments that can be protected by cost effective contingency measures.