Three Pass Approach to Coastal Risk Assessment

Assessment of the physical sensitivity and exposure of coasts to hazards including storm surge flooding and erosion is an essential component of any properly comprehensive coastal vulnerability study. With climate change resulting in greater concern over coastal hazards a confusing plethora of coastal sensitivity assessment methods have been developed or proposed over the last few decades. However the essential requirements of physical coastal sensitivity assessment can be reduced to a simple conceptual framework involving three logical ‘passes’ of assessment. A First Pass comprises the identification of shores likely to be physically sensitive to coastal hazards at all. This involves geomorphic and topographic mapping to identify soft (erosion-prone) and low-lying (flood prone) coasts, and can be prepared relatively rapidly for long coasts, providing a useful indicative coastal risk assessment. Such a First Pass assessment is currently being prepared at a national scale for Australia. A Second Pass or ‘regional’ assessment involves identifying regional variations in the energies or processes driving the physical impacts on the potentially sensitive shores identified in the first pass. This identifies those sensitive shores most exposed to physical impacts, using information on wave, wind and storm climates, tidal regimes or vertical land movement to show severity of risks and indicative time frames under different scenarios, and making initial assessment of protection and adaptation options. Where areas have been identified as potentially hazardous with risks likely to occur within a period of say 25 years, then a more detailed Third Pass or ‘site-specific’ assessment would be necessary to identify and evaluate critical local variations in shoreline sensitivity and exposure, as the basis for final design and selection of appropriate responses to the identified hazards.