Year

2016

Degree Name

BSci Hons

ANZSRC / FoR Code

040604 Natural Hazards

Department

School of Earth & Environmental Science

Advisor(s)

Colin Woodroffe

Abstract

Rocky coasts account for approximately 40% of the Australian coast, with some of the best examples of shore platforms found along the south-eastern coastline of NSW. The processes by which these have formed have been debated for centuries, with opposing views existing on morphology and whether they are contemporary or inherited landforms. Researchers have long considered wave erosion as the major determinant, however, subaerial weathering processes have also been proposed. Australian residents and tourists congregate to the coast for a variety of recreational activities, and increasingly it is being recognised that there are significant levels of risk involved with these rocky coast landforms. Royal Lifesaving Australia reports that 126 people have drowned in rocky coast settings in the past seven years, with the large majority of drownings being rock fishermen. A stretch of coastline in the Central Coast region has recorded 16 incidences of drowning within 8 years, suggesting that some coastlines pose higher levels of risk than others and that rocky coasts clearly present a challenge to coastal managers in terms of safety and classifying risk. Research of beach systems allowed Surf Lifesaving Australia to successfully implement a Safety and Management Plan for Australia (ABSAMP), which relies on a thorough understanding of beach morphodynamics. It has recently been proposed that a similar approach could be applied to rocky coasts, as the interactions between platforms of variable morphology and wave energy incur different levels of risk. This study focuses on the various shore platform morphologies in central-southern New South Wales and how platform morphology influences risk. Utilising airborne LiDAR, characteristics of elevation, width and slope for shore platforms are analysed and used as factors of risk. Analysis of morphology gave an indication of formative processes, with rock properties, particularly rock structure being concluded as a major influence, as this factor will determine the resistance properties of platforms to wave action. Elevation data was combined with wave action and tidal data and it was found that the level of risk on a shore platform increases with tidal inundation and wave height, and inundation is determined by elevation. Platform width and slope influence the amount of wave energy impacting upon a platform, with a narrow sub-horizontal platform being considered highly reflective in nature, whereas a wide sloping platform is considered dissipative. Analysis of platforms with high drowning occurrences, and seemingly higher risk showed morphology that is both dissipative and reflective of wave energy, suggesting an intermediate state of energy transfer which may present hazards that neither solely dissipative nor reflective platform morphologies exhibit. This study provides a preliminary basis of classifying risk for various shore platform morphologies. Platform morphology analysed varies significantly, indicating there are several aspects of risk to be considered. This risk analysis provides potential for coastal managers to identify hazards for rock coasts. In the classification hazards are defined by three key observable and measureable parameters; elevation of a platform, tidal height and wave action. This study has demonstrated the potential of airborne LiDAR to analyse morphology and risk involved with rock coasts. Future studies might benefit addressing the influence that slope and width have on wave energy interaction with a platform. These parameters, along with acquisition of offshore bathymetry data combined with the classification used in this study, will help further to refine a risk index.

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