Year

2012

Degree Name

Bachelor of Environmental Science (Honours)

ANZSRC / FoR Code

050299 Environmental Science and Management not elsewhere classified

Department

School of Earth & Environmental Science

Advisor(s)

Colin Woodroffe

Abstract

Dunes are the first line of defence against the physical forces of the coastal environment. Informed dune management is an important challenge for coastal managers, particularly with the predicted onset of rising sea levels. The measurement of long term trends and change in coastal systems can provide valuable information for informed and pre-emptive management of the world’s coastlines. Methods commonly used for change detection involve retrospective measurement of the shoreline or high water mark using aerial photography. For more dynamic coasts however, longer-term trends in these features may be obscured by short-term fluctuations. In this study, three different methods for quantifying dune change using aerial photographs, photogrammetric data, and LiDAR data, are used. The methods include 1) dune volume calculation, 2) 2 m AHD contour movement analysis, and 3) vegetation line tracking. The techniques are applied to Woonona/Bellambi and Thirroul beaches located within the Wollongong Local Government Area. It is shown that the use of different indicators results in significantly different trend estimates and that caution must be exercised in the selection of appropriate indicators. For highly dynamic dunes, such as those at Woonona/Bellambi and Thirroul, indicators such as the 2 m AHD contour location and the dune volume provided a better indication of underlying trends in coastal erosion than the vegetation line. Woonona/Bellambi Beach was found to have accreted by 147,770.5 (±60,000) m3 since 1961, while Thirroul appears to have fluctuated around its 1961 volume. A large storm cut of 76,719.8 m3 was calculated for the whole of Thirroul Beach system after the 1974 storm events. An analysis of the methods highlights limitations, including a low temporal resolution, that should be addressed in future monitoring of dune behavior. The detailed analysis of dune change allows for more site specific management of the dune systems by Wollongong Council. This report provides an improved understanding of how the different systems have changed and can projected into future pre-emptive management.

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