Year

2020

Degree Name

Bachelor of Science (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Amy Dougherty

Abstract

Beaches that receive more sediment than can be removed by storm erosion will not recede as the sea level rises from future global warming. This research examines the interplay between sediment supply and the frequency and magnitude of storms within the historical record at Bengello Beach, Moruya, New South Wales. During a series of large storms in May-June 1974, Bengello Beach lost approximately 50% of its sand volume and evidence of this erosion is preserved by a 40+ year beach profile campaign that recorded subsequent sediment accumulation. This historical beach-profile history can be contextualised with the barrier’s stratigraphic record captured by the progradation in the past 7,000 years allowing inferences to be made of larger scale changes. The three main objectives of this study are: 1) Examine the links between river flooding, coastal storms and beach changes during large storm events 2) Determine if the Moruya River is delivering sediment to the beach and 3) Analyse the frequency and magnitude of river flooding, coastal storms and beach changes from the historical record and beyond. This methodological approach will focus on analysing pre-existing datasets including: a 40+ year beach profile dataset, a 34- and 46-year wave buoy dataset from Batemans Bay and Port Kembla, peak discharge from the Moruya River and estuarine hydrodynamic models. While it is common to observe intense rain and river flooding in association with coastal storms, preliminary results from the analyses indicate that no strong correlation exist between the occurrence of high river discharge and high significant wave height. However, estuarine hydrodynamic models indicate that sediment reaching the river mouth during floods appears to coincide with increased coastal accretion. Furthermore, within the wave rider buoy records, differences in the quantity, peak significant wave height, duration and period of moderate to extreme storms were noticed on the seasonal scale in addition to an increasing occurrence of severe events (Hsig 5-6m) which have appeared throughout the record since 2000. In response to the observed trends in storm wave 3 characteristics, the effect of various climatic influences can be inferred. The implications of this study will highlight the sensitivity of coastal barriers to storm erosion and changing storm frequency relationships seen throughout the early 21st century.

FoR codes (2008)

040604 Natural Hazards

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.