Abstract
The south-east coast of Australia has many low-lying areas at river entrances that are vulnerable to coastal inundation due to high water levels elevated by ocean tides, coastal storms, ocean waves and other drivers. The penetration of elevated entrance water levels into rivers can further intensify river flooding associated with high rainfall events. In this study, historical water level data, which were collected continuously at 17 inshore and 5 offshore permanent tide stations along the East Coast of Australia, are used to study effects of tides and waves on water levels at trained river entrances and also to estimate extreme entrance water levels without major entrance rainfall-related flooding.
Highlights
Water levels at coastal river entrances are potentially influenced by a variety of coastal drivers including astronomic tides, ocean waves, coastal trapped waves, ocean currents, ENSO and sea level rise
The results show that extreme water levels vary along the New South Wales (NSW) coast and generally tend to be slightly higher on the north coast than on the south coast
This trend is seen in both bay/harbour sites and river entrance sites
Summary
Water levels at coastal river entrances are potentially influenced by a variety of coastal drivers including astronomic tides, ocean waves, coastal trapped waves, ocean currents, ENSO and sea level rise. Hanslow et al (1996) concluded that the absence of wave setup at the trained entrance of the Brunswick River was due to the momentum flux of the river flow and its influence on the incoming waves This may not be the case when rising tides propagate with ocean waves in the same direction. Dunn (2001) attempted to further explain the field data of Hanslow et al (1992, 1996) by applying different analytical and numerical models He concluded that two of the main reasons for small and sometimes immeasurable wave setup height in the Brunswick River entrance were wave energy dissipation due to bottom friction and wave energy loss due to wave rolling on the training breakwaters. A number of long-term field datasets on mean water levels collected at coastal entrances of rivers and large bays and harbours along the Australian East Coast of New South Wales (NSW) will be used to investigate the effects of tides and wave setup on mean water levels measured and estimate n-year return extreme water levels at the NSW coastal river entrances
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