- Title
- Water level trends in NSW coastal lakes by use of exceedance probability analysis
- Creator
- Hart, Roseanne M.; Power, Hannah E.; Hanslow, David J.
- Relation
- Australasian Coasts and Ports 2019 Conference. Proceedings of Australasian Coasts and Ports 2019 Conference (Hobart, Tasmania 10-13 September, 2019) p. 534-540
- Publisher
- Engineers Australia
- Resource Type
- conference paper
- Date
- 2019
- Description
- The scenic coastal lake network along the southeast Australian coastline has observed continued population growth and development in close proximity to the mean water level due to minimal wave and tidal exposure. As the short and long-term projections of sea level rise (SLR) continue to increase as a result of thermal expansion and continued depletion of ice sheets, so to the risk of inundation. Coupled with the evolving hydrodynamics within coastal lakes resulting from entrance training, there is a need to further understand the complexities of water level dynamics to assist in planning for potential inundation hazards. In addition, large-scale external oscillations such as El Nino-Southern Oscillation (ENSO) are known to affect offshore and coastal systems, however the direct effect of these large-scale drivers on small-scale coastal lake systems is yet to be investigated.
This paper investigates the rates of SLR in two coastal lakes in NSW - Lake Macquarie and Lake Illawarra, the latter of which had entrance training completed in 2008. Tide gauge data is used to assess trends in exceedance probability values of low, median and high water levels represented by 95%, 50% and 5% exceedance probability respectively within coastal lakes and ocean conditions at Patonga for proxy. In addition, the relationship between coastal lake water levels and ENSO are investigated. Within Lake Macquarie both median and high water levels have shown significant increases, however, high water levels have shown the greatest increases most noticeable in the entrance channel at Swansea. This indicates increases in water level range and increased exposure to ocean tides and conditions. ENSO, represented by the Southern Oscillation Index (SOI) was shown to be responsible for up to 6% of water level variability within Lake Macquarie, highlighting the need to incorporate large-scale oscillations when assessing potential inundation hazards in these systems.
Lake Illawarra exhibited a response to entrance training through a significant increase in high water levels within the lake. Since entrance training, high water levels have increased at rate of up to 9.3 mm per year which is over three times the global SLR estimate. The minimal association between water level variation within Lake Illawarra and the SOI, together with increased water level ranges due to rapid annual increases in high water levels indicated a dynamic response to entrance training. This dynamic nature highlights the necessity of regular monitoring of SLR within the lake and robust inundation hazard modelling. - Subject
- sea-level rise; coastal risk; oastal lakes; water levels; exceedance probability
- Identifier
- http://hdl.handle.net/1959.13/1460255
- Identifier
- uon:45908
- Identifier
- ISBN:9781925627237
- Language
- eng
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